kselftest/arm64: signal: Allow tests to be incompatible with features

Some features may invalidate some tests, for example by supporting an
operation which would trap otherwise. Allow tests to list features that
they are incompatible with so we can cover the case where a signal will
be generated without disruption on systems where that won't happen.

Signed-off-by: Mark Brown <[e-mail]>
Reviewed-by: Shuah Khan <[e-mail]>
Acked-by: Catalin Marinas <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Will Deacon <[e-mail]>

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

···
 	char			*name;
 	char			*descr;
 	unsigned long		feats_required;
+	unsigned long		feats_incompatible;
 	/* bitmask of effectively supported feats: populated at run-time */
 	unsigned long		feats_supported;
 	bool			initialized;

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

···
 {
 	size_t flen = MAX_FEATS_SZ - 1;
 
+	feats_string[0] = '\0';
+
 	for (int i = 0; i < FMAX_END; i++) {
 		if (feats & (1UL << i)) {
 			size_t tlen = strlen(feats_names[i]);
···
 		td->minsigstksz = MINSIGSTKSZ;
 	fprintf(stderr, "Detected MINSTKSIGSZ:%d\n", td->minsigstksz);
 
-	if (td->feats_required) {
+	if (td->feats_required || td->feats_incompatible) {
 		td->feats_supported = 0;
 		/*
 		 * Checking for CPU required features using both the
···
 		if (getauxval(AT_HWCAP) & HWCAP_SVE)
 			td->feats_supported |= FEAT_SVE;
 		if (feats_ok(td)) {
-			fprintf(stderr,
-				"Required Features: [%s] supported\n",
-				feats_to_string(td->feats_required &
-						td->feats_supported));
+			if (td->feats_required & td->feats_supported)
+				fprintf(stderr,
+					"Required Features: [%s] supported\n",
+					feats_to_string(td->feats_required &
+							td->feats_supported));
+			if (!(td->feats_incompatible & td->feats_supported))
+				fprintf(stderr,
+					"Incompatible Features: [%s] absent\n",
+					feats_to_string(td->feats_incompatible));
 		} else {
-			fprintf(stderr,
-				"Required Features: [%s] NOT supported\n",
-				feats_to_string(td->feats_required &
-						~td->feats_supported));
+			if ((td->feats_required & td->feats_supported) !=
+			    td->feats_supported)
+				fprintf(stderr,
+					"Required Features: [%s] NOT supported\n",
+					feats_to_string(td->feats_required &
+							~td->feats_supported));
+			if (td->feats_incompatible & td->feats_supported)
+				fprintf(stderr,
+					"Incompatible Features: [%s] supported\n",
+					feats_to_string(td->feats_incompatible &
+							~td->feats_supported));
+
+
 			td->result = KSFT_SKIP;
 			return 0;
 		}

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

···
 
 static inline bool feats_ok(struct tdescr *td)
 {
+	if (td->feats_incompatible & td->feats_supported)
+		return false;
 	return (td->feats_required & td->feats_supported) == td->feats_required;
 }