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

[Bill Roberts]

On 6/29/26 4:46 PM, Edgecombe, Rick P wrote:
On Mon, 2026-06-15 at 14:51 -0500, Bill Roberts wrote:
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.robe...@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;
+       }
More generally, we should not be able to use ARCH_SHSTK_UNLOCK here. Can we make
the comment generic and not checking for a specific bug? Because it does more
than that.

Hey Rick, not really sure how I could make the git commit message and 
the comment
more generic, as they seem really generic, can you please be more 
specific or give me
a blurb you're looking for here?


+
+       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;