kselftest/arm64: Allow signals tests to specify an expected si_code

Currently we ignore si_code unless the expected signal is a SIGSEGV, in
which case we enforce it being SEGV_ACCERR. Allow test cases to specify
exactly which si_code should be generated so we can validate this, and
test for other segfault codes.

Reviewed-by: Thiago Jung Bauermann <[email protected]>
Signed-off-by: Mark Brown <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Catalin Marinas <[email protected]>

Author: broonie

tools/testing/selftests/arm64/signal/test_signals.h

@@ -71,6 +71,10 @@ struct tdescr {
 	 * Zero when no signal is expected on success
 	 */
 	int			sig_ok;
+	/*
+	 * expected si_code for sig_ok, or 0 to not check
+	 */
+	int			sig_ok_code;
 	/* signum expected on unsupported CPU features. */
 	int			sig_unsupp;
 	/* a timeout in second for test completion */

tools/testing/selftests/arm64/signal/test_signals_utils.c

@@ -143,16 +143,25 @@ static bool handle_signal_ok(struct tdescr *td,
 			"current->token ZEROED...test is probably broken!\n");
 		abort();
 	}
-	/*
-	 * Trying to narrow down the SEGV to the ones generated by Kernel itself
-	 * via arm64_notify_segfault(). This is a best-effort check anyway, and
-	 * the si_code check may need to change if this aspect of the kernel
-	 * ABI changes.
-	 */
-	if (td->sig_ok == SIGSEGV && si->si_code != SEGV_ACCERR) {
-		fprintf(stdout,
-			"si_code != SEGV_ACCERR...test is probably broken!\n");
-		abort();
+	if (td->sig_ok_code) {
+		if (si->si_code != td->sig_ok_code) {
+			fprintf(stdout, "si_code is %d not %d\n",
+				si->si_code, td->sig_ok_code);
+			abort();
+		}
+	} else {
+		/*
+		 * Trying to narrow down the SEGV to the ones
+		 * generated by Kernel itself via
+		 * arm64_notify_segfault(). This is a best-effort
+		 * check anyway, and the si_code check may need to
+		 * change if this aspect of the kernel ABI changes.
+		 */
+		if (td->sig_ok == SIGSEGV && si->si_code != SEGV_ACCERR) {
+			fprintf(stdout,
+				"si_code != SEGV_ACCERR...test is probably broken!\n");
+			abort();
+		}
 	}
 	td->pass = 1;
 	/*