http://blog.csdn.net/andyhuabing/article/details/9223163
昨天开会讨论IP网络升级时,需要一个后台服务做升级检测及下载数据,最后在定义下载的数据存放位置及如何做开机标志时,突然发现一个很好用的上层java类对象。
frameworks\base\core\java\android\os\RecoverySystem.java
那么这个类做了什么事情呢?又是如何做到的。
RecoverySystem类,可以帮助我们调用系统还原等操作:
android.os.RecoverySystem,提供了如下静态方法
static void installPackage(Context context, File packageFile) //重启设备,安装一个更新包
static void rebootWipeUserData(Context context) //重启设备,清除用户数据分区类似恢复出厂设置
static String handleAftermath() 提供清除recover中相关文件,在开机广播中被调用
static void verifyPackage(File packageFile, RecoverySystem.ProgressListener listener, File deviceCertsZipFile) //验证加密签名的系统更新包在安装前,其中第二个数接口的具体定义为 android.os.RecoverySystem.ProgressListener 其中只有一个回调方法 abstract void onProgress(int progress) 来显示效验的进度。
下面具体看一下代码中是如何实现:
1、安装更新包:
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/**
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* Reboots the device in order to install the given update
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* package.
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* Requires the {@link android.Manifest.permission#REBOOT} permission.
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*
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* @param context the Context to use
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* @param packageFile the update package to install. Must be on
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* a partition mountable by recovery. (The set of partitions
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* known to recovery may vary from device to device. Generally,
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* /cache and /data are safe.)
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*
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* @throws IOException if writing the recovery command file
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* fails, or if the reboot itself fails.
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*/
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public static void installPackage(Context context, File packageFile)
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throws IOException {
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String filename = packageFile.getCanonicalPath();
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Log.w(TAG, "!!! REBOOTING TO INSTALL " + filename + " !!!");
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String arg = "--update_package=" + filename;
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bootCommand(context, arg); // 都是调用了这个函数
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}
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/**
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* Reboot into the recovery system with the supplied argument.
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* @param arg to pass to the recovery utility.
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* @throws IOException if something goes wrong.
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*/
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private static void bootCommand(Context context, String arg) throws IOException {
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RECOVERY_DIR.mkdirs(); // In case we need it
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COMMAND_FILE.delete(); // In case it's not writable
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LOG_FILE.delete();
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FileWriter command = new FileWriter(COMMAND_FILE); // 写命令写入到recover中
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try {
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command.write(arg);
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command.write("\n");
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} finally {
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command.close();
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}
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// Having written the command file, go ahead and reboot 系统重启
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PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
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pm.reboot("recovery");
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throw new IOException("Reboot failed (no permissions?)");
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}
2、出厂恢复
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/**
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* Reboots the device and wipes the user data partition. This is
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* sometimes called a "factory reset", which is something of a
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* misnomer because the system partition is not restored to its
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* factory state.
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* Requires the {@link android.Manifest.permission#REBOOT} permission.
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*
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* @param context the Context to use
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*
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* @throws IOException if writing the recovery command file
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* fails, or if the reboot itself fails.
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*/
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public static void rebootWipeUserData(Context context) throws IOException {
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final ConditionVariable condition = new ConditionVariable();
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Intent intent = new Intent("android.intent.action.MASTER_CLEAR_NOTIFICATION");
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context.sendOrderedBroadcast(intent, android.Manifest.permission.MASTER_CLEAR,
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new BroadcastReceiver() {
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@Override
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public void onReceive(Context context, Intent intent) {
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condition.open();
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}
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}, null, 0, null, null);
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// Block until the ordered broadcast has completed.
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condition.block();
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bootCommand(context, "--wipe_data");
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}
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/**
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* Reboot into the recovery system to wipe the /cache partition.
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* @throws IOException if something goes wrong.
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*/
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public static void rebootWipeCache(Context context) throws IOException {
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bootCommand(context, "--wipe_cache");
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}
3、验证签名
public static void verifyPackage(File packageFile,
ProgressListener listener,
File deviceCertsZipFile) 请自行阅读源码
后面说一下重启 reboot 命令如何执行的:
无论是 factory reset 工厂恢复还是 安装更新包都会调用到reboot函数,调用 pm.reboot("recovery");
通到jni就是: android_os_Power.cpp
shutdown 调用 android_reboot(ANDROID_RB_POWEROFF, 0, 0);
reboot 调用 android_reboot(ANDROID_RB_RESTART2, 0, (char *) chars);
最终都是调用到下面函数:
int reboot (int mode)
{
return __reboot( LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, mode, NULL );
}
=====linux kernel 内核流程=====
/bionic/libc/arch-arm/syscalls/__reboot.S
这个文件由gensyscalls.py自动产生,调用系统调用 __NR_reboot
bionic/libc/include/sys/linux-syscalls.h
#define __NR_reboot
(__NR_SYSCALL_BASE+88)
/arch/arm/kernel/calls.S
__NR_reboot?就是系统函数sys_reboot
sys_reboot定义在./include/linux/syscalls.h,实现在./kernel/sys.c?sys_reboot会调用kernel_restart
最终kernel_restart调用每一个架构特定的machine_restart,即machine_restart执行每个架构特定的函数
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