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 } 84