android L 启动流程
android启动流程文章已经概述了android的启动流程，而andoird 5.0的流程其实也差不多，少数不同而已。
如下图：
整个启动流程与之前的一样，唯一不同的是android L支持64位的app，所以又起一个Zygote64来专门负责64位APK的孵化。
而且创建Zygote进程脚本在init.zygoteXX.rc里。
如下：
system/core/rootdir/init.zygote64_32.rc system/core/rootdir/init.zygote64.rc system/core/rootdir/init.zygote32.rc system/core/rootdir/init.zygote32_64.rc
64位芯片通常会选择
system/core/rootdir/init.zygote64_32.rc
咱们来看下内容，分析创建了两个zygote。
service zygote /system/bin/app_process64 -Xzygote /system/bin --zygote --start-system-server --socket-name=zygote
class main
socket zygote stream 660 root system
onrestart write /sys/android_power/request_state wake
onrestart write /sys/power/state on
onrestart restart media
onrestart restart netd
service zygote_secondary /system/bin/app_process32 -Xzygote /system/bin --zygote --socket-name=zygote_secondary
class main
socket zygote_secondary stream 660 root system
onrestart restart zygote
言归正传：
1：Linux内核启动
2：init进程启动。
3：本地系统服务,Java系统服务 启动：
1)：init启动service manager，这个进程主要负责系统服务的注册管理，包括“java系统服务”“本地系统服务”
2)：init启动Media server，这个进程负责启动C/C++的“本地系统服务”。
3)：init启动Zygote,这个进程启动System server进程，这个进程启动"Java系统服务"－－－[包括power manager service,sensor service]
4)：另外init启动system/bin下面的各种守护进程
4：Home启动。
第一：Linux内核启动
....
第二：init进程启动
kernel/init/main.c
asmlinkage void __init start_kernel(void)//这是kernel的入口，汇编head-common.S会链过来。
{
...
/* Do the rest non-__init'ed, we're now alive */
rest_init();
}
static noinline void __init_refok rest_init(void)
{
...
kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND);
...
}
static int __ref kernel_init(void *unused)
{
kernel_init_freeable();//指定init文件位置，新增的函数，与之前的系统不同。
<span style="white-space:pre"> </span>...
if (ramdisk_execute_command) {
if (!run_init_process(ramdisk_execute_command))//调用run_init_process，init进程跑进来
return 0;
pr_err("Failed to execute %s\n", ramdisk_execute_command);
}
<span style="white-space:pre"> </span>....
}kernel_init_freeable()实现
static noinline void __init kernel_init_freeable(void)
{
...
if (!ramdisk_execute_command)
ramdisk_execute_command = "/init";//指定init文件位置
if (sys_access((const char __user *) ramdisk_execute_command, 0) != 0) {
ramdisk_execute_command = NULL;
prepare_namespace();
}
...
}
第三：启动servicemanager进程
init进程通过init.rc脚本启动servicemanager
init.rc
service servicemanager /system/bin/servicemanager//看到吧
class core
user system
group system
critical
onrestart restart healthd
onrestart restart zygote
onrestart restart media
onrestart restart surfaceflinger
onrestart restart drm下面是servicemanager部分代码，它负责管理本地系统服务和Java系统服务，为下面的本地系统系服，java系统服务的注册提供服务
frameworks/native/cmds/servicemanager/service_manager.c
uint32_t do_find_service(struct binder_state *bs, const uint16_t *s, size_t len, uid_t uid, pid_t spid)
{
}
int do_add_service(struct binder_state *bs,
const uint16_t *s, size_t len,
uint32_t handle, uid_t uid, int allow_isolated,
pid_t spid)
{
}
int main(int argc, char **argv)
{
struct binder_state *bs;
bs = binder_open(128*1024);
...
selinux_enabled = is_selinux_enabled();
sehandle = selinux_android_service_context_handle();//增加了selinux方面的内容
if (selinux_enabled > 0) {
if (sehandle == NULL) {
ALOGE("SELinux: Failed to acquire sehandle. Aborting.\n");
abort();
}
if (getcon(&service_manager_context) != 0) {
ALOGE("SELinux: Failed to acquire service_manager context. Aborting.\n");
abort();
}
}
union selinux_callback cb;
cb.func_audit = audit_callback;
selinux_set_callback(SELINUX_CB_AUDIT, cb);//很多地方都用到
cb.func_log = selinux_log_callback;
selinux_set_callback(SELINUX_CB_LOG, cb);
svcmgr_handle = BINDER_SERVICE_MANAGER;
binder_loop(bs, svcmgr_handler);
return 0;
}
从是上面知道servicemanager除了什么的service的注册服务外，还在SELinux安全领域做了工作，因为android L已经完全打开SELinux的功能。
init进程通过init.rc脚本启动mediaserver
init.rc
service media /system/bin/mediaserver//这样启动
class main
user media
group audio camera inet net_bt net_bt_admin net_bw_acct drmrpc mediadrm qcom_diag
ioprio rt 4
mediaserver启动一系统本地系统服务
frameworks/av/media/mediaserver/main_mediaserver.cpp
int main(int argc __unused, char** argv)
{
...
ALOGI("ServiceManager: %p", sm.get());
AudioFlinger::instantiate();//启动AudioFlinger服务
MediaPlayerService::instantiate();//启动MediaPlayerService服务
CameraService::instantiate();//启动CameraService服务
#ifdef AUDIO_LISTEN_ENABLED
ALOGI("ListenService instantiated");
ListenService::instantiate();
#endif
AudioPolicyService::instantiate();
SoundTriggerHwService::instantiate();
registerExtensions();
ProcessState::self()->startThreadPool();
IPCThreadState::self()->joinThreadPool();
}
}
init进程通过init.zygoteXX.rc启动zygote
前面讲到andoird L是64位系统，与之配合的芯片如果是64位的话，那init.zygoteXX.rc = init.zygote64_32.rc
service zygote /system/bin/app_process64 -Xzygote /system/bin --zygote --start-system-server --socket-name=zygote//zygote64通过app_process64进程启动
class main
socket zygote stream 660 root system
onrestart write /sys/android_power/request_state wake
onrestart write /sys/power/state on
onrestart restart media
onrestart restart netd
service zygote_secondary /system/bin/app_process32 -Xzygote /system/bin --zygote --socket-name=zygote_secondary//zygote通过app_process32进程启动
class main
socket zygote_secondary stream 660 root system
onrestart restart zygote分别通过app_process64,app_process32两个app_process进程来启动zygote64,zygote。
frameworks/base/cmds/app_process/app_main.cpp
#if defined(__LP64__)
static const char ABI_LIST_PROPERTY[] = "ro.product.cpu.abilist64";
static const char ZYGOTE_NICE_NAME[] = "zygote64";//64位zygote进程的名字
#else
static const char ABI_LIST_PROPERTY[] = "ro.product.cpu.abilist32";
static const char ZYGOTE_NICE_NAME[] = "zygote";
#endif
int main(int argc, char* const argv[])
{
...
while (i < argc) {
const char* arg = argv[i++];
if (strcmp(arg, "--zygote") == 0) {
zygote = true;
niceName = ZYGOTE_NICE_NAME;//根据64还是32，指定zygote进程的名字
} ...
}
...
if (!niceName.isEmpty()) {
runtime.setArgv0(niceName.string());
set_process_name(niceName.string());//设置进程名字
}
if (zygote) {
runtime.start("com.android.internal.os.ZygoteInit", args);//启动zygote进程
} ...
}
AndroidRuntime是android的运行环境，由于Dalvik VM的效率不高，在android4.4开始，google就开发了androidruntime即android运行环境。Dalvik下，应用每次运行，都要将字节码转成机器码，大大影响效率。ART不同，应用第一次安装的时候，字节码就会转成机器码，并保存起来，这样应用启动时就更快。
Zygote是Java编写的，需运行在AndroidRuntime上。
frameworks/base/core/jni/AndroidRuntime.cpp
void AndroidRuntime::start(const char* className, const Vector<String8>& options)
{
ALOGD("\n>>>>>> AndroidRuntime START %s <<<<<<\n",
className != NULL ? className : "(unknown)");
...
//下面就是启动java进程，调用了java中的main函数入口
/*
* Start VM. This thread becomes the main thread of the VM, and will
* not return until the VM exits.
*/
char* slashClassName = toSlashClassName(className);
jclass startClass = env->FindClass(slashClassName);
if (startClass == NULL) {
ALOGE("JavaVM unable to locate class '%s'\n", slashClassName);
/* keep going */
} else {
jmethodID startMeth = env->GetStaticMethodID(startClass, "main",
"([Ljava/lang/String;)V");
if (startMeth == NULL) {
ALOGE("JavaVM unable to find main() in '%s'\n", className);
/* keep going */
} else {
env->CallStaticVoidMethod(startClass, startMeth, strArray);
#if 0
if (env->ExceptionCheck())
threadExitUncaughtException(env);
#endif
}
}
free(slashClassName);
ALOGD("Shutting down VM\n");
if (mJavaVM->DetachCurrentThread() != JNI_OK)
ALOGW("Warning: unable to detach main thread\n");
if (mJavaVM->DestroyJavaVM() != 0)
ALOGW("Warning: VM did not shut down cleanly\n");
}
zygote启动system server
frameworks/base/core/java/com/android/internal/os/ZygoteInit.java
public static void main(String argv[]) {
try {
...
registerZygoteSocket(socketName);//注册listener接口
...
if (startSystemServer) {
startSystemServer(abiList, socketName);//启动system server
}
Log.i(TAG, "Accepting command socket connections");
runSelectLoop(abiList);
closeServerSocket();
} catch (MethodAndArgsCaller caller) {
caller.run();
} catch (RuntimeException ex) {
Log.e(TAG, "Zygote died with exception", ex);
closeServerSocket();
throw ex;
}
}
启动一系列Java系统服务
frameworks/base/services/java/com/android/server/SystemServer.java
public static void main(String[] args) {
new SystemServer().run();//调用run()
}
SystemServer的main函数直接调用run()
private void run() {
...
// Start services.
try {
startBootstrapServices();//启动一系列Java系统服务
startCoreServices();
startOtherServices();
} catch (Throwable ex) {
Slog.e("System", "******************************************");
Slog.e("System", "************ Failure starting system services", ex);
throw ex;
}
...
}
private void startOtherServices() {
...
Slog.i(TAG, "Content Manager");
contentService = ContentService.main(context,
mFactoryTestMode == FactoryTest.FACTORY_TEST_LOW_LEVEL);
Slog.i(TAG, "System Content Providers");
mActivityManagerService.installSystemProviders();
Slog.i(TAG, "Vibrator Service");
vibrator = new VibratorService(context);
ServiceManager.addService("vibrator", vibrator);
Slog.i(TAG, "Consumer IR Service");
consumerIr = new ConsumerIrService(context);
ServiceManager.addService(Context.CONSUMER_IR_SERVICE, consumerIr);
mAlarmManagerService = mSystemServiceManager.startService(AlarmManagerService.class);
alarm = IAlarmManager.Stub.asInterface(
ServiceManager.getService(Context.ALARM_SERVICE));
Slog.i(TAG, "Init Watchdog");
final Watchdog watchdog = Watchdog.getInstance();
watchdog.init(context, mActivityManagerService);
...
}
第四：Home启动
如下：
private void startOtherServices() {
...
mActivityManagerService.systemReady(new Runnable() {
@Override
public void run() {
...
}
});
...
}
来到ActivityManagerService
frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
public void systemReady(final Runnable goingCallback) {
synchronized(this) {
if (mSystemReady) {
// If we're done calling all the receivers, run the next "boot phase" passed in
// by the SystemServer
if (goingCallback != null) {
goingCallback.run();
}
return;
}
...
mStackSupervisor.resumeTopActivitiesLocked();//启动HomeActivity
sendUserSwitchBroadcastsLocked(-1, mCurrentUserId);
}
}
systemReady调用mStackSupervisor.resumeTopActivityesLocked启动HomeActivity
mStackSupervisor.resumeTopActivitiesLoked()实现
frameworks/base/services/core/java/com/android/server/am/ActivityStackSupervisor.java
boolean resumeTopActivitiesLocked() {
return resumeTopActivitiesLocked(null, null, null);
}
boolean resumeTopActivitiesLocked(ActivityStack targetStack, ActivityRecord target,
Bundle targetOptions) {
if (targetStack == null) {
targetStack = getFocusedStack();
}
// Do targetStack first.
boolean result = false;
if (isFrontStack(targetStack)) {
result = targetStack.resumeTopActivityLocked(target, targetOptions);
}
for (int displayNdx = mActivityDisplays.size() - 1; displayNdx >= 0; --displayNdx) {
final ArrayList<ActivityStack> stacks = mActivityDisplays.valueAt(displayNdx).mStacks;
for (int stackNdx = stacks.size() - 1; stackNdx >= 0; --stackNdx) {
final ActivityStack stack = stacks.get(stackNdx);
if (stack == targetStack) {
// Already started above.
continue;
}
if (isFrontStack(stack)) {
stack.resumeTopActivityLocked(null);//调用stack.resumeTopActivityLocked()
}
}
}
return result;
}
要调用stack.resumeTopActivityLocked()的条件是stacks.size() = 1;那会=1吗？当然会
因为systemserver进程调用了setWindowManager(wm)创建第一个ActivityStack,并且是HOMD_STACK
如下设置setWindowManager(wm)
frameworks/base/services/java/com/android/server/SystemServer.java
private void startOtherServices() {
...
mActivityManagerService.setWindowManager(wm);
...
}
mActivityManagerService.setWindowManager(wm)实现
frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
public void setWindowManager(WindowManagerService wm) {
mWindowManager = wm;
mStackSupervisor.setWindowManager(wm);//调用这里
}
mStackSupervisor.setWindowManager(wm)实现
frameworks/base/services/core/java/com/android/server/am/ActivityStackSupervisor.java
void setWindowManager(WindowManagerService wm) {
synchronized (mService) {
...
createStackOnDisplay(HOME_STACK_ID, Display.DEFAULT_DISPLAY);//创建HOME_STACK，与之前系统有所不同
mHomeStack = mFocusedStack = mLastFocusedStack = getStack(HOME_STACK_ID);
...
}
}
private int createStackOnDisplay(int stackId, int displayId) {
ActivityDisplay activityDisplay = mActivityDisplays.get(displayId);
if (activityDisplay == null) {
return -1;
}
ActivityContainer activityContainer = new ActivityContainer(stackId);
mActivityContainers.put(stackId, activityContainer);//将HOME_STACK放入Activitycontainer中
activityContainer.attachToDisplayLocked(activityDisplay);
return stackId;
}
所以说stack.size() = 1，并且是 launcher
而通过下面的getStack()函数获取HOME_STACK_ID
ActivityStack getStack(int stackId) {
ActivityContainer activityContainer = mActivityContainers.get(stackId);
if (activityContainer != null) {
return activityContainer.mStack;
}
return null;
}
回到刚才的函数
frameworks/base/services/core/java/com/android/server/am/ActivityStackSupervisor.java
boolean resumeTopActivitiesLocked(ActivityStack targetStack, ActivityRecord target,
Bundle targetOptions) {
.....
if (stack == targetStack) {
// Already started above.
continue;
}
if (isFrontStack(stack)) {
stack.resumeTopActivityLocked(null);//调用stack.resumeTopActivityLocked()
}
....
}
stack.resumeTopActivityLocked()实现
frameworks/base/services/core/java/com/android/server/am/ActivityStack.java
final boolean resumeTopActivityLocked(ActivityRecord prev) {
return resumeTopActivityLocked(prev, null);
}
final boolean resumeTopActivityLocked(ActivityRecord prev, Bundle options) {
...
result = resumeTopActivityInnerLocked(prev, options);
...
}
final boolean resumeTopActivityInnerLocked(ActivityRecord prev, Bundle options) {
...
final TaskRecord prevTask = prev != null ? prev.task : null;
if (next == null) {
// There are no more activities! Let's just start up the
// Launcher...
ActivityOptions.abort(options);
if (DEBUG_STATES) Slog.d(TAG, "resumeTopActivityLocked: No more activities go home");
if (DEBUG_STACK) mStackSupervisor.validateTopActivitiesLocked();
// Only resume home if on home display
final int returnTaskType = prevTask == null || !prevTask.isOverHomeStack() ?
HOME_ACTIVITY_TYPE : prevTask.getTaskToReturnTo();
return isOnHomeDisplay() &&
mStackSupervisor.resumeHomeStackTask(returnTaskType, prev);//调用
}
...
}
mStackSupervisor.resumeHomeStackTask()实现
frameworks/base/services/core/java/com/android/server/am/ActivityStackSupervisor.java
boolean resumeHomeStackTask(int homeStackTaskType, ActivityRecord prev) {
if (!mService.mBooting && !mService.mBooted) {
// Not ready yet!
return false;
}
if (homeStackTaskType == RECENTS_ACTIVITY_TYPE) {
mWindowManager.showRecentApps();
return false;
}
moveHomeStackTaskToTop(homeStackTaskType);
if (prev != null) {
prev.task.setTaskToReturnTo(APPLICATION_ACTIVITY_TYPE);
}
ActivityRecord r = mHomeStack.topRunningActivityLocked(null);
// if (r != null && (r.isHomeActivity() || r.isRecentsActivity())) {
if (r != null && r.isHomeActivity()) {
mService.setFocusedActivityLocked(r);
return resumeTopActivitiesLocked(mHomeStack, prev, null);
}
return mService.startHomeActivityLocked(mCurrentUser);//调用
}
由于prev =null, 而第一个应用Launcher还没跑起来，所以r = null
mService.startHomeActivityLocked()实现
frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
boolean startHomeActivityLocked(int userId) {
if (mFactoryTest == FactoryTest.FACTORY_TEST_LOW_LEVEL
&& mTopAction == null) {
// We are running in factory test mode, but unable to find
// the factory test app, so just sit around displaying the
// error message and don't try to start anything.
return false;
}
Intent intent = getHomeIntent();
ActivityInfo aInfo =
resolveActivityInfo(intent, STOCK_PM_FLAGS, userId);
if (aInfo != null) {
intent.setComponent(new ComponentName(
aInfo.applicationInfo.packageName, aInfo.name));
// Don't do this if the home app is currently being
// instrumented.
aInfo = new ActivityInfo(aInfo);
aInfo.applicationInfo = getAppInfoForUser(aInfo.applicationInfo, userId);
ProcessRecord app = getProcessRecordLocked(aInfo.processName,
aInfo.applicationInfo.uid, true);
if (app == null || app.instrumentationClass == null) {
intent.setFlags(intent.getFlags() | Intent.FLAG_ACTIVITY_NEW_TASK);
mStackSupervisor.startHomeActivity(intent, aInfo);
}
}
return true;
}
最后跑回到ActivityManagerService启动Home。
谢谢