Merge 8aebac8293 ("Merge tag 'rust-v6.1-rc1' of https://github.com/Rust-for-Linux/linux") into android-mainline

Steps on the way to 6.1-rc1

Resolves merge conficts in:
	scripts/Makefile.modfinal

Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I3b66e95488224202d13b481c686d55e9e3048cbb

.gitignore

@@ -37,6 +37,8 @@
 *.o
 *.o.*
 *.patch
+*.rmeta
+*.rsi
 *.s
 *.so
 *.so.dbg
@@ -97,6 +99,7 @@ modules.order
 !.gitattributes
 !.gitignore
 !.mailmap
+!.rustfmt.toml
 
 #
 # Generated include files
@@ -162,3 +165,6 @@ x509.genkey
 
 # Documentation toolchain
 sphinx_*/
+
+# Rust analyzer configuration
+/rust-project.json

.rustfmt.toml

@@ -0,0 +1,12 @@
+edition = "2021"
+newline_style = "Unix"
+
+# Unstable options that help catching some mistakes in formatting and that we may want to enable
+# when they become stable.
+#
+# They are kept here since they are useful to run from time to time.
+#format_code_in_doc_comments = true
+#reorder_impl_items = true
+#comment_width = 100
+#wrap_comments = true
+#normalize_comments = true

Documentation/core-api/printk-formats.rst

@@ -625,6 +625,16 @@ Examples::
 	%p4cc	Y10  little-endian (0x20303159)
 	%p4cc	NV12 big-endian (0xb231564e)
 
+Rust
+----
+
+::
+
+	%pA
+
+Only intended to be used from Rust code to format ``core::fmt::Arguments``.
+Do *not* use it from C.
+
 Thanks
 ======
 

Documentation/doc-guide/kernel-doc.rst

@@ -14,6 +14,9 @@ when it is embedded in source files.
    reasons. The kernel source contains tens of thousands of kernel-doc
    comments. Please stick to the style described here.
 
+.. note:: kernel-doc does not cover Rust code: please see
+   Documentation/rust/general-information.rst instead.
+
 The kernel-doc structure is extracted from the comments, and proper
 `Sphinx C Domain`_ function and type descriptions with anchors are
 generated from them. The descriptions are filtered for special kernel-doc

Documentation/index.rst

@@ -58,6 +58,7 @@ Various other manuals with useful information for all kernel developers.
    trace/index
    fault-injection/index
    livepatch/index
+   rust/index
 
 
 User-oriented documentation

Documentation/kbuild/kbuild.rst

@@ -48,6 +48,10 @@ KCFLAGS
 -------
 Additional options to the C compiler (for built-in and modules).
 
+KRUSTFLAGS
+----------
+Additional options to the Rust compiler (for built-in and modules).
+
 CFLAGS_KERNEL
 -------------
 Additional options for $(CC) when used to compile
@@ -57,6 +61,15 @@ CFLAGS_MODULE
 -------------
 Additional module specific options to use for $(CC).
 
+RUSTFLAGS_KERNEL
+----------------
+Additional options for $(RUSTC) when used to compile
+code that is compiled as built-in.
+
+RUSTFLAGS_MODULE
+----------------
+Additional module specific options to use for $(RUSTC).
+
 LDFLAGS_MODULE
 --------------
 Additional options used for $(LD) when linking modules.
@@ -69,6 +82,10 @@ HOSTCXXFLAGS
 ------------
 Additional flags to be passed to $(HOSTCXX) when building host programs.
 
+HOSTRUSTFLAGS
+-------------
+Additional flags to be passed to $(HOSTRUSTC) when building host programs.
+
 HOSTLDFLAGS
 -----------
 Additional flags to be passed when linking host programs.

Documentation/kbuild/makefiles.rst

@@ -29,8 +29,9 @@ This document describes the Linux kernel Makefiles.
 	   --- 4.1 Simple Host Program
 	   --- 4.2 Composite Host Programs
 	   --- 4.3 Using C++ for host programs
-	   --- 4.4 Controlling compiler options for host programs
-	   --- 4.5 When host programs are actually built
+	   --- 4.4 Using Rust for host programs
+	   --- 4.5 Controlling compiler options for host programs
+	   --- 4.6 When host programs are actually built
 
 	=== 5 Userspace Program support
 	   --- 5.1 Simple Userspace Program
@@ -835,7 +836,24 @@ Both possibilities are described in the following.
 		qconf-cxxobjs := qconf.o
 		qconf-objs    := check.o
 
-4.4 Controlling compiler options for host programs
+4.4 Using Rust for host programs
+--------------------------------
+
+	Kbuild offers support for host programs written in Rust. However,
+	since a Rust toolchain is not mandatory for kernel compilation,
+	it may only be used in scenarios where Rust is required to be
+	available (e.g. when  ``CONFIG_RUST`` is enabled).
+
+	Example::
+
+		hostprogs     := target
+		target-rust   := y
+
+	Kbuild will compile ``target`` using ``target.rs`` as the crate root,
+	located in the same directory as the ``Makefile``. The crate may
+	consist of several source files (see ``samples/rust/hostprogs``).
+
+4.5 Controlling compiler options for host programs
 --------------------------------------------------
 
 	When compiling host programs, it is possible to set specific flags.
@@ -867,7 +885,7 @@ Both possibilities are described in the following.
 	When linking qconf, it will be passed the extra option
 	"-L$(QTDIR)/lib".
 
-4.5 When host programs are actually built
+4.6 When host programs are actually built
 -----------------------------------------
 
 	Kbuild will only build host-programs when they are referenced
@@ -1181,6 +1199,17 @@ When kbuild executes, the following steps are followed (roughly):
 	The first example utilises the trick that a config option expands
 	to 'y' when selected.
 
+    KBUILD_RUSTFLAGS
+	$(RUSTC) compiler flags
+
+	Default value - see top level Makefile
+	Append or modify as required per architecture.
+
+	Often, the KBUILD_RUSTFLAGS variable depends on the configuration.
+
+	Note that target specification file generation (for ``--target``)
+	is handled in ``scripts/generate_rust_target.rs``.
+
     KBUILD_AFLAGS_KERNEL
 	Assembler options specific for built-in
 
@@ -1208,6 +1237,19 @@ When kbuild executes, the following steps are followed (roughly):
 	are used for $(CC).
 	From commandline CFLAGS_MODULE shall be used (see kbuild.rst).
 
+    KBUILD_RUSTFLAGS_KERNEL
+	$(RUSTC) options specific for built-in
+
+	$(KBUILD_RUSTFLAGS_KERNEL) contains extra Rust compiler flags used to
+	compile resident kernel code.
+
+    KBUILD_RUSTFLAGS_MODULE
+	Options for $(RUSTC) when building modules
+
+	$(KBUILD_RUSTFLAGS_MODULE) is used to add arch-specific options that
+	are used for $(RUSTC).
+	From commandline RUSTFLAGS_MODULE shall be used (see kbuild.rst).
+
     KBUILD_LDFLAGS_MODULE
 	Options for $(LD) when linking modules
 

Documentation/process/changes.rst

@@ -31,6 +31,8 @@ you probably needn't concern yourself with pcmciautils.
 ====================== ===============  ========================================
 GNU C                  5.1              gcc --version
 Clang/LLVM (optional)  11.0.0           clang --version
+Rust (optional)        1.62.0           rustc --version
+bindgen (optional)     0.56.0           bindgen --version
 GNU make               3.81             make --version
 bash                   4.2              bash --version
 binutils               2.23             ld -v
@@ -80,6 +82,29 @@ kernels. Older releases aren't guaranteed to work, and we may drop workarounds
 from the kernel that were used to support older versions. Please see additional
 docs on :ref:`Building Linux with Clang/LLVM <kbuild_llvm>`.
 
+Rust (optional)
+---------------
+
+A particular version of the Rust toolchain is required. Newer versions may or
+may not work because the kernel depends on some unstable Rust features, for
+the moment.
+
+Each Rust toolchain comes with several "components", some of which are required
+(like ``rustc``) and some that are optional. The ``rust-src`` component (which
+is optional) needs to be installed to build the kernel. Other components are
+useful for developing.
+
+Please see Documentation/rust/quick-start.rst for instructions on how to
+satisfy the build requirements of Rust support. In particular, the ``Makefile``
+target ``rustavailable`` is useful to check why the Rust toolchain may not
+be detected.
+
+bindgen (optional)
+------------------
+
+``bindgen`` is used to generate the Rust bindings to the C side of the kernel.
+It depends on ``libclang``.
+
 Make
 ----
 
@@ -348,6 +373,12 @@ Sphinx
 Please see :ref:`sphinx_install` in :ref:`Documentation/doc-guide/sphinx.rst <sphinxdoc>`
 for details about Sphinx requirements.
 
+rustdoc
+-------
+
+``rustdoc`` is used to generate the documentation for Rust code. Please see
+Documentation/rust/general-information.rst for more information.
+
 Getting updated software
 ========================
 
@@ -364,6 +395,16 @@ Clang/LLVM
 
 - :ref:`Getting LLVM <getting_llvm>`.
 
+Rust
+----
+
+- Documentation/rust/quick-start.rst.
+
+bindgen
+-------
+
+- Documentation/rust/quick-start.rst.
+
 Make
 ----
 

Documentation/rust/arch-support.rst

@@ -0,0 +1,19 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Arch Support
+============
+
+Currently, the Rust compiler (``rustc``) uses LLVM for code generation,
+which limits the supported architectures that can be targeted. In addition,
+support for building the kernel with LLVM/Clang varies (please see
+Documentation/kbuild/llvm.rst). This support is needed for ``bindgen``
+which uses ``libclang``.
+
+Below is a general summary of architectures that currently work. Level of
+support corresponds to ``S`` values in the ``MAINTAINERS`` file.
+
+============  ================  ==============================================
+Architecture  Level of support  Constraints
+============  ================  ==============================================
+``x86``       Maintained        ``x86_64`` only.
+============  ================  ==============================================

Documentation/rust/coding-guidelines.rst

@@ -0,0 +1,216 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Coding Guidelines
+=================
+
+This document describes how to write Rust code in the kernel.
+
+
+Style & formatting
+------------------
+
+The code should be formatted using ``rustfmt``. In this way, a person
+contributing from time to time to the kernel does not need to learn and
+remember one more style guide. More importantly, reviewers and maintainers
+do not need to spend time pointing out style issues anymore, and thus
+less patch roundtrips may be needed to land a change.
+
+.. note:: Conventions on comments and documentation are not checked by
+  ``rustfmt``. Thus those are still needed to be taken care of.
+
+The default settings of ``rustfmt`` are used. This means the idiomatic Rust
+style is followed. For instance, 4 spaces are used for indentation rather
+than tabs.
+
+It is convenient to instruct editors/IDEs to format while typing,
+when saving or at commit time. However, if for some reason reformatting
+the entire kernel Rust sources is needed at some point, the following can be
+run::
+
+	make LLVM=1 rustfmt
+
+It is also possible to check if everything is formatted (printing a diff
+otherwise), for instance for a CI, with::
+
+	make LLVM=1 rustfmtcheck
+
+Like ``clang-format`` for the rest of the kernel, ``rustfmt`` works on
+individual files, and does not require a kernel configuration. Sometimes it may
+even work with broken code.
+
+
+Comments
+--------
+
+"Normal" comments (i.e. ``//``, rather than code documentation which starts
+with ``///`` or ``//!``) are written in Markdown the same way as documentation
+comments are, even though they will not be rendered. This improves consistency,
+simplifies the rules and allows to move content between the two kinds of
+comments more easily. For instance:
+
+.. code-block:: rust
+
+	// `object` is ready to be handled now.
+	f(object);
+
+Furthermore, just like documentation, comments are capitalized at the beginning
+of a sentence and ended with a period (even if it is a single sentence). This
+includes ``// SAFETY:``, ``// TODO:`` and other "tagged" comments, e.g.:
+
+.. code-block:: rust
+
+	// FIXME: The error should be handled properly.
+
+Comments should not be used for documentation purposes: comments are intended
+for implementation details, not users. This distinction is useful even if the
+reader of the source file is both an implementor and a user of an API. In fact,
+sometimes it is useful to use both comments and documentation at the same time.
+For instance, for a ``TODO`` list or to comment on the documentation itself.
+For the latter case, comments can be inserted in the middle; that is, closer to
+the line of documentation to be commented. For any other case, comments are
+written after the documentation, e.g.:
+
+.. code-block:: rust
+
+	/// Returns a new [`Foo`].
+	///
+	/// # Examples
+	///
+	// TODO: Find a better example.
+	/// ```
+	/// let foo = f(42);
+	/// ```
+	// FIXME: Use fallible approach.
+	pub fn f(x: i32) -> Foo {
+	    // ...
+	}
+
+One special kind of comments are the ``// SAFETY:`` comments. These must appear
+before every ``unsafe`` block, and they explain why the code inside the block is
+correct/sound, i.e. why it cannot trigger undefined behavior in any case, e.g.:
+
+.. code-block:: rust
+
+	// SAFETY: `p` is valid by the safety requirements.
+	unsafe { *p = 0; }
+
+``// SAFETY:`` comments are not to be confused with the ``# Safety`` sections
+in code documentation. ``# Safety`` sections specify the contract that callers
+(for functions) or implementors (for traits) need to abide by. ``// SAFETY:``
+comments show why a call (for functions) or implementation (for traits) actually
+respects the preconditions stated in a ``# Safety`` section or the language
+reference.
+
+
+Code documentation
+------------------
+
+Rust kernel code is not documented like C kernel code (i.e. via kernel-doc).
+Instead, the usual system for documenting Rust code is used: the ``rustdoc``
+tool, which uses Markdown (a lightweight markup language).
+
+To learn Markdown, there are many guides available out there. For instance,
+the one at:
+
+	https://commonmark.org/help/
+
+This is how a well-documented Rust function may look like:
+
+.. code-block:: rust
+
+	/// Returns the contained [`Some`] value, consuming the `self` value,
+	/// without checking that the value is not [`None`].
+	///
+	/// # Safety
+	///
+	/// Calling this method on [`None`] is *[undefined behavior]*.
+	///
+	/// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+	///
+	/// # Examples
+	///
+	/// ```
+	/// let x = Some("air");
+	/// assert_eq!(unsafe { x.unwrap_unchecked() }, "air");
+	/// ```
+	pub unsafe fn unwrap_unchecked(self) -> T {
+	    match self {
+	        Some(val) => val,
+
+	        // SAFETY: The safety contract must be upheld by the caller.
+	        None => unsafe { hint::unreachable_unchecked() },
+	    }
+	}
+
+This example showcases a few ``rustdoc`` features and some conventions followed
+in the kernel:
+
+  - The first paragraph must be a single sentence briefly describing what
+    the documented item does. Further explanations must go in extra paragraphs.
+
+  - Unsafe functions must document their safety preconditions under
+    a ``# Safety`` section.
+
+  - While not shown here, if a function may panic, the conditions under which
+    that happens must be described under a ``# Panics`` section.
+
+    Please note that panicking should be very rare and used only with a good
+    reason. In almost all cases, a fallible approach should be used, typically
+    returning a ``Result``.
+
+  - If providing examples of usage would help readers, they must be written in
+    a section called ``# Examples``.
+
+  - Rust items (functions, types, constants...) must be linked appropriately
+    (``rustdoc`` will create a link automatically).
+
+  - Any ``unsafe`` block must be preceded by a ``// SAFETY:`` comment
+    describing why the code inside is sound.
+
+    While sometimes the reason might look trivial and therefore unneeded,
+    writing these comments is not just a good way of documenting what has been
+    taken into account, but most importantly, it provides a way to know that
+    there are no *extra* implicit constraints.
+
+To learn more about how to write documentation for Rust and extra features,
+please take a look at the ``rustdoc`` book at:
+
+	https://doc.rust-lang.org/rustdoc/how-to-write-documentation.html
+
+
+Naming
+------
+
+Rust kernel code follows the usual Rust naming conventions:
+
+	https://rust-lang.github.io/api-guidelines/naming.html
+
+When existing C concepts (e.g. macros, functions, objects...) are wrapped into
+a Rust abstraction, a name as close as reasonably possible to the C side should
+be used in order to avoid confusion and to improve readability when switching
+back and forth between the C and Rust sides. For instance, macros such as
+``pr_info`` from C are named the same in the Rust side.
+
+Having said that, casing should be adjusted to follow the Rust naming
+conventions, and namespacing introduced by modules and types should not be
+repeated in the item names. For instance, when wrapping constants like:
+
+.. code-block:: c
+
+	#define GPIO_LINE_DIRECTION_IN	0
+	#define GPIO_LINE_DIRECTION_OUT	1
+
+The equivalent in Rust may look like (ignoring documentation):
+
+.. code-block:: rust
+
+	pub mod gpio {
+	    pub enum LineDirection {
+	        In = bindings::GPIO_LINE_DIRECTION_IN as _,
+	        Out = bindings::GPIO_LINE_DIRECTION_OUT as _,
+	    }
+	}
+
+That is, the equivalent of ``GPIO_LINE_DIRECTION_IN`` would be referred to as
+``gpio::LineDirection::In``. In particular, it should not be named
+``gpio::gpio_line_direction::GPIO_LINE_DIRECTION_IN``.

Documentation/rust/general-information.rst

@@ -0,0 +1,79 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+General Information
+===================
+
+This document contains useful information to know when working with
+the Rust support in the kernel.
+
+
+Code documentation
+------------------
+
+Rust kernel code is documented using ``rustdoc``, its built-in documentation
+generator.
+
+The generated HTML docs include integrated search, linked items (e.g. types,
+functions, constants), source code, etc. They may be read at (TODO: link when
+in mainline and generated alongside the rest of the documentation):
+
+	http://kernel.org/
+
+The docs can also be easily generated and read locally. This is quite fast
+(same order as compiling the code itself) and no special tools or environment
+are needed. This has the added advantage that they will be tailored to
+the particular kernel configuration used. To generate them, use the ``rustdoc``
+target with the same invocation used for compilation, e.g.::
+
+	make LLVM=1 rustdoc
+
+To read the docs locally in your web browser, run e.g.::
+
+	xdg-open rust/doc/kernel/index.html
+
+To learn about how to write the documentation, please see coding-guidelines.rst.
+
+
+Extra lints
+-----------
+
+While ``rustc`` is a very helpful compiler, some extra lints and analyses are
+available via ``clippy``, a Rust linter. To enable it, pass ``CLIPPY=1`` to
+the same invocation used for compilation, e.g.::
+
+	make LLVM=1 CLIPPY=1
+
+Please note that Clippy may change code generation, thus it should not be
+enabled while building a production kernel.
+
+
+Abstractions vs. bindings
+-------------------------
+
+Abstractions are Rust code wrapping kernel functionality from the C side.
+
+In order to use functions and types from the C side, bindings are created.
+Bindings are the declarations for Rust of those functions and types from
+the C side.
+
+For instance, one may write a ``Mutex`` abstraction in Rust which wraps
+a ``struct mutex`` from the C side and calls its functions through the bindings.
+
+Abstractions are not available for all the kernel internal APIs and concepts,
+but it is intended that coverage is expanded as time goes on. "Leaf" modules
+(e.g. drivers) should not use the C bindings directly. Instead, subsystems
+should provide as-safe-as-possible abstractions as needed.
+
+
+Conditional compilation
+-----------------------
+
+Rust code has access to conditional compilation based on the kernel
+configuration:
+
+.. code-block:: rust
+
+	#[cfg(CONFIG_X)]       // Enabled               (`y` or `m`)
+	#[cfg(CONFIG_X="y")]   // Enabled as a built-in (`y`)
+	#[cfg(CONFIG_X="m")]   // Enabled as a module   (`m`)
+	#[cfg(not(CONFIG_X))]  // Disabled

Documentation/rust/index.rst

@@ -0,0 +1,22 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Rust
+====
+
+Documentation related to Rust within the kernel. To start using Rust
+in the kernel, please read the quick-start.rst guide.
+
+.. toctree::
+    :maxdepth: 1
+
+    quick-start
+    general-information
+    coding-guidelines
+    arch-support
+
+.. only::  subproject and html
+
+   Indices
+   =======
+
+   * :ref:`genindex`

Documentation/rust/quick-start.rst

@@ -0,0 +1,232 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Quick Start
+===========
+
+This document describes how to get started with kernel development in Rust.
+
+
+Requirements: Building
+----------------------
+
+This section explains how to fetch the tools needed for building.
+
+Some of these requirements might be available from Linux distributions
+under names like ``rustc``, ``rust-src``, ``rust-bindgen``, etc. However,
+at the time of writing, they are likely not to be recent enough unless
+the distribution tracks the latest releases.
+
+To easily check whether the requirements are met, the following target
+can be used::
+
+	make LLVM=1 rustavailable
+
+This triggers the same logic used by Kconfig to determine whether
+``RUST_IS_AVAILABLE`` should be enabled; but it also explains why not
+if that is the case.
+
+
+rustc
+*****
+
+A particular version of the Rust compiler is required. Newer versions may or
+may not work because, for the moment, the kernel depends on some unstable
+Rust features.
+
+If ``rustup`` is being used, enter the checked out source code directory
+and run::
+
+	rustup override set $(scripts/min-tool-version.sh rustc)
+
+Otherwise, fetch a standalone installer or install ``rustup`` from:
+
+	https://www.rust-lang.org
+
+
+Rust standard library source
+****************************
+
+The Rust standard library source is required because the build system will
+cross-compile ``core`` and ``alloc``.
+
+If ``rustup`` is being used, run::
+
+	rustup component add rust-src
+
+The components are installed per toolchain, thus upgrading the Rust compiler
+version later on requires re-adding the component.
+
+Otherwise, if a standalone installer is used, the Rust repository may be cloned
+into the installation folder of the toolchain::
+
+	git clone --recurse-submodules \
+		--branch $(scripts/min-tool-version.sh rustc) \
+		https://github.com/rust-lang/rust \
+		$(rustc --print sysroot)/lib/rustlib/src/rust
+
+In this case, upgrading the Rust compiler version later on requires manually
+updating this clone.
+
+
+libclang
+********
+
+``libclang`` (part of LLVM) is used by ``bindgen`` to understand the C code
+in the kernel, which means LLVM needs to be installed; like when the kernel
+is compiled with ``CC=clang`` or ``LLVM=1``.
+
+Linux distributions are likely to have a suitable one available, so it is
+best to check that first.
+
+There are also some binaries for several systems and architectures uploaded at:
+
+	https://releases.llvm.org/download.html
+
+Otherwise, building LLVM takes quite a while, but it is not a complex process:
+
+	https://llvm.org/docs/GettingStarted.html#getting-the-source-code-and-building-llvm
+
+Please see Documentation/kbuild/llvm.rst for more information and further ways
+to fetch pre-built releases and distribution packages.
+
+
+bindgen
+*******
+
+The bindings to the C side of the kernel are generated at build time using
+the ``bindgen`` tool. A particular version is required.
+
+Install it via (note that this will download and build the tool from source)::
+
+	cargo install --locked --version $(scripts/min-tool-version.sh bindgen) bindgen
+
+
+Requirements: Developing
+------------------------
+
+This section explains how to fetch the tools needed for developing. That is,
+they are not needed when just building the kernel.
+
+
+rustfmt
+*******
+
+The ``rustfmt`` tool is used to automatically format all the Rust kernel code,
+including the generated C bindings (for details, please see
+coding-guidelines.rst).
+
+If ``rustup`` is being used, its ``default`` profile already installs the tool,
+thus nothing needs to be done. If another profile is being used, the component
+can be installed manually::
+
+	rustup component add rustfmt
+
+The standalone installers also come with ``rustfmt``.
+
+
+clippy
+******
+
+``clippy`` is a Rust linter. Running it provides extra warnings for Rust code.
+It can be run by passing ``CLIPPY=1`` to ``make`` (for details, please see
+general-information.rst).
+
+If ``rustup`` is being used, its ``default`` profile already installs the tool,
+thus nothing needs to be done. If another profile is being used, the component
+can be installed manually::
+
+	rustup component add clippy
+
+The standalone installers also come with ``clippy``.
+
+
+cargo
+*****
+
+``cargo`` is the Rust native build system. It is currently required to run
+the tests since it is used to build a custom standard library that contains
+the facilities provided by the custom ``alloc`` in the kernel. The tests can
+be run using the ``rusttest`` Make target.
+
+If ``rustup`` is being used, all the profiles already install the tool,
+thus nothing needs to be done.
+
+The standalone installers also come with ``cargo``.
+
+
+rustdoc
+*******
+
+``rustdoc`` is the documentation tool for Rust. It generates pretty HTML
+documentation for Rust code (for details, please see
+general-information.rst).
+
+``rustdoc`` is also used to test the examples provided in documented Rust code
+(called doctests or documentation tests). The ``rusttest`` Make target uses
+this feature.
+
+If ``rustup`` is being used, all the profiles already install the tool,
+thus nothing needs to be done.
+
+The standalone installers also come with ``rustdoc``.
+
+
+rust-analyzer
+*************
+
+The `rust-analyzer <https://rust-analyzer.github.io/>`_ language server can
+be used with many editors to enable syntax highlighting, completion, go to
+definition, and other features.
+
+``rust-analyzer`` needs a configuration file, ``rust-project.json``, which
+can be generated by the ``rust-analyzer`` Make target.
+
+
+Configuration
+-------------
+
+``Rust support`` (``CONFIG_RUST``) needs to be enabled in the ``General setup``
+menu. The option is only shown if a suitable Rust toolchain is found (see
+above), as long as the other requirements are met. In turn, this will make
+visible the rest of options that depend on Rust.
+
+Afterwards, go to::
+
+	Kernel hacking
+	    -> Sample kernel code
+	        -> Rust samples
+
+And enable some sample modules either as built-in or as loadable.
+
+
+Building
+--------
+
+Building a kernel with a complete LLVM toolchain is the best supported setup
+at the moment. That is::
+
+	make LLVM=1
+
+For architectures that do not support a full LLVM toolchain, use::
+
+	make CC=clang
+
+Using GCC also works for some configurations, but it is very experimental at
+the moment.
+
+
+Hacking
+-------
+
+To dive deeper, take a look at the source code of the samples
+at ``samples/rust/``, the Rust support code under ``rust/`` and
+the ``Rust hacking`` menu under ``Kernel hacking``.
+
+If GDB/Binutils is used and Rust symbols are not getting demangled, the reason
+is the toolchain does not support Rust's new v0 mangling scheme yet.
+There are a few ways out:
+
+  - Install a newer release (GDB >= 10.2, Binutils >= 2.36).
+
+  - Some versions of GDB (e.g. vanilla GDB 10.1) are able to use
+    the pre-demangled names embedded in the debug info (``CONFIG_DEBUG_INFO``).

MAINTAINERS

@@ -17762,6 +17762,24 @@ F:	include/rv/
 F:	kernel/trace/rv/
 F:	tools/verification/
 
+RUST
+M:	Miguel Ojeda <ojeda@kernel.org>
+M:	Alex Gaynor <alex.gaynor@gmail.com>
+M:	Wedson Almeida Filho <wedsonaf@gmail.com>
+R:	Boqun Feng <boqun.feng@gmail.com>
+R:	Gary Guo <gary@garyguo.net>
+R:	Björn Roy Baron <bjorn3_gh@protonmail.com>
+L:	rust-for-linux@vger.kernel.org
+S:	Supported
+W:	https://github.com/Rust-for-Linux/linux
+B:	https://github.com/Rust-for-Linux/linux/issues
+T:	git https://github.com/Rust-for-Linux/linux.git rust-next
+F:	Documentation/rust/
+F:	rust/
+F:	samples/rust/
+F:	scripts/*rust*
+K:	\b(?i:rust)\b
+
 RXRPC SOCKETS (AF_RXRPC)
 M:	David Howells <dhowells@redhat.com>
 M:	Marc Dionne <marc.dionne@auristor.com>

Makefile

@@ -120,6 +120,15 @@ endif
 
 export KBUILD_CHECKSRC
 
+# Enable "clippy" (a linter) as part of the Rust compilation.
+#
+# Use 'make CLIPPY=1' to enable it.
+ifeq ("$(origin CLIPPY)", "command line")
+  KBUILD_CLIPPY := $(CLIPPY)
+endif
+
+export KBUILD_CLIPPY
+
 # Use make M=dir or set the environment variable KBUILD_EXTMOD to specify the
 # directory of external module to build. Setting M= takes precedence.
 ifeq ("$(origin M)", "command line")
@@ -288,14 +297,14 @@ no-dot-config-targets := $(clean-targets) \
 			 cscope gtags TAGS tags help% %docs check% coccicheck \
 			 $(version_h) headers headers_% archheaders archscripts \
 			 %asm-generic kernelversion %src-pkg dt_binding_check \
-			 outputmakefile
+			 outputmakefile rustavailable rustfmt rustfmtcheck
 # Installation targets should not require compiler. Unfortunately, vdso_install
 # is an exception where build artifacts may be updated. This must be fixed.
 no-compiler-targets := $(no-dot-config-targets) install dtbs_install \
 			headers_install modules_install kernelrelease image_name
 no-sync-config-targets := $(no-dot-config-targets) %install kernelrelease \
 			  image_name
-single-targets := %.a %.i %.ko %.lds %.ll %.lst %.mod %.o %.s %.symtypes %/
+single-targets := %.a %.i %.rsi %.ko %.lds %.ll %.lst %.mod %.o %.s %.symtypes %/
 
 config-build	:=
 mixed-build	:=
@@ -457,6 +466,7 @@ else
 HOSTCC	= gcc
 HOSTCXX	= g++
 endif
+HOSTRUSTC = rustc
 HOSTPKG_CONFIG	= pkg-config
 
 KBUILD_USERHOSTCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes \
@@ -465,8 +475,26 @@ KBUILD_USERHOSTCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes \
 KBUILD_USERCFLAGS  := $(KBUILD_USERHOSTCFLAGS) $(USERCFLAGS)
 KBUILD_USERLDFLAGS := $(USERLDFLAGS)
 
+# These flags apply to all Rust code in the tree, including the kernel and
+# host programs.
+export rust_common_flags := --edition=2021 \
+			    -Zbinary_dep_depinfo=y \
+			    -Dunsafe_op_in_unsafe_fn -Drust_2018_idioms \
+			    -Dunreachable_pub -Dnon_ascii_idents \
+			    -Wmissing_docs \
+			    -Drustdoc::missing_crate_level_docs \
+			    -Dclippy::correctness -Dclippy::style \
+			    -Dclippy::suspicious -Dclippy::complexity \
+			    -Dclippy::perf \
+			    -Dclippy::let_unit_value -Dclippy::mut_mut \
+			    -Dclippy::needless_bitwise_bool \
+			    -Dclippy::needless_continue \
+			    -Wclippy::dbg_macro
+
 KBUILD_HOSTCFLAGS   := $(KBUILD_USERHOSTCFLAGS) $(HOST_LFS_CFLAGS) $(HOSTCFLAGS)
 KBUILD_HOSTCXXFLAGS := -Wall -O2 $(HOST_LFS_CFLAGS) $(HOSTCXXFLAGS)
+KBUILD_HOSTRUSTFLAGS := $(rust_common_flags) -O -Cstrip=debuginfo \
+			-Zallow-features= $(HOSTRUSTFLAGS)
 KBUILD_HOSTLDFLAGS  := $(HOST_LFS_LDFLAGS) $(HOSTLDFLAGS)
 KBUILD_HOSTLDLIBS   := $(HOST_LFS_LIBS) $(HOSTLDLIBS)
 
@@ -491,6 +519,12 @@ OBJDUMP		= $(CROSS_COMPILE)objdump
 READELF		= $(CROSS_COMPILE)readelf
 STRIP		= $(CROSS_COMPILE)strip
 endif
+RUSTC		= rustc
+RUSTDOC		= rustdoc
+RUSTFMT		= rustfmt
+CLIPPY_DRIVER	= clippy-driver
+BINDGEN		= bindgen
+CARGO		= cargo
 PAHOLE		= pahole
 RESOLVE_BTFIDS	= $(objtree)/tools/bpf/resolve_btfids/resolve_btfids
 LEX		= flex
@@ -516,9 +550,11 @@ CHECKFLAGS     := -D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__ \
 		  -Wbitwise -Wno-return-void -Wno-unknown-attribute $(CF)
 NOSTDINC_FLAGS :=
 CFLAGS_MODULE   =
+RUSTFLAGS_MODULE =
 AFLAGS_MODULE   =
 LDFLAGS_MODULE  =
 CFLAGS_KERNEL	=
+RUSTFLAGS_KERNEL =
 AFLAGS_KERNEL	=
 LDFLAGS_vmlinux =
 
@@ -547,15 +583,43 @@ KBUILD_CFLAGS   := -Wall -Wundef -Werror=strict-prototypes -Wno-trigraphs \
 		   -Werror=return-type -Wno-format-security \
 		   -std=gnu11
 KBUILD_CPPFLAGS := -D__KERNEL__
+KBUILD_RUSTFLAGS := $(rust_common_flags) \
+		    --target=$(objtree)/rust/target.json \
+		    -Cpanic=abort -Cembed-bitcode=n -Clto=n \
+		    -Cforce-unwind-tables=n -Ccodegen-units=1 \
+		    -Csymbol-mangling-version=v0 \
+		    -Crelocation-model=static \
+		    -Zfunction-sections=n \
+		    -Dclippy::float_arithmetic
+
 KBUILD_AFLAGS_KERNEL :=
 KBUILD_CFLAGS_KERNEL :=
+KBUILD_RUSTFLAGS_KERNEL :=
 KBUILD_AFLAGS_MODULE  := -DMODULE
 KBUILD_CFLAGS_MODULE  := -DMODULE
+KBUILD_RUSTFLAGS_MODULE := --cfg MODULE
 KBUILD_LDFLAGS_MODULE :=
 KBUILD_LDFLAGS :=
 CLANG_FLAGS :=
 
+ifeq ($(KBUILD_CLIPPY),1)
+	RUSTC_OR_CLIPPY_QUIET := CLIPPY
+	RUSTC_OR_CLIPPY = $(CLIPPY_DRIVER)
+else
+	RUSTC_OR_CLIPPY_QUIET := RUSTC
+	RUSTC_OR_CLIPPY = $(RUSTC)
+endif
+
+ifdef RUST_LIB_SRC
+	export RUST_LIB_SRC
+endif
+
+# Allows the usage of unstable features in stable compilers.
+export RUSTC_BOOTSTRAP := 1
+
 export ARCH SRCARCH CONFIG_SHELL BASH HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE LD CC HOSTPKG_CONFIG
+export RUSTC RUSTDOC RUSTFMT RUSTC_OR_CLIPPY_QUIET RUSTC_OR_CLIPPY BINDGEN CARGO
+export HOSTRUSTC KBUILD_HOSTRUSTFLAGS
 export CPP AR NM STRIP OBJCOPY OBJDUMP READELF PAHOLE RESOLVE_BTFIDS LEX YACC AWK INSTALLKERNEL
 export PERL PYTHON3 CHECK CHECKFLAGS MAKE UTS_MACHINE HOSTCXX
 export KGZIP KBZIP2 KLZOP LZMA LZ4 XZ ZSTD
@@ -564,9 +628,10 @@ export KBUILD_USERCFLAGS KBUILD_USERLDFLAGS
 
 export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS KBUILD_LDFLAGS
 export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE
+export KBUILD_RUSTFLAGS RUSTFLAGS_KERNEL RUSTFLAGS_MODULE
 export KBUILD_AFLAGS AFLAGS_KERNEL AFLAGS_MODULE
-export KBUILD_AFLAGS_MODULE KBUILD_CFLAGS_MODULE KBUILD_LDFLAGS_MODULE
-export KBUILD_AFLAGS_KERNEL KBUILD_CFLAGS_KERNEL
+export KBUILD_AFLAGS_MODULE KBUILD_CFLAGS_MODULE KBUILD_RUSTFLAGS_MODULE KBUILD_LDFLAGS_MODULE
+export KBUILD_AFLAGS_KERNEL KBUILD_CFLAGS_KERNEL KBUILD_RUSTFLAGS_KERNEL
 export PAHOLE_FLAGS
 
 # Files to ignore in find ... statements
@@ -749,7 +814,7 @@ $(KCONFIG_CONFIG):
 #
 # Do not use $(call cmd,...) here. That would suppress prompts from syncconfig,
 # so you cannot notice that Kconfig is waiting for the user input.
-%/config/auto.conf %/config/auto.conf.cmd %/generated/autoconf.h: $(KCONFIG_CONFIG)
+%/config/auto.conf %/config/auto.conf.cmd %/generated/autoconf.h %/generated/rustc_cfg: $(KCONFIG_CONFIG)
 	$(Q)$(kecho) "  SYNC    $@"
 	$(Q)$(MAKE) -f $(srctree)/Makefile syncconfig
 else # !may-sync-config
@@ -778,10 +843,17 @@ KBUILD_CFLAGS	+= $(call cc-disable-warning, address-of-packed-member)
 
 ifdef CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE
 KBUILD_CFLAGS += -O2
+KBUILD_RUSTFLAGS += -Copt-level=2
 else ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
 KBUILD_CFLAGS += -Os
+KBUILD_RUSTFLAGS += -Copt-level=s
 endif
 
+# Always set `debug-assertions` and `overflow-checks` because their default
+# depends on `opt-level` and `debug-assertions`, respectively.
+KBUILD_RUSTFLAGS += -Cdebug-assertions=$(if $(CONFIG_RUST_DEBUG_ASSERTIONS),y,n)
+KBUILD_RUSTFLAGS += -Coverflow-checks=$(if $(CONFIG_RUST_OVERFLOW_CHECKS),y,n)
+
 # Tell gcc to never replace conditional load with a non-conditional one
 ifdef CONFIG_CC_IS_GCC
 # gcc-10 renamed --param=allow-store-data-races=0 to
@@ -812,6 +884,9 @@ KBUILD_CFLAGS-$(CONFIG_WERROR) += -Werror
 KBUILD_CFLAGS-$(CONFIG_CC_NO_ARRAY_BOUNDS) += -Wno-array-bounds
 KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) $(CONFIG_CC_IMPLICIT_FALLTHROUGH)
 
+KBUILD_RUSTFLAGS-$(CONFIG_WERROR) += -Dwarnings
+KBUILD_RUSTFLAGS += $(KBUILD_RUSTFLAGS-y)
+
 ifdef CONFIG_CC_IS_CLANG
 KBUILD_CPPFLAGS += -Qunused-arguments
 # The kernel builds with '-std=gnu11' so use of GNU extensions is acceptable.
@@ -832,12 +907,15 @@ KBUILD_CFLAGS += $(call cc-disable-warning, dangling-pointer)
 
 ifdef CONFIG_FRAME_POINTER
 KBUILD_CFLAGS	+= -fno-omit-frame-pointer -fno-optimize-sibling-calls
+KBUILD_RUSTFLAGS += -Cforce-frame-pointers=y
 else
 # Some targets (ARM with Thumb2, for example), can't be built with frame
 # pointers.  For those, we don't have FUNCTION_TRACER automatically
 # select FRAME_POINTER.  However, FUNCTION_TRACER adds -pg, and this is
 # incompatible with -fomit-frame-pointer with current GCC, so we don't use
 # -fomit-frame-pointer with FUNCTION_TRACER.
+# In the Rust target specification, "frame-pointer" is set explicitly
+# to "may-omit".
 ifndef CONFIG_FUNCTION_TRACER
 KBUILD_CFLAGS	+= -fomit-frame-pointer
 endif
@@ -902,8 +980,10 @@ ifdef CONFIG_DEBUG_SECTION_MISMATCH
 KBUILD_CFLAGS += -fno-inline-functions-called-once
 endif
 
+# `rustc`'s `-Zfunction-sections` applies to data too (as of 1.59.0).
 ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
 KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections
+KBUILD_RUSTFLAGS_KERNEL += -Zfunction-sections=y
 LDFLAGS_vmlinux += --gc-sections
 endif
 
@@ -1052,10 +1132,11 @@ include $(addprefix $(srctree)/, $(include-y))
 # Do not add $(call cc-option,...) below this line. When you build the kernel
 # from the clean source tree, the GCC plugins do not exist at this point.
 
-# Add user supplied CPPFLAGS, AFLAGS and CFLAGS as the last assignments
+# Add user supplied CPPFLAGS, AFLAGS, CFLAGS and RUSTFLAGS as the last assignments
 KBUILD_CPPFLAGS += $(KCPPFLAGS)
 KBUILD_AFLAGS   += $(KAFLAGS)
 KBUILD_CFLAGS   += $(KCFLAGS)
+KBUILD_RUSTFLAGS += $(KRUSTFLAGS)
 
 KBUILD_LDFLAGS_MODULE += --build-id=sha1
 LDFLAGS_vmlinux += --build-id=sha1
@@ -1164,6 +1245,7 @@ ifeq ($(KBUILD_EXTMOD),)
 core-y			+= kernel/ certs/ mm/ fs/ ipc/ security/ crypto/
 core-$(CONFIG_BLOCK)	+= block/
 core-$(CONFIG_IO_URING)	+= io_uring/
+core-$(CONFIG_RUST)	+= rust/
 
 vmlinux-dirs	:= $(patsubst %/,%,$(filter %/, \
 		     $(core-y) $(core-m) $(drivers-y) $(drivers-m) \
@@ -1269,6 +1351,10 @@ prepare0: archprepare
 
 # All the preparing..
 prepare: prepare0
+ifdef CONFIG_RUST
+	$(Q)$(CONFIG_SHELL) $(srctree)/scripts/rust_is_available.sh -v
+	$(Q)$(MAKE) $(build)=rust
+endif
 
 PHONY += remove-stale-files
 remove-stale-files:
@@ -1540,7 +1626,7 @@ endif # CONFIG_MODULES
 # Directories & files removed with 'make clean'
 CLEAN_FILES += include/ksym vmlinux.symvers modules-only.symvers \
 	       modules.builtin modules.builtin.modinfo modules.nsdeps \
-	       compile_commands.json .thinlto-cache
+	       compile_commands.json .thinlto-cache rust/test rust/doc
 
 # Directories & files removed with 'make mrproper'
 MRPROPER_FILES += include/config include/generated          \
@@ -1551,7 +1637,8 @@ MRPROPER_FILES += include/config include/generated          \
 		  certs/signing_key.pem \
 		  certs/x509.genkey \
 		  vmlinux-gdb.py \
-		  *.spec
+		  *.spec \
+		  rust/target.json rust/libmacros.so
 
 # clean - Delete most, but leave enough to build external modules
 #
@@ -1576,6 +1663,9 @@ $(mrproper-dirs):
 
 mrproper: clean $(mrproper-dirs)
 	$(call cmd,rmfiles)
+	@find . $(RCS_FIND_IGNORE) \
+		\( -name '*.rmeta' \) \
+		-type f -print | xargs rm -f
 
 # distclean
 #
@@ -1663,6 +1753,24 @@ help:
 	@echo  '  kselftest-merge   - Merge all the config dependencies of'
 	@echo  '		      kselftest to existing .config.'
 	@echo  ''
+	@echo  'Rust targets:'
+	@echo  '  rustavailable   - Checks whether the Rust toolchain is'
+	@echo  '		    available and, if not, explains why.'
+	@echo  '  rustfmt	  - Reformat all the Rust code in the kernel'
+	@echo  '  rustfmtcheck	  - Checks if all the Rust code in the kernel'
+	@echo  '		    is formatted, printing a diff otherwise.'
+	@echo  '  rustdoc	  - Generate Rust documentation'
+	@echo  '		    (requires kernel .config)'
+	@echo  '  rusttest        - Runs the Rust tests'
+	@echo  '                    (requires kernel .config; downloads external repos)'
+	@echo  '  rust-analyzer	  - Generate rust-project.json rust-analyzer support file'
+	@echo  '		    (requires kernel .config)'
+	@echo  '  dir/file.[os]   - Build specified target only'
+	@echo  '  dir/file.rsi    - Build macro expanded source, similar to C preprocessing.'
+	@echo  '                    Run with RUSTFMT=n to skip reformatting if needed.'
+	@echo  '                    The output is not intended to be compilable.'
+	@echo  '  dir/file.ll     - Build the LLVM assembly file'
+	@echo  ''
 	@$(if $(dtstree), \
 		echo 'Devicetree:'; \
 		echo '* dtbs             - Build device tree blobs for enabled boards'; \
@@ -1735,6 +1843,52 @@ PHONY += $(DOC_TARGETS)
 $(DOC_TARGETS):
 	$(Q)$(MAKE) $(build)=Documentation $@
 
+
+# Rust targets
+# ---------------------------------------------------------------------------
+
+# "Is Rust available?" target
+PHONY += rustavailable
+rustavailable:
+	$(Q)$(CONFIG_SHELL) $(srctree)/scripts/rust_is_available.sh -v && echo "Rust is available!"
+
+# Documentation target
+#
+# Using the singular to avoid running afoul of `no-dot-config-targets`.
+PHONY += rustdoc
+rustdoc: prepare
+	$(Q)$(MAKE) $(build)=rust $@
+
+# Testing target
+PHONY += rusttest
+rusttest: prepare
+	$(Q)$(MAKE) $(build)=rust $@
+
+# Formatting targets
+PHONY += rustfmt rustfmtcheck
+
+# We skip `rust/alloc` since we want to minimize the diff w.r.t. upstream.
+#
+# We match using absolute paths since `find` does not resolve them
+# when matching, which is a problem when e.g. `srctree` is `..`.
+# We `grep` afterwards in order to remove the directory entry itself.
+rustfmt:
+	$(Q)find $(abs_srctree) -type f -name '*.rs' \
+		-o -path $(abs_srctree)/rust/alloc -prune \
+		-o -path $(abs_objtree)/rust/test -prune \
+		| grep -Fv $(abs_srctree)/rust/alloc \
+		| grep -Fv $(abs_objtree)/rust/test \
+		| grep -Fv generated \
+		| xargs $(RUSTFMT) $(rustfmt_flags)
+
+rustfmtcheck: rustfmt_flags = --check
+rustfmtcheck: rustfmt
+
+# IDE support targets
+PHONY += rust-analyzer
+rust-analyzer:
+	$(Q)$(MAKE) $(build)=rust $@
+
 # Misc
 # ---------------------------------------------------------------------------
 
@@ -1904,7 +2058,7 @@ $(clean-dirs):
 clean: $(clean-dirs)
 	$(call cmd,rmfiles)
 	@find $(or $(KBUILD_EXTMOD), .) $(RCS_FIND_IGNORE) \
-		\( -name '*.[aios]' -o -name '*.ko' -o -name '.*.cmd' \
+		\( -name '*.[aios]' -o -name '*.rsi' -o -name '*.ko' -o -name '.*.cmd' \
 		-o -name '*.ko.*' \
 		-o -name '*.dtb' -o -name '*.dtbo' -o -name '*.dtb.S' -o -name '*.dt.yaml' \
 		-o -name '*.dwo' -o -name '*.lst' \

arch/Kconfig

@@ -355,6 +355,12 @@ config HAVE_RSEQ
 	  This symbol should be selected by an architecture if it
 	  supports an implementation of restartable sequences.
 
+config HAVE_RUST
+	bool
+	help
+	  This symbol should be selected by an architecture if it
+	  supports Rust.
+
 config HAVE_FUNCTION_ARG_ACCESS_API
 	bool
 	help

arch/x86/Kconfig

@@ -257,6 +257,7 @@ config X86
 	select HAVE_STATIC_CALL_INLINE		if HAVE_OBJTOOL
 	select HAVE_PREEMPT_DYNAMIC_CALL
 	select HAVE_RSEQ
+	select HAVE_RUST			if X86_64
 	select HAVE_SYSCALL_TRACEPOINTS
 	select HAVE_UACCESS_VALIDATION		if HAVE_OBJTOOL
 	select HAVE_UNSTABLE_SCHED_CLOCK

arch/x86/Makefile

@@ -68,6 +68,7 @@ export BITS
 #    https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53383
 #
 KBUILD_CFLAGS += -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx
+KBUILD_RUSTFLAGS += -Ctarget-feature=-sse,-sse2,-sse3,-ssse3,-sse4.1,-sse4.2,-avx,-avx2
 
 ifeq ($(CONFIG_X86_KERNEL_IBT),y)
 #
@@ -155,8 +156,17 @@ else
         cflags-$(CONFIG_GENERIC_CPU)	+= -mtune=generic
         KBUILD_CFLAGS += $(cflags-y)
 
+        rustflags-$(CONFIG_MK8)		+= -Ctarget-cpu=k8
+        rustflags-$(CONFIG_MPSC)	+= -Ctarget-cpu=nocona
+        rustflags-$(CONFIG_MCORE2)	+= -Ctarget-cpu=core2
+        rustflags-$(CONFIG_MATOM)	+= -Ctarget-cpu=atom
+        rustflags-$(CONFIG_GENERIC_CPU)	+= -Ztune-cpu=generic
+        KBUILD_RUSTFLAGS += $(rustflags-y)
+
         KBUILD_CFLAGS += -mno-red-zone
         KBUILD_CFLAGS += -mcmodel=kernel
+        KBUILD_RUSTFLAGS += -Cno-redzone=y
+        KBUILD_RUSTFLAGS += -Ccode-model=kernel
 endif
 
 #

include/linux/compiler_types.h

@@ -4,8 +4,12 @@
 
 #ifndef __ASSEMBLY__
 
+/*
+ * Skipped when running bindgen due to a libclang issue;
+ * see https://github.com/rust-lang/rust-bindgen/issues/2244.
+ */
 #if defined(CONFIG_DEBUG_INFO_BTF) && defined(CONFIG_PAHOLE_HAS_BTF_TAG) && \
-	__has_attribute(btf_type_tag)
+	__has_attribute(btf_type_tag) && !defined(__BINDGEN__)
 # define BTF_TYPE_TAG(value) __attribute__((btf_type_tag(#value)))
 #else
 # define BTF_TYPE_TAG(value) /* nothing */

include/linux/kallsyms.h

@@ -15,7 +15,7 @@
 
 #include <asm/sections.h>
 
-#define KSYM_NAME_LEN 128
+#define KSYM_NAME_LEN 512
 #define KSYM_SYMBOL_LEN (sizeof("%s+%#lx/%#lx [%s %s]") + \
 			(KSYM_NAME_LEN - 1) + \
 			2*(BITS_PER_LONG*3/10) + (MODULE_NAME_LEN - 1) + \

init/Kconfig

@@ -60,6 +60,17 @@ config LLD_VERSION
 	default $(ld-version) if LD_IS_LLD
 	default 0
 
+config RUST_IS_AVAILABLE
+	def_bool $(success,$(srctree)/scripts/rust_is_available.sh)
+	help
+	  This shows whether a suitable Rust toolchain is available (found).
+
+	  Please see Documentation/rust/quick-start.rst for instructions on how
+	  to satify the build requirements of Rust support.
+
+	  In particular, the Makefile target 'rustavailable' is useful to check
+	  why the Rust toolchain is not being detected.
+
 config CC_CAN_LINK
 	bool
 	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT
@@ -147,7 +158,8 @@ config WERROR
 	default y
 	help
 	  A kernel build should not cause any compiler warnings, and this
-	  enables the '-Werror' flag to enforce that rule by default.
+	  enables the '-Werror' (for C) and '-Dwarnings' (for Rust) flags
+	  to enforce that rule by default.
 
 	  However, if you have a new (or very old) compiler with odd and
 	  unusual warnings, or you have some architecture with problems,
@@ -1899,6 +1911,38 @@ config PROFILING
 	  Say Y here to enable the extended profiling support mechanisms used
 	  by profilers.
 
+config RUST
+	bool "Rust support"
+	depends on HAVE_RUST
+	depends on RUST_IS_AVAILABLE
+	depends on !MODVERSIONS
+	depends on !GCC_PLUGINS
+	depends on !RANDSTRUCT
+	depends on !DEBUG_INFO_BTF
+	select CONSTRUCTORS
+	help
+	  Enables Rust support in the kernel.
+
+	  This allows other Rust-related options, like drivers written in Rust,
+	  to be selected.
+
+	  It is also required to be able to load external kernel modules
+	  written in Rust.
+
+	  See Documentation/rust/ for more information.
+
+	  If unsure, say N.
+
+config RUSTC_VERSION_TEXT
+	string
+	depends on RUST
+	default $(shell,command -v $(RUSTC) >/dev/null 2>&1 && $(RUSTC) --version || echo n)
+
+config BINDGEN_VERSION_TEXT
+	string
+	depends on RUST
+	default $(shell,command -v $(BINDGEN) >/dev/null 2>&1 && $(BINDGEN) --version || echo n)
+
 #
 # Place an empty function call at each tracepoint site. Can be
 # dynamically changed for a probe function.

kernel/configs/rust.config

@@ -0,0 +1 @@
+CONFIG_RUST=y

kernel/kallsyms.c

@@ -50,12 +50,20 @@ static unsigned int kallsyms_expand_symbol(unsigned int off,
 	data = &kallsyms_names[off];
 	len = *data;
 	data++;
+	off++;
+
+	/* If MSB is 1, it is a "big" symbol, so needs an additional byte. */
+	if ((len & 0x80) != 0) {
+		len = (len & 0x7F) | (*data << 7);
+		data++;
+		off++;
+	}
 
 	/*
 	 * Update the offset to return the offset for the next symbol on
 	 * the compressed stream.
 	 */
-	off += len + 1;
+	off += len;
 
 	/*
 	 * For every byte on the compressed symbol data, copy the table
@@ -108,7 +116,7 @@ static char kallsyms_get_symbol_type(unsigned int off)
 static unsigned int get_symbol_offset(unsigned long pos)
 {
 	const u8 *name;
-	int i;
+	int i, len;
 
 	/*
 	 * Use the closest marker we have. We have markers every 256 positions,
@@ -122,8 +130,18 @@ static unsigned int get_symbol_offset(unsigned long pos)
 	 * so we just need to add the len to the current pointer for every
 	 * symbol we wish to skip.
 	 */
-	for (i = 0; i < (pos & 0xFF); i++)
-		name = name + (*name) + 1;
+	for (i = 0; i < (pos & 0xFF); i++) {
+		len = *name;
+
+		/*
+		 * If MSB is 1, it is a "big" symbol, so we need to look into
+		 * the next byte (and skip it, too).
+		 */
+		if ((len & 0x80) != 0)
+			len = ((len & 0x7F) | (name[1] << 7)) + 1;
+
+		name = name + len + 1;
+	}
 
 	return name - kallsyms_names;
 }

kernel/livepatch/core.c

@@ -213,7 +213,7 @@ static int klp_resolve_symbols(Elf_Shdr *sechdrs, const char *strtab,
 	 * we use the smallest/strictest upper bound possible (56, based on
 	 * the current definition of MODULE_NAME_LEN) to prevent overflows.
 	 */
-	BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 128);
+	BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 512);
 
 	relas = (Elf_Rela *) relasec->sh_addr;
 	/* For each rela in this klp relocation section */
@@ -227,7 +227,7 @@ static int klp_resolve_symbols(Elf_Shdr *sechdrs, const char *strtab,
 
 		/* Format: .klp.sym.sym_objname.sym_name,sympos */
 		cnt = sscanf(strtab + sym->st_name,
-			     ".klp.sym.%55[^.].%127[^,],%lu",
+			     ".klp.sym.%55[^.].%511[^,],%lu",
 			     sym_objname, sym_name, &sympos);
 		if (cnt != 3) {
 			pr_err("symbol %s has an incorrectly formatted name\n",

lib/Kconfig.debug

@@ -2710,6 +2710,40 @@ config HYPERV_TESTING
 
 endmenu # "Kernel Testing and Coverage"
 
+menu "Rust hacking"
+
+config RUST_DEBUG_ASSERTIONS
+	bool "Debug assertions"
+	depends on RUST
+	help
+	  Enables rustc's `-Cdebug-assertions` codegen option.
+
+	  This flag lets you turn `cfg(debug_assertions)` conditional
+	  compilation on or off. This can be used to enable extra debugging
+	  code in development but not in production. For example, it controls
+	  the behavior of the standard library's `debug_assert!` macro.
+
+	  Note that this will apply to all Rust code, including `core`.
+
+	  If unsure, say N.
+
+config RUST_OVERFLOW_CHECKS
+	bool "Overflow checks"
+	default y
+	depends on RUST
+	help
+	  Enables rustc's `-Coverflow-checks` codegen option.
+
+	  This flag allows you to control the behavior of runtime integer
+	  overflow. When overflow-checks are enabled, a Rust panic will occur
+	  on overflow.
+
+	  Note that this will apply to all Rust code, including `core`.
+
+	  If unsure, say Y.
+
+endmenu # "Rust"
+
 source "Documentation/Kconfig"
 
 endmenu # Kernel hacking

lib/vsprintf.c

@@ -2246,6 +2246,9 @@ int __init no_hash_pointers_enable(char *str)
 }
 early_param("no_hash_pointers", no_hash_pointers_enable);
 
+/* Used for Rust formatting ('%pA'). */
+char *rust_fmt_argument(char *buf, char *end, void *ptr);
+
 /*
  * Show a '%p' thing.  A kernel extension is that the '%p' is followed
  * by an extra set of alphanumeric characters that are extended format
@@ -2372,6 +2375,10 @@ early_param("no_hash_pointers", no_hash_pointers_enable);
  *
  * Note: The default behaviour (unadorned %p) is to hash the address,
  * rendering it useful as a unique identifier.
+ *
+ * There is also a '%pA' format specifier, but it is only intended to be used
+ * from Rust code to format core::fmt::Arguments. Do *not* use it from C.
+ * See rust/kernel/print.rs for details.
  */
 static noinline_for_stack
 char *pointer(const char *fmt, char *buf, char *end, void *ptr,
@@ -2444,6 +2451,12 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
 		return device_node_string(buf, end, ptr, spec, fmt + 1);
 	case 'f':
 		return fwnode_string(buf, end, ptr, spec, fmt + 1);
+	case 'A':
+		if (!IS_ENABLED(CONFIG_RUST)) {
+			WARN_ONCE(1, "Please remove %%pA from non-Rust code\n");
+			return error_string(buf, end, "(%pA?)", spec);
+		}
+		return rust_fmt_argument(buf, end, ptr);
 	case 'x':
 		return pointer_string(buf, end, ptr, spec);
 	case 'e':

rust/.gitignore

@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0
+
+target.json
+bindings_generated.rs
+bindings_helpers_generated.rs
+exports_*_generated.h
+doc/
+test/

rust/Makefile

@@ -0,0 +1,381 @@
+# SPDX-License-Identifier: GPL-2.0
+
+always-$(CONFIG_RUST) += target.json
+no-clean-files += target.json
+
+obj-$(CONFIG_RUST) += core.o compiler_builtins.o
+always-$(CONFIG_RUST) += exports_core_generated.h
+
+# Missing prototypes are expected in the helpers since these are exported
+# for Rust only, thus there is no header nor prototypes.
+obj-$(CONFIG_RUST) += helpers.o
+CFLAGS_REMOVE_helpers.o = -Wmissing-prototypes -Wmissing-declarations
+
+always-$(CONFIG_RUST) += libmacros.so
+no-clean-files += libmacros.so
+
+always-$(CONFIG_RUST) += bindings/bindings_generated.rs bindings/bindings_helpers_generated.rs
+obj-$(CONFIG_RUST) += alloc.o bindings.o kernel.o
+always-$(CONFIG_RUST) += exports_alloc_generated.h exports_bindings_generated.h \
+    exports_kernel_generated.h
+
+obj-$(CONFIG_RUST) += exports.o
+
+# Avoids running `$(RUSTC)` for the sysroot when it may not be available.
+ifdef CONFIG_RUST
+
+# `$(rust_flags)` is passed in case the user added `--sysroot`.
+rustc_sysroot := $(shell $(RUSTC) $(rust_flags) --print sysroot)
+rustc_host_target := $(shell $(RUSTC) --version --verbose | grep -F 'host: ' | cut -d' ' -f2)
+RUST_LIB_SRC ?= $(rustc_sysroot)/lib/rustlib/src/rust/library
+
+ifeq ($(quiet),silent_)
+cargo_quiet=-q
+rust_test_quiet=-q
+rustdoc_test_quiet=--test-args -q
+else ifeq ($(quiet),quiet_)
+rust_test_quiet=-q
+rustdoc_test_quiet=--test-args -q
+else
+cargo_quiet=--verbose
+endif
+
+core-cfgs = \
+    --cfg no_fp_fmt_parse
+
+alloc-cfgs = \
+    --cfg no_fmt \
+    --cfg no_global_oom_handling \
+    --cfg no_macros \
+    --cfg no_rc \
+    --cfg no_str \
+    --cfg no_string \
+    --cfg no_sync \
+    --cfg no_thin
+
+quiet_cmd_rustdoc = RUSTDOC $(if $(rustdoc_host),H, ) $<
+      cmd_rustdoc = \
+	OBJTREE=$(abspath $(objtree)) \
+	$(RUSTDOC) $(if $(rustdoc_host),$(rust_common_flags),$(rust_flags)) \
+		$(rustc_target_flags) -L$(objtree)/$(obj) \
+		--output $(objtree)/$(obj)/doc \
+		--crate-name $(subst rustdoc-,,$@) \
+		@$(objtree)/include/generated/rustc_cfg $<
+
+# The `html_logo_url` and `html_favicon_url` forms of the `doc` attribute
+# can be used to specify a custom logo. However:
+#   - The given value is used as-is, thus it cannot be relative or a local file
+#     (unlike the non-custom case) since the generated docs have subfolders.
+#   - It requires adding it to every crate.
+#   - It requires changing `core` which comes from the sysroot.
+#
+# Using `-Zcrate-attr` would solve the last two points, but not the first.
+# The https://github.com/rust-lang/rfcs/pull/3226 RFC suggests two new
+# command-like flags to solve the issue. Meanwhile, we use the non-custom case
+# and then retouch the generated files.
+rustdoc: rustdoc-core rustdoc-macros rustdoc-compiler_builtins \
+    rustdoc-alloc rustdoc-kernel
+	$(Q)cp $(srctree)/Documentation/images/logo.svg $(objtree)/$(obj)/doc
+	$(Q)cp $(srctree)/Documentation/images/COPYING-logo $(objtree)/$(obj)/doc
+	$(Q)find $(objtree)/$(obj)/doc -name '*.html' -type f -print0 | xargs -0 sed -Ei \
+		-e 's:rust-logo\.svg:logo.svg:g' \
+		-e 's:rust-logo\.png:logo.svg:g' \
+		-e 's:favicon\.svg:logo.svg:g' \
+		-e 's:<link rel="alternate icon" type="image/png" href="[./]*favicon-(16x16|32x32)\.png">::g'
+	$(Q)echo '.logo-container > img { object-fit: contain; }' \
+		>> $(objtree)/$(obj)/doc/rustdoc.css
+
+rustdoc-macros: private rustdoc_host = yes
+rustdoc-macros: private rustc_target_flags = --crate-type proc-macro \
+    --extern proc_macro
+rustdoc-macros: $(src)/macros/lib.rs FORCE
+	$(call if_changed,rustdoc)
+
+rustdoc-core: private rustc_target_flags = $(core-cfgs)
+rustdoc-core: $(RUST_LIB_SRC)/core/src/lib.rs FORCE
+	$(call if_changed,rustdoc)
+
+rustdoc-compiler_builtins: $(src)/compiler_builtins.rs rustdoc-core FORCE
+	$(call if_changed,rustdoc)
+
+# We need to allow `rustdoc::broken_intra_doc_links` because some
+# `no_global_oom_handling` functions refer to non-`no_global_oom_handling`
+# functions. Ideally `rustdoc` would have a way to distinguish broken links
+# due to things that are "configured out" vs. entirely non-existing ones.
+rustdoc-alloc: private rustc_target_flags = $(alloc-cfgs) \
+    -Arustdoc::broken_intra_doc_links
+rustdoc-alloc: $(src)/alloc/lib.rs rustdoc-core rustdoc-compiler_builtins FORCE
+	$(call if_changed,rustdoc)
+
+rustdoc-kernel: private rustc_target_flags = --extern alloc \
+    --extern macros=$(objtree)/$(obj)/libmacros.so \
+    --extern bindings
+rustdoc-kernel: $(src)/kernel/lib.rs rustdoc-core rustdoc-macros \
+    rustdoc-compiler_builtins rustdoc-alloc $(obj)/libmacros.so \
+    $(obj)/bindings.o FORCE
+	$(call if_changed,rustdoc)
+
+quiet_cmd_rustc_test_library = RUSTC TL $<
+      cmd_rustc_test_library = \
+	OBJTREE=$(abspath $(objtree)) \
+	$(RUSTC) $(rust_common_flags) \
+		@$(objtree)/include/generated/rustc_cfg $(rustc_target_flags) \
+		--crate-type $(if $(rustc_test_library_proc),proc-macro,rlib) \
+		--out-dir $(objtree)/$(obj)/test --cfg testlib \
+		--sysroot $(objtree)/$(obj)/test/sysroot \
+		-L$(objtree)/$(obj)/test \
+		--crate-name $(subst rusttest-,,$(subst rusttestlib-,,$@)) $<
+
+rusttestlib-macros: private rustc_target_flags = --extern proc_macro
+rusttestlib-macros: private rustc_test_library_proc = yes
+rusttestlib-macros: $(src)/macros/lib.rs rusttest-prepare FORCE
+	$(call if_changed,rustc_test_library)
+
+rusttestlib-bindings: $(src)/bindings/lib.rs rusttest-prepare FORCE
+	$(call if_changed,rustc_test_library)
+
+quiet_cmd_rustdoc_test = RUSTDOC T $<
+      cmd_rustdoc_test = \
+	OBJTREE=$(abspath $(objtree)) \
+	$(RUSTDOC) --test $(rust_common_flags) \
+		@$(objtree)/include/generated/rustc_cfg \
+		$(rustc_target_flags) $(rustdoc_test_target_flags) \
+		--sysroot $(objtree)/$(obj)/test/sysroot $(rustdoc_test_quiet) \
+		-L$(objtree)/$(obj)/test --output $(objtree)/$(obj)/doc \
+		--crate-name $(subst rusttest-,,$@) $<
+
+# We cannot use `-Zpanic-abort-tests` because some tests are dynamic,
+# so for the moment we skip `-Cpanic=abort`.
+quiet_cmd_rustc_test = RUSTC T  $<
+      cmd_rustc_test = \
+	OBJTREE=$(abspath $(objtree)) \
+	$(RUSTC) --test $(rust_common_flags) \
+		@$(objtree)/include/generated/rustc_cfg \
+		$(rustc_target_flags) --out-dir $(objtree)/$(obj)/test \
+		--sysroot $(objtree)/$(obj)/test/sysroot \
+		-L$(objtree)/$(obj)/test \
+		--crate-name $(subst rusttest-,,$@) $<; \
+	$(objtree)/$(obj)/test/$(subst rusttest-,,$@) $(rust_test_quiet) \
+		$(rustc_test_run_flags)
+
+rusttest: rusttest-macros rusttest-kernel
+
+# This prepares a custom sysroot with our custom `alloc` instead of
+# the standard one.
+#
+# This requires several hacks:
+#   - Unlike `core` and `alloc`, `std` depends on more than a dozen crates,
+#     including third-party crates that need to be downloaded, plus custom
+#     `build.rs` steps. Thus hardcoding things here is not maintainable.
+#   - `cargo` knows how to build the standard library, but it is an unstable
+#     feature so far (`-Zbuild-std`).
+#   - `cargo` only considers the use case of building the standard library
+#     to use it in a given package. Thus we need to create a dummy package
+#     and pick the generated libraries from there.
+#   - Since we only keep a subset of upstream `alloc` in-tree, we need
+#     to recreate it on the fly by putting our sources on top.
+#   - The usual ways of modifying the dependency graph in `cargo` do not seem
+#     to apply for the `-Zbuild-std` steps, thus we have to mislead it
+#     by modifying the sources in the sysroot.
+#   - To avoid messing with the user's Rust installation, we create a clone
+#     of the sysroot. However, `cargo` ignores `RUSTFLAGS` in the `-Zbuild-std`
+#     steps, thus we use a wrapper binary passed via `RUSTC` to pass the flag.
+#
+# In the future, we hope to avoid the whole ordeal by either:
+#   - Making the `test` crate not depend on `std` (either improving upstream
+#     or having our own custom crate).
+#   - Making the tests run in kernel space (requires the previous point).
+#   - Making `std` and friends be more like a "normal" crate, so that
+#     `-Zbuild-std` and related hacks are not needed.
+quiet_cmd_rustsysroot = RUSTSYSROOT
+      cmd_rustsysroot = \
+	rm -rf $(objtree)/$(obj)/test; \
+	mkdir -p $(objtree)/$(obj)/test; \
+	cp -a $(rustc_sysroot) $(objtree)/$(obj)/test/sysroot; \
+	cp -r $(srctree)/$(src)/alloc/* \
+		$(objtree)/$(obj)/test/sysroot/lib/rustlib/src/rust/library/alloc/src; \
+	echo '\#!/bin/sh' > $(objtree)/$(obj)/test/rustc_sysroot; \
+	echo "$(RUSTC) --sysroot=$(abspath $(objtree)/$(obj)/test/sysroot) \"\$$@\"" \
+		>> $(objtree)/$(obj)/test/rustc_sysroot; \
+	chmod u+x $(objtree)/$(obj)/test/rustc_sysroot; \
+	$(CARGO) -q new $(objtree)/$(obj)/test/dummy; \
+	RUSTC=$(objtree)/$(obj)/test/rustc_sysroot $(CARGO) $(cargo_quiet) \
+		test -Zbuild-std --target $(rustc_host_target) \
+		--manifest-path $(objtree)/$(obj)/test/dummy/Cargo.toml; \
+	rm $(objtree)/$(obj)/test/sysroot/lib/rustlib/$(rustc_host_target)/lib/*; \
+	cp $(objtree)/$(obj)/test/dummy/target/$(rustc_host_target)/debug/deps/* \
+		$(objtree)/$(obj)/test/sysroot/lib/rustlib/$(rustc_host_target)/lib
+
+rusttest-prepare: FORCE
+	$(call if_changed,rustsysroot)
+
+rusttest-macros: private rustc_target_flags = --extern proc_macro
+rusttest-macros: private rustdoc_test_target_flags = --crate-type proc-macro
+rusttest-macros: $(src)/macros/lib.rs rusttest-prepare FORCE
+	$(call if_changed,rustc_test)
+	$(call if_changed,rustdoc_test)
+
+rusttest-kernel: private rustc_target_flags = --extern alloc \
+    --extern macros --extern bindings
+rusttest-kernel: $(src)/kernel/lib.rs rusttest-prepare \
+    rusttestlib-macros rusttestlib-bindings FORCE
+	$(call if_changed,rustc_test)
+	$(call if_changed,rustc_test_library)
+
+filechk_rust_target = $(objtree)/scripts/generate_rust_target < $<
+
+$(obj)/target.json: $(objtree)/include/config/auto.conf FORCE
+	$(call filechk,rust_target)
+
+ifdef CONFIG_CC_IS_CLANG
+bindgen_c_flags = $(c_flags)
+else
+# bindgen relies on libclang to parse C. Ideally, bindgen would support a GCC
+# plugin backend and/or the Clang driver would be perfectly compatible with GCC.
+#
+# For the moment, here we are tweaking the flags on the fly. This is a hack,
+# and some kernel configurations may not work (e.g. `GCC_PLUGIN_RANDSTRUCT`
+# if we end up using one of those structs).
+bindgen_skip_c_flags := -mno-fp-ret-in-387 -mpreferred-stack-boundary=% \
+	-mskip-rax-setup -mgeneral-regs-only -msign-return-address=% \
+	-mindirect-branch=thunk-extern -mindirect-branch-register \
+	-mfunction-return=thunk-extern -mrecord-mcount -mabi=lp64 \
+	-mindirect-branch-cs-prefix -mstack-protector-guard% -mtraceback=no \
+	-mno-pointers-to-nested-functions -mno-string \
+	-mno-strict-align -mstrict-align \
+	-fconserve-stack -falign-jumps=% -falign-loops=% \
+	-femit-struct-debug-baseonly -fno-ipa-cp-clone -fno-ipa-sra \
+	-fno-partial-inlining -fplugin-arg-arm_ssp_per_task_plugin-% \
+	-fno-reorder-blocks -fno-allow-store-data-races -fasan-shadow-offset=% \
+	-fzero-call-used-regs=% -fno-stack-clash-protection \
+	-fno-inline-functions-called-once \
+	--param=% --param asan-%
+
+# Derived from `scripts/Makefile.clang`.
+BINDGEN_TARGET_x86	:= x86_64-linux-gnu
+BINDGEN_TARGET		:= $(BINDGEN_TARGET_$(SRCARCH))
+
+# All warnings are inhibited since GCC builds are very experimental,
+# many GCC warnings are not supported by Clang, they may only appear in
+# some configurations, with new GCC versions, etc.
+bindgen_extra_c_flags = -w --target=$(BINDGEN_TARGET)
+
+bindgen_c_flags = $(filter-out $(bindgen_skip_c_flags), $(c_flags)) \
+	$(bindgen_extra_c_flags)
+endif
+
+ifdef CONFIG_LTO
+bindgen_c_flags_lto = $(filter-out $(CC_FLAGS_LTO), $(bindgen_c_flags))
+else
+bindgen_c_flags_lto = $(bindgen_c_flags)
+endif
+
+bindgen_c_flags_final = $(bindgen_c_flags_lto) -D__BINDGEN__
+
+quiet_cmd_bindgen = BINDGEN $@
+      cmd_bindgen = \
+	$(BINDGEN) $< $(bindgen_target_flags) \
+		--use-core --with-derive-default --ctypes-prefix core::ffi --no-layout-tests \
+		--no-debug '.*' \
+		--size_t-is-usize -o $@ -- $(bindgen_c_flags_final) -DMODULE \
+		$(bindgen_target_cflags) $(bindgen_target_extra)
+
+$(obj)/bindings/bindings_generated.rs: private bindgen_target_flags = \
+    $(shell grep -v '^\#\|^$$' $(srctree)/$(src)/bindgen_parameters)
+$(obj)/bindings/bindings_generated.rs: $(src)/bindings/bindings_helper.h \
+    $(src)/bindgen_parameters FORCE
+	$(call if_changed_dep,bindgen)
+
+# See `CFLAGS_REMOVE_helpers.o` above. In addition, Clang on C does not warn
+# with `-Wmissing-declarations` (unlike GCC), so it is not strictly needed here
+# given it is `libclang`; but for consistency, future Clang changes and/or
+# a potential future GCC backend for `bindgen`, we disable it too.
+$(obj)/bindings/bindings_helpers_generated.rs: private bindgen_target_flags = \
+    --blacklist-type '.*' --whitelist-var '' \
+    --whitelist-function 'rust_helper_.*'
+$(obj)/bindings/bindings_helpers_generated.rs: private bindgen_target_cflags = \
+    -I$(objtree)/$(obj) -Wno-missing-prototypes -Wno-missing-declarations
+$(obj)/bindings/bindings_helpers_generated.rs: private bindgen_target_extra = ; \
+    sed -Ei 's/pub fn rust_helper_([a-zA-Z0-9_]*)/#[link_name="rust_helper_\1"]\n    pub fn \1/g' $@
+$(obj)/bindings/bindings_helpers_generated.rs: $(src)/helpers.c FORCE
+	$(call if_changed_dep,bindgen)
+
+quiet_cmd_exports = EXPORTS $@
+      cmd_exports = \
+	$(NM) -p --defined-only $< \
+		| grep -E ' (T|R|D) ' | cut -d ' ' -f 3 \
+		| xargs -Isymbol \
+		echo 'EXPORT_SYMBOL_RUST_GPL(symbol);' > $@
+
+$(obj)/exports_core_generated.h: $(obj)/core.o FORCE
+	$(call if_changed,exports)
+
+$(obj)/exports_alloc_generated.h: $(obj)/alloc.o FORCE
+	$(call if_changed,exports)
+
+$(obj)/exports_bindings_generated.h: $(obj)/bindings.o FORCE
+	$(call if_changed,exports)
+
+$(obj)/exports_kernel_generated.h: $(obj)/kernel.o FORCE
+	$(call if_changed,exports)
+
+quiet_cmd_rustc_procmacro = $(RUSTC_OR_CLIPPY_QUIET) P $@
+      cmd_rustc_procmacro = \
+	$(RUSTC_OR_CLIPPY) $(rust_common_flags) \
+		--emit=dep-info,link --extern proc_macro \
+		--crate-type proc-macro --out-dir $(objtree)/$(obj) \
+		--crate-name $(patsubst lib%.so,%,$(notdir $@)) $<; \
+	mv $(objtree)/$(obj)/$(patsubst lib%.so,%,$(notdir $@)).d $(depfile); \
+	sed -i '/^\#/d' $(depfile)
+
+# Procedural macros can only be used with the `rustc` that compiled it.
+# Therefore, to get `libmacros.so` automatically recompiled when the compiler
+# version changes, we add `core.o` as a dependency (even if it is not needed).
+$(obj)/libmacros.so: $(src)/macros/lib.rs $(obj)/core.o FORCE
+	$(call if_changed_dep,rustc_procmacro)
+
+quiet_cmd_rustc_library = $(if $(skip_clippy),RUSTC,$(RUSTC_OR_CLIPPY_QUIET)) L $@
+      cmd_rustc_library = \
+	OBJTREE=$(abspath $(objtree)) \
+	$(if $(skip_clippy),$(RUSTC),$(RUSTC_OR_CLIPPY)) \
+		$(filter-out $(skip_flags),$(rust_flags) $(rustc_target_flags)) \
+		--emit=dep-info,obj,metadata --crate-type rlib \
+		--out-dir $(objtree)/$(obj) -L$(objtree)/$(obj) \
+		--crate-name $(patsubst %.o,%,$(notdir $@)) $<; \
+	mv $(objtree)/$(obj)/$(patsubst %.o,%,$(notdir $@)).d $(depfile); \
+	sed -i '/^\#/d' $(depfile) \
+	$(if $(rustc_objcopy),;$(OBJCOPY) $(rustc_objcopy) $@)
+
+rust-analyzer:
+	$(Q)$(srctree)/scripts/generate_rust_analyzer.py $(srctree) $(objtree) \
+		$(RUST_LIB_SRC) > $(objtree)/rust-project.json
+
+$(obj)/core.o: private skip_clippy = 1
+$(obj)/core.o: private skip_flags = -Dunreachable_pub
+$(obj)/core.o: private rustc_target_flags = $(core-cfgs)
+$(obj)/core.o: $(RUST_LIB_SRC)/core/src/lib.rs $(obj)/target.json FORCE
+	$(call if_changed_dep,rustc_library)
+
+$(obj)/compiler_builtins.o: private rustc_objcopy = -w -W '__*'
+$(obj)/compiler_builtins.o: $(src)/compiler_builtins.rs $(obj)/core.o FORCE
+	$(call if_changed_dep,rustc_library)
+
+$(obj)/alloc.o: private skip_clippy = 1
+$(obj)/alloc.o: private skip_flags = -Dunreachable_pub
+$(obj)/alloc.o: private rustc_target_flags = $(alloc-cfgs)
+$(obj)/alloc.o: $(src)/alloc/lib.rs $(obj)/compiler_builtins.o FORCE
+	$(call if_changed_dep,rustc_library)
+
+$(obj)/bindings.o: $(src)/bindings/lib.rs \
+    $(obj)/compiler_builtins.o \
+    $(obj)/bindings/bindings_generated.rs \
+    $(obj)/bindings/bindings_helpers_generated.rs FORCE
+	$(call if_changed_dep,rustc_library)
+
+$(obj)/kernel.o: private rustc_target_flags = --extern alloc \
+    --extern macros --extern bindings
+$(obj)/kernel.o: $(src)/kernel/lib.rs $(obj)/alloc.o \
+    $(obj)/libmacros.so $(obj)/bindings.o FORCE
+	$(call if_changed_dep,rustc_library)
+
+endif # CONFIG_RUST

rust/alloc/README.md

@@ -0,0 +1,33 @@
+# `alloc`
+
+These source files come from the Rust standard library, hosted in
+the <https://github.com/rust-lang/rust> repository, licensed under
+"Apache-2.0 OR MIT" and adapted for kernel use. For copyright details,
+see <https://github.com/rust-lang/rust/blob/master/COPYRIGHT>.
+
+Please note that these files should be kept as close as possible to
+upstream. In general, only additions should be performed (e.g. new
+methods). Eventually, changes should make it into upstream so that,
+at some point, this fork can be dropped from the kernel tree.
+
+
+## Rationale
+
+On one hand, kernel folks wanted to keep `alloc` in-tree to have more
+freedom in both workflow and actual features if actually needed
+(e.g. receiver types if we ended up using them), which is reasonable.
+
+On the other hand, Rust folks wanted to keep `alloc` as close as
+upstream as possible and avoid as much divergence as possible, which
+is also reasonable.
+
+We agreed on a middle-ground: we would keep a subset of `alloc`
+in-tree that would be as small and as close as possible to upstream.
+Then, upstream can start adding the functions that we add to `alloc`
+etc., until we reach a point where the kernel already knows exactly
+what it needs in `alloc` and all the new methods are merged into
+upstream, so that we can drop `alloc` from the kernel tree and go back
+to using the upstream one.
+
+By doing this, the kernel can go a bit faster now, and Rust can
+slowly incorporate and discuss the changes as needed.

rust/alloc/alloc.rs

@@ -0,0 +1,440 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+//! Memory allocation APIs
+
+#![stable(feature = "alloc_module", since = "1.28.0")]
+
+#[cfg(not(test))]
+use core::intrinsics;
+use core::intrinsics::{min_align_of_val, size_of_val};
+
+use core::ptr::Unique;
+#[cfg(not(test))]
+use core::ptr::{self, NonNull};
+
+#[stable(feature = "alloc_module", since = "1.28.0")]
+#[doc(inline)]
+pub use core::alloc::*;
+
+use core::marker::Destruct;
+
+#[cfg(test)]
+mod tests;
+
+extern "Rust" {
+    // These are the magic symbols to call the global allocator.  rustc generates
+    // them to call `__rg_alloc` etc. if there is a `#[global_allocator]` attribute
+    // (the code expanding that attribute macro generates those functions), or to call
+    // the default implementations in libstd (`__rdl_alloc` etc. in `library/std/src/alloc.rs`)
+    // otherwise.
+    // The rustc fork of LLVM also special-cases these function names to be able to optimize them
+    // like `malloc`, `realloc`, and `free`, respectively.
+    #[rustc_allocator]
+    #[rustc_allocator_nounwind]
+    fn __rust_alloc(size: usize, align: usize) -> *mut u8;
+    #[rustc_allocator_nounwind]
+    fn __rust_dealloc(ptr: *mut u8, size: usize, align: usize);
+    #[rustc_allocator_nounwind]
+    fn __rust_realloc(ptr: *mut u8, old_size: usize, align: usize, new_size: usize) -> *mut u8;
+    #[rustc_allocator_nounwind]
+    fn __rust_alloc_zeroed(size: usize, align: usize) -> *mut u8;
+}
+
+/// The global memory allocator.
+///
+/// This type implements the [`Allocator`] trait by forwarding calls
+/// to the allocator registered with the `#[global_allocator]` attribute
+/// if there is one, or the `std` crate’s default.
+///
+/// Note: while this type is unstable, the functionality it provides can be
+/// accessed through the [free functions in `alloc`](self#functions).
+#[unstable(feature = "allocator_api", issue = "32838")]
+#[derive(Copy, Clone, Default, Debug)]
+#[cfg(not(test))]
+pub struct Global;
+
+#[cfg(test)]
+pub use std::alloc::Global;
+
+/// Allocate memory with the global allocator.
+///
+/// This function forwards calls to the [`GlobalAlloc::alloc`] method
+/// of the allocator registered with the `#[global_allocator]` attribute
+/// if there is one, or the `std` crate’s default.
+///
+/// This function is expected to be deprecated in favor of the `alloc` method
+/// of the [`Global`] type when it and the [`Allocator`] trait become stable.
+///
+/// # Safety
+///
+/// See [`GlobalAlloc::alloc`].
+///
+/// # Examples
+///
+/// ```
+/// use std::alloc::{alloc, dealloc, Layout};
+///
+/// unsafe {
+///     let layout = Layout::new::<u16>();
+///     let ptr = alloc(layout);
+///
+///     *(ptr as *mut u16) = 42;
+///     assert_eq!(*(ptr as *mut u16), 42);
+///
+///     dealloc(ptr, layout);
+/// }
+/// ```
+#[stable(feature = "global_alloc", since = "1.28.0")]
+#[must_use = "losing the pointer will leak memory"]
+#[inline]
+pub unsafe fn alloc(layout: Layout) -> *mut u8 {
+    unsafe { __rust_alloc(layout.size(), layout.align()) }
+}
+
+/// Deallocate memory with the global allocator.
+///
+/// This function forwards calls to the [`GlobalAlloc::dealloc`] method
+/// of the allocator registered with the `#[global_allocator]` attribute
+/// if there is one, or the `std` crate’s default.
+///
+/// This function is expected to be deprecated in favor of the `dealloc` method
+/// of the [`Global`] type when it and the [`Allocator`] trait become stable.
+///
+/// # Safety
+///
+/// See [`GlobalAlloc::dealloc`].
+#[stable(feature = "global_alloc", since = "1.28.0")]
+#[inline]
+pub unsafe fn dealloc(ptr: *mut u8, layout: Layout) {
+    unsafe { __rust_dealloc(ptr, layout.size(), layout.align()) }
+}
+
+/// Reallocate memory with the global allocator.
+///
+/// This function forwards calls to the [`GlobalAlloc::realloc`] method
+/// of the allocator registered with the `#[global_allocator]` attribute
+/// if there is one, or the `std` crate’s default.
+///
+/// This function is expected to be deprecated in favor of the `realloc` method
+/// of the [`Global`] type when it and the [`Allocator`] trait become stable.
+///
+/// # Safety
+///
+/// See [`GlobalAlloc::realloc`].
+#[stable(feature = "global_alloc", since = "1.28.0")]
+#[must_use = "losing the pointer will leak memory"]
+#[inline]
+pub unsafe fn realloc(ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
+    unsafe { __rust_realloc(ptr, layout.size(), layout.align(), new_size) }
+}
+
+/// Allocate zero-initialized memory with the global allocator.
+///
+/// This function forwards calls to the [`GlobalAlloc::alloc_zeroed`] method
+/// of the allocator registered with the `#[global_allocator]` attribute
+/// if there is one, or the `std` crate’s default.
+///
+/// This function is expected to be deprecated in favor of the `alloc_zeroed` method
+/// of the [`Global`] type when it and the [`Allocator`] trait become stable.
+///
+/// # Safety
+///
+/// See [`GlobalAlloc::alloc_zeroed`].
+///
+/// # Examples
+///
+/// ```
+/// use std::alloc::{alloc_zeroed, dealloc, Layout};
+///
+/// unsafe {
+///     let layout = Layout::new::<u16>();
+///     let ptr = alloc_zeroed(layout);
+///
+///     assert_eq!(*(ptr as *mut u16), 0);
+///
+///     dealloc(ptr, layout);
+/// }
+/// ```
+#[stable(feature = "global_alloc", since = "1.28.0")]
+#[must_use = "losing the pointer will leak memory"]
+#[inline]
+pub unsafe fn alloc_zeroed(layout: Layout) -> *mut u8 {
+    unsafe { __rust_alloc_zeroed(layout.size(), layout.align()) }
+}
+
+#[cfg(not(test))]
+impl Global {
+    #[inline]
+    fn alloc_impl(&self, layout: Layout, zeroed: bool) -> Result<NonNull<[u8]>, AllocError> {
+        match layout.size() {
+            0 => Ok(NonNull::slice_from_raw_parts(layout.dangling(), 0)),
+            // SAFETY: `layout` is non-zero in size,
+            size => unsafe {
+                let raw_ptr = if zeroed { alloc_zeroed(layout) } else { alloc(layout) };
+                let ptr = NonNull::new(raw_ptr).ok_or(AllocError)?;
+                Ok(NonNull::slice_from_raw_parts(ptr, size))
+            },
+        }
+    }
+
+    // SAFETY: Same as `Allocator::grow`
+    #[inline]
+    unsafe fn grow_impl(
+        &self,
+        ptr: NonNull<u8>,
+        old_layout: Layout,
+        new_layout: Layout,
+        zeroed: bool,
+    ) -> Result<NonNull<[u8]>, AllocError> {
+        debug_assert!(
+            new_layout.size() >= old_layout.size(),
+            "`new_layout.size()` must be greater than or equal to `old_layout.size()`"
+        );
+
+        match old_layout.size() {
+            0 => self.alloc_impl(new_layout, zeroed),
+
+            // SAFETY: `new_size` is non-zero as `old_size` is greater than or equal to `new_size`
+            // as required by safety conditions. Other conditions must be upheld by the caller
+            old_size if old_layout.align() == new_layout.align() => unsafe {
+                let new_size = new_layout.size();
+
+                // `realloc` probably checks for `new_size >= old_layout.size()` or something similar.
+                intrinsics::assume(new_size >= old_layout.size());
+
+                let raw_ptr = realloc(ptr.as_ptr(), old_layout, new_size);
+                let ptr = NonNull::new(raw_ptr).ok_or(AllocError)?;
+                if zeroed {
+                    raw_ptr.add(old_size).write_bytes(0, new_size - old_size);
+                }
+                Ok(NonNull::slice_from_raw_parts(ptr, new_size))
+            },
+
+            // SAFETY: because `new_layout.size()` must be greater than or equal to `old_size`,
+            // both the old and new memory allocation are valid for reads and writes for `old_size`
+            // bytes. Also, because the old allocation wasn't yet deallocated, it cannot overlap
+            // `new_ptr`. Thus, the call to `copy_nonoverlapping` is safe. The safety contract
+            // for `dealloc` must be upheld by the caller.
+            old_size => unsafe {
+                let new_ptr = self.alloc_impl(new_layout, zeroed)?;
+                ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), old_size);
+                self.deallocate(ptr, old_layout);
+                Ok(new_ptr)
+            },
+        }
+    }
+}
+
+#[unstable(feature = "allocator_api", issue = "32838")]
+#[cfg(not(test))]
+unsafe impl Allocator for Global {
+    #[inline]
+    fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
+        self.alloc_impl(layout, false)
+    }
+
+    #[inline]
+    fn allocate_zeroed(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
+        self.alloc_impl(layout, true)
+    }
+
+    #[inline]
+    unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
+        if layout.size() != 0 {
+            // SAFETY: `layout` is non-zero in size,
+            // other conditions must be upheld by the caller
+            unsafe { dealloc(ptr.as_ptr(), layout) }
+        }
+    }
+
+    #[inline]
+    unsafe fn grow(
+        &self,
+        ptr: NonNull<u8>,
+        old_layout: Layout,
+        new_layout: Layout,
+    ) -> Result<NonNull<[u8]>, AllocError> {
+        // SAFETY: all conditions must be upheld by the caller
+        unsafe { self.grow_impl(ptr, old_layout, new_layout, false) }
+    }
+
+    #[inline]
+    unsafe fn grow_zeroed(
+        &self,
+        ptr: NonNull<u8>,
+        old_layout: Layout,
+        new_layout: Layout,
+    ) -> Result<NonNull<[u8]>, AllocError> {
+        // SAFETY: all conditions must be upheld by the caller
+        unsafe { self.grow_impl(ptr, old_layout, new_layout, true) }
+    }
+
+    #[inline]
+    unsafe fn shrink(
+        &self,
+        ptr: NonNull<u8>,
+        old_layout: Layout,
+        new_layout: Layout,
+    ) -> Result<NonNull<[u8]>, AllocError> {
+        debug_assert!(
+            new_layout.size() <= old_layout.size(),
+            "`new_layout.size()` must be smaller than or equal to `old_layout.size()`"
+        );
+
+        match new_layout.size() {
+            // SAFETY: conditions must be upheld by the caller
+            0 => unsafe {
+                self.deallocate(ptr, old_layout);
+                Ok(NonNull::slice_from_raw_parts(new_layout.dangling(), 0))
+            },
+
+            // SAFETY: `new_size` is non-zero. Other conditions must be upheld by the caller
+            new_size if old_layout.align() == new_layout.align() => unsafe {
+                // `realloc` probably checks for `new_size <= old_layout.size()` or something similar.
+                intrinsics::assume(new_size <= old_layout.size());
+
+                let raw_ptr = realloc(ptr.as_ptr(), old_layout, new_size);
+                let ptr = NonNull::new(raw_ptr).ok_or(AllocError)?;
+                Ok(NonNull::slice_from_raw_parts(ptr, new_size))
+            },
+
+            // SAFETY: because `new_size` must be smaller than or equal to `old_layout.size()`,
+            // both the old and new memory allocation are valid for reads and writes for `new_size`
+            // bytes. Also, because the old allocation wasn't yet deallocated, it cannot overlap
+            // `new_ptr`. Thus, the call to `copy_nonoverlapping` is safe. The safety contract
+            // for `dealloc` must be upheld by the caller.
+            new_size => unsafe {
+                let new_ptr = self.allocate(new_layout)?;
+                ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), new_size);
+                self.deallocate(ptr, old_layout);
+                Ok(new_ptr)
+            },
+        }
+    }
+}
+
+/// The allocator for unique pointers.
+#[cfg(all(not(no_global_oom_handling), not(test)))]
+#[lang = "exchange_malloc"]
+#[inline]
+unsafe fn exchange_malloc(size: usize, align: usize) -> *mut u8 {
+    let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
+    match Global.allocate(layout) {
+        Ok(ptr) => ptr.as_mut_ptr(),
+        Err(_) => handle_alloc_error(layout),
+    }
+}
+
+#[cfg_attr(not(test), lang = "box_free")]
+#[inline]
+#[rustc_const_unstable(feature = "const_box", issue = "92521")]
+// This signature has to be the same as `Box`, otherwise an ICE will happen.
+// When an additional parameter to `Box` is added (like `A: Allocator`), this has to be added here as
+// well.
+// For example if `Box` is changed to  `struct Box<T: ?Sized, A: Allocator>(Unique<T>, A)`,
+// this function has to be changed to `fn box_free<T: ?Sized, A: Allocator>(Unique<T>, A)` as well.
+pub(crate) const unsafe fn box_free<T: ?Sized, A: ~const Allocator + ~const Destruct>(
+    ptr: Unique<T>,
+    alloc: A,
+) {
+    unsafe {
+        let size = size_of_val(ptr.as_ref());
+        let align = min_align_of_val(ptr.as_ref());
+        let layout = Layout::from_size_align_unchecked(size, align);
+        alloc.deallocate(From::from(ptr.cast()), layout)
+    }
+}
+
+// # Allocation error handler
+
+#[cfg(not(no_global_oom_handling))]
+extern "Rust" {
+    // This is the magic symbol to call the global alloc error handler.  rustc generates
+    // it to call `__rg_oom` if there is a `#[alloc_error_handler]`, or to call the
+    // default implementations below (`__rdl_oom`) otherwise.
+    fn __rust_alloc_error_handler(size: usize, align: usize) -> !;
+}
+
+/// Abort on memory allocation error or failure.
+///
+/// Callers of memory allocation APIs wishing to abort computation
+/// in response to an allocation error are encouraged to call this function,
+/// rather than directly invoking `panic!` or similar.
+///
+/// The default behavior of this function is to print a message to standard error
+/// and abort the process.
+/// It can be replaced with [`set_alloc_error_hook`] and [`take_alloc_error_hook`].
+///
+/// [`set_alloc_error_hook`]: ../../std/alloc/fn.set_alloc_error_hook.html
+/// [`take_alloc_error_hook`]: ../../std/alloc/fn.take_alloc_error_hook.html
+#[stable(feature = "global_alloc", since = "1.28.0")]
+#[rustc_const_unstable(feature = "const_alloc_error", issue = "92523")]
+#[cfg(all(not(no_global_oom_handling), not(test)))]
+#[cold]
+pub const fn handle_alloc_error(layout: Layout) -> ! {
+    const fn ct_error(_: Layout) -> ! {
+        panic!("allocation failed");
+    }
+
+    fn rt_error(layout: Layout) -> ! {
+        unsafe {
+            __rust_alloc_error_handler(layout.size(), layout.align());
+        }
+    }
+
+    unsafe { core::intrinsics::const_eval_select((layout,), ct_error, rt_error) }
+}
+
+// For alloc test `std::alloc::handle_alloc_error` can be used directly.
+#[cfg(all(not(no_global_oom_handling), test))]
+pub use std::alloc::handle_alloc_error;
+
+#[cfg(all(not(no_global_oom_handling), not(test)))]
+#[doc(hidden)]
+#[allow(unused_attributes)]
+#[unstable(feature = "alloc_internals", issue = "none")]
+pub mod __alloc_error_handler {
+    use crate::alloc::Layout;
+
+    // called via generated `__rust_alloc_error_handler`
+
+    // if there is no `#[alloc_error_handler]`
+    #[rustc_std_internal_symbol]
+    pub unsafe extern "C-unwind" fn __rdl_oom(size: usize, _align: usize) -> ! {
+        panic!("memory allocation of {size} bytes failed")
+    }
+
+    // if there is an `#[alloc_error_handler]`
+    #[rustc_std_internal_symbol]
+    pub unsafe extern "C-unwind" fn __rg_oom(size: usize, align: usize) -> ! {
+        let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
+        extern "Rust" {
+            #[lang = "oom"]
+            fn oom_impl(layout: Layout) -> !;
+        }
+        unsafe { oom_impl(layout) }
+    }
+}
+
+/// Specialize clones into pre-allocated, uninitialized memory.
+/// Used by `Box::clone` and `Rc`/`Arc::make_mut`.
+pub(crate) trait WriteCloneIntoRaw: Sized {
+    unsafe fn write_clone_into_raw(&self, target: *mut Self);
+}
+
+impl<T: Clone> WriteCloneIntoRaw for T {
+    #[inline]
+    default unsafe fn write_clone_into_raw(&self, target: *mut Self) {
+        // Having allocated *first* may allow the optimizer to create
+        // the cloned value in-place, skipping the local and move.
+        unsafe { target.write(self.clone()) };
+    }
+}
+
+impl<T: Copy> WriteCloneIntoRaw for T {
+    #[inline]
+    unsafe fn write_clone_into_raw(&self, target: *mut Self) {
+        // We can always copy in-place, without ever involving a local value.
+        unsafe { target.copy_from_nonoverlapping(self, 1) };
+    }
+}

rust/alloc/borrow.rs

@@ -0,0 +1,498 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+//! A module for working with borrowed data.
+
+#![stable(feature = "rust1", since = "1.0.0")]
+
+use core::cmp::Ordering;
+use core::hash::{Hash, Hasher};
+use core::ops::Deref;
+#[cfg(not(no_global_oom_handling))]
+use core::ops::{Add, AddAssign};
+
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::borrow::{Borrow, BorrowMut};
+
+use core::fmt;
+#[cfg(not(no_global_oom_handling))]
+use crate::string::String;
+
+use Cow::*;
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, B: ?Sized> Borrow<B> for Cow<'a, B>
+where
+    B: ToOwned,
+    <B as ToOwned>::Owned: 'a,
+{
+    fn borrow(&self) -> &B {
+        &**self
+    }
+}
+
+/// A generalization of `Clone` to borrowed data.
+///
+/// Some types make it possible to go from borrowed to owned, usually by
+/// implementing the `Clone` trait. But `Clone` works only for going from `&T`
+/// to `T`. The `ToOwned` trait generalizes `Clone` to construct owned data
+/// from any borrow of a given type.
+#[cfg_attr(not(test), rustc_diagnostic_item = "ToOwned")]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub trait ToOwned {
+    /// The resulting type after obtaining ownership.
+    #[stable(feature = "rust1", since = "1.0.0")]
+    type Owned: Borrow<Self>;
+
+    /// Creates owned data from borrowed data, usually by cloning.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let s: &str = "a";
+    /// let ss: String = s.to_owned();
+    ///
+    /// let v: &[i32] = &[1, 2];
+    /// let vv: Vec<i32> = v.to_owned();
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    #[must_use = "cloning is often expensive and is not expected to have side effects"]
+    fn to_owned(&self) -> Self::Owned;
+
+    /// Uses borrowed data to replace owned data, usually by cloning.
+    ///
+    /// This is borrow-generalized version of `Clone::clone_from`.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// # #![feature(toowned_clone_into)]
+    /// let mut s: String = String::new();
+    /// "hello".clone_into(&mut s);
+    ///
+    /// let mut v: Vec<i32> = Vec::new();
+    /// [1, 2][..].clone_into(&mut v);
+    /// ```
+    #[unstable(feature = "toowned_clone_into", reason = "recently added", issue = "41263")]
+    fn clone_into(&self, target: &mut Self::Owned) {
+        *target = self.to_owned();
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> ToOwned for T
+where
+    T: Clone,
+{
+    type Owned = T;
+    fn to_owned(&self) -> T {
+        self.clone()
+    }
+
+    fn clone_into(&self, target: &mut T) {
+        target.clone_from(self);
+    }
+}
+
+/// A clone-on-write smart pointer.
+///
+/// The type `Cow` is a smart pointer providing clone-on-write functionality: it
+/// can enclose and provide immutable access to borrowed data, and clone the
+/// data lazily when mutation or ownership is required. The type is designed to
+/// work with general borrowed data via the `Borrow` trait.
+///
+/// `Cow` implements `Deref`, which means that you can call
+/// non-mutating methods directly on the data it encloses. If mutation
+/// is desired, `to_mut` will obtain a mutable reference to an owned
+/// value, cloning if necessary.
+///
+/// If you need reference-counting pointers, note that
+/// [`Rc::make_mut`][crate::rc::Rc::make_mut] and
+/// [`Arc::make_mut`][crate::sync::Arc::make_mut] can provide clone-on-write
+/// functionality as well.
+///
+/// # Examples
+///
+/// ```
+/// use std::borrow::Cow;
+///
+/// fn abs_all(input: &mut Cow<[i32]>) {
+///     for i in 0..input.len() {
+///         let v = input[i];
+///         if v < 0 {
+///             // Clones into a vector if not already owned.
+///             input.to_mut()[i] = -v;
+///         }
+///     }
+/// }
+///
+/// // No clone occurs because `input` doesn't need to be mutated.
+/// let slice = [0, 1, 2];
+/// let mut input = Cow::from(&slice[..]);
+/// abs_all(&mut input);
+///
+/// // Clone occurs because `input` needs to be mutated.
+/// let slice = [-1, 0, 1];
+/// let mut input = Cow::from(&slice[..]);
+/// abs_all(&mut input);
+///
+/// // No clone occurs because `input` is already owned.
+/// let mut input = Cow::from(vec![-1, 0, 1]);
+/// abs_all(&mut input);
+/// ```
+///
+/// Another example showing how to keep `Cow` in a struct:
+///
+/// ```
+/// use std::borrow::Cow;
+///
+/// struct Items<'a, X: 'a> where [X]: ToOwned<Owned = Vec<X>> {
+///     values: Cow<'a, [X]>,
+/// }
+///
+/// impl<'a, X: Clone + 'a> Items<'a, X> where [X]: ToOwned<Owned = Vec<X>> {
+///     fn new(v: Cow<'a, [X]>) -> Self {
+///         Items { values: v }
+///     }
+/// }
+///
+/// // Creates a container from borrowed values of a slice
+/// let readonly = [1, 2];
+/// let borrowed = Items::new((&readonly[..]).into());
+/// match borrowed {
+///     Items { values: Cow::Borrowed(b) } => println!("borrowed {b:?}"),
+///     _ => panic!("expect borrowed value"),
+/// }
+///
+/// let mut clone_on_write = borrowed;
+/// // Mutates the data from slice into owned vec and pushes a new value on top
+/// clone_on_write.values.to_mut().push(3);
+/// println!("clone_on_write = {:?}", clone_on_write.values);
+///
+/// // The data was mutated. Let's check it out.
+/// match clone_on_write {
+///     Items { values: Cow::Owned(_) } => println!("clone_on_write contains owned data"),
+///     _ => panic!("expect owned data"),
+/// }
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "Cow")]
+pub enum Cow<'a, B: ?Sized + 'a>
+where
+    B: ToOwned,
+{
+    /// Borrowed data.
+    #[stable(feature = "rust1", since = "1.0.0")]
+    Borrowed(#[stable(feature = "rust1", since = "1.0.0")] &'a B),
+
+    /// Owned data.
+    #[stable(feature = "rust1", since = "1.0.0")]
+    Owned(#[stable(feature = "rust1", since = "1.0.0")] <B as ToOwned>::Owned),
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<B: ?Sized + ToOwned> Clone for Cow<'_, B> {
+    fn clone(&self) -> Self {
+        match *self {
+            Borrowed(b) => Borrowed(b),
+            Owned(ref o) => {
+                let b: &B = o.borrow();
+                Owned(b.to_owned())
+            }
+        }
+    }
+
+    fn clone_from(&mut self, source: &Self) {
+        match (self, source) {
+            (&mut Owned(ref mut dest), &Owned(ref o)) => o.borrow().clone_into(dest),
+            (t, s) => *t = s.clone(),
+        }
+    }
+}
+
+impl<B: ?Sized + ToOwned> Cow<'_, B> {
+    /// Returns true if the data is borrowed, i.e. if `to_mut` would require additional work.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(cow_is_borrowed)]
+    /// use std::borrow::Cow;
+    ///
+    /// let cow = Cow::Borrowed("moo");
+    /// assert!(cow.is_borrowed());
+    ///
+    /// let bull: Cow<'_, str> = Cow::Owned("...moo?".to_string());
+    /// assert!(!bull.is_borrowed());
+    /// ```
+    #[unstable(feature = "cow_is_borrowed", issue = "65143")]
+    #[rustc_const_unstable(feature = "const_cow_is_borrowed", issue = "65143")]
+    pub const fn is_borrowed(&self) -> bool {
+        match *self {
+            Borrowed(_) => true,
+            Owned(_) => false,
+        }
+    }
+
+    /// Returns true if the data is owned, i.e. if `to_mut` would be a no-op.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(cow_is_borrowed)]
+    /// use std::borrow::Cow;
+    ///
+    /// let cow: Cow<'_, str> = Cow::Owned("moo".to_string());
+    /// assert!(cow.is_owned());
+    ///
+    /// let bull = Cow::Borrowed("...moo?");
+    /// assert!(!bull.is_owned());
+    /// ```
+    #[unstable(feature = "cow_is_borrowed", issue = "65143")]
+    #[rustc_const_unstable(feature = "const_cow_is_borrowed", issue = "65143")]
+    pub const fn is_owned(&self) -> bool {
+        !self.is_borrowed()
+    }
+
+    /// Acquires a mutable reference to the owned form of the data.
+    ///
+    /// Clones the data if it is not already owned.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::borrow::Cow;
+    ///
+    /// let mut cow = Cow::Borrowed("foo");
+    /// cow.to_mut().make_ascii_uppercase();
+    ///
+    /// assert_eq!(
+    ///   cow,
+    ///   Cow::Owned(String::from("FOO")) as Cow<str>
+    /// );
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn to_mut(&mut self) -> &mut <B as ToOwned>::Owned {
+        match *self {
+            Borrowed(borrowed) => {
+                *self = Owned(borrowed.to_owned());
+                match *self {
+                    Borrowed(..) => unreachable!(),
+                    Owned(ref mut owned) => owned,
+                }
+            }
+            Owned(ref mut owned) => owned,
+        }
+    }
+
+    /// Extracts the owned data.
+    ///
+    /// Clones the data if it is not already owned.
+    ///
+    /// # Examples
+    ///
+    /// Calling `into_owned` on a `Cow::Borrowed` returns a clone of the borrowed data:
+    ///
+    /// ```
+    /// use std::borrow::Cow;
+    ///
+    /// let s = "Hello world!";
+    /// let cow = Cow::Borrowed(s);
+    ///
+    /// assert_eq!(
+    ///   cow.into_owned(),
+    ///   String::from(s)
+    /// );
+    /// ```
+    ///
+    /// Calling `into_owned` on a `Cow::Owned` returns the owned data. The data is moved out of the
+    /// `Cow` without being cloned.
+    ///
+    /// ```
+    /// use std::borrow::Cow;
+    ///
+    /// let s = "Hello world!";
+    /// let cow: Cow<str> = Cow::Owned(String::from(s));
+    ///
+    /// assert_eq!(
+    ///   cow.into_owned(),
+    ///   String::from(s)
+    /// );
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn into_owned(self) -> <B as ToOwned>::Owned {
+        match self {
+            Borrowed(borrowed) => borrowed.to_owned(),
+            Owned(owned) => owned,
+        }
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_const_unstable(feature = "const_deref", issue = "88955")]
+impl<B: ?Sized + ToOwned> const Deref for Cow<'_, B>
+where
+    B::Owned: ~const Borrow<B>,
+{
+    type Target = B;
+
+    fn deref(&self) -> &B {
+        match *self {
+            Borrowed(borrowed) => borrowed,
+            Owned(ref owned) => owned.borrow(),
+        }
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<B: ?Sized> Eq for Cow<'_, B> where B: Eq + ToOwned {}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<B: ?Sized> Ord for Cow<'_, B>
+where
+    B: Ord + ToOwned,
+{
+    #[inline]
+    fn cmp(&self, other: &Self) -> Ordering {
+        Ord::cmp(&**self, &**other)
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, 'b, B: ?Sized, C: ?Sized> PartialEq<Cow<'b, C>> for Cow<'a, B>
+where
+    B: PartialEq<C> + ToOwned,
+    C: ToOwned,
+{
+    #[inline]
+    fn eq(&self, other: &Cow<'b, C>) -> bool {
+        PartialEq::eq(&**self, &**other)
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, B: ?Sized> PartialOrd for Cow<'a, B>
+where
+    B: PartialOrd + ToOwned,
+{
+    #[inline]
+    fn partial_cmp(&self, other: &Cow<'a, B>) -> Option<Ordering> {
+        PartialOrd::partial_cmp(&**self, &**other)
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<B: ?Sized> fmt::Debug for Cow<'_, B>
+where
+    B: fmt::Debug + ToOwned<Owned: fmt::Debug>,
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            Borrowed(ref b) => fmt::Debug::fmt(b, f),
+            Owned(ref o) => fmt::Debug::fmt(o, f),
+        }
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<B: ?Sized> fmt::Display for Cow<'_, B>
+where
+    B: fmt::Display + ToOwned<Owned: fmt::Display>,
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            Borrowed(ref b) => fmt::Display::fmt(b, f),
+            Owned(ref o) => fmt::Display::fmt(o, f),
+        }
+    }
+}
+
+#[stable(feature = "default", since = "1.11.0")]
+impl<B: ?Sized> Default for Cow<'_, B>
+where
+    B: ToOwned<Owned: Default>,
+{
+    /// Creates an owned Cow<'a, B> with the default value for the contained owned value.
+    fn default() -> Self {
+        Owned(<B as ToOwned>::Owned::default())
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<B: ?Sized> Hash for Cow<'_, B>
+where
+    B: Hash + ToOwned,
+{
+    #[inline]
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        Hash::hash(&**self, state)
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + ToOwned> AsRef<T> for Cow<'_, T> {
+    fn as_ref(&self) -> &T {
+        self
+    }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "cow_add", since = "1.14.0")]
+impl<'a> Add<&'a str> for Cow<'a, str> {
+    type Output = Cow<'a, str>;
+
+    #[inline]
+    fn add(mut self, rhs: &'a str) -> Self::Output {
+        self += rhs;
+        self
+    }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "cow_add", since = "1.14.0")]
+impl<'a> Add<Cow<'a, str>> for Cow<'a, str> {
+    type Output = Cow<'a, str>;
+
+    #[inline]
+    fn add(mut self, rhs: Cow<'a, str>) -> Self::Output {
+        self += rhs;
+        self
+    }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "cow_add", since = "1.14.0")]
+impl<'a> AddAssign<&'a str> for Cow<'a, str> {
+    fn add_assign(&mut self, rhs: &'a str) {
+        if self.is_empty() {
+            *self = Cow::Borrowed(rhs)
+        } else if !rhs.is_empty() {
+            if let Cow::Borrowed(lhs) = *self {
+                let mut s = String::with_capacity(lhs.len() + rhs.len());
+                s.push_str(lhs);
+                *self = Cow::Owned(s);
+            }
+            self.to_mut().push_str(rhs);
+        }
+    }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "cow_add", since = "1.14.0")]
+impl<'a> AddAssign<Cow<'a, str>> for Cow<'a, str> {
+    fn add_assign(&mut self, rhs: Cow<'a, str>) {
+        if self.is_empty() {
+            *self = rhs
+        } else if !rhs.is_empty() {
+            if let Cow::Borrowed(lhs) = *self {
+                let mut s = String::with_capacity(lhs.len() + rhs.len());
+                s.push_str(lhs);
+                *self = Cow::Owned(s);
+            }
+            self.to_mut().push_str(&rhs);
+        }
+    }
+}

rust/alloc/collections/mod.rs

@@ -0,0 +1,156 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+//! Collection types.
+
+#![stable(feature = "rust1", since = "1.0.0")]
+
+#[cfg(not(no_global_oom_handling))]
+pub mod binary_heap;
+#[cfg(not(no_global_oom_handling))]
+mod btree;
+#[cfg(not(no_global_oom_handling))]
+pub mod linked_list;
+#[cfg(not(no_global_oom_handling))]
+pub mod vec_deque;
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub mod btree_map {
+    //! An ordered map based on a B-Tree.
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub use super::btree::map::*;
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub mod btree_set {
+    //! An ordered set based on a B-Tree.
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub use super::btree::set::*;
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+#[doc(no_inline)]
+pub use binary_heap::BinaryHeap;
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+#[doc(no_inline)]
+pub use btree_map::BTreeMap;
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+#[doc(no_inline)]
+pub use btree_set::BTreeSet;
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+#[doc(no_inline)]
+pub use linked_list::LinkedList;
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+#[doc(no_inline)]
+pub use vec_deque::VecDeque;
+
+use crate::alloc::{Layout, LayoutError};
+use core::fmt::Display;
+
+/// The error type for `try_reserve` methods.
+#[derive(Clone, PartialEq, Eq, Debug)]
+#[stable(feature = "try_reserve", since = "1.57.0")]
+pub struct TryReserveError {
+    kind: TryReserveErrorKind,
+}
+
+impl TryReserveError {
+    /// Details about the allocation that caused the error
+    #[inline]
+    #[must_use]
+    #[unstable(
+        feature = "try_reserve_kind",
+        reason = "Uncertain how much info should be exposed",
+        issue = "48043"
+    )]
+    pub fn kind(&self) -> TryReserveErrorKind {
+        self.kind.clone()
+    }
+}
+
+/// Details of the allocation that caused a `TryReserveError`
+#[derive(Clone, PartialEq, Eq, Debug)]
+#[unstable(
+    feature = "try_reserve_kind",
+    reason = "Uncertain how much info should be exposed",
+    issue = "48043"
+)]
+pub enum TryReserveErrorKind {
+    /// Error due to the computed capacity exceeding the collection's maximum
+    /// (usually `isize::MAX` bytes).
+    CapacityOverflow,
+
+    /// The memory allocator returned an error
+    AllocError {
+        /// The layout of allocation request that failed
+        layout: Layout,
+
+        #[doc(hidden)]
+        #[unstable(
+            feature = "container_error_extra",
+            issue = "none",
+            reason = "\
+            Enable exposing the allocator’s custom error value \
+            if an associated type is added in the future: \
+            https://github.com/rust-lang/wg-allocators/issues/23"
+        )]
+        non_exhaustive: (),
+    },
+}
+
+#[unstable(
+    feature = "try_reserve_kind",
+    reason = "Uncertain how much info should be exposed",
+    issue = "48043"
+)]
+impl From<TryReserveErrorKind> for TryReserveError {
+    #[inline]
+    fn from(kind: TryReserveErrorKind) -> Self {
+        Self { kind }
+    }
+}
+
+#[unstable(feature = "try_reserve_kind", reason = "new API", issue = "48043")]
+impl From<LayoutError> for TryReserveErrorKind {
+    /// Always evaluates to [`TryReserveErrorKind::CapacityOverflow`].
+    #[inline]
+    fn from(_: LayoutError) -> Self {
+        TryReserveErrorKind::CapacityOverflow
+    }
+}
+
+#[stable(feature = "try_reserve", since = "1.57.0")]
+impl Display for TryReserveError {
+    fn fmt(
+        &self,
+        fmt: &mut core::fmt::Formatter<'_>,
+    ) -> core::result::Result<(), core::fmt::Error> {
+        fmt.write_str("memory allocation failed")?;
+        let reason = match self.kind {
+            TryReserveErrorKind::CapacityOverflow => {
+                " because the computed capacity exceeded the collection's maximum"
+            }
+            TryReserveErrorKind::AllocError { .. } => {
+                " because the memory allocator returned a error"
+            }
+        };
+        fmt.write_str(reason)
+    }
+}
+
+/// An intermediate trait for specialization of `Extend`.
+#[doc(hidden)]
+trait SpecExtend<I: IntoIterator> {
+    /// Extends `self` with the contents of the given iterator.
+    fn spec_extend(&mut self, iter: I);
+}

rust/alloc/lib.rs

@@ -0,0 +1,244 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+//! # The Rust core allocation and collections library
+//!
+//! This library provides smart pointers and collections for managing
+//! heap-allocated values.
+//!
+//! This library, like libcore, normally doesn’t need to be used directly
+//! since its contents are re-exported in the [`std` crate](../std/index.html).
+//! Crates that use the `#![no_std]` attribute however will typically
+//! not depend on `std`, so they’d use this crate instead.
+//!
+//! ## Boxed values
+//!
+//! The [`Box`] type is a smart pointer type. There can only be one owner of a
+//! [`Box`], and the owner can decide to mutate the contents, which live on the
+//! heap.
+//!
+//! This type can be sent among threads efficiently as the size of a `Box` value
+//! is the same as that of a pointer. Tree-like data structures are often built
+//! with boxes because each node often has only one owner, the parent.
+//!
+//! ## Reference counted pointers
+//!
+//! The [`Rc`] type is a non-threadsafe reference-counted pointer type intended
+//! for sharing memory within a thread. An [`Rc`] pointer wraps a type, `T`, and
+//! only allows access to `&T`, a shared reference.
+//!
+//! This type is useful when inherited mutability (such as using [`Box`]) is too
+//! constraining for an application, and is often paired with the [`Cell`] or
+//! [`RefCell`] types in order to allow mutation.
+//!
+//! ## Atomically reference counted pointers
+//!
+//! The [`Arc`] type is the threadsafe equivalent of the [`Rc`] type. It
+//! provides all the same functionality of [`Rc`], except it requires that the
+//! contained type `T` is shareable. Additionally, [`Arc<T>`][`Arc`] is itself
+//! sendable while [`Rc<T>`][`Rc`] is not.
+//!
+//! This type allows for shared access to the contained data, and is often
+//! paired with synchronization primitives such as mutexes to allow mutation of
+//! shared resources.
+//!
+//! ## Collections
+//!
+//! Implementations of the most common general purpose data structures are
+//! defined in this library. They are re-exported through the
+//! [standard collections library](../std/collections/index.html).
+//!
+//! ## Heap interfaces
+//!
+//! The [`alloc`](alloc/index.html) module defines the low-level interface to the
+//! default global allocator. It is not compatible with the libc allocator API.
+//!
+//! [`Arc`]: sync
+//! [`Box`]: boxed
+//! [`Cell`]: core::cell
+//! [`Rc`]: rc
+//! [`RefCell`]: core::cell
+
+// To run liballoc tests without x.py without ending up with two copies of liballoc, Miri needs to be
+// able to "empty" this crate. See <https://github.com/rust-lang/miri-test-libstd/issues/4>.
+// rustc itself never sets the feature, so this line has no affect there.
+#![cfg(any(not(feature = "miri-test-libstd"), test, doctest))]
+#![allow(unused_attributes)]
+#![stable(feature = "alloc", since = "1.36.0")]
+#![doc(
+    html_playground_url = "https://play.rust-lang.org/",
+    issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/",
+    test(no_crate_inject, attr(allow(unused_variables), deny(warnings)))
+)]
+#![doc(cfg_hide(
+    not(test),
+    not(any(test, bootstrap)),
+    any(not(feature = "miri-test-libstd"), test, doctest),
+    no_global_oom_handling,
+    not(no_global_oom_handling),
+    target_has_atomic = "ptr"
+))]
+#![no_std]
+#![needs_allocator]
+//
+// Lints:
+#![deny(unsafe_op_in_unsafe_fn)]
+#![warn(deprecated_in_future)]
+#![warn(missing_debug_implementations)]
+#![warn(missing_docs)]
+#![allow(explicit_outlives_requirements)]
+//
+// Library features:
+#![cfg_attr(not(no_global_oom_handling), feature(alloc_c_string))]
+#![feature(alloc_layout_extra)]
+#![feature(allocator_api)]
+#![feature(array_chunks)]
+#![feature(array_methods)]
+#![feature(array_windows)]
+#![feature(assert_matches)]
+#![feature(async_iterator)]
+#![feature(coerce_unsized)]
+#![cfg_attr(not(no_global_oom_handling), feature(const_alloc_error))]
+#![feature(const_box)]
+#![cfg_attr(not(no_global_oom_handling), feature(const_btree_new))]
+#![feature(const_cow_is_borrowed)]
+#![feature(const_convert)]
+#![feature(const_size_of_val)]
+#![feature(const_align_of_val)]
+#![feature(const_ptr_read)]
+#![feature(const_maybe_uninit_write)]
+#![feature(const_maybe_uninit_as_mut_ptr)]
+#![feature(const_refs_to_cell)]
+#![feature(core_c_str)]
+#![feature(core_intrinsics)]
+#![feature(core_ffi_c)]
+#![feature(const_eval_select)]
+#![feature(const_pin)]
+#![feature(cstr_from_bytes_until_nul)]
+#![feature(dispatch_from_dyn)]
+#![feature(exact_size_is_empty)]
+#![feature(extend_one)]
+#![feature(fmt_internals)]
+#![feature(fn_traits)]
+#![feature(hasher_prefixfree_extras)]
+#![feature(inplace_iteration)]
+#![feature(iter_advance_by)]
+#![feature(layout_for_ptr)]
+#![feature(maybe_uninit_slice)]
+#![cfg_attr(test, feature(new_uninit))]
+#![feature(nonnull_slice_from_raw_parts)]
+#![feature(pattern)]
+#![feature(ptr_internals)]
+#![feature(ptr_metadata)]
+#![feature(ptr_sub_ptr)]
+#![feature(receiver_trait)]
+#![feature(set_ptr_value)]
+#![feature(slice_group_by)]
+#![feature(slice_ptr_get)]
+#![feature(slice_ptr_len)]
+#![feature(slice_range)]
+#![feature(str_internals)]
+#![feature(strict_provenance)]
+#![feature(trusted_len)]
+#![feature(trusted_random_access)]
+#![feature(try_trait_v2)]
+#![feature(unchecked_math)]
+#![feature(unicode_internals)]
+#![feature(unsize)]
+//
+// Language features:
+#![feature(allocator_internals)]
+#![feature(allow_internal_unstable)]
+#![feature(associated_type_bounds)]
+#![feature(box_syntax)]
+#![feature(cfg_sanitize)]
+#![feature(const_deref)]
+#![feature(const_mut_refs)]
+#![feature(const_ptr_write)]
+#![feature(const_precise_live_drops)]
+#![feature(const_trait_impl)]
+#![feature(const_try)]
+#![feature(dropck_eyepatch)]
+#![feature(exclusive_range_pattern)]
+#![feature(fundamental)]
+#![cfg_attr(not(test), feature(generator_trait))]
+#![feature(hashmap_internals)]
+#![feature(lang_items)]
+#![feature(let_else)]
+#![feature(min_specialization)]
+#![feature(negative_impls)]
+#![feature(never_type)]
+#![feature(nll)] // Not necessary, but here to test the `nll` feature.
+#![feature(rustc_allow_const_fn_unstable)]
+#![feature(rustc_attrs)]
+#![feature(slice_internals)]
+#![feature(staged_api)]
+#![cfg_attr(test, feature(test))]
+#![feature(unboxed_closures)]
+#![feature(unsized_fn_params)]
+#![feature(c_unwind)]
+//
+// Rustdoc features:
+#![feature(doc_cfg)]
+#![feature(doc_cfg_hide)]
+// Technically, this is a bug in rustdoc: rustdoc sees the documentation on `#[lang = slice_alloc]`
+// blocks is for `&[T]`, which also has documentation using this feature in `core`, and gets mad
+// that the feature-gate isn't enabled. Ideally, it wouldn't check for the feature gate for docs
+// from other crates, but since this can only appear for lang items, it doesn't seem worth fixing.
+#![feature(intra_doc_pointers)]
+
+// Allow testing this library
+#[cfg(test)]
+#[macro_use]
+extern crate std;
+#[cfg(test)]
+extern crate test;
+
+// Module with internal macros used by other modules (needs to be included before other modules).
+#[cfg(not(no_macros))]
+#[macro_use]
+mod macros;
+
+mod raw_vec;
+
+// Heaps provided for low-level allocation strategies
+
+pub mod alloc;
+
+// Primitive types using the heaps above
+
+// Need to conditionally define the mod from `boxed.rs` to avoid
+// duplicating the lang-items when building in test cfg; but also need
+// to allow code to have `use boxed::Box;` declarations.
+#[cfg(not(test))]
+pub mod boxed;
+#[cfg(test)]
+mod boxed {
+    pub use std::boxed::Box;
+}
+pub mod borrow;
+pub mod collections;
+#[cfg(not(no_global_oom_handling))]
+pub mod ffi;
+#[cfg(not(no_fmt))]
+pub mod fmt;
+#[cfg(not(no_rc))]
+pub mod rc;
+pub mod slice;
+#[cfg(not(no_str))]
+pub mod str;
+#[cfg(not(no_string))]
+pub mod string;
+#[cfg(not(no_sync))]
+#[cfg(target_has_atomic = "ptr")]
+pub mod sync;
+#[cfg(all(not(no_global_oom_handling), target_has_atomic = "ptr"))]
+pub mod task;
+#[cfg(test)]
+mod tests;
+pub mod vec;
+
+#[doc(hidden)]
+#[unstable(feature = "liballoc_internals", issue = "none", reason = "implementation detail")]
+pub mod __export {
+    pub use core::format_args;
+}

rust/alloc/raw_vec.rs

@@ -0,0 +1,527 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+#![unstable(feature = "raw_vec_internals", reason = "unstable const warnings", issue = "none")]
+
+use core::alloc::LayoutError;
+use core::cmp;
+use core::intrinsics;
+use core::mem::{self, ManuallyDrop, MaybeUninit};
+use core::ops::Drop;
+use core::ptr::{self, NonNull, Unique};
+use core::slice;
+
+#[cfg(not(no_global_oom_handling))]
+use crate::alloc::handle_alloc_error;
+use crate::alloc::{Allocator, Global, Layout};
+use crate::boxed::Box;
+use crate::collections::TryReserveError;
+use crate::collections::TryReserveErrorKind::*;
+
+#[cfg(test)]
+mod tests;
+
+#[cfg(not(no_global_oom_handling))]
+enum AllocInit {
+    /// The contents of the new memory are uninitialized.
+    Uninitialized,
+    /// The new memory is guaranteed to be zeroed.
+    Zeroed,
+}
+
+/// A low-level utility for more ergonomically allocating, reallocating, and deallocating
+/// a buffer of memory on the heap without having to worry about all the corner cases
+/// involved. This type is excellent for building your own data structures like Vec and VecDeque.
+/// In particular:
+///
+/// * Produces `Unique::dangling()` on zero-sized types.
+/// * Produces `Unique::dangling()` on zero-length allocations.
+/// * Avoids freeing `Unique::dangling()`.
+/// * Catches all overflows in capacity computations (promotes them to "capacity overflow" panics).
+/// * Guards against 32-bit systems allocating more than isize::MAX bytes.
+/// * Guards against overflowing your length.
+/// * Calls `handle_alloc_error` for fallible allocations.
+/// * Contains a `ptr::Unique` and thus endows the user with all related benefits.
+/// * Uses the excess returned from the allocator to use the largest available capacity.
+///
+/// This type does not in anyway inspect the memory that it manages. When dropped it *will*
+/// free its memory, but it *won't* try to drop its contents. It is up to the user of `RawVec`
+/// to handle the actual things *stored* inside of a `RawVec`.
+///
+/// Note that the excess of a zero-sized types is always infinite, so `capacity()` always returns
+/// `usize::MAX`. This means that you need to be careful when round-tripping this type with a
+/// `Box<[T]>`, since `capacity()` won't yield the length.
+#[allow(missing_debug_implementations)]
+pub(crate) struct RawVec<T, A: Allocator = Global> {
+    ptr: Unique<T>,
+    cap: usize,
+    alloc: A,
+}
+
+impl<T> RawVec<T, Global> {
+    /// HACK(Centril): This exists because stable `const fn` can only call stable `const fn`, so
+    /// they cannot call `Self::new()`.
+    ///
+    /// If you change `RawVec<T>::new` or dependencies, please take care to not introduce anything
+    /// that would truly const-call something unstable.
+    pub const NEW: Self = Self::new();
+
+    /// Creates the biggest possible `RawVec` (on the system heap)
+    /// without allocating. If `T` has positive size, then this makes a
+    /// `RawVec` with capacity `0`. If `T` is zero-sized, then it makes a
+    /// `RawVec` with capacity `usize::MAX`. Useful for implementing
+    /// delayed allocation.
+    #[must_use]
+    pub const fn new() -> Self {
+        Self::new_in(Global)
+    }
+
+    /// Creates a `RawVec` (on the system heap) with exactly the
+    /// capacity and alignment requirements for a `[T; capacity]`. This is
+    /// equivalent to calling `RawVec::new` when `capacity` is `0` or `T` is
+    /// zero-sized. Note that if `T` is zero-sized this means you will
+    /// *not* get a `RawVec` with the requested capacity.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the requested capacity exceeds `isize::MAX` bytes.
+    ///
+    /// # Aborts
+    ///
+    /// Aborts on OOM.
+    #[cfg(not(any(no_global_oom_handling, test)))]
+    #[must_use]
+    #[inline]
+    pub fn with_capacity(capacity: usize) -> Self {
+        Self::with_capacity_in(capacity, Global)
+    }
+
+    /// Like `with_capacity`, but guarantees the buffer is zeroed.
+    #[cfg(not(any(no_global_oom_handling, test)))]
+    #[must_use]
+    #[inline]
+    pub fn with_capacity_zeroed(capacity: usize) -> Self {
+        Self::with_capacity_zeroed_in(capacity, Global)
+    }
+}
+
+impl<T, A: Allocator> RawVec<T, A> {
+    // Tiny Vecs are dumb. Skip to:
+    // - 8 if the element size is 1, because any heap allocators is likely
+    //   to round up a request of less than 8 bytes to at least 8 bytes.
+    // - 4 if elements are moderate-sized (<= 1 KiB).
+    // - 1 otherwise, to avoid wasting too much space for very short Vecs.
+    pub(crate) const MIN_NON_ZERO_CAP: usize = if mem::size_of::<T>() == 1 {
+        8
+    } else if mem::size_of::<T>() <= 1024 {
+        4
+    } else {
+        1
+    };
+
+    /// Like `new`, but parameterized over the choice of allocator for
+    /// the returned `RawVec`.
+    pub const fn new_in(alloc: A) -> Self {
+        // `cap: 0` means "unallocated". zero-sized types are ignored.
+        Self { ptr: Unique::dangling(), cap: 0, alloc }
+    }
+
+    /// Like `with_capacity`, but parameterized over the choice of
+    /// allocator for the returned `RawVec`.
+    #[cfg(not(no_global_oom_handling))]
+    #[inline]
+    pub fn with_capacity_in(capacity: usize, alloc: A) -> Self {
+        Self::allocate_in(capacity, AllocInit::Uninitialized, alloc)
+    }
+
+    /// Like `with_capacity_zeroed`, but parameterized over the choice
+    /// of allocator for the returned `RawVec`.
+    #[cfg(not(no_global_oom_handling))]
+    #[inline]
+    pub fn with_capacity_zeroed_in(capacity: usize, alloc: A) -> Self {
+        Self::allocate_in(capacity, AllocInit::Zeroed, alloc)
+    }
+
+    /// Converts the entire buffer into `Box<[MaybeUninit<T>]>` with the specified `len`.
+    ///
+    /// Note that this will correctly reconstitute any `cap` changes
+    /// that may have been performed. (See description of type for details.)
+    ///
+    /// # Safety
+    ///
+    /// * `len` must be greater than or equal to the most recently requested capacity, and
+    /// * `len` must be less than or equal to `self.capacity()`.
+    ///
+    /// Note, that the requested capacity and `self.capacity()` could differ, as
+    /// an allocator could overallocate and return a greater memory block than requested.
+    pub unsafe fn into_box(self, len: usize) -> Box<[MaybeUninit<T>], A> {
+        // Sanity-check one half of the safety requirement (we cannot check the other half).
+        debug_assert!(
+            len <= self.capacity(),
+            "`len` must be smaller than or equal to `self.capacity()`"
+        );
+
+        let me = ManuallyDrop::new(self);
+        unsafe {
+            let slice = slice::from_raw_parts_mut(me.ptr() as *mut MaybeUninit<T>, len);
+            Box::from_raw_in(slice, ptr::read(&me.alloc))
+        }
+    }
+
+    #[cfg(not(no_global_oom_handling))]
+    fn allocate_in(capacity: usize, init: AllocInit, alloc: A) -> Self {
+        // Don't allocate here because `Drop` will not deallocate when `capacity` is 0.
+        if mem::size_of::<T>() == 0 || capacity == 0 {
+            Self::new_in(alloc)
+        } else {
+            // We avoid `unwrap_or_else` here because it bloats the amount of
+            // LLVM IR generated.
+            let layout = match Layout::array::<T>(capacity) {
+                Ok(layout) => layout,
+                Err(_) => capacity_overflow(),
+            };
+            match alloc_guard(layout.size()) {
+                Ok(_) => {}
+                Err(_) => capacity_overflow(),
+            }
+            let result = match init {
+                AllocInit::Uninitialized => alloc.allocate(layout),
+                AllocInit::Zeroed => alloc.allocate_zeroed(layout),
+            };
+            let ptr = match result {
+                Ok(ptr) => ptr,
+                Err(_) => handle_alloc_error(layout),
+            };
+
+            // Allocators currently return a `NonNull<[u8]>` whose length
+            // matches the size requested. If that ever changes, the capacity
+            // here should change to `ptr.len() / mem::size_of::<T>()`.
+            Self {
+                ptr: unsafe { Unique::new_unchecked(ptr.cast().as_ptr()) },
+                cap: capacity,
+                alloc,
+            }
+        }
+    }
+
+    /// Reconstitutes a `RawVec` from a pointer, capacity, and allocator.
+    ///
+    /// # Safety
+    ///
+    /// The `ptr` must be allocated (via the given allocator `alloc`), and with the given
+    /// `capacity`.
+    /// The `capacity` cannot exceed `isize::MAX` for sized types. (only a concern on 32-bit
+    /// systems). ZST vectors may have a capacity up to `usize::MAX`.
+    /// If the `ptr` and `capacity` come from a `RawVec` created via `alloc`, then this is
+    /// guaranteed.
+    #[inline]
+    pub unsafe fn from_raw_parts_in(ptr: *mut T, capacity: usize, alloc: A) -> Self {
+        Self { ptr: unsafe { Unique::new_unchecked(ptr) }, cap: capacity, alloc }
+    }
+
+    /// Gets a raw pointer to the start of the allocation. Note that this is
+    /// `Unique::dangling()` if `capacity == 0` or `T` is zero-sized. In the former case, you must
+    /// be careful.
+    #[inline]
+    pub fn ptr(&self) -> *mut T {
+        self.ptr.as_ptr()
+    }
+
+    /// Gets the capacity of the allocation.
+    ///
+    /// This will always be `usize::MAX` if `T` is zero-sized.
+    #[inline(always)]
+    pub fn capacity(&self) -> usize {
+        if mem::size_of::<T>() == 0 { usize::MAX } else { self.cap }
+    }
+
+    /// Returns a shared reference to the allocator backing this `RawVec`.
+    pub fn allocator(&self) -> &A {
+        &self.alloc
+    }
+
+    fn current_memory(&self) -> Option<(NonNull<u8>, Layout)> {
+        if mem::size_of::<T>() == 0 || self.cap == 0 {
+            None
+        } else {
+            // We have an allocated chunk of memory, so we can bypass runtime
+            // checks to get our current layout.
+            unsafe {
+                let layout = Layout::array::<T>(self.cap).unwrap_unchecked();
+                Some((self.ptr.cast().into(), layout))
+            }
+        }
+    }
+
+    /// Ensures that the buffer contains at least enough space to hold `len +
+    /// additional` elements. If it doesn't already have enough capacity, will
+    /// reallocate enough space plus comfortable slack space to get amortized
+    /// *O*(1) behavior. Will limit this behavior if it would needlessly cause
+    /// itself to panic.
+    ///
+    /// If `len` exceeds `self.capacity()`, this may fail to actually allocate
+    /// the requested space. This is not really unsafe, but the unsafe
+    /// code *you* write that relies on the behavior of this function may break.
+    ///
+    /// This is ideal for implementing a bulk-push operation like `extend`.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the new capacity exceeds `isize::MAX` bytes.
+    ///
+    /// # Aborts
+    ///
+    /// Aborts on OOM.
+    #[cfg(not(no_global_oom_handling))]
+    #[inline]
+    pub fn reserve(&mut self, len: usize, additional: usize) {
+        // Callers expect this function to be very cheap when there is already sufficient capacity.
+        // Therefore, we move all the resizing and error-handling logic from grow_amortized and
+        // handle_reserve behind a call, while making sure that this function is likely to be
+        // inlined as just a comparison and a call if the comparison fails.
+        #[cold]
+        fn do_reserve_and_handle<T, A: Allocator>(
+            slf: &mut RawVec<T, A>,
+            len: usize,
+            additional: usize,
+        ) {
+            handle_reserve(slf.grow_amortized(len, additional));
+        }
+
+        if self.needs_to_grow(len, additional) {
+            do_reserve_and_handle(self, len, additional);
+        }
+    }
+
+    /// A specialized version of `reserve()` used only by the hot and
+    /// oft-instantiated `Vec::push()`, which does its own capacity check.
+    #[cfg(not(no_global_oom_handling))]
+    #[inline(never)]
+    pub fn reserve_for_push(&mut self, len: usize) {
+        handle_reserve(self.grow_amortized(len, 1));
+    }
+
+    /// The same as `reserve`, but returns on errors instead of panicking or aborting.
+    pub fn try_reserve(&mut self, len: usize, additional: usize) -> Result<(), TryReserveError> {
+        if self.needs_to_grow(len, additional) {
+            self.grow_amortized(len, additional)
+        } else {
+            Ok(())
+        }
+    }
+
+    /// The same as `reserve_for_push`, but returns on errors instead of panicking or aborting.
+    #[inline(never)]
+    pub fn try_reserve_for_push(&mut self, len: usize) -> Result<(), TryReserveError> {
+        self.grow_amortized(len, 1)
+    }
+
+    /// Ensures that the buffer contains at least enough space to hold `len +
+    /// additional` elements. If it doesn't already, will reallocate the
+    /// minimum possible amount of memory necessary. Generally this will be
+    /// exactly the amount of memory necessary, but in principle the allocator
+    /// is free to give back more than we asked for.
+    ///
+    /// If `len` exceeds `self.capacity()`, this may fail to actually allocate
+    /// the requested space. This is not really unsafe, but the unsafe code
+    /// *you* write that relies on the behavior of this function may break.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the new capacity exceeds `isize::MAX` bytes.
+    ///
+    /// # Aborts
+    ///
+    /// Aborts on OOM.
+    #[cfg(not(no_global_oom_handling))]
+    pub fn reserve_exact(&mut self, len: usize, additional: usize) {
+        handle_reserve(self.try_reserve_exact(len, additional));
+    }
+
+    /// The same as `reserve_exact`, but returns on errors instead of panicking or aborting.
+    pub fn try_reserve_exact(
+        &mut self,
+        len: usize,
+        additional: usize,
+    ) -> Result<(), TryReserveError> {
+        if self.needs_to_grow(len, additional) { self.grow_exact(len, additional) } else { Ok(()) }
+    }
+
+    /// Shrinks the buffer down to the specified capacity. If the given amount
+    /// is 0, actually completely deallocates.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the given amount is *larger* than the current capacity.
+    ///
+    /// # Aborts
+    ///
+    /// Aborts on OOM.
+    #[cfg(not(no_global_oom_handling))]
+    pub fn shrink_to_fit(&mut self, cap: usize) {
+        handle_reserve(self.shrink(cap));
+    }
+}
+
+impl<T, A: Allocator> RawVec<T, A> {
+    /// Returns if the buffer needs to grow to fulfill the needed extra capacity.
+    /// Mainly used to make inlining reserve-calls possible without inlining `grow`.
+    fn needs_to_grow(&self, len: usize, additional: usize) -> bool {
+        additional > self.capacity().wrapping_sub(len)
+    }
+
+    fn set_ptr_and_cap(&mut self, ptr: NonNull<[u8]>, cap: usize) {
+        // Allocators currently return a `NonNull<[u8]>` whose length matches
+        // the size requested. If that ever changes, the capacity here should
+        // change to `ptr.len() / mem::size_of::<T>()`.
+        self.ptr = unsafe { Unique::new_unchecked(ptr.cast().as_ptr()) };
+        self.cap = cap;
+    }
+
+    // This method is usually instantiated many times. So we want it to be as
+    // small as possible, to improve compile times. But we also want as much of
+    // its contents to be statically computable as possible, to make the
+    // generated code run faster. Therefore, this method is carefully written
+    // so that all of the code that depends on `T` is within it, while as much
+    // of the code that doesn't depend on `T` as possible is in functions that
+    // are non-generic over `T`.
+    fn grow_amortized(&mut self, len: usize, additional: usize) -> Result<(), TryReserveError> {
+        // This is ensured by the calling contexts.
+        debug_assert!(additional > 0);
+
+        if mem::size_of::<T>() == 0 {
+            // Since we return a capacity of `usize::MAX` when `elem_size` is
+            // 0, getting to here necessarily means the `RawVec` is overfull.
+            return Err(CapacityOverflow.into());
+        }
+
+        // Nothing we can really do about these checks, sadly.
+        let required_cap = len.checked_add(additional).ok_or(CapacityOverflow)?;
+
+        // This guarantees exponential growth. The doubling cannot overflow
+        // because `cap <= isize::MAX` and the type of `cap` is `usize`.
+        let cap = cmp::max(self.cap * 2, required_cap);
+        let cap = cmp::max(Self::MIN_NON_ZERO_CAP, cap);
+
+        let new_layout = Layout::array::<T>(cap);
+
+        // `finish_grow` is non-generic over `T`.
+        let ptr = finish_grow(new_layout, self.current_memory(), &mut self.alloc)?;
+        self.set_ptr_and_cap(ptr, cap);
+        Ok(())
+    }
+
+    // The constraints on this method are much the same as those on
+    // `grow_amortized`, but this method is usually instantiated less often so
+    // it's less critical.
+    fn grow_exact(&mut self, len: usize, additional: usize) -> Result<(), TryReserveError> {
+        if mem::size_of::<T>() == 0 {
+            // Since we return a capacity of `usize::MAX` when the type size is
+            // 0, getting to here necessarily means the `RawVec` is overfull.
+            return Err(CapacityOverflow.into());
+        }
+
+        let cap = len.checked_add(additional).ok_or(CapacityOverflow)?;
+        let new_layout = Layout::array::<T>(cap);
+
+        // `finish_grow` is non-generic over `T`.
+        let ptr = finish_grow(new_layout, self.current_memory(), &mut self.alloc)?;
+        self.set_ptr_and_cap(ptr, cap);
+        Ok(())
+    }
+
+    #[allow(dead_code)]
+    fn shrink(&mut self, cap: usize) -> Result<(), TryReserveError> {
+        assert!(cap <= self.capacity(), "Tried to shrink to a larger capacity");
+
+        let (ptr, layout) = if let Some(mem) = self.current_memory() { mem } else { return Ok(()) };
+
+        let ptr = unsafe {
+            // `Layout::array` cannot overflow here because it would have
+            // overflowed earlier when capacity was larger.
+            let new_layout = Layout::array::<T>(cap).unwrap_unchecked();
+            self.alloc
+                .shrink(ptr, layout, new_layout)
+                .map_err(|_| AllocError { layout: new_layout, non_exhaustive: () })?
+        };
+        self.set_ptr_and_cap(ptr, cap);
+        Ok(())
+    }
+}
+
+// This function is outside `RawVec` to minimize compile times. See the comment
+// above `RawVec::grow_amortized` for details. (The `A` parameter isn't
+// significant, because the number of different `A` types seen in practice is
+// much smaller than the number of `T` types.)
+#[inline(never)]
+fn finish_grow<A>(
+    new_layout: Result<Layout, LayoutError>,
+    current_memory: Option<(NonNull<u8>, Layout)>,
+    alloc: &mut A,
+) -> Result<NonNull<[u8]>, TryReserveError>
+where
+    A: Allocator,
+{
+    // Check for the error here to minimize the size of `RawVec::grow_*`.
+    let new_layout = new_layout.map_err(|_| CapacityOverflow)?;
+
+    alloc_guard(new_layout.size())?;
+
+    let memory = if let Some((ptr, old_layout)) = current_memory {
+        debug_assert_eq!(old_layout.align(), new_layout.align());
+        unsafe {
+            // The allocator checks for alignment equality
+            intrinsics::assume(old_layout.align() == new_layout.align());
+            alloc.grow(ptr, old_layout, new_layout)
+        }
+    } else {
+        alloc.allocate(new_layout)
+    };
+
+    memory.map_err(|_| AllocError { layout: new_layout, non_exhaustive: () }.into())
+}
+
+unsafe impl<#[may_dangle] T, A: Allocator> Drop for RawVec<T, A> {
+    /// Frees the memory owned by the `RawVec` *without* trying to drop its contents.
+    fn drop(&mut self) {
+        if let Some((ptr, layout)) = self.current_memory() {
+            unsafe { self.alloc.deallocate(ptr, layout) }
+        }
+    }
+}
+
+// Central function for reserve error handling.
+#[cfg(not(no_global_oom_handling))]
+#[inline]
+fn handle_reserve(result: Result<(), TryReserveError>) {
+    match result.map_err(|e| e.kind()) {
+        Err(CapacityOverflow) => capacity_overflow(),
+        Err(AllocError { layout, .. }) => handle_alloc_error(layout),
+        Ok(()) => { /* yay */ }
+    }
+}
+
+// We need to guarantee the following:
+// * We don't ever allocate `> isize::MAX` byte-size objects.
+// * We don't overflow `usize::MAX` and actually allocate too little.
+//
+// On 64-bit we just need to check for overflow since trying to allocate
+// `> isize::MAX` bytes will surely fail. On 32-bit and 16-bit we need to add
+// an extra guard for this in case we're running on a platform which can use
+// all 4GB in user-space, e.g., PAE or x32.
+
+#[inline]
+fn alloc_guard(alloc_size: usize) -> Result<(), TryReserveError> {
+    if usize::BITS < 64 && alloc_size > isize::MAX as usize {
+        Err(CapacityOverflow.into())
+    } else {
+        Ok(())
+    }
+}
+
+// One central function responsible for reporting capacity overflows. This'll
+// ensure that the code generation related to these panics is minimal as there's
+// only one location which panics rather than a bunch throughout the module.
+#[cfg(not(no_global_oom_handling))]
+fn capacity_overflow() -> ! {
+    panic!("capacity overflow");
+}

rust/alloc/vec/drain.rs

@@ -0,0 +1,186 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use crate::alloc::{Allocator, Global};
+use core::fmt;
+use core::iter::{FusedIterator, TrustedLen};
+use core::mem;
+use core::ptr::{self, NonNull};
+use core::slice::{self};
+
+use super::Vec;
+
+/// A draining iterator for `Vec<T>`.
+///
+/// This `struct` is created by [`Vec::drain`].
+/// See its documentation for more.
+///
+/// # Example
+///
+/// ```
+/// let mut v = vec![0, 1, 2];
+/// let iter: std::vec::Drain<_> = v.drain(..);
+/// ```
+#[stable(feature = "drain", since = "1.6.0")]
+pub struct Drain<
+    'a,
+    T: 'a,
+    #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator + 'a = Global,
+> {
+    /// Index of tail to preserve
+    pub(super) tail_start: usize,
+    /// Length of tail
+    pub(super) tail_len: usize,
+    /// Current remaining range to remove
+    pub(super) iter: slice::Iter<'a, T>,
+    pub(super) vec: NonNull<Vec<T, A>>,
+}
+
+#[stable(feature = "collection_debug", since = "1.17.0")]
+impl<T: fmt::Debug, A: Allocator> fmt::Debug for Drain<'_, T, A> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_tuple("Drain").field(&self.iter.as_slice()).finish()
+    }
+}
+
+impl<'a, T, A: Allocator> Drain<'a, T, A> {
+    /// Returns the remaining items of this iterator as a slice.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let mut vec = vec!['a', 'b', 'c'];
+    /// let mut drain = vec.drain(..);
+    /// assert_eq!(drain.as_slice(), &['a', 'b', 'c']);
+    /// let _ = drain.next().unwrap();
+    /// assert_eq!(drain.as_slice(), &['b', 'c']);
+    /// ```
+    #[must_use]
+    #[stable(feature = "vec_drain_as_slice", since = "1.46.0")]
+    pub fn as_slice(&self) -> &[T] {
+        self.iter.as_slice()
+    }
+
+    /// Returns a reference to the underlying allocator.
+    #[unstable(feature = "allocator_api", issue = "32838")]
+    #[must_use]
+    #[inline]
+    pub fn allocator(&self) -> &A {
+        unsafe { self.vec.as_ref().allocator() }
+    }
+}
+
+#[stable(feature = "vec_drain_as_slice", since = "1.46.0")]
+impl<'a, T, A: Allocator> AsRef<[T]> for Drain<'a, T, A> {
+    fn as_ref(&self) -> &[T] {
+        self.as_slice()
+    }
+}
+
+#[stable(feature = "drain", since = "1.6.0")]
+unsafe impl<T: Sync, A: Sync + Allocator> Sync for Drain<'_, T, A> {}
+#[stable(feature = "drain", since = "1.6.0")]
+unsafe impl<T: Send, A: Send + Allocator> Send for Drain<'_, T, A> {}
+
+#[stable(feature = "drain", since = "1.6.0")]
+impl<T, A: Allocator> Iterator for Drain<'_, T, A> {
+    type Item = T;
+
+    #[inline]
+    fn next(&mut self) -> Option<T> {
+        self.iter.next().map(|elt| unsafe { ptr::read(elt as *const _) })
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+}
+
+#[stable(feature = "drain", since = "1.6.0")]
+impl<T, A: Allocator> DoubleEndedIterator for Drain<'_, T, A> {
+    #[inline]
+    fn next_back(&mut self) -> Option<T> {
+        self.iter.next_back().map(|elt| unsafe { ptr::read(elt as *const _) })
+    }
+}
+
+#[stable(feature = "drain", since = "1.6.0")]
+impl<T, A: Allocator> Drop for Drain<'_, T, A> {
+    fn drop(&mut self) {
+        /// Moves back the un-`Drain`ed elements to restore the original `Vec`.
+        struct DropGuard<'r, 'a, T, A: Allocator>(&'r mut Drain<'a, T, A>);
+
+        impl<'r, 'a, T, A: Allocator> Drop for DropGuard<'r, 'a, T, A> {
+            fn drop(&mut self) {
+                if self.0.tail_len > 0 {
+                    unsafe {
+                        let source_vec = self.0.vec.as_mut();
+                        // memmove back untouched tail, update to new length
+                        let start = source_vec.len();
+                        let tail = self.0.tail_start;
+                        if tail != start {
+                            let src = source_vec.as_ptr().add(tail);
+                            let dst = source_vec.as_mut_ptr().add(start);
+                            ptr::copy(src, dst, self.0.tail_len);
+                        }
+                        source_vec.set_len(start + self.0.tail_len);
+                    }
+                }
+            }
+        }
+
+        let iter = mem::replace(&mut self.iter, (&mut []).iter());
+        let drop_len = iter.len();
+
+        let mut vec = self.vec;
+
+        if mem::size_of::<T>() == 0 {
+            // ZSTs have no identity, so we don't need to move them around, we only need to drop the correct amount.
+            // this can be achieved by manipulating the Vec length instead of moving values out from `iter`.
+            unsafe {
+                let vec = vec.as_mut();
+                let old_len = vec.len();
+                vec.set_len(old_len + drop_len + self.tail_len);
+                vec.truncate(old_len + self.tail_len);
+            }
+
+            return;
+        }
+
+        // ensure elements are moved back into their appropriate places, even when drop_in_place panics
+        let _guard = DropGuard(self);
+
+        if drop_len == 0 {
+            return;
+        }
+
+        // as_slice() must only be called when iter.len() is > 0 because
+        // vec::Splice modifies vec::Drain fields and may grow the vec which would invalidate
+        // the iterator's internal pointers. Creating a reference to deallocated memory
+        // is invalid even when it is zero-length
+        let drop_ptr = iter.as_slice().as_ptr();
+
+        unsafe {
+            // drop_ptr comes from a slice::Iter which only gives us a &[T] but for drop_in_place
+            // a pointer with mutable provenance is necessary. Therefore we must reconstruct
+            // it from the original vec but also avoid creating a &mut to the front since that could
+            // invalidate raw pointers to it which some unsafe code might rely on.
+            let vec_ptr = vec.as_mut().as_mut_ptr();
+            let drop_offset = drop_ptr.sub_ptr(vec_ptr);
+            let to_drop = ptr::slice_from_raw_parts_mut(vec_ptr.add(drop_offset), drop_len);
+            ptr::drop_in_place(to_drop);
+        }
+    }
+}
+
+#[stable(feature = "drain", since = "1.6.0")]
+impl<T, A: Allocator> ExactSizeIterator for Drain<'_, T, A> {
+    fn is_empty(&self) -> bool {
+        self.iter.is_empty()
+    }
+}
+
+#[unstable(feature = "trusted_len", issue = "37572")]
+unsafe impl<T, A: Allocator> TrustedLen for Drain<'_, T, A> {}
+
+#[stable(feature = "fused", since = "1.26.0")]
+impl<T, A: Allocator> FusedIterator for Drain<'_, T, A> {}

rust/alloc/vec/drain_filter.rs

@@ -0,0 +1,145 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use crate::alloc::{Allocator, Global};
+use core::ptr::{self};
+use core::slice::{self};
+
+use super::Vec;
+
+/// An iterator which uses a closure to determine if an element should be removed.
+///
+/// This struct is created by [`Vec::drain_filter`].
+/// See its documentation for more.
+///
+/// # Example
+///
+/// ```
+/// #![feature(drain_filter)]
+///
+/// let mut v = vec![0, 1, 2];
+/// let iter: std::vec::DrainFilter<_, _> = v.drain_filter(|x| *x % 2 == 0);
+/// ```
+#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
+#[derive(Debug)]
+pub struct DrainFilter<
+    'a,
+    T,
+    F,
+    #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
+> where
+    F: FnMut(&mut T) -> bool,
+{
+    pub(super) vec: &'a mut Vec<T, A>,
+    /// The index of the item that will be inspected by the next call to `next`.
+    pub(super) idx: usize,
+    /// The number of items that have been drained (removed) thus far.
+    pub(super) del: usize,
+    /// The original length of `vec` prior to draining.
+    pub(super) old_len: usize,
+    /// The filter test predicate.
+    pub(super) pred: F,
+    /// A flag that indicates a panic has occurred in the filter test predicate.
+    /// This is used as a hint in the drop implementation to prevent consumption
+    /// of the remainder of the `DrainFilter`. Any unprocessed items will be
+    /// backshifted in the `vec`, but no further items will be dropped or
+    /// tested by the filter predicate.
+    pub(super) panic_flag: bool,
+}
+
+impl<T, F, A: Allocator> DrainFilter<'_, T, F, A>
+where
+    F: FnMut(&mut T) -> bool,
+{
+    /// Returns a reference to the underlying allocator.
+    #[unstable(feature = "allocator_api", issue = "32838")]
+    #[inline]
+    pub fn allocator(&self) -> &A {
+        self.vec.allocator()
+    }
+}
+
+#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
+impl<T, F, A: Allocator> Iterator for DrainFilter<'_, T, F, A>
+where
+    F: FnMut(&mut T) -> bool,
+{
+    type Item = T;
+
+    fn next(&mut self) -> Option<T> {
+        unsafe {
+            while self.idx < self.old_len {
+                let i = self.idx;
+                let v = slice::from_raw_parts_mut(self.vec.as_mut_ptr(), self.old_len);
+                self.panic_flag = true;
+                let drained = (self.pred)(&mut v[i]);
+                self.panic_flag = false;
+                // Update the index *after* the predicate is called. If the index
+                // is updated prior and the predicate panics, the element at this
+                // index would be leaked.
+                self.idx += 1;
+                if drained {
+                    self.del += 1;
+                    return Some(ptr::read(&v[i]));
+                } else if self.del > 0 {
+                    let del = self.del;
+                    let src: *const T = &v[i];
+                    let dst: *mut T = &mut v[i - del];
+                    ptr::copy_nonoverlapping(src, dst, 1);
+                }
+            }
+            None
+        }
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (0, Some(self.old_len - self.idx))
+    }
+}
+
+#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
+impl<T, F, A: Allocator> Drop for DrainFilter<'_, T, F, A>
+where
+    F: FnMut(&mut T) -> bool,
+{
+    fn drop(&mut self) {
+        struct BackshiftOnDrop<'a, 'b, T, F, A: Allocator>
+        where
+            F: FnMut(&mut T) -> bool,
+        {
+            drain: &'b mut DrainFilter<'a, T, F, A>,
+        }
+
+        impl<'a, 'b, T, F, A: Allocator> Drop for BackshiftOnDrop<'a, 'b, T, F, A>
+        where
+            F: FnMut(&mut T) -> bool,
+        {
+            fn drop(&mut self) {
+                unsafe {
+                    if self.drain.idx < self.drain.old_len && self.drain.del > 0 {
+                        // This is a pretty messed up state, and there isn't really an
+                        // obviously right thing to do. We don't want to keep trying
+                        // to execute `pred`, so we just backshift all the unprocessed
+                        // elements and tell the vec that they still exist. The backshift
+                        // is required to prevent a double-drop of the last successfully
+                        // drained item prior to a panic in the predicate.
+                        let ptr = self.drain.vec.as_mut_ptr();
+                        let src = ptr.add(self.drain.idx);
+                        let dst = src.sub(self.drain.del);
+                        let tail_len = self.drain.old_len - self.drain.idx;
+                        src.copy_to(dst, tail_len);
+                    }
+                    self.drain.vec.set_len(self.drain.old_len - self.drain.del);
+                }
+            }
+        }
+
+        let backshift = BackshiftOnDrop { drain: self };
+
+        // Attempt to consume any remaining elements if the filter predicate
+        // has not yet panicked. We'll backshift any remaining elements
+        // whether we've already panicked or if the consumption here panics.
+        if !backshift.drain.panic_flag {
+            backshift.drain.for_each(drop);
+        }
+    }
+}

rust/alloc/vec/into_iter.rs

@@ -0,0 +1,366 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+#[cfg(not(no_global_oom_handling))]
+use super::AsVecIntoIter;
+use crate::alloc::{Allocator, Global};
+use crate::raw_vec::RawVec;
+use core::fmt;
+use core::intrinsics::arith_offset;
+use core::iter::{
+    FusedIterator, InPlaceIterable, SourceIter, TrustedLen, TrustedRandomAccessNoCoerce,
+};
+use core::marker::PhantomData;
+use core::mem::{self, ManuallyDrop};
+#[cfg(not(no_global_oom_handling))]
+use core::ops::Deref;
+use core::ptr::{self, NonNull};
+use core::slice::{self};
+
+/// An iterator that moves out of a vector.
+///
+/// This `struct` is created by the `into_iter` method on [`Vec`](super::Vec)
+/// (provided by the [`IntoIterator`] trait).
+///
+/// # Example
+///
+/// ```
+/// let v = vec![0, 1, 2];
+/// let iter: std::vec::IntoIter<_> = v.into_iter();
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_insignificant_dtor]
+pub struct IntoIter<
+    T,
+    #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
+> {
+    pub(super) buf: NonNull<T>,
+    pub(super) phantom: PhantomData<T>,
+    pub(super) cap: usize,
+    // the drop impl reconstructs a RawVec from buf, cap and alloc
+    // to avoid dropping the allocator twice we need to wrap it into ManuallyDrop
+    pub(super) alloc: ManuallyDrop<A>,
+    pub(super) ptr: *const T,
+    pub(super) end: *const T,
+}
+
+#[stable(feature = "vec_intoiter_debug", since = "1.13.0")]
+impl<T: fmt::Debug, A: Allocator> fmt::Debug for IntoIter<T, A> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_tuple("IntoIter").field(&self.as_slice()).finish()
+    }
+}
+
+impl<T, A: Allocator> IntoIter<T, A> {
+    /// Returns the remaining items of this iterator as a slice.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let vec = vec!['a', 'b', 'c'];
+    /// let mut into_iter = vec.into_iter();
+    /// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
+    /// let _ = into_iter.next().unwrap();
+    /// assert_eq!(into_iter.as_slice(), &['b', 'c']);
+    /// ```
+    #[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
+    pub fn as_slice(&self) -> &[T] {
+        unsafe { slice::from_raw_parts(self.ptr, self.len()) }
+    }
+
+    /// Returns the remaining items of this iterator as a mutable slice.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let vec = vec!['a', 'b', 'c'];
+    /// let mut into_iter = vec.into_iter();
+    /// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
+    /// into_iter.as_mut_slice()[2] = 'z';
+    /// assert_eq!(into_iter.next().unwrap(), 'a');
+    /// assert_eq!(into_iter.next().unwrap(), 'b');
+    /// assert_eq!(into_iter.next().unwrap(), 'z');
+    /// ```
+    #[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
+    pub fn as_mut_slice(&mut self) -> &mut [T] {
+        unsafe { &mut *self.as_raw_mut_slice() }
+    }
+
+    /// Returns a reference to the underlying allocator.
+    #[unstable(feature = "allocator_api", issue = "32838")]
+    #[inline]
+    pub fn allocator(&self) -> &A {
+        &self.alloc
+    }
+
+    fn as_raw_mut_slice(&mut self) -> *mut [T] {
+        ptr::slice_from_raw_parts_mut(self.ptr as *mut T, self.len())
+    }
+
+    /// Drops remaining elements and relinquishes the backing allocation.
+    ///
+    /// This is roughly equivalent to the following, but more efficient
+    ///
+    /// ```
+    /// # let mut into_iter = Vec::<u8>::with_capacity(10).into_iter();
+    /// (&mut into_iter).for_each(core::mem::drop);
+    /// unsafe { core::ptr::write(&mut into_iter, Vec::new().into_iter()); }
+    /// ```
+    ///
+    /// This method is used by in-place iteration, refer to the vec::in_place_collect
+    /// documentation for an overview.
+    #[cfg(not(no_global_oom_handling))]
+    pub(super) fn forget_allocation_drop_remaining(&mut self) {
+        let remaining = self.as_raw_mut_slice();
+
+        // overwrite the individual fields instead of creating a new
+        // struct and then overwriting &mut self.
+        // this creates less assembly
+        self.cap = 0;
+        self.buf = unsafe { NonNull::new_unchecked(RawVec::NEW.ptr()) };
+        self.ptr = self.buf.as_ptr();
+        self.end = self.buf.as_ptr();
+
+        unsafe {
+            ptr::drop_in_place(remaining);
+        }
+    }
+
+    /// Forgets to Drop the remaining elements while still allowing the backing allocation to be freed.
+    #[allow(dead_code)]
+    pub(crate) fn forget_remaining_elements(&mut self) {
+        self.ptr = self.end;
+    }
+}
+
+#[stable(feature = "vec_intoiter_as_ref", since = "1.46.0")]
+impl<T, A: Allocator> AsRef<[T]> for IntoIter<T, A> {
+    fn as_ref(&self) -> &[T] {
+        self.as_slice()
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+unsafe impl<T: Send, A: Allocator + Send> Send for IntoIter<T, A> {}
+#[stable(feature = "rust1", since = "1.0.0")]
+unsafe impl<T: Sync, A: Allocator + Sync> Sync for IntoIter<T, A> {}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T, A: Allocator> Iterator for IntoIter<T, A> {
+    type Item = T;
+
+    #[inline]
+    fn next(&mut self) -> Option<T> {
+        if self.ptr as *const _ == self.end {
+            None
+        } else if mem::size_of::<T>() == 0 {
+            // purposefully don't use 'ptr.offset' because for
+            // vectors with 0-size elements this would return the
+            // same pointer.
+            self.ptr = unsafe { arith_offset(self.ptr as *const i8, 1) as *mut T };
+
+            // Make up a value of this ZST.
+            Some(unsafe { mem::zeroed() })
+        } else {
+            let old = self.ptr;
+            self.ptr = unsafe { self.ptr.offset(1) };
+
+            Some(unsafe { ptr::read(old) })
+        }
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let exact = if mem::size_of::<T>() == 0 {
+            self.end.addr().wrapping_sub(self.ptr.addr())
+        } else {
+            unsafe { self.end.sub_ptr(self.ptr) }
+        };
+        (exact, Some(exact))
+    }
+
+    #[inline]
+    fn advance_by(&mut self, n: usize) -> Result<(), usize> {
+        let step_size = self.len().min(n);
+        let to_drop = ptr::slice_from_raw_parts_mut(self.ptr as *mut T, step_size);
+        if mem::size_of::<T>() == 0 {
+            // SAFETY: due to unchecked casts of unsigned amounts to signed offsets the wraparound
+            // effectively results in unsigned pointers representing positions 0..usize::MAX,
+            // which is valid for ZSTs.
+            self.ptr = unsafe { arith_offset(self.ptr as *const i8, step_size as isize) as *mut T }
+        } else {
+            // SAFETY: the min() above ensures that step_size is in bounds
+            self.ptr = unsafe { self.ptr.add(step_size) };
+        }
+        // SAFETY: the min() above ensures that step_size is in bounds
+        unsafe {
+            ptr::drop_in_place(to_drop);
+        }
+        if step_size < n {
+            return Err(step_size);
+        }
+        Ok(())
+    }
+
+    #[inline]
+    fn count(self) -> usize {
+        self.len()
+    }
+
+    unsafe fn __iterator_get_unchecked(&mut self, i: usize) -> Self::Item
+    where
+        Self: TrustedRandomAccessNoCoerce,
+    {
+        // SAFETY: the caller must guarantee that `i` is in bounds of the
+        // `Vec<T>`, so `i` cannot overflow an `isize`, and the `self.ptr.add(i)`
+        // is guaranteed to pointer to an element of the `Vec<T>` and
+        // thus guaranteed to be valid to dereference.
+        //
+        // Also note the implementation of `Self: TrustedRandomAccess` requires
+        // that `T: Copy` so reading elements from the buffer doesn't invalidate
+        // them for `Drop`.
+        unsafe {
+            if mem::size_of::<T>() == 0 { mem::zeroed() } else { ptr::read(self.ptr.add(i)) }
+        }
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T, A: Allocator> DoubleEndedIterator for IntoIter<T, A> {
+    #[inline]
+    fn next_back(&mut self) -> Option<T> {
+        if self.end == self.ptr {
+            None
+        } else if mem::size_of::<T>() == 0 {
+            // See above for why 'ptr.offset' isn't used
+            self.end = unsafe { arith_offset(self.end as *const i8, -1) as *mut T };
+
+            // Make up a value of this ZST.
+            Some(unsafe { mem::zeroed() })
+        } else {
+            self.end = unsafe { self.end.offset(-1) };
+
+            Some(unsafe { ptr::read(self.end) })
+        }
+    }
+
+    #[inline]
+    fn advance_back_by(&mut self, n: usize) -> Result<(), usize> {
+        let step_size = self.len().min(n);
+        if mem::size_of::<T>() == 0 {
+            // SAFETY: same as for advance_by()
+            self.end = unsafe {
+                arith_offset(self.end as *const i8, step_size.wrapping_neg() as isize) as *mut T
+            }
+        } else {
+            // SAFETY: same as for advance_by()
+            self.end = unsafe { self.end.offset(step_size.wrapping_neg() as isize) };
+        }
+        let to_drop = ptr::slice_from_raw_parts_mut(self.end as *mut T, step_size);
+        // SAFETY: same as for advance_by()
+        unsafe {
+            ptr::drop_in_place(to_drop);
+        }
+        if step_size < n {
+            return Err(step_size);
+        }
+        Ok(())
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T, A: Allocator> ExactSizeIterator for IntoIter<T, A> {
+    fn is_empty(&self) -> bool {
+        self.ptr == self.end
+    }
+}
+
+#[stable(feature = "fused", since = "1.26.0")]
+impl<T, A: Allocator> FusedIterator for IntoIter<T, A> {}
+
+#[unstable(feature = "trusted_len", issue = "37572")]
+unsafe impl<T, A: Allocator> TrustedLen for IntoIter<T, A> {}
+
+#[doc(hidden)]
+#[unstable(issue = "none", feature = "std_internals")]
+#[rustc_unsafe_specialization_marker]
+pub trait NonDrop {}
+
+// T: Copy as approximation for !Drop since get_unchecked does not advance self.ptr
+// and thus we can't implement drop-handling
+#[unstable(issue = "none", feature = "std_internals")]
+impl<T: Copy> NonDrop for T {}
+
+#[doc(hidden)]
+#[unstable(issue = "none", feature = "std_internals")]
+// TrustedRandomAccess (without NoCoerce) must not be implemented because
+// subtypes/supertypes of `T` might not be `NonDrop`
+unsafe impl<T, A: Allocator> TrustedRandomAccessNoCoerce for IntoIter<T, A>
+where
+    T: NonDrop,
+{
+    const MAY_HAVE_SIDE_EFFECT: bool = false;
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "vec_into_iter_clone", since = "1.8.0")]
+impl<T: Clone, A: Allocator + Clone> Clone for IntoIter<T, A> {
+    #[cfg(not(test))]
+    fn clone(&self) -> Self {
+        self.as_slice().to_vec_in(self.alloc.deref().clone()).into_iter()
+    }
+    #[cfg(test)]
+    fn clone(&self) -> Self {
+        crate::slice::to_vec(self.as_slice(), self.alloc.deref().clone()).into_iter()
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+unsafe impl<#[may_dangle] T, A: Allocator> Drop for IntoIter<T, A> {
+    fn drop(&mut self) {
+        struct DropGuard<'a, T, A: Allocator>(&'a mut IntoIter<T, A>);
+
+        impl<T, A: Allocator> Drop for DropGuard<'_, T, A> {
+            fn drop(&mut self) {
+                unsafe {
+                    // `IntoIter::alloc` is not used anymore after this and will be dropped by RawVec
+                    let alloc = ManuallyDrop::take(&mut self.0.alloc);
+                    // RawVec handles deallocation
+                    let _ = RawVec::from_raw_parts_in(self.0.buf.as_ptr(), self.0.cap, alloc);
+                }
+            }
+        }
+
+        let guard = DropGuard(self);
+        // destroy the remaining elements
+        unsafe {
+            ptr::drop_in_place(guard.0.as_raw_mut_slice());
+        }
+        // now `guard` will be dropped and do the rest
+    }
+}
+
+// In addition to the SAFETY invariants of the following three unsafe traits
+// also refer to the vec::in_place_collect module documentation to get an overview
+#[unstable(issue = "none", feature = "inplace_iteration")]
+#[doc(hidden)]
+unsafe impl<T, A: Allocator> InPlaceIterable for IntoIter<T, A> {}
+
+#[unstable(issue = "none", feature = "inplace_iteration")]
+#[doc(hidden)]
+unsafe impl<T, A: Allocator> SourceIter for IntoIter<T, A> {
+    type Source = Self;
+
+    #[inline]
+    unsafe fn as_inner(&mut self) -> &mut Self::Source {
+        self
+    }
+}
+
+#[cfg(not(no_global_oom_handling))]
+unsafe impl<T> AsVecIntoIter for IntoIter<T> {
+    type Item = T;
+
+    fn as_into_iter(&mut self) -> &mut IntoIter<Self::Item> {
+        self
+    }
+}

rust/alloc/vec/is_zero.rs

@@ -0,0 +1,120 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use crate::boxed::Box;
+
+#[rustc_specialization_trait]
+pub(super) unsafe trait IsZero {
+    /// Whether this value's representation is all zeros
+    fn is_zero(&self) -> bool;
+}
+
+macro_rules! impl_is_zero {
+    ($t:ty, $is_zero:expr) => {
+        unsafe impl IsZero for $t {
+            #[inline]
+            fn is_zero(&self) -> bool {
+                $is_zero(*self)
+            }
+        }
+    };
+}
+
+impl_is_zero!(i16, |x| x == 0);
+impl_is_zero!(i32, |x| x == 0);
+impl_is_zero!(i64, |x| x == 0);
+impl_is_zero!(i128, |x| x == 0);
+impl_is_zero!(isize, |x| x == 0);
+
+impl_is_zero!(u16, |x| x == 0);
+impl_is_zero!(u32, |x| x == 0);
+impl_is_zero!(u64, |x| x == 0);
+impl_is_zero!(u128, |x| x == 0);
+impl_is_zero!(usize, |x| x == 0);
+
+impl_is_zero!(bool, |x| x == false);
+impl_is_zero!(char, |x| x == '\0');
+
+impl_is_zero!(f32, |x: f32| x.to_bits() == 0);
+impl_is_zero!(f64, |x: f64| x.to_bits() == 0);
+
+unsafe impl<T> IsZero for *const T {
+    #[inline]
+    fn is_zero(&self) -> bool {
+        (*self).is_null()
+    }
+}
+
+unsafe impl<T> IsZero for *mut T {
+    #[inline]
+    fn is_zero(&self) -> bool {
+        (*self).is_null()
+    }
+}
+
+unsafe impl<T: IsZero, const N: usize> IsZero for [T; N] {
+    #[inline]
+    fn is_zero(&self) -> bool {
+        // Because this is generated as a runtime check, it's not obvious that
+        // it's worth doing if the array is really long.  The threshold here
+        // is largely arbitrary, but was picked because as of 2022-05-01 LLVM
+        // can const-fold the check in `vec![[0; 32]; n]` but not in
+        // `vec![[0; 64]; n]`: https://godbolt.org/z/WTzjzfs5b
+        // Feel free to tweak if you have better evidence.
+
+        N <= 32 && self.iter().all(IsZero::is_zero)
+    }
+}
+
+// `Option<&T>` and `Option<Box<T>>` are guaranteed to represent `None` as null.
+// For fat pointers, the bytes that would be the pointer metadata in the `Some`
+// variant are padding in the `None` variant, so ignoring them and
+// zero-initializing instead is ok.
+// `Option<&mut T>` never implements `Clone`, so there's no need for an impl of
+// `SpecFromElem`.
+
+unsafe impl<T: ?Sized> IsZero for Option<&T> {
+    #[inline]
+    fn is_zero(&self) -> bool {
+        self.is_none()
+    }
+}
+
+unsafe impl<T: ?Sized> IsZero for Option<Box<T>> {
+    #[inline]
+    fn is_zero(&self) -> bool {
+        self.is_none()
+    }
+}
+
+// `Option<num::NonZeroU32>` and similar have a representation guarantee that
+// they're the same size as the corresponding `u32` type, as well as a guarantee
+// that transmuting between `NonZeroU32` and `Option<num::NonZeroU32>` works.
+// While the documentation officially makes it UB to transmute from `None`,
+// we're the standard library so we can make extra inferences, and we know that
+// the only niche available to represent `None` is the one that's all zeros.
+
+macro_rules! impl_is_zero_option_of_nonzero {
+    ($($t:ident,)+) => {$(
+        unsafe impl IsZero for Option<core::num::$t> {
+            #[inline]
+            fn is_zero(&self) -> bool {
+                self.is_none()
+            }
+        }
+    )+};
+}
+
+impl_is_zero_option_of_nonzero!(
+    NonZeroU8,
+    NonZeroU16,
+    NonZeroU32,
+    NonZeroU64,
+    NonZeroU128,
+    NonZeroI8,
+    NonZeroI16,
+    NonZeroI32,
+    NonZeroI64,
+    NonZeroI128,
+    NonZeroUsize,
+    NonZeroIsize,
+);

rust/alloc/vec/partial_eq.rs

@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use crate::alloc::Allocator;
+#[cfg(not(no_global_oom_handling))]
+use crate::borrow::Cow;
+
+use super::Vec;
+
+macro_rules! __impl_slice_eq1 {
+    ([$($vars:tt)*] $lhs:ty, $rhs:ty $(where $ty:ty: $bound:ident)?, #[$stability:meta]) => {
+        #[$stability]
+        impl<T, U, $($vars)*> PartialEq<$rhs> for $lhs
+        where
+            T: PartialEq<U>,
+            $($ty: $bound)?
+        {
+            #[inline]
+            fn eq(&self, other: &$rhs) -> bool { self[..] == other[..] }
+            #[inline]
+            fn ne(&self, other: &$rhs) -> bool { self[..] != other[..] }
+        }
+    }
+}
+
+__impl_slice_eq1! { [A1: Allocator, A2: Allocator] Vec<T, A1>, Vec<U, A2>, #[stable(feature = "rust1", since = "1.0.0")] }
+__impl_slice_eq1! { [A: Allocator] Vec<T, A>, &[U], #[stable(feature = "rust1", since = "1.0.0")] }
+__impl_slice_eq1! { [A: Allocator] Vec<T, A>, &mut [U], #[stable(feature = "rust1", since = "1.0.0")] }
+__impl_slice_eq1! { [A: Allocator] &[T], Vec<U, A>, #[stable(feature = "partialeq_vec_for_ref_slice", since = "1.46.0")] }
+__impl_slice_eq1! { [A: Allocator] &mut [T], Vec<U, A>, #[stable(feature = "partialeq_vec_for_ref_slice", since = "1.46.0")] }
+__impl_slice_eq1! { [A: Allocator] Vec<T, A>, [U], #[stable(feature = "partialeq_vec_for_slice", since = "1.48.0")]  }
+__impl_slice_eq1! { [A: Allocator] [T], Vec<U, A>, #[stable(feature = "partialeq_vec_for_slice", since = "1.48.0")]  }
+#[cfg(not(no_global_oom_handling))]
+__impl_slice_eq1! { [A: Allocator] Cow<'_, [T]>, Vec<U, A> where T: Clone, #[stable(feature = "rust1", since = "1.0.0")] }
+#[cfg(not(no_global_oom_handling))]
+__impl_slice_eq1! { [] Cow<'_, [T]>, &[U] where T: Clone, #[stable(feature = "rust1", since = "1.0.0")] }
+#[cfg(not(no_global_oom_handling))]
+__impl_slice_eq1! { [] Cow<'_, [T]>, &mut [U] where T: Clone, #[stable(feature = "rust1", since = "1.0.0")] }
+__impl_slice_eq1! { [A: Allocator, const N: usize] Vec<T, A>, [U; N], #[stable(feature = "rust1", since = "1.0.0")] }
+__impl_slice_eq1! { [A: Allocator, const N: usize] Vec<T, A>, &[U; N], #[stable(feature = "rust1", since = "1.0.0")] }
+
+// NOTE: some less important impls are omitted to reduce code bloat
+// FIXME(Centril): Reconsider this?
+//__impl_slice_eq1! { [const N: usize] Vec<A>, &mut [B; N], }
+//__impl_slice_eq1! { [const N: usize] [A; N], Vec<B>, }
+//__impl_slice_eq1! { [const N: usize] &[A; N], Vec<B>, }
+//__impl_slice_eq1! { [const N: usize] &mut [A; N], Vec<B>, }
+//__impl_slice_eq1! { [const N: usize] Cow<'a, [A]>, [B; N], }
+//__impl_slice_eq1! { [const N: usize] Cow<'a, [A]>, &[B; N], }
+//__impl_slice_eq1! { [const N: usize] Cow<'a, [A]>, &mut [B; N], }

rust/bindgen_parameters

@@ -0,0 +1,21 @@
+# SPDX-License-Identifier: GPL-2.0
+
+--opaque-type xregs_state
+--opaque-type desc_struct
+--opaque-type arch_lbr_state
+--opaque-type local_apic
+
+# Packed type cannot transitively contain a `#[repr(align)]` type.
+--opaque-type x86_msi_data
+--opaque-type x86_msi_addr_lo
+
+# `try` is a reserved keyword since Rust 2018; solved in `bindgen` v0.59.2,
+# commit 2aed6b021680 ("context: Escape the try keyword properly").
+--opaque-type kunit_try_catch
+
+# If SMP is disabled, `arch_spinlock_t` is defined as a ZST which triggers a Rust
+# warning. We don't need to peek into it anyway.
+--opaque-type spinlock
+
+# `seccomp`'s comment gets understood as a doctest
+--no-doc-comments

rust/bindings/bindings_helper.h

@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Header that contains the code (mostly headers) for which Rust bindings
+ * will be automatically generated by `bindgen`.
+ *
+ * Sorted alphabetically.
+ */
+
+#include <linux/slab.h>
+
+/* `bindgen` gets confused at certain things. */
+const gfp_t BINDINGS_GFP_KERNEL = GFP_KERNEL;
+const gfp_t BINDINGS___GFP_ZERO = __GFP_ZERO;

rust/bindings/lib.rs

@@ -0,0 +1,53 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Bindings.
+//!
+//! Imports the generated bindings by `bindgen`.
+//!
+//! This crate may not be directly used. If you need a kernel C API that is
+//! not ported or wrapped in the `kernel` crate, then do so first instead of
+//! using this crate.
+
+#![no_std]
+#![feature(core_ffi_c)]
+// See <https://github.com/rust-lang/rust-bindgen/issues/1651>.
+#![cfg_attr(test, allow(deref_nullptr))]
+#![cfg_attr(test, allow(unaligned_references))]
+#![cfg_attr(test, allow(unsafe_op_in_unsafe_fn))]
+#![allow(
+    clippy::all,
+    missing_docs,
+    non_camel_case_types,
+    non_upper_case_globals,
+    non_snake_case,
+    improper_ctypes,
+    unreachable_pub,
+    unsafe_op_in_unsafe_fn
+)]
+
+mod bindings_raw {
+    // Use glob import here to expose all helpers.
+    // Symbols defined within the module will take precedence to the glob import.
+    pub use super::bindings_helper::*;
+    include!(concat!(
+        env!("OBJTREE"),
+        "/rust/bindings/bindings_generated.rs"
+    ));
+}
+
+// When both a directly exposed symbol and a helper exists for the same function,
+// the directly exposed symbol is preferred and the helper becomes dead code, so
+// ignore the warning here.
+#[allow(dead_code)]
+mod bindings_helper {
+    // Import the generated bindings for types.
+    include!(concat!(
+        env!("OBJTREE"),
+        "/rust/bindings/bindings_helpers_generated.rs"
+    ));
+}
+
+pub use bindings_raw::*;
+
+pub const GFP_KERNEL: gfp_t = BINDINGS_GFP_KERNEL;
+pub const __GFP_ZERO: gfp_t = BINDINGS___GFP_ZERO;

rust/compiler_builtins.rs

@@ -0,0 +1,63 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Our own `compiler_builtins`.
+//!
+//! Rust provides [`compiler_builtins`] as a port of LLVM's [`compiler-rt`].
+//! Since we do not need the vast majority of them, we avoid the dependency
+//! by providing this file.
+//!
+//! At the moment, some builtins are required that should not be. For instance,
+//! [`core`] has 128-bit integers functionality which we should not be compiling
+//! in. We will work with upstream [`core`] to provide feature flags to disable
+//! the parts we do not need. For the moment, we define them to [`panic!`] at
+//! runtime for simplicity to catch mistakes, instead of performing surgery
+//! on `core.o`.
+//!
+//! In any case, all these symbols are weakened to ensure we do not override
+//! those that may be provided by the rest of the kernel.
+//!
+//! [`compiler_builtins`]: https://github.com/rust-lang/compiler-builtins
+//! [`compiler-rt`]: https://compiler-rt.llvm.org/
+
+#![feature(compiler_builtins)]
+#![compiler_builtins]
+#![no_builtins]
+#![no_std]
+
+macro_rules! define_panicking_intrinsics(
+    ($reason: tt, { $($ident: ident, )* }) => {
+        $(
+            #[doc(hidden)]
+            #[no_mangle]
+            pub extern "C" fn $ident() {
+                panic!($reason);
+            }
+        )*
+    }
+);
+
+define_panicking_intrinsics!("`f32` should not be used", {
+    __eqsf2,
+    __gesf2,
+    __lesf2,
+    __nesf2,
+    __unordsf2,
+});
+
+define_panicking_intrinsics!("`f64` should not be used", {
+    __unorddf2,
+});
+
+define_panicking_intrinsics!("`i128` should not be used", {
+    __ashrti3,
+    __muloti4,
+    __multi3,
+});
+
+define_panicking_intrinsics!("`u128` should not be used", {
+    __ashlti3,
+    __lshrti3,
+    __udivmodti4,
+    __udivti3,
+    __umodti3,
+});

rust/exports.c

@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * A hack to export Rust symbols for loadable modules without having to redo
+ * the entire `include/linux/export.h` logic in Rust.
+ *
+ * This requires the Rust's new/future `v0` mangling scheme because the default
+ * one ("legacy") uses invalid characters for C identifiers (thus we cannot use
+ * the `EXPORT_SYMBOL_*` macros).
+ *
+ * All symbols are exported as GPL-only to guarantee no GPL-only feature is
+ * accidentally exposed.
+ */
+
+#include <linux/module.h>
+
+#define EXPORT_SYMBOL_RUST_GPL(sym) extern int sym; EXPORT_SYMBOL_GPL(sym)
+
+#include "exports_core_generated.h"
+#include "exports_alloc_generated.h"
+#include "exports_bindings_generated.h"
+#include "exports_kernel_generated.h"

rust/helpers.c

@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Non-trivial C macros cannot be used in Rust. Similarly, inlined C functions
+ * cannot be called either. This file explicitly creates functions ("helpers")
+ * that wrap those so that they can be called from Rust.
+ *
+ * Even though Rust kernel modules should never use directly the bindings, some
+ * of these helpers need to be exported because Rust generics and inlined
+ * functions may not get their code generated in the crate where they are
+ * defined. Other helpers, called from non-inline functions, may not be
+ * exported, in principle. However, in general, the Rust compiler does not
+ * guarantee codegen will be performed for a non-inline function either.
+ * Therefore, this file exports all the helpers. In the future, this may be
+ * revisited to reduce the number of exports after the compiler is informed
+ * about the places codegen is required.
+ *
+ * All symbols are exported as GPL-only to guarantee no GPL-only feature is
+ * accidentally exposed.
+ */
+
+#include <linux/bug.h>
+#include <linux/build_bug.h>
+
+__noreturn void rust_helper_BUG(void)
+{
+	BUG();
+}
+EXPORT_SYMBOL_GPL(rust_helper_BUG);
+
+/*
+ * We use `bindgen`'s `--size_t-is-usize` option to bind the C `size_t` type
+ * as the Rust `usize` type, so we can use it in contexts where Rust
+ * expects a `usize` like slice (array) indices. `usize` is defined to be
+ * the same as C's `uintptr_t` type (can hold any pointer) but not
+ * necessarily the same as `size_t` (can hold the size of any single
+ * object). Most modern platforms use the same concrete integer type for
+ * both of them, but in case we find ourselves on a platform where
+ * that's not true, fail early instead of risking ABI or
+ * integer-overflow issues.
+ *
+ * If your platform fails this assertion, it means that you are in
+ * danger of integer-overflow bugs (even if you attempt to remove
+ * `--size_t-is-usize`). It may be easiest to change the kernel ABI on
+ * your platform such that `size_t` matches `uintptr_t` (i.e., to increase
+ * `size_t`, because `uintptr_t` has to be at least as big as `size_t`).
+ */
+static_assert(
+	sizeof(size_t) == sizeof(uintptr_t) &&
+	__alignof__(size_t) == __alignof__(uintptr_t),
+	"Rust code expects C `size_t` to match Rust `usize`"
+);

rust/kernel/allocator.rs

@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Allocator support.
+
+use core::alloc::{GlobalAlloc, Layout};
+use core::ptr;
+
+use crate::bindings;
+
+struct KernelAllocator;
+
+unsafe impl GlobalAlloc for KernelAllocator {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        // `krealloc()` is used instead of `kmalloc()` because the latter is
+        // an inline function and cannot be bound to as a result.
+        unsafe { bindings::krealloc(ptr::null(), layout.size(), bindings::GFP_KERNEL) as *mut u8 }
+    }
+
+    unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {
+        unsafe {
+            bindings::kfree(ptr as *const core::ffi::c_void);
+        }
+    }
+}
+
+#[global_allocator]
+static ALLOCATOR: KernelAllocator = KernelAllocator;
+
+// `rustc` only generates these for some crate types. Even then, we would need
+// to extract the object file that has them from the archive. For the moment,
+// let's generate them ourselves instead.
+//
+// Note that `#[no_mangle]` implies exported too, nowadays.
+#[no_mangle]
+fn __rust_alloc(size: usize, _align: usize) -> *mut u8 {
+    unsafe { bindings::krealloc(core::ptr::null(), size, bindings::GFP_KERNEL) as *mut u8 }
+}
+
+#[no_mangle]
+fn __rust_dealloc(ptr: *mut u8, _size: usize, _align: usize) {
+    unsafe { bindings::kfree(ptr as *const core::ffi::c_void) };
+}
+
+#[no_mangle]
+fn __rust_realloc(ptr: *mut u8, _old_size: usize, _align: usize, new_size: usize) -> *mut u8 {
+    unsafe {
+        bindings::krealloc(
+            ptr as *const core::ffi::c_void,
+            new_size,
+            bindings::GFP_KERNEL,
+        ) as *mut u8
+    }
+}
+
+#[no_mangle]
+fn __rust_alloc_zeroed(size: usize, _align: usize) -> *mut u8 {
+    unsafe {
+        bindings::krealloc(
+            core::ptr::null(),
+            size,
+            bindings::GFP_KERNEL | bindings::__GFP_ZERO,
+        ) as *mut u8
+    }
+}

rust/kernel/error.rs

@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Kernel errors.
+//!
+//! C header: [`include/uapi/asm-generic/errno-base.h`](../../../include/uapi/asm-generic/errno-base.h)
+
+use alloc::collections::TryReserveError;
+
+/// Contains the C-compatible error codes.
+pub mod code {
+    /// Out of memory.
+    pub const ENOMEM: super::Error = super::Error(-(crate::bindings::ENOMEM as i32));
+}
+
+/// Generic integer kernel error.
+///
+/// The kernel defines a set of integer generic error codes based on C and
+/// POSIX ones. These codes may have a more specific meaning in some contexts.
+///
+/// # Invariants
+///
+/// The value is a valid `errno` (i.e. `>= -MAX_ERRNO && < 0`).
+#[derive(Clone, Copy, PartialEq, Eq)]
+pub struct Error(core::ffi::c_int);
+
+impl Error {
+    /// Returns the kernel error code.
+    pub fn to_kernel_errno(self) -> core::ffi::c_int {
+        self.0
+    }
+}
+
+impl From<TryReserveError> for Error {
+    fn from(_: TryReserveError) -> Error {
+        code::ENOMEM
+    }
+}
+
+/// A [`Result`] with an [`Error`] error type.
+///
+/// To be used as the return type for functions that may fail.
+///
+/// # Error codes in C and Rust
+///
+/// In C, it is common that functions indicate success or failure through
+/// their return value; modifying or returning extra data through non-`const`
+/// pointer parameters. In particular, in the kernel, functions that may fail
+/// typically return an `int` that represents a generic error code. We model
+/// those as [`Error`].
+///
+/// In Rust, it is idiomatic to model functions that may fail as returning
+/// a [`Result`]. Since in the kernel many functions return an error code,
+/// [`Result`] is a type alias for a [`core::result::Result`] that uses
+/// [`Error`] as its error type.
+///
+/// Note that even if a function does not return anything when it succeeds,
+/// it should still be modeled as returning a `Result` rather than
+/// just an [`Error`].
+pub type Result<T = ()> = core::result::Result<T, Error>;

rust/kernel/lib.rs

@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! The `kernel` crate.
+//!
+//! This crate contains the kernel APIs that have been ported or wrapped for
+//! usage by Rust code in the kernel and is shared by all of them.
+//!
+//! In other words, all the rest of the Rust code in the kernel (e.g. kernel
+//! modules written in Rust) depends on [`core`], [`alloc`] and this crate.
+//!
+//! If you need a kernel C API that is not ported or wrapped yet here, then
+//! do so first instead of bypassing this crate.
+
+#![no_std]
+#![feature(core_ffi_c)]
+
+// Ensure conditional compilation based on the kernel configuration works;
+// otherwise we may silently break things like initcall handling.
+#[cfg(not(CONFIG_RUST))]
+compile_error!("Missing kernel configuration for conditional compilation");
+
+#[cfg(not(test))]
+#[cfg(not(testlib))]
+mod allocator;
+pub mod error;
+pub mod prelude;
+pub mod print;
+pub mod str;
+
+#[doc(hidden)]
+pub use bindings;
+pub use macros;
+
+/// Prefix to appear before log messages printed from within the `kernel` crate.
+const __LOG_PREFIX: &[u8] = b"rust_kernel\0";
+
+/// The top level entrypoint to implementing a kernel module.
+///
+/// For any teardown or cleanup operations, your type may implement [`Drop`].
+pub trait Module: Sized + Sync {
+    /// Called at module initialization time.
+    ///
+    /// Use this method to perform whatever setup or registration your module
+    /// should do.
+    ///
+    /// Equivalent to the `module_init` macro in the C API.
+    fn init(module: &'static ThisModule) -> error::Result<Self>;
+}
+
+/// Equivalent to `THIS_MODULE` in the C API.
+///
+/// C header: `include/linux/export.h`
+pub struct ThisModule(*mut bindings::module);
+
+// SAFETY: `THIS_MODULE` may be used from all threads within a module.
+unsafe impl Sync for ThisModule {}
+
+impl ThisModule {
+    /// Creates a [`ThisModule`] given the `THIS_MODULE` pointer.
+    ///
+    /// # Safety
+    ///
+    /// The pointer must be equal to the right `THIS_MODULE`.
+    pub const unsafe fn from_ptr(ptr: *mut bindings::module) -> ThisModule {
+        ThisModule(ptr)
+    }
+}
+
+#[cfg(not(any(testlib, test)))]
+#[panic_handler]
+fn panic(info: &core::panic::PanicInfo<'_>) -> ! {
+    pr_emerg!("{}\n", info);
+    // SAFETY: FFI call.
+    unsafe { bindings::BUG() };
+    // Bindgen currently does not recognize `__noreturn` so `BUG` returns `()`
+    // instead of `!`. See <https://github.com/rust-lang/rust-bindgen/issues/2094>.
+    loop {}
+}

rust/kernel/prelude.rs

@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! The `kernel` prelude.
+//!
+//! These are the most common items used by Rust code in the kernel,
+//! intended to be imported by all Rust code, for convenience.
+//!
+//! # Examples
+//!
+//! ```
+//! use kernel::prelude::*;
+//! ```
+
+pub use super::{
+    error::{Error, Result},
+    pr_emerg, pr_info, ThisModule,
+};
+pub use alloc::{boxed::Box, vec::Vec};
+pub use core::pin::Pin;
+pub use macros::module;

rust/kernel/print.rs

@@ -0,0 +1,198 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Printing facilities.
+//!
+//! C header: [`include/linux/printk.h`](../../../../include/linux/printk.h)
+//!
+//! Reference: <https://www.kernel.org/doc/html/latest/core-api/printk-basics.html>
+
+use core::{
+    ffi::{c_char, c_void},
+    fmt,
+};
+
+use crate::str::RawFormatter;
+
+#[cfg(CONFIG_PRINTK)]
+use crate::bindings;
+
+// Called from `vsprintf` with format specifier `%pA`.
+#[no_mangle]
+unsafe fn rust_fmt_argument(buf: *mut c_char, end: *mut c_char, ptr: *const c_void) -> *mut c_char {
+    use fmt::Write;
+    // SAFETY: The C contract guarantees that `buf` is valid if it's less than `end`.
+    let mut w = unsafe { RawFormatter::from_ptrs(buf.cast(), end.cast()) };
+    let _ = w.write_fmt(unsafe { *(ptr as *const fmt::Arguments<'_>) });
+    w.pos().cast()
+}
+
+/// Format strings.
+///
+/// Public but hidden since it should only be used from public macros.
+#[doc(hidden)]
+pub mod format_strings {
+    use crate::bindings;
+
+    /// The length we copy from the `KERN_*` kernel prefixes.
+    const LENGTH_PREFIX: usize = 2;
+
+    /// The length of the fixed format strings.
+    pub const LENGTH: usize = 10;
+
+    /// Generates a fixed format string for the kernel's [`_printk`].
+    ///
+    /// The format string is always the same for a given level, i.e. for a
+    /// given `prefix`, which are the kernel's `KERN_*` constants.
+    ///
+    /// [`_printk`]: ../../../../include/linux/printk.h
+    const fn generate(is_cont: bool, prefix: &[u8; 3]) -> [u8; LENGTH] {
+        // Ensure the `KERN_*` macros are what we expect.
+        assert!(prefix[0] == b'\x01');
+        if is_cont {
+            assert!(prefix[1] == b'c');
+        } else {
+            assert!(prefix[1] >= b'0' && prefix[1] <= b'7');
+        }
+        assert!(prefix[2] == b'\x00');
+
+        let suffix: &[u8; LENGTH - LENGTH_PREFIX] = if is_cont {
+            b"%pA\0\0\0\0\0"
+        } else {
+            b"%s: %pA\0"
+        };
+
+        [
+            prefix[0], prefix[1], suffix[0], suffix[1], suffix[2], suffix[3], suffix[4], suffix[5],
+            suffix[6], suffix[7],
+        ]
+    }
+
+    // Generate the format strings at compile-time.
+    //
+    // This avoids the compiler generating the contents on the fly in the stack.
+    //
+    // Furthermore, `static` instead of `const` is used to share the strings
+    // for all the kernel.
+    pub static EMERG: [u8; LENGTH] = generate(false, bindings::KERN_EMERG);
+    pub static INFO: [u8; LENGTH] = generate(false, bindings::KERN_INFO);
+}
+
+/// Prints a message via the kernel's [`_printk`].
+///
+/// Public but hidden since it should only be used from public macros.
+///
+/// # Safety
+///
+/// The format string must be one of the ones in [`format_strings`], and
+/// the module name must be null-terminated.
+///
+/// [`_printk`]: ../../../../include/linux/_printk.h
+#[doc(hidden)]
+#[cfg_attr(not(CONFIG_PRINTK), allow(unused_variables))]
+pub unsafe fn call_printk(
+    format_string: &[u8; format_strings::LENGTH],
+    module_name: &[u8],
+    args: fmt::Arguments<'_>,
+) {
+    // `_printk` does not seem to fail in any path.
+    #[cfg(CONFIG_PRINTK)]
+    unsafe {
+        bindings::_printk(
+            format_string.as_ptr() as _,
+            module_name.as_ptr(),
+            &args as *const _ as *const c_void,
+        );
+    }
+}
+
+/// Performs formatting and forwards the string to [`call_printk`].
+///
+/// Public but hidden since it should only be used from public macros.
+#[doc(hidden)]
+#[cfg(not(testlib))]
+#[macro_export]
+#[allow(clippy::crate_in_macro_def)]
+macro_rules! print_macro (
+    // The non-continuation cases (most of them, e.g. `INFO`).
+    ($format_string:path, $($arg:tt)+) => (
+        // SAFETY: This hidden macro should only be called by the documented
+        // printing macros which ensure the format string is one of the fixed
+        // ones. All `__LOG_PREFIX`s are null-terminated as they are generated
+        // by the `module!` proc macro or fixed values defined in a kernel
+        // crate.
+        unsafe {
+            $crate::print::call_printk(
+                &$format_string,
+                crate::__LOG_PREFIX,
+                format_args!($($arg)+),
+            );
+        }
+    );
+);
+
+/// Stub for doctests
+#[cfg(testlib)]
+#[macro_export]
+macro_rules! print_macro (
+    ($format_string:path, $e:expr, $($arg:tt)+) => (
+        ()
+    );
+);
+
+// We could use a macro to generate these macros. However, doing so ends
+// up being a bit ugly: it requires the dollar token trick to escape `$` as
+// well as playing with the `doc` attribute. Furthermore, they cannot be easily
+// imported in the prelude due to [1]. So, for the moment, we just write them
+// manually, like in the C side; while keeping most of the logic in another
+// macro, i.e. [`print_macro`].
+//
+// [1]: https://github.com/rust-lang/rust/issues/52234
+
+/// Prints an emergency-level message (level 0).
+///
+/// Use this level if the system is unusable.
+///
+/// Equivalent to the kernel's [`pr_emerg`] macro.
+///
+/// Mimics the interface of [`std::print!`]. See [`core::fmt`] and
+/// `alloc::format!` for information about the formatting syntax.
+///
+/// [`pr_emerg`]: https://www.kernel.org/doc/html/latest/core-api/printk-basics.html#c.pr_emerg
+/// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html
+///
+/// # Examples
+///
+/// ```
+/// pr_emerg!("hello {}\n", "there");
+/// ```
+#[macro_export]
+macro_rules! pr_emerg (
+    ($($arg:tt)*) => (
+        $crate::print_macro!($crate::print::format_strings::EMERG, $($arg)*)
+    )
+);
+
+/// Prints an info-level message (level 6).
+///
+/// Use this level for informational messages.
+///
+/// Equivalent to the kernel's [`pr_info`] macro.
+///
+/// Mimics the interface of [`std::print!`]. See [`core::fmt`] and
+/// `alloc::format!` for information about the formatting syntax.
+///
+/// [`pr_info`]: https://www.kernel.org/doc/html/latest/core-api/printk-basics.html#c.pr_info
+/// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html
+///
+/// # Examples
+///
+/// ```
+/// pr_info!("hello {}\n", "there");
+/// ```
+#[macro_export]
+#[doc(alias = "print")]
+macro_rules! pr_info (
+    ($($arg:tt)*) => (
+        $crate::print_macro!($crate::print::format_strings::INFO, $($arg)*)
+    )
+);

rust/kernel/str.rs

@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! String representations.
+
+use core::fmt;
+
+/// Allows formatting of [`fmt::Arguments`] into a raw buffer.
+///
+/// It does not fail if callers write past the end of the buffer so that they can calculate the
+/// size required to fit everything.
+///
+/// # Invariants
+///
+/// The memory region between `pos` (inclusive) and `end` (exclusive) is valid for writes if `pos`
+/// is less than `end`.
+pub(crate) struct RawFormatter {
+    // Use `usize` to use `saturating_*` functions.
+    #[allow(dead_code)]
+    beg: usize,
+    pos: usize,
+    end: usize,
+}
+
+impl RawFormatter {
+    /// Creates a new instance of [`RawFormatter`] with the given buffer pointers.
+    ///
+    /// # Safety
+    ///
+    /// If `pos` is less than `end`, then the region between `pos` (inclusive) and `end`
+    /// (exclusive) must be valid for writes for the lifetime of the returned [`RawFormatter`].
+    pub(crate) unsafe fn from_ptrs(pos: *mut u8, end: *mut u8) -> Self {
+        // INVARIANT: The safety requierments guarantee the type invariants.
+        Self {
+            beg: pos as _,
+            pos: pos as _,
+            end: end as _,
+        }
+    }
+
+    /// Returns the current insert position.
+    ///
+    /// N.B. It may point to invalid memory.
+    pub(crate) fn pos(&self) -> *mut u8 {
+        self.pos as _
+    }
+}
+
+impl fmt::Write for RawFormatter {
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        // `pos` value after writing `len` bytes. This does not have to be bounded by `end`, but we
+        // don't want it to wrap around to 0.
+        let pos_new = self.pos.saturating_add(s.len());
+
+        // Amount that we can copy. `saturating_sub` ensures we get 0 if `pos` goes past `end`.
+        let len_to_copy = core::cmp::min(pos_new, self.end).saturating_sub(self.pos);
+
+        if len_to_copy > 0 {
+            // SAFETY: If `len_to_copy` is non-zero, then we know `pos` has not gone past `end`
+            // yet, so it is valid for write per the type invariants.
+            unsafe {
+                core::ptr::copy_nonoverlapping(
+                    s.as_bytes().as_ptr(),
+                    self.pos as *mut u8,
+                    len_to_copy,
+                )
+            };
+        }
+
+        self.pos = pos_new;
+        Ok(())
+    }
+}

rust/macros/helpers.rs

@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use proc_macro::{token_stream, TokenTree};
+
+pub(crate) fn try_ident(it: &mut token_stream::IntoIter) -> Option<String> {
+    if let Some(TokenTree::Ident(ident)) = it.next() {
+        Some(ident.to_string())
+    } else {
+        None
+    }
+}
+
+pub(crate) fn try_literal(it: &mut token_stream::IntoIter) -> Option<String> {
+    if let Some(TokenTree::Literal(literal)) = it.next() {
+        Some(literal.to_string())
+    } else {
+        None
+    }
+}
+
+pub(crate) fn try_byte_string(it: &mut token_stream::IntoIter) -> Option<String> {
+    try_literal(it).and_then(|byte_string| {
+        if byte_string.starts_with("b\"") && byte_string.ends_with('\"') {
+            Some(byte_string[2..byte_string.len() - 1].to_string())
+        } else {
+            None
+        }
+    })
+}
+
+pub(crate) fn expect_ident(it: &mut token_stream::IntoIter) -> String {
+    try_ident(it).expect("Expected Ident")
+}
+
+pub(crate) fn expect_punct(it: &mut token_stream::IntoIter) -> char {
+    if let TokenTree::Punct(punct) = it.next().expect("Reached end of token stream for Punct") {
+        punct.as_char()
+    } else {
+        panic!("Expected Punct");
+    }
+}
+
+pub(crate) fn expect_byte_string(it: &mut token_stream::IntoIter) -> String {
+    try_byte_string(it).expect("Expected byte string")
+}
+
+pub(crate) fn expect_end(it: &mut token_stream::IntoIter) {
+    if it.next().is_some() {
+        panic!("Expected end");
+    }
+}

rust/macros/lib.rs

@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Crate for all kernel procedural macros.
+
+mod helpers;
+mod module;
+
+use proc_macro::TokenStream;
+
+/// Declares a kernel module.
+///
+/// The `type` argument should be a type which implements the [`Module`]
+/// trait. Also accepts various forms of kernel metadata.
+///
+/// C header: [`include/linux/moduleparam.h`](../../../include/linux/moduleparam.h)
+///
+/// [`Module`]: ../kernel/trait.Module.html
+///
+/// # Examples
+///
+/// ```ignore
+/// use kernel::prelude::*;
+///
+/// module!{
+///     type: MyModule,
+///     name: b"my_kernel_module",
+///     author: b"Rust for Linux Contributors",
+///     description: b"My very own kernel module!",
+///     license: b"GPL",
+///     params: {
+///        my_i32: i32 {
+///            default: 42,
+///            permissions: 0o000,
+///            description: b"Example of i32",
+///        },
+///        writeable_i32: i32 {
+///            default: 42,
+///            permissions: 0o644,
+///            description: b"Example of i32",
+///        },
+///    },
+/// }
+///
+/// struct MyModule;
+///
+/// impl kernel::Module for MyModule {
+///     fn init() -> Result<Self> {
+///         // If the parameter is writeable, then the kparam lock must be
+///         // taken to read the parameter:
+///         {
+///             let lock = THIS_MODULE.kernel_param_lock();
+///             pr_info!("i32 param is:  {}\n", writeable_i32.read(&lock));
+///         }
+///         // If the parameter is read only, it can be read without locking
+///         // the kernel parameters:
+///         pr_info!("i32 param is:  {}\n", my_i32.read());
+///         Ok(Self)
+///     }
+/// }
+/// ```
+///
+/// # Supported argument types
+///   - `type`: type which implements the [`Module`] trait (required).
+///   - `name`: byte array of the name of the kernel module (required).
+///   - `author`: byte array of the author of the kernel module.
+///   - `description`: byte array of the description of the kernel module.
+///   - `license`: byte array of the license of the kernel module (required).
+///   - `alias`: byte array of alias name of the kernel module.
+#[proc_macro]
+pub fn module(ts: TokenStream) -> TokenStream {
+    module::module(ts)
+}

rust/macros/module.rs

@@ -0,0 +1,282 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use crate::helpers::*;
+use proc_macro::{token_stream, Literal, TokenStream, TokenTree};
+use std::fmt::Write;
+
+struct ModInfoBuilder<'a> {
+    module: &'a str,
+    counter: usize,
+    buffer: String,
+}
+
+impl<'a> ModInfoBuilder<'a> {
+    fn new(module: &'a str) -> Self {
+        ModInfoBuilder {
+            module,
+            counter: 0,
+            buffer: String::new(),
+        }
+    }
+
+    fn emit_base(&mut self, field: &str, content: &str, builtin: bool) {
+        let string = if builtin {
+            // Built-in modules prefix their modinfo strings by `module.`.
+            format!(
+                "{module}.{field}={content}\0",
+                module = self.module,
+                field = field,
+                content = content
+            )
+        } else {
+            // Loadable modules' modinfo strings go as-is.
+            format!("{field}={content}\0", field = field, content = content)
+        };
+
+        write!(
+            &mut self.buffer,
+            "
+                {cfg}
+                #[doc(hidden)]
+                #[link_section = \".modinfo\"]
+                #[used]
+                pub static __{module}_{counter}: [u8; {length}] = *{string};
+            ",
+            cfg = if builtin {
+                "#[cfg(not(MODULE))]"
+            } else {
+                "#[cfg(MODULE)]"
+            },
+            module = self.module.to_uppercase(),
+            counter = self.counter,
+            length = string.len(),
+            string = Literal::byte_string(string.as_bytes()),
+        )
+        .unwrap();
+
+        self.counter += 1;
+    }
+
+    fn emit_only_builtin(&mut self, field: &str, content: &str) {
+        self.emit_base(field, content, true)
+    }
+
+    fn emit_only_loadable(&mut self, field: &str, content: &str) {
+        self.emit_base(field, content, false)
+    }
+
+    fn emit(&mut self, field: &str, content: &str) {
+        self.emit_only_builtin(field, content);
+        self.emit_only_loadable(field, content);
+    }
+}
+
+#[derive(Debug, Default)]
+struct ModuleInfo {
+    type_: String,
+    license: String,
+    name: String,
+    author: Option<String>,
+    description: Option<String>,
+    alias: Option<String>,
+}
+
+impl ModuleInfo {
+    fn parse(it: &mut token_stream::IntoIter) -> Self {
+        let mut info = ModuleInfo::default();
+
+        const EXPECTED_KEYS: &[&str] =
+            &["type", "name", "author", "description", "license", "alias"];
+        const REQUIRED_KEYS: &[&str] = &["type", "name", "license"];
+        let mut seen_keys = Vec::new();
+
+        loop {
+            let key = match it.next() {
+                Some(TokenTree::Ident(ident)) => ident.to_string(),
+                Some(_) => panic!("Expected Ident or end"),
+                None => break,
+            };
+
+            if seen_keys.contains(&key) {
+                panic!(
+                    "Duplicated key \"{}\". Keys can only be specified once.",
+                    key
+                );
+            }
+
+            assert_eq!(expect_punct(it), ':');
+
+            match key.as_str() {
+                "type" => info.type_ = expect_ident(it),
+                "name" => info.name = expect_byte_string(it),
+                "author" => info.author = Some(expect_byte_string(it)),
+                "description" => info.description = Some(expect_byte_string(it)),
+                "license" => info.license = expect_byte_string(it),
+                "alias" => info.alias = Some(expect_byte_string(it)),
+                _ => panic!(
+                    "Unknown key \"{}\". Valid keys are: {:?}.",
+                    key, EXPECTED_KEYS
+                ),
+            }
+
+            assert_eq!(expect_punct(it), ',');
+
+            seen_keys.push(key);
+        }
+
+        expect_end(it);
+
+        for key in REQUIRED_KEYS {
+            if !seen_keys.iter().any(|e| e == key) {
+                panic!("Missing required key \"{}\".", key);
+            }
+        }
+
+        let mut ordered_keys: Vec<&str> = Vec::new();
+        for key in EXPECTED_KEYS {
+            if seen_keys.iter().any(|e| e == key) {
+                ordered_keys.push(key);
+            }
+        }
+
+        if seen_keys != ordered_keys {
+            panic!(
+                "Keys are not ordered as expected. Order them like: {:?}.",
+                ordered_keys
+            );
+        }
+
+        info
+    }
+}
+
+pub(crate) fn module(ts: TokenStream) -> TokenStream {
+    let mut it = ts.into_iter();
+
+    let info = ModuleInfo::parse(&mut it);
+
+    let mut modinfo = ModInfoBuilder::new(info.name.as_ref());
+    if let Some(author) = info.author {
+        modinfo.emit("author", &author);
+    }
+    if let Some(description) = info.description {
+        modinfo.emit("description", &description);
+    }
+    modinfo.emit("license", &info.license);
+    if let Some(alias) = info.alias {
+        modinfo.emit("alias", &alias);
+    }
+
+    // Built-in modules also export the `file` modinfo string.
+    let file =
+        std::env::var("RUST_MODFILE").expect("Unable to fetch RUST_MODFILE environmental variable");
+    modinfo.emit_only_builtin("file", &file);
+
+    format!(
+        "
+            /// The module name.
+            ///
+            /// Used by the printing macros, e.g. [`info!`].
+            const __LOG_PREFIX: &[u8] = b\"{name}\\0\";
+
+            /// The \"Rust loadable module\" mark, for `scripts/is_rust_module.sh`.
+            //
+            // This may be best done another way later on, e.g. as a new modinfo
+            // key or a new section. For the moment, keep it simple.
+            #[cfg(MODULE)]
+            #[doc(hidden)]
+            #[used]
+            static __IS_RUST_MODULE: () = ();
+
+            static mut __MOD: Option<{type_}> = None;
+
+            // SAFETY: `__this_module` is constructed by the kernel at load time and will not be
+            // freed until the module is unloaded.
+            #[cfg(MODULE)]
+            static THIS_MODULE: kernel::ThisModule = unsafe {{
+                kernel::ThisModule::from_ptr(&kernel::bindings::__this_module as *const _ as *mut _)
+            }};
+            #[cfg(not(MODULE))]
+            static THIS_MODULE: kernel::ThisModule = unsafe {{
+                kernel::ThisModule::from_ptr(core::ptr::null_mut())
+            }};
+
+            // Loadable modules need to export the `{{init,cleanup}}_module` identifiers.
+            #[cfg(MODULE)]
+            #[doc(hidden)]
+            #[no_mangle]
+            pub extern \"C\" fn init_module() -> core::ffi::c_int {{
+                __init()
+            }}
+
+            #[cfg(MODULE)]
+            #[doc(hidden)]
+            #[no_mangle]
+            pub extern \"C\" fn cleanup_module() {{
+                __exit()
+            }}
+
+            // Built-in modules are initialized through an initcall pointer
+            // and the identifiers need to be unique.
+            #[cfg(not(MODULE))]
+            #[cfg(not(CONFIG_HAVE_ARCH_PREL32_RELOCATIONS))]
+            #[doc(hidden)]
+            #[link_section = \"{initcall_section}\"]
+            #[used]
+            pub static __{name}_initcall: extern \"C\" fn() -> core::ffi::c_int = __{name}_init;
+
+            #[cfg(not(MODULE))]
+            #[cfg(CONFIG_HAVE_ARCH_PREL32_RELOCATIONS)]
+            core::arch::global_asm!(
+                r#\".section \"{initcall_section}\", \"a\"
+                __{name}_initcall:
+                    .long   __{name}_init - .
+                    .previous
+                \"#
+            );
+
+            #[cfg(not(MODULE))]
+            #[doc(hidden)]
+            #[no_mangle]
+            pub extern \"C\" fn __{name}_init() -> core::ffi::c_int {{
+                __init()
+            }}
+
+            #[cfg(not(MODULE))]
+            #[doc(hidden)]
+            #[no_mangle]
+            pub extern \"C\" fn __{name}_exit() {{
+                __exit()
+            }}
+
+            fn __init() -> core::ffi::c_int {{
+                match <{type_} as kernel::Module>::init(&THIS_MODULE) {{
+                    Ok(m) => {{
+                        unsafe {{
+                            __MOD = Some(m);
+                        }}
+                        return 0;
+                    }}
+                    Err(e) => {{
+                        return e.to_kernel_errno();
+                    }}
+                }}
+            }}
+
+            fn __exit() {{
+                unsafe {{
+                    // Invokes `drop()` on `__MOD`, which should be used for cleanup.
+                    __MOD = None;
+                }}
+            }}
+
+            {modinfo}
+        ",
+        type_ = info.type_,
+        name = info.name,
+        modinfo = modinfo.buffer,
+        initcall_section = ".initcall6.init"
+    )
+    .parse()
+    .expect("Error parsing formatted string into token stream.")
+}

samples/Kconfig

@@ -263,6 +263,8 @@ config SAMPLE_CORESIGHT_SYSCFG
 	  This demonstrates how a user may create their own CoreSight
 	  configurations and easily load them into the system at runtime.
 
+source "samples/rust/Kconfig"
+
 endif # SAMPLES
 
 config HAVE_SAMPLE_FTRACE_DIRECT

samples/Makefile

@@ -35,3 +35,4 @@ subdir-$(CONFIG_SAMPLE_WATCH_QUEUE)	+= watch_queue
 obj-$(CONFIG_DEBUG_KMEMLEAK_TEST)	+= kmemleak/
 obj-$(CONFIG_SAMPLE_CORESIGHT_SYSCFG)	+= coresight/
 obj-$(CONFIG_SAMPLE_FPROBE)		+= fprobe/
+obj-$(CONFIG_SAMPLES_RUST)		+= rust/

samples/rust/Kconfig

@@ -0,0 +1,30 @@
+# SPDX-License-Identifier: GPL-2.0
+
+menuconfig SAMPLES_RUST
+	bool "Rust samples"
+	depends on RUST
+	help
+	  You can build sample Rust kernel code here.
+
+	  If unsure, say N.
+
+if SAMPLES_RUST
+
+config SAMPLE_RUST_MINIMAL
+	tristate "Minimal"
+	help
+	  This option builds the Rust minimal module sample.
+
+	  To compile this as a module, choose M here:
+	  the module will be called rust_minimal.
+
+	  If unsure, say N.
+
+config SAMPLE_RUST_HOSTPROGS
+	bool "Host programs"
+	help
+	  This option builds the Rust host program samples.
+
+	  If unsure, say N.
+
+endif # SAMPLES_RUST

samples/rust/Makefile

@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_SAMPLE_RUST_MINIMAL)		+= rust_minimal.o
+
+subdir-$(CONFIG_SAMPLE_RUST_HOSTPROGS)		+= hostprogs

samples/rust/hostprogs/.gitignore

@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+
+single

samples/rust/hostprogs/Makefile

@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0
+
+hostprogs-always-y := single
+
+single-rust := y

samples/rust/hostprogs/a.rs

@@ -0,0 +1,7 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust single host program sample: module `a`.
+
+pub(crate) fn f(x: i32) {
+    println!("The number is {}.", x);
+}

samples/rust/hostprogs/b.rs

@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust single host program sample: module `b`.
+
+pub(crate) const CONSTANT: i32 = 42;

samples/rust/hostprogs/single.rs

@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust single host program sample.
+
+mod a;
+mod b;
+
+fn main() {
+    println!("Hello world!");
+
+    a::f(b::CONSTANT);
+}

samples/rust/rust_minimal.rs

@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust minimal sample.
+
+use kernel::prelude::*;
+
+module! {
+    type: RustMinimal,
+    name: b"rust_minimal",
+    author: b"Rust for Linux Contributors",
+    description: b"Rust minimal sample",
+    license: b"GPL",
+}
+
+struct RustMinimal {
+    numbers: Vec<i32>,
+}
+
+impl kernel::Module for RustMinimal {
+    fn init(_module: &'static ThisModule) -> Result<Self> {
+        pr_info!("Rust minimal sample (init)\n");
+        pr_info!("Am I built-in? {}\n", !cfg!(MODULE));
+
+        let mut numbers = Vec::new();
+        numbers.try_push(72)?;
+        numbers.try_push(108)?;
+        numbers.try_push(200)?;
+
+        Ok(RustMinimal { numbers })
+    }
+}
+
+impl Drop for RustMinimal {
+    fn drop(&mut self) {
+        pr_info!("My numbers are {:?}\n", self.numbers);
+        pr_info!("Rust minimal sample (exit)\n");
+    }
+}

scripts/.gitignore

@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0-only
 /asn1_compiler
 /bin2c
+/generate_rust_target
 /insert-sys-cert
 /kallsyms
 /module.lds

scripts/Kconfig.include

@@ -36,12 +36,12 @@ ld-option = $(success,$(LD) -v $(1))
 as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) -c -x assembler -o /dev/null -)
 
 # check if $(CC) and $(LD) exist
-$(error-if,$(failure,command -v $(CC)),compiler '$(CC)' not found)
+$(error-if,$(failure,command -v $(CC)),C compiler '$(CC)' not found)
 $(error-if,$(failure,command -v $(LD)),linker '$(LD)' not found)
 
-# Get the compiler name, version, and error out if it is not supported.
+# Get the C compiler name, version, and error out if it is not supported.
 cc-info := $(shell,$(srctree)/scripts/cc-version.sh $(CC))
-$(error-if,$(success,test -z "$(cc-info)"),Sorry$(comma) this compiler is not supported.)
+$(error-if,$(success,test -z "$(cc-info)"),Sorry$(comma) this C compiler is not supported.)
 cc-name := $(shell,set -- $(cc-info) && echo $1)
 cc-version := $(shell,set -- $(cc-info) && echo $2)
 

scripts/Makefile

@@ -10,6 +10,9 @@ hostprogs-always-$(CONFIG_BUILDTIME_TABLE_SORT)		+= sorttable
 hostprogs-always-$(CONFIG_ASN1)				+= asn1_compiler
 hostprogs-always-$(CONFIG_MODULE_SIG_FORMAT)		+= sign-file
 hostprogs-always-$(CONFIG_SYSTEM_EXTRA_CERTIFICATE)	+= insert-sys-cert
+hostprogs-always-$(CONFIG_RUST)				+= generate_rust_target
+
+generate_rust_target-rust := y
 
 HOSTCFLAGS_sorttable.o = -I$(srctree)/tools/include
 HOSTLDLIBS_sorttable = -lpthread

scripts/Makefile.build

@@ -26,6 +26,7 @@ EXTRA_CPPFLAGS :=
 EXTRA_LDFLAGS  :=
 asflags-y  :=
 ccflags-y  :=
+rustflags-y :=
 cppflags-y :=
 ldflags-y  :=
 
@@ -271,6 +272,65 @@ quiet_cmd_cc_lst_c = MKLST   $@
 $(obj)/%.lst: $(src)/%.c FORCE
 	$(call if_changed_dep,cc_lst_c)
 
+# Compile Rust sources (.rs)
+# ---------------------------------------------------------------------------
+
+rust_allowed_features := core_ffi_c
+
+rust_common_cmd = \
+	RUST_MODFILE=$(modfile) $(RUSTC_OR_CLIPPY) $(rust_flags) \
+	-Zallow-features=$(rust_allowed_features) \
+	-Zcrate-attr=no_std \
+	-Zcrate-attr='feature($(rust_allowed_features))' \
+	--extern alloc --extern kernel \
+	--crate-type rlib --out-dir $(obj) -L $(objtree)/rust/ \
+	--crate-name $(basename $(notdir $@))
+
+rust_handle_depfile = \
+	mv $(obj)/$(basename $(notdir $@)).d $(depfile); \
+	sed -i '/^\#/d' $(depfile)
+
+# `--emit=obj`, `--emit=asm` and `--emit=llvm-ir` imply a single codegen unit
+# will be used. We explicitly request `-Ccodegen-units=1` in any case, and
+# the compiler shows a warning if it is not 1. However, if we ever stop
+# requesting it explicitly and we start using some other `--emit` that does not
+# imply it (and for which codegen is performed), then we would be out of sync,
+# i.e. the outputs we would get for the different single targets (e.g. `.ll`)
+# would not match each other.
+
+quiet_cmd_rustc_o_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@
+      cmd_rustc_o_rs = \
+	$(rust_common_cmd) --emit=dep-info,obj $<; \
+	$(rust_handle_depfile)
+
+$(obj)/%.o: $(src)/%.rs FORCE
+	$(call if_changed_dep,rustc_o_rs)
+
+quiet_cmd_rustc_rsi_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@
+      cmd_rustc_rsi_rs = \
+	$(rust_common_cmd) --emit=dep-info -Zunpretty=expanded $< >$@; \
+	command -v $(RUSTFMT) >/dev/null && $(RUSTFMT) $@; \
+	$(rust_handle_depfile)
+
+$(obj)/%.rsi: $(src)/%.rs FORCE
+	$(call if_changed_dep,rustc_rsi_rs)
+
+quiet_cmd_rustc_s_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@
+      cmd_rustc_s_rs = \
+	$(rust_common_cmd) --emit=dep-info,asm $<; \
+	$(rust_handle_depfile)
+
+$(obj)/%.s: $(src)/%.rs FORCE
+	$(call if_changed_dep,rustc_s_rs)
+
+quiet_cmd_rustc_ll_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@
+      cmd_rustc_ll_rs = \
+	$(rust_common_cmd) --emit=dep-info,llvm-ir $<; \
+	$(rust_handle_depfile)
+
+$(obj)/%.ll: $(src)/%.rs FORCE
+	$(call if_changed_dep,rustc_ll_rs)
+
 # Compile assembler sources (.S)
 # ---------------------------------------------------------------------------
 

scripts/Makefile.debug

@@ -1,4 +1,6 @@
 DEBUG_CFLAGS	:=
+DEBUG_RUSTFLAGS	:=
+
 debug-flags-y	:= -g
 
 ifdef CONFIG_DEBUG_INFO_SPLIT
@@ -17,9 +19,12 @@ KBUILD_AFLAGS	+= $(debug-flags-y)
 
 ifdef CONFIG_DEBUG_INFO_REDUCED
 DEBUG_CFLAGS	+= -fno-var-tracking
+DEBUG_RUSTFLAGS	+= -Cdebuginfo=1
 ifdef CONFIG_CC_IS_GCC
 DEBUG_CFLAGS	+= -femit-struct-debug-baseonly
 endif
+else
+DEBUG_RUSTFLAGS	+= -Cdebuginfo=2
 endif
 
 ifdef CONFIG_DEBUG_INFO_COMPRESSED
@@ -30,3 +35,6 @@ endif
 
 KBUILD_CFLAGS	+= $(DEBUG_CFLAGS)
 export DEBUG_CFLAGS
+
+KBUILD_RUSTFLAGS += $(DEBUG_RUSTFLAGS)
+export DEBUG_RUSTFLAGS

scripts/Makefile.host

@@ -22,6 +22,8 @@ $(obj)/%.tab.c $(obj)/%.tab.h: $(src)/%.y FORCE
 # to preprocess a data file.
 #
 # Both C and C++ are supported, but preferred language is C for such utilities.
+# Rust is also supported, but it may only be used in scenarios where a Rust
+# toolchain is required to be available (e.g. when  `CONFIG_RUST` is enabled).
 #
 # Sample syntax (see Documentation/kbuild/makefiles.rst for reference)
 # hostprogs := bin2hex
@@ -37,15 +39,20 @@ $(obj)/%.tab.c $(obj)/%.tab.h: $(src)/%.y FORCE
 # qconf-objs      := menu.o
 # Will compile qconf as a C++ program, and menu as a C program.
 # They are linked as C++ code to the executable qconf
+#
+# hostprogs   := target
+# target-rust := y
+# Will compile `target` as a Rust program, using `target.rs` as the crate root.
+# The crate may consist of several source files.
 
 # C code
 # Executables compiled from a single .c file
 host-csingle	:= $(foreach m,$(hostprogs), \
-			$(if $($(m)-objs)$($(m)-cxxobjs),,$(m)))
+			$(if $($(m)-objs)$($(m)-cxxobjs)$($(m)-rust),,$(m)))
 
 # C executables linked based on several .o files
 host-cmulti	:= $(foreach m,$(hostprogs),\
-		   $(if $($(m)-cxxobjs),,$(if $($(m)-objs),$(m))))
+		   $(if $($(m)-cxxobjs)$($(m)-rust),,$(if $($(m)-objs),$(m))))
 
 # Object (.o) files compiled from .c files
 host-cobjs	:= $(sort $(foreach m,$(hostprogs),$($(m)-objs)))
@@ -58,11 +65,17 @@ host-cxxmulti	:= $(foreach m,$(hostprogs),$(if $($(m)-cxxobjs),$(m)))
 # C++ Object (.o) files compiled from .cc files
 host-cxxobjs	:= $(sort $(foreach m,$(host-cxxmulti),$($(m)-cxxobjs)))
 
+# Rust code
+# Executables compiled from a single Rust crate (which may consist of
+# one or more .rs files)
+host-rust	:= $(foreach m,$(hostprogs),$(if $($(m)-rust),$(m)))
+
 host-csingle	:= $(addprefix $(obj)/,$(host-csingle))
 host-cmulti	:= $(addprefix $(obj)/,$(host-cmulti))
 host-cobjs	:= $(addprefix $(obj)/,$(host-cobjs))
 host-cxxmulti	:= $(addprefix $(obj)/,$(host-cxxmulti))
 host-cxxobjs	:= $(addprefix $(obj)/,$(host-cxxobjs))
+host-rust	:= $(addprefix $(obj)/,$(host-rust))
 
 #####
 # Handle options to gcc. Support building with separate output directory
@@ -71,6 +84,8 @@ _hostc_flags   = $(KBUILD_HOSTCFLAGS)   $(HOST_EXTRACFLAGS)   \
                  $(HOSTCFLAGS_$(target-stem).o)
 _hostcxx_flags = $(KBUILD_HOSTCXXFLAGS) $(HOST_EXTRACXXFLAGS) \
                  $(HOSTCXXFLAGS_$(target-stem).o)
+_hostrust_flags = $(KBUILD_HOSTRUSTFLAGS) $(HOST_EXTRARUSTFLAGS) \
+                  $(HOSTRUSTFLAGS_$(target-stem))
 
 # $(objtree)/$(obj) for including generated headers from checkin source files
 ifeq ($(KBUILD_EXTMOD),)
@@ -82,6 +97,7 @@ endif
 
 hostc_flags    = -Wp,-MMD,$(depfile) $(_hostc_flags)
 hostcxx_flags  = -Wp,-MMD,$(depfile) $(_hostcxx_flags)
+hostrust_flags = $(_hostrust_flags)
 
 #####
 # Compile programs on the host
@@ -128,5 +144,17 @@ quiet_cmd_host-cxxobjs	= HOSTCXX $@
 $(host-cxxobjs): $(obj)/%.o: $(src)/%.cc FORCE
 	$(call if_changed_dep,host-cxxobjs)
 
+# Create executable from a single Rust crate (which may consist of
+# one or more `.rs` files)
+# host-rust -> Executable
+quiet_cmd_host-rust	= HOSTRUSTC $@
+      cmd_host-rust	= \
+	$(HOSTRUSTC) $(hostrust_flags) --emit=dep-info,link \
+		--out-dir=$(obj)/ $<; \
+	mv $(obj)/$(target-stem).d $(depfile); \
+	sed -i '/^\#/d' $(depfile)
+$(host-rust): $(obj)/%: $(src)/%.rs FORCE
+	$(call if_changed_dep,host-rust)
+
 targets += $(host-csingle) $(host-cmulti) $(host-cobjs) \
-	   $(host-cxxmulti) $(host-cxxobjs)
+	   $(host-cxxmulti) $(host-cxxobjs) $(host-rust)

scripts/Makefile.lib

@@ -8,6 +8,7 @@ ldflags-y  += $(EXTRA_LDFLAGS)
 # flags that take effect in current and sub directories
 KBUILD_AFLAGS += $(subdir-asflags-y)
 KBUILD_CFLAGS += $(subdir-ccflags-y)
+KBUILD_RUSTFLAGS += $(subdir-rustflags-y)
 
 # Figure out what we need to build from the various variables
 # ===========================================================================
@@ -128,6 +129,10 @@ _c_flags       = $(filter-out $(CFLAGS_REMOVE_$(target-stem).o), \
                      $(filter-out $(ccflags-remove-y), \
                          $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) $(ccflags-y)) \
                      $(CFLAGS_$(target-stem).o))
+_rust_flags    = $(filter-out $(RUSTFLAGS_REMOVE_$(target-stem).o), \
+                     $(filter-out $(rustflags-remove-y), \
+                         $(KBUILD_RUSTFLAGS) $(rustflags-y)) \
+                     $(RUSTFLAGS_$(target-stem).o))
 _a_flags       = $(filter-out $(AFLAGS_REMOVE_$(target-stem).o), \
                      $(filter-out $(asflags-remove-y), \
                          $(KBUILD_CPPFLAGS) $(KBUILD_AFLAGS) $(asflags-y)) \
@@ -202,6 +207,11 @@ modkern_cflags =                                          \
 		$(KBUILD_CFLAGS_MODULE) $(CFLAGS_MODULE), \
 		$(KBUILD_CFLAGS_KERNEL) $(CFLAGS_KERNEL) $(modfile_flags))
 
+modkern_rustflags =                                              \
+	$(if $(part-of-module),                                   \
+		$(KBUILD_RUSTFLAGS_MODULE) $(RUSTFLAGS_MODULE), \
+		$(KBUILD_RUSTFLAGS_KERNEL) $(RUSTFLAGS_KERNEL))
+
 modkern_aflags = $(if $(part-of-module),				\
 			$(KBUILD_AFLAGS_MODULE) $(AFLAGS_MODULE),	\
 			$(KBUILD_AFLAGS_KERNEL) $(AFLAGS_KERNEL))
@@ -211,6 +221,8 @@ c_flags        = -Wp,-MMD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE)     \
 		 $(_c_flags) $(modkern_cflags)                           \
 		 $(basename_flags) $(modname_flags)
 
+rust_flags     = $(_rust_flags) $(modkern_rustflags) @$(objtree)/include/generated/rustc_cfg
+
 a_flags        = -Wp,-MMD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE)     \
 		 $(_a_flags) $(modkern_aflags)
 

scripts/Makefile.modfinal

@@ -41,11 +41,13 @@ quiet_cmd_ld_ko_o = LD [M]  $@
 
 quiet_cmd_btf_ko = BTF [M] $@
       cmd_btf_ko = 							\
-	if [ -f $(mixed-build-prefix)vmlinux ]; then						\
+	if [ ! -f $(mixed-build-prefix)vmlinux ]; then					\
+		printf "Skipping BTF generation for %s due to unavailability of $(mixed-build-prefix)vmlinux\n" $@ 1>&2; \
+	elif [ -n "$(CONFIG_RUST)" ] && $(srctree)/scripts/is_rust_module.sh $@; then 		\
+		printf "Skipping BTF generation for %s because it's a Rust module\n" $@ 1>&2; \
+	else								\
 		LLVM_OBJCOPY="$(OBJCOPY)" $(PAHOLE) -J $(PAHOLE_FLAGS) --btf_base $(mixed-build-prefix)vmlinux $@; \
 		$(RESOLVE_BTFIDS) -b $(mixed-build-prefix)vmlinux $@; 			\
-	else								\
-		printf "Skipping BTF generation for %s due to unavailability of $(mixed-build-prefix)vmlinux\n" $@ 1>&2; \
 	fi;
 
 # Same as newer-prereqs, but allows to exclude specified extra dependencies

scripts/cc-version.sh

@@ -1,13 +1,13 @@
 #!/bin/sh
 # SPDX-License-Identifier: GPL-2.0
 #
-# Print the compiler name and its version in a 5 or 6-digit form.
+# Print the C compiler name and its version in a 5 or 6-digit form.
 # Also, perform the minimum version check.
 
 set -e
 
-# Print the compiler name and some version components.
-get_compiler_info()
+# Print the C compiler name and some version components.
+get_c_compiler_info()
 {
 	cat <<- EOF | "$@" -E -P -x c - 2>/dev/null
 	#if defined(__clang__)
@@ -32,7 +32,7 @@ get_canonical_version()
 
 # $@ instead of $1 because multiple words might be given, e.g. CC="ccache gcc".
 orig_args="$@"
-set -- $(get_compiler_info "$@")
+set -- $(get_c_compiler_info "$@")
 
 name=$1
 
@@ -52,7 +52,7 @@ ICC)
 	min_version=$($min_tool_version icc)
 	;;
 *)
-	echo "$orig_args: unknown compiler" >&2
+	echo "$orig_args: unknown C compiler" >&2
 	exit 1
 	;;
 esac
@@ -62,7 +62,7 @@ min_cversion=$(get_canonical_version $min_version)
 
 if [ "$cversion" -lt "$min_cversion" ]; then
 	echo >&2 "***"
-	echo >&2 "*** Compiler is too old."
+	echo >&2 "*** C compiler is too old."
 	echo >&2 "***   Your $name version:    $version"
 	echo >&2 "***   Minimum $name version: $min_version"
 	echo >&2 "***"

scripts/checkpatch.pl

@@ -3616,7 +3616,7 @@ sub process {
 				my $comment = "";
 				if ($realfile =~ /\.(h|s|S)$/) {
 					$comment = '/*';
-				} elsif ($realfile =~ /\.(c|dts|dtsi)$/) {
+				} elsif ($realfile =~ /\.(c|rs|dts|dtsi)$/) {
 					$comment = '//';
 				} elsif (($checklicenseline == 2) || $realfile =~ /\.(sh|pl|py|awk|tc|yaml)$/) {
 					$comment = '#';
@@ -3664,7 +3664,7 @@ sub process {
 		}
 
 # check we are in a valid source file if not then ignore this hunk
-		next if ($realfile !~ /\.(h|c|s|S|sh|dtsi|dts)$/);
+		next if ($realfile !~ /\.(h|c|rs|s|S|sh|dtsi|dts)$/);
 
 # check for using SPDX-License-Identifier on the wrong line number
 		if ($realline != $checklicenseline &&
@@ -6783,15 +6783,19 @@ sub process {
 				}
 				if ($bad_specifier ne "") {
 					my $stat_real = get_stat_real($linenr, $lc);
+					my $msg_level = \&WARN;
 					my $ext_type = "Invalid";
 					my $use = "";
 					if ($bad_specifier =~ /p[Ff]/) {
 						$use = " - use %pS instead";
 						$use =~ s/pS/ps/ if ($bad_specifier =~ /pf/);
+					} elsif ($bad_specifier =~ /pA/) {
+						$use =  " - '%pA' is only intended to be used from Rust code";
+						$msg_level = \&ERROR;
 					}
 
-					WARN("VSPRINTF_POINTER_EXTENSION",
-					     "$ext_type vsprintf pointer extension '$bad_specifier'$use\n" . "$here\n$stat_real\n");
+					&{$msg_level}("VSPRINTF_POINTER_EXTENSION",
+						      "$ext_type vsprintf pointer extension '$bad_specifier'$use\n" . "$here\n$stat_real\n");
 				}
 			}
 		}

scripts/decode_stacktrace.sh

@@ -8,6 +8,14 @@ usage() {
 	echo "	$0 -r <release> | <vmlinux> [<base path>|auto] [<modules path>]"
 }
 
+# Try to find a Rust demangler
+if type llvm-cxxfilt >/dev/null 2>&1 ; then
+	cppfilt=llvm-cxxfilt
+elif type c++filt >/dev/null 2>&1 ; then
+	cppfilt=c++filt
+	cppfilt_opts=-i
+fi
+
 if [[ $1 == "-r" ]] ; then
 	vmlinux=""
 	basepath="auto"
@@ -180,6 +188,12 @@ parse_symbol() {
 	# In the case of inlines, move everything to same line
 	code=${code//$'\n'/' '}
 
+	# Demangle if the name looks like a Rust symbol and if
+	# we got a Rust demangler
+	if [[ $name =~ ^_R && $cppfilt != "" ]] ; then
+		name=$("$cppfilt" "$cppfilt_opts" "$name")
+	fi
+
 	# Replace old address with pretty line numbers
 	symbol="$segment$name ($code)"
 }

scripts/generate_rust_analyzer.py

@@ -0,0 +1,135 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+"""generate_rust_analyzer - Generates the `rust-project.json` file for `rust-analyzer`.
+"""
+
+import argparse
+import json
+import logging
+import pathlib
+import sys
+
+def generate_crates(srctree, objtree, sysroot_src):
+    # Generate the configuration list.
+    cfg = []
+    with open(objtree / "include" / "generated" / "rustc_cfg") as fd:
+        for line in fd:
+            line = line.replace("--cfg=", "")
+            line = line.replace("\n", "")
+            cfg.append(line)
+
+    # Now fill the crates list -- dependencies need to come first.
+    #
+    # Avoid O(n^2) iterations by keeping a map of indexes.
+    crates = []
+    crates_indexes = {}
+
+    def append_crate(display_name, root_module, deps, cfg=[], is_workspace_member=True, is_proc_macro=False):
+        crates_indexes[display_name] = len(crates)
+        crates.append({
+            "display_name": display_name,
+            "root_module": str(root_module),
+            "is_workspace_member": is_workspace_member,
+            "is_proc_macro": is_proc_macro,
+            "deps": [{"crate": crates_indexes[dep], "name": dep} for dep in deps],
+            "cfg": cfg,
+            "edition": "2021",
+            "env": {
+                "RUST_MODFILE": "This is only for rust-analyzer"
+            }
+        })
+
+    # First, the ones in `rust/` since they are a bit special.
+    append_crate(
+        "core",
+        sysroot_src / "core" / "src" / "lib.rs",
+        [],
+        is_workspace_member=False,
+    )
+
+    append_crate(
+        "compiler_builtins",
+        srctree / "rust" / "compiler_builtins.rs",
+        [],
+    )
+
+    append_crate(
+        "alloc",
+        srctree / "rust" / "alloc" / "lib.rs",
+        ["core", "compiler_builtins"],
+    )
+
+    append_crate(
+        "macros",
+        srctree / "rust" / "macros" / "lib.rs",
+        [],
+        is_proc_macro=True,
+    )
+    crates[-1]["proc_macro_dylib_path"] = "rust/libmacros.so"
+
+    append_crate(
+        "bindings",
+        srctree / "rust"/ "bindings" / "lib.rs",
+        ["core"],
+        cfg=cfg,
+    )
+    crates[-1]["env"]["OBJTREE"] = str(objtree.resolve(True))
+
+    append_crate(
+        "kernel",
+        srctree / "rust" / "kernel" / "lib.rs",
+        ["core", "alloc", "macros", "bindings"],
+        cfg=cfg,
+    )
+    crates[-1]["source"] = {
+        "include_dirs": [
+            str(srctree / "rust" / "kernel"),
+            str(objtree / "rust")
+        ],
+        "exclude_dirs": [],
+    }
+
+    # Then, the rest outside of `rust/`.
+    #
+    # We explicitly mention the top-level folders we want to cover.
+    for folder in ("samples", "drivers"):
+        for path in (srctree / folder).rglob("*.rs"):
+            logging.info("Checking %s", path)
+            name = path.name.replace(".rs", "")
+
+            # Skip those that are not crate roots.
+            if f"{name}.o" not in open(path.parent / "Makefile").read():
+                continue
+
+            logging.info("Adding %s", name)
+            append_crate(
+                name,
+                path,
+                ["core", "alloc", "kernel"],
+                cfg=cfg,
+            )
+
+    return crates
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--verbose', '-v', action='store_true')
+    parser.add_argument("srctree", type=pathlib.Path)
+    parser.add_argument("objtree", type=pathlib.Path)
+    parser.add_argument("sysroot_src", type=pathlib.Path)
+    args = parser.parse_args()
+
+    logging.basicConfig(
+        format="[%(asctime)s] [%(levelname)s] %(message)s",
+        level=logging.INFO if args.verbose else logging.WARNING
+    )
+
+    rust_project = {
+        "crates": generate_crates(args.srctree, args.objtree, args.sysroot_src),
+        "sysroot_src": str(args.sysroot_src),
+    }
+
+    json.dump(rust_project, sys.stdout, sort_keys=True, indent=4)
+
+if __name__ == "__main__":
+    main()

scripts/generate_rust_target.rs

@@ -0,0 +1,182 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! The custom target specification file generator for `rustc`.
+//!
+//! To configure a target from scratch, a JSON-encoded file has to be passed
+//! to `rustc` (introduced in [RFC 131]). These options and the file itself are
+//! unstable. Eventually, `rustc` should provide a way to do this in a stable
+//! manner. For instance, via command-line arguments. Therefore, this file
+//! should avoid using keys which can be set via `-C` or `-Z` options.
+//!
+//! [RFC 131]: https://rust-lang.github.io/rfcs/0131-target-specification.html
+
+use std::{
+    collections::HashMap,
+    fmt::{Display, Formatter, Result},
+    io::BufRead,
+};
+
+enum Value {
+    Boolean(bool),
+    Number(i32),
+    String(String),
+    Object(Object),
+}
+
+type Object = Vec<(String, Value)>;
+
+/// Minimal "almost JSON" generator (e.g. no `null`s, no arrays, no escaping),
+/// enough for this purpose.
+impl Display for Value {
+    fn fmt(&self, formatter: &mut Formatter<'_>) -> Result {
+        match self {
+            Value::Boolean(boolean) => write!(formatter, "{}", boolean),
+            Value::Number(number) => write!(formatter, "{}", number),
+            Value::String(string) => write!(formatter, "\"{}\"", string),
+            Value::Object(object) => {
+                formatter.write_str("{")?;
+                if let [ref rest @ .., ref last] = object[..] {
+                    for (key, value) in rest {
+                        write!(formatter, "\"{}\": {},", key, value)?;
+                    }
+                    write!(formatter, "\"{}\": {}", last.0, last.1)?;
+                }
+                formatter.write_str("}")
+            }
+        }
+    }
+}
+
+struct TargetSpec(Object);
+
+impl TargetSpec {
+    fn new() -> TargetSpec {
+        TargetSpec(Vec::new())
+    }
+}
+
+trait Push<T> {
+    fn push(&mut self, key: &str, value: T);
+}
+
+impl Push<bool> for TargetSpec {
+    fn push(&mut self, key: &str, value: bool) {
+        self.0.push((key.to_string(), Value::Boolean(value)));
+    }
+}
+
+impl Push<i32> for TargetSpec {
+    fn push(&mut self, key: &str, value: i32) {
+        self.0.push((key.to_string(), Value::Number(value)));
+    }
+}
+
+impl Push<String> for TargetSpec {
+    fn push(&mut self, key: &str, value: String) {
+        self.0.push((key.to_string(), Value::String(value)));
+    }
+}
+
+impl Push<&str> for TargetSpec {
+    fn push(&mut self, key: &str, value: &str) {
+        self.push(key, value.to_string());
+    }
+}
+
+impl Push<Object> for TargetSpec {
+    fn push(&mut self, key: &str, value: Object) {
+        self.0.push((key.to_string(), Value::Object(value)));
+    }
+}
+
+impl Display for TargetSpec {
+    fn fmt(&self, formatter: &mut Formatter<'_>) -> Result {
+        // We add some newlines for clarity.
+        formatter.write_str("{\n")?;
+        if let [ref rest @ .., ref last] = self.0[..] {
+            for (key, value) in rest {
+                write!(formatter, "    \"{}\": {},\n", key, value)?;
+            }
+            write!(formatter, "    \"{}\": {}\n", last.0, last.1)?;
+        }
+        formatter.write_str("}")
+    }
+}
+
+struct KernelConfig(HashMap<String, String>);
+
+impl KernelConfig {
+    /// Parses `include/config/auto.conf` from `stdin`.
+    fn from_stdin() -> KernelConfig {
+        let mut result = HashMap::new();
+
+        let stdin = std::io::stdin();
+        let mut handle = stdin.lock();
+        let mut line = String::new();
+
+        loop {
+            line.clear();
+
+            if handle.read_line(&mut line).unwrap() == 0 {
+                break;
+            }
+
+            if line.starts_with('#') {
+                continue;
+            }
+
+            let (key, value) = line.split_once('=').expect("Missing `=` in line.");
+            result.insert(key.to_string(), value.trim_end_matches('\n').to_string());
+        }
+
+        KernelConfig(result)
+    }
+
+    /// Does the option exist in the configuration (any value)?
+    ///
+    /// The argument must be passed without the `CONFIG_` prefix.
+    /// This avoids repetition and it also avoids `fixdep` making us
+    /// depend on it.
+    fn has(&self, option: &str) -> bool {
+        let option = "CONFIG_".to_owned() + option;
+        self.0.contains_key(&option)
+    }
+}
+
+fn main() {
+    let cfg = KernelConfig::from_stdin();
+    let mut ts = TargetSpec::new();
+
+    // `llvm-target`s are taken from `scripts/Makefile.clang`.
+    if cfg.has("X86_64") {
+        ts.push("arch", "x86_64");
+        ts.push(
+            "data-layout",
+            "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128",
+        );
+        let mut features = "-3dnow,-3dnowa,-mmx,+soft-float".to_string();
+        if cfg.has("RETPOLINE") {
+            features += ",+retpoline-external-thunk";
+        }
+        ts.push("features", features);
+        ts.push("llvm-target", "x86_64-linux-gnu");
+        ts.push("target-pointer-width", "64");
+    } else {
+        panic!("Unsupported architecture");
+    }
+
+    ts.push("emit-debug-gdb-scripts", false);
+    ts.push("frame-pointer", "may-omit");
+    ts.push(
+        "stack-probes",
+        vec![("kind".to_string(), Value::String("none".to_string()))],
+    );
+
+    // Everything else is LE, whether `CPU_LITTLE_ENDIAN` is declared or not
+    // (e.g. x86). It is also `rustc`'s default.
+    if cfg.has("CPU_BIG_ENDIAN") {
+        ts.push("target-endian", "big");
+    }
+
+    println!("{}", ts);
+}

scripts/is_rust_module.sh

@@ -0,0 +1,16 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+#
+# is_rust_module.sh module.ko
+#
+# Returns `0` if `module.ko` is a Rust module, `1` otherwise.
+
+set -e
+
+# Using the `16_` prefix ensures other symbols with the same substring
+# are not picked up (even if it would be unlikely). The last part is
+# used just in case LLVM decides to use the `.` suffix.
+#
+# In the future, checking for the `.comment` section may be another
+# option, see https://github.com/rust-lang/rust/pull/97550.
+${NM} "$*" | grep -qE '^[0-9a-fA-F]+ r _R[^[:space:]]+16___IS_RUST_MODULE[^[:space:]]*$'

scripts/kallsyms.c

@@ -27,7 +27,23 @@
 
 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
 
-#define KSYM_NAME_LEN		128
+#define _stringify_1(x)	#x
+#define _stringify(x)	_stringify_1(x)
+
+#define KSYM_NAME_LEN		512
+
+/*
+ * A substantially bigger size than the current maximum.
+ *
+ * It cannot be defined as an expression because it gets stringified
+ * for the fscanf() format string. Therefore, a _Static_assert() is
+ * used instead to maintain the relationship with KSYM_NAME_LEN.
+ */
+#define KSYM_NAME_LEN_BUFFER	2048
+_Static_assert(
+	KSYM_NAME_LEN_BUFFER == KSYM_NAME_LEN * 4,
+	"Please keep KSYM_NAME_LEN_BUFFER in sync with KSYM_NAME_LEN"
+);
 
 struct sym_entry {
 	unsigned long long addr;
@@ -198,15 +214,15 @@ static void check_symbol_range(const char *sym, unsigned long long addr,
 
 static struct sym_entry *read_symbol(FILE *in)
 {
-	char name[500], type;
+	char name[KSYM_NAME_LEN_BUFFER+1], type;
 	unsigned long long addr;
 	unsigned int len;
 	struct sym_entry *sym;
 	int rc;
 
-	rc = fscanf(in, "%llx %c %499s\n", &addr, &type, name);
+	rc = fscanf(in, "%llx %c %" _stringify(KSYM_NAME_LEN_BUFFER) "s\n", &addr, &type, name);
 	if (rc != 3) {
-		if (rc != EOF && fgets(name, 500, in) == NULL)
+		if (rc != EOF && fgets(name, ARRAY_SIZE(name), in) == NULL)
 			fprintf(stderr, "Read error or end of file.\n");
 		return NULL;
 	}
@@ -471,12 +487,35 @@ static void write_src(void)
 		if ((i & 0xFF) == 0)
 			markers[i >> 8] = off;
 
-		printf("\t.byte 0x%02x", table[i]->len);
+		/* There cannot be any symbol of length zero. */
+		if (table[i]->len == 0) {
+			fprintf(stderr, "kallsyms failure: "
+				"unexpected zero symbol length\n");
+			exit(EXIT_FAILURE);
+		}
+
+		/* Only lengths that fit in up-to-two-byte ULEB128 are supported. */
+		if (table[i]->len > 0x3FFF) {
+			fprintf(stderr, "kallsyms failure: "
+				"unexpected huge symbol length\n");
+			exit(EXIT_FAILURE);
+		}
+
+		/* Encode length with ULEB128. */
+		if (table[i]->len <= 0x7F) {
+			/* Most symbols use a single byte for the length. */
+			printf("\t.byte 0x%02x", table[i]->len);
+			off += table[i]->len + 1;
+		} else {
+			/* "Big" symbols use two bytes. */
+			printf("\t.byte 0x%02x, 0x%02x",
+				(table[i]->len & 0x7F) | 0x80,
+				(table[i]->len >> 7) & 0x7F);
+			off += table[i]->len + 2;
+		}
 		for (k = 0; k < table[i]->len; k++)
 			printf(", 0x%02x", table[i]->sym[k]);
 		printf("\n");
-
-		off += table[i]->len + 1;
 	}
 	printf("\n");
 

scripts/kconfig/confdata.c

@@ -216,6 +216,13 @@ static const char *conf_get_autoheader_name(void)
 	return name ? name : "include/generated/autoconf.h";
 }
 
+static const char *conf_get_rustccfg_name(void)
+{
+	char *name = getenv("KCONFIG_RUSTCCFG");
+
+	return name ? name : "include/generated/rustc_cfg";
+}
+
 static int conf_set_sym_val(struct symbol *sym, int def, int def_flags, char *p)
 {
 	char *p2;
@@ -605,6 +612,9 @@ static const struct comment_style comment_style_c = {
 
 static void conf_write_heading(FILE *fp, const struct comment_style *cs)
 {
+	if (!cs)
+		return;
+
 	fprintf(fp, "%s\n", cs->prefix);
 
 	fprintf(fp, "%s Automatically generated file; DO NOT EDIT.\n",
@@ -745,6 +755,65 @@ static void print_symbol_for_c(FILE *fp, struct symbol *sym)
 	free(escaped);
 }
 
+static void print_symbol_for_rustccfg(FILE *fp, struct symbol *sym)
+{
+	const char *val;
+	const char *val_prefix = "";
+	char *val_prefixed = NULL;
+	size_t val_prefixed_len;
+	char *escaped = NULL;
+
+	if (sym->type == S_UNKNOWN)
+		return;
+
+	val = sym_get_string_value(sym);
+
+	switch (sym->type) {
+	case S_BOOLEAN:
+	case S_TRISTATE:
+		/*
+		 * We do not care about disabled ones, i.e. no need for
+		 * what otherwise are "comments" in other printers.
+		 */
+		if (*val == 'n')
+			return;
+
+		/*
+		 * To have similar functionality to the C macro `IS_ENABLED()`
+		 * we provide an empty `--cfg CONFIG_X` here in both `y`
+		 * and `m` cases.
+		 *
+		 * Then, the common `fprintf()` below will also give us
+		 * a `--cfg CONFIG_X="y"` or `--cfg CONFIG_X="m"`, which can
+		 * be used as the equivalent of `IS_BUILTIN()`/`IS_MODULE()`.
+		 */
+		fprintf(fp, "--cfg=%s%s\n", CONFIG_, sym->name);
+		break;
+	case S_HEX:
+		if (val[0] != '0' || (val[1] != 'x' && val[1] != 'X'))
+			val_prefix = "0x";
+		break;
+	default:
+		break;
+	}
+
+	if (strlen(val_prefix) > 0) {
+		val_prefixed_len = strlen(val) + strlen(val_prefix) + 1;
+		val_prefixed = xmalloc(val_prefixed_len);
+		snprintf(val_prefixed, val_prefixed_len, "%s%s", val_prefix, val);
+		val = val_prefixed;
+	}
+
+	/* All values get escaped: the `--cfg` option only takes strings */
+	escaped = escape_string_value(val);
+	val = escaped;
+
+	fprintf(fp, "--cfg=%s%s=%s\n", CONFIG_, sym->name, val);
+
+	free(escaped);
+	free(val_prefixed);
+}
+
 /*
  * Write out a minimal config.
  * All values that has default values are skipped as this is redundant.
@@ -1132,6 +1201,12 @@ int conf_write_autoconf(int overwrite)
 	if (ret)
 		return ret;
 
+	ret = __conf_write_autoconf(conf_get_rustccfg_name(),
+				    print_symbol_for_rustccfg,
+				    NULL);
+	if (ret)
+		return ret;
+
 	/*
 	 * Create include/config/auto.conf. This must be the last step because
 	 * Kbuild has a dependency on auto.conf and this marks the successful

scripts/min-tool-version.sh

@@ -30,6 +30,12 @@ llvm)
 		echo 11.0.0
 	fi
 	;;
+rustc)
+	echo 1.62.0
+	;;
+bindgen)
+	echo 0.56.0
+	;;
 *)
 	echo "$1: unknown tool" >&2
 	exit 1

scripts/rust_is_available.sh

@@ -0,0 +1,160 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+#
+# Tests whether a suitable Rust toolchain is available.
+#
+# Pass `-v` for human output and more checks (as warnings).
+
+set -e
+
+min_tool_version=$(dirname $0)/min-tool-version.sh
+
+# Convert the version string x.y.z to a canonical up-to-7-digits form.
+#
+# Note that this function uses one more digit (compared to other
+# instances in other version scripts) to give a bit more space to
+# `rustc` since it will reach 1.100.0 in late 2026.
+get_canonical_version()
+{
+	IFS=.
+	set -- $1
+	echo $((100000 * $1 + 100 * $2 + $3))
+}
+
+# Check that the Rust compiler exists.
+if ! command -v "$RUSTC" >/dev/null; then
+	if [ "$1" = -v ]; then
+		echo >&2 "***"
+		echo >&2 "*** Rust compiler '$RUSTC' could not be found."
+		echo >&2 "***"
+	fi
+	exit 1
+fi
+
+# Check that the Rust bindings generator exists.
+if ! command -v "$BINDGEN" >/dev/null; then
+	if [ "$1" = -v ]; then
+		echo >&2 "***"
+		echo >&2 "*** Rust bindings generator '$BINDGEN' could not be found."
+		echo >&2 "***"
+	fi
+	exit 1
+fi
+
+# Check that the Rust compiler version is suitable.
+#
+# Non-stable and distributions' versions may have a version suffix, e.g. `-dev`.
+rust_compiler_version=$( \
+	LC_ALL=C "$RUSTC" --version 2>/dev/null \
+		| head -n 1 \
+		| grep -oE '[0-9]+\.[0-9]+\.[0-9]+' \
+)
+rust_compiler_min_version=$($min_tool_version rustc)
+rust_compiler_cversion=$(get_canonical_version $rust_compiler_version)
+rust_compiler_min_cversion=$(get_canonical_version $rust_compiler_min_version)
+if [ "$rust_compiler_cversion" -lt "$rust_compiler_min_cversion" ]; then
+	if [ "$1" = -v ]; then
+		echo >&2 "***"
+		echo >&2 "*** Rust compiler '$RUSTC' is too old."
+		echo >&2 "***   Your version:    $rust_compiler_version"
+		echo >&2 "***   Minimum version: $rust_compiler_min_version"
+		echo >&2 "***"
+	fi
+	exit 1
+fi
+if [ "$1" = -v ] && [ "$rust_compiler_cversion" -gt "$rust_compiler_min_cversion" ]; then
+	echo >&2 "***"
+	echo >&2 "*** Rust compiler '$RUSTC' is too new. This may or may not work."
+	echo >&2 "***   Your version:     $rust_compiler_version"
+	echo >&2 "***   Expected version: $rust_compiler_min_version"
+	echo >&2 "***"
+fi
+
+# Check that the Rust bindings generator is suitable.
+#
+# Non-stable and distributions' versions may have a version suffix, e.g. `-dev`.
+rust_bindings_generator_version=$( \
+	LC_ALL=C "$BINDGEN" --version 2>/dev/null \
+		| head -n 1 \
+		| grep -oE '[0-9]+\.[0-9]+\.[0-9]+' \
+)
+rust_bindings_generator_min_version=$($min_tool_version bindgen)
+rust_bindings_generator_cversion=$(get_canonical_version $rust_bindings_generator_version)
+rust_bindings_generator_min_cversion=$(get_canonical_version $rust_bindings_generator_min_version)
+if [ "$rust_bindings_generator_cversion" -lt "$rust_bindings_generator_min_cversion" ]; then
+	if [ "$1" = -v ]; then
+		echo >&2 "***"
+		echo >&2 "*** Rust bindings generator '$BINDGEN' is too old."
+		echo >&2 "***   Your version:    $rust_bindings_generator_version"
+		echo >&2 "***   Minimum version: $rust_bindings_generator_min_version"
+		echo >&2 "***"
+	fi
+	exit 1
+fi
+if [ "$1" = -v ] && [ "$rust_bindings_generator_cversion" -gt "$rust_bindings_generator_min_cversion" ]; then
+	echo >&2 "***"
+	echo >&2 "*** Rust bindings generator '$BINDGEN' is too new. This may or may not work."
+	echo >&2 "***   Your version:     $rust_bindings_generator_version"
+	echo >&2 "***   Expected version: $rust_bindings_generator_min_version"
+	echo >&2 "***"
+fi
+
+# Check that the `libclang` used by the Rust bindings generator is suitable.
+bindgen_libclang_version=$( \
+	LC_ALL=C "$BINDGEN" $(dirname $0)/rust_is_available_bindgen_libclang.h 2>&1 >/dev/null \
+		| grep -F 'clang version ' \
+		| grep -oE '[0-9]+\.[0-9]+\.[0-9]+' \
+		| head -n 1 \
+)
+bindgen_libclang_min_version=$($min_tool_version llvm)
+bindgen_libclang_cversion=$(get_canonical_version $bindgen_libclang_version)
+bindgen_libclang_min_cversion=$(get_canonical_version $bindgen_libclang_min_version)
+if [ "$bindgen_libclang_cversion" -lt "$bindgen_libclang_min_cversion" ]; then
+	if [ "$1" = -v ]; then
+		echo >&2 "***"
+		echo >&2 "*** libclang (used by the Rust bindings generator '$BINDGEN') is too old."
+		echo >&2 "***   Your version:    $bindgen_libclang_version"
+		echo >&2 "***   Minimum version: $bindgen_libclang_min_version"
+		echo >&2 "***"
+	fi
+	exit 1
+fi
+
+# If the C compiler is Clang, then we can also check whether its version
+# matches the `libclang` version used by the Rust bindings generator.
+#
+# In the future, we might be able to perform a full version check, see
+# https://github.com/rust-lang/rust-bindgen/issues/2138.
+if [ "$1" = -v ]; then
+	cc_name=$($(dirname $0)/cc-version.sh "$CC" | cut -f1 -d' ')
+	if [ "$cc_name" = Clang ]; then
+		clang_version=$( \
+			LC_ALL=C "$CC" --version 2>/dev/null \
+				| sed -nE '1s:.*version ([0-9]+\.[0-9]+\.[0-9]+).*:\1:p'
+		)
+		if [ "$clang_version" != "$bindgen_libclang_version" ]; then
+			echo >&2 "***"
+			echo >&2 "*** libclang (used by the Rust bindings generator '$BINDGEN')"
+			echo >&2 "*** version does not match Clang's. This may be a problem."
+			echo >&2 "***   libclang version: $bindgen_libclang_version"
+			echo >&2 "***   Clang version:    $clang_version"
+			echo >&2 "***"
+		fi
+	fi
+fi
+
+# Check that the source code for the `core` standard library exists.
+#
+# `$KRUSTFLAGS` is passed in case the user added `--sysroot`.
+rustc_sysroot=$("$RUSTC" $KRUSTFLAGS --print sysroot)
+rustc_src=${RUST_LIB_SRC:-"$rustc_sysroot/lib/rustlib/src/rust/library"}
+rustc_src_core="$rustc_src/core/src/lib.rs"
+if [ ! -e "$rustc_src_core" ]; then
+	if [ "$1" = -v ]; then
+		echo >&2 "***"
+		echo >&2 "*** Source code for the 'core' standard library could not be found"
+		echo >&2 "*** at '$rustc_src_core'."
+		echo >&2 "***"
+	fi
+	exit 1
+fi

scripts/rust_is_available_bindgen_libclang.h

@@ -0,0 +1,2 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#pragma message("clang version " __clang_version__)

tools/include/linux/kallsyms.h

@@ -6,7 +6,7 @@
 #include <stdio.h>
 #include <unistd.h>
 
-#define KSYM_NAME_LEN 128
+#define KSYM_NAME_LEN 512
 
 struct module;
 

tools/lib/perf/include/perf/event.h

@@ -97,7 +97,7 @@ struct perf_record_throttle {
 };
 
 #ifndef KSYM_NAME_LEN
-#define KSYM_NAME_LEN 256
+#define KSYM_NAME_LEN 512
 #endif
 
 struct perf_record_ksymbol {

tools/lib/symbol/kallsyms.h

@@ -7,7 +7,7 @@
 #include <linux/types.h>
 
 #ifndef KSYM_NAME_LEN
-#define KSYM_NAME_LEN 256
+#define KSYM_NAME_LEN 512
 #endif
 
 static inline u8 kallsyms2elf_binding(char type)