android之恢复出厂设置的关机流程

意外发现：setprop sys.powerctl reboot,recovery 将重启进入有菜单选择界面的recovery模式，在此模式下有root权限，不过要通过串口模式操作。

在系统设置应用里有恢复出厂设置的菜单，点击弹出对话框，确认后调用恢复出厂设置广播：

Settings/src/com/android/tv/settings/device/privacy/PrivacyActivity.java:171

    private void onFactoryResetConfirm(ActionBehavior behaviour) {switch (behaviour) {case INIT:setContentAndActionFragments(ContentFragment.newInstance(ActionType.FACTORY_RESET_CONFIRM.getTitle(getResources()),getString(R.string.device_reset),getString(R.string.confirm_factory_reset_description),R.drawable.ic_settings_backuprestore,getResources().getColor(R.color.icon_background)),ActionFragment.newInstance(getFactoryResetConfirmActions()));break;case OK:if (!ActivityManager.isUserAMonkey()) {Intent resetIntent = new Intent("android.intent.action.MASTER_CLEAR");if (getIntent().getBooleanExtra(SHUTDOWN_INTENT_EXTRA, false)) {resetIntent.putExtra(SHUTDOWN_INTENT_EXTRA, true);}sendBroadcast(resetIntent);}break;case CANCEL:getFragmentManager().popBackStack(null, 0);getFragmentManager().popBackStack(null, 0);break;default:break;}}

搜索字段MASTER_CLEAR，frameworks/base/core/res/AndroidManifest.xml里有注册receiver

frameworks\base\services\core\java\com\android\server\MasterClearReceiver.java

    public void onReceive(final Context context, final Intent intent) {if (intent.getAction().equals(Intent.ACTION_REMOTE_INTENT)) {if (!"google.com".equals(intent.getStringExtra("from"))) {Slog.w(TAG, "Ignoring master clear request -- not from trusted server.");return;}}final boolean shutdown = intent.getBooleanExtra("shutdown", false);final String reason = intent.getStringExtra(Intent.EXTRA_REASON);final boolean wipeExternalStorage = intent.getBooleanExtra(Intent.EXTRA_WIPE_EXTERNAL_STORAGE, false);Slog.w(TAG, "!!! FACTORY RESET !!!");// The reboot call is blocking, so we need to do it on another thread.Thread thr = new Thread("Reboot") {@Overridepublic void run() {try {RecoverySystem.rebootWipeUserData(context, shutdown, reason);Log.wtf(TAG, "Still running after master clear?!");} catch (IOException e) {Slog.e(TAG, "Can't perform master clear/factory reset", e);} catch (SecurityException e) {Slog.e(TAG, "Can't perform master clear/factory reset", e);}}};if (wipeExternalStorage) {// thr will be started at the end of this task.new WipeAdoptableDisksTask(context, thr).execute();} else {thr.start();}}

frameworks\base\core\java\android\os\RecoverySystem.java

    public static void rebootWipeUserData(Context context, boolean shutdown, String reason)throws IOException {UserManager um = (UserManager) context.getSystemService(Context.USER_SERVICE);if (um.hasUserRestriction(UserManager.DISALLOW_FACTORY_RESET)) {throw new SecurityException("Wiping data is not allowed for this user.");}final ConditionVariable condition = new ConditionVariable();Intent intent = new Intent("android.intent.action.MASTER_CLEAR_NOTIFICATION");intent.addFlags(Intent.FLAG_RECEIVER_FOREGROUND);context.sendOrderedBroadcastAsUser(intent, UserHandle.OWNER,android.Manifest.permission.MASTER_CLEAR,new BroadcastReceiver() {@Overridepublic void onReceive(Context context, Intent intent) {condition.open();}}, null, 0, null, null);// Block until the ordered broadcast has completed.condition.block();String shutdownArg = null;if (shutdown) {shutdownArg = "--shutdown_after";}String reasonArg = null;if (!TextUtils.isEmpty(reason)) {reasonArg = "--reason=" + sanitizeArg(reason);}final String localeArg = "--locale=" + Locale.getDefault().toString();bootCommand(context, shutdownArg, "--wipe_data", reasonArg, localeArg);}

    private static void bootCommand(Context context, String... args) throws IOException {RECOVERY_DIR.mkdirs();  // In case we need itCOMMAND_FILE.delete();  // In case it's not writableLOG_FILE.delete();FileWriter command = new FileWriter(COMMAND_FILE);try {for (String arg : args) {if (!TextUtils.isEmpty(arg)) {// MStar Android Patch BeginStorageManager mStorageManager = context.getSystemService(StorageManager.class);String cmd = arg;String label = null;String uuid = null;if (cmd.startsWith("--update_package")) {cmd = arg.substring(17, arg.length() -1);if (cmd.startsWith("/cache")) {command.write("--uuid=mstar-cache");command.write("\n");command.write("--label=mstar-cache");command.write("\n");} else {StorageVolume vol = mStorageManager.getStorageVolume(new File(cmd));uuid = "--uuid=" + vol.getUuid();label = "--label=" + utf8ToUnicode(vol.getFsLabel());command.write(uuid);command.write("\n");command.write(label);command.write("\n");}}// MStar Android Patch Endcommand.write(arg);command.write("\n");}}} finally {command.close();}Log.i(TAG, "bootCommand /cache");// Having written the command file, go ahead and rebootPowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE);pm.reboot(PowerManager.REBOOT_RECOVERY);throw new IOException("Reboot failed (no permissions?)");}

此时会在安卓设备里/cache/recovery 目录清除，且创建command文件，写入命令：

#/cache/recovery # ls -l
-rw------- system system 55 2018-01-01 08:01 command

#cat command
--wipe_data
--reason=MasterClearConfirm
--locale=zh_CN

然后重启,重启还需处理，否则不会进入recovery。ShutdownThread.java：

 private static void beginShutdownSequence(Context context) {synchronized (sIsStartedGuard) {if (sIsStarted) {Log.d(TAG, "Shutdown sequence already running, returning.");return;}sIsStarted = true;}// Throw up a system dialog to indicate the device is rebooting / shutting down.ProgressDialog pd = new ProgressDialog(context);// Path 1: Reboot to recovery and install the update//   Condition: mRebootReason == REBOOT_RECOVERY and mRebootUpdate == True//   (mRebootUpdate is set by checking if /cache/recovery/uncrypt_file exists.)//   UI: progress bar//// Path 2: Reboot to recovery for factory reset//   Condition: mRebootReason == REBOOT_RECOVERY//   UI: spinning circle only (no progress bar)//// Path 3: Regular reboot / shutdown//   Condition: Otherwise//   UI: spinning circle only (no progress bar)if (PowerManager.REBOOT_RECOVERY.equals(mRebootReason)) {mRebootUpdate = new File(UNCRYPT_PACKAGE_FILE).exists();if (mRebootUpdate) {pd.setTitle(context.getText(com.android.internal.R.string.reboot_to_update_title));pd.setMessage(context.getText(com.android.internal.R.string.reboot_to_update_prepare));pd.setMax(100);pd.setProgressNumberFormat(null);pd.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);pd.setProgress(0);pd.setIndeterminate(false);} else {// Factory reset path. Set the dialog message accordingly.pd.setTitle(context.getText(com.android.internal.R.string.reboot_to_reset_title));pd.setMessage(context.getText(com.android.internal.R.string.reboot_to_reset_message));pd.setIndeterminate(true);}} else {
.
.
.
.// also make sure the screen stays on for better user experiencesInstance.mScreenWakeLock = null;if (sInstance.mPowerManager.isScreenOn()) {try {sInstance.mScreenWakeLock = sInstance.mPowerManager.newWakeLock(PowerManager.FULL_WAKE_LOCK, TAG + "-screen");sInstance.mScreenWakeLock.setReferenceCounted(false);sInstance.mScreenWakeLock.acquire();} catch (SecurityException e) {Log.w(TAG, "No permission to acquire wake lock", e);sInstance.mScreenWakeLock = null;}}// start the thread that initiates shutdownsInstance.mHandler = new Handler() {};sInstance.start();}

调到最后一行，sInstance.start(); 启动线程的运行，进入线程的run方法。

    /*** Makes sure we handle the shutdown gracefully.* Shuts off power regardless of radio and bluetooth state if the alloted time has passed.*/public void run() {BroadcastReceiver br = new BroadcastReceiver() {@Override public void onReceive(Context context, Intent intent) {// We don't allow apps to cancel this, so ignore the result.actionDone();}};/** Write a system property in case the system_server reboots before we* get to the actual hardware restart. If that happens, we'll retry at* the beginning of the SystemServer startup.*/{String reason = (mReboot ? "1" : "0") + (mRebootReason != null ? mRebootReason : "");SystemProperties.set(SHUTDOWN_ACTION_PROPERTY, reason);}/** If we are rebooting into safe mode, write a system property* indicating so.*/if (mRebootSafeMode) {SystemProperties.set(REBOOT_SAFEMODE_PROPERTY, "1");}Log.i(TAG, "Sending shutdown broadcast...");// First send the high-level shut down broadcast.mActionDone = false;Intent intent = new Intent(Intent.ACTION_SHUTDOWN);intent.addFlags(Intent.FLAG_RECEIVER_FOREGROUND);mContext.sendOrderedBroadcastAsUser(intent,UserHandle.ALL, null, br, mHandler, 0, null, null);final long endTime = SystemClock.elapsedRealtime() + MAX_BROADCAST_TIME;synchronized (mActionDoneSync) {while (!mActionDone) {long delay = endTime - SystemClock.elapsedRealtime();if (delay <= 0) {Log.w(TAG, "Shutdown broadcast timed out");break;} else if (mRebootUpdate) {int status = (int)((MAX_BROADCAST_TIME - delay) * 1.0 *BROADCAST_STOP_PERCENT / MAX_BROADCAST_TIME);sInstance.setRebootProgress(status, null);}try {mActionDoneSync.wait(Math.min(delay, PHONE_STATE_POLL_SLEEP_MSEC));} catch (InterruptedException e) {}}}if (mRebootUpdate) {sInstance.setRebootProgress(BROADCAST_STOP_PERCENT, null);}Log.i(TAG, "Shutting down activity manager...");final IActivityManager am =ActivityManagerNative.asInterface(ServiceManager.checkService("activity"));if (am != null) {try {am.shutdown(MAX_BROADCAST_TIME);} catch (RemoteException e) {}}if (mRebootUpdate) {sInstance.setRebootProgress(ACTIVITY_MANAGER_STOP_PERCENT, null);}Log.i(TAG, "Shutting down package manager...");final PackageManagerService pm = (PackageManagerService)ServiceManager.getService("package");if (pm != null) {pm.shutdown();}if (mRebootUpdate) {sInstance.setRebootProgress(PACKAGE_MANAGER_STOP_PERCENT, null);}// Shutdown radios.shutdownRadios(MAX_RADIO_WAIT_TIME);if (mRebootUpdate) {sInstance.setRebootProgress(RADIO_STOP_PERCENT, null);}// Shutdown MountService to ensure media is in a safe stateIMountShutdownObserver observer = new IMountShutdownObserver.Stub() {public void onShutDownComplete(int statusCode) throws RemoteException {Log.w(TAG, "Result code " + statusCode + " from MountService.shutdown");actionDone();}};Log.i(TAG, "Shutting down MountService");// Set initial variables and time out time.mActionDone = false;final long endShutTime = SystemClock.elapsedRealtime() + MAX_SHUTDOWN_WAIT_TIME;synchronized (mActionDoneSync) {try {final IMountService mount = IMountService.Stub.asInterface(ServiceManager.checkService("mount"));if (mount != null) {mount.shutdown(observer);} else {Log.w(TAG, "MountService unavailable for shutdown");}} catch (Exception e) {Log.e(TAG, "Exception during MountService shutdown", e);}while (!mActionDone) {long delay = endShutTime - SystemClock.elapsedRealtime();if (delay <= 0) {Log.w(TAG, "Shutdown wait timed out");break;} else if (mRebootUpdate) {int status = (int)((MAX_SHUTDOWN_WAIT_TIME - delay) * 1.0 *(MOUNT_SERVICE_STOP_PERCENT - RADIO_STOP_PERCENT) /MAX_SHUTDOWN_WAIT_TIME);status += RADIO_STOP_PERCENT;sInstance.setRebootProgress(status, null);}try {mActionDoneSync.wait(Math.min(delay, PHONE_STATE_POLL_SLEEP_MSEC));} catch (InterruptedException e) {}}}if (mRebootUpdate) {sInstance.setRebootProgress(MOUNT_SERVICE_STOP_PERCENT, null);// If it's to reboot to install update, invoke uncrypt via init service.uncrypt();}rebootOrShutdown(mContext, mReboot, mRebootReason);}

rebootOrShutdown(mContext, mReboot, mRebootReason);

    public static void rebootOrShutdown(final Context context, boolean reboot, String reason) {if (reboot) {Log.i(TAG, "Rebooting, reason: " + reason);PowerManagerService.lowLevelReboot(reason);Log.e(TAG, "Reboot failed, will attempt shutdown instead");} else if (SHUTDOWN_VIBRATE_MS > 0 && context != null) {// vibrate before shutting downVibrator vibrator = new SystemVibrator(context);try {vibrator.vibrate(SHUTDOWN_VIBRATE_MS, VIBRATION_ATTRIBUTES);} catch (Exception e) {// Failure to vibrate shouldn't interrupt shutdown.  Just log it.Log.w(TAG, "Failed to vibrate during shutdown.", e);}// vibrator is asynchronous so we need to wait to avoid shutting down too soon.try {Thread.sleep(SHUTDOWN_VIBRATE_MS);} catch (InterruptedException unused) {}}// Shutdown powerLog.i(TAG, "Performing low-level shutdown...");PowerManagerService.lowLevelShutdown();}

PowerManagerService.lowLevelReboot(reason);

    /*** Low-level function to reboot the device. On success, this* function doesn't return. If more than 20 seconds passes from* the time a reboot is requested, this method returns.** @param reason code to pass to the kernel (e.g. "recovery"), or null.*/public static void lowLevelReboot(String reason) {if (reason == null) {reason = "";}if (reason.equals(PowerManager.REBOOT_RECOVERY)) {// If we are rebooting to go into recovery, instead of// setting sys.powerctl directly we'll start the// pre-recovery service which will do some preparation for// recovery and then reboot for us.SystemProperties.set("ctl.start", "pre-recovery");} else {SystemProperties.set("sys.powerctl", "reboot," + reason);}try {Thread.sleep(20 * 1000L);} catch (InterruptedException e) {Thread.currentThread().interrupt();}Slog.wtf(TAG, "Unexpected return from lowLevelReboot!");}

SystemProperties.set("ctl.start", "pre-recovery"); 此处将导致系统重启，启动init.rc里注册的服务：

service pre-recovery /system/bin/uncrypt --reboot
class main
disabled
oneshot

service pre-recovery /system/bin/uncrypt --reboot    system/bin/uncrypt 这个程序会被执行，传入的参数是--reboot

进入bootable/recovery/uncrypt/uncrypt.cpp

int main(int argc, char** argv) {const char* input_path;const char* map_file;if (argc != 3 && argc != 1 && (argc == 2 && strcmp(argv[1], "--reboot") != 0)) {fprintf(stderr, "usage: %s [--reboot] [<transform_path> <map_file>]\n", argv[0]);return 2;}// When uncrypt is started with "--reboot", it wipes misc and reboots.// Otherwise it uncrypts the package and writes the block map.if (argc == 2) {printf("\r\n uncrypt to wipe_misc");if (read_fstab() == NULL) {return 1;}wipe_misc();reboot_to_recovery();} else {// The pipe has been created by the system server.int status_fd = open(status_file.c_str(), O_WRONLY | O_CREAT | O_SYNC, S_IRUSR | S_IWUSR);if (status_fd == -1) {ALOGE("failed to open pipe \"%s\": %s\n", status_file.c_str(), strerror(errno));return 1;}if (argc == 3) {// when command-line args are given this binary is being used// for debugging.input_path = argv[1];map_file = argv[2];} else {std::string package;if (!find_uncrypt_package(package)) {android::base::WriteStringToFd("-1\n", status_fd);close(status_fd);return 1;}input_path = package.c_str();map_file = cache_block_map.c_str();}int status = uncrypt(input_path, map_file, status_fd);if (status != 0) {android::base::WriteStringToFd("-1\n", status_fd);close(status_fd);return 1;}android::base::WriteStringToFd("100\n", status_fd);close(status_fd);}return 0;
}

static void reboot_to_recovery() {ALOGI("rebooting to recovery");property_set("sys.powerctl", "reboot,recovery");sleep(10);ALOGE("reboot didn't succeed?");
}

property_set("sys.powerctl", "reboot,recovery");

sys.powerctl属性出发开关在init.rc中

on property:sys.powerctl=*
powerctl ${sys.powerctl}

system/core/init/keywords.h
KEYWORD(powerctl,    COMMAND, 1, do_powerctl

system/core/init/builtins.cpp
int do_powerctl(int nargs, char **args)
{char command[PROP_VALUE_MAX];int res;int len = 0;int cmd = 0;const char *reboot_target;res = expand_props(command, args[1], sizeof(command));if (res) {ERROR("powerctl: cannot expand '%s'\n", args[1]);return -EINVAL;}if (strncmp(command, "shutdown", 8) == 0) {cmd = ANDROID_RB_POWEROFF;len = 8;} else if (strncmp(command, "reboot", 6) == 0) {cmd = ANDROID_RB_RESTART2;len = 6;} else {ERROR("powerctl: unrecognized command '%s'\n", command);return -EINVAL;}if (command[len] == ',') {reboot_target = &command[len + 1];} else if (command[len] == '\0') {reboot_target = "";} else {ERROR("powerctl: unrecognized reboot target '%s'\n", &command[len]);return -EINVAL;}return android_reboot(cmd, 0, reboot_target);
}

android_reboot(cmd, 0, reboot_target);    参数为(ANDROID_RB_RESTART2, 0, "recovery")

system/core/libcutils/android_reboot.c
int android_reboot(int cmd, int flags UNUSED, const char *arg)
{int ret;sync();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 = syscall(__NR_reboot, LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2,LINUX_REBOOT_CMD_RESTART2, arg);break;default:ret = -1;}return ret;
}

case ANDROID_RB_RESTART2:
ret = syscall(__NR_reboot, LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2,
LINUX_REBOOT_CMD_RESTART2, arg);

在用户空间和内核空间之间，有一个叫做Syscall(系统调用, system call)的中间层，是连接用户态和内核态的桥梁。这样即提高了内核的安全型，也便于移植，只需实现同一套接口即可。Linux系统，用户空间通过向内核空间发出Syscall，产生软中断，从而让程序陷入内核态，执行相应的操作。对于每个系统调用都会有一个对应的系统调用号，比很多操作系统要少很多。

kernel/include/uapi/asm-generic/unistd.h
/* kernel/sys.c */
#define __NR_setpriority 140
__SYSCALL(__NR_setpriority, sys_setpriority)
#define __NR_getpriority 141
__SYSCALL(__NR_getpriority, sys_getpriority)
#define __NR_reboot 142
__SYSCALL(__NR_reboot, sys_reboot)
#define __NR_setregid 143

/* kernel/sys.c */表明是在/* kernel/sys.c */的文件里定义的方法

宏定义SYSCALL_DEFINEx(xxx,…)，展开后对应的方法则是sys_xxx；

kernel/sys.c
/** Reboot system call: for obvious reasons only root may call it,* and even root needs to set up some magic numbers in the registers* so that some mistake won't make this reboot the whole machine.* You can also set the meaning of the ctrl-alt-del-key here.** reboot doesn't sync: do that yourself before calling this.*/
SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,void __user *, arg)
{struct pid_namespace *pid_ns = task_active_pid_ns(current);char buffer[256];int ret = 0;/* We only trust the superuser with rebooting the system. */if (!ns_capable(pid_ns->user_ns, CAP_SYS_BOOT))return -EPERM;/* For safety, we require "magic" arguments. */if (magic1 != LINUX_REBOOT_MAGIC1 ||(magic2 != LINUX_REBOOT_MAGIC2 &&magic2 != LINUX_REBOOT_MAGIC2A &&magic2 != LINUX_REBOOT_MAGIC2B &&magic2 != LINUX_REBOOT_MAGIC2C))return -EINVAL;/** If pid namespaces are enabled and the current task is in a child* pid_namespace, the command is handled by reboot_pid_ns() which will* call do_exit().*/ret = reboot_pid_ns(pid_ns, cmd);if (ret)return ret;/* Instead of trying to make the power_off code look like* halt when pm_power_off is not set do it the easy way.*/
#if (MP_PLATFORM_PM == 0)if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)cmd = LINUX_REBOOT_CMD_HALT;#endif /* MP_PLATFORM_PM */mutex_lock(&reboot_mutex);switch (cmd) {case LINUX_REBOOT_CMD_RESTART:kernel_restart(NULL);break;case LINUX_REBOOT_CMD_CAD_ON:C_A_D = 1;break;case LINUX_REBOOT_CMD_CAD_OFF:C_A_D = 0;break;case LINUX_REBOOT_CMD_HALT:kernel_halt();do_exit(0);panic("cannot halt");case LINUX_REBOOT_CMD_POWER_OFF:kernel_power_off();do_exit(0);break;case LINUX_REBOOT_CMD_RESTART2:if (strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1) < 0) {ret = -EFAULT;break;}buffer[sizeof(buffer) - 1] = '\0';kernel_restart(buffer);break;#ifdef CONFIG_KEXECcase LINUX_REBOOT_CMD_KEXEC:ret = kernel_kexec();break;
#endif#ifdef CONFIG_HIBERNATIONcase LINUX_REBOOT_CMD_SW_SUSPEND:ret = hibernate();break;
#endifdefault:ret = -EINVAL;break;}mutex_unlock(&reboot_mutex);return ret;
}

kernel_restart(buffer); 参数为("recovery")

/*** kernel_restart - reboot the system* @cmd: pointer to buffer containing command to execute for restart*     or %NULL**  Shutdown everything and perform a clean reboot.*    This is not safe to call in interrupt context.*/
void kernel_restart(char *cmd)
{extern ptrdiff_t   mstar_pm_base;kernel_restart_prepare(cmd);migrate_to_reboot_cpu();syscore_shutdown();if (!cmd)printk(KERN_EMERG "Restarting system.\n");elseprintk(KERN_EMERG "Restarting system with command '%s'.\n", cmd);#if defined(CONFIG_ARM)*((volatile unsigned int*) (0xfd000000 + (0x3008 << 1))) = 0x0e00;*((volatile unsigned int*) (0xfd000000 + (0x300a << 1))) = 0x0727;#elif defined(CONFIG_ARM64)*((volatile unsigned int*) (mstar_pm_base + (0x3008 << 1))) = 0x0e00;*((volatile unsigned int*) (mstar_pm_base + (0x300a << 1))) = 0x0727;#endifkmsg_dump(KMSG_DUMP_RESTART);machine_restart(cmd);
}

machine_restart(cmd); 参数为("recovery")，machine_restart 函数在很多文件里都有，具体是哪个文件暂不研究，猜测可能走下面这条路，不过也有可能搞错了。

arch/arm64/kernel/process.c
void machine_restart(char *cmd)
{machine_shutdown();/* Disable interrupts first */local_irq_disable();local_fiq_disable();/* Now call the architecture specific reboot code. */if (arm_pm_restart)arm_pm_restart('h', cmd);/** Whoops - the architecture was unable to reboot.*/printk("Reboot failed -- System halted\n");while (1);
}

arm_pm_restart('h', cmd); cmd="recovery"

arch/arm64/kernel/process.c
void (*arm_pm_restart)(char str, const char *cmd) = arm_machine_restart;
EXPORT_SYMBOL_GPL(arm_pm_restart);

arch/arm64/kernel/process.c
#if (MP_PLATFORM_PM == 1)
static void arm_machine_restart(char mode, const char *cmd)
{/** Tell the mm system that we are going to reboot -* we may need it to insert some 1:1 mappings so that* soft boot works.*/setup_mm_for_reboot();#ifndef CONFIG_MP_PLATFORM_ARM/* Clean and invalidate caches */flush_cache_all();/* Turn D-cache off */cpu_cache_off();/* Push out any further dirty data, and ensure cache is empty */flush_cache_all();
#endif/** Now call the architecture specific reboot code.*/arch_reset(mode, cmd);
}
#else
static void arm_machine_restart(char mode, const char *cmd){}
#endif

kernel\linaro\mstar2\hal\mainz\cpu\arm64\include\mach\system.h
static inline void arch_reset(char mode, const char *cmd)
{
#ifdef CONFIG_SMPif(magic_number_address != 0)*(volatile unsigned short *)(magic_number_address) =  0x0;*(volatile unsigned long*)(REG_PM_MISC_BASE + 0xB8) = 0x79;    // reg_top_sw_rst
#endif
#if 0
// set WDT count down timer
*(volatile unsigned long*)(REG_WDT_BASE + 0x10) = BOOT_DELAY_MILLISECOND & 0x0000FFFF;
*(volatile unsigned long*)(REG_WDT_BASE + 0x14) = BOOT_DELAY_MILLISECOND  >> 16  ;
#endif
}

arch_reset(mode, cmd); 参数为（'h'，"recovery"）

#define REG_PM_MISC_BASE (0x2e00UL)

0x2eB8 写 0x79

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