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switch_root: improve behavior on error; improve help text

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*: make "can't execute '%s'" message uniform
This commit is contained in:
Denis Vlasenko
2009-04-21 20:40:51 +00:00
parent 950bd72966
commit f9d4fc3cf8
10 changed files with 48 additions and 41 deletions
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60
util-linux/switch_root.c
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@ -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]);
}