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authorPetr Pavlu <petr.pavlu@suse.com>2024-02-22 14:35:00 +0100
committerMasahiro Yamada <masahiroy@kernel.org>2024-02-25 18:04:26 +0900
commit5270316c9fec8cc99aa0e0a258509c5c7f789d12 (patch)
tree4e51d320f23a8ac5d41d2298bf641eb2c9d43a85 /Makefile
parentc31f96a00f652a96a1a097b0c6a333509560900f (diff)
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 'Makefile')
-rw-r--r--Makefile7
1 files changed, 7 insertions, 0 deletions
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