Android 进阶——系统启动之SystemServer创建并启动Installer服务（八）

引言

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SystemServer进程在执行startBootstrapServices方法后，首先就通过SystemServiceManager创建和启动Installer系统服务。

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• Android 进阶——系统启动之BootLoader 简介及内核启动（一）
• Android 进阶——系统启动之Linux init进程的创建和启动（二）
• Android 进阶——系统启动之Android init进程的创建和启动（三）
• Android 进阶——系统启动之Android init.rc脚本解析（四）
• Android 进阶——系统启动之Android init进程解析init.rc脚本（五）
• Android 进阶——系统启动之Android进程造物者Zygote 进程启动详解（六）
• Android 进阶——系统启动之核心SystemServer进程启动详解（七）
• Android 进阶——系统启动之SystemServer创建并启动Installer服务（八）

一、Intsaller系统服务概述

\frameworks\base\services\core\java\com\android\server\pm\Installer.java继承自com.android.server.SystemService，同时持有installd守护进程对应Binder服务的代理对象，本质上就是通过Binder调用去与Linux底层installd守护进程通信完成真正的完成Apk文件格式的优化和转换、建立相关的数据目录、删除文件、安装应用等工作。因此在其他系统核心服务启动前首先被启动，

    private void startBootstrapServices() {
    
    
    	...
       Installer installer = mSystemServiceManager.startService(Installer.class);

当SystemServiceManager.startService(Installer.class)触发com.android.server.pm.Installer#onStart回调时，首先通过ServerManager获取名为installdBinder服务代理对象，然后调用这个Binder服务代理对象通过socket与Linux的installd 守护进程通信。

package com.android.server.pm;

import com.android.internal.os.BackgroundThread;
import com.android.server.SystemService;
public class Installer extends SystemService {
    
    
    private volatile IInstalld mInstalld;

    public Installer(Context context, boolean isolated) {
    
    
        super(context);
        mIsolated = isolated;
    }

    @Override
    public void onStart() {
    
    
        if (mIsolated) {
    
    
            mInstalld = null;
        } else {
    
    
            connect();
        }
    }

    private void connect() {
    
    
        IBinder binder = ServiceManager.getService("installd");
        if (binder != null) {
    
    
            try {
    
    
                binder.linkToDeath(new DeathRecipient() {
    
    
                    @Override
                    public void binderDied() {
    
    
                        Slog.w(TAG, "installd died; reconnecting");
                        connect();
                    }
                }, 0);
            }
        }

        if (binder != null) {
    
    
            mInstalld = IInstalld.Stub.asInterface(binder);
            try {
    
    
                invalidateMounts();
            }
        } else {
    
    
            Slog.w(TAG, "installd not found; trying again");
            BackgroundThread.getHandler().postDelayed(() -> {
    
    
                connect();
            }, DateUtils.SECOND_IN_MILLIS);
        }
    }
    public void dexopt(String apkPath, int uid, @Nullable String pkgName, String instructionSet,
            int dexoptNeeded, @Nullable String outputPath, int dexFlags,
            String compilerFilter, @Nullable String volumeUuid, @Nullable String sharedLibraries,
            @Nullable String seInfo, boolean downgrade, int targetSdkVersion,
            @Nullable String profileName, @Nullable String dexMetadataPath,
            @Nullable String compilationReason) throws InstallerException {
    
    
        if (!checkBeforeRemote()) return;
        try {
    
    
            mInstalld.dexopt(apkPath, uid, pkgName, instructionSet, dexoptNeeded, outputPath,
                    dexFlags, compilerFilter, volumeUuid, sharedLibraries, seInfo, downgrade,
                    targetSdkVersion, profileName, dexMetadataPath, compilationReason);
        }
    }
    public void rmdex(String codePath, String instructionSet) throws InstallerException {
    
    
        try {
    
    
            mInstalld.rmdex(codePath, instructionSet);
        }
    }
    public void createUserData(String uuid, int userId, int userSerial, int flags)
            throws InstallerException {
    
    
        if (!checkBeforeRemote()) return;
        try {
    
    
            mInstalld.createUserData(uuid, userId, userSerial, flags);
        }
    }
	...
    public void linkNativeLibraryDirectory(String uuid, String packageName, String nativeLibPath32,
            int userId) throws InstallerException {
    
    
        if (!checkBeforeRemote()) return;
        try {
    
    
            mInstalld.linkNativeLibraryDirectory(uuid, packageName, nativeLibPath32, userId);
        }
    }
    public void createOatDir(String oatDir, String dexInstructionSet)
            throws InstallerException {
    
    
        if (!checkBeforeRemote()) return;
        try {
    
    
            mInstalld.createOatDir(oatDir, dexInstructionSet);
        }
    }
    public void linkFile(String relativePath, String fromBase, String toBase)
            throws InstallerException {
    
    
        if (!checkBeforeRemote()) return;
        try {
    
    
            mInstalld.linkFile(relativePath, fromBase, toBase);
        }
    }
    public void deleteOdex(String apkPath, String instructionSet, String outputPath)
            throws InstallerException {
    
    
            mInstalld.deleteOdex(apkPath, instructionSet, outputPath);
    }
    public void installApkVerity(String filePath, FileDescriptor verityInput, int contentSize)
            throws InstallerException {
    
    
        if (!checkBeforeRemote()) return;
         mInstalld.installApkVerity(filePath, verityInput, contentSize);
    }
    public boolean reconcileSecondaryDexFile(String apkPath, String packageName, int uid,
            String[] isas, @Nullable String volumeUuid, int flags) throws InstallerException {
    
    
            return mInstalld.reconcileSecondaryDexFile(apkPath, packageName, uid, isas,
                    volumeUuid, flags);
    }

    public void invalidateMounts() throws InstallerException {
    
    
        if (!checkBeforeRemote()) return;
            mInstalld.invalidateMounts();
    }
    ...
}

二、com.android.server.SystemService概述

\frameworks\base\services\core\java\com\android\server\SystemService.java本质上就是对于一些运行在系统进程服务进行了抽象，定义了一些统一的生命周期方法和运行规则（所有方法都必须在系统服务进程的main looper thread中被调用）。

package com.android.server;

import android.os.ServiceManager;
/**
 * The base class for services running in the system process. Override and implement
 * the lifecycle event callback methods as needed.
 * {@hide}
 */
public abstract class SystemService {
    
    
    ...
    private final Context mContext;
    public SystemService(Context context) {
    
    
        mContext = context;
    }
    public abstract void onStart();
		...
    protected final void publishBinderService(String name, IBinder service) {
    
    
        publishBinderService(name, service, false);
    }
    protected final void publishBinderService(String name, IBinder service,
            boolean allowIsolated) {
    
    
        ServiceManager.addService(name, service, allowIsolated);
    }
    protected final IBinder getBinderService(String name) {
    
    
        return ServiceManager.getService(name);
    }
    protected final <T> void publishLocalService(Class<T> type, T service) {
    
    
        LocalServices.addService(type, service);
    }
    protected final <T> T getLocalService(Class<T> type) {
    
    
        return LocalServices.getService(type);
    }

    private SystemServiceManager getManager() {
    
    
        return LocalServices.getService(SystemServiceManager.class);
    }
}

三、Intsaller系统服务的启动

1、com.android.server.SystemServer#startBootstrapServices 触发Installer系统服务启动

    private void startBootstrapServices() {
    
    
        Installer installer = mSystemServiceManager.startService(Installer.class);

2、com.android.server.SystemServiceManager#startService反射创建并回调com.android.server.pm.Installer#onStart

\frameworks\base\services\core\java\com\android\server\SystemServiceManager.java

2.1、com.android.server.SystemServiceManager#startService(String className)获取Installer的字节码对象

    public SystemService startService(String className) {
    
    
        final Class<SystemService> serviceClass;
        serviceClass = (Class<SystemService>)Class.forName(className);
        return startService(serviceClass);
    }

2.2、com.android.server.SystemServiceManager#startService(java.lang.Class< T >)反射创建Installer对象

 /**
     * Creates and starts a system service. The class must be a subclass of
     * {@link com.android.server.SystemService}.
     */
    public <T extends SystemService> T startService(Class<T> serviceClass) {
    
    
        try {
    
    
            final String name = serviceClass.getName();
            // Create the service.
            final T service;
            try {
    
    
                Constructor<T> constructor = serviceClass.getConstructor(Context.class);
                service = constructor.newInstance(mContext);
            } 
            startService(service);
            return service;
        }
    }

2.3、com.android.server.SystemServiceManager#startService(SystemService) 注册到SystemServerManager并触发Installer#onStart回调

 public void startService(@NonNull final SystemService service) {
    
    
        // @link ArrayList<SystemService> mServices 注册到SystemServerManager中
        mServices.add(service);
        long time = SystemClock.elapsedRealtime();
        try {
    
    
            service.onStart();
        }
        warnIfTooLong(SystemClock.elapsedRealtime() - time, service, "onStart");
    }

3、com.android.server.pm.Installer#onStart 获取installd 的Binder服务代理对象

3.1、com.android.server.pm.Installer#onStart 触发获取installd 的Binder服务代理对象

    @Override
    public void onStart() {
    
    
        if (mIsolated) {
    
    
            mInstalld = null;
        } else {
    
    
            connect();
        }
    } 

3.2、com.android.server.pm.Installer#connect 真正获取installd 的Binder服务代理对象

    private void connect() {
    
    
    	//首先通过ServiceManager 获取installd服务的Binder对象
        IBinder binder = ServiceManager.getService("installd");
        if (binder != null) {
    
    
            try {
    
    
                binder.linkToDeath(new DeathRecipient() {
    
    
                    @Override
                    public void binderDied() {
    
    
                        Slog.w(TAG, "installd died; reconnecting");
                        connect();
                    }
                }, 0);
            } catch (RemoteException e) {
    
    
                binder = null;
            }
        }

        if (binder != null) {
    
    
            //把Binder对象转为具体的Binder服务对象
            mInstalld = IInstalld.Stub.asInterface(binder);
            try {
    
    
                invalidateMounts();
            } catch (InstallerException ignored) {
    
    
            }
        } else {
    
    
            Slog.w(TAG, "installd not found; trying again");
            BackgroundThread.getHandler().postDelayed(() -> {
    
    
                connect();
            }, DateUtils.SECOND_IN_MILLIS);
        }
    }

至此Installer系统服务启动完毕，接着真正开始其他系统服务的启动，敬请参见下集。