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authorThomas Gleixner <tglx@linutronix.de>2022-09-15 14:11:18 +0300
committerPeter Zijlstra <peterz@infradead.org>2022-10-17 17:41:10 +0300
commitbea75b33895f7f87f0c40023e36a2d087e87ffa1 (patch)
tree301d9fc0cc4db3df6746e8163186cab5bf436632 /arch/x86/Makefile
parent8f7c0d8b23c3f5f740a48db31ebadef28af17a22 (diff)
downloadlinux-bea75b33895f7f87f0c40023e36a2d087e87ffa1.tar.xz
x86/Kconfig: Introduce function padding
Now that all functions are 16 byte aligned, add 16 bytes of NOP padding in front of each function. This prepares things for software call stack tracking and kCFI/FineIBT. This significantly increases kernel .text size, around 5.1% on a x86_64-defconfig-ish build. However, per the random access argument used for alignment, these 16 extra bytes are code that wouldn't be used. Performance measurements back this up by showing no significant performance regressions. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20220915111146.950884492@infradead.org
Diffstat (limited to 'arch/x86/Makefile')
-rw-r--r--arch/x86/Makefile6
1 files changed, 6 insertions, 0 deletions
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 415a5d138de4..1640e005092b 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -208,6 +208,12 @@ ifdef CONFIG_SLS
KBUILD_CFLAGS += -mharden-sls=all
endif
+ifdef CONFIG_CALL_THUNKS
+PADDING_CFLAGS := -fpatchable-function-entry=$(CONFIG_FUNCTION_PADDING_BYTES),$(CONFIG_FUNCTION_PADDING_BYTES)
+KBUILD_CFLAGS += $(PADDING_CFLAGS)
+export PADDING_CFLAGS
+endif
+
KBUILD_LDFLAGS += -m elf_$(UTS_MACHINE)
ifdef CONFIG_LTO_CLANG