From abbf9a44944171ca99c150adad9361a2f517d3b6 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Sun, 27 Jul 2025 11:23:17 +0200 Subject: [PATCH 1/2] rust: workaround `rustdoc` target modifiers bug Starting with Rust 1.88.0 (released 2025-06-26), `rustdoc` complains about a target modifier mismatch in configurations where `-Zfixed-x18` is passed: error: mixing `-Zfixed-x18` will cause an ABI mismatch in crate `rust_out` | = help: the `-Zfixed-x18` flag modifies the ABI so Rust crates compiled with different values of this flag cannot be used together safely = note: unset `-Zfixed-x18` in this crate is incompatible with `-Zfixed-x18=` in dependency `core` = help: set `-Zfixed-x18=` in this crate or unset `-Zfixed-x18` in `core` = help: if you are sure this will not cause problems, you may use `-Cunsafe-allow-abi-mismatch=fixed-x18` to silence this error The reason is that `rustdoc` was not passing the target modifiers when configuring the session options, and thus it would report a mismatch that did not exist as soon as a target modifier is used in a dependency. We did not notice it in the kernel until now because `-Zfixed-x18` has been a target modifier only since 1.88.0 (and it is the only one we use so far). The issue has been reported upstream [1] and a fix has been submitted [2], including a test similar to the kernel case. [ This is now fixed upstream (thanks Guillaume for the quick review), so it will be fixed in Rust 1.90.0 (expected 2025-09-18). - Miguel ] Meanwhile, conditionally pass `-Cunsafe-allow-abi-mismatch=fixed-x18` to workaround the issue on our side. Cc: stable@vger.kernel.org # Needed in 6.12.y and later (Rust is pinned in older LTSs). Reported-by: Konrad Dybcio Closes: https://lore.kernel.org/rust-for-linux/36cdc798-524f-4910-8b77-d7b9fac08d77@oss.qualcomm.com/ Link: https://github.com/rust-lang/rust/issues/144521 [1] Link: https://github.com/rust-lang/rust/pull/144523 [2] Reviewed-by: Alice Ryhl Link: https://lore.kernel.org/r/20250727092317.2930617-1-ojeda@kernel.org Signed-off-by: Miguel Ojeda --- rust/Makefile | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/rust/Makefile b/rust/Makefile index 4263462b8470..d47f82588d78 100644 --- a/rust/Makefile +++ b/rust/Makefile @@ -65,6 +65,10 @@ core-cfgs = \ core-edition := $(if $(call rustc-min-version,108700),2024,2021) +# `rustdoc` did not save the target modifiers, thus workaround for +# the time being (https://github.com/rust-lang/rust/issues/144521). +rustdoc_modifiers_workaround := $(if $(call rustc-min-version,108800),-Cunsafe-allow-abi-mismatch=fixed-x18) + # `rustc` recognizes `--remap-path-prefix` since 1.26.0, but `rustdoc` only # since Rust 1.81.0. Moreover, `rustdoc` ICEs on out-of-tree builds since Rust # 1.82.0 (https://github.com/rust-lang/rust/issues/138520). Thus workaround both @@ -77,6 +81,7 @@ quiet_cmd_rustdoc = RUSTDOC $(if $(rustdoc_host),H, ) $< -Zunstable-options --generate-link-to-definition \ --output $(rustdoc_output) \ --crate-name $(subst rustdoc-,,$@) \ + $(rustdoc_modifiers_workaround) \ $(if $(rustdoc_host),,--sysroot=/dev/null) \ @$(objtree)/include/generated/rustc_cfg $< @@ -215,6 +220,7 @@ quiet_cmd_rustdoc_test_kernel = RUSTDOC TK $< --extern bindings --extern uapi \ --no-run --crate-name kernel -Zunstable-options \ --sysroot=/dev/null \ + $(rustdoc_modifiers_workaround) \ --test-builder $(objtree)/scripts/rustdoc_test_builder \ $< $(rustdoc_test_kernel_quiet); \ $(objtree)/scripts/rustdoc_test_gen From 252fea131e15aba2cd487119d1a8f546471199e2 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Sat, 26 Jul 2025 15:34:35 +0200 Subject: [PATCH 2/2] rust: kbuild: clean output before running `rustdoc` `rustdoc` can get confused when generating documentation into a folder that contains generated files from other `rustdoc` versions. For instance, running something like: rustup default 1.78.0 make LLVM=1 rustdoc rustup default 1.88.0 make LLVM=1 rustdoc may generate errors like: error: couldn't generate documentation: invalid template: last line expected to start with a comment | = note: failed to create or modify "./Documentation/output/rust/rustdoc/src-files.js" Thus just always clean the output folder before generating the documentation -- we are anyway regenerating it every time the `rustdoc` target gets called, at least for the time being. Cc: stable@vger.kernel.org # Needed in 6.12.y and later (Rust is pinned in older LTSs). Reported-by: Daniel Almeida Closes: https://rust-for-linux.zulipchat.com/#narrow/channel/288089/topic/x/near/527201113 Reviewed-by: Tamir Duberstein Link: https://lore.kernel.org/r/20250726133435.2460085-1-ojeda@kernel.org Signed-off-by: Miguel Ojeda --- rust/Makefile | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/rust/Makefile b/rust/Makefile index d47f82588d78..bfa915b0e588 100644 --- a/rust/Makefile +++ b/rust/Makefile @@ -111,14 +111,14 @@ rustdoc: rustdoc-core rustdoc-macros rustdoc-compiler_builtins \ 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 +rustdoc-macros: $(src)/macros/lib.rs rustdoc-clean FORCE +$(call if_changed,rustdoc) # Starting with Rust 1.82.0, skipping `-Wrustdoc::unescaped_backticks` should # not be needed -- see https://github.com/rust-lang/rust/pull/128307. rustdoc-core: private skip_flags = --edition=2021 -Wrustdoc::unescaped_backticks rustdoc-core: private rustc_target_flags = --edition=$(core-edition) $(core-cfgs) -rustdoc-core: $(RUST_LIB_SRC)/core/src/lib.rs FORCE +rustdoc-core: $(RUST_LIB_SRC)/core/src/lib.rs rustdoc-clean FORCE +$(call if_changed,rustdoc) rustdoc-compiler_builtins: $(src)/compiler_builtins.rs rustdoc-core FORCE @@ -130,7 +130,8 @@ rustdoc-ffi: $(src)/ffi.rs rustdoc-core FORCE rustdoc-pin_init_internal: private rustdoc_host = yes rustdoc-pin_init_internal: private rustc_target_flags = --cfg kernel \ --extern proc_macro --crate-type proc-macro -rustdoc-pin_init_internal: $(src)/pin-init/internal/src/lib.rs FORCE +rustdoc-pin_init_internal: $(src)/pin-init/internal/src/lib.rs \ + rustdoc-clean FORCE +$(call if_changed,rustdoc) rustdoc-pin_init: private rustdoc_host = yes @@ -148,6 +149,9 @@ rustdoc-kernel: $(src)/kernel/lib.rs rustdoc-core rustdoc-ffi rustdoc-macros \ $(obj)/bindings.o FORCE +$(call if_changed,rustdoc) +rustdoc-clean: FORCE + $(Q)rm -rf $(rustdoc_output) + quiet_cmd_rustc_test_library = $(RUSTC_OR_CLIPPY_QUIET) TL $< cmd_rustc_test_library = \ OBJTREE=$(abspath $(objtree)) \