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/*
* 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 <errno.h>
#include <fcntl.h>
#include <mntent.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/cdefs.h>
#include <sys/mount.h>
#include <sys/reboot.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <unistd.h>
#include <cutils/android_reboot.h>
#include <cutils/klog.h>
#include <cutils/list.h>
#define TAG "android_reboot"
#define READONLY_CHECK_MS 5000
#define READONLY_CHECK_TIMES 50
typedef struct {
struct listnode list;
struct mntent entry;
} mntent_list;
static bool has_mount_option(const char* opts, const char* opt_to_find)
{
bool ret = false;
char* copy = NULL;
char* opt;
char* rem;
while ((opt = strtok_r(copy ? NULL : (copy = strdup(opts)), ",", &rem))) {
if (!strcmp(opt, opt_to_find)) {
ret = true;
break;
}
}
free(copy);
return ret;
}
static bool is_block_device(const char* fsname)
{
return !strncmp(fsname, "/dev/block", 10);
}
/* Find all read+write block devices in /proc/mounts and add them to
* |rw_entries|.
*/
static void find_rw(struct listnode* rw_entries)
{
FILE* fp;
struct mntent* mentry;
if ((fp = setmntent("/proc/mounts", "r")) == NULL) {
KLOG_WARNING(TAG, "Failed to open /proc/mounts.\n");
return;
}
while ((mentry = getmntent(fp)) != NULL) {
if (is_block_device(mentry->mnt_fsname) &&
has_mount_option(mentry->mnt_opts, "rw")) {
mntent_list* item = (mntent_list*)calloc(1, sizeof(mntent_list));
item->entry = *mentry;
item->entry.mnt_fsname = strdup(mentry->mnt_fsname);
item->entry.mnt_dir = strdup(mentry->mnt_dir);
item->entry.mnt_type = strdup(mentry->mnt_type);
item->entry.mnt_opts = strdup(mentry->mnt_opts);
list_add_tail(rw_entries, &item->list);
}
}
endmntent(fp);
}
static void free_entries(struct listnode* entries)
{
struct listnode* node;
struct listnode* n;
list_for_each_safe(node, n, entries) {
mntent_list* item = node_to_item(node, mntent_list, list);
free(item->entry.mnt_fsname);
free(item->entry.mnt_dir);
free(item->entry.mnt_type);
free(item->entry.mnt_opts);
free(item);
}
}
static mntent_list* find_item(struct listnode* rw_entries, const char* fsname_to_find)
{
struct listnode* node;
list_for_each(node, rw_entries) {
mntent_list* item = node_to_item(node, mntent_list, list);
if (!strcmp(item->entry.mnt_fsname, fsname_to_find)) {
return item;
}
}
return NULL;
}
/* 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 (*cb_on_remount)(const struct mntent*))
{
int fd, cnt;
FILE* fp;
struct mntent* mentry;
struct listnode* node;
list_declare(rw_entries);
list_declare(ro_entries);
sync();
find_rw(&rw_entries);
/* Trigger the remount of the filesystems as read-only,
* which also marks them clean.
*/
fd = TEMP_FAILURE_RETRY(open("/proc/sysrq-trigger", O_WRONLY));
if (fd < 0) {
KLOG_WARNING(TAG, "Failed to open sysrq-trigger.\n");
/* TODO: Try to remount each rw parition manually in readonly mode.
* This may succeed if no process is using the partition.
*/
goto out;
}
if (TEMP_FAILURE_RETRY(write(fd, "u", 1)) != 1) {
close(fd);
KLOG_WARNING(TAG, "Failed to write to sysrq-trigger.\n");
/* TODO: The same. Manually remount the paritions. */
goto out;
}
close(fd);
/* Now poll /proc/mounts till it's done */
cnt = 0;
while (cnt < READONLY_CHECK_TIMES) {
if ((fp = setmntent("/proc/mounts", "r")) == NULL) {
/* If we can't read /proc/mounts, just give up. */
KLOG_WARNING(TAG, "Failed to open /proc/mounts.\n");
goto out;
}
while ((mentry = getmntent(fp)) != NULL) {
if (!is_block_device(mentry->mnt_fsname) ||
!has_mount_option(mentry->mnt_opts, "ro")) {
continue;
}
mntent_list* item = find_item(&rw_entries, mentry->mnt_fsname);
if (item) {
/* |item| has now been ro remounted. */
list_remove(&item->list);
list_add_tail(&ro_entries, &item->list);
}
}
endmntent(fp);
if (list_empty(&rw_entries)) {
/* All rw block devices are now readonly. */
break;
}
TEMP_FAILURE_RETRY(
usleep(READONLY_CHECK_MS * 1000 / READONLY_CHECK_TIMES));
cnt++;
}
list_for_each(node, &rw_entries) {
mntent_list* item = node_to_item(node, mntent_list, list);
KLOG_WARNING(TAG, "Failed to remount %s in readonly mode.\n",
item->entry.mnt_fsname);
}
if (cb_on_remount) {
list_for_each(node, &ro_entries) {
mntent_list* item = node_to_item(node, mntent_list, list);
cb_on_remount(&item->entry);
}
}
out:
free_entries(&rw_entries);
free_entries(&ro_entries);
}
int android_reboot_with_callback(
int cmd, int flags __unused, const char *arg,
void (*cb_on_remount)(const struct mntent*))
{
int ret;
remount_ro(cb_on_remount);
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 = syscall(__NR_reboot, LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2,
LINUX_REBOOT_CMD_RESTART2, arg);
break;
default:
ret = -1;
}
return ret;
}
int android_reboot(int cmd, int flags, const char *arg)
{
return android_reboot_with_callback(cmd, flags, arg, NULL);
}
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