From 867a311f231e89b4c9194579e40718f751761ffc Mon Sep 17 00:00:00 2001 From: Alexandre Frade Date: Sat, 31 Aug 2024 16:57:41 +0000 Subject: [PATCH 04/19] kbuild: Remove GCC minimal function alignment Signed-off-by: Alexandre Frade --- Makefile | 7 ------- arch/Kconfig | 12 ------------ include/linux/compiler_types.h | 10 +++++----- 3 files changed, 5 insertions(+), 24 deletions(-) --- a/Makefile +++ b/Makefile @@ -981,15 +981,8 @@ export CC_FLAGS_FPU export CC_FLAGS_NO_FPU ifneq ($(CONFIG_FUNCTION_ALIGNMENT),0) -# Set the minimal function alignment. Use the newer GCC option -# -fmin-function-alignment if it is available, or fall back to -falign-funtions. -# See also CONFIG_CC_HAS_SANE_FUNCTION_ALIGNMENT. -ifdef CONFIG_CC_HAS_MIN_FUNCTION_ALIGNMENT -KBUILD_CFLAGS += -fmin-function-alignment=$(CONFIG_FUNCTION_ALIGNMENT) -else KBUILD_CFLAGS += -falign-functions=$(CONFIG_FUNCTION_ALIGNMENT) endif -endif # arch Makefile may override CC so keep this after arch Makefile is included NOSTDINC_FLAGS += -nostdinc --- a/arch/Kconfig +++ b/arch/Kconfig @@ -1628,18 +1628,6 @@ 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 - config ARCH_NEED_CMPXCHG_1_EMU bool --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -99,17 +99,17 @@ static inline void __chk_io_ptr(const vo * 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 - * 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. + * 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. * * See: * * https://lore.kernel.org/lkml/Y77%2FqVgvaJidFpYt@FVFF77S0Q05N * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88345#c9 */ -#if defined(CONFIG_CC_HAS_SANE_FUNCTION_ALIGNMENT) || (CONFIG_FUNCTION_ALIGNMENT == 0) +#if !defined(CONFIG_CC_IS_GCC) || (CONFIG_FUNCTION_ALIGNMENT == 0) #define __cold __attribute__((__cold__)) #else #define __cold