tools/testing/selftests/pid_namespace/pidns_init_via_setns.c

Source file repositories/reference/linux-study-clean/tools/testing/selftests/pid_namespace/pidns_init_via_setns.c

File Facts

System
Linux kernel
Corpus path
tools/testing/selftests/pid_namespace/pidns_init_via_setns.c
Extension
.c
Size
5501 bytes
Lines
239
Domain
Support Tooling And Documentation
Bucket
tools
Inferred role
Support Tooling And Documentation: implementation source
Status
source implementation candidate

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

if (grandchild == 0) {
			/* Should be init (PID 1) in the new namespace */
			if (getpid() != 1)
				_exit(1);
			_exit(0);
		}

		ASSERT_EQ(0, wait_for_pid(grandchild));
		_exit(0);
	}

	close(pipe_fd[0]);

	ASSERT_EQ(0, unshare(CLONE_NEWPID));

	/* Signal child that the new PID namespace is ready */
	buf = 0;
	ASSERT_EQ(1, write_nointr(pipe_fd[1], &buf, 1));
	close(pipe_fd[1]);

	ASSERT_EQ(0, wait_for_pid(child));
}

/*
 * Similar to pidns_init_via_setns, but:
 *  1. Parent enters a new PID namespace right from the start to be able to
 *     later freely use pid 1001 in it.
 *  2. After forking child, parent also calls unshare(CLONE_NEWUSER)
 *     before unshare(CLONE_NEWPID) so that new old and new pid namespaces have
 *     different user namespace owners.
 *  3. Child uses clone3() with set_tid={1, 1001} instead of fork() and
 *     grandchild checks that it gets desired pids .
 *
 * Flow:
 *  1. Test process creates a new PID namespace and forks a wrapper
 *     (PID 1 in the outer namespace).
 *  2. Wrapper forks a child.
 *  3. Wrapper calls unshare(CLONE_NEWUSER) + unshare(CLONE_NEWPID)
 *     to create an inner PID namespace.
 *  4. Wrapper signals the child via pipe.
 *  5. Child opens wrapper's /proc/<pid>/ns/pid_for_children and calls
 *     setns(fd, CLONE_NEWPID) to join the inner namespace.
 *  6. Child calls clone3() with set_tid={1, 1001}.
 *  7. Grandchild verifies its NSpid ends with "1001 1".
 */

pid_t set_tid[] = {1, 1001};

static int pidns_init_via_setns_set_tid_grandchild(struct __test_metadata *_metadata)
{
	char *line = NULL;
	size_t len = 0;
	int found = 0;
	FILE *gf;

	gf = fopen("/proc/self/status", "r");
	ASSERT_NE(gf, NULL);

	while (getline(&line, &len, gf) != -1) {
		if (strncmp(line, "NSpid:", 6) != 0)
			continue;

		for (int i = 0; i < 2; i++) {
			char *last = strrchr(line, '\t');
			pid_t pid;

			ASSERT_NE(last, NULL);
			ASSERT_EQ(sscanf(last, "%d", &pid), 1);
			ASSERT_EQ(pid, set_tid[i]);
			*last = '\0';
		}

		found = true;
		break;
	}

	free(line);
	fclose(gf);
	ASSERT_TRUE(found);
	return 0;
}

static int pidns_init_via_setns_set_tid_child(struct __test_metadata *_metadata,
					      pid_t parent_pid, int pipe_fd[2])
{
	struct __clone_args args = {
		.exit_signal	= SIGCHLD,
		.set_tid	= ptr_to_u64(set_tid),
		.set_tid_size	= 2,
	};

Annotation

Implementation Notes