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 "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.java
 
public class MasterClearReceiver extends BroadcastReceiver {
    private static final String TAG = "MasterClear";
    private boolean mWipeExternalStorage;
    private boolean mWipeEsims;
 
    @Override
    public 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") {
            @Override
            public 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 {
        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);
        }
 
        @Override
        protected void onPreExecute() {
            mProgressDialog.setIndeterminate(true);
            mProgressDialog.getWindow().setType(WindowManager.LayoutParams.TYPE_SYSTEM_ALERT);
            mProgressDialog.setMessage(mContext.getText(R.string.progress_erasing));
            mProgressDialog.show();
        }
 
        @Override
        protected Void doInBackground(Void... params) {
            Slog.w(TAG, "Wiping adoptable disks");
            if (mWipeExternalStorage) {
                StorageManager sm = (StorageManager) mContext.getSystemService(
                        Context.STORAGE_SERVICE);
                sm.wipeAdoptableDisks();
            }
            return null;
        }
 
        @Override
        protected void onPostExecute(Void result) {
            mProgressDialog.dismiss();
            mChainedTask.start();
        }
    }
}

"com.android.server.MasterClearReceiver"
            android:permission="android.permission.MASTER_CLEAR">
            
                    android:priority="100" >
                
                "android.intent.action.FACTORY_RESET" />
                
                "android.intent.action.MASTER_CLEAR" />
 
                
                "com.google.android.c2dm.intent.RECEIVE" />
                "android.intent.category.MASTER_CLEAR" />
            
 

 /frameworks/base/core/java/android/os/RecoverySystem.java
 
 
public 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() {
                    @Override
                    public 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BCB
    private 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 call
    public 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 {
 
  @UnsupportedAppUsage
    final 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 call
        public 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() {
            @Override
            public 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.java
	
	
	private 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 returned
        synchronized (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.java
 
 private final IStorageManager mStorageManager;
 
  @UnsupportedAppUsage
    public 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 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 wipe
                    mStorageManager.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} */
    @UnsupportedAppUsage
    public void partitionPublic(String diskId) {
        try {
            mStorageManager.partitionPublic(diskId);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }