Contents of /tags/mkinitrd-6_1_0/busybox/util-linux/switch_root.c
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Fri Apr 24 19:09:57 2009 UTC (15 years, 5 months ago) by niro
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Fri Apr 24 19:09:57 2009 UTC (15 years, 5 months ago) by niro
File MIME type: text/plain
File size: 2979 byte(s)
tagged 'mkinitrd-6_1_0'
1 | /* vi: set sw=4 ts=4: */ |
2 | /* Copyright 2005 Rob Landley <rob@landley.net> |
3 | * |
4 | * Switch from rootfs to another filesystem as the root of the mount tree. |
5 | * |
6 | * Licensed under GPL version 2, see file LICENSE in this tarball for details. |
7 | */ |
8 | |
9 | #include "libbb.h" |
10 | #include <sys/vfs.h> |
11 | |
12 | // Make up for header deficiencies. |
13 | #ifndef RAMFS_MAGIC |
14 | #define RAMFS_MAGIC ((unsigned)0x858458f6) |
15 | #endif |
16 | |
17 | #ifndef TMPFS_MAGIC |
18 | #define TMPFS_MAGIC ((unsigned)0x01021994) |
19 | #endif |
20 | |
21 | #ifndef MS_MOVE |
22 | #define MS_MOVE 8192 |
23 | #endif |
24 | |
25 | // Recursively delete contents of rootfs. |
26 | static void delete_contents(const char *directory, dev_t rootdev) |
27 | { |
28 | DIR *dir; |
29 | struct dirent *d; |
30 | struct stat st; |
31 | |
32 | // Don't descend into other filesystems |
33 | if (lstat(directory, &st) || st.st_dev != rootdev) |
34 | return; |
35 | |
36 | // Recursively delete the contents of directories. |
37 | if (S_ISDIR(st.st_mode)) { |
38 | dir = opendir(directory); |
39 | if (dir) { |
40 | while ((d = readdir(dir))) { |
41 | char *newdir = d->d_name; |
42 | |
43 | // Skip . and .. |
44 | if (DOT_OR_DOTDOT(newdir)) |
45 | continue; |
46 | |
47 | // Recurse to delete contents |
48 | newdir = concat_path_file(directory, newdir); |
49 | delete_contents(newdir, rootdev); |
50 | free(newdir); |
51 | } |
52 | closedir(dir); |
53 | |
54 | // Directory should now be empty. Zap it. |
55 | rmdir(directory); |
56 | } |
57 | |
58 | // It wasn't a directory. Zap it. |
59 | } else unlink(directory); |
60 | } |
61 | |
62 | int switch_root_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; |
63 | int switch_root_main(int argc UNUSED_PARAM, char **argv) |
64 | { |
65 | char *newroot, *console = NULL; |
66 | struct stat st1, st2; |
67 | struct statfs stfs; |
68 | dev_t rootdev; |
69 | |
70 | // Parse args (-c console) |
71 | opt_complementary = "-2"; // minimum 2 params |
72 | getopt32(argv, "+c:", &console); // '+': stop parsing at first non-option |
73 | argv += optind; |
74 | |
75 | // Change to new root directory and verify it's a different fs. |
76 | newroot = *argv++; |
77 | |
78 | xchdir(newroot); |
79 | if (lstat(".", &st1) || lstat("/", &st2) || st1.st_dev == st2.st_dev) { |
80 | bb_error_msg_and_die("bad newroot %s", newroot); |
81 | } |
82 | rootdev = st2.st_dev; |
83 | |
84 | // Additional sanity checks: we're about to rm -rf /, so be REALLY SURE |
85 | // we mean it. (I could make this a CONFIG option, but I would get email |
86 | // from all the people who WILL eat their filesystems.) |
87 | if (lstat("/init", &st1) || !S_ISREG(st1.st_mode) || statfs("/", &stfs) |
88 | || (((unsigned)stfs.f_type != RAMFS_MAGIC) && ((unsigned)stfs.f_type != TMPFS_MAGIC)) |
89 | || (getpid() != 1) |
90 | ) { |
91 | bb_error_msg_and_die("not rootfs"); |
92 | } |
93 | |
94 | // Zap everything out of rootdev |
95 | delete_contents("/", rootdev); |
96 | |
97 | // Overmount / with newdir and chroot into it. The chdir is needed to |
98 | // recalculate "." and ".." links. |
99 | if (mount(".", "/", NULL, MS_MOVE, NULL)) |
100 | bb_error_msg_and_die("error moving root"); |
101 | xchroot("."); |
102 | xchdir("/"); |
103 | |
104 | // If a new console specified, redirect stdin/stdout/stderr to that. |
105 | if (console) { |
106 | close(0); |
107 | xopen(console, O_RDWR); |
108 | xdup2(0, 1); |
109 | xdup2(0, 2); |
110 | } |
111 | |
112 | // Exec real init. (This is why we must be pid 1.) |
113 | execv(argv[0], argv); |
114 | bb_perror_msg_and_die("bad init %s", argv[0]); |
115 | } |