selftests/harness: Merge TEST_F_FORK() into TEST_F()

Replace Landlock-specific TEST_F_FORK() with an improved TEST_F() which
brings four related changes:

Run TEST_F()'s tests in a grandchild process to make it possible to
drop privileges and delegate teardown to the parent.

Compared to TEST_F_FORK(), simplify handling of the test grandchild
process thanks to vfork(2), and makes it generic (e.g. no explicit
conversion between exit code and _metadata).

Compared to TEST_F_FORK(), run teardown even when tests failed with an
assert thanks to commit 63e6b2a42342 ("selftests/harness: Run TEARDOWN
for ASSERT failures").

Simplify the test harness code by removing the no_print and step fields
which are not used.  I added this feature just after I made
kselftest_harness.h more broadly available but this step counter
remained even though it wasn't needed after all. See commit 369130b63178
("selftests: Enhance kselftest_harness.h to print which assert failed").

Replace spaces with tabs in one line of __TEST_F_IMPL().

Cc: Günther Noack <gnoack@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Will Drewry <wad@chromium.org>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 60 deletions

diff --git a/tools/testing/selftests/landlock/common.h b/tools/testing/selftests/landlock/common.h
index f40146d40763..401e2eb092a3 100644
--- a/tools/testing/selftests/landlock/common.h
+++ b/tools/testing/selftests/landlock/common.h
@@ -23,66 +23,8 @@
 #define __maybe_unused __attribute__((__unused__))
 #endif
 
-/*
- * TEST_F_FORK() is useful when a test drop privileges but the corresponding
- * FIXTURE_TEARDOWN() requires them (e.g. to remove files from a directory
- * where write actions are denied).  For convenience, FIXTURE_TEARDOWN() is
- * also called when the test failed, but not when FIXTURE_SETUP() failed.  For
- * this to be possible, we must not call abort() but instead exit smoothly
- * (hence the step print).
- */
-/* clang-format off */
-#define TEST_F_FORK(fixture_name, test_name) \
-	static void fixture_name##_##test_name##_child( \
-		struct __test_metadata *_metadata, \
-		FIXTURE_DATA(fixture_name) *self, \
-		const FIXTURE_VARIANT(fixture_name) *variant); \
-	__TEST_F_IMPL(fixture_name, test_name, -1, TEST_TIMEOUT_DEFAULT) \
-	{ \
-		int status; \
-		const pid_t child = fork(); \
-		if (child < 0) \
-			abort(); \
-		if (child == 0) { \
-			_metadata->no_print = 1; \
-			fixture_name##_##test_name##_child(_metadata, self, variant); \
-			if (_metadata->skip) \
-				_exit(255); \
-			if (_metadata->passed) \
-				_exit(0); \
-			_exit(_metadata->step); \
-		} \
-		if (child != waitpid(child, &status, 0)) \
-			abort(); \
-		if (WIFSIGNALED(status) || !WIFEXITED(status)) { \
-			_metadata->passed = 0; \
-			_metadata->step = 1; \
-			return; \
-		} \
-		switch (WEXITSTATUS(status)) { \
-		case 0: \
-			_metadata->passed = 1; \
-			break; \
-		case 255: \
-			_metadata->passed = 1; \
-			_metadata->skip = 1; \
-			break; \
-		default: \
-			_metadata->passed = 0; \
-			_metadata->step = WEXITSTATUS(status); \
-			break; \
-		} \
-	} \
-	static void fixture_name##_##test_name##_child( \
-		struct __test_metadata __attribute__((unused)) *_metadata, \
-		FIXTURE_DATA(fixture_name) __attribute__((unused)) *self, \
-		const FIXTURE_VARIANT(fixture_name) \
-			__attribute__((unused)) *variant)
-/* clang-format on */
-
-/* Makes backporting easier. */
-#undef TEST_F
-#define TEST_F(fixture_name, test_name) TEST_F_FORK(fixture_name, test_name)
+/* TEST_F_FORK() should not be used for new tests. */
+#define TEST_F_FORK(fixture_name, test_name) TEST_F(fixture_name, test_name)
 
 #ifndef landlock_create_ruleset
 static inline int