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
18 int 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 }
83
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