Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
samples: add binderfs sample program
This adds a simple sample program mounting binderfs and adding, then
removing a binder device. Hopefully, it will be helpful to users who want
to know how binderfs is supposed to be used.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
authored by
Christian Brauner
and committed by
Jonathan Corbet
9762dc14
35283f56
+92
-1
+7
samples/Kconfig
+7
samples/Kconfig
···
147
147
Specifically it does *not* include any legacy vga stuff.
148
148
Device looks a lot like "qemu -device secondary-vga".
149
149
150
+
config SAMPLE_ANDROID_BINDERFS
151
+
bool "Build Android binderfs example"
152
+
depends on CONFIG_ANDROID_BINDERFS
153
+
help
154
+
Builds a sample program to illustrate the use of the Android binderfs
155
+
filesystem.
156
+
150
157
config SAMPLE_STATX
151
158
bool "Build example extended-stat using code"
152
159
depends on BROKEN
+1
-1
samples/Makefile
+1
-1
samples/Makefile
+1
samples/binderfs/Makefile
+1
samples/binderfs/Makefile
···
1
+
obj-$(CONFIG_SAMPLE_ANDROID_BINDERFS) += binderfs_example.o
+83
samples/binderfs/binderfs_example.c
+83
samples/binderfs/binderfs_example.c
···
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
+
size_t len;
22
+
struct binderfs_device device = { 0 };
23
+
24
+
ret = unshare(CLONE_NEWNS);
25
+
if (ret < 0) {
26
+
fprintf(stderr, "%s - Failed to unshare mount namespace\n",
27
+
strerror(errno));
28
+
exit(EXIT_FAILURE);
29
+
}
30
+
31
+
ret = mount(NULL, "/", NULL, MS_REC | MS_PRIVATE, 0);
32
+
if (ret < 0) {
33
+
fprintf(stderr, "%s - Failed to mount / as private\n",
34
+
strerror(errno));
35
+
exit(EXIT_FAILURE);
36
+
}
37
+
38
+
ret = mkdir("/dev/binderfs", 0755);
39
+
if (ret < 0 && errno != EEXIST) {
40
+
fprintf(stderr, "%s - Failed to create binderfs mountpoint\n",
41
+
strerror(errno));
42
+
exit(EXIT_FAILURE);
43
+
}
44
+
45
+
ret = mount(NULL, "/dev/binderfs", "binder", 0, 0);
46
+
if (ret < 0) {
47
+
fprintf(stderr, "%s - Failed to mount binderfs\n",
48
+
strerror(errno));
49
+
exit(EXIT_FAILURE);
50
+
}
51
+
52
+
memcpy(device.name, "my-binder", strlen("my-binder"));
53
+
54
+
fd = open("/dev/binderfs/binder-control", O_RDONLY | O_CLOEXEC);
55
+
if (fd < 0) {
56
+
fprintf(stderr, "%s - Failed to open binder-control device\n",
57
+
strerror(errno));
58
+
exit(EXIT_FAILURE);
59
+
}
60
+
61
+
ret = ioctl(fd, BINDER_CTL_ADD, &device);
62
+
saved_errno = errno;
63
+
close(fd);
64
+
errno = saved_errno;
65
+
if (ret < 0) {
66
+
fprintf(stderr, "%s - Failed to allocate new binder device\n",
67
+
strerror(errno));
68
+
exit(EXIT_FAILURE);
69
+
}
70
+
71
+
printf("Allocated new binder device with major %d, minor %d, and name %s\n",
72
+
device.major, device.minor, device.name);
73
+
74
+
ret = unlink("/dev/binderfs/my-binder");
75
+
if (ret < 0) {
76
+
fprintf(stderr, "%s - Failed to delete binder device\n",
77
+
strerror(errno));
78
+
exit(EXIT_FAILURE);
79
+
}
80
+
81
+
/* Cleanup happens when the mount namespace dies. */
82
+
exit(EXIT_SUCCESS);
83
+
}