[PATCH 2/2] selftest/x86: test ARCH_SHSTK_UNLOCK

[Bill Roberts <bill.roberts@arm.com>]

One should not be able to use ARCH_SHSTK_UNLOCK via arch_prctl to twiddle
feature bits, test that this is the case.

Signed-off-by: Bill Roberts <bill.roberts@arm.com>
---
 tools/testing/selftests/x86/test_shadow_stack.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/testing/selftests/x86/test_shadow_stack.c b/tools/testing/selftests/x86/test_shadow_stack.c
index 21af54d5f4ea..82a5fefa9df5 100644
--- a/tools/testing/selftests/x86/test_shadow_stack.c
+++ b/tools/testing/selftests/x86/test_shadow_stack.c
@@ -979,6 +979,14 @@ int main(int argc, char *argv[])
 {
 	int ret = 0;
 
+	/* test that we can't use unlock to set shadow stack */
+	if (!ARCH_PRCTL(ARCH_SHSTK_UNLOCK, ARCH_SHSTK_SHSTK)) {
+		printf("[SKIP]\tCould enable Shadow stack via UNLOCK\n");
+		return 1;
+	}
+
+	printf("[OK]\tCouldn't enable Shadow stack via UNLOCK\n");
+
 	if (ARCH_PRCTL(ARCH_SHSTK_ENABLE, ARCH_SHSTK_SHSTK)) {
 		printf("[SKIP]\tCould not enable Shadow stack\n");
 		return 1;
-- 
2.54.0