【专题】Android 启动流程相关
适用平台：MTK
文章内容包括Android启动流程相关知识。
Android 开机启动流程可以分为三个部分，硬件启动，内核启动，Android启动。
硬件启动包括了
Pre-Loader，UBOOT
内核启动
linux kernel
Android启动
init
services
zygote
system server
server manager
home launcher
1 首先来看 内核启动
文件<project root path>/kernel/init/main.c
内核进程寻找并启动init进程。
init进程是linux kernel起来之后启动的第一个用户进程，执行了目录创建挂载、rc文件解析执行、环境设置、启动服务、socket监听等动作。
USER PID PPID VSIZE RSS WCHAN PC NAME
root 1 0 924 568 c018b9f4 0001c040 S /init
2 再来看Android 启动
/system/bin/servicemanager 启动
路径:frameworks/base/cmds/servicemanager/service_manager.c
int main(int argc, char **argv)
{
struct binder_state *bs;
void *svcmgr = BINDER_SERVICE_MANAGER;
bs = binder_open(128*1024);
if (binder_become_context_manager(bs)) {
ALOGE("cannot become context manager (%s)\n", strerror(errno));
return -1;
}
svcmgr_handle = svcmgr;
binder_loop(bs, svcmgr_handler);
return 0;
}
Zygote启动
路径:frameworks/base/cmds/system_server/app_process/app_main.cpp
int main( ){
AppRuntime runtime;
if (zygote) {
runtime.start("com.android.internal.os.ZygoteInit", startSystemServer ? "start-system-server" : "");
}
}
class AppRuntime : public AndroidRuntime{}
zygoteInit
路径:frameworks\base\core\java\com\android\internal\os\ZygoteInit.java
public static void main(String argv[]) {
if (argv[1].equals("start-system-server")) {
startSystemServer();
} else if (!argv[1].equals("")) {
throw new RuntimeException(argv[0] + USAGE_STRING);
}
}
SystemServer
路径：frameworks\base\services\java\com\android\server\SystemServer.java
public static void main(String[] args) {
System.loadLibrary("android_servers");
init1(args);
}
native public static void init1(String[] args);
init1()
路径：frameworks/base/services/jni/com_android_server_SystemServer.cpp
static void android_server_SystemServer_init1(JNIEnv* env, jobject clazz)
{
system_init();
}
/*
* JNI registration.
*/
static JNINativeMethod gMethods[] = {
/* name, signature, funcPtr */
{ "init1", "([Ljava/lang/String;)V", (void*) android_server_SystemServer_init1 },
};
system_init()
路径:frameworks/base/cmds/system_server/library/system_init.cpp
JNIEnv* env = runtime->getJNIEnv();
jclass clazz = env->FindClass("com/android/server/SystemServer");
jmethodID methodId = env->GetStaticMethodID(clazz, "init2", "()V");
env->CallStaticVoidMethod(clazz, methodId);
init2()
路径：frameworks\base\services\java\com\android\server\SystemServer.java
wm = WindowManagerService.main(context, power, display, inputManager, uiHandler, wmHandler, factoryTest != SystemServer.FACTORY_TEST_LOW_LEVEL, !firstBoot, onlyCore); ActivityManagerService.self().setWindowManager(wm); ActivityManagerService.self().systemReady(...);
systemReady()
路径: 路径: frameworks/base/services/java/com/android/server/am/ActivityManagerService.java
public void systemReady(final Runnable goingCallback) {
mMainStack. resumeTopActivityLocked(null);
}
Home Launcher 启动
resumeTopActivityLocked()
路径:frameworks/base/services/java/com/android/server/am/ActivityStack.java
final boolean resumeTopActivityLocked(ActivityRecord prev, Bundle options) {
mService.startHomeActivityLocked(0);
}
startHomeActivityLocked()
路径:frameworks/base/services/java/com/android/server/am/ActivityManagerService.java
boolean startHomeActivityLocked(int userId) {
Intent intent = new Intent(mTopAction, mTopData != null ? Uri.parse(mTopData) : null);
....
intent.setFlags(intent.getFlags() | Intent.FLAG_ACTIVITY_NEW_TASK);
mMainStack.startActivityLocked(null, intent, null, aInfo, null, null, 0, 0, 0, 0, null, false, null);
}