9a05c494ad4a05cfd583f0274c0a84a82b5f1dc5
[project/fstools.git] / 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 int mount_extroot(void)
28 {
29         char ldlib_path[32];
30         char block_path[32];
31         char kmod_loader[64];
32         struct stat s;
33         pid_t pid;
34
35         if (!extroot_prefix)
36                 return -1;
37
38         sprintf(ldlib_path, "%s/lib", extroot_prefix);
39         sprintf(block_path, "%s/sbin/block", extroot_prefix);
40
41         if (stat(block_path, &s))
42                 return -1;
43
44         sprintf(kmod_loader, "/sbin/kmodloader %s/etc/modules-boot.d/ %s", extroot_prefix, extroot_prefix);
45         system(kmod_loader);
46
47         pid = fork();
48         if (!pid) {
49                 mkdir("/tmp/extroot", 0755);
50                 setenv("LD_LIBRARY_PATH", ldlib_path, 1);
51                 execl(block_path, block_path, "extroot", NULL);
52                 exit(-1);
53         } else if (pid > 0) {
54                 int status;
55
56                 waitpid(pid, &status, 0);
57                 if (!WEXITSTATUS(status)) {
58                         if (find_mount("/tmp/extroot/mnt")) {
59                                 mount("/dev/root", "/", NULL, MS_NOATIME | MS_REMOUNT | MS_RDONLY, 0);
60
61                                 mkdir("/tmp/extroot/mnt/proc", 0755);
62                                 mkdir("/tmp/extroot/mnt/dev", 0755);
63                                 mkdir("/tmp/extroot/mnt/sys", 0755);
64                                 mkdir("/tmp/extroot/mnt/tmp", 0755);
65                                 mkdir("/tmp/extroot/mnt/rom", 0755);
66
67                                 if (mount_move("/tmp/extroot", "", "/mnt")) {
68                                         fprintf(stderr, "moving pivotroot failed - continue normal boot\n");
69                                         umount("/tmp/extroot/mnt");
70                                 } else if (pivot("/mnt", "/rom")) {
71                                         fprintf(stderr, "switching to pivotroot failed - continue normal boot\n");
72                                         umount("/mnt");
73                                 } else {
74                                         umount("/tmp/overlay");
75                                         rmdir("/tmp/overlay");
76                                         rmdir("/tmp/extroot/mnt");
77                                         rmdir("/tmp/extroot");
78                                         return 0;
79                                 }
80                         } else if (find_mount("/tmp/extroot/overlay")) {
81                                 if (mount_move("/tmp/extroot", "", "/overlay")) {
82                                         fprintf(stderr, "moving extroot failed - continue normal boot\n");
83                                         umount("/tmp/extroot/overlay");
84                                 } else if (fopivot("/overlay", "/rom")) {
85                                         fprintf(stderr, "switching to extroot failed - continue normal boot\n");
86                                         umount("/overlay");
87                                 } else {
88                                         umount("/tmp/overlay");
89                                         rmdir("/tmp/overlay");
90                                         rmdir("/tmp/extroot/overlay");
91                                         rmdir("/tmp/extroot");
92                                         return 0;
93                                 }
94                         }
95                 }
96         }
97         return -1;
98 }