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 --- Makefile | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'Makefile') diff --git a/Makefile b/Makefile index bc54a6cc8dc5..d84c0fb215fd 100644 --- a/Makefile +++ b/Makefile @@ -974,8 +974,15 @@ export CC_FLAGS_CFI endif 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 -- cgit v1.2.3