Android开机流程跟踪

./core/rootdir/init.trace.rc

./core/rootdir/init.zygote64_32.rc

./core/rootdir/init.rc

./core/rootdir/init.zygote64.rc

./core/rootdir/init.zygote32.rc

./core/rootdir/init.zygote32_64.rc

servicezygote/system/bin/app_process64-Xzygote/system/bin--zygote--start-system-server--socket-name=zygote

classmain

socketzygotestream660rootsystem

onrestartwrite/sys/android_power/request_statewake

onrestartwrite/sys/power/stateon

onrestartrestartmedia

onrestartrestartnetd

intmain(intargc,char*constargv[])

{

//Parseruntimearguments.Stopatfirstunrecognizedoption.

//这里解析参数配置信息确定zygote以及nicename等参数

boolzygote=false;

boolstartSystemServer=false;

boolapplication=false;

String8niceName;

String8className;

++i;//Skipunused"parentdir"argument.

while(i<argc){

constchar*arg=argv[i++];

if(strcmp(arg,"--zygote")==0){

zygote=true;

niceName=ZYGOTE_NICE_NAME;

}elseif(strcmp(arg,"--start-system-server")==0){

startSystemServer=true;

}elseif(strcmp(arg,"--application")==0){

application=true;

}elseif(strncmp(arg,"--nice-name=",12)==0){

niceName.setTo(arg+12);

}elseif(strncmp(arg,"--",2)!=0){

className.setTo(arg);

break;

}else{

--i;

break;

}

}

......

//这里设置processname从配置信息我们可以看到，processname为zygote

if(!niceName.isEmpty()){

runtime.setArgv0(niceName.string());

set_process_name(niceName.string());

}

if(zygote){

runtime.start("com.android.internal.os.ZygoteInit",args);

}elseif(className){

runtime.start("com.android.internal.os.RuntimeInit",args);

}else{

//参数配置错误

}

}

/*

*StarttheAndroidruntime.Thisinvolvesstartingthevirtualmachine

*andcallingthe"staticvoidmain(String[]args)"methodintheclass

*namedby"className".

*

*Passesthemainfunctiontwoarguments,theclassnameandthespecified

*optionsstring.

*/

voidAndroidRuntime::start(constchar*className,constVector<String8>&options)

{

staticconstString8startSystemServer("start-system-server");

......

constchar*rootDir=getenv("ANDROID_ROOT");

if(rootDir==NULL){

rootDir="/system";

if(!hasDir("/system")){

LOG_FATAL("Norootdirectoryspecified,and/androiddoesnotexist.");

return;

}

setenv("ANDROID_ROOT",rootDir,1);

}

//constchar*kernelHack=getenv("LD_ASSUME_KERNEL");

//ALOGD("FoundLD_ASSUME_KERNEL='%s'\n",kernelHack);

/*startthevirtualmachine*/

JniInvocationjni_invocation;

jni_invocation.Init(NULL);

JNIEnv*env;

if(startVm(&mJavaVM,&env)!=0){

return;

}

onVmCreated(env);

/*

*Registerandroidfunctions.

*/

if(startReg(env)<0){

ALOGE("Unabletoregisterallandroidnatives\n");

return;

}

/*

*StartVM.ThisthreadbecomesthemainthreadoftheVM,andwill

*notreturnuntiltheVMexits.

*/

char*slashClassName=toSlashClassName(className);

jclassstartClass=env->FindClass(slashClassName);

if(startClass==NULL){

ALOGE("JavaVMunabletolocateclass'%s'\n",slashClassName);

/*keepgoing*/

}else{

jmethodIDstartMeth=env->GetStaticMethodID(startClass,"main",

"([Ljava/lang/String;)V");

if(startMeth==NULL){

ALOGE("JavaVMunabletofindmain()in'%s'\n",className);

/*keepgoing*/

}else{

env->CallStaticVoidMethod(startClass,startMeth,strArray);

#if0

if(env->ExceptionCheck())

threadExitUncaughtException(env);

#endif

}

}

free(slashClassName);

}

//fulairy

publicstaticvoidmain(Stringargv[]){

try{

......

booleanstartSystemServer=false;

StringsocketName="zygote";

StringabiList=null;

for(inti=1;i<argv.length;i++){

if("start-system-server".equals(argv[i])){

startSystemServer=true;

}elseif(argv[i].startsWith(ABI_LIST_ARG)){

abiList=argv[i].substring(ABI_LIST_ARG.length());

}elseif(argv[i].startsWith(SOCKET_NAME_ARG)){//SOCKET_NAME_ARG=--socket-name=

socketName=argv[i].substring(SOCKET_NAME_ARG.length());

}else{

thrownewRuntimeException("Unknowncommandlineargument:"+argv[i]);

}

}

if(abiList==null){

thrownewRuntimeException("NoABIlistsupplied.");

}

注册socket监听

registerZygoteSocket(socketName);

加载资源文件

preload();加载资源class，resource,libraryetc

触发垃圾回收

//Doaninitialgctocleanupafterstartup

gc();

if(startSystemServer){

startSystemServer(abiList,socketName);

}

runSelectLoop(abiList);

closeServerSocket();

}catch(MethodAndArgsCallercaller){

		//MethodAndArgsCaller异常很重要

caller.run();

}catch(RuntimeExceptionex){

Log.e(TAG,"Zygotediedwithexception",ex);

closeServerSocket();

throwex;

}

}

/**

*Preparetheargumentsandforkforthesystemserverprocess.

*/

privatestaticbooleanstartSystemServer(StringabiList,StringsocketName)

throwsMethodAndArgsCaller,RuntimeException{

longcapabilities=posixCapabilitiesAsBits(

OsConstants.CAP_BLOCK_SUSPEND,

OsConstants.CAP_KILL,

OsConstants.CAP_NET_ADMIN,

OsConstants.CAP_NET_BIND_SERVICE,

OsConstants.CAP_NET_BROADCAST,

OsConstants.CAP_NET_RAW,

OsConstants.CAP_SYS_MODULE,

OsConstants.CAP_SYS_NICE,

OsConstants.CAP_SYS_RESOURCE,

OsConstants.CAP_SYS_TIME,

OsConstants.CAP_SYS_TTY_CONFIG

);

/*Hardcodedcommandlinetostartthesystemserver*/

Stringargs[]={

"--setuid=1000",

"--setgid=1000",

"--setgroups=1001,1002,1003,1004,1005,1006,1007,1008,1009,1010,1018,1032,3001,3002,3003,3006,3007",

"--capabilities="+capabilities+","+capabilities,

"--runtime-init",

"--nice-name=system_server",

"com.android.server.SystemServer",

};

ZygoteConnection.ArgumentsparsedArgs=null;

intpid;

try{

//这里将参数封装为ZygoteConnection.Arguments参数类型

parsedArgs=newZygoteConnection.Arguments(args);

ZygoteConnection.applyDebuggerSystemProperty(parsedArgs);

ZygoteConnection.applyInvokeWithSystemProperty(parsedArgs);

/*Requesttoforkthesystemserverprocess*/

//为啥不直接把parsedArgs传递过去就完了....因为需要传递的信息只需要一部分，保证了程序安全性。

pid=Zygote.forkSystemServer(

parsedArgs.uid,parsedArgs.gid,

parsedArgs.gids,

parsedArgs.debugFlags,

null,

parsedArgs.permittedCapabilities,

parsedArgs.effectiveCapabilities);

}catch(IllegalArgumentExceptionex){

thrownewRuntimeException(ex);

}

/*Forchildprocess*/

if(pid==0){

if(hasSecondZygote(abiList)){

waitForSecondaryZygote(socketName);

}

handleSystemServerProcess(parsedArgs);

}

returntrue;

}

/**

*Finishremainingworkforthenewlyforkedsystemserverprocess.

*/

privatestaticvoidhandleSystemServerProcess(

ZygoteConnection.ArgumentsparsedArgs)

throwsZygoteInit.MethodAndArgsCaller{

if(parsedArgs.invokeWith!=null){

......

}else{

ClassLoadercl=null;

if(systemServerClasspath!=null){

cl=newPathClassLoader(systemServerClasspath,ClassLoader.getSystemClassLoader());

Thread.currentThread().setContextClassLoader(cl);

}

/*

*PasstheremainingargumentstoSystemServer.

*/

RuntimeInit.zygoteInit(parsedArgs.targetSdkVersion,parsedArgs.remainingArgs,cl);

}

/*shouldneverreachhere*/

}

/**

*Themainfunctioncalledwhenstartedthroughthezygoteprocess.This

*couldbeunifiedwithmain(),ifthenativecodeinnativeFinishInit()

*wererationalizedwithZygotestartup.<p>

*

*Currentrecognizedargs:

*<ul>

*<li><code>[--]<startclassname><args>

*</ul>

*

*@paramtargetSdkVersiontargetSDKversion

*@paramargvargstrings

*/

publicstaticfinalvoidzygoteInit(inttargetSdkVersion,String[]argv,ClassLoaderclassLoader)

throwsZygoteInit.MethodAndArgsCaller{

if(DEBUG)Slog.d(TAG,"RuntimeInit:Startingapplicationfromzygote");

redirectLogStreams();//aboutprintandroidlog

commonInit();//包含uncaughtexception，timezone，logmanager，HTTPuserAgent，NetworkManagementSocketTagger

nativeZygoteInit();//nativeinit

applicationInit(targetSdkVersion,argv,classLoader);

}

privatestaticvoidapplicationInit(inttargetSdkVersion,String[]argv,ClassLoaderclassLoader)

throwsZygoteInit.MethodAndArgsCaller{

//IftheapplicationcallsSystem.exit(),terminatetheprocess

//immediatelywithoutrunninganyshutdownhooks.Itisnotpossibleto

//shutdownanAndroidapplicationgracefully.Amongotherthings,the

//AndroidruntimeshutdownhooksclosetheBinderdriver,whichcancause

//leftoverrunningthreadstocrashbeforetheprocessactuallyexits.

nativeSetExitWithoutCleanup(true);

//Wewanttobefairlyaggressiveaboutheaputilization,toavoid

//holdingontoalotofmemorythatisn'tneeded.

VMRuntime.getRuntime().setTargetHeapUtilization(0.75f);

VMRuntime.getRuntime().setTargetSdkVersion(targetSdkVersion);//之前的版本好像没有这个方法，应该是5.1中新增，设置sdk版本

finalArgumentsargs;

try{

args=newArguments(argv);

}catch(IllegalArgumentExceptionex){

Slog.e(TAG,ex.getMessage());

//lettheprocessexit

return;

}

//Remainingargumentsarepassedtothestartclass'sstaticmain

接下来有invokeStaticMain方法

invokeStaticMain(args.startClass,args.startArgs,classLoader);

}

/**

*Invokesastatic"main(argv[])methodonclass"className".

*ConvertsvariousfailingexceptionsintoRuntimeExceptions,with

*theassumptionthattheywillthencausetheVMinstancetoexit.

*

*@paramclassNameFully-qualifiedclassname

*@paramargvArgumentvectorformain()

*@paramclassLoadertheclassLoadertoload{@className}with

*/

privatestaticvoidinvokeStaticMain(StringclassName,String[]argv,ClassLoaderclassLoader)

throwsZygoteInit.MethodAndArgsCaller{

Class<?>cl;

try{

cl=Class.forName(className,true,classLoader);

}catch(ClassNotFoundExceptionex){

thrownewRuntimeException(

"Missingclasswheninvokingstaticmain"+className,

ex);

}

Methodm;

try{

m=cl.getMethod("main",newClass[]{String[].class});

}catch(NoSuchMethodExceptionex){

thrownewRuntimeException(

"Missingstaticmainon"+className,ex);

}catch(SecurityExceptionex){

thrownewRuntimeException(

"Problemgettingstaticmainon"+className,ex);

}

intmodifiers=m.getModifiers();

if(!(Modifier.isStatic(modifiers)&&Modifier.isPublic(modifiers))){

thrownewRuntimeException(

"Mainmethodisnotpublicandstaticon"+className);

}

/*

*ThisthrowgetscaughtinZygoteInit.main(),whichresponds

*byinvokingtheexception'srun()method.Thisarrangement

*clearsupallthestackframesthatwererequiredinsetting

*uptheprocess.

*/

thrownewZygoteInit.MethodAndArgsCaller(m,argv);

}

/**

*Themainentrypointfromzygote.

*/

publicstaticvoidmain(String[]args){

newSystemServer().run();

}