昨天開會討論IP網絡升級時,需要一個後臺服務做升級檢測及下載數據,最後在定義下載的數據存放位置及如何做開機標志時,突然發現一個很好用的上層java類對象。
frameworks\base\core\java\android\os\RecoverySystem.java
那麼這個類做瞭什麼事情呢?又是如何做到的。
RecoverySystem類,可以幫助我們調用系統還原等操作:
android.os.RecoverySystem,提供瞭如下靜態方法
static void installPackage(Context context, File packageFile) //重啟設備,安裝一個更新包
static void rebootWipeUserData(Context context) //重啟設備,清除用戶數據分區類似恢復出廠設置
static String handleAftermath() 提供清除recover中相關文件,在開機廣播中被調用
static void verifyPackage(File packageFile, RecoverySystem.ProgressListener listener, File deviceCertsZipFile) //驗證加密簽名的系統更新包在安裝前,其中第二個數接口的具體定義為 android.os.RecoverySystem.ProgressListener 其中隻有一個回調方法 abstract void onProgress(int progress) 來顯示效驗的進度。
下面具體看一下代碼中是如何實現:
1、安裝更新包:
/** * Reboots the device in order to install the given update * package. * Requires the {@link android.Manifest.permission#REBOOT} permission. * * @param context the Context to use * @param packageFile the update package to install. Must be on * a partition mountable by recovery. (The set of partitions * known to recovery may vary from device to device. Generally, * /cache and /data are safe.) * * @throws IOException if writing the recovery command file * fails, or if the reboot itself fails. */ public static void installPackage(Context context, File packageFile) throws IOException { String filename = packageFile.getCanonicalPath(); Log.w(TAG, "!!! REBOOTING TO INSTALL " + filename + " !!!"); String arg = "--update_package=" + filename; bootCommand(context, arg); // 都是調用瞭這個函數 } /** * Reboot into the recovery system with the supplied argument. * @param arg to pass to the recovery utility. * @throws IOException if something goes wrong. */ private static void bootCommand(Context context, String arg) throws IOException { RECOVERY_DIR.mkdirs(); // In case we need it COMMAND_FILE.delete(); // In case it's not writable LOG_FILE.delete(); FileWriter command = new FileWriter(COMMAND_FILE); // 寫命令寫入到recover中 try { command.write(arg); command.write("\n"); } finally { command.close(); } // Having written the command file, go ahead and reboot 系統重啟 PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE); pm.reboot("recovery"); throw new IOException("Reboot failed (no permissions?)"); } /** * Reboots the device in order to install the given update * package. * Requires the {@link android.Manifest.permission#REBOOT} permission. * * @param context the Context to use * @param packageFile the update package to install. Must be on * a partition mountable by recovery. (The set of partitions * known to recovery may vary from device to device. Generally, * /cache and /data are safe.) * * @throws IOException if writing the recovery command file * fails, or if the reboot itself fails. */ public static void installPackage(Context context, File packageFile) throws IOException { String filename = packageFile.getCanonicalPath(); Log.w(TAG, "!!! REBOOTING TO INSTALL " + filename + " !!!"); String arg = "--update_package=" + filename; bootCommand(context, arg); // 都是調用瞭這個函數 } /** * Reboot into the recovery system with the supplied argument. * @param arg to pass to the recovery utility. * @throws IOException if something goes wrong. */ private static void bootCommand(Context context, String arg) throws IOException { RECOVERY_DIR.mkdirs(); // In case we need it COMMAND_FILE.delete(); // In case it's not writable LOG_FILE.delete(); FileWriter command = new FileWriter(COMMAND_FILE); // 寫命令寫入到recover中 try { command.write(arg); command.write("\n"); } finally { command.close(); } // Having written the command file, go ahead and reboot 系統重啟 PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE); pm.reboot("recovery"); throw new IOException("Reboot failed (no permissions?)"); }
2、出廠恢復
/** * Reboots the device and wipes the user data partition. This is * sometimes called a "factory reset", which is something of a * misnomer because the system partition is not restored to its * factory state. * Requires the {@link android.Manifest.permission#REBOOT} permission. * * @param context the Context to use * * @throws IOException if writing the recovery command file * fails, or if the reboot itself fails. */ public static void rebootWipeUserData(Context context) throws IOException { final ConditionVariable condition = new ConditionVariable(); Intent intent = new Intent("android.intent.action.MASTER_CLEAR_NOTIFICATION"); context.sendOrderedBroadcast(intent, 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(); bootCommand(context, "--wipe_data"); } /** * Reboot into the recovery system to wipe the /cache partition. * @throws IOException if something goes wrong. */ public static void rebootWipeCache(Context context) throws IOException { bootCommand(context, "--wipe_cache"); } /** * Reboots the device and wipes the user data partition. This is * sometimes called a "factory reset", which is something of a * misnomer because the system partition is not restored to its * factory state. * Requires the {@link android.Manifest.permission#REBOOT} permission. * * @param context the Context to use * * @throws IOException if writing the recovery command file * fails, or if the reboot itself fails. */ public static void rebootWipeUserData(Context context) throws IOException { final ConditionVariable condition = new ConditionVariable(); Intent intent = new Intent("android.intent.action.MASTER_CLEAR_NOTIFICATION"); context.sendOrderedBroadcast(intent, 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(); bootCommand(context, "--wipe_data"); } /** * Reboot into the recovery system to wipe the /cache partition. * @throws IOException if something goes wrong. */ public static void rebootWipeCache(Context context) throws IOException { bootCommand(context, "--wipe_cache"); }
3、驗證簽名
public static void verifyPackage(File packageFile,
ProgressListener listener,
File deviceCertsZipFile) 請自行閱讀源碼
後面說一下重啟 reboot 命令如何執行的:
無論是 factory reset 工廠恢復還是 安裝更新包都會調用到reboot函數,調用 pm.reboot("recovery");
通到jni就是: android_os_Power.cpp
shutdown 調用 android_reboot(ANDROID_RB_POWEROFF, 0, 0);
reboot 調用 android_reboot(ANDROID_RB_RESTART2, 0, (char *) chars);
最終都是調用到下面函數:
int reboot (int mode)
{
return __reboot( LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, mode, NULL );
}
=====linux kernel 內核流程=====
/bionic/libc/arch-arm/syscalls/__reboot.S
這個文件由gensyscalls.py自動產生,調用系統調用 __NR_reboot
bionic/libc/include/sys/linux-syscalls.h
#define __NR_reboot (__NR_SYSCALL_BASE+88)
/arch/arm/kernel/calls.S
__NR_reboot?就是系統函數sys_reboot
sys_reboot定義在./include/linux/syscalls.h,實現在./kernel/sys.c?sys_reboot會調用kernel_restart
最終kernel_restart調用每一個架構特定的machine_restart,即machine_restart執行每個架構特定的函數