（android 关机/重启）Android关机/重启流程解析（2）-----实例解析(多种实现方式)

来源：互联网发布：java基础教程 pdf 编辑：程序博客网时间：2024/05/29 15:24

介入方法1（java）接口：java实现的方式

--------------------------------上层空间--------------------------------

1.frameworks/base/core/java/android/os/PowerManager.java

////在PowerManager的API文档中，给出了一个关机/重启接口：

public void reboot (String reason)

////接口的作用就是重启设备，而且，就算重启成功了也没有返回值。

需要包含REBOOT权限，也就是android.permission.REBOOT

唯一参数reason代表需要的特定重启模式，比如recovery，当然也可以为null

介入方法2（java）接口:java实现的方式

~~(adb: adb shell setprop sys.powerctl reboot,handoff_resolution_enable)~~

SystemProperties.set("ctl.start", "shutdown");///关机

&& SystemProperties.set("sys.powerctl", "reboot," + reason);///重启

（（具体实现例子详见附页2））

4.frameworks/base/services/java/com/android/server/pm/ShutdownThread.java

public static void rebootOrShutdown(boolean reboot, String reason) {
        if (reboot) {
            Log.i(TAG, "Rebooting, reason: " + reason);
            if ( (reason != null) && reason.equals("recovery") ) {
                delayForPlayAnimation();
            }
            try {
                PowerManagerService.lowLevelReboot(reason);
            } catch (Exception e) {
                Log.e(TAG, "Reboot failed, will attempt shutdown instead", e);
            }
        } else if (SHUTDOWN_VIBRATE_MS > 0) {
            // vibrate before shutting down
            Vibrator vibrator = new SystemVibrator();
            try {
                vibrator.vibrate(SHUTDOWN_VIBRATE_MS);
            } 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) {
            }
        }

        delayForPlayAnimation();
        // Shutdown power
        // power off auto test, don't modify
        Log.i(TAG, "Performing low-level shutdown...");
        //PowerManagerService.lowLevelShutdown();////已经注释掉了
        //add your func: HDMI off
        //add for MFR
        try {
            if (ImHDMI == null)
                ImHDMI=MediatekClassFactory.createInstance(IHDMINative.class);
        } catch (Exception e) {
            e.printStackTrace();
        }
        ImHDMI.hdmiPowerEnable(false);

        //unmout data/cache partitions while performing shutdown

        SystemProperties.set("ctl.start", "shutdown");////直接关机shutdown操作

        /* sleep for a long time, prevent start another service */
        try {
            Thread.currentThread().sleep(Integer.MAX_VALUE);
        } catch ( Exception e) {
            Log.e(TAG, "Shutdown rebootOrShutdown Thread.currentThread().sleep exception!");
        }
    }

}

public static void lowLevelShutdown() {
        SystemProperties.set("sys.powerctl", "shutdown");////直接关机
    }

    /**
     * Low-level function to reboot the device. On success, this function
     * doesn't return. If more than 5 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 = "";
        }
        SystemProperties.set("sys.powerctl", "reboot," + reason);///重启
        try {
            Thread.sleep(20000);
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
        }
    }

【注解：】

关机流程中最后是通过修改Android属性进行关机操作(SystemProperties.java通过JNI调用访问系统属性)。

当然我们也可以通过adb命令修改Android系统属性执行关机操作，例如adb shell setpro sys.powerctl shutdown。

这里我们简单介绍下修改Android属性关机的原理或流程。

native_set()<SystemProperties.java>--->SystemProperties_set()<android_os_SystemProperties.cpp>

这是SystemProperties.java类中设置系统函数的方法。

介入方法3（JNI-ndk）接口：java实现的方式

5.frameworks/base/services/jni/com_android_server_PowerManagerService.cpp

static JNINativeMethod gPowerManagerServiceMethods[] = {
/* name, signature, funcPtr */
...
{ "nativeShutdown", "()V",
(void*) nativeShutdown },
{ "nativeReboot", "(Ljava/lang/String;)V",
(void*) nativeReboot },
...
};

这两个好哥俩的实现也是在一起的：（定义如下）

static void nativeShutdown(JNIEnv *env, jobject clazz) {
android_reboot(ANDROID_RB_POWEROFF, 0, 0); ////直接关机
}

static void nativeReboot(JNIEnv *env, jobject clazz, jstring reason) {
if (reason == NULL) {
android_reboot(ANDROID_RB_RESTART, 0, 0); //////无reboot reason的重启
} else {
const char *chars = env->GetStringUTFChars(reason, NULL);
android_reboot(ANDROID_RB_RESTART2, 0, (char *) chars); //////有reboot reason的重启
env->ReleaseStringUTFChars(reason, chars); // In case it fails.
}
jniThrowIOException(env, errno);
}

可以看到无论是关机还是重启，都是调用android_reboot来实现的，只是参数不一样而已。

6.system/core/libcutils/android_reboot.c

      int android_reboot(int cmd, int flags, char *arg)
{
    int ret;

    sync();
    remount_ro();

    switch (cmd) {
        case ANDROID_RB_RESTART://普通重启
            ret = reboot(RB_AUTOBOOT);
            break;

        case ANDROID_RB_POWEROFF://///直接关机
            ret = reboot(RB_POWER_OFF);
            break;

        case ANDROID_RB_RESTART2:
            ret = __reboot(LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2,///有参数的重启直接走这里
                           LINUX_REBOOT_CMD_RESTART2, arg);
            break;

        default:
            ret = -1;
    }

    return ret;
}

介入方法4（kernel）接口（或者是adb 入口方法：adb reboot xx，etc）
（具体实现例子详见附页4）

7.bionic/libc/unistd/reboot.c ///A:\v387-debug\my-ap\bionic\libc\bionic\reboot.c：

int reboot (int mode)
{
return __reboot( LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, mode, NULL );
}

--------------------------------KERNEL域--------------------------------

8.__reboot通过syscall来到内核

这里用一些篇幅简要介绍syscall，以后遇到类似的东西更好追踪一些。

第七步中的__reboot在arm架构的实现是这样的（bionic/libc/arch-arm/syscalls/__reboot.S）

/////home/tonylau/tony-workspace/v387-debug/my-ap/bionic/libc/arch-arm/syscalls/__reboot.S

9.kernel/sys.c

在进入这个文件前，我们先去include/linux/syscalls.h中查看一下sys_reboot的定义：

asmlinkage long sys_reboot(int magic1, int magic2, unsigned int cmd,
void __user *arg);

SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd, void __user *, arg)就是sys_reboot

。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。（以下省略......）

xx.最终调用@@@@kernel/meditek/kernel/kernel/system.c：

void arch_reset(char mode, const char *cmd)

{
    char reboot = 0;
    int res=0;
    struct wd_api*wd_api = NULL;

    res = get_wd_api(&wd_api);
    printk("arch_reset: cmd = %s\n", cmd ? : "NULL");

    if (cmd && !strcmp(cmd, "charger")) {//////
        /* do nothing */
    } else if (cmd && !strcmp(cmd, "recovery")) {/////如果传下来的字符串是recovery=>就在RTC寄存器里设置某个特定值，

                                                              当uboot里读取RTC寄存器的时候如果获取了这个特定值，那就可以起recovery这个动作了
        rtc_mark_recovery();
    } else if (cmd && !strcmp(cmd, "bootloader")){//////////
           rtc_mark_fast();
    }
#ifdef MTK_KERNEL_POWER_OFF_CHARGING
           else if (cmd && !strcmp(cmd, "kpoc")){ rtc_mark_kpoc(); }///////
            #endif
    else {
       reboot = 1;
    }

    if(res){
        printk("arch_reset, get wd api error %d\n",res);
    } else {
        wd_api->wd_sw_reset(reboot);
    }
}

附页2：

 private OnClickListener ButtonSetResolution = new OnClickListener(){        @Override        public void onClick(View view) {            try {                Class<?> c = Class.forName("android.os.SystemProperties");                Object object1 = c.newInstance();                java.lang.reflect.Method getmethod = c.getDeclaredMethod("get", String.class);                java.lang.reflect.Method setmethod = c.getDeclaredMethod("set", String.class, String.class);                setmethod.invoke(object1, "sys.powerctl", "reboot,handoff_resolution_enable");   ////2015-06-03                //setmethod.invoke(object1, "sys.lucid.PowerXtend.loglevel", Integer.toString(1));            } catch (Exception e) {                e.printStackTrace();            }        }    };

附页4：refer http://blog.sina.com.cn/s/blog_474928c90100zxkb.html

1、在Android源码目录中的packages/apps/下创建一个目录，例如：Hello。2、编写Android.mk文件：LOCAL_PATH:= $(call my-dir)include $(CLEAR_VARS)LOCAL_SRC_FILES:= shutdown.cLOCAL_MODULE:= shutdown LOCAL_PRELINK_MODULE:= falseLOCAL_SHARED_LIBRARIES:= libutilsinclude $(BUILD_EXECUTABLE)3、编写shutdown.c源文件，如下：

#include <stdio.h>#include <stdlib.h>#include <utils/Log.h>#include <sys/reboot.h>#ifndef LOG_TAG#define LOG_TAG "dxyh"#endifint main(int argc, char **argv){int retval;if ((retval = __reboot(LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2,RB_POWER_OFF, NULL)) < 0) {LOGE("Try to shutdown the machine failed!");exit(EXIT_FAILURE);}return 0;}

<span style="color:#000000;"><span style="font-size:16px"><span style="background:none repeat scroll 0% 0% transparent">4</span></span><span style="background:none repeat scroll 0% 0% transparent"><span style="font-size:16px">、</span><span style="font-size:16px">mm</span></span></span><span style="color:#000000;"><span style="font-size:16px"><span style="background:none repeat scroll 0% 0% transparent">5</span></span><span style="background:none repeat scroll 0% 0% transparent"><span style="font-size:16px">、将生成的</span><span style="font-size:16px">shutdown</span></span><span style="background:none repeat scroll 0% 0% transparent"><span style="font-size:16px">可执行程序推入到</span><span style="font-size:16px">pad</span></span><span style="background:none repeat scroll 0% 0% transparent"><span style="font-size:16px">中的</span><span style="font-size:16px">/system/bin</span></span><span style="background:none repeat scroll 0% 0% transparent"><span style="font-size:16px">下即可。</span></span></span><span style="color:#000000;"><span style="font-size:16px"><span style="background:none repeat scroll 0% 0% transparent">6</span></span><span style="background:none repeat scroll 0% 0% transparent"><span style="font-size:16px">、然后就可以和其他命令一样运行了，例如</span><span style="font-size:16px">adb shell shutdown</span></span><span style="background:none repeat scroll 0% 0% transparent"><span style="font-size:16px">。</span></span></span>

0 0

（android 关机/重启）Android关机/重启流程解析 （2）-----实例解析(多种实现方式)