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| author |  Mark Rutland <mark.rutland@arm.com>
| 2023-04-12 17:01:32 +0100 |
|---|---|---|
| committer |  Will Deacon <will@kernel.org>
| 2023-04-13 12:27:11 +0100 |
| commit | 9df3f5082ff94c55e84523a28c040445220b2f64 (patch) | |
| tree | 3c194b8b27d8030be66306272834df1fb769c188 /arch/arm64/include/asm/compiler.h | |
| parent | arm64: stacktrace: always inline core stacktrace functions (diff) | |
| download | linux-9df3f5082ff94c55e84523a28c040445220b2f64.tar.gz linux-9df3f5082ff94c55e84523a28c040445220b2f64.tar.bz2 linux-9df3f5082ff94c55e84523a28c040445220b2f64.zip | |
arm64: avoid redundant PAC stripping in __builtin_return_address()
In old versions of GCC and Clang, __builtin_return_address() did not
strip the PAC. This was not the behaviour we desired, and so we wrapped
this with code to strip the PAC in commit:
689eae42afd7a916 ("arm64: mask PAC bits of __builtin_return_address")
Since then, both GCC and Clang decided that __builtin_return_address()
*should* strip the PAC, and the existing behaviour was a bug.
GCC was fixed in 11.1.0, with those fixes backported to 10.2.0, 9.4.0,
8.5.0, but not earlier:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94891
Clang was fixed in 12.0.0, though this was not backported:
https://reviews.llvm.org/D75044
When using a compiler whose __builtin_return_address() strips the PAC,
our wrapper to strip the PAC is redundant. Similarly, when pointer
authentication is not in use within the kernel pointers will not have a
PAC, and so there's no point stripping those pointers.
To avoid this redundant work, this patch updates the
__builtin_return_address() wrapper to only be used when in-kernel
pointer authentication is configured and the compiler's
__builtin_return_address() does not strip the PAC.
This is a cleanup/optimization, and not a fix that requires backporting.
Stripping a PAC should be an idempotent operation, and so redundantly
stripping the PAC is not harmful.
There should be no functional change as a result of this patch.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Amit Daniel Kachhap <amit.kachhap@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Kristina Martsenko <kristina.martsenko@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20230412160134.306148-2-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'arch/arm64/include/asm/compiler.h')
| -rw-r--r-- | arch/arm64/include/asm/compiler.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/compiler.h b/arch/arm64/include/asm/compiler.h index 6fb2e6bcc392..9033a0b2f46a 100644 --- a/arch/arm64/include/asm/compiler.h +++ b/arch/arm64/include/asm/compiler.h @@ -20,7 +20,10 @@ ((ptr & BIT_ULL(55)) ? (ptr | ptrauth_kernel_pac_mask()) : \ (ptr & ~ptrauth_user_pac_mask())) +#if defined(CONFIG_ARM64_PTR_AUTH_KERNEL) && \ + !defined(CONFIG_BUILTIN_RETURN_ADDRESS_STRIPS_PAC) #define __builtin_return_address(val) \ (void *)(ptrauth_clear_pac((unsigned long)__builtin_return_address(val))) +#endif #endif /* __ASM_COMPILER_H */ |