Re: [PATCH v13 07/12] KVM: selftests: Report stacktraces SIGBUS, SIGSEGV, SIGILL, and SIGFPE by default

["Garg, Shivank" <shivankg@amd.com>]

On 10/16/2025 10:58 PM, Sean Christopherson wrote:
> Register handlers for signals for all selftests that are likely happen due
> to test (or kernel) bugs, and explicitly fail tests on unexpected signals
> so that users get a stack trace, i.e. don't have to go spelunking to do
> basic triage.
> 
> Register the handlers as early as possible, to catch as many unexpected
> signals as possible, and also so that the common code doesn't clobber a
> handler that's installed by test (or arch) code.
> 
> Tested-by: Ackerley Tng <ackerleytng@google.com>
> Reviewed-by: Ackerley Tng <ackerleytng@google.com>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
>  tools/testing/selftests/kvm/lib/kvm_util.c | 24 ++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index 8b60b767224b..0c3a6a40d1a9 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -2290,11 +2290,35 @@ __weak void kvm_selftest_arch_init(void)
>  {
>  }
>  
> +static void report_unexpected_signal(int signum)
> +{
> +#define KVM_CASE_SIGNUM(sig)					\
> +	case sig: TEST_FAIL("Unexpected " #sig " (%d)\n", signum)
> +
> +	switch (signum) {
> +	KVM_CASE_SIGNUM(SIGBUS);
> +	KVM_CASE_SIGNUM(SIGSEGV);
> +	KVM_CASE_SIGNUM(SIGILL);
> +	KVM_CASE_SIGNUM(SIGFPE);
> +	default:
> +		TEST_FAIL("Unexpected signal %d\n", signum);
> +	}
> +}
> +
>  void __attribute((constructor)) kvm_selftest_init(void)
>  {
> +	struct sigaction sig_sa = {
> +		.sa_handler = report_unexpected_signal,
> +	};
> +
>  	/* Tell stdout not to buffer its content. */
>  	setbuf(stdout, NULL);
>  
> +	sigaction(SIGBUS, &sig_sa, NULL);
> +	sigaction(SIGSEGV, &sig_sa, NULL);
> +	sigaction(SIGILL, &sig_sa, NULL);
> +	sigaction(SIGFPE, &sig_sa, NULL);
> +
>  	guest_random_seed = last_guest_seed = random();
>  	pr_info("Random seed: 0x%x\n", guest_random_seed);
>  

Reviewed-by: Shivank Garg <shivankg@amd.com>
Tested-by: Shivank Garg <shivankg@amd.com>