From 5270316c9fec8cc99aa0e0a258509c5c7f789d12 Mon Sep 17 00:00:00 2001 From: Petr Pavlu Date: Thu, 22 Feb 2024 14:35:00 +0100 Subject: 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 Reviewed-by: Nathan Chancellor Acked-by: Mark Rutland Signed-off-by: Masahiro Yamada --- include/linux/compiler_types.h | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'include') diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h index 0caf354cb94b..fb8888678687 100644 --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -99,17 +99,17 @@ static inline void __chk_io_ptr(const volatile void __iomem *ptr) { } * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute * * When -falign-functions=N is in use, we must avoid the cold attribute as - * contemporary versions of GCC drop the alignment for cold functions. Worse, - * GCC can implicitly mark callees of cold functions as cold themselves, so - * it's not sufficient to add __function_aligned here as that will not ensure - * that callees are correctly aligned. + * GCC drops the alignment for cold functions. Worse, GCC can implicitly mark + * callees of cold functions as cold themselves, so it's not sufficient to add + * __function_aligned here as that will not ensure that callees are correctly + * aligned. * * See: * * https://lore.kernel.org/lkml/Y77%2FqVgvaJidFpYt@FVFF77S0Q05N * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88345#c9 */ -#if !defined(CONFIG_CC_IS_GCC) || (CONFIG_FUNCTION_ALIGNMENT == 0) +#if defined(CONFIG_CC_HAS_SANE_FUNCTION_ALIGNMENT) || (CONFIG_FUNCTION_ALIGNMENT == 0) #define __cold __attribute__((__cold__)) #else #define __cold -- cgit