kernel/linux.git/include/linux/compiler-gcc.h, branch v6.6.131

kasan: Fix Software Tag-Based KASAN with GCC

2024-11-08T15:28:20+00:00

[ Upstream commit 894b00a3350c560990638bdf89bdf1f3d5491950 ] Per [1], -fsanitize=kernel-hwaddress with GCC currently does not disable instrumentation in functions with __attribute__((no_sanitize_address)). However, __attribute__((no_sanitize("hwaddress"))) does correctly disable instrumentation. Use it instead. Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117196 [1] Link: https://lore.kernel.org/r/000000000000f362e80620e27859@google.com Link: https://lore.kernel.org/r/ZvFGwKfoC4yVjN_X@J2N7QTR9R3 Link: https://bugzilla.kernel.org/show_bug.cgi?id=218854 Reported-by: syzbot+908886656a02769af987@syzkaller.appspotmail.com Tested-by: Andrey Konovalov Cc: Andrew Pinski Cc: Mark Rutland Cc: Will Deacon Signed-off-by: Marco Elver Reviewed-by: Andrey Konovalov Fixes: 7b861a53e46b ("kasan: Bump required compiler version") Link: https://lore.kernel.org/r/20241021120013.3209481-1-elver@google.com Signed-off-by: Will Deacon Signed-off-by: Sasha Levin

update workarounds for gcc "asm goto" issue

2024-02-23T08:24:47+00:00

commit 68fb3ca0e408e00db1c3f8fccdfa19e274c033be upstream. In commit 4356e9f841f7 ("work around gcc bugs with 'asm goto' with outputs") I did the gcc workaround unconditionally, because the cause of the bad code generation wasn't entirely clear. In the meantime, Jakub Jelinek debugged the issue, and has come up with a fix in gcc [2], which also got backported to the still maintained branches of gcc-11, gcc-12 and gcc-13. Note that while the fix technically wasn't in the original gcc-14 branch, Jakub says: "while it is true that no GCC 14 snapshots until today (or whenever the fix will be committed) have the fix, for GCC trunk it is up to the distros to use the latest snapshot if they use it at all and would allow better testing of the kernel code without the workaround, so that if there are other issues they won't be discovered years later. Most userland code doesn't actually use asm goto with outputs..." so we will consider gcc-14 to be fixed - if somebody is using gcc snapshots of the gcc-14 before the fix, they should upgrade. Note that while the bug goes back to gcc-11, in practice other gcc changes seem to have effectively hidden it since gcc-12.1 as per a bisect by Jakub. So even a gcc-14 snapshot without the fix likely doesn't show actual problems. Also, make the default 'asm_goto_output()' macro mark the asm as volatile by hand, because of an unrelated gcc issue [1] where it doesn't match the documented behavior ("asm goto is always volatile"). Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103979 [1] Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113921 [2] Link: https://lore.kernel.org/all/20240208220604.140859-1-seanjc@google.com/ Requested-by: Jakub Jelinek Cc: Uros Bizjak Cc: Nick Desaulniers Cc: Sean Christopherson Cc: Andrew Pinski Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

work around gcc bugs with 'asm goto' with outputs

2024-02-23T08:24:47+00:00

commit 4356e9f841f7fbb945521cef3577ba394c65f3fc upstream. We've had issues with gcc and 'asm goto' before, and we created a 'asm_volatile_goto()' macro for that in the past: see commits 3f0116c3238a ("compiler/gcc4: Add quirk for 'asm goto' miscompilation bug") and a9f180345f53 ("compiler/gcc4: Make quirk for asm_volatile_goto() unconditional"). Then, much later, we ended up removing the workaround in commit 43c249ea0b1e ("compiler-gcc.h: remove ancient workaround for gcc PR 58670") because we no longer supported building the kernel with the affected gcc versions, but we left the macro uses around. Now, Sean Christopherson reports a new version of a very similar problem, which is fixed by re-applying that ancient workaround. But the problem in question is limited to only the 'asm goto with outputs' cases, so instead of re-introducing the old workaround as-is, let's rename and limit the workaround to just that much less common case. It looks like there are at least two separate issues that all hit in this area: (a) some versions of gcc don't mark the asm goto as 'volatile' when it has outputs: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98619 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110420 which is easy to work around by just adding the 'volatile' by hand. (b) Internal compiler errors: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110422 which are worked around by adding the extra empty 'asm' as a barrier, as in the original workaround. but the problem Sean sees may be a third thing since it involves bad code generation (not an ICE) even with the manually added 'volatile'. but the same old workaround works for this case, even if this feels a bit like voodoo programming and may only be hiding the issue. Reported-and-tested-by: Sean Christopherson Link: https://lore.kernel.org/all/20240208220604.140859-1-seanjc@google.com/ Cc: Nick Desaulniers Cc: Uros Bizjak Cc: Jakub Jelinek Cc: Andrew Pinski Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

compiler-gcc: document minimum version for `__no_sanitize_coverage__`

2022-11-09T01:37:20+00:00

The attribute was added in GCC 12.1. This will simplify future cleanups, and is closer to what we do in `compiler_attributes.h`. Link: https://godbolt.org/z/MGbT76j6G Link: https://lkml.kernel.org/r/20221021115956.9947-5-ojeda@kernel.org Signed-off-by: Miguel Ojeda Acked-by: Marco Elver Reviewed-by: Nathan Chancellor Cc: Alexander Potapenko Cc: Andrey Konovalov Cc: Arnd Bergmann Cc: Dan Li Cc: Kees Cook Cc: Kumar Kartikeya Dwivedi Cc: Nick Desaulniers Cc: Uros Bizjak Signed-off-by: Andrew Morton

compiler-gcc: remove attribute support check for `__no_sanitize_undefined__`

2022-11-09T01:37:20+00:00

The attribute was added in GCC 4.9, while the minimum GCC version supported by the kernel is GCC 5.1. Therefore, remove the check. Link: https://godbolt.org/z/GrMeo6fYr Link: https://lkml.kernel.org/r/20221021115956.9947-4-ojeda@kernel.org Signed-off-by: Miguel Ojeda Reviewed-by: Nathan Chancellor Cc: Alexander Potapenko Cc: Andrey Konovalov Cc: Arnd Bergmann Cc: Dan Li Cc: Kees Cook Cc: Kumar Kartikeya Dwivedi Cc: Marco Elver Cc: Nick Desaulniers Cc: Uros Bizjak Signed-off-by: Andrew Morton

compiler-gcc: remove attribute support check for `__no_sanitize_thread__`

2022-11-09T01:37:20+00:00

The attribute was added in GCC 5.1, which matches the minimum GCC version supported by the kernel. Therefore, remove the check. Link: https://godbolt.org/z/vbxKejxbx Link: https://lkml.kernel.org/r/20221021115956.9947-3-ojeda@kernel.org Signed-off-by: Miguel Ojeda Acked-by: Marco Elver Reviewed-by: Nathan Chancellor Cc: Alexander Potapenko Cc: Andrey Konovalov Cc: Arnd Bergmann Cc: Dan Li Cc: Kees Cook Cc: Kumar Kartikeya Dwivedi Cc: Nick Desaulniers Cc: Uros Bizjak Signed-off-by: Andrew Morton

compiler-gcc: remove attribute support check for `__no_sanitize_address__`

2022-11-09T01:37:20+00:00

The attribute was added in GCC 4.8, while the minimum GCC version supported by the kernel is GCC 5.1. Therefore, remove the check. Link: https://godbolt.org/z/84v56vcn8 Link: https://lkml.kernel.org/r/20221021115956.9947-2-ojeda@kernel.org Signed-off-by: Miguel Ojeda Reviewed-by: Nathan Chancellor Cc: Alexander Potapenko Cc: Andrey Konovalov Cc: Arnd Bergmann Cc: Dan Li Cc: Kees Cook Cc: Kumar Kartikeya Dwivedi Cc: Marco Elver Cc: Nick Desaulniers Cc: Uros Bizjak Signed-off-by: Andrew Morton

compiler-gcc: be consistent with underscores use for `no_sanitize`

2022-11-09T01:37:20+00:00

Patch series "compiler-gcc: be consistent with underscores use for `no_sanitize`". This patch (of 5): Other macros that define shorthands for attributes in e.g. `compiler_attributes.h` and elsewhere use underscores. Link: https://lkml.kernel.org/r/20221021115956.9947-1-ojeda@kernel.org Signed-off-by: Miguel Ojeda Reviewed-by: Nathan Chancellor Cc: Marco Elver Cc: Alexander Potapenko Cc: Andrey Konovalov Cc: Arnd Bergmann Cc: Dan Li Cc: Kees Cook Cc: Kumar Kartikeya Dwivedi Cc: Nick Desaulniers Cc: Uros Bizjak Signed-off-by: Andrew Morton

kmsan: introduce __no_sanitize_memory and __no_kmsan_checks

2022-10-03T21:03:19+00:00

__no_sanitize_memory is a function attribute that instructs KMSAN to skip a function during instrumentation. This is needed to e.g. implement the noinstr functions. __no_kmsan_checks is a function attribute that makes KMSAN ignore the uninitialized values coming from the function's inputs, and initialize the function's outputs. Functions marked with this attribute can't be inlined into functions not marked with it, and vice versa. This behavior is overridden by __always_inline. __SANITIZE_MEMORY__ is a macro that's defined iff the file is instrumented with KMSAN. This is not the same as CONFIG_KMSAN, which is defined for every file. Link: https://lkml.kernel.org/r/20220915150417.722975-8-glider@google.com Signed-off-by: Alexander Potapenko Reviewed-by: Marco Elver Cc: Alexander Viro Cc: Alexei Starovoitov Cc: Andrey Konovalov Cc: Andrey Konovalov Cc: Andy Lutomirski Cc: Arnd Bergmann Cc: Borislav Petkov Cc: Christoph Hellwig Cc: Christoph Lameter Cc: David Rientjes Cc: Dmitry Vyukov Cc: Eric Biggers Cc: Eric Biggers Cc: Eric Dumazet Cc: Greg Kroah-Hartman Cc: Herbert Xu Cc: Ilya Leoshkevich Cc: Ingo Molnar Cc: Jens Axboe Cc: Joonsoo Kim Cc: Kees Cook Cc: Mark Rutland Cc: Matthew Wilcox Cc: Michael S. Tsirkin Cc: Pekka Enberg Cc: Peter Zijlstra Cc: Petr Mladek Cc: Stephen Rothwell Cc: Steven Rostedt Cc: Thomas Gleixner Cc: Vasily Gorbik Cc: Vegard Nossum Cc: Vlastimil Babka Signed-off-by: Andrew Morton

compiler-gcc.h: remove ancient workaround for gcc PR 58670

2022-07-18T00:31:38+00:00

The workaround for 'asm goto' miscompilation introduces a compiler barrier quirk that inhibits many useful compiler optimizations. For example, __try_cmpxchg_user compiles to: 11375: 41 8b 4d 00 mov 0x0(%r13),%ecx 11379: 41 8b 02 mov (%r10),%eax 1137c: f0 0f b1 0a lock cmpxchg %ecx,(%rdx) 11380: 0f 94 c2 sete %dl 11383: 84 d2 test %dl,%dl 11385: 75 c4 jne 1134b <...> 11387: 41 89 02 mov %eax,(%r10) where the barrier inhibits flags propagation from asm when compiled with gcc-12. When the mentioned quirk is removed, the following code is generated: 11553: 41 8b 4d 00 mov 0x0(%r13),%ecx 11557: 41 8b 02 mov (%r10),%eax 1155a: f0 0f b1 0a lock cmpxchg %ecx,(%rdx) 1155e: 74 c9 je 11529 <...> 11560: 41 89 02 mov %eax,(%r10) The refered compiler bug: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670 was fixed for gcc-4.8.2. Current minimum required version of GCC is version 5.1 which has the above 'asm goto' miscompilation fixed, so remove the workaround. Link: https://lkml.kernel.org/r/20220624141412.72274-1-ubizjak@gmail.com Signed-off-by: Uros Bizjak Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: Thomas Gleixner Signed-off-by: Andrew Morton