119 lines
3.1 KiB
C
119 lines
3.1 KiB
C
/*
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* Copyright 2011, The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <unistd.h>
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#include <sys/reboot.h>
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#include <sys/syscall.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <mntent.h>
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#include <stdio.h>
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#include <string.h>
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#include <cutils/android_reboot.h>
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#define UNUSED __attribute__((unused))
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/* Check to see if /proc/mounts contains any writeable filesystems
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* backed by a block device.
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* Return true if none found, else return false.
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*/
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static int remount_ro_done(void)
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{
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FILE* fp;
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struct mntent* mentry;
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int found_rw_fs = 0;
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if ((fp = setmntent("/proc/mounts", "r")) == NULL) {
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/* If we can't read /proc/mounts, just give up. */
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return 1;
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}
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while ((mentry = getmntent(fp)) != NULL) {
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if (!strncmp(mentry->mnt_fsname, "/dev/block", 10) && strstr(mentry->mnt_opts, "rw,")) {
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found_rw_fs = 1;
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break;
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}
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}
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endmntent(fp);
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return !found_rw_fs;
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}
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/* Remounting filesystems read-only is difficult when there are files
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* opened for writing or pending deletes on the filesystem. There is
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* no way to force the remount with the mount(2) syscall. The magic sysrq
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* 'u' command does an emergency remount read-only on all writable filesystems
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* that have a block device (i.e. not tmpfs filesystems) by calling
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* emergency_remount(), which knows how to force the remount to read-only.
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* Unfortunately, that is asynchronous, and just schedules the work and
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* returns. The best way to determine if it is done is to read /proc/mounts
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* repeatedly until there are no more writable filesystems mounted on
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* block devices.
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*/
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static void remount_ro(void)
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{
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int fd, cnt = 0;
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/* Trigger the remount of the filesystems as read-only,
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* which also marks them clean.
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*/
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fd = open("/proc/sysrq-trigger", O_WRONLY);
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if (fd < 0) {
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return;
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}
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write(fd, "u", 1);
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close(fd);
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/* Now poll /proc/mounts till it's done */
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while (!remount_ro_done() && (cnt < 50)) {
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usleep(100000);
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cnt++;
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}
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return;
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}
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int android_reboot(int cmd, int flags UNUSED, char *arg)
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{
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int ret;
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sync();
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remount_ro();
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switch (cmd) {
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case ANDROID_RB_RESTART:
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ret = reboot(RB_AUTOBOOT);
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break;
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case ANDROID_RB_POWEROFF:
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ret = reboot(RB_POWER_OFF);
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break;
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case ANDROID_RB_RESTART2:
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ret = syscall(__NR_reboot, LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2,
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LINUX_REBOOT_CMD_RESTART2, arg);
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break;
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default:
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ret = -1;
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}
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return ret;
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}
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