Android PakageManagerService源码解析
2019-01-02 本文已影响13人
孤独的根号十二
PakageManagerService
PakageManagerService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。
SystemServer进程是Zygote孵化出的第一个进程，该进程主要的工作是启动android系统服务进程，其中包括PackageManagerService服务
SystemServer:run()
try {
startBootstrapServices();
startCoreServices();
startOtherServices();
} catch (Throwable ex) {
Slog.e("System", "******************************************");
Slog.e("System", "************ Failure starting system services", ex);
throw ex;
}
启动PakageManagerService
private void startBootstrapServices() {
//...
//调用PMS的main函数
mPackageManagerService = PackageManagerService.main(mSystemContext, installer,
mFactoryTestMode != FactoryTest.FACTORY_TEST_OFF, mOnlyCore);
//判断本次是否为初次启动，当Zygote或者SystemServer退出时，init会再次启动它们，所以这里
//的firstBoot指的是开机后的第一次启动
mFirstBoot = mPackageManagerService.isFirstBoot();
mPackageManager = mSystemContext.getPackageManager();
//...
}
PakageManagerService的main()
//扫描Android系统中几个目标文件夹的APK，建立对应的数据结构来管理Package信息、四大组件信息、权限信息等各种信息
public static PackageManagerService main(Context context, Installer installer,
boolean factoryTest, boolean onlyCore) {
//new 一个PackageManagerService对象
PackageManagerService m = new PackageManagerService(context, installer,
factoryTest, onlyCore);
//PKM注册到ServiceManager上。ServiceManager相当于安卓系统服务的DNS服务器
ServiceManager.addService("package", m);
return m;
}
PakageManagerService的构造方法
public PackageManagerService(Context context, Installer installer,
boolean factoryTest, boolean onlyCore) {
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_START,
SystemClock.uptimeMillis());
if (mSdkVersion <= 0) {
Slog.w(TAG, "**** ro.build.version.sdk not set!");
}
mContext = context; //ActivityThread getSystemContext()
mFactoryTest = factoryTest; // //是否在工厂测试模式下，假定为false
mOnlyCore = onlyCore;
mLazyDexOpt = "eng".equals(SystemProperties.get("ro.build.type")); //如果此系统是“eng”版，扫描Package后，不对package做dex优化
mMetrics = new DisplayMetrics();
//第一个参数是字符串“android.uid.system”;第二个是SYSTEM_UID，其值为1000，
//第三个是FLAG_SYSTEM标志，用于标识系统Package。
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);
Settings 与在manifest注册android:sharedUserId="android.uid.system"有关
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
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。
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
..........................................省略部分代码...............................................
// 获取系统相关的权限，它主要是解析系统目录下xml文件，获得设备相关的权限
SystemConfig systemConfig = SystemConfig.getInstance();
mGlobalGids = systemConfig.getGlobalGids();
mSystemPermissions = systemConfig.getSystemPermissions();
mAvailableFeatures = systemConfig.getAvailableFeatures();
synchronized (mInstallLock) {
// writer
synchronized (mPackages) {
//创建一个ThreadHandler对象，实际就是创建一个带消息队列循环处理的线程，
//该线程的工作是：程序的安装和卸载等。
mHandlerThread = new ServiceThread(TAG,
Process.THREAD_PRIORITY_BACKGROUND, true /*allowIo*/);
mHandlerThread.start();
//以ThreadHandler线程的消息循环（Looper对象）作为参数new一个
//PackageHandler，因此该Handler的handlemessage方法将运行在此线程上
mHandler = new PackageHandler(mHandlerThread.getLooper());
Watchdog.getInstance().addThread(mHandler, WATCHDOG_TIMEOUT);
// /data目录
File dataDir = Environment.getDataDirectory();
// /data/data目录
mAppDataDir = new File(dataDir, "data");
// /data/app目录
mAppInstallDir = new File(dataDir, "app");
// /data/app-lib目录
mAppLib32InstallDir = new File(dataDir, "app-lib");
// /data/app-asec目录
mAsecInternalPath = new File(dataDir, "app-asec").getPath();
// /data/user目录
mUserAppDataDir = new File(dataDir, "user");
// /data/app-private目录
mDrmAppPrivateInstallDir = new File(dataDir, "app-private");
//new一个UserManager对象，目前没有什么作用，但其前途[不可限量](https://www.baidu.com/s?wd=%E4%B8%8D%E5%8F%AF%E9%99%90%E9%87%8F&tn=24004469_oem_dg&rsv_dl=gh_pl_sl_csd)。
//google设想，未来手机将支持多个User，每个User安装自己的应用
//该功能为android智能手机推向企业用户打下基础
sUserManager = new UserManagerService(context, this,
mInstallLock, mPackages);
// 获取系统相关的权限，它主要是解析系统目录下xml文件，获得设备相关的权限
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);
}
}
//获得系统的Libraries，也就是系统的一些jar
ArrayMap<String, String> libConfig = systemConfig.getSharedLibraries();
for (int i=0; i<libConfig.size(); i++) {
mSharedLibraries.put(libConfig.keyAt(i),
new SharedLibraryEntry(libConfig.valueAt(i), null));
}
mFoundPolicyFile = SELinuxMMAC.readInstallPolicy();
mRestoredSettings = mSettings.readLPw(this, sUserManager.getUsers(false),
mSdkVersion, mOnlyCore);
String customResolverActivity = Resources.getSystem().getString(
R.string.config_customResolverActivity);
if (TextUtils.isEmpty(customResolverActivity)) {
customResolverActivity = null;
} else {
mCustomResolverComponentName = ComponentName.unflattenFromString(
customResolverActivity);
}
long startTime = SystemClock.uptimeMillis();
/**
* Ensure all external libraries have had dexopt run on them.
*扫描优化各种系统库，主要是扫描系统中的APK，由于需要逐个扫描apk文件，因此手机上安装的程序越多，PKM的工作量越大，系统启动速度越慢，也就是开机时间越长。
*/
if (mSharedLibraries.size() > 0) {
// NOTE: For now, we're compiling these system "shared libraries"
// (and framework jars) into all available architectures. It's possible
// to compile them only when we come across an app that uses them (there's
// already logic for that in scanPackageLI) but that adds some complexity.
for (String dexCodeInstructionSet : dexCodeInstructionSets) {
for (SharedLibraryEntry libEntry : mSharedLibraries.values()) {
final String lib = libEntry.path;
if (lib == null) {
continue;
}
try {
int dexoptNeeded = DexFile.getDexOptNeeded(lib, null, dexCodeInstructionSet, false);
if (dexoptNeeded != DexFile.NO_DEXOPT_NEEDED) {
alreadyDexOpted.add(lib);
mInstaller.dexopt(lib, Process.SYSTEM_UID, true, dexCodeInstructionSet, dexoptNeeded);
}
} catch (FileNotFoundException e) {
Slog.w(TAG, "Library not found: " + lib);
} catch (IOException e) {
Slog.w(TAG, "Cannot dexopt " + lib + "; is it an APK or JAR? "
+ e.getMessage());
}
}
}
}
File frameworkDir = new File(Environment.getRootDirectory(), "framework");
// Gross hack for now: we know this file doesn't contain any
// code, so don't dexopt it to avoid the resulting log spew.
alreadyDexOpted.add(frameworkDir.getPath() + "/framework-res.apk");
// Gross hack for now: we know this file is only part of
// the boot class path for art, so don't dexopt it to
// avoid the resulting log spew.
alreadyDexOpted.add(frameworkDir.getPath() + "/core-libart.jar");
/**
* There are a number of commands implemented in Java, which
* we currently need to do the dexopt on so that they can be
* run from a non-root shell.
*/
String[] frameworkFiles = frameworkDir.list();
if (frameworkFiles != null) {
// TODO: We could compile these only for the most preferred ABI. We should
// first double check that the dex files for these commands are not referenced
// by other system apps.
for (String dexCodeInstructionSet : dexCodeInstructionSets) {
for (int i=0; i<frameworkFiles.length; i++) {
File libPath = new File(frameworkDir, frameworkFiles[i]);
String path = libPath.getPath();
// Skip the file if we already did it.
if (alreadyDexOpted.contains(path)) {
continue;
}
// Skip the file if it is not a type we want to dexopt.
if (!path.endsWith(".apk") && !path.endsWith(".jar")) {
continue;
}
try {
int dexoptNeeded = DexFile.getDexOptNeeded(path, null, dexCodeInstructionSet, false);
if (dexoptNeeded != DexFile.NO_DEXOPT_NEEDED) {
//dex优化
mInstaller.dexopt(path, Process.SYSTEM_UID, true, dexCodeInstructionSet, dexoptNeeded);
}
} catch (FileNotFoundException e) {
Slog.w(TAG, "Jar not found: " + path);
} catch (IOException e) {
Slog.w(TAG, "Exception reading jar: " + path, e);
}
}
}
}
//下面代码就是扫描系统app和厂商默认的app，还有已经安装的app
// Collect vendor overlay packages.
// (Do this before scanning any apps.)
// For security and version matching reason, only consider
// overlay packages if they reside in VENDOR_OVERLAY_DIR.
File vendorOverlayDir = new File(VENDOR_OVERLAY_DIR);
scanDirLI(vendorOverlayDir, PackageParser.PARSE_IS_SYSTEM
| PackageParser.PARSE_IS_SYSTEM_DIR, scanFlags | SCAN_TRUSTED_OVERLAY, 0);
// Find base frameworks (resource packages without code).
scanDirLI(frameworkDir, PackageParser.PARSE_IS_SYSTEM
| PackageParser.PARSE_IS_SYSTEM_DIR
| PackageParser.PARSE_IS_PRIVILEGED,
scanFlags | SCAN_NO_DEX, 0);
// Collected privileged system packages.
final File privilegedAppDir = new File(Environment.getRootDirectory(), "priv-app");
scanDirLI(privilegedAppDir, PackageParser.PARSE_IS_SYSTEM
| PackageParser.PARSE_IS_SYSTEM_DIR
| PackageParser.PARSE_IS_PRIVILEGED, scanFlags, 0);
// Collect ordinary system packages.
final File systemAppDir = new File(Environment.getRootDirectory(), "app");
scanDirLI(systemAppDir, PackageParser.PARSE_IS_SYSTEM
| PackageParser.PARSE_IS_SYSTEM_DIR, scanFlags, 0);
// Collect all vendor packages.
File vendorAppDir = new File("/vendor/app");
try {
vendorAppDir = vendorAppDir.getCanonicalFile();
} catch (IOException e) {
// failed to look up canonical path, continue with original one
}
scanDirLI(vendorAppDir, PackageParser.PARSE_IS_SYSTEM
| PackageParser.PARSE_IS_SYSTEM_DIR, scanFlags, 0);
// Collect all OEM packages.
final File oemAppDir = new File(Environment.getOemDirectory(), "app");
scanDirLI(oemAppDir, PackageParser.PARSE_IS_SYSTEM
| PackageParser.PARSE_IS_SYSTEM_DIR, scanFlags, 0);
解析每个app的manifest文件，添加4大组件
private PackageParser.Package scanPackageDirtyLI(PackageParser.Package pkg, int parseFlags,
int scanFlags, long currentTime, UserHandle user) throws PackageManagerException {
//省略部分代码
N = pkg.activities.size();
r = null;
for (i=0; i<N; i++){
PackageParser.Activity a = pkg.activities.get(i);
a.info.processName = fixProcessName(pkg.applicationInfo.processName,
a.info.processName, pkg.applicationInfo.uid);
mActivities.addActivity(a, "activity");
if ((parseFlags&PackageParser.PARSE_CHATTY) != 0) {
if (r == null) {
r = new StringBuilder(256);
} else {
r.append(' ');
}
r.append(a.info.name);
}
}
......................................
N = pkg.receivers.size();
r = null;
for (i=0; i<N; i++) {
PackageParser.Activity a = pkg.receivers.get(i);
a.info.processName = fixProcessName(pkg.applicationInfo.processName,
a.info.processName, pkg.applicationInfo.uid);
mReceivers.addActivity(a, "receiver");
if ((parseFlags&PackageParser.PARSE_CHATTY) != 0) {
if (r == null) {
r = new StringBuilder(256);
} else {
r.append(' ');
}
r.append(a.info.name);
}
}
.........................................
}
5.4扫描系统和非系统apk总结
PKM在这个过程中工作任务非常繁重，要创建很多的对象，所以它是一个耗时耗内存的操作，从流程来看，PKM在这个过程中无非是扫描XML或者APK文件，但是其中涉及的数据结构及它们的关系较为复杂。
