kfence: test: use new suite_{init/exit} support, add .kunitconfig

Currently, the kfence test suite could not run via "normal" means since
KUnit didn't support per-suite setup/teardown. So it manually called
internal kunit functions to run itself.
This has some downsides, like missing TAP headers => can't use kunit.py
to run or even parse the test results (w/o tweaks).

Use the newly added support and convert it over, adding a .kunitconfig
so it's even easier to run from kunit.py.

People can now run the test via
$ ./tools/testing/kunit/kunit.py run --kunitconfig=mm/kfence --arch=x86_64
...
[11:02:32] Testing complete. Passed: 23, Failed: 0, Crashed: 0, Skipped: 2, Errors: 0
[11:02:32] Elapsed time: 43.562s total, 0.003s configuring, 9.268s building, 34.281s running

Cc: kasan-dev@googlegroups.com
Signed-off-by: Daniel Latypov <dlatypov@google.com>
Tested-by: David Gow <davidgow@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

mm/kfence/.kunitconfig

+CONFIG_KUNIT=y
+CONFIG_KFENCE=y
+CONFIG_KFENCE_KUNIT_TEST=y
+
+# Additional dependencies.
+CONFIG_FTRACE=y

mm/kfence/kfence_test.c

@@ -826,14 +826,6 @@ static void test_exit(struct kunit *test)
 	test_cache_destroy();
 }
 
-static struct kunit_suite kfence_test_suite = {
-	.name = "kfence",
-	.test_cases = kfence_test_cases,
-	.init = test_init,
-	.exit = test_exit,
-};
-static struct kunit_suite *kfence_test_suites[] = { &kfence_test_suite, NULL };
-
 static void register_tracepoints(struct tracepoint *tp, void *ignore)
 {
 	check_trace_callback_type_console(probe_console);
@@ -847,11 +839,7 @@ static void unregister_tracepoints(struct tracepoint *tp, void *ignore)
 		tracepoint_probe_unregister(tp, probe_console, NULL);
 }
 
-/*
- * We only want to do tracepoints setup and teardown once, therefore we have to
- * customize the init and exit functions and cannot rely on kunit_test_suite().
- */
-static int __init kfence_test_init(void)
+static int kfence_suite_init(struct kunit_suite *suite)
 {
 	/*
 	 * Because we want to be able to build the test as a module, we need to
@@ -859,18 +847,25 @@ static int __init kfence_test_init(void)
 	 * won't work here.
 	 */
 	for_each_kernel_tracepoint(register_tracepoints, NULL);
-	return __kunit_test_suites_init(kfence_test_suites);
+	return 0;
 }
 
-static void kfence_test_exit(void)
+static void kfence_suite_exit(struct kunit_suite *suite)
 {
-	__kunit_test_suites_exit(kfence_test_suites);
 	for_each_kernel_tracepoint(unregister_tracepoints, NULL);
 	tracepoint_synchronize_unregister();
 }
 
-late_initcall_sync(kfence_test_init);
-module_exit(kfence_test_exit);
+static struct kunit_suite kfence_test_suite = {
+	.name = "kfence",
+	.test_cases = kfence_test_cases,
+	.init = test_init,
+	.exit = test_exit,
+	.suite_init = kfence_suite_init,
+	.suite_exit = kfence_suite_exit,
+};
+
+kunit_test_suites(&kfence_test_suite);
 
 MODULE_LICENSE("GPL v2");
 MODULE_AUTHOR("Alexander Potapenko <glider@google.com>, Marco Elver <elver@google.com>");