1 files changed, 263 insertions, 0 deletions
diff --git a/sys-utils/switch_root.c b/sys-utils/switch_root.c
new file mode 100644
index 0000000..a85ce24
--- /dev/null
+++ b/sys-utils/switch_root.c
@@ -0,0 +1,263 @@
+/*
+ * switchroot.c - switch to new root directory and start init.
+ *
+ * Copyright 2002-2009 Red Hat, Inc.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors:
+ *	Peter Jones <pjones@redhat.com>
+ *	Jeremy Katz <katzj@redhat.com>
+ */
+#include <sys/mount.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/statfs.h>
+#include <sys/param.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+#include <ctype.h>
+#include <dirent.h>
+#include <getopt.h>
+
+#include "c.h"
+#include "nls.h"
+#include "closestream.h"
+#include "statfs_magic.h"
+
+#ifndef MS_MOVE
+#define MS_MOVE 8192
+#endif
+
+#ifndef MNT_DETACH
+#define MNT_DETACH       0x00000002	/* Just detach from the tree */
+#endif
+
+/* remove all files/directories below dirName -- don't cross mountpoints */
+static int recursiveRemove(int fd)
+{
+	struct stat rb;
+	DIR *dir;
+	int rc = -1;
+	int dfd;
+
+	if (!(dir = fdopendir(fd))) {
+		warn(_("failed to open directory"));
+		goto done;
+	}
+
+	/* fdopendir() precludes us from continuing to use the input fd */
+	dfd = dirfd(dir);
+
+	if (fstat(dfd, &rb)) {
+		warn(_("stat failed"));
+		goto done;
+	}
+
+	while(1) {
+		struct dirent *d;
+		int isdir = 0;
+
+		errno = 0;
+		if (!(d = readdir(dir))) {
+			if (errno) {
+				warn(_("failed to read directory"));
+				goto done;
+			}
+			break;	/* end of directory */
+		}
+
+		if (!strcmp(d->d_name, ".") || !strcmp(d->d_name, ".."))
+			continue;
+#ifdef _DIRENT_HAVE_D_TYPE
+		if (d->d_type == DT_DIR || d->d_type == DT_UNKNOWN)
+#endif
+		{
+			struct stat sb;
+
+			if (fstatat(dfd, d->d_name, &sb, AT_SYMLINK_NOFOLLOW)) {
+				warn(_("stat of %s failed"), d->d_name);
+				continue;
+			}
+
+			/* skip if device is not the same */
+			if (sb.st_dev != rb.st_dev)
+				continue;
+
+			/* remove subdirectories */
+			if (S_ISDIR(sb.st_mode)) {
+				int cfd;
+
+				cfd = openat(dfd, d->d_name, O_RDONLY);
+				if (cfd >= 0) {
+					recursiveRemove(cfd);
+					close(cfd);
+				}
+				isdir = 1;
+			}
+		}
+
+		if (unlinkat(dfd, d->d_name, isdir ? AT_REMOVEDIR : 0))
+			warn(_("failed to unlink %s"), d->d_name);
+	}
+
+	rc = 0;	/* success */
+
+done:
+	if (dir)
+		closedir(dir);
+	return rc;
+}
+
+static int switchroot(const char *newroot)
+{
+	/*  Don't try to unmount the old "/", there's no way to do it. */
+	const char *umounts[] = { "/dev", "/proc", "/sys", "/run", NULL };
+	int i;
+	int cfd;
+	pid_t pid;
+	struct stat newroot_stat, sb;
+
+	if (stat(newroot, &newroot_stat) != 0) {
+		warn(_("stat of %s failed"), newroot);
+		return -1;
+	}
+
+	for (i = 0; umounts[i] != NULL; i++) {
+		char newmount[PATH_MAX];
+
+		snprintf(newmount, sizeof(newmount), "%s%s", newroot, umounts[i]);
+
+		if ((stat(newmount, &sb) != 0) || (sb.st_dev != newroot_stat.st_dev)) {
+			/* mount point seems to be mounted already or stat failed */
+			umount2(umounts[i], MNT_DETACH);
+			continue;
+		}
+
+		if (mount(umounts[i], newmount, NULL, MS_MOVE, NULL) < 0) {
+			warn(_("failed to mount moving %s to %s"),
+				umounts[i], newmount);
+			warnx(_("forcing unmount of %s"), umounts[i]);
+			umount2(umounts[i], MNT_FORCE);
+		}
+	}
+
+	if (chdir(newroot)) {
+		warn(_("failed to change directory to %s"), newroot);
+		return -1;
+	}
+
+	cfd = open("/", O_RDONLY);
+	if (cfd < 0) {
+		warn(_("cannot open %s"), "/");
+		return -1;
+	}
+
+	if (mount(newroot, "/", NULL, MS_MOVE, NULL) < 0) {
+		close(cfd);
+		warn(_("failed to mount moving %s to /"), newroot);
+		return -1;
+	}
+
+	if (chroot(".")) {
+		close(cfd);
+		warn(_("failed to change root"));
+		return -1;
+	}
+
+	pid = fork();
+	if (pid <= 0) {
+		struct statfs stfs;
+
+		if (fstatfs(cfd, &stfs) == 0 &&
+		    (F_TYPE_EQUAL(stfs.f_type, STATFS_RAMFS_MAGIC) ||
+		     F_TYPE_EQUAL(stfs.f_type, STATFS_TMPFS_MAGIC)))
+			recursiveRemove(cfd);
+		else
+			warn(_("old root filesystem is not an initramfs"));
+		if (pid == 0)
+			exit(EXIT_SUCCESS);
+	}
+
+	close(cfd);
+	return 0;
+}
+
+static void __attribute__((__noreturn__)) usage(void)
+{
+	FILE *output = stdout;
+	fputs(USAGE_HEADER, output);
+	fprintf(output, _(" %s [options] <newrootdir> <init> <args to init>\n"),
+		program_invocation_short_name);
+
+	fputs(USAGE_SEPARATOR, output);
+	fputs(_("Switch to another filesystem as the root of the mount tree.\n"), output);
+
+	fputs(USAGE_OPTIONS, output);
+	printf(USAGE_HELP_OPTIONS(16));
+	printf(USAGE_MAN_TAIL("switch_root(8)"));
+
+	exit(EXIT_SUCCESS);
+}
+
+int main(int argc, char *argv[])
+{
+	char *newroot, *init, **initargs;
+	int c;
+	static const struct option longopts[] = {
+		{"version", no_argument, NULL, 'V'},
+		{"help", no_argument, NULL, 'h'},
+		{NULL, 0, NULL, 0}
+	};
+
+	atexit(close_stdout);
+
+	while ((c = getopt_long(argc, argv, "+Vh", longopts, NULL)) != -1)
+		switch (c) {
+		case 'V':
+			printf(UTIL_LINUX_VERSION);
+			return EXIT_SUCCESS;
+		case 'h':
+			usage();
+		default:
+			errtryhelp(EXIT_FAILURE);
+		}
+	if (argc < 3) {
+		warnx(_("not enough arguments"));
+		errtryhelp(EXIT_FAILURE);
+	}
+
+	newroot = argv[1];
+	init = argv[2];
+	initargs = &argv[2];
+
+	if (!*newroot || !*init) {
+		warnx(_("bad usage"));
+		errtryhelp(EXIT_FAILURE);
+	}
+
+	if (switchroot(newroot))
+		errx(EXIT_FAILURE, _("failed. Sorry."));
+
+	if (access(init, X_OK))
+		warn(_("cannot access %s"), init);
+
+	execv(init, initargs);
+	errexec(init);
+}
+