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