zygote启动systemserver流程
作者：互联网
涉及代码路径：
\frameworks\base\cmds\app_process\app_main.cpp
\frameworks\base\core\jni\AndroidRuntime.cpp
\frameworks\base\core\java\com\android\internal\os\ZygoteInit.java
\frameworks\base\core\java\com\android\internal\os\ZygoteConnection.java
\frameworks\base\core\java\com\android\internal\os\Zygote.java
\frameworks\base\core\java\com\android\internal\os\RuntimeInit.java
1、zygote启动：
app_main.cpp中main函数如下：
初始化appruntime
AppRuntime runtime(argv[0], computeArgBlockSize(argc, argv));
其中：
class AppRuntime : public AndroidRuntime
解析参数中是否包含–zygote和–start-system-server
while (i < argc) {
const char* arg = argv[i++];
if (strcmp(arg, "--zygote") == 0) {
zygote = true;
niceName = ZYGOTE_NICE_NAME;
} else if (strcmp(arg, "--start-system-server") == 0) {
startSystemServer = true;
} else if (strcmp(arg, "--application") == 0) {
application = true;
} else if (strncmp(arg, "--nice-name=", 12) == 0) {
niceName.setTo(arg + 12);
} else if (strncmp(arg, "--", 2) != 0) {
className.setTo(arg);
break;
} else {
--i;
break;
}
}
runtime只是类名，args添加application字段
args.add(application ? String8("application") : String8("tool"));
runtime.setClassNameAndArgs(className, argc - i, argv + i);
添加参数start-system-server
if (startSystemServer) {
args.add(String8("start-system-server"));
}
调用对应的类名中的main函数，在androidruntime类的start方法中，首先分析ZygoteInit
if (zygote) {
runtime.start("com.android.internal.os.ZygoteInit", args, zygote);
} else if (className) {
runtime.start("com.android.internal.os.RuntimeInit", args, zygote);
} else {
fprintf(stderr, "Error: no class name or --zygote supplied.\n");
app_usage();
LOG_ALWAYS_FATAL("app_process: no class name or --zygote supplied.");
return 10;
}
2、AndroidRuntime
AndroidRuntime中start方法如下：
启动虚拟机：
JniInvocation jni_invocation;
jni_invocation.Init(NULL);
JNIEnv* env;
if (startVm(&mJavaVM, &env, zygote) != 0) {
return;
}
onVmCreated(env);
注册android方法：
if (startReg(env) < 0) {
ALOGE("Unable to register all android natives\n");
return;
}
从传入的参数中获取类名，并且调用该类中的main方法：
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
}
传入的是com.android.internal.os.ZygoteInit，接下来进入到ZygoteInit
3、ZygoteInit
ZygoteInit中main方法如下：
registerZygoteSocket(socketName); //注册socket
preload(); //预加载
预加载按顺序为：1、安装ICU cache reference pinning，2、加载类，3、加载资源，4、加载OpenGL资源，5、加载共享库，6、加载text资源，7、准备webview环境，8、使能ICU cache reference pinning，9、安装AndroidKeyStoreProvider
static void preload() {
Log.d(TAG, "begin preload");
Trace.traceBegin(Trace.TRACE_TAG_DALVIK, "BeginIcuCachePinning");
beginIcuCachePinning();
Trace.traceEnd(Trace.TRACE_TAG_DALVIK);
Trace.traceBegin(Trace.TRACE_TAG_DALVIK, "PreloadClasses");
preloadClasses();
Trace.traceEnd(Trace.TRACE_TAG_DALVIK);
Trace.traceBegin(Trace.TRACE_TAG_DALVIK, "PreloadResources");
preloadResources();
Trace.traceEnd(Trace.TRACE_TAG_DALVIK);
Trace.traceBegin(Trace.TRACE_TAG_DALVIK, "PreloadOpenGL");
preloadOpenGL();
Trace.traceEnd(Trace.TRACE_TAG_DALVIK);
preloadSharedLibraries();
preloadTextResources();
// Ask the WebViewFactory to do any initialization that must run in the zygote process,
// for memory sharing purposes.
WebViewFactory.prepareWebViewInZygote();
endIcuCachePinning();
warmUpJcaProviders();
Log.d(TAG, "end preload");
}
启动systemserver进入android世界
if (startSystemServer) {
startSystemServer(abiList, socketName);
}
private static boolean startSystemServer(String abiList, String socketName)
throws MethodAndArgsCaller, RuntimeException {
String args[] = {
"--setuid=1000",
"--setgid=1000",
"--setgroups=1001,1002,1003,1004,1005,1006,1007,1008,1009,1010,1018, 1021,1032,3001,3002,3003,3006,3007,3009,3010",
"--capabilities=" + capabilities + "," + capabilities,
"--nice-name=system_server",
"--runtime-args",
"com.android.server.SystemServer",
};
解析参数，创建子systemserver子进程。
try {
parsedArgs = new ZygoteConnection.Arguments(args);
ZygoteConnection.applyDebuggerSystemProperty(parsedArgs);
ZygoteConnection.applyInvokeWithSystemProperty(parsedArgs);
/* Request to fork the system server process */
pid = Zygote.forkSystemServer(
parsedArgs.uid, parsedArgs.gid,
parsedArgs.gids,
parsedArgs.debugFlags,
null,
parsedArgs.permittedCapabilities,
parsedArgs.effectiveCapabilities);
} catch (IllegalArgumentException ex) {
throw new RuntimeException(ex);
}
子进程创建成功后处理子进程
private static Runnable handleSystemServerProcess(ZygoteConnection.Arguments parsedArgs) {
// set umask to 0077 so new files and directories will default to owner-only permissions.
Os.umask(S_IRWXG | S_IRWXO);
//...... 对几个系统路径的jar文件做odex操作
if (parsedArgs.invokeWith != null) {
// 由上可知parsedArgs.invokeWith为空,此处不会进入
} else {
ClassLoader cl = null;
if (systemServerClasspath != null) {
cl = createPathClassLoader(systemServerClasspath, parsedArgs.targetSdkVersion);
Thread.currentThread().setContextClassLoader(cl);
}
/*
* Pass the remaining arguments to SystemServer.
*/
return ZygoteInit.zygoteInit(parsedArgs.targetSdkVersion, parsedArgs.remainingArgs, cl);
}
/* should never reach here */
}
public static final Runnable zygoteInit(int targetSdkVersion, String[] argv, ClassLoader classLoader) {
RuntimeInit.redirectLogStreams(); //重定向logstream
RuntimeInit.commonInit(); //常规内容初始化，比如bindeath进程crash监听等
ZygoteInit.nativeZygoteInit();
return RuntimeInit.applicationInit(targetSdkVersion, argv, classLoader);
}
protected static Runnable applicationInit(int targetSdkVersion, String[] argv,
ClassLoader classLoader) {
nativeSetExitWithoutCleanup(true);
VMRuntime.getRuntime().setTargetHeapUtilization(0.75f);
VMRuntime.getRuntime().setTargetSdkVersion(targetSdkVersion);
final Arguments args = new Arguments(argv);
//此处的startClass就是：com.android.server.SystemServer
return findStaticMain(args.startClass, args.startArgs, classLoader);
}
protected static Runnable findStaticMain(String className, String[] argv,
ClassLoader classLoader) {
Class<?> cl;
try {
cl = Class.forName(className, true, classLoader);
} catch (ClassNotFoundException ex) {
}
Method m;
try {
m = cl.getMethod("main", new Class[] { String[].class });
} catch (NoSuchMethodException ex) {
} catch (SecurityException ex) {
}
// ......
return new MethodAndArgsCaller(m, argv);
}
之后进入到：E:\frameworks\base\services\java\com\android\server\SystemServer.java
的main方法中：
public static void main(String[] args) {
new SystemServer().run();
}
至此，从zygote到systemserver启动过程分析完成。
标签：Trace,流程,args,zygote,parsedArgs,main,android,systemserver 来源： https://blog.csdn.net/thh159/article/details/88426902