[PATCH] selftests/x86: report a skip when shadow stack cannot be enabled

[Sasha Levin <sashal@kernel.org>]

test_shadow_stack prints "[SKIP] Could not enable Shadow stack" when
ARCH_SHSTK_ENABLE fails, as it does on CPUs without shadow stack support
and on kernels built without CONFIG_X86_USER_SHADOW_STACK, but then exits
with 1, so the kselftest runner reports a failure.

Exit with KSFT_SKIP instead.

Fixes: 81f30337ef4f ("selftests/x86: Add shadow stack test")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
Found with KernelCI's x86 builds, which leave
CONFIG_X86_USER_SHADOW_STACK unset. Tested on an AMD EPYC 9655P with
KernelCI's x86_64 build of next-20261104: the test now exits with 4
instead of 1.

 tools/testing/selftests/x86/test_shadow_stack.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/x86/test_shadow_stack.c b/tools/testing/selftests/x86/test_shadow_stack.c
index 3d6ca33edba42..f7051ea525d4e 100644
--- a/tools/testing/selftests/x86/test_shadow_stack.c
+++ b/tools/testing/selftests/x86/test_shadow_stack.c
@@ -36,6 +36,8 @@
 #include <linux/elf.h>
 #include <linux/perf_event.h>
 
+#include "kselftest.h"
+
 /*
  * Define the ABI defines if needed, so people can run the tests
  * without building the headers.
@@ -1061,7 +1063,7 @@ int main(int argc, char *argv[])
 
 	if (ARCH_PRCTL(ARCH_SHSTK_ENABLE, ARCH_SHSTK_SHSTK)) {
 		printf("[SKIP]\tCould not enable Shadow stack\n");
-		return 1;
+		return KSFT_SKIP;
 	}
 
 	if (ARCH_PRCTL(ARCH_SHSTK_DISABLE, ARCH_SHSTK_SHSTK)) {
-- 
2.53.0