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PackageManagerService分析之一_ipackagemanager.stub.asinterfac

作者：笔触狂放9 | 2024-03-06 13:25:48

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ipackagemanager.stub.asinterfac

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。

  1. mPackageManagerService = PackageManagerService.main(mSystemContext, installer,
  2.                 mFactoryTestMode != FactoryTest.FACTORY_TEST_OFF, mOnlyCore);
PMS的main方法如下, 
  1.    public static PackageManagerService main(Context context, Installer installer,
  2.             boolean factoryTest, boolean onlyCore) {
  3.         PackageManagerService m = new PackageManagerService(context, installer,
  4.                 factoryTest, onlyCore);
  5.         ServiceManager.addService("package", m); // 注册
  6.         return m;
  7.     }

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。

  1. if (sPackageManager != null) {
  2.             //Slog.v("PackageManager", "returning cur default = " + sPackageManager);
  3.             return sPackageManager;
  4.         }
  5.         IBinder b = ServiceManager.getService("package");
  6.         //Slog.v("PackageManager", "default service binder = " + b);
  7.         sPackageManager = IPackageManager.Stub.asInterface(b);
  8.         //Slog.v("PackageManager", "default service = " + sPackageManager);
  9.         return sPackageManager;
  10.     }

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,

  1. mSettings = new Settings(mPackages);
  2.         mSettings.addSharedUserLPw("android.uid.system", Process.SYSTEM_UID,
  3.                 ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);
  4.         mSettings.addSharedUserLPw("android.uid.phone", RADIO_UID,
  5.                 ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);
  6.         mSettings.addSharedUserLPw("android.uid.log", LOG_UID,
  7.                 ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);
  8.         mSettings.addSharedUserLPw("android.uid.nfc", NFC_UID,
  9.                 ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);
  10.         mSettings.addSharedUserLPw("android.uid.bluetooth", BLUETOOTH_UID,
  11.                 ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);
  12.         mSettings.addSharedUserLPw("android.uid.shell", SHELL_UID,
  13.                 ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);

mPackages是一个ArrayMap变量,

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

流程图如下,


2.1 Settings

Settings的构造方法如下,

  1. Settings(Object lock) {
  2.         this(Environment.getDataDirectory(), lock);
  3.     }
  4.  
  5.     Settings(File dataDir, Object lock) {
  6.         mLock = lock;
  7.  
  8.         mRuntimePermissionsPersistence = new RuntimePermissionPersistence(mLock);
  9.  
  10.         mSystemDir = new File(dataDir, "system");
  11.         mSystemDir.mkdirs();
  12.         FileUtils.setPermissions(mSystemDir.toString(),
  13.                 FileUtils.S_IRWXU|FileUtils.S_IRWXG
  14.                 |FileUtils.S_IROTH|FileUtils.S_IXOTH,
  15.                 -1, -1);
  16.         mSettingsFilename = new File(mSystemDir, "packages.xml");
  17.         mBackupSettingsFilename = new File(mSystemDir, "packages-backup.xml");
  18.         mPackageListFilename = new File(mSystemDir, "packages.list");
  19.         FileUtils.setPermissions(mPackageListFilename, 0640, SYSTEM_UID, PACKAGE_INFO_GID);
  20.  
  21.         // Deprecated: Needed for migration
  22.         mStoppedPackagesFilename = new File(mSystemDir, "packages-stopped.xml");
  23.         mBackupStoppedPackagesFilename = new File(mSystemDir, "packages-stopped-backup.xml");
  24.     }

新建了5个文件夹,

  1. private final File mSettingsFilename;
  2.     private final File mBackupSettingsFilename;
  3.     private final File mPackageListFilename;
  4.     private final File mStoppedPackagesFilename;
  5.     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

  1. mSettings.addSharedUserLPw("android.uid.system", Process.SYSTEM_UID,
  2.                 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,

  1. public static final int ROOT_UID = 0; 
  2. public static final int SYSTEM_UID = 1000; // system
  3. public static final int PHONE_UID = 1001;// telephony
  4. public static final int SHELL_UID = 2000;// user shell
  5. public static final int LOG_UID = 1007;// log group
  6.  public static final int WIFI_UID = 1010;// WIFI
  7. •••

Settings中的addSharedUserLPw方法如下,

  1. SharedUserSetting addSharedUserLPw(String name, int uid, int pkgFlags, int pkgPrivateFlags) {
  2.         SharedUserSetting s = mSharedUsers.get(name);
  3.         if (s != null) {
  4.             if (s.userId == uid) {
  5.                 return s;
  6.             }
  7.             PackageManagerService.reportSettingsProblem(Log.ERROR,
  8.                     "Adding duplicate shared user, keeping first: " + name);
  9.             return null;
  10.         }
  11.         s = new SharedUserSetting(name, pkgFlags, pkgPrivateFlags);
  12.         s.userId = uid;
  13.         if (addUserIdLPw(uid, s, name)) {
  14.             mSharedUsers.put(name, s);
  15.             return s;
  16.         }
  17.         return null;
  18.     }

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

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

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

  1. <mainfest xmlns:android="http://schemas.android.com/apk/res/android"
  2.         package="com.android.systemui"
  3.         coreApp="true"
  4.         android:sharedUserId="android.uid.system"
  5.         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。

  1. String separateProcesses = SystemProperties.get("debug.separate_processes");
  2.         if (separateProcesses != null && separateProcesses.length() > 0) {
  3.             if ("*".equals(separateProcesses)) {
  4.                 mDefParseFlags = PackageParser.PARSE_IGNORE_PROCESSES;
  5.                 mSeparateProcesses = null;
  6.                 Slog.w(TAG, "Running with debug.separate_processes: * (ALL)");
  7.             } else {
  8.                 mDefParseFlags = 0;
  9.                 mSeparateProcesses = separateProcesses.split(",");
  10.                 Slog.w(TAG, "Running with debug.separate_processes: "
  11.                         + separateProcesses);
  12.             }
  13.         } else {
  14.             mDefParseFlags = 0;
  15.             mSeparateProcesses = null;
  16.         }
  17.  
  18.         mInstaller = installer;
  19.         mPackageDexOptimizer = new PackageDexOptimizer(this);
  20.         mMoveCallbacks = new MoveCallbacks(FgThread.get().getLooper());
  21.  
  22.         mOnPermissionChangeListeners = new OnPermissionChangeListeners(
  23.                 FgThread.get().getLooper());
  24.  
  25.         getDefaultDisplayMetrics(context, mMetrics);
  26.  
  27.         SystemConfig systemConfig = SystemConfig.getInstance();
  28.         mGlobalGids = systemConfig.getGlobalGids();
  29.         mSystemPermissions = systemConfig.getSystemPermissions();
  30.         mAvailableFeatures = systemConfig.getAvailableFeatures();

新建文件

  1.  File dataDir = Environment.getDataDirectory();
  2.             mAppDataDir = new File(dataDir, "data");
  3.             mAppInstallDir = new File(dataDir, "app");
  4.             mAppLib32InstallDir = new File(dataDir, "app-lib");
  5.             mAsecInternalPath = new File(dataDir, "app-asec").getPath();
  6.             mUserAppDataDir = new File(dataDir, "user");
  7.             mDrmAppPrivateInstallDir = new File(dataDir, "app-private");
  8.             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

  1. ArrayMap<String, SystemConfig.PermissionEntry> permConfig
  2.                     = systemConfig.getPermissions();
  3.             for (int i=0; i<permConfig.size(); i++) {
  4.                 SystemConfig.PermissionEntry perm = permConfig.valueAt(i);
  5.                 BasePermission bp = mSettings.mPermissions.get(perm.name);
  6.                 if (bp == null) {
  7.                     bp = new BasePermission(perm.name, "android", BasePermission.TYPE_BUILTIN);
  8.                     mSettings.mPermissions.put(perm.name, bp);
  9.                 }
  10.                 if (perm.gids != null) {
  11.                     bp.setGids(perm.gids, perm.perUser);
  12.                 }
  13.             }

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