1// SPDX-License-Identifier: GPL-2.0
 2
 3#define _GNU_SOURCE
 4#include <errno.h>
 5#include <fcntl.h>
 6#include <sched.h>
 7#include <stdio.h>
 8#include <stdlib.h>
 9#include <string.h>
10#include <sys/ioctl.h>
11#include <sys/mount.h>
12#include <sys/stat.h>
13#include <sys/types.h>
14#include <unistd.h>
15#include <linux/android/binder.h>
16#include <linux/android/binderfs.h>
17
18int main(int argc, char *argv[])
19{
20	int fd, ret, saved_errno;
21	struct binderfs_device device = { 0 };
22
23	ret = unshare(CLONE_NEWNS);
24	if (ret < 0) {
25		fprintf(stderr, "%s - Failed to unshare mount namespace\n",
26			strerror(errno));
27		exit(EXIT_FAILURE);
28	}
29
30	ret = mount(NULL, "/", NULL, MS_REC | MS_PRIVATE, 0);
31	if (ret < 0) {
32		fprintf(stderr, "%s - Failed to mount / as private\n",
33			strerror(errno));
34		exit(EXIT_FAILURE);
35	}
36
37	ret = mkdir("/dev/binderfs", 0755);
38	if (ret < 0 && errno != EEXIST) {
39		fprintf(stderr, "%s - Failed to create binderfs mountpoint\n",
40			strerror(errno));
41		exit(EXIT_FAILURE);
42	}
43
44	ret = mount(NULL, "/dev/binderfs", "binder", 0, 0);
45	if (ret < 0) {
46		fprintf(stderr, "%s - Failed to mount binderfs\n",
47			strerror(errno));
48		exit(EXIT_FAILURE);
49	}
50
51	memcpy(device.name, "my-binder", strlen("my-binder"));
52
53	fd = open("/dev/binderfs/binder-control", O_RDONLY | O_CLOEXEC);
54	if (fd < 0) {
55		fprintf(stderr, "%s - Failed to open binder-control device\n",
56			strerror(errno));
57		exit(EXIT_FAILURE);
58	}
59
60	ret = ioctl(fd, BINDER_CTL_ADD, &device);
61	saved_errno = errno;
62	close(fd);
63	errno = saved_errno;
64	if (ret < 0) {
65		fprintf(stderr, "%s - Failed to allocate new binder device\n",
66			strerror(errno));
67		exit(EXIT_FAILURE);
68	}
69
70	printf("Allocated new binder device with major %d, minor %d, and name %s\n",
71	       device.major, device.minor, device.name);
72
73	ret = unlink("/dev/binderfs/my-binder");
74	if (ret < 0) {
75		fprintf(stderr, "%s - Failed to delete binder device\n",
76			strerror(errno));
77		exit(EXIT_FAILURE);
78	}
79
80	/* Cleanup happens when the mount namespace dies. */
81	exit(EXIT_SUCCESS);
82}