diff options
| 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/Kconfig | |
| parent | b5ecc19e684eee1df32a035b7d981932f344fc67 (diff) | |
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/Kconfig')
| -rw-r--r-- | arch/arm64/Kconfig | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 1023e896d46b..d69b624b3083 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -362,6 +362,20 @@ config ARCH_PROC_KCORE_TEXT config BROKEN_GAS_INST def_bool !$(as-instr,1:\n.inst 0\n.rept . - 1b\n\nnop\n.endr\n) +config BUILTIN_RETURN_ADDRESS_STRIPS_PAC + bool + # Clang's __builtin_return_adddress() strips the PAC since 12.0.0 + # https://reviews.llvm.org/D75044 + default y if CC_IS_CLANG && (CLANG_VERSION >= 120000) + # GCC's __builtin_return_address() strips the PAC since 11.1.0, + # and this was backported to 10.2.0, 9.4.0, 8.5.0, but not earlier + # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94891 + default y if CC_IS_GCC && (GCC_VERSION >= 110100) + default y if CC_IS_GCC && (GCC_VERSION >= 100200) && (GCC_VERSION < 110000) + default y if CC_IS_GCC && (GCC_VERSION >= 90400) && (GCC_VERSION < 100000) + default y if CC_IS_GCC && (GCC_VERSION >= 80500) && (GCC_VERSION < 90000) + default n + config KASAN_SHADOW_OFFSET hex depends on KASAN_GENERIC || KASAN_SW_TAGS |