ca8e66a8b0
Move the responsibility for rebooting the system from the reboot command to init. Init is in a better position to take actions to bring the system down cleanly, including making sure filesystems are mounted read-only. The only UIDs which can perform an init triggered reboot are root, system, and shell. Modify the reboot command so that it calls into init to perform the reboot. The reboot command no longer requires CAP_SYS_BOOT. Remove the -n reboot option and code which supports it. Anyone needing to do an unclean shutdown can just do a 'echo c > /proc/sysrq-trigger'. Modify adb so that it calls into init to perform a shutdown. Bug: 8646621 Change-Id: I84c0513acb549720cb0e8c9fcbda0050f5c396f5
131 lines
3.4 KiB
C
131 lines
3.4 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/types.h>
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#include <sys/stat.h>
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#include <fcntl.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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/* 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 *f;
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char mount_dev[256];
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char mount_dir[256];
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char mount_type[256];
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char mount_opts[256];
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int mount_freq;
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int mount_passno;
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int match;
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int found_rw_fs = 0;
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f = fopen("/proc/mounts", "r");
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if (! f) {
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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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do {
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match = fscanf(f, "%255s %255s %255s %255s %d %d\n",
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mount_dev, mount_dir, mount_type,
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mount_opts, &mount_freq, &mount_passno);
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mount_dev[255] = 0;
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mount_dir[255] = 0;
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mount_type[255] = 0;
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mount_opts[255] = 0;
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if ((match == 6) && !strncmp(mount_dev, "/dev/block", 10) && strstr(mount_opts, "rw")) {
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found_rw_fs = 1;
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break;
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}
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} while (match != EOF);
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fclose(f);
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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, 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 = __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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