Currently we set -march=armv8.5+memtag when building the MTE selftests, allowing the compiler to emit v8.5 and MTE instructions for anything it generates. This means that we may get code that will generate SIGILLs when run on older systems rather than skipping on non-MTE systems as should be the case. Most toolchains don't select any incompatible instructions but I have seen some reports which suggest that some may be appearing which do so. This is also potentially problematic in that if the compiler chooses to emit any MTE instructions for the C code it may interfere with the MTE usage we are trying to test.

Since the only reason we are specifying this option is to allow us to assemble MTE instructions in mte_helper.S we can avoid these issues by moving to using a .arch directive there and adding the -march explicitly to the toolchain support check instead of the generic CFLAGS.

Signed-off-by: Mark Brown broonie@kernel.org --- tools/testing/selftests/arm64/mte/Makefile | 5 +---- tools/testing/selftests/arm64/mte/mte_helper.S | 2 ++ 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/arm64/mte/Makefile b/tools/testing/selftests/arm64/mte/Makefile index a5a0744423d8..037046f5784e 100644 --- a/tools/testing/selftests/arm64/mte/Makefile +++ b/tools/testing/selftests/arm64/mte/Makefile @@ -11,11 +11,8 @@ LDFLAGS += -pthread SRCS := $(filter-out mte_common_util.c,$(wildcard *.c)) PROGS := $(patsubst %.c,%,$(SRCS))

-#Add mte compiler option -CFLAGS += -march=armv8.5-a+memtag - #check if the compiler works well -mte_cc_support := $(shell if ($(CC) $(CFLAGS) -E -x c /dev/null -o /dev/null 2>&1) then echo "1"; fi) +mte_cc_support := $(shell if ($(CC) $(CFLAGS) -march=armv8.5-a+memtag -E -x c /dev/null -o /dev/null 2>&1) then echo "1"; fi)

ifeq ($(mte_cc_support),1) # Generated binaries to be installed by top KSFT script diff --git a/tools/testing/selftests/arm64/mte/mte_helper.S b/tools/testing/selftests/arm64/mte/mte_helper.S index a02c04cd0aac..a55dbbc56ed1 100644 --- a/tools/testing/selftests/arm64/mte/mte_helper.S +++ b/tools/testing/selftests/arm64/mte/mte_helper.S @@ -3,6 +3,8 @@

#include "mte_def.h"

+.arch armv8.5-a+memtag + #define ENTRY(name) \ .globl name ;\ .p2align 2;\