tools/nolibc: add testcase for fork()/waitpid()

On s390 the arguments to clone() which is used by fork() are different
than other archs.
Make sure everything works correctly.
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/testing/selftests/nolibc/nolibc-test.c

@@ -474,6 +474,25 @@ static int test_getpagesize(void)
 	return !c;
 }
 
+static int test_fork(void)
+{
+	int status;
+	pid_t pid = fork();
+
+	switch (pid) {
+	case -1:
+		return 1;
+
+	case 0:
+		exit(123);
+
+	default:
+		pid = waitpid(pid, &status, 0);
+
+		return pid == -1 || !WIFEXITED(status) || WEXITSTATUS(status) != 123;
+	}
+}
+
 /* Run syscall tests between IDs <min> and <max>.
  * Return 0 on success, non-zero on failure.
  */
@@ -530,6 +549,7 @@ int run_syscall(int min, int max)
 		CASE_TEST(dup3_0);            tmp = dup3(0, 100, 0);  EXPECT_SYSNE(1, tmp, -1); close(tmp); break;
 		CASE_TEST(dup3_m1);           tmp = dup3(-1, 100, 0); EXPECT_SYSER(1, tmp, -1, EBADF); if (tmp != -1) close(tmp); break;
 		CASE_TEST(execve_root);       EXPECT_SYSER(1, execve("/", (char*[]){ [0] = "/", [1] = NULL }, NULL), -1, EACCES); break;
+		CASE_TEST(fork);              EXPECT_SYSZR(1, test_fork()); break;
 		CASE_TEST(getdents64_root);   EXPECT_SYSNE(1, test_getdents64("/"), -1); break;
 		CASE_TEST(getdents64_null);   EXPECT_SYSER(1, test_getdents64("/dev/null"), -1, ENOTDIR); break;
 		CASE_TEST(gettimeofday_null); EXPECT_SYSZR(1, gettimeofday(NULL, NULL)); break;