/* * Copyright 2011, The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #include #include #include #include #include #include #include #include /* Check to see if /proc/mounts contains any writeable filesystems * backed by a block device. * Return true if none found, else return false. */ static int remount_ro_done(void) { FILE *f; char mount_dev[256]; char mount_dir[256]; char mount_type[256]; char mount_opts[256]; int mount_freq; int mount_passno; int match; int found_rw_fs = 0; f = fopen("/proc/mounts", "r"); if (! f) { /* If we can't read /proc/mounts, just give up */ return 1; } do { match = fscanf(f, "%255s %255s %255s %255s %d %d\n", mount_dev, mount_dir, mount_type, mount_opts, &mount_freq, &mount_passno); mount_dev[255] = 0; mount_dir[255] = 0; mount_type[255] = 0; mount_opts[255] = 0; if ((match == 6) && !strncmp(mount_dev, "/dev/block", 10) && strstr(mount_opts, "rw")) { found_rw_fs = 1; break; } } while (match != EOF); fclose(f); return !found_rw_fs; } /* Remounting filesystems read-only is difficult when there are files * opened for writing or pending deletes on the filesystem. There is * no way to force the remount with the mount(2) syscall. The magic sysrq * 'u' command does an emergency remount read-only on all writable filesystems * that have a block device (i.e. not tmpfs filesystems) by calling * emergency_remount(), which knows how to force the remount to read-only. * Unfortunately, that is asynchronous, and just schedules the work and * returns. The best way to determine if it is done is to read /proc/mounts * repeatedly until there are no more writable filesystems mounted on * block devices. */ static void remount_ro(void) { int fd, cnt = 0; /* Trigger the remount of the filesystems as read-only, * which also marks them clean. */ fd = open("/proc/sysrq-trigger", O_WRONLY); if (fd < 0) { return; } write(fd, "u", 1); close(fd); /* Now poll /proc/mounts till it's done */ while (!remount_ro_done() && (cnt < 50)) { usleep(100000); cnt++; } return; } extern int write_misc(char *reason); int android_reboot(int cmd, int flags, char *arg) { int ret; if (!(flags & ANDROID_RB_FLAG_NO_SYNC)) sync(); if (!(flags & ANDROID_RB_FLAG_NO_REMOUNT_RO)) remount_ro(); switch (cmd) { case ANDROID_RB_RESTART: ret = reboot(RB_AUTOBOOT); break; case ANDROID_RB_POWEROFF: ret = reboot(RB_POWER_OFF); break; case ANDROID_RB_RESTART2: //ret = __reboot(LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, // LINUX_REBOOT_CMD_RESTART2, arg); write_misc(arg); ret = reboot(RB_AUTOBOOT); break; default: ret = -1; } return ret; }