Android源码笔记--恢复出厂设置

最近在学习Android系统源码，这一节主要是了解恢复出厂设置。实现恢复出厂一般是通过发广播操作，如下:

//恢复出厂设置
Intent recovery = new Intent("android.intent.action.MASTER_CLEAR");
recovery.setPackage("android");
sendBroadcast(recovery);清单文件需要加:1 android:shareUserId = "android.uid.system"  //表明系统应用2 <uses-permission android:name="android.permission.MASTER_CLEAR" />

它的主要流程如下：

1 点击按钮，系统发送恢复出厂设置广播
2 系统MasterClearReceiver接收广播，并进行android层的相关处理最后重启
3 在/cache/recovery/command文件中写入命令字段
4 重启系统，进入Recovery模式
5 根据/cache/recovery/command中的命令字段清楚用户数据
6 重新启动系统,恢复出厂完成

简单来看一下源码:

/frameworks/base/services/core/java/com/android/server/MasterClearReceiver.javapublic class MasterClearReceiver extends BroadcastReceiver {private static final String TAG = "MasterClear";private boolean mWipeExternalStorage;private boolean mWipeEsims;@Overridepublic void onReceive(final Context context, final Intent intent) {...final String factoryResetPackage = context.getString(com.android.internal.R.string.config_factoryResetPackage);if (Intent.ACTION_FACTORY_RESET.equals(intent.getAction())&& !TextUtils.isEmpty(factoryResetPackage)) {intent.setPackage(factoryResetPackage).setComponent(null);context.sendBroadcastAsUser(intent, UserHandle.SYSTEM);return;}final boolean shutdown = intent.getBooleanExtra("shutdown", false);final String reason = intent.getStringExtra(Intent.EXTRA_REASON);mWipeExternalStorage = intent.getBooleanExtra(Intent.EXTRA_WIPE_EXTERNAL_STORAGE, false);mWipeEsims = intent.getBooleanExtra(Intent.EXTRA_WIPE_ESIMS, false);final boolean forceWipe = intent.getBooleanExtra(Intent.EXTRA_FORCE_MASTER_CLEAR, false)|| intent.getBooleanExtra(Intent.EXTRA_FORCE_FACTORY_RESET, 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, forceWipe, mWipeEsims);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 (mWipeExternalStorage) {// thr will be started at the end of this task.new WipeDataTask(context, thr).execute();} else {thr.start();}}private class WipeDataTask extends AsyncTask<Void, Void, Void> {private final Thread mChainedTask;private final Context mContext;private final ProgressDialog mProgressDialog;public WipeDataTask(Context context, Thread chainedTask) {mContext = context;mChainedTask = chainedTask;mProgressDialog = new ProgressDialog(context);}@Overrideprotected void onPreExecute() {mProgressDialog.setIndeterminate(true);mProgressDialog.getWindow().setType(WindowManager.LayoutParams.TYPE_SYSTEM_ALERT);mProgressDialog.setMessage(mContext.getText(R.string.progress_erasing));mProgressDialog.show();}@Overrideprotected Void doInBackground(Void... params) {Slog.w(TAG, "Wiping adoptable disks");if (mWipeExternalStorage) {StorageManager sm = (StorageManager) mContext.getSystemService(Context.STORAGE_SERVICE);sm.wipeAdoptableDisks();}return null;}@Overrideprotected void onPostExecute(Void result) {mProgressDialog.dismiss();mChainedTask.start();}}
}

<receiver android:name="com.android.server.MasterClearReceiver"android:permission="android.permission.MASTER_CLEAR"><intent-filterandroid:priority="100" ><!-- For Checkin, Settings, etc.: action=FACTORY_RESET --><action android:name="android.intent.action.FACTORY_RESET" /><!-- As above until all the references to the deprecated MASTER_CLEAR get updated toFACTORY_RESET. --><action android:name="android.intent.action.MASTER_CLEAR" /><!-- MCS always uses REMOTE_INTENT: category=MASTER_CLEAR --><action android:name="com.google.android.c2dm.intent.RECEIVE" /><category android:name="android.intent.category.MASTER_CLEAR" /></intent-filter></receiver>

 /frameworks/base/core/java/android/os/RecoverySystem.javapublic class RecoverySystem {private final IRecoverySystem mService;public RecoverySystem(IRecoverySystem service) {mService = service;}public static void rebootWipeUserData(Context context, boolean shutdown, String reason,boolean force, boolean wipeEuicc) throws IOException {UserManager um = (UserManager) context.getSystemService(Context.USER_SERVICE);if (!force && 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| Intent.FLAG_RECEIVER_INCLUDE_BACKGROUND);context.sendOrderedBroadcastAsUser(intent, UserHandle.SYSTEM,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();EuiccManager euiccManager = context.getSystemService(EuiccManager.class);if (wipeEuicc) {wipeEuiccData(context, PACKAGE_NAME_EUICC_DATA_MANAGEMENT_CALLBACK);} else {removeEuiccInvisibleSubs(context, euiccManager);}String shutdownArg = null;if (shutdown) {shutdownArg = "--shutdown_after";}String reasonArg = null;if (!TextUtils.isEmpty(reason)) {String timeStamp = DateFormat.format("yyyy-MM-ddTHH:mm:ssZ", System.currentTimeMillis()).toString();reasonArg = "--reason=" + sanitizeArg(reason + "," + timeStamp);}final String localeArg = "--locale=" + Locale.getDefault().toLanguageTag() ;bootCommand(context, shutdownArg, "--wipe_data", reasonArg, localeArg);}

 private static void bootCommand(Context context, String... args) throws IOException {//删除日志信息 LOG_FILE.delete();StringBuilder command = new StringBuilder();for (String arg : args) {if (!TextUtils.isEmpty(arg)) {command.append(arg);command.append("\n");}}// Write the command into BCB (bootloader control block) and boot from// there. Will not return unless failed.// 将命令写到bootloader control block RecoverySystem rs = (RecoverySystem) context.getSystemService(Context.RECOVERY_SERVICE);rs.rebootRecoveryWithCommand(command.toString());throw new IOException("Reboot failed (no permissions?)");}// 通过Binder与RecoverySystemService对话以设置BCBprivate void rebootRecoveryWithCommand(String command) {try {mService.rebootRecoveryWithCommand(command);} catch (RemoteException ignored) {}}

来看一下服务端:

/frameworks/base/services/core/java/com/android/server/recoverysystem/RecoverySystemService.java@Override // Binder callpublic void rebootRecoveryWithCommand(String command) {if (DEBUG) Slog.d(TAG, "rebootRecoveryWithCommand: [" + command + "]");synchronized (sRequestLock) {if (!setupOrClearBcb(true, command)) {return;}// 设置完CBC，调用电源管理重启系统，进入恢复模式PowerManager pm = mInjector.getPowerManager();pm.reboot(PowerManager.REBOOT_RECOVERY);}}private boolean setupOrClearBcb(boolean isSetup, String command) {mContext.enforceCallingOrSelfPermission(android.Manifest.permission.RECOVERY, null);final boolean available = checkAndWaitForUncryptService();if (!available) {Slog.e(TAG, "uncrypt service is unavailable.");return false;}if (isSetup) {mInjector.systemPropertiesSet("ctl.start", "setup-bcb");} else {mInjector.systemPropertiesSet("ctl.start", "clear-bcb");}// Connect to the uncrypt service socket.UncryptSocket socket = mInjector.connectService();if (socket == null) {Slog.e(TAG, "Failed to connect to uncrypt socket");return false;}try {// Send the BCB commands if it's to setup BCB.if (isSetup) {socket.sendCommand(command);}// Read the status from the socket.int status = socket.getPercentageUncrypted();// Ack receipt of the status code. uncrypt waits for the ack so// the socket won't be destroyed before we receive the code.socket.sendAck();if (status == 100) {Slog.i(TAG, "uncrypt " + (isSetup ? "setup" : "clear")+ " bcb successfully finished.");} else {// Error in /system/bin/uncrypt.Slog.e(TAG, "uncrypt failed with status: " + status);return false;}} catch (IOException e) {Slog.e(TAG, "IOException when communicating with uncrypt:", e);return false;} finally {socket.close();}return true;}

/frameworks/base/core/java/android/os/PowerManager.java
public final class PowerManager {@UnsupportedAppUsagefinal IPowerManager mService;/*** {@hide}*/public PowerManager(Context context, IPowerManager service, IThermalService thermalService,Handler handler) {mContext = context;mService = service;mThermalService = thermalService;mHandler = handler;}public void reboot(@Nullable String reason) {if (REBOOT_USERSPACE.equals(reason) && !isRebootingUserspaceSupported()) {throw new UnsupportedOperationException("Attempted userspace reboot on a device that doesn't support it");}try {mService.reboot(false, reason, true);} catch (RemoteException e) {throw e.rethrowFromSystemServer();}}
}

/frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java/*** Reboots the device.** @param confirm If true, shows a reboot confirmation dialog.* @param reason The reason for the reboot, or null if none.* @param wait If true, this call waits for the reboot to complete and does not return.*/@Override // Binder callpublic void reboot(boolean confirm, @Nullable String reason, boolean wait) {mContext.enforceCallingOrSelfPermission(android.Manifest.permission.REBOOT, null);if (PowerManager.REBOOT_RECOVERY.equals(reason)|| PowerManager.REBOOT_RECOVERY_UPDATE.equals(reason)) {mContext.enforceCallingOrSelfPermission(android.Manifest.permission.RECOVERY, null);}final long ident = Binder.clearCallingIdentity();try {shutdownOrRebootInternal(HALT_MODE_REBOOT, confirm, reason, wait);} finally {Binder.restoreCallingIdentity(ident);}}private void shutdownOrRebootInternal(final @HaltMode int haltMode, final boolean confirm,@Nullable final String reason, boolean wait) {if (PowerManager.REBOOT_USERSPACE.equals(reason)) {if (!PowerManager.isRebootingUserspaceSupportedImpl()) {throw new UnsupportedOperationException("Attempted userspace reboot on a device that doesn't support it");}UserspaceRebootLogger.noteUserspaceRebootWasRequested();}if (mHandler == null || !mSystemReady) {if (RescueParty.isAttemptingFactoryReset()) {// If we're stuck in a really low-level reboot loop, and a// rescue party is trying to prompt the user for a factory data// reset, we must GET TO DA CHOPPA!PowerManagerService.lowLevelReboot(reason);} else {throw new IllegalStateException("Too early to call shutdown() or reboot()");}}Runnable runnable = new Runnable() {@Overridepublic void run() {synchronized (this) {if (haltMode == HALT_MODE_REBOOT_SAFE_MODE) {ShutdownThread.rebootSafeMode(getUiContext(), confirm);} else if (haltMode == HALT_MODE_REBOOT) {ShutdownThread.reboot(getUiContext(), reason, confirm);} else {ShutdownThread.shutdown(getUiContext(), reason, confirm);}}}};// ShutdownThread must run on a looper capable of displaying the UI.Message msg = Message.obtain(UiThread.getHandler(), runnable);msg.setAsynchronous(true);UiThread.getHandler().sendMessage(msg);// PowerManager.reboot() is documented not to return so just wait for the inevitable.if (wait) {synchronized (runnable) {while (true) {try {runnable.wait();} catch (InterruptedException e) {}}}}}

/frameworks/base/services/core/java/com/android/server/power/ShutdownThread.javaprivate static final ShutdownThread sInstance = new ShutdownThread();public static void rebootSafeMode(final Context context, boolean confirm) {UserManager um = (UserManager) context.getSystemService(Context.USER_SERVICE);if (um.hasUserRestriction(UserManager.DISALLOW_SAFE_BOOT)) {return;}mReboot = true;mRebootSafeMode = true;mRebootHasProgressBar = false;mReason = null;shutdownInner(context, confirm);}public static void reboot(final Context context, String reason, boolean confirm) {mReboot = true;mRebootSafeMode = false;mRebootHasProgressBar = false;mReason = reason;shutdownInner(context, confirm);}public static void shutdown(final Context context, String reason, boolean confirm) {mReboot = false;mRebootSafeMode = false;mReason = reason;shutdownInner(context, confirm);}private static void shutdownInner(final Context context, boolean confirm) {// ShutdownThread is called from many places, so best to verify here that the context passed// in is themed.context.assertRuntimeOverlayThemable();// ensure that only one thread is trying to power down.// any additional calls are just returnedsynchronized (sIsStartedGuard) {if (sIsStarted) {Log.d(TAG, "Request to shutdown already running, returning.");return;}}final int longPressBehavior = context.getResources().getInteger(com.android.internal.R.integer.config_longPressOnPowerBehavior);final int resourceId = mRebootSafeMode? com.android.internal.R.string.reboot_safemode_confirm: (longPressBehavior == 2? com.android.internal.R.string.shutdown_confirm_question: com.android.internal.R.string.shutdown_confirm);Log.d(TAG, "Notifying thread to start shutdown longPressBehavior=" + longPressBehavior);if (confirm) {final CloseDialogReceiver closer = new CloseDialogReceiver(context);if (sConfirmDialog != null) {sConfirmDialog.dismiss();}sConfirmDialog = new AlertDialog.Builder(context).setTitle(mRebootSafeMode? com.android.internal.R.string.reboot_safemode_title: com.android.internal.R.string.power_off).setMessage(resourceId).setPositiveButton(com.android.internal.R.string.yes, new DialogInterface.OnClickListener() {public void onClick(DialogInterface dialog, int which) {beginShutdownSequence(context);}}).setNegativeButton(com.android.internal.R.string.no, null).create();closer.dialog = sConfirmDialog;sConfirmDialog.setOnDismissListener(closer);sConfirmDialog.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD_DIALOG);sConfirmDialog.show();} else {beginShutdownSequence(context);}}

/frameworks/base/core/java/android/os/storage/StorageManager.javaprivate final IStorageManager mStorageManager;@UnsupportedAppUsagepublic StorageManager(Context context, Looper looper) throws ServiceNotFoundException {mContext = context;mResolver = context.getContentResolver();mLooper = looper;mStorageManager = IStorageManager.Stub.asInterface(ServiceManager.getServiceOrThrow("mount"));mAppOps = mContext.getSystemService(AppOpsManager.class);}/** {@hide} */public void wipeAdoptableDisks() {// We only wipe devices in "adoptable" locations, which are in a// long-term stable slot/location on the device, where apps have a// reasonable chance of storing sensitive data. (Apps need to go through// SAF to write to transient volumes.)final List<DiskInfo> disks = getDisks();for (DiskInfo disk : disks) {final String diskId = disk.getId();if (disk.isAdoptable()) {Slog.d(TAG, "Found adoptable " + diskId + "; wiping");try {// TODO: switch to explicit wipe command when we have it,// for now rely on the fact that vfat format does a wipemStorageManager.partitionPublic(diskId);} catch (Exception e) {Slog.w(TAG, "Failed to wipe " + diskId + ", but soldiering onward", e);}} else {Slog.d(TAG, "Ignorning non-adoptable disk " + disk.getId());}}}/** {@hide} */@UnsupportedAppUsagepublic void partitionPublic(String diskId) {try {mStorageManager.partitionPublic(diskId);} catch (RemoteException e) {throw e.rethrowFromSystemServer();}}

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