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Alexei Starovoitov 2564a031ab Merge branch 'bpf: allow ctx writes using BPF_ST_MEM instruction' 
Eduard Zingerman says:

====================

Changes v1 -> v2, suggested by Alexei:
- Resolved conflict with recent commit:
  6fcd486b3a ("bpf: Refactor RCU enforcement in the verifier");
- Variable `ctx_access` removed in function `convert_ctx_accesses()`;
- Macro `BPF_COPY_STORE` renamed to `BPF_EMIT_STORE` and fixed to
  correctly extract original store instruction class from code.

Original message follows:

The function verifier.c:convert_ctx_access() applies some rewrites to BPF
instructions that read from or write to the BPF program context.
For example, the write instruction for the `struct bpf_sockopt::retval`
field:

    *(u32 *)(r1 + offsetof(struct bpf_sockopt, retval)) = r2

Is transformed to:

    *(u64 *)(r1 + offsetof(struct bpf_sockopt_kern, tmp_reg)) = r9
    r9 = *(u64 *)(r1 + offsetof(struct bpf_sockopt_kern, current_task))
    r9 = *(u64 *)(r9 + offsetof(struct task_struct, bpf_ctx))
    *(u32 *)(r9 + offsetof(struct bpf_cg_run_ctx, retval)) = r2
    r9 = *(u64 *)(r1 + offsetof(struct bpf_sockopt_kern, tmp_reg))

Currently, the verifier only supports such transformations for LDX
(memory-to-register read) and STX (register-to-memory write) instructions.
Error is reported for ST instructions (immediate-to-memory write).
This is fine because clang does not currently emit ST instructions.

However, new `-mcpu=v4` clang flag is planned, which would allow to emit
ST instructions (discussed in [1]).

This patch-set adjusts the verifier to support ST instructions in
`verifier.c:convert_ctx_access()`.

The patches #1 and #2 were previously shared as part of RFC [2]. The
changes compared to that RFC are:
- In patch #1, a bug in the handling of the
  `struct __sk_buff::queue_mapping` field was fixed.
- Patch #3 is added, which is a set of disassembler-based test cases for
  context access rewrites. The test cases cover all fields for which the
  handling code is modified in patch #1.

[1] Propose some new instructions for -mcpu=v4
    https://lore.kernel.org/bpf/4bfe98be-5333-1c7e-2f6d-42486c8ec039@meta.com/
[2] RFC Support for BPF_ST instruction in LLVM C compiler
    https://lore.kernel.org/bpf/20221231163122.1360813-1-eddyz87@gmail.com/
[3] v1
    https://lore.kernel.org/bpf/20230302225507.3413720-1-eddyz87@gmail.com/
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2023-03-03 21:41:46 -08:00
arch bpf, mips: Implement R4000 workarounds for JIT 2023-02-28 14:52:55 +01:00
block Updates for the interrupt subsystem: 2023-02-21 10:03:48 -08:00
certs certs: don't try to update blacklist keys 2023-02-13 10:11:20 +02:00
crypto Networking changes for 6.3. 2023-02-21 18:24:12 -08:00
Documentation bpf: Introduce kptr_rcu. 2023-03-03 17:42:20 +01:00
drivers Networking changes for 6.3. 2023-02-21 18:24:12 -08:00
fs Networking changes for 6.3. 2023-02-21 18:24:12 -08:00
include bpf: Use separate RCU callbacks for freeing selem 2023-03-03 09:45:27 -08:00
init Networking changes for 6.3. 2023-02-21 18:24:12 -08:00
io_uring for-6.3/block-2023-02-16 2023-02-20 14:27:21 -08:00
ipc fs: port ->permission() to pass mnt_idmap 2023-01-19 09:24:28 +01:00
kernel bpf: allow ctx writes using BPF_ST_MEM instruction 2023-03-03 21:41:46 -08:00
lib Networking changes for 6.3. 2023-02-21 18:24:12 -08:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm Networking changes for 6.3. 2023-02-21 18:24:12 -08:00
net bpf: allow ctx writes using BPF_ST_MEM instruction 2023-03-03 21:41:46 -08:00
rust Rust changes for v6.3 2023-02-20 10:40:42 -08:00
samples samples/bpf: Use bpf_{btf,link,map,prog}_get_info_by_fd() 2023-02-16 15:32:45 -08:00
scripts Networking changes for 6.3. 2023-02-21 18:24:12 -08:00
security This update includes the following changes: 2023-02-21 18:10:50 -08:00
sound ARM: unused boardfile removal for 6.3 2023-02-20 15:28:57 -08:00
tools selftests/bpf: Disassembler tests for verifier.c:convert_ctx_access() 2023-03-03 21:41:46 -08:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt VFIO fixes for v6.2-rc6 2023-01-23 11:56:07 -08:00
.clang-format iommufd for 6.2 2022-12-14 09:15:43 -08:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore *.rpm 2022-12-30 17:22:14 +09:00
.mailmap 12 hotfixes, mostly against mm/. Five of these fixes are cc:stable. 2023-02-13 14:09:20 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: update SCTP maintainers 2023-02-02 11:35:33 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Networking changes for 6.3. 2023-02-21 18:24:12 -08:00
Makefile Rust changes for v6.3 2023-02-20 10:40:42 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.