libfstools/extroot.c

   1 /*
   2  * Copyright (C) 2014 John Crispin <blogic@openwrt.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU Lesser General Public License version 2.1
   6  * as published by the Free Software Foundation
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  */
  13
  14 #include <unistd.h>
  15 #include <stdlib.h>
  16 #include <stdio.h>
  17 #include <string.h>
  18 #include <sys/mount.h>
  19 #include <sys/types.h>
  20 #include <sys/stat.h>
  21 #include <sys/wait.h>
  22
  23 #include "libfstools.h"
  24
  25 char const *extroot_prefix = NULL;
  26
  27 /*
  28  * This will execute "block extroot" and make use of mounted extroot or return
  29  * an error.
  30  */
  31 int mount_extroot(void)
  32 {
  33         char ldlib_path[32];
  34         char block_path[32];
  35         char kmod_loader[64];
  36         struct stat s;
  37         pid_t pid;
  38
  39         if (!extroot_prefix)
  40                 return -1;
  41
  42         sprintf(ldlib_path, "%s/lib", extroot_prefix);
  43         sprintf(block_path, "%s/sbin/block", extroot_prefix);
  44
  45         if (stat(block_path, &s))
  46                 return -1;
  47
  48         sprintf(kmod_loader, "/sbin/kmodloader %s/etc/modules-boot.d/ %s", extroot_prefix, extroot_prefix);
  49         system(kmod_loader);
  50
  51         pid = fork();
  52         if (!pid) {
  53                 mkdir("/tmp/extroot", 0755);
  54                 setenv("LD_LIBRARY_PATH", ldlib_path, 1);
  55                 execl(block_path, block_path, "extroot", NULL);
  56                 exit(-1);
  57         } else if (pid > 0) {
  58                 int status;
  59
  60                 waitpid(pid, &status, 0);
  61                 if (!WEXITSTATUS(status)) {
  62                         if (find_mount("/tmp/extroot/mnt")) {
  63                                 mount("/dev/root", "/", NULL, MS_NOATIME | MS_REMOUNT | MS_RDONLY, 0);
  64
  65                                 mkdir("/tmp/extroot/mnt/proc", 0755);
  66                                 mkdir("/tmp/extroot/mnt/dev", 0755);
  67                                 mkdir("/tmp/extroot/mnt/sys", 0755);
  68                                 mkdir("/tmp/extroot/mnt/tmp", 0755);
  69                                 mkdir("/tmp/extroot/mnt/rom", 0755);
  70
  71                                 if (mount_move("/tmp/extroot", "", "/mnt")) {
  72                                         fprintf(stderr, "moving pivotroot failed - continue normal boot\n");
  73                                         umount("/tmp/extroot/mnt");
  74                                 } else if (pivot("/mnt", "/rom")) {
  75                                         fprintf(stderr, "switching to pivotroot failed - continue normal boot\n");
  76                                         umount("/mnt");
  77                                 } else {
  78                                         umount("/tmp/overlay");
  79                                         rmdir("/tmp/overlay");
  80                                         rmdir("/tmp/extroot/mnt");
  81                                         rmdir("/tmp/extroot");
  82                                         return 0;
  83                                 }
  84                         } else if (find_mount("/tmp/extroot/overlay")) {
  85                                 if (mount_move("/tmp/extroot", "", "/overlay")) {
  86                                         fprintf(stderr, "moving extroot failed - continue normal boot\n");
  87                                         umount("/tmp/extroot/overlay");
  88                                 } else if (fopivot("/overlay", "/rom")) {
  89                                         fprintf(stderr, "switching to extroot failed - continue normal boot\n");
  90                                         umount("/overlay");
  91                                 } else {
  92                                         umount("/tmp/overlay");
  93                                         rmdir("/tmp/overlay");
  94                                         rmdir("/tmp/extroot/overlay");
  95                                         rmdir("/tmp/extroot");
  96                                         return 0;
  97                                 }
  98                         }
  99                 }
 100         }
 101         return -1;
 102 }