在PowerManager的API文檔中,給出瞭一個關機/重啟接口:
public void reboot (String reason)
對於這個接口的描述很簡單,就是幾句話。
接口的作用就是重啟設備,而且,就算重啟成功瞭也沒有返回值。
需要包含REBOOT權限,也就是android.permission.REBOOT
唯一參數reason代表需要的特定重啟模式,比如recovery,當然也可以為null。
——————————–上層空間——————————–
1.frameworks/base/core/java/android/os/PowerManager.java
[java]
* Reboot the device. Will not return if the reboot is
* successful. Requires the {@link android.Manifest.permission#REBOOT}
* permission.
*
* @param reason code to pass to the kernel (e.g., "recovery") to
* request special boot modes, or null.
*/
public void reboot(String reason)
{
try {
mService.reboot(reason);
} catch (RemoteException e) {
}
}
/**
* Reboot the device. Will not return if the reboot is
* successful. Requires the {@link android.Manifest.permission#REBOOT}
* permission.
*
* @param reason code to pass to the kernel (e.g., "recovery") to
* request special boot modes, or null.
*/
public void reboot(String reason)
{
try {
mService.reboot(reason);
} catch (RemoteException e) {
}
}
mService為IPowerManager Binder接口服務。
[java]
/**
* {@hide}
*/
public PowerManager(IPowerManager service, Handler handler)
{
mService = service;
mHandler = handler;
}
/**
* {@hide}
*/
public PowerManager(IPowerManager service, Handler handler)
{
mService = service;
mHandler = handler;
}
2.frameworks/base/core/java/android/os/IPowerManager.aidl
[java]
interface IPowerManager
{
…
void reboot(String reason);
…
}
interface IPowerManager
{
…
void reboot(String reason);
…
}
3.frameworks/base/services/java/com/android/server/PowerManagerService.java
[java]
/**
* Reboot the device immediately, passing 'reason' (may be null)
* to the underlying __reboot system call. Should not return.
*/
public void reboot(String reason)
{
mContext.enforceCallingOrSelfPermission(android.Manifest.permission.REBOOT, null);
if (mHandler == null || !ActivityManagerNative.isSystemReady()) {
throw new IllegalStateException("Too early to call reboot()");
}
final String finalReason = reason;
Runnable runnable = new Runnable() {
public void run() {
synchronized (this) {
ShutdownThread.reboot(getUiContext(), finalReason, false);
}
}
};
// ShutdownThread must run on a looper capable of displaying the UI.
mHandler.post(runnable);
// PowerManager.reboot() is documented not to return so just wait for the inevitable.
synchronized (runnable) {
while (true) {
try {
runnable.wait();
} catch (InterruptedException e) {
}
}
}
}
/**
* Reboot the device immediately, passing 'reason' (may be null)
* to the underlying __reboot system call. Should not return.
*/
public void reboot(String reason)
{
mContext.enforceCallingOrSelfPermission(android.Manifest.permission.REBOOT, null);
if (mHandler == null || !ActivityManagerNative.isSystemReady()) {
throw new IllegalStateException("Too early to call reboot()");
}
final String finalReason = reason;
Runnable runnable = new Runnable() {
public void run() {
synchronized (this) {
ShutdownThread.reboot(getUiContext(), finalReason, false);
}
}
};
// ShutdownThread must run on a looper capable of displaying the UI.
mHandler.post(runnable);
// PowerManager.reboot() is documented not to return so just wait for the inevitable.
synchronized (runnable) {
while (true) {
try {
runnable.wait();
} catch (InterruptedException e) {
}
}
}
}
4.frameworks/base/services/java/com/android/server/pm/ShutdownThread.java
[java]
/**
* Request a clean shutdown, waiting for subsystems to clean up their
* state etc. Must be called from a Looper thread in which its UI
* is shown.
*
* @param context Context used to display the shutdown progress dialog.
* @param reason code to pass to the kernel (e.g. "recovery"), or null.
* @param confirm true if user confirmation is needed before shutting down.
*/
public static void reboot(final Context context, String reason, boolean confirm) {
mReboot = true;
mRebootSafeMode = false;
mRebootReason = reason;
shutdownInner(context, confirm);
}
/**
* Request a clean shutdown, waiting for subsystems to clean up their
* state etc. Must be called from a Looper thread in which its UI
* is shown.
*
* @param context Context used to display the shutdown progress dialog.
* @param reason code to pass to the kernel (e.g. "recovery"), or null.
* @param confirm true if user confirmation is needed before shutting down.
*/
public static void reboot(final Context context, String reason, boolean confirm) {
mReboot = true;
mRebootSafeMode = false;
mRebootReason = reason;
shutdownInner(context, confirm);
}
這裡說明是需要重啟,且不是安全模式,重啟參數為傳遞下來的reason,shutdownInner的confirm參數是用來設置是否有確認提示框的,通過reboot接口調用重啟是沒有的,為false。
重啟的實現在run()中,因為ShutdownThread是Thread的擴展,所以run會自動運行。
[java]
/**
* Makes sure we handle the shutdown gracefully.
* Shuts off power regardless of radio and bluetooth state if the alloted time has passed.
*/
public void run() {
BroadcastReceiver br = new BroadcastReceiver() {
@Override public void onReceive(Context context, Intent intent) {
// We don't allow apps to cancel this, so ignore the result.
actionDone();
}
};
/*
* Write a system property in case the system_server reboots before we
* get to the actual hardware restart. If that happens, we'll retry at
* the beginning of the SystemServer startup.
*/
{
String reason = (mReboot ? "1" : "0") + (mRebootReason != null ? mRebootReason : "");
SystemProperties.set(SHUTDOWN_ACTION_PROPERTY, reason);
}
/*
* If we are rebooting into safe mode, write a system property
* indicating so.
*/
if (mRebootSafeMode) {
SystemProperties.set(REBOOT_SAFEMODE_PROPERTY, "1");
}
…
rebootOrShutdown(mReboot, mRebootReason);
}
/**
* Makes sure we handle the shutdown gracefully.
* Shuts off power regardless of radio and bluetooth state if the alloted time has passed.
*/
public void run() {
BroadcastReceiver br = new BroadcastReceiver() {
@Override public void onReceive(Context context, Intent intent) {
// We don't allow apps to cancel this, so ignore the result.
actionDone();
}
};
/*
* Write a system property in case the system_server reboots before we
* get to the actual hardware restart. If that happens, we'll retry at
* the beginning of the SystemServer startup.
*/
{
String reason = (mReboot ? "1" : "0") + (mRebootReason != null ? mRebootReason : "");
SystemProperties.set(SHUTDOWN_ACTION_PROPERTY, reason);
}
/*
* If we are rebooting into safe mode, write a system property
* indicating so.
*/
if (mRebootSafeMode) {
SystemProperties.set(REBOOT_SAFEMODE_PROPERTY, "1");
}
…
rebootOrShutdown(mReboot, mRebootReason);
}
在重啟前會將重啟原因寫入sys.shutdown.requested,如果沒有則為空,如果是安全模式還會將persist.sys.safemode置1,之後會進行一些關機前的預處理,關閉ActivityManager以及MountService,最終調用rebootOrShutdown進行關機操作。
[java]
/**
* Do not call this directly. Use {@link #reboot(Context, String, boolean)}
* or {@link #shutdown(Context, boolean)} instead.
*
* @param reboot true to reboot or false to shutdown
* @param reason reason for reboot
*/
public static void rebootOrShutdown(boolean reboot, String reason) {
if (reboot) {
Log.i(TAG, "Rebooting, reason: " + reason);
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) {
}
}
// Shutdown power
Log.i(TAG, "Performing low-level shutdown…");
PowerManagerService.lowLevelShutdown();
}
}
/**
* Do not call this directly. Use {@link #reboot(Context, String, boolean)}
* or {@link #shutdown(Context, boolean)} instead.
*
* @param reboot true to reboot or false to shutdown
* @param reason reason for reboot
*/
public static void rebootOrShutdown(boolean reboot, String reason) {
if (reboot) {
Log.i(TAG, "Rebooting, reason: " + reason);
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) {
}
}
// Shutdown power
Log.i(TAG, "Performing low-level shutdown…");
PowerManagerService.lowLevelShutdown();
}
}
如果確認重啟,則調用PowerManagerService的lowLevelReboot函數,參數就是傳遞下來的reason,稍後分析。如果不是重啟,即mReboot=false,那就是需要關機瞭,在shutdown函數中就能夠知道。
[jav
/**
* Request a clean shutdown, waiting for subsystems to clean up their
* state etc. Must be called from a Looper thread in which its UI
* is shown.
*
* @param context Context used to display the shutdown progress dialog.
* @param confirm true if user confirmation is needed before shutting down.
*/
public static void shutdown(final Context context, boolean confirm) {
mReboot = false;
mRebootSafeMode = false;
shutdownInner(context, confirm);
}
/**
* Request a clean shutdown, waiting for subsystems to clean up their
* state etc. Must be called from a Looper thread in which its UI
* is shown.
*
* @param context Context used to display the shutdown progress dialog.
* @param confirm true if user confirmation is needed before shutting down.
*/
public static void shutdown(final Context context, boolean confirm) {
mReboot = false;
mRebootSafeMode = false;
shutdownInner(context, confirm);
}
關機的時候需要震動,就是這裡瞭SHUTDOWN_VIBRATE_MS,默認的定義是500ms。但是在代碼上看,無論如何,最後都會調用一下lowLevelShutdown函數,也就是關機。邏輯上,這裡可能是個問題,但是實際中,如果重啟操作能夠調用成功的話,整個系統都重啟瞭,後邊的代碼當然不可能執行到瞭。
目光轉回PowerManagerService
4.frameworks/base/services/java/com/android/server/PowerManagerService.java
[java] ?
/**
* Low-level function to reboot the device.
*
* @param reason code to pass to the kernel (e.g. "recovery"), or null.
* @throws IOException if reboot fails for some reason (eg, lack of
* permission)
*/
public static void lowLevelReboot(String reason) throws IOException {
nativeReboot(reason);
}
/**
* Low-level function turn the device off immediately, without trying
* to be clean. Most people should use
* {@link com.android.server.pm.internal.app.ShutdownThread} for a clean shutdown.
*/
public static void lowLevelShutdown() {
nativeShutdown();
}
/**
* Low-level function to reboot the device.
*
* @param reason code to pass to the kernel (e.g. "recovery"), or null.
* @throws IOException if reboot fails for some reason (eg, lack of
* permission)
*/
public static void lowLevelReboot(String reason) throws IOException {
nativeReboot(reason);
}
/**
* Low-level function turn the device off immediately, without trying
* to be clean. Most people should use
* {@link com.android.server.pm.internal.app.ShutdownThread} for a clean shutdown.
*/
public static void lowLevelShutdown() {
nativeShutdown();
}
很熟悉的字樣native,是JNI調用瞭:
[java]
private static native void nativeShutdown();
private static native void nativeReboot(String reason) throws IOException;
private static native void nativeShutdown();
private static native void nativeReboot(String reason) throws IOException;
5.frameworks/base/services/jni/com_android_server_PowerManagerService.cpp
[cpp]
static JNINativeMethod gPowerManagerServiceMethods[] = {
/* name, signature, funcPtr */
…
{ "nativeShutdown", "()V",
(void*) nativeShutdown },
{ "nativeReboot", "(Ljava/lang/String;)V",
(void*) nativeReboot },
…
};
static JNINativeMethod gPowerManagerServiceMethods[] = {
/* name, signature, funcPtr */
…
{ "nativeShutdown", "()V",
(void*) nativeShutdown },
{ "nativeReboot", "(Ljava/lang/String;)V",
(void*) nativeReboot },
…
};
這兩個好哥倆的實現也是在一起的:
[cpp]
static void nativeShutdown(JNIEnv *env, jobject clazz) {
android_reboot(ANDROID_RB_POWEROFF, 0, 0);
}
static void nativeReboot(JNIEnv *env, jobject clazz, jstring reason) {
if (reason == NULL) {
android_reboot(ANDROID_RB_RESTART, 0, 0);
} else {
const char *chars = env->GetStringUTFChars(reason, NULL);
android_reboot(ANDROID_RB_RESTART2, 0, (char *) chars);
env->ReleaseStringUTFChars(reason, chars); // In case it fails.
}
jniThrowIOException(env, errno);
}
static void nativeShutdown(JNIEnv *env, jobject clazz) {
android_reboot(ANDROID_RB_POWEROFF, 0, 0);
}
static void nativeReboot(JNIEnv *env, jobject clazz, jstring reason) {
if (reason == NULL) {
android_reboot(ANDROID_RB_RESTART, 0, 0);
} else {
const char *chars = env->GetStringUTFChars(reason, NULL);
android_reboot(ANDROID_RB_RESTART2, 0, (char *) chars);
env->ReleaseStringUTFChars(reason, chars); // In case it fails.
}
jniThrowIOException(env, errno);
}
可以看到無論是關機還是重啟,都是調用android_reboot來實現的,隻是參數不一樣而已。
6.system/core/libcutils/android_reboot.c
[cpp]
int android_reboot(int cmd, int flags, char *arg)
{
int ret = 0;
int reason = -1;
#ifdef RECOVERY_PRE_COMMAND
if (cmd == (int) ANDROID_RB_RESTART2) {
if (arg && strlen(arg) > 0) {
char cmd[PATH_MAX];
sprintf(cmd, RECOVERY_PRE_COMMAND " %s", arg);
system(cmd);
}
}
#endif
if (!(flags & ANDROID_RB_FLAG_NO_SYNC))
sync();
if (!(flags & ANDROID_RB_FLAG_NO_REMOUNT_RO))
remount_ro();
switch (cmd) {
case ANDROID_RB_RESTART:
reason = RB_AUTOBOOT;
break;
case ANDROID_RB_POWEROFF:
ret = reboot(RB_POWER_OFF);
return ret;
case ANDROID_RB_RESTART2:
// REBOOT_MAGIC
break;
default:
return -1;
}
#ifdef RECOVERY_PRE_COMMAND_CLEAR_REASON
reason = RB_AUTOBOOT;
#endif
if (reason != -1)
ret = reboot(reason);
else
ret = __reboot(LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2,
LINUX_REBOOT_CMD_RESTART2, arg);
return ret;
}
int android_reboot(int cmd, int flags, char *arg)
{
int ret = 0;
int reason = -1;
#ifdef RECOVERY_PRE_COMMAND
if (cmd == (int) ANDROID_RB_RESTART2) {
if (arg && strlen(arg) > 0) {
char cmd[PATH_MAX];
sprintf(cmd, RECOVERY_PRE_COMMAND " %s", arg);
system(cmd);
}
}
#endif
if (!(flags & ANDROID_RB_FLAG_NO_SYNC))
sync();
if (!(flags & ANDROID_RB_FLAG_NO_REMOUNT_RO))
remount_ro();
switch (cmd) {
case ANDROID_RB_RESTART:
reason = RB_AUTOBOOT;
break;
case ANDROID_RB_POWEROFF:
ret = reboot(RB_POWER_OFF);
return ret;
case ANDROID_RB_RESTART2:
// REBOOT_MAGIC
break;
default:
return -1;
}
#ifdef RECOVERY_PRE_COMMAND_CLEAR_REASON
reason = RB_AUTOBOOT;
#endif
if (reason != -1)
ret = reboot(reason);
else
ret = __reboot(LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2,
LINUX_REBOOT_CMD_RESTART2, arg);
return ret;
}
以reboot recovery為例,arg即為recovery,所在在第五步的時候會傳入ANDROID_RB_RESTART2。到瞭android_reboot函數中,會看到這樣的定義#ifdef RECOVERY_PRE_COMMAND,即屬於重啟前會執行的命令,如果定義瞭就會執行。
下面也是做瞭一些關機重啟前的預處理工作,sync()作用是將緩存中的信息寫入磁盤,以免程序異常結束導致文件被損壞,linux系統關機前會做幾次這樣的動作;而remount_ro()作用是通過調用emergency_remount()強制將文件系統掛載為隻讀,不再允許任何寫入操作,同時會通過檢查/proc/mounts的設備狀態來確認是否當前的所有寫入工作已經完成,這個檢查過程是阻塞操作。
接下來才是對參數的解析處理:
1)普通重啟 ANDROID_RB_RESTART, reason = RB_AUTOBOOT;
2)關機 ANDROID_RB_POWEROFF, 無需reason,直接調用reboot進行關機;
3)帶參數的特殊重啟 ANDROID_RB_RESTART2, reason 將為默認值 -1
這裡又出現一個#ifdef RECOVERY_PRE_COMMAND_CLEAR_REASON,如果定義瞭它,則無論上層傳下來的參數是什麼樣的,最終都隻是普通重啟而已。定義它的方式是在BoardConfig.mk中加入TARGET_RECOVERY_PRE_COMMAND_CLEAR_REASON := true,應該有廠商會喜歡這麼做的,畢竟除瞭普通重啟,都可能帶給用戶一定的風險。
最後會對reason進行一個檢測,那麼通過上邊的分析,其實隻有帶參數的特殊重啟才會為-1,而不等於-1的情況中有普通重啟和關機,而關機已經自行解決瞭……所以,不等於-1的情況到瞭這裡也隻有普通重啟瞭。最終這裡就是區分普通重啟與特殊重啟的地方瞭。這裡再插入一個問題,其他的幾個cmd都是什麼值呢?答案在bionic/libc/include/sys/reboot.h中:
[cpp]
#define RB_AUTOBOOT LINUX_REBOOT_CMD_RESTART
#define RB_HALT_SYSTEM LINUX_REBOOT_CMD_HALT
#define RB_ENABLE_CAD LINUX_REBOOT_CMD_CAD_ON
#define RB_DISABLE_CAD LINUX_REBOOT_CMD_CAD_OFF
#define RB_POWER_OFF LINUX_REBOOT_CMD_POWER_OFF
#define RB_AUTOBOOT LINUX_REBOOT_CMD_RESTART
#define RB_HALT_SYSTEM LINUX_REBOOT_CMD_HALT
#define RB_ENABLE_CAD LINUX_REBOOT_CMD_CAD_ON
#define RB_DISABLE_CAD LINUX_REBOOT_CMD_CAD_OFF
#define RB_POWER_OFF LINUX_REBOOT_CMD_POWER_OFF
而,LINUX_REBOOT_XXXX之類的在bionic/libc/kernel/common/linux/reboot.h中:
[cpp]
#define LINUX_REBOOT_MAGIC1 0xfee1dead
#define LINUX_REBOOT_MAGIC2 672274793
/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE – SEE TOP FOR INSTRUCTIONS */
#define LINUX_REBOOT_MAGIC2A 85072278
#define LINUX_REBOOT_MAGIC2B 369367448
#define LINUX_REBOOT_MAGIC2C 537993216
#define LINUX_REBOOT_CMD_RESTART 0x01234567
/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE – SEE TOP FOR INSTRUCTIONS */
#define LINUX_REBOOT_CMD_HALT 0xCDEF0123
#define LINUX_REBOOT_CMD_CAD_ON 0x89ABCDEF
#define LINUX_REBOOT_CMD_CAD_OFF 0x00000000
#define LINUX_REBOOT_CMD_POWER_OFF 0x4321FEDC
/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE – SEE TOP FOR INSTRUCTIONS */
#define LINUX_REBOOT_CMD_RESTART2 0xA1B2C3D4
#define LINUX_REBOOT_CMD_SW_SUSPEND 0xD000FCE2
#define LINUX_REBOOT_CMD_KEXEC 0x45584543
#define LINUX_REBOOT_MAGIC1 0xfee1dead
#define LINUX_REBOOT_MAGIC2 672274793
/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE – SEE TOP FOR INSTRUCTIONS */
#define LINUX_REBOOT_MAGIC2A 85072278
#define LINUX_REBOOT_MAGIC2B 369367448
#define LINUX_REBOOT_MAGIC2C 537993216
#define LINUX_REBOOT_CMD_RESTART 0x01234567
/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE – SEE TOP FOR INSTRUCTIONS */
#define LINUX_REBOOT_CMD_HALT 0xCDEF0123
#define LINUX_REBOOT_CMD_CAD_ON 0x89ABCDEF
#define LINUX_REBOOT_CMD_CAD_OFF 0x00000000
#define LINUX_REBOOT_CMD_POWER_OFF 0x4321FEDC
/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE – SEE TOP FOR INSTRUCTIONS */
#define LINUX_REBOOT_CMD_RESTART2 0xA1B2C3D4
#define LINUX_REBOOT_CMD_SW_SUSPEND 0xD000FCE2
#define LINUX_REBOOT_CMD_KEXEC 0x45584543至於為什麼他們是這樣奇怪的值這個問題,我隻能說他們是magic number,魔法嘛,本來就是正常人不能夠理解的,所以~~~放過他們吧,隻要知道他們沒有是-1的就OK啦。
先來看reboot函數,按照往常的經驗,reboot最終一定會調用到__reboot的。
7.bionic/libc/unistd/reboot.c
[cpp]
int reboot (int mode)
{
return __reboot( LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, mode, NULL );
}
int reboot (int mode)
{
return __reboot( LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, mode, NULL );
}
Bingo!果然是這樣,如此說來reboot(reason) -> reboot(RB_AUTOBOOT) -> __reboot( LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, LINUX_REBOOT_CMD_RESTART, NULL ),要是直接這樣寫多好~~~免得繞這一層瞭。
——————————–KERNEL域——————————–
8.__reboot通過syscall來到內核
這裡用一些篇幅簡要介紹syscall,以後遇到類似的東西更好追蹤一些。
第七步中的__reboot在arm架構的實現是這樣的(bionic/libc/arch-arm/syscalls/__reboot.S)
[plain]
ENTRY(__reboot)
.save {r4, r7}
stmfd sp!, {r4, r7}
ldr r7, =__NR_reboot
swi #0
ldmfd sp!, {r4, r7}
movs r0, r0
bxpl lr
b __set_syscall_errno
END(__reboot)
ENTRY(__reboot)
.save {r4, r7}
stmfd sp!, {r4, r7}
ldr r7, =__NR_reboot
swi #0
ldmfd sp!, {r4, r7}
movs r0, r0
bxpl lr
b __set_syscall_errno
END(__reboot)
可以看出來,這裡將__reboot的實現映射到瞭__NR_reboot, 而在bionic/libc/sys/linux-syscalls.h能夠找到:
[plain]
#define __NR_reboot (__NR_SYSCALL_BASE + 88)
#define __NR_reboot (__NR_SYSCALL_BASE + 88)
其被指定瞭一個固定的偏移量,在被調用的時候就是通過這個偏移量去內核中尋找對應的入口的,由此可見,內核中一定有著相同的定義,否則將不能成功調用。內核中對syscall偏移量的定義在內核源碼中的arch/arm/include/asm/unistd.h,相關信息完全一致。
已經找到瞭內核中的對應映射,那麼下一步就要去找尋真正的實現函數瞭,在include/asm-generic/unistd.h中可以找到內核對__NR_reboot的syscall函數映射,即
[cpp]
/* kernel/sys.c */
#define __NR_setpriority 140
__SYSCALL(__NR_setpriority, sys_setpriority)
#define __NR_getpriority 141
__SYSCALL(__NR_getpriority, sys_getpriority)
#define __NR_reboot 142
__SYSCALL(__NR_reboot, sys_reboot)
/* kernel/sys.c */
#define __NR_setpriority 140
__SYSCALL(__NR_setpriority, sys_setpriority)
#define __NR_getpriority 141
__SYSCALL(__NR_getpriority, sys_getpriority)
#define __NR_reboot 142
__SYSCALL(__NR_reboot, sys_reboot)
同時,能夠發現如此溫馨的一幕,內核已經指引我們下一步該去哪裡尋找sys_reboot,即kernel/sys.c。
9.kernel/sys.c
在進入這個文件前,我們先去include/linux/syscalls.h中查看一下sys_reboot的定義:
[cpp]
asmlinkage long sys_reboot(int magic1, int magic2, unsigned int cmd,
void __user *arg);
asmlinkage long sys_reboot(int magic1, int magic2, unsigned int cmd,
void __user *arg);
與__reboot的調用參數一致。
進入sys.c文件後,並沒有找到名為sys_reboot的函數,而通過仔細查找,發現一個很有趣的函數,其定義為SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd, void __user *, arg),對比__reboot的參數,能夠符合。究竟是不是這個函數?
同樣在include/linux/syscalls.h文件中,能夠找到這樣幾個定義:
[cpp]
#define SYSCALL_DEFINE1(name, …) SYSCALL_DEFINEx(1, _##name, __VA_ARGS__)
#define SYSCALL_DEFINE2(name, …) SYSCALL_DEFINEx(2, _##name, __VA_ARGS__)
#define SYSCALL_DEFINE3(name, …) SYSCALL_DEFINEx(3, _##name, __VA_ARGS__)
#define SYSCALL_DEFINE4(name, …) SYSCALL_DEFINEx(4, _##name, __VA_ARGS__)
#define SYSCALL_DEFINE5(name, …) SYSCALL_DEFINEx(5, _##name, __VA_ARGS__)
#define SYSCALL_DEFINE6(name, …) SYSCALL_DEFINEx(6, _##name, __VA_ARGS__)
…
#define SYSCALL_DEFINEx(x, sname, …) \
__SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
…
#define __SYSCALL_DEFINEx(x, name, …) \
asmlinkage long sys##name(__SC_DECL##x(__VA_ARGS__))
#define SYSCALL_DEFINE1(name, …) SYSCALL_DEFINEx(1, _##name, __VA_ARGS__)
#define SYSCALL_DEFINE2(name, …) SYSCALL_DEFINEx(2, _##name, __VA_ARGS__)
#define SYSCALL_DEFINE3(name, …) SYSCALL_DEFINEx(3, _##name, __VA_ARGS__)
#define SYSCALL_DEFINE4(name, …) SYSCALL_DEFINEx(4, _##name, __VA_ARGS__)
#define SYSCALL_DEFINE5(name, …) SYSCALL_DEFINEx(5, _##name, __VA_ARGS__)
#define SYSCALL_DEFINE6(name, …) SYSCALL_DEFINEx(6, _##name, __VA_ARGS__)
…
#define SYSCALL_DEFINEx(x, sname, …) \
__SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
…
#define __SYSCALL_DEFINEx(x, name, …) \
asmlinkage long sys##name(__SC_DECL##x(__VA_ARGS__))
整合後等價於:
[cpp
#define SYSCALL_DEFINE4(name, …) \
asmlinkage long sys##_name(__SC_DECL##4(__VA_ARGS__))
#define SYSCALL_DEFINE4(name, …) \
asmlinkage long sys##_name(__SC_DECL##4(__VA_ARGS__))
這樣就不難看出,SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd, void __user *, arg)就是sys_reboot,也就是上層調用的__reboot的最終實現。函數實現如下:
[cpp]
/*
* Reboot system call: for obvious reasons only root may call it,
* and even root needs to set up some magic numbers in the registers
* so that some mistake won't make this reboot the whole machine.
* You can also set the meaning of the ctrl-alt-del-key here.
*
* reboot doesn't sync: do that yourself before calling this.
*/
SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
void __user *, arg)
{
char buffer[256];
int ret = 0;
/* We only trust the superuser with rebooting the system. */
if (!capable(CAP_SYS_BOOT))
return -EPERM;
/* For safety, we require "magic" arguments. */
if (magic1 != LINUX_REBOOT_MAGIC1 ||
(magic2 != LINUX_REBOOT_MAGIC2 &&
magic2 != LINUX_REBOOT_MAGIC2A &&
magic2 != LINUX_REBOOT_MAGIC2B &&
magic2 != LINUX_REBOOT_MAGIC2C))
return -EINVAL;
/* Instead of trying to make the power_off code look like
* halt when pm_power_off is not set do it the easy way.
*/
if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
cmd = LINUX_REBOOT_CMD_HALT;
mutex_lock(&reboot_mutex);
switch (cmd) {
case LINUX_REBOOT_CMD_RESTART:
kernel_restart(NULL);
break;
case LINUX_REBOOT_CMD_CAD_ON:
C_A_D = 1;
break;
case LINUX_REBOOT_CMD_CAD_OFF:
C_A_D = 0;
break;
case LINUX_REBOOT_CMD_HALT:
kernel_halt();
do_exit(0);
panic("cannot halt");
case LINUX_REBOOT_CMD_POWER_OFF:
kernel_power_off();
do_exit(0);
break;
case LINUX_REBOOT_CMD_RESTART2:
if (strncpy_from_user(&buffer[0], arg, sizeof(buffer) – 1) < 0) {
ret = -EFAULT;
break;
}
buffer[sizeof(buffer) – 1] = '\0';
kernel_restart(buffer);
break;
#ifdef CONFIG_KEXEC
case LINUX_REBOOT_CMD_KEXEC:
ret = kernel_kexec();
break;
#endif
#ifdef CONFIG_HIBERNATION
case LINUX_REBOOT_CMD_SW_SUSPEND:
ret = hibernate();
break;
#endif
default:
ret = -EINVAL;
break;
}
mutex_unlock(&reboot_mutex);
return ret;
}
/*
* Reboot system call: for obvious reasons only root may call it,
* and even root needs to set up some magic numbers in the registers
* so that some mistake won't make this reboot the whole machine.
* You can also set the meaning of the ctrl-alt-del-key here.
*
* reboot doesn't sync: do that yourself before calling this.
*/
SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
void __user *, arg)
{
char buffer[256];
int ret = 0;
/* We only trust the superuser with rebooting the system. */
if (!capable(CAP_SYS_BOOT))
return -EPERM;
/* For safety, we require "magic" arguments. */
if (magic1 != LINUX_REBOOT_MAGIC1 ||
(magic2 != LINUX_REBOOT_MAGIC2 &&
magic2 != LINUX_REBOOT_MAGIC2A &&
magic2 != LINUX_REBOOT_MAGIC2B &&
magic2 != LINUX_REBOOT_MAGIC2C))
return -EINVAL;
/* Instead of trying to make the power_off code look like
* halt when pm_power_off is not set do it the easy way.
*/
if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
cmd = LINUX_REBOOT_CMD_HALT;
mutex_lock(&reboot_mutex);
switch (cmd) {
case LINUX_REBOOT_CMD_RESTART:
kernel_restart(NULL);
break;
case LINUX_REBOOT_CMD_CAD_ON:
C_A_D = 1;
break;
case LINUX_REBOOT_CMD_CAD_OFF:
C_A_D = 0;
break;
case LINUX_REBOOT_CMD_HALT:
kernel_halt();
do_exit(0);
panic("cannot halt");
case LINUX_REBOOT_CMD_POWER_OFF:
kernel_power_off();
do_exit(0);
break;
case LINUX_REBOOT_CMD_RESTART2:
if (strncpy_from_user(&buffer[0], arg, sizeof(buffer) – 1) < 0) {
ret = -EFAULT;
break;
}
buffer[sizeof(buffer) – 1] = '\0';
kernel_restart(buffer);
break;
#ifdef CONFIG_KEXEC
case LINUX_REBOOT_CMD_KEXEC:
ret = kernel_kexec();
break;
#endif
#ifdef CONFIG_HIBERNATION
case LINUX_REBOOT_CMD_SW_SUSPEND:
ret = hibernate();
break;
#endif
default:
ret = -EINVAL;
break;
}
mutex_unlock(&reboot_mutex);
return ret;
}
在此函數中,首先會檢測權限問題,隻有超級用戶才可以執行重啟系統的操作:
[cpp]
/* We only trust the superuser with rebooting the system. */
if (!capable(CAP_SYS_BOOT))
return -EPERM;
/* We only trust the superuser with rebooting the system. */
if (!capable(CAP_SYS_BOOT))
return -EPERM;
否則將返回權限錯誤。對應的權限列表在include/linux/capability.h中,重啟操作為22.
隨後對magic number進行瞭校驗:
[cpp]
/* For safety, we require "magic" arguments. */
if (magic1 != LINUX_REBOOT_MAGIC1 ||
(magic2 != LINUX_REBOOT_MAGIC2 &&
magic2 != LINUX_REBOOT_MAGIC2A &&
magic2 != LINUX_REBOOT_MAGIC2B &&
magic2 != LINUX_REBOOT_MAGIC2C))
return -EINVAL;
/* For safety, we require "magic" arguments. */
if (magic1 != LINUX_REBOOT_MAGIC1 ||
(magic2 != LINUX_REBOOT_MAGIC2 &&
magic2 != LINUX_REBOOT_MAGIC2A &&
magic2 != LINUX_REBOOT_MAGIC2B &&
magic2 != LINUX_REBOOT_MAGIC2C))
return -EINVAL;
如果數據傳輸過程中沒有發生錯誤的話,這裡也當然不會有問題,所以隻是一個安全性校驗,基本不會發生錯誤。
之後有一個很有趣的檢查,如果用戶要求關機,而pm_power_off為空的話,就把用戶的關機命令轉換為掛起:
[cpp]
/* Instead of trying to make the power_off code look like
* halt when pm_power_off is not set do it the easy way.
*/
if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
cmd = LINUX_REBOOT_CMD_HALT;
/* Instead of trying to make the power_off code look like
* halt when pm_power_off is not set do it the easy way.
*/
if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
cmd = LINUX_REBOOT_CMD_HALT;
在arch/arm/kernel/process.c中可以找到它的定義:
[cpp]
/*
* Function pointers to optional machine specific functions
*/
void (*pm_power_off)(void);
EXPORT_SYMBOL(pm_power_off);
/*
* Function pointers to optional machine specific functions
*/
void (*pm_power_off)(void);
EXPORT_SYMBOL(pm_power_off);
好的,隻是一個函數指針,而且做瞭全局操作,整個kernel都可以調用它。以高通msm7x30為例,在arch/arm/mach-msm/pm2.c中對這個函數指針進行瞭賦值:
[cpp]
pm_power_off = msm_pm_power_off;
pm_power_off = msm_pm_power_off;
msm_pm_power_off的具體實現就不再跟蹤瞭,各傢的都不一樣,跟下去沒有太大意義。現在隻要知道,我分析的這個kernel是給瞭這個函數指針賦值的,所以不為空,關機命令將正常執行。
接下來就是這個函數的正題瞭,對用戶命令進行解析操作,同時這個過程是用reboot_mutex互斥鎖來進行保護的,以保證同一時間隻可能有一個解析過程,避免沖突。
下邊貼出所有關機重啟相關的命令定義:
[cpp]
/*
* Commands accepted by the _reboot() system call.
*
* RESTART Restart system using default command and mode.
* HALT Stop OS and give system control to ROM monitor, if any.
* CAD_ON Ctrl-Alt-Del sequence causes RESTART command.
* CAD_OFF Ctrl-Alt-Del sequence sends SIGINT to init task.
* POWER_OFF Stop OS and remove all power from system, if possible.
* RESTART2 Restart system using given command string.
* SW_SUSPEND Suspend system using software suspend if compiled in.
* KEXEC Restart system using a previously loaded Linux kernel
*/
#define LINUX_REBOOT_CMD_RESTART 0x01234567
#define LINUX_REBOOT_CMD_HALT 0xCDEF0123
#define LINUX_REBOOT_CMD_CAD_ON 0x89ABCDEF
#define LINUX_REBOOT_CMD_CAD_OFF 0x00000000
#define LINUX_REBOOT_CMD_POWER_OFF 0x4321FEDC
#define LINUX_REBOOT_CMD_RESTART2 0xA1B2C3D4
#define LINUX_REBOOT_CMD_SW_SUSPEND 0xD000FCE2
#define LINUX_REBOOT_CMD_KEXEC 0x45584543
/*
* Commands accepted by the _reboot() system call.
*
* RESTART Restart system using default command and mode.
* HALT Stop OS and give system control to ROM monitor, if any.
* CAD_ON Ctrl-Alt-Del sequence causes RESTART command.
* CAD_OFF Ctrl-Alt-Del sequence sends SIGINT to init task.
* POWER_OFF Stop OS and remove all power from system, if possible.
* RESTART2 Restart system using given command string.
* SW_SUSPEND Suspend system using software suspend if compiled in.
* KEXEC Restart system using a previously loaded Linux kernel
*/
#define LINUX_REBOOT_CMD_RESTART 0x01234567
#define LINUX_REBOOT_CMD_HALT 0xCDEF0123
#define LINUX_REBOOT_CMD_CAD_ON 0x89ABCDEF
#define LINUX_REBOOT_CMD_CAD_OFF 0x00000000
#define LINUX_REBOOT_CMD_POWER_OFF 0x4321FEDC
#define LINUX_REBOOT_CMD_RESTART2 0xA1B2C3D4
#define LINUX_REBOOT_CMD_SW_SUSPEND 0xD000FCE2
#define LINUX_REBOOT_CMD_KEXEC 0x45584543
註釋中的說明很詳細瞭,比較陌生的就是關於CAD,其實就是用來想用Ctrl+Alt+Del操作的;然後SW_SYSPEND是軟件休眠;KEXEC就太高端瞭,屬於內核的一個補丁,用來利用老內核重啟,詳細資料:http://www.ibm.com/developerworks/cn/linux/l-kexec/?ca=dwcn-newsletter-linux
以上這些隻有前六個命令被Android系統所使用,為什麼這麼說,可以去看bionic/libc/include/sys/reboot.h,上邊已經貼出瞭。LINUX_REBOOT_CMD_HALT雖有定義,但是也沒有發現Android系統中哪裡有調用,有高手找到的話,希望能夠告知一下。最終的最終,能夠用到的就隻有三個:
RESTART
POWER_OFF
RESTART2
10.最終實現
重啟調用的是kernel_restart,區別是參數是不是空,關機則調用kernel_power_off(),先看關機:
[cpp]
/**
* kernel_power_off – power_off the system
*
* Shutdown everything and perform a clean system power_off.
*/
void kernel_power_off(void)
{
kernel_shutdown_prepare(SYSTEM_POWER_OFF);
if (pm_power_off_prepare)
pm_power_off_prepare();
disable_nonboot_cpus();
syscore_shutdown();
printk(KERN_EMERG "Power down.\n");
kmsg_dump(KMSG_DUMP_POWEROFF);
machine_power_off();
}
EXPORT_SYMBOL_GPL(kernel_power_off);
/**
* kernel_power_off – power_off the system
*
* Shutdown everything and perform a clean system power_off.
*/
void kernel_power_off(void)
{
kernel_shutdown_prepare(SYSTEM_POWER_OFF);
if (pm_power_off_prepare)
pm_power_off_prepare();
disable_nonboot_cpus();
syscore_shutdown();
printk(KERN_EMERG "Power down.\n");
kmsg_dump(KMSG_DUMP_POWEROFF);
machine_power_off();
}
EXPORT_SYMBOL_GPL(kernel_power_off);
最瞭一系列準備工作,最終調用machine_power_off():
[cpp]
void machine_power_off(void)
{
machine_shutdown();
if (pm_power_off)
pm_power_off();
}
void machine_power_off(void)
{
machine_shutdown();
if (pm_power_off)
pm_power_off();
}
之前找尋的pm_power_off在這裡就有用處瞭,是關機的最後一步操作。關機完成,之後看下重啟操作:
[cpp]
/**
* kernel_restart – reboot the system
* @cmd: pointer to buffer containing command to execute for restart
* or %NULL
*
* Shutdown everything and perform a clean reboot.
* This is not safe to call in interrupt context.
*/
void kernel_restart(char *cmd)
{
kernel_restart_prepare(cmd);
if (!cmd)
printk(KERN_EMERG "Restarting system.\n");
else
printk(KERN_EMERG "Restarting system with command '%s'.\n", cmd);
kmsg_dump(KMSG_DUMP_RESTART);
machine_restart(cmd);
}
EXPORT_SYMBOL_GPL(kernel_restart);
/**
* kernel_restart – reboot the system
* @cmd: pointer to buffer containing command to execute for restart
* or %NULL
*
* Shutdown everything and perform a clean reboot.
* This is not safe to call in interrupt context.
*/
void kernel_restart(char *cmd)
{
kernel_restart_prepare(cmd);
if (!cmd)
printk(KERN_EMERG "Restarting system.\n");
else
printk(KERN_EMERG "Restarting system with command '%s'.\n", cmd);
kmsg_dump(KMSG_DUMP_RESTART);
machine_restart(cmd);
}
EXPORT_SYMBOL_GPL(kernel_restart);
同樣的套路,也是會進行一些準備工作,之後調用machine_restart(cmd), 如果是普通重啟,那麼中個cmd就為NULL,如果是特殊重啟,那麼這個cmd就是一層一層傳遞下來得那個arg瞭。
[cpp]
void machine_restart(char *cmd)
{
machine_shutdown();
arm_pm_restart(reboot_mode, cmd);
}
…
void (*arm_pm_restart)(char str, const char *cmd) = arm_machine_restart;
EXPORT_SYMBOL_GPL(arm_pm_restart);
void machine_restart(char *cmd)
{
machine_shutdown();
arm_pm_restart(reboot_mode, cmd);
}
…
void (*arm_pm_restart)(char str, const char *cmd) = arm_machine_restart;
EXPORT_SYMBOL_GPL(arm_pm_restart);
而還記得剛才的pm2.c嗎?在那裡同樣對arm_pm_restart進行瞭指針賦值:
[cpp]
arm_pm_restart = msm_pm_restart;
arm_pm_restart = msm_pm_restart;
賦值的函數為msm_pm_init, 其調用為
[cpp]
late_initcall_sync(msm_pm_init);
late_initcall_sync(msm_pm_init);
late_initcall_sync的啟動優先級是最低的,為7。module_init其實是6的優先級,數字越大優先級越低。所以,這樣推斷的話,最終arm_pm_restart這個函數指針會指向msm_pm_restart。關於msm_pm_restart的具體實現也不細看瞭,跟前邊說的一樣,都是各傢不一樣,就幾行代碼:
[cpp]
static void msm_pm_restart(char str, const char *cmd)
{
msm_rpcrouter_close();
msm_proc_comm(PCOM_RESET_CHIP, &restart_reason, 0);
for (;;)
;
}
static void msm_pm_restart(char str, const char *cmd)
{
msm_rpcrouter_close();
msm_proc_comm(PCOM_RESET_CHIP, &restart_reason, 0);
for (;;)
;
}
但是細心的朋友可能會發現這裡有一個restart_reason,這個並不是傳遞下來的參數。事實上,這個值已經在之前kernel_restart_prepare(cmd)的時候就已經設置好瞭。
[cpp] v
void kernel_restart_prepare(char *cmd)
{
blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
system_state = SYSTEM_RESTART;
usermodehelper_disable();
device_shutdown();
syscore_shutdown();
}
void kernel_restart_prepare(char *cmd)
{
blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
system_state = SYSTEM_RESTART;
usermodehelper_disable();
device_shutdown();
syscore_shutdown();
}
就是blocking_notifier機制,這個操作在之前的shutdown關機操作中也有,且是同一個list,都是reboot_notifier_list。也很容易理解,就是將註冊在reboot_notifier_list上的函數傳入相關參數後執行,作為瞭解,看一下具體是怎麼使用的:(arch/arm/mach-msm/pm2.c)
[cpp]
static int msm_reboot_call
(struct notifier_block *this, unsigned long code, void *_cmd)
{
if ((code == SYS_RESTART) && _cmd) {
char *cmd = _cmd;
if (!strcmp(cmd, "bootloader")) {
restart_reason = 0x77665500;
} else if (!strcmp(cmd, "recovery")) {
restart_reason = 0x77665502;
} else if (!strcmp(cmd, "eraseflash")) {
restart_reason = 0x776655EF;
} else if (!strncmp(cmd, "oem-", 4)) {
unsigned code = simple_strtoul(cmd + 4, 0, 16) & 0xff;
restart_reason = 0x6f656d00 | code;
} else {
restart_reason = 0x77665501;
}
}
return NOTIFY_DONE;
}
static struct notifier_block msm_reboot_notifier = {
.notifier_call = msm_reboot_call,
};
…
static int __init msm_pm_init(void)
{
…
register_reboot_notifier(&msm_reboot_notifier);
…
}
static int msm_reboot_call
(struct notifier_block *this, unsigned long code, void *_cmd)
{
if ((code == SYS_RESTART) && _cmd) {
char *cmd = _cmd;
if (!strcmp(cmd, "bootloader")) {
restart_reason = 0x77665500;
} else if (!strcmp(cmd, "recovery")) {
restart_reason = 0x77665502;
} else if (!strcmp(cmd, "eraseflash")) {
restart_reason = 0x776655EF;
} else if (!strncmp(cmd, "oem-", 4)) {
unsigned code = simple_strtoul(cmd + 4, 0, 16) & 0xff;
restart_reason = 0x6f656d00 | code;
} else {
restart_reason = 0x77665501;
}
}
return NOTIFY_DONE;
}
static struct notifier_block msm_reboot_notifier = {
.notifier_call = msm_reboot_call,
};
…
static int __init msm_pm_init(void)
{
…
register_reboot_notifier(&msm_reboot_notifier);
…
}
OK,萬事大吉,在kernel_restart_prepare的時候msm_reboot_call會被首先調用,這個函數的作用就是根據用戶命令給restart_reason賦值,從而在之後調用msm_pm_restart的時候使用。這裡我們發現在reboot的時候可以帶的參數不僅有recovery,bootloader,還有eraseflash和oem-???,字面上看應該是用來擦除ROM和解鎖之類的操作瞭。
關機怎麼用?
本文的分析是由Android給出的reboot接口開始的,但是分析來分析去,回頭想一想會發現,Android給出的接口reboot就真的隻能重啟而已,不能進行關機操作,可以在跟蹤這個流程的過程中會發現,確實是有存在關機的相關接口的。那麼關機該怎麼用呢?
frameworks/base/services/java/com/android/serverBatteryService.java
[java]
private final void shutdownIfNoPower() {
// shut down gracefully if our battery is critically low and we are not powered.
// wait until the system has booted before attempting to display the shutdown dialog.
if (mBatteryLevel == 0 && !isPowered() && ActivityManagerNative.isSystemReady()) {
Intent intent = new Intent(Intent.ACTION_REQUEST_SHUTDOWN);
intent.putExtra(Intent.EXTRA_KEY_CONFIRM, false);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
mContext.startActivity(intent);
}
private final void shutdownIfNoPower() {
// shut down gracefully if our battery is critically low and we are not powered.
// wait until the system has booted before attempting to display the shutdown dialog.
if (mBatteryLevel == 0 && !isPowered() && ActivityManagerNative.isSystemReady()) {
Intent intent = new Intent(Intent.ACTION_REQUEST_SHUTDOWN);
intent.putExtra(Intent.EXTRA_KEY_CONFIRM, false);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
mContext.startActivity(intent);
}
}
這樣就可以瞭,不用多說瞭吧。