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authorGravatar Denis Vlasenko <vda.linux@googlemail.com>2009-04-21 20:40:51 +0000
committerGravatar Denis Vlasenko <vda.linux@googlemail.com>2009-04-21 20:40:51 +0000
commitf9d4fc3cf8ca91dbebfa305c5c08f8781caa1a0f (patch)
treeb341f97661b629cc112ebe09933c044ebb31a6f7 /util-linux/switch_root.c
parent950bd729665cecf1fbee65bc6e57e087c93aaab6 (diff)
downloadbusybox-f9d4fc3cf8ca91dbebfa305c5c08f8781caa1a0f.tar.gz
busybox-f9d4fc3cf8ca91dbebfa305c5c08f8781caa1a0f.tar.bz2
switch_root: improve behavior on error; improve help text
*: make "can't execute '%s'" message uniform
Diffstat (limited to 'util-linux/switch_root.c')
-rw-r--r--util-linux/switch_root.c62
1 files changed, 34 insertions, 28 deletions
diff --git a/util-linux/switch_root.c b/util-linux/switch_root.c
index 08aa72597..f9e3444d5 100644
--- a/util-linux/switch_root.c
+++ b/util-linux/switch_root.c
@@ -5,11 +5,10 @@
*
* 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.
+// Make up for header deficiencies
#ifndef RAMFS_MAGIC
#define RAMFS_MAGIC ((unsigned)0x858458f6)
#endif
@@ -22,7 +21,7 @@
#define MS_MOVE 8192
#endif
-// Recursively delete contents of rootfs.
+// Recursively delete contents of rootfs
static void delete_contents(const char *directory, dev_t rootdev)
{
DIR *dir;
@@ -33,7 +32,7 @@ static void delete_contents(const char *directory, dev_t rootdev)
if (lstat(directory, &st) || st.st_dev != rootdev)
return;
- // Recursively delete the contents of directories.
+ // Recursively delete the contents of directories
if (S_ISDIR(st.st_mode)) {
dir = opendir(directory);
if (dir) {
@@ -51,42 +50,47 @@ static void delete_contents(const char *directory, dev_t rootdev)
}
closedir(dir);
- // Directory should now be empty. Zap it.
+ // Directory should now be empty, zap it
rmdir(directory);
}
-
- // It wasn't a directory. Zap it.
- } else unlink(directory);
+ } else {
+ // It wasn't a directory, zap it
+ unlink(directory);
+ }
}
int switch_root_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int switch_root_main(int argc UNUSED_PARAM, char **argv)
{
char *newroot, *console = NULL;
- struct stat st1, st2;
+ struct stat st;
struct statfs stfs;
dev_t rootdev;
// Parse args (-c console)
opt_complementary = "-2"; // minimum 2 params
- getopt32(argv, "+c:", &console); // '+': stop parsing at first non-option
+ getopt32(argv, "+c:", &console); // '+': stop at first non-option
argv += optind;
-
- // Change to new root directory and verify it's a different fs.
newroot = *argv++;
+ // Change to new root directory and verify it's a different fs
xchdir(newroot);
- if (lstat(".", &st1) || lstat("/", &st2) || st1.st_dev == st2.st_dev) {
- bb_error_msg_and_die("bad newroot %s", newroot);
+ xstat("/", &st);
+ rootdev = st.st_dev;
+ xstat(".", &st);
+ if (st.st_dev == rootdev || getpid() != 1) {
+ // Show usage, it says new root must be a mountpoint
+ // and we must be PID 1
+ bb_show_usage();
}
- 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)
- || (((unsigned)stfs.f_type != RAMFS_MAGIC) && ((unsigned)stfs.f_type != TMPFS_MAGIC))
- || (getpid() != 1)
+
+ // 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 destroy their filesystems.
+ statfs("/", &stfs); // this never fails
+ if (lstat("/init", &st) != 0 || !S_ISREG(st.st_mode)
+ || ((unsigned)stfs.f_type != RAMFS_MAGIC
+ && (unsigned)stfs.f_type != TMPFS_MAGIC)
) {
bb_error_msg_and_die("not rootfs");
}
@@ -94,14 +98,16 @@ int switch_root_main(int argc UNUSED_PARAM, char **argv)
// Zap everything out of rootdev
delete_contents("/", rootdev);
- // Overmount / with newdir and chroot into it. The chdir is needed to
- // recalculate "." and ".." links.
- if (mount(".", "/", NULL, MS_MOVE, NULL))
+ // Overmount / with newdir and chroot into it
+ if (mount(".", "/", NULL, MS_MOVE, NULL)) {
+ // For example, fails when newroot is not a mountpoint
bb_perror_msg_and_die("error moving root");
+ }
+ // The chdir is needed to recalculate "." and ".." links
xchroot(".");
xchdir("/");
- // If a new console specified, redirect stdin/stdout/stderr to that.
+ // If a new console specified, redirect stdin/stdout/stderr to it
if (console) {
close(0);
xopen(console, O_RDWR);
@@ -109,7 +115,7 @@ int switch_root_main(int argc UNUSED_PARAM, char **argv)
xdup2(0, 2);
}
- // Exec real init. (This is why we must be pid 1.)
+ // Exec real init
execv(argv[0], argv);
- bb_perror_msg_and_die("bad init %s", argv[0]);
+ bb_perror_msg_and_die("can't execute '%s'", argv[0]);
}