PackageManagerService分析之一

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1, 基本概念

PackageManagerService(简称PMS), 是android系统中一个核心的服务，

它负责系统中Package的管理，应该程序的安装、卸载等.在SystemServer的startBootstrapServices方法启动。

mPackageManagerService = PackageManagerService.main(mSystemContext, installer,                mFactoryTestMode != FactoryTest.FACTORY_TEST_OFF, mOnlyCore);

PMS的main方法如下,

   public static PackageManagerService main(Context context, Installer installer,            boolean factoryTest, boolean onlyCore) {        PackageManagerService m = new PackageManagerService(context, installer,                factoryTest, onlyCore);        ServiceManager.addService("package", m); // 注册        return m;    }

看来所有动作都在PMS的构造方法中完成的。

再看看PMS的结构可知,PMS服务也是一个Binder服务,

public class PackageManagerService extends IPackageManager.Stub {

在ActivityThread的getPackageManager方法中,可以获取PMS服务。

if (sPackageManager != null) {            //Slog.v("PackageManager", "returning cur default = " + sPackageManager);            return sPackageManager;        }        IBinder b = ServiceManager.getService("package");        //Slog.v("PackageManager", "default service binder = " + b);        sPackageManager = IPackageManager.Stub.asInterface(b);        //Slog.v("PackageManager", "default service = " + sPackageManager);        return sPackageManager;    }

PMS的构造方法很长很长,主要包括以下逻辑

扫描目标文件夹之前的准备工作。
扫描目标文件夹。
扫描之后的工作。

2, 准备工作

PMS的构造方法关于Settings部分代码如下,

mSettings = new Settings(mPackages);        mSettings.addSharedUserLPw("android.uid.system", Process.SYSTEM_UID,                ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);        mSettings.addSharedUserLPw("android.uid.phone", RADIO_UID,                ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);        mSettings.addSharedUserLPw("android.uid.log", LOG_UID,                ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);        mSettings.addSharedUserLPw("android.uid.nfc", NFC_UID,                ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);        mSettings.addSharedUserLPw("android.uid.bluetooth", BLUETOOTH_UID,                ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);        mSettings.addSharedUserLPw("android.uid.shell", SHELL_UID,                ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);

mPackages是一个ArrayMap变量,

@GuardedBy("mPackages")    final ArrayMap<String, PackageParser.Package> mPackages =            new ArrayMap<String, PackageParser.Package>();

流程图如下,

2.1 Settings

Settings的构造方法如下,

Settings(Object lock) {        this(Environment.getDataDirectory(), lock);    }    Settings(File dataDir, Object lock) {        mLock = lock;        mRuntimePermissionsPersistence = new RuntimePermissionPersistence(mLock);        mSystemDir = new File(dataDir, "system");        mSystemDir.mkdirs();        FileUtils.setPermissions(mSystemDir.toString(),                FileUtils.S_IRWXU|FileUtils.S_IRWXG                |FileUtils.S_IROTH|FileUtils.S_IXOTH,                -1, -1);        mSettingsFilename = new File(mSystemDir, "packages.xml");        mBackupSettingsFilename = new File(mSystemDir, "packages-backup.xml");        mPackageListFilename = new File(mSystemDir, "packages.list");        FileUtils.setPermissions(mPackageListFilename, 0640, SYSTEM_UID, PACKAGE_INFO_GID);        // Deprecated: Needed for migration        mStoppedPackagesFilename = new File(mSystemDir, "packages-stopped.xml");        mBackupStoppedPackagesFilename = new File(mSystemDir, "packages-stopped-backup.xml");    }

新建了5个文件夹,

private final File mSettingsFilename;    private final File mBackupSettingsFilename;    private final File mPackageListFilename;    private final File mStoppedPackagesFilename;    private final File mBackupStoppedPackagesFilename;

Environment.getDataDirectory()返回/data目录，然后创建/data/system/目录，并设置它的权限，

并在/data/system目录中创建5个文件。packages.xml就是保存了系统所有的Package信息，

packages-backup.xml是packages.xml的备份，防止在写packages.xml突然断电等问题。

2.2 addSharedUserLPw

mSettings.addSharedUserLPw("android.uid.system", Process.SYSTEM_UID,                ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);

调用addSharedUserLPw将几种SharedUserId的名字和它对应的UID对应写到Settings当中。

关于 SharedUserId的使用，在后面介绍APK的安装过程中再来分析. Process中提供的UID列表如下,

public static final int ROOT_UID = 0; public static final int SYSTEM_UID = 1000; // systempublic static final int PHONE_UID = 1001;// telephonypublic static final int SHELL_UID = 2000;// user shellpublic static final int LOG_UID = 1007;// log group public static final int WIFI_UID = 1010;// WIFI•••

Settings中的addSharedUserLPw方法如下,

SharedUserSetting addSharedUserLPw(String name, int uid, int pkgFlags, int pkgPrivateFlags) {        SharedUserSetting s = mSharedUsers.get(name);        if (s != null) {            if (s.userId == uid) {                return s;            }            PackageManagerService.reportSettingsProblem(Log.ERROR,                    "Adding duplicate shared user, keeping first: " + name);            return null;        }        s = new SharedUserSetting(name, pkgFlags, pkgPrivateFlags);        s.userId = uid;        if (addUserIdLPw(uid, s, name)) {            mSharedUsers.put(name, s);            return s;        }        return null;    }

首先根据name, pkgFlags, pkgPrivateFlags等信息构造SharedUserSetting,然后添加到mSharedUsers的ArrayMap中。

final ArrayMap<String, SharedUserSetting> mSharedUsers =            new ArrayMap<String, SharedUserSetting>();

例如在SystemUI.apk的AndroidManifest.xml文件中，有关键代码：

<mainfest xmlns:android="http://schemas.android.com/apk/res/android"        package="com.android.systemui"        coreApp="true"        android:sharedUserId="android.uid.system"        android:process="system">

在该标签中，声明了一个android:sharedUserId的属性，其值为“android.uid.system”。sharedUserId和UID有关，它的作用是

1,两个或者多个声明了同一种sharedUserid的APK可共享彼此的数据，并且可运行在同一进程中。

2,通过声明特定的sharedUserId,该APK所在的进程将被赋予指定UID。

例如SystemUI声明了system的uid，运行SystemUI的进程就可享有system用户所对应的权限了，实际上就是将该进程的UID设置为system的uid了

2.3 XML文件扫描

接下来是扫描系统目录下与系统权限相关的xml文件,新建文件,处理线程和Handler等。

String separateProcesses = SystemProperties.get("debug.separate_processes");        if (separateProcesses != null && separateProcesses.length() > 0) {            if ("*".equals(separateProcesses)) {                mDefParseFlags = PackageParser.PARSE_IGNORE_PROCESSES;                mSeparateProcesses = null;                Slog.w(TAG, "Running with debug.separate_processes: * (ALL)");            } else {                mDefParseFlags = 0;                mSeparateProcesses = separateProcesses.split(",");                Slog.w(TAG, "Running with debug.separate_processes: "                        + separateProcesses);            }        } else {            mDefParseFlags = 0;            mSeparateProcesses = null;        }        mInstaller = installer;        mPackageDexOptimizer = new PackageDexOptimizer(this);        mMoveCallbacks = new MoveCallbacks(FgThread.get().getLooper());        mOnPermissionChangeListeners = new OnPermissionChangeListeners(                FgThread.get().getLooper());        getDefaultDisplayMetrics(context, mMetrics);        SystemConfig systemConfig = SystemConfig.getInstance();        mGlobalGids = systemConfig.getGlobalGids();        mSystemPermissions = systemConfig.getSystemPermissions();        mAvailableFeatures = systemConfig.getAvailableFeatures();

新建文件

 File dataDir = Environment.getDataDirectory();            mAppDataDir = new File(dataDir, "data");            mAppInstallDir = new File(dataDir, "app");            mAppLib32InstallDir = new File(dataDir, "app-lib");            mAsecInternalPath = new File(dataDir, "app-asec").getPath();            mUserAppDataDir = new File(dataDir, "user");            mDrmAppPrivateInstallDir = new File(dataDir, "app-private");            mRegionalizationAppInstallDir = new File(dataDir, "app-regional");

解析系统权限文件, 主要是解析系统目录下xml文件，获得设备相关的权限.

例如该设备是否支持蓝牙,wifi等

ArrayMap<String, SystemConfig.PermissionEntry> permConfig                    = systemConfig.getPermissions();            for (int i=0; i<permConfig.size(); i++) {                SystemConfig.PermissionEntry perm = permConfig.valueAt(i);                BasePermission bp = mSettings.mPermissions.get(perm.name);                if (bp == null) {                    bp = new BasePermission(perm.name, "android", BasePermission.TYPE_BUILTIN);                    mSettings.mPermissions.put(perm.name, bp);                }                if (perm.gids != null) {                    bp.setGids(perm.gids, perm.perUser);                }            }

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