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author | Rob Landley <rob@landley.net> | 2005-10-27 22:55:50 +0000 |
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committer | Rob Landley <rob@landley.net> | 2005-10-27 22:55:50 +0000 |
commit | 0f34a821ab99e4936c7aa4974f58784442172211 (patch) | |
tree | 1341f988aa02110b3a997edc52e54bcc27ea1000 /util-linux/switch_root.c | |
parent | 2454ebd85ddbbdc0971e9b848032f66e23245ebe (diff) | |
download | busybox-w32-0f34a821ab99e4936c7aa4974f58784442172211.tar.gz busybox-w32-0f34a821ab99e4936c7aa4974f58784442172211.tar.bz2 busybox-w32-0f34a821ab99e4936c7aa4974f58784442172211.zip |
Add a switch_root utility (like kconfig's utils/run_init.c, although not
actuall using any of that code). This is needed because pivot_root doesn't
work right under initramfs. (See the menuconfig help.)
Diffstat (limited to 'util-linux/switch_root.c')
-rw-r--r-- | util-linux/switch_root.c | 118 |
1 files changed, 118 insertions, 0 deletions
diff --git a/util-linux/switch_root.c b/util-linux/switch_root.c new file mode 100644 index 000000000..242699560 --- /dev/null +++ b/util-linux/switch_root.c | |||
@@ -0,0 +1,118 @@ | |||
1 | /* vi:set ts=4:*/ | ||
2 | |||
3 | #include <dirent.h> | ||
4 | #include <fcntl.h> | ||
5 | #include <stdio.h> | ||
6 | #include <sys/mount.h> | ||
7 | #include <sys/stat.h> | ||
8 | #include <sys/types.h> | ||
9 | #include <sys/vfs.h> | ||
10 | #include <unistd.h> | ||
11 | |||
12 | #include "busybox.h" | ||
13 | |||
14 | // Make up for header deficiencies. | ||
15 | |||
16 | #ifndef RAMFS_MAGIC | ||
17 | #define RAMFS_MAGIC 0x858458f6 | ||
18 | #endif | ||
19 | |||
20 | #ifndef TMPFS_MAGIC | ||
21 | #define TMPFS_MAGIC 0x01021994 | ||
22 | #endif | ||
23 | |||
24 | #ifndef MS_MOVE | ||
25 | #define MS_MOVE 8192 | ||
26 | #endif | ||
27 | |||
28 | dev_t rootdev; | ||
29 | |||
30 | // Recursively delete contents of rootfs. | ||
31 | |||
32 | static void delete_contents(char *directory) | ||
33 | { | ||
34 | DIR *dir; | ||
35 | struct dirent *d; | ||
36 | struct stat st; | ||
37 | |||
38 | // Don't descend into other filesystems | ||
39 | if (stat(directory,&st) || st.st_dev != rootdev) return; | ||
40 | |||
41 | // Recursively delete the contents of directories. | ||
42 | if (S_ISDIR(st.st_mode)) { | ||
43 | if((dir = opendir(directory))) { | ||
44 | while ((d = readdir(dir))) { | ||
45 | char *newdir=d->d_name; | ||
46 | |||
47 | // Skip . and .. | ||
48 | if(*newdir=='.' && (!newdir[1] || (newdir[1]=='.' && !newdir[2]))) | ||
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 | printf("rmdir %s\n",directory); // rmdir(directory); | ||
60 | } | ||
61 | |||
62 | // It wasn't a directory. Zap it. | ||
63 | |||
64 | } else printf("unlink %s\n",directory); //unlink(directory); | ||
65 | } | ||
66 | |||
67 | int switch_root_main(int argc, char *argv[]) | ||
68 | { | ||
69 | char *newroot, *console="/dev/console"; | ||
70 | struct stat st1, st2; | ||
71 | struct statfs stfs; | ||
72 | |||
73 | // Parse args (-c console) | ||
74 | |||
75 | bb_opt_complementally="-2"; | ||
76 | bb_getopt_ulflags(argc,argv,"c:",&console); | ||
77 | |||
78 | // Change to new root directory and verify it's a different fs. | ||
79 | |||
80 | newroot=argv[optind++]; | ||
81 | |||
82 | if (chdir(newroot) || stat(".", &st1) || stat("/", &st2) || | ||
83 | st1.st_dev == st2.st_dev) | ||
84 | { | ||
85 | bb_error_msg_and_die("bad newroot %s",newroot); | ||
86 | } | ||
87 | rootdev=st2.st_dev; | ||
88 | |||
89 | // Additional sanity checks: we're about to rm -rf /, so be REALLY SURE | ||
90 | // we mean it. (I could make this a CONFIG option, but I would get email | ||
91 | // from all the people who WILL eat their filesystemss.) | ||
92 | |||
93 | if (stat("/init", &st1) || !S_ISREG(st1.st_mode) || statfs("/", &stfs) || | ||
94 | (stfs.f_type != RAMFS_MAGIC && stfs.f_type != TMPFS_MAGIC) || | ||
95 | getpid() != 1) | ||
96 | { | ||
97 | bb_error_msg_and_die("not rootfs"); | ||
98 | } | ||
99 | |||
100 | // Zap everything out of rootdev | ||
101 | delete_contents("/"); | ||
102 | |||
103 | // Overmount / with newdir | ||
104 | |||
105 | if (mount(".", "/", NULL, MS_MOVE, NULL) || chdir("/")) | ||
106 | bb_error_msg_and_die("moving root"); | ||
107 | |||
108 | // Reopen stdin/stdout/stderr to /dev/console | ||
109 | close(0); | ||
110 | if(open(console, O_RDWR) < 0) | ||
111 | bb_error_msg_and_die("Bad console '%s'",console); | ||
112 | dup2(0, 1); | ||
113 | dup2(0, 2); | ||
114 | |||
115 | // Exec real init. (This is why we must be pid 1.) | ||
116 | execv(argv[optind],argv+optind+1); | ||
117 | bb_error_msg_and_die("Bad init '%s'",argv[optind]); | ||
118 | } | ||