switch-root: move switch_root() call into its own .c file

3 files changed, 161 insertions, 89 deletions

diff --git a/src/core/main.c b/src/core/main.c
index 4d09cb7174..22052220f9 100644
--- a/src/core/main.c
+++ b/src/core/main.c
@@ -49,6 +49,7 @@
 #include "virt.h"
 #include "watchdog.h"
 #include "path-util.h"
+#include "switch-root.h"
 
 #include "mount-setup.h"
 #include "loopback-setup.h"
@@ -1173,90 +1174,6 @@ static void test_cgroups(void) {
         sleep(10);
 }
 
-static int do_switch_root(const char *switch_root) {
-        int r=0;
-        /*  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 = -1;
-        struct stat switch_root_stat, sb;
-        bool remove_old_root;
-
-        if (path_equal(switch_root, "/"))
-                return 0;
-
-        if (stat(switch_root, &switch_root_stat) != 0) {
-                r = -errno;
-                log_error("failed to stat directory %s", switch_root);
-                goto fail;
-        }
-
-        remove_old_root = in_initrd();
-
-        for (i = 0; umounts[i] != NULL; i++) {
-                char newmount[PATH_MAX];
-
-                snprintf(newmount, sizeof(newmount), "%s%s", switch_root, umounts[i]);
-
-                if ((stat(newmount, &sb) != 0) || (sb.st_dev != switch_root_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) {
-                        log_error("failed to mount moving %s to %s",
-                                  umounts[i], newmount);
-                        log_error("forcing unmount of %s", umounts[i]);
-                        umount2(umounts[i], MNT_FORCE);
-                }
-        }
-
-        if (chdir(switch_root)) {
-                r = -errno;
-                log_error("failed to change directory to %s", switch_root);
-                goto fail;
-        }
-
-        if (remove_old_root)
-                cfd = open("/", O_RDONLY);
-
-        if (mount(switch_root, "/", NULL, MS_MOVE, NULL) < 0) {
-                r = -errno;
-                log_error("failed to mount moving %s to /", switch_root);
-                goto fail;
-        }
-
-        if (chroot(".")) {
-                r = -errno;
-                log_error("failed to change root");
-                goto fail;
-        }
-
-        if (cfd >= 0) {
-                struct stat rb;
-
-                if (fstat(cfd, &rb)) {
-                        log_error("failed to stat old root directory");
-                        goto fail;
-                }
-
-                rm_rf_children(cfd, false, false, &rb);
-                close(cfd);
-                cfd=-1;
-        }
-
-        return 0;
-
-fail:
-        if (cfd >= 0)
-                close(cfd);
-
-        log_error("Failed to switch root, ignoring: %s", strerror(-r));
-
-        return r;
-}
-
 int main(int argc, char *argv[]) {
         Manager *m = NULL;
         int r, retval = EXIT_FAILURE;
@@ -1271,7 +1188,7 @@ int main(int argc, char *argv[]) {
         int j;
         bool loaded_policy = false;
         bool arm_reboot_watchdog = false;
-        char *switch_root = NULL, *switch_root_init = NULL;
+        char *switch_root_dir = NULL, *switch_root_init = NULL;
 
 #ifdef HAVE_SYSV_COMPAT
         if (getpid() != 1 && strstr(program_invocation_short_name, "init")) {
@@ -1673,7 +1590,7 @@ int main(int argc, char *argv[]) {
 
                 case MANAGER_SWITCH_ROOT:
                         /* Steal the switch root parameters */
-                        switch_root = m->switch_root;
+                        switch_root_dir = m->switch_root;
                         switch_root_init = m->switch_root_init;
                         m->switch_root = m->switch_root_init = NULL;
 
@@ -1728,8 +1645,11 @@ finish:
                  * rebooted while we do that */
                 watchdog_close(true);
 
-                if (switch_root)
-                        do_switch_root(switch_root);
+                if (switch_root_dir) {
+                        r = switch_root(switch_root_dir);
+                        if (r < 0)
+                                log_error("Failed to switch root, ignoring: %s", strerror(-r));
+                }
 
                 args_size = MAX(6, argc+1);
                 args = newa(const char*, args_size);
@@ -1750,7 +1670,7 @@ finish:
 
                         i = 0;
                         args[i++] = SYSTEMD_BINARY_PATH;
-                        if (switch_root)
+                        if (switch_root_dir)
                                 args[i++] = "--switchedroot";
                         args[i++] = arg_running_as == MANAGER_SYSTEM ? "--system" : "--user";
                         args[i++] = "--deserialize";
diff --git a/src/core/switch-root.c b/src/core/switch-root.c
new file mode 100644
index 0000000000..ed0a31e697
--- /dev/null
+++ b/src/core/switch-root.c
@@ -0,0 +1,125 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2012 Harald Hoyer, Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd 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
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <sys/stat.h>
+#include <stdbool.h>
+#include <errno.h>
+#include <string.h>
+#include <sys/mount.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+#include "util.h"
+#include "path-util.h"
+#include "switch-root.h"
+
+int switch_root(const char *new_root) {
+
+        /*  Don't try to unmount/move the old "/", there's no way to do it. */
+        static const char move_mounts[] =
+                "/dev\0"
+                "/proc\0"
+                "/sys\0"
+                "/run\0";
+
+        int r, old_root_fd = -1;
+        struct stat new_root_stat;
+        bool old_root_remove;
+        const char *i;
+
+        if (path_equal(new_root, "/"))
+                return 0;
+
+        old_root_remove = in_initrd();
+
+        if (stat(new_root, &new_root_stat) < 0) {
+                r = -errno;
+                log_error("Failed to stat directory %s: %m", new_root);
+                goto fail;
+        }
+
+        NULSTR_FOREACH(i, move_mounts) {
+                char new_mount[PATH_MAX];
+                struct stat sb;
+
+                snprintf(new_mount, sizeof(new_mount), "%s%s", new_root, i);
+                char_array_0(new_mount);
+
+                if ((stat(new_mount, &sb) < 0) ||
+                    sb.st_dev != new_root_stat.st_dev) {
+
+                        /* Mount point seems to be mounted already or
+                         * stat failed. Unmount the old mount
+                         * point. */
+                        if (umount2(i, MNT_DETACH) < 0)
+                                log_warning("Failed to unmount %s: %m", i);
+                        continue;
+                }
+
+                if (mount(i, new_mount, NULL, MS_MOVE, NULL) < 0) {
+                        log_error("Failed to move mount %s to %s, forcing unmount: %m", i, new_mount);
+
+                        if (umount2(i, MNT_FORCE) < 0)
+                                log_warning("Failed to unmount %s: %m", i);
+                }
+        }
+
+        if (chdir(new_root) < 0) {
+                r = -errno;
+                log_error("Failed to change directory to %s: %m", new_root);
+                goto fail;
+        }
+
+        if (old_root_remove) {
+                old_root_fd = open("/", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_NOCTTY|O_DIRECTORY);
+                if (old_root_fd < 0)
+                        log_warning("Failed to open root directory: %m");
+        }
+
+        if (mount(new_root, "/", NULL, MS_MOVE, NULL) < 0) {
+                r = -errno;
+                log_error("Failed to mount moving %s to /: %m", new_root);
+                goto fail;
+        }
+
+        if (chroot(".") < 0) {
+                r = -errno;
+                log_error("Failed to change root: %m");
+                goto fail;
+        }
+
+        if (old_root_fd >= 0) {
+                struct stat rb;
+
+                if (fstat(old_root_fd, &rb) < 0)
+                        log_warning("Failed to stat old root directory, leaving: %m");
+                else
+                        rm_rf_children(old_root_fd, false, false, &rb);
+        }
+
+        r = 0;
+
+fail:
+        if (old_root_fd >= 0)
+                close_nointr_nofail(old_root_fd);
+
+        return r;
+}
diff --git a/src/core/switch-root.h b/src/core/switch-root.h
new file mode 100644
index 0000000000..0c4cd1e403
--- /dev/null
+++ b/src/core/switch-root.h
@@ -0,0 +1,27 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+#ifndef fooswitchroothfoo
+#define fooswitchroothfoo
+
+/***
+  This file is part of systemd.
+
+  Copyright 2012 Harald Hoyer, Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd 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
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+int switch_root(const char *switch_root);
+
+#endif