Re: [PATCH 1/2] selftests/x86/signal: Adjust the test to the kernel's altstack check

[Shuah Khan]

On 4/1/22 4:10 PM, Chang S. Bae wrote:
> The test assumes an insufficient altstack is allowed. Then it raises a
> signal to test the delivery failure due to an altstack overflow.
>
> The kernel now provides an option to tweak sigaltstack()'s sanity check to
> prevent an insufficient altstack. ENOMEM is returned on the check failure.
>
> Adjust the code to skip the test when this option is on.

Mention the option name here and in the Skip message.

> Signed-off-by: Chang S. Bae <chang.seok.bae@xxxxxxxxx>
> Cc: linux-kselftest@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> ---
>   tools/testing/selftests/x86/sigaltstack.c | 12 +++++++++++-
>   1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/x86/sigaltstack.c b/tools/testing/selftests/x86/sigaltstack.c
> index f689af75e979..22a88b764a8e 100644
> --- a/tools/testing/selftests/x86/sigaltstack.c
> +++ b/tools/testing/selftests/x86/sigaltstack.c
> @@ -88,8 +88,18 @@ static void sigalrm(int sig, siginfo_t *info, void *ctx_void)
>   
>   static void test_sigaltstack(void *altstack, unsigned long size)
>   {
> -	if (setup_altstack(altstack, size))
> +	if (setup_altstack(altstack, size)) {
> +		/*
> +		 * The kernel may return ENOMEM when the altstack size
> +		 * is insufficient. Skip the test in this case.
> +		 */
> +		if (errno == ENOMEM && size < at_minstack_size) {
> +			printf("[SKIP]\tThe running kernel disallows an insufficient size.\n");

Please improve this message to clearly why it is okay to skip the test.
Mention that the option to disallowing insufficient is enabled and that
the test can't be run.


> +			return;
> +		}
> +
>   		err(1, "sigaltstack()");
> +	}
>   
>   	sigalrm_expected = (size > at_minstack_size) ? true : false;
>   

With these changes:

Reviewed-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>

thanks,
-- Shuah