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| author | Petr Pavlu <petr.pavlu@suse.com> | 2024-02-22 14:35:00 +0100 |
|---|---|---|
| committer | Masahiro Yamada <masahiroy@kernel.org> | 2024-02-25 18:04:26 +0900 |
| commit | 5270316c9fec8cc99aa0e0a258509c5c7f789d12 (patch) | |
| tree | 4e51d320f23a8ac5d41d2298bf641eb2c9d43a85 /arch/Kconfig | |
| parent | c31f96a00f652a96a1a097b0c6a333509560900f (diff) | |
| download | linux-5270316c9fec8cc99aa0e0a258509c5c7f789d12.tar.gz | |
kbuild: Use -fmin-function-alignment when available
GCC recently added option -fmin-function-alignment, which should appear
in GCC 14. Unlike -falign-functions, this option causes all functions to
be aligned at the specified value, including the cold ones.
In particular, when an arm64 kernel is built with
DYNAMIC_FTRACE_WITH_CALL_OPS=y, the 8-byte function alignment is
required for correct functionality. This was done by -falign-functions=8
and having workarounds in the kernel to force the compiler to follow
this alignment. The new -fmin-function-alignment option directly
guarantees it.
Detect availability of -fmin-function-alignment and use it instead of
-falign-functions when present. Introduce CC_HAS_SANE_FUNCTION_ALIGNMENT
and enable __cold to work as expected when it is set.
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Diffstat (limited to 'arch/Kconfig')
| -rw-r--r-- | arch/Kconfig | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/arch/Kconfig b/arch/Kconfig index a5af0edd3eb8f..bd6c6335efac8 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -1507,4 +1507,16 @@ config FUNCTION_ALIGNMENT default 4 if FUNCTION_ALIGNMENT_4B default 0 +config CC_HAS_MIN_FUNCTION_ALIGNMENT + # Detect availability of the GCC option -fmin-function-alignment which + # guarantees minimal alignment for all functions, unlike + # -falign-functions which the compiler ignores for cold functions. + def_bool $(cc-option, -fmin-function-alignment=8) + +config CC_HAS_SANE_FUNCTION_ALIGNMENT + # Set if the guaranteed alignment with -fmin-function-alignment is + # available or extra care is required in the kernel. Clang provides + # strict alignment always, even with -falign-functions. + def_bool CC_HAS_MIN_FUNCTION_ALIGNMENT || CC_IS_CLANG + endmenu |