selftests/harness: Add 30 second timeout per test

In order to keep tests from hanging forever, this adds an alarm signal
to each test run. This assumes an individual test doesn't take longer
than 30 seconds.
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/kselftest_harness.h

@@ -696,6 +696,7 @@ void __run_test(struct __test_metadata *t)
 	t->passed = 1;
 	t->trigger = 0;
 	printf("[ RUN      ] %s\n", t->name);
+	alarm(30);
 	child_pid = fork();
 	if (child_pid < 0) {
 		printf("ERROR SPAWNING TEST CHILD\n");
@@ -744,6 +745,7 @@ void __run_test(struct __test_metadata *t)
 		}
 	}
 	printf("[     %4s ] %s\n", (t->passed ? "OK" : "FAIL"), t->name);
+	alarm(0);
 }
 
 static int test_harness_run(int __attribute__((unused)) argc,