On Sun, 19 Nov 2023 at 22:29, Maria Yu quic_aiquny@quicinc.com wrote:
Registers r7 is removed in clobber list, so compiler may choose r7 for local variables usage, while r7 will be actually updated by the inline asm code. This caused the runtime behavior wrong. While those kind of reserved registers cannot be set to clobber list because of error like "inline asm clobber list contains reserved registers". Explicitly reserve r7 by adding attribute no-omit-frame-pointer for this file, then in T32 asm code r7 is used as a frame pointer and is not available for use as a general-purpose register. Note that "no-omit-frame-pointer" will make the code size a little bigger to store the stack frame pointer.
Fixes: dd12e97f3c72 ("ARM: kprobes: treat R7 as the frame pointer register in Thumb2 builds") Suggested-by: Ard Biesheuvel ardb@kernel.org Signed-off-by: Maria Yu quic_aiquny@quicinc.com Cc: stable@vger.kernel.org
arch/arm/probes/kprobes/Makefile | 1 + 1 file changed, 1 insertion(+)
diff --git a/arch/arm/probes/kprobes/Makefile b/arch/arm/probes/kprobes/Makefile index 6159010dac4a..b1f21e78950b 100644 --- a/arch/arm/probes/kprobes/Makefile +++ b/arch/arm/probes/kprobes/Makefile @@ -8,6 +8,7 @@ test-kprobes-objs := test-core.o
ifdef CONFIG_THUMB2_KERNEL obj-$(CONFIG_KPROBES) += actions-thumb.o checkers-thumb.o +CFLAGS_actions-thumb.o += -fno-omit-frame-pointer test-kprobes-objs += test-thumb.o else obj-$(CONFIG_KPROBES) += actions-arm.o checkers-arm.o
If Nathan is happy with this, I think we can drop this into the patch tracker.