tests: verify the auxstr of clone3(2) when --namespace=switchTo is given

* tests/clone3-report-ns-id.c: New file.
* tests/pure_executables.list: Add clone3-report-ns-id.
* tests/.gitignore: Likewise.
* tests/gen_tests.in: New test.

Signed-off-by: Masatake YAMATO <yamato@redhat.com>

tests/.gitignore

@@ -72,6 +72,7 @@ clone3
 clone3-Xabbrev
 clone3-Xraw
 clone3-Xverbose
+clone3-report-ns-id
 clone3-success
 clone3-success-Xabbrev
 clone3-success-Xraw

tests/clone3-report-ns-id.c

@@ -0,0 +1,71 @@
+/*
+ * Check appending auxstr of clone3(2) when --namespace=switchTo is given
+ *
+ * Copyright (c) 2024 The strace developers.
+ * All rights reserved.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "tests.h"
+#include "xmalloc.h"
+
+#include <limits.h>
+#include <linux/sched.h>
+#include <stdio.h>
+#include <sys/socket.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+
+#include "scno.h"
+
+static void
+retrieve_userns(int pid, char *userns_buf, size_t userns_buflen, int fd)
+{
+	char c = 0;
+	if (read(fd, &c, 1) != 1)
+		perror_msg_and_fail("read from the child");
+
+	char *fname = xasprintf("/proc/%d/ns/user", pid);
+	int rc = readlink(fname, userns_buf, userns_buflen - 1);
+	if ((unsigned int) rc >= userns_buflen)
+		perror_msg_and_fail("readlink");
+	userns_buf[rc] = '\0';
+
+	if (write(fd, &c, 1) != 1)
+		perror_msg_and_fail("write to the child");
+}
+
+static void
+child_pause(int fd)
+{
+	char c = 0;
+	if (write(fd, &c, 1) != 1)
+		return;
+	if (read(fd, &c, 1) != 1)
+		return;
+}
+
+int
+main(void)
+{
+	static int child_sockpair[2];
+	if (socketpair(AF_UNIX, SOCK_STREAM, 0, child_sockpair) < 0)
+		perror_msg_and_fail("socketpair");
+
+	struct clone_args arg = { .flags = CLONE_NEWUSER };
+	int pid = syscall(__NR_clone3, &arg, sizeof(arg));
+	if (pid < 0)
+		perror_msg_and_fail("clone3");
+	if (pid > 0) {
+		printf("clone3({flags=CLONE_NEWUSER, exit_signal=0, stack=NULL, stack_size=0}"
+		       ", %zu) = %s ", sizeof(arg), sprintrc(pid));
+
+		char userns[PATH_MAX];
+		retrieve_userns(pid, userns, sizeof(userns), child_sockpair[0]);
+		printf("(%s)\n", userns);
+		puts("+++ exited with 0 +++");
+	} else
+		child_pause(child_sockpair[1]);
+	return 0;
+}

tests/gen_tests.in

@@ -66,6 +66,7 @@ clone3-success-Xabbrev	-einject=clone3:retval=42 -etrace=clone3 -a16 -Xabbrev
 clone3-success-Xraw	-einject=clone3:retval=42 -etrace=clone3 -a16 -Xraw
 clone3-success-Xverbose	-einject=clone3:retval=42 -etrace=clone3 -a16 -Xverbose
 clone_parent +clone_ptrace.test
+clone3-report-ns-id	-etrace=clone3 -a35 -enamespace=switchTo
 clone_parent--quiet-exit +clone_ptrace.test --quiet=exit,personality
 clone_parent-q +clone_ptrace.test -q
 clone_parent-qq +clone_ptrace.test -qq

tests/pure_executables.list

@@ -44,6 +44,7 @@ clone3
 clone3-Xabbrev
 clone3-Xraw
 clone3-Xverbose
+clone3-report-ns-id
 copy_file_range
 creat
 delete_module