tests: increase the child stack size in some tests that invoke clone

Increase the child stack size from the half page size to the full page
size in those few tests that invoke clone syscall.

The former size appears to be insufficient in some build setups.
For example, clang 7 on Ubuntu bionic x86_64 makes ioctl_nsfs test fail
due to child process segfaults.

* tests/clone_parent.c (child_stack_size, clone): Remove.
(do_clone): New macro.
(main): Use it.
* tests/clone_ptrace.c: Likewise.
* tests/ioctl_nsfs.c (child_stack_size, clone): Remove.
(do_clone): New macro.
(test_user_namespace): Use it.

1 files changed, 14 insertions, 7 deletions

diff --git a/tests/ioctl_nsfs.c b/tests/ioctl_nsfs.c
index 74dbe6e94..fd82b4adb 100644
--- a/tests/ioctl_nsfs.c
+++ b/tests/ioctl_nsfs.c
@@ -86,22 +86,27 @@ child(void *arg)
 
 #ifdef IA64
 extern int __clone2(int (*)(void *), void *, size_t, int, void *, ...);
-# define clone(fn, child_stack, flags, arg)	\
-		__clone2(fn, child_stack, get_page_size() / 2, flags, arg)
+# define do_clone(fn_, stack_, size_, flags_, arg_, ...)	\
+	__clone2((fn_), (stack_), (size_), (flags_), (arg_), ## __VA_ARGS__)
+#else
+# define do_clone(fn_, stack_, size_, flags_, arg_, ...)	\
+	clone((fn_), (stack_), (flags_), (arg_), ## __VA_ARGS__)
 #endif
 
 static void
 test_user_namespace(void)
 {
-	pid_t pid;
 	int pipefd[2];
-	int status;
-
 	if (pipe(pipefd))
 		perror_msg_and_fail("pipe");
 
-	pid = clone(child, tail_alloc(get_page_size() / 2),
-		    CLONE_NEWUSER | CLONE_UNTRACED | SIGCHLD, pipefd);
+	const unsigned long child_stack_size = get_page_size();
+	void *const child_stack =
+		tail_alloc(child_stack_size * 2) + child_stack_size;
+
+	const pid_t pid = do_clone(child, child_stack, child_stack_size,
+				   CLONE_NEWUSER | CLONE_UNTRACED | SIGCHLD,
+				   pipefd);
 	if (pid == -1) {
 		perror("clone");
 		return;
@@ -109,6 +114,8 @@ test_user_namespace(void)
 	close(pipefd[0]);
 	test_clone(pid);
 	close(pipefd[1]);
+
+	int status;
 	if (wait(&status) != pid) {
 		perror_msg_and_fail("wait");
 	} else if (status != 0) {