--- /dev/null
+/* -*- c-file-style: "linux" -*-
+ * ostree_switch_root.c - switch to new root directory and start init.
+ * Copyright 2011 Colin Walters <walters@verbum.org>
+ *
+ * Based of switch_root.c from util-linux.
+ * 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>
+ * Colin Walters <walters@verbum.org>
+ */
+#define _GNU_SOURCE
+#include <sys/mount.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/param.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdarg.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+#include <ctype.h>
+#include <dirent.h>
+
+static int
+perrorv (const char *format, ...)
+{
+ va_list args;
+ char buf[PATH_MAX];
+ char *p;
+
+ p = strerror_r (errno, buf, sizeof (buf));
+
+ va_start (args, format);
+
+ vfprintf (stderr, format, args);
+ fprintf (stderr, ": %s\n", p);
+
+ va_end (args);
+
+ return 0;
+}
+
+/* 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))) {
+ perrorv("failed to open directory");
+ goto done;
+ }
+
+ /* fdopendir() precludes us from continuing to use the input fd */
+ dfd = dirfd(dir);
+
+ if (fstat(dfd, &rb)) {
+ perrorv("failed to stat directory");
+ goto done;
+ }
+
+ while(1) {
+ struct dirent *d;
+
+ errno = 0;
+ if (!(d = readdir(dir))) {
+ if (errno) {
+ perrorv("failed to read directory");
+ goto done;
+ }
+ break; /* end of directory */
+ }
+
+ if (!strcmp(d->d_name, ".") || !strcmp(d->d_name, ".."))
+ continue;
+
+ if (d->d_type == DT_DIR) {
+ struct stat sb;
+
+ if (fstatat(dfd, d->d_name, &sb, AT_SYMLINK_NOFOLLOW)) {
+ perrorv("failed to stat %s", d->d_name);
+ continue;
+ }
+
+ /* remove subdirectories if device is same as dir */
+ if (sb.st_dev == rb.st_dev) {
+ int cfd;
+
+ cfd = openat(dfd, d->d_name, O_RDONLY);
+ if (cfd >= 0) {
+ recursiveRemove(cfd);
+ close(cfd);
+ }
+ } else
+ continue;
+ }
+
+ if (unlinkat(dfd, d->d_name,
+ d->d_type == DT_DIR ? AT_REMOVEDIR : 0))
+ perrorv("failed to unlink %s", d->d_name);
+ }
+
+ rc = 0; /* success */
+
+done:
+ if (dir)
+ closedir(dir);
+ return rc;
+}
+
+static int make_readonly(const char *tree)
+{
+ if (mount(tree, tree, NULL, MS_BIND, NULL) < 0) {
+ perrorv("Failed to do initial RO bind mount %s", tree);
+ return -1;
+ }
+ if (mount(tree, tree, NULL, MS_BIND | MS_REMOUNT | MS_RDONLY, NULL) < 0) {
+ perrorv("Failed to remount RO bind mount %s", tree);
+ return -1;
+ }
+ return 0;
+}
+
+
+static int switchroot(const char *newroot, const char *subroot)
+{
+ const char *root_bind_mounts[] = { "/home", "/root", "/var", NULL };
+ int i;
+ int orig_cfd;
+ int new_cfd;
+ pid_t pid;
+ char srcpath[PATH_MAX];
+ char destpath[PATH_MAX];
+
+ orig_cfd = open("/", O_RDONLY);
+ new_cfd = open(newroot, O_RDONLY);
+
+ /* For now just remount the rootfs r/w. Should definitely
+ * handle this better later... (famous last words)
+ */
+ if (mount(newroot, newroot, NULL, MS_REMOUNT & ~MS_RDONLY, NULL) < 0) {
+ perrorv("failed to remount / read/write", newroot);
+ return -1;
+ }
+
+ for (i = 0; root_bind_mounts[i] != NULL; i++) {
+ snprintf(srcpath, sizeof(srcpath), "%s%s", newroot, root_bind_mounts[i]);
+ snprintf(destpath, sizeof(destpath), "%s/%s%s", newroot, subroot, root_bind_mounts[i]);
+ if (mount(srcpath, destpath, NULL, MS_BIND & ~MS_RDONLY, NULL) < 0) {
+ perrorv("failed to bind mount %s to %s", srcpath, destpath);
+ return -1;
+ }
+ }
+
+ if (chdir(newroot)) {
+ perrorv("failed to change directory to %s", newroot);
+ return -1;
+ }
+
+ if (mount(newroot, "/", NULL, MS_MOVE, NULL) < 0) {
+ perrorv("failed to mount moving %s to /", newroot);
+ return -1;
+ }
+
+ if (fchdir (new_cfd) < 0) {
+ perrorv("failed to fchdir back to initrd");
+ return -1;
+ }
+
+ if (chroot(subroot) < 0) {
+ perrorv("failed to change root to %s", subroot);
+ return -1;
+ }
+
+ if (orig_cfd >= 0) {
+ pid = fork();
+ if (pid <= 0) {
+ recursiveRemove(orig_cfd);
+ if (pid == 0)
+ exit(EXIT_SUCCESS);
+ }
+ close(orig_cfd);
+ }
+ close(new_cfd);
+ return 0;
+}
+
+static void usage(FILE *output)
+{
+ fprintf(output, "usage: %s <newrootdir> <subroot> <init> <args to init>\n",
+ program_invocation_short_name);
+ exit(output == stderr ? EXIT_FAILURE : EXIT_SUCCESS);
+}
+
+int main(int argc, char *argv[])
+{
+ char *newroot, *subroot, *init, **initargs;
+
+ if (argc < 3)
+ usage(stderr);
+
+ if ((!strcmp(argv[1], "--help") || !strcmp(argv[1], "-h")))
+ usage(stdout);
+
+ newroot = argv[1];
+ subroot = argv[2];
+ init = argv[3];
+ initargs = &argv[3];
+
+ if (!*newroot || !*init)
+ usage(stderr);
+
+ if (switchroot(newroot, subroot))
+ exit(1);
+
+ if (access(init, X_OK))
+ perrorv("cannot access %s", init);
+
+ execv(init, initargs);
+ exit(1);
+}
+
projects / ostree.git / commitdiff