selftests: kselftest_harness: support using xfail

Currently some tests report skip for things they expect to fail
e.g. when given combination of parameters is known to be unsupported.
This is confusing because in an ideal test environment and fully
featured kernel no tests should be skipped.

Selftest summary line already includes xfail and xpass counters,
e.g.:

  Totals: pass:725 fail:0 xfail:0 xpass:0 skip:0 error:0

but there's no way to use it from within the harness.

Add a new per-fixture+variant combination list of test cases
we expect to fail.

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: kuba-moo

tools/testing/selftests/kselftest_harness.h

@@ -803,6 +803,37 @@ struct __fixture_metadata {
 	.prev = &_fixture_global,
 };
 
+struct __test_xfail {
+	struct __fixture_metadata *fixture;
+	struct __fixture_variant_metadata *variant;
+	struct __test_metadata *test;
+	struct __test_xfail *prev, *next;
+};
+
+/**
+ * XFAIL_ADD() - mark variant + test case combination as expected to fail
+ * @fixture_name: name of the fixture
+ * @variant_name: name of the variant
+ * @test_name: name of the test case
+ *
+ * Mark a combination of variant + test case for a given fixture as expected
+ * to fail. Tests marked this way will report XPASS / XFAIL return codes,
+ * instead of PASS / FAIL,and use respective counters.
+ */
+#define XFAIL_ADD(fixture_name, variant_name, test_name) \
+	static struct __test_xfail \
+		_##fixture_name##_##variant_name##_##test_name##_xfail = \
+	{ \
+		.fixture = &_##fixture_name##_fixture_object, \
+		.variant = &_##fixture_name##_##variant_name##_object, \
+		.test = &_##fixture_name##_##test_name##_object, \
+	}; \
+	static void __attribute__((constructor)) \
+		_register_##fixture_name##_##variant_name##_##test_name##_xfail(void) \
+	{ \
+		__register_xfail(&_##fixture_name##_##variant_name##_##test_name##_xfail); \
+	}
+
 static struct __fixture_metadata *__fixture_list = &_fixture_global;
 static int __constructor_order;
 
@@ -817,6 +848,7 @@ static inline void __register_fixture(struct __fixture_metadata *f)
 struct __fixture_variant_metadata {
 	const char *name;
 	const void *data;
+	struct __test_xfail *xfails;
 	struct __fixture_variant_metadata *prev, *next;
 };
 
@@ -866,6 +898,11 @@ static inline void __register_test(struct __test_metadata *t)
 	__LIST_APPEND(t->fixture->tests, t);
 }
 
+static inline void __register_xfail(struct __test_xfail *xf)
+{
+	__LIST_APPEND(xf->variant->xfails, xf);
+}
+
 static inline int __bail(int for_realz, struct __test_metadata *t)
 {
 	/* if this is ASSERT, return immediately. */
@@ -941,7 +978,9 @@ void __wait_for_test(struct __test_metadata *t)
 		fprintf(TH_LOG_STREAM,
 			"# %s: Test terminated by timeout\n", t->name);
 	} else if (WIFEXITED(status)) {
-		if (WEXITSTATUS(status) == KSFT_SKIP) {
+		if (WEXITSTATUS(status) == KSFT_SKIP ||
+		    WEXITSTATUS(status) == KSFT_XPASS ||
+		    WEXITSTATUS(status) == KSFT_XFAIL) {
 			t->exit_code = WEXITSTATUS(status);
 		} else if (t->termsig != -1) {
 			t->exit_code = KSFT_FAIL;
@@ -1110,6 +1149,7 @@ void __run_test(struct __fixture_metadata *f,
 		struct __fixture_variant_metadata *variant,
 		struct __test_metadata *t)
 {
+	struct __test_xfail *xfail;
 	char test_name[LINE_MAX];
 	const char *diagnostic;
 
@@ -1141,6 +1181,13 @@ void __run_test(struct __fixture_metadata *f,
 	ksft_print_msg("         %4s  %s\n",
 		       __test_passed(t) ? "OK" : "FAIL", test_name);
 
+	/* Check if we're expecting this test to fail */
+	for (xfail = variant->xfails; xfail; xfail = xfail->next)
+		if (xfail->test == t)
+			break;
+	if (xfail)
+		t->exit_code = __test_passed(t) ? KSFT_XPASS : KSFT_XFAIL;
+
 	if (t->results->reason[0])
 		diagnostic = t->results->reason;
 	else if (t->exit_code == KSFT_PASS || t->exit_code == KSFT_FAIL)