[1770] | 1 | /* vi: set sw=4 ts=4: */
|
---|
[821] | 2 | /* Copyright 2005 Rob Landley <rob@landley.net>
|
---|
| 3 | *
|
---|
| 4 | * Switch from rootfs to another filesystem as the root of the mount tree.
|
---|
| 5 | *
|
---|
[1770] | 6 | * Licensed under GPL version 2, see file LICENSE in this tarball for details.
|
---|
[821] | 7 | */
|
---|
| 8 |
|
---|
[1770] | 9 | #include "libbb.h"
|
---|
[821] | 10 | #include <sys/vfs.h>
|
---|
| 11 |
|
---|
| 12 |
|
---|
| 13 | // Make up for header deficiencies.
|
---|
| 14 |
|
---|
| 15 | #ifndef RAMFS_MAGIC
|
---|
| 16 | #define RAMFS_MAGIC 0x858458f6
|
---|
| 17 | #endif
|
---|
| 18 |
|
---|
| 19 | #ifndef TMPFS_MAGIC
|
---|
| 20 | #define TMPFS_MAGIC 0x01021994
|
---|
| 21 | #endif
|
---|
| 22 |
|
---|
| 23 | #ifndef MS_MOVE
|
---|
| 24 | #define MS_MOVE 8192
|
---|
| 25 | #endif
|
---|
| 26 |
|
---|
[1770] | 27 | static dev_t rootdev;
|
---|
[821] | 28 |
|
---|
| 29 | // Recursively delete contents of rootfs.
|
---|
| 30 |
|
---|
[1770] | 31 | static void delete_contents(const char *directory)
|
---|
[821] | 32 | {
|
---|
| 33 | DIR *dir;
|
---|
| 34 | struct dirent *d;
|
---|
| 35 | struct stat st;
|
---|
| 36 |
|
---|
| 37 | // Don't descend into other filesystems
|
---|
[1770] | 38 | if (lstat(directory, &st) || st.st_dev != rootdev) return;
|
---|
[821] | 39 |
|
---|
| 40 | // Recursively delete the contents of directories.
|
---|
| 41 | if (S_ISDIR(st.st_mode)) {
|
---|
[1770] | 42 | dir = opendir(directory);
|
---|
| 43 | if (dir) {
|
---|
[821] | 44 | while ((d = readdir(dir))) {
|
---|
[1770] | 45 | char *newdir = d->d_name;
|
---|
[821] | 46 |
|
---|
| 47 | // Skip . and ..
|
---|
[1770] | 48 | if (*newdir=='.' && (!newdir[1] || (newdir[1]=='.' && !newdir[2])))
|
---|
[821] | 49 | continue;
|
---|
| 50 |
|
---|
| 51 | // Recurse to delete contents
|
---|
| 52 | newdir = alloca(strlen(directory) + strlen(d->d_name) + 2);
|
---|
| 53 | sprintf(newdir, "%s/%s", directory, d->d_name);
|
---|
| 54 | delete_contents(newdir);
|
---|
| 55 | }
|
---|
| 56 | closedir(dir);
|
---|
| 57 |
|
---|
| 58 | // Directory should now be empty. Zap it.
|
---|
| 59 | rmdir(directory);
|
---|
| 60 | }
|
---|
| 61 |
|
---|
| 62 | // It wasn't a directory. Zap it.
|
---|
| 63 |
|
---|
| 64 | } else unlink(directory);
|
---|
| 65 | }
|
---|
| 66 |
|
---|
[1770] | 67 | int switch_root_main(int argc, char **argv);
|
---|
| 68 | int switch_root_main(int argc, char **argv)
|
---|
[821] | 69 | {
|
---|
[1770] | 70 | char *newroot, *console = NULL;
|
---|
[821] | 71 | struct stat st1, st2;
|
---|
| 72 | struct statfs stfs;
|
---|
| 73 |
|
---|
| 74 | // Parse args (-c console)
|
---|
| 75 |
|
---|
[1770] | 76 | opt_complementary = "-2";
|
---|
| 77 | getopt32(argv, "c:", &console);
|
---|
| 78 | argv += optind;
|
---|
[821] | 79 |
|
---|
| 80 | // Change to new root directory and verify it's a different fs.
|
---|
| 81 |
|
---|
[1770] | 82 | newroot = *argv++;
|
---|
[821] | 83 |
|
---|
[1770] | 84 | xchdir(newroot);
|
---|
| 85 | if (lstat(".", &st1) || lstat("/", &st2) || st1.st_dev == st2.st_dev) {
|
---|
| 86 | bb_error_msg_and_die("bad newroot %s", newroot);
|
---|
[821] | 87 | }
|
---|
[1770] | 88 | rootdev = st2.st_dev;
|
---|
[821] | 89 |
|
---|
| 90 | // Additional sanity checks: we're about to rm -rf /, so be REALLY SURE
|
---|
| 91 | // we mean it. (I could make this a CONFIG option, but I would get email
|
---|
[1770] | 92 | // from all the people who WILL eat their filesystems.)
|
---|
[821] | 93 |
|
---|
| 94 | if (lstat("/init", &st1) || !S_ISREG(st1.st_mode) || statfs("/", &stfs) ||
|
---|
| 95 | (stfs.f_type != RAMFS_MAGIC && stfs.f_type != TMPFS_MAGIC) ||
|
---|
| 96 | getpid() != 1)
|
---|
| 97 | {
|
---|
| 98 | bb_error_msg_and_die("not rootfs");
|
---|
| 99 | }
|
---|
| 100 |
|
---|
| 101 | // Zap everything out of rootdev
|
---|
| 102 |
|
---|
| 103 | delete_contents("/");
|
---|
| 104 |
|
---|
| 105 | // Overmount / with newdir and chroot into it. The chdir is needed to
|
---|
| 106 | // recalculate "." and ".." links.
|
---|
| 107 |
|
---|
[1770] | 108 | if (mount(".", "/", NULL, MS_MOVE, NULL) || chroot("."))
|
---|
| 109 | bb_error_msg_and_die("error moving root");
|
---|
| 110 | xchdir("/");
|
---|
[821] | 111 |
|
---|
| 112 | // If a new console specified, redirect stdin/stdout/stderr to that.
|
---|
| 113 |
|
---|
| 114 | if (console) {
|
---|
| 115 | close(0);
|
---|
[1770] | 116 | xopen(console, O_RDWR);
|
---|
[821] | 117 | dup2(0, 1);
|
---|
| 118 | dup2(0, 2);
|
---|
| 119 | }
|
---|
| 120 |
|
---|
| 121 | // Exec real init. (This is why we must be pid 1.)
|
---|
[1770] | 122 | execv(argv[0], argv);
|
---|
| 123 | bb_perror_msg_and_die("bad init %s", argv[0]);
|
---|
[821] | 124 | }
|
---|