LXR linux/samples/binderfs/binderfs

   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}
  83