hush/util-linux/switch_root.c
Denis Vlasenko 394eebed66 lpd: spool mode added by Vladimir
lpr: more robust error reporting
*: introduce and use xchroot
libbb: full_read/write now will report partial data counts prior to error
isdirectory.c: style fixes

lpd_main                                             249     486    +237
xchroot                                                -      29     +29
get_response_or_say_and_die                          110     139     +29
full_write                                            52      60      +8
full_read                                             55      63      +8
static.newline                                         1       -      -1
switch_root_main                                     404     400      -4
chpst_main                                          1089    1079     -10
getopt32                                            1370    1359     -11
chroot_main                                          115     101     -14
------------------------------------------------------------------------------
(add/remove: 1/1 grow/shrink: 4/4 up/down: 311/-40)           Total: 271 bytes
   text    data     bss     dec     hex filename
 798472     728    7484  806684   c4f1c busybox_old
 798775     728    7484  806987   c504b busybox_unstripped
2008-02-25 20:30:24 +00:00

126 lines
2.9 KiB
C

/* vi: set sw=4 ts=4: */
/* Copyright 2005 Rob Landley <rob@landley.net>
*
* Switch from rootfs to another filesystem as the root of the mount tree.
*
* Licensed under GPL version 2, see file LICENSE in this tarball for details.
*/
#include "libbb.h"
#include <sys/vfs.h>
// Make up for header deficiencies.
#ifndef RAMFS_MAGIC
#define RAMFS_MAGIC 0x858458f6
#endif
#ifndef TMPFS_MAGIC
#define TMPFS_MAGIC 0x01021994
#endif
#ifndef MS_MOVE
#define MS_MOVE 8192
#endif
static dev_t rootdev;
// Recursively delete contents of rootfs.
static void delete_contents(const char *directory)
{
DIR *dir;
struct dirent *d;
struct stat st;
// Don't descend into other filesystems
if (lstat(directory, &st) || st.st_dev != rootdev) return;
// Recursively delete the contents of directories.
if (S_ISDIR(st.st_mode)) {
dir = opendir(directory);
if (dir) {
while ((d = readdir(dir))) {
char *newdir = d->d_name;
// Skip . and ..
if (*newdir=='.' && (!newdir[1] || (newdir[1]=='.' && !newdir[2])))
continue;
// Recurse to delete contents
newdir = alloca(strlen(directory) + strlen(d->d_name) + 2);
sprintf(newdir, "%s/%s", directory, d->d_name);
delete_contents(newdir);
}
closedir(dir);
// Directory should now be empty. Zap it.
rmdir(directory);
}
// It wasn't a directory. Zap it.
} else unlink(directory);
}
int switch_root_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int switch_root_main(int argc, char **argv)
{
char *newroot, *console = NULL;
struct stat st1, st2;
struct statfs stfs;
// Parse args (-c console)
opt_complementary = "-2"; // minimum 2 params
getopt32(argv, "+c:", &console); // '+': stop parsing at first non-option
argv += optind;
// Change to new root directory and verify it's a different fs.
newroot = *argv++;
xchdir(newroot);
if (lstat(".", &st1) || lstat("/", &st2) || st1.st_dev == st2.st_dev) {
bb_error_msg_and_die("bad newroot %s", newroot);
}
rootdev = st2.st_dev;
// Additional sanity checks: we're about to rm -rf /, so be REALLY SURE
// we mean it. (I could make this a CONFIG option, but I would get email
// from all the people who WILL eat their filesystems.)
if (lstat("/init", &st1) || !S_ISREG(st1.st_mode) || statfs("/", &stfs) ||
(stfs.f_type != RAMFS_MAGIC && stfs.f_type != TMPFS_MAGIC) ||
getpid() != 1)
{
bb_error_msg_and_die("not rootfs");
}
// Zap everything out of rootdev
delete_contents("/");
// Overmount / with newdir and chroot into it. The chdir is needed to
// recalculate "." and ".." links.
if (mount(".", "/", NULL, MS_MOVE, NULL))
bb_error_msg_and_die("error moving root");
xchroot(".");
xchdir("/");
// If a new console specified, redirect stdin/stdout/stderr to that.
if (console) {
close(0);
xopen(console, O_RDWR);
dup2(0, 1);
dup2(0, 2);
}
// Exec real init. (This is why we must be pid 1.)
execv(argv[0], argv);
bb_perror_msg_and_die("bad init %s", argv[0]);
}