PackageManagerService启动及初始化流程

PackageManagerService也是有ServerThread启动的，运行在system_process进程。

我们先来看下PackageManagerService是怎么启动的：

PackageManagerService的启动需要四个参数，context上下文环境信息由ActivityManagerService获 取，installer是一个安装器，是对install程序的一个封装，在new一个Installer之后会调用ping命令测试是否能连接的上 install的服务端。

再来看一下PackageManagerService的初始化流程：

相关代码：

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;
        mFactoryTest = factoryTest;
        mOnlyCore = onlyCore;
        mNoDexOpt = "eng".equals(SystemProperties.get("ro.build.type"));
        mMetrics = new DisplayMetrics();
        mSettings = new Settings(context);//新建一个Settings结构
        mSettings.addSharedUserLPw("android.uid.system", //添加一些用户id
                Process.SYSTEM_UID, ApplicationInfo.FLAG_SYSTEM);
        mSettings.addSharedUserLPw("android.uid.phone", RADIO_UID, ApplicationInfo.FLAG_SYSTEM);
        mSettings.addSharedUserLPw("android.uid.log", LOG_UID, ApplicationInfo.FLAG_SYSTEM);
        mSettings.addSharedUserLPw("android.uid.nfc", NFC_UID, ApplicationInfo.FLAG_SYSTEM);
        mSettings.addSharedUserLPw("android.uid.bluetooth", BLUETOOTH_UID, ApplicationInfo.FLAG_SYSTEM);

        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;//在ServerThread中创建，调用了其中的ping测试是否连上

        WindowManager wm = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE);//获取WINDOW_SERVICE
        Display d = wm.getDefaultDisplay();//获取显示参数
        d.getMetrics(mMetrics);

        synchronized (mInstallLock) {
        // writer
        synchronized (mPackages) {
            mHandlerThread.start();//启动消息处理循环
            mHandler = new PackageHandler(mHandlerThread.getLooper());//PackageHandler封装了对消息的处理

            File dataDir = Environment.getDataDirectory();///data
            mAppDataDir = new File(dataDir, "data");//待检测目录/data/data
            mAppInstallDir = new File(dataDir, "app");///data/app
            mAppLibInstallDir = new File(dataDir, "app-lib");///data/app-lib
            mAsecInternalPath = new File(dataDir, "app-asec").getPath();///data/app-asec
            mUserAppDataDir = new File(dataDir, "user");///data/user
            mDrmAppPrivateInstallDir = new File(dataDir, "app-private");///data/app-private

            sUserManager = new UserManagerService(context, this,
                    mInstallLock, mPackages);//创建一个UserManagerService

            readPermissions();//读取权限配置文件中的信息，保存到全局变量

            mRestoredSettings = mSettings.readLPw(sUserManager.getUsers(false));
            long startTime = SystemClock.uptimeMillis();

            EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_SYSTEM_SCAN_START,
                    startTime);

            // Set flag to monitor and not change apk file paths when
            // scanning install directories.
            int scanMode = SCAN_MONITOR | SCAN_NO_PATHS | SCAN_DEFER_DEX | SCAN_BOOTING;//设置扫描模式
            if (mNoDexOpt) {
                Slog.w(TAG, "Running ENG build: no pre-dexopt!");
                scanMode |= SCAN_NO_DEX;
            }

            final HashSet libFiles = new HashSet();

            mFrameworkDir = new File(Environment.getRootDirectory(), "framework");///system/framework
            mDalvikCacheDir = new File(dataDir, "dalvik-cache");///data/dalvik-cache

            boolean didDexOpt = false;

            /**
             * Out of paranoia, ensure that everything in the boot class
             * path has been dexed.
             */
            String bootClassPath = System.getProperty("java.boot.class.path");//所有在bootClassPath目录的类已经优化了
            if (bootClassPath != null) {//确保 boot路径的class都被优化了
                String[] paths = splitString(bootClassPath, ':');
                for (int i=0; i
                    try {
                        if (dalvik.system.DexFile.isDexOptNeeded(paths[i])) {//需要优化？
                            libFiles.add(paths[i]);
                            mInstaller.dexopt(paths[i], Process.SYSTEM_UID, true);
                            didDexOpt = true;
                        }
                    } catch (FileNotFoundException e) {
                        Slog.w(TAG, "Boot class path not found: " + paths[i]);
                    } catch (IOException e) {
                        Slog.w(TAG, "Cannot dexopt " + paths[i] + "; is it an APK or JAR? "
                                + e.getMessage());
                    }
                }
            } else {
                Slog.w(TAG, "No BOOTCLASSPATH found!");
            }

            /**
             * Also ensure all external libraries have had dexopt run on them.
             */
            if (mSharedLibraries.size() > 0) {//确保 外部库也被 优化
                Iterator libs = mSharedLibraries.values().iterator();
                while (libs.hasNext()) {
                    String lib = libs.next();
                    try {
                        if (dalvik.system.DexFile.isDexOptNeeded(lib)) {
                            libFiles.add(lib);
                            mInstaller.dexopt(lib, Process.SYSTEM_UID, true);
                            didDexOpt = true;
                        }
                    } 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());
                    }
                }
            }

            // Gross hack for now: we know this file doesn't contain any
            // code, so don't dexopt it to avoid the resulting log spew.
            libFiles.add(mFrameworkDir.getPath() + "/framework-res.apk");//framework-res.apk没有包含代码，不需要优化

            /**
             * And 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 = mFrameworkDir.list();
            if (frameworkFiles != null) {
                for (int i=0; i//优化/system/framework目录下的文件
                    File libPath = new File(mFrameworkDir, frameworkFiles[i]);
                    String path = libPath.getPath();
                    // Skip the file if we alrady did it.
                    if (libFiles.contains(path)) {//已经包含过，包含过的都优化了
                        continue;
                    }
                    // Skip the file if it is not a type we want to dexopt.
                    if (!path.endsWith(".apk") && !path.endsWith(".jar")) {//跳过不符合条件的
                        continue;
                    }
                    try {
                        if (dalvik.system.DexFile.isDexOptNeeded(path)) {//需要优化
                            mInstaller.dexopt(path, Process.SYSTEM_UID, true);
                            didDexOpt = true;
                        }
                    } catch (FileNotFoundException e) {
                        Slog.w(TAG, "Jar not found: " + path);
                    } catch (IOException e) {
                        Slog.w(TAG, "Exception reading jar: " + path, e);
                    }
                }
            }

            if (didDexOpt) {
                // If we had to do a dexopt of one of the previous
                // things, then something on the system has changed.
                // Consider this significant, and wipe away all other
                // existing dexopt files to ensure we don't leave any
                // dangling around.
                String[] files = mDalvikCacheDir.list();
                if (files != null) {
                    for (int i=0; i
                        String fn = files[i];
                        if (fn.startsWith("data@app@")
                                || fn.startsWith("data@app-private@")) {
                            Slog.i(TAG, "Pruning dalvik file: " + fn);
                            (new File(mDalvikCacheDir, fn)).delete();
                        }
                    }
                }
            }

            // Find base frameworks (resource packages without code).
            mFrameworkInstallObserver = new AppDirObserver(//创建一个监察器监视/system/framework
                mFrameworkDir.getPath(), OBSERVER_EVENTS, true);
            mFrameworkInstallObserver.startWatching();
            scanDirLI(mFrameworkDir, PackageParser.PARSE_IS_SYSTEM//扫描该目录下的所有apk，进行安装
                    | PackageParser.PARSE_IS_SYSTEM_DIR,
                    scanMode | SCAN_NO_DEX, 0);//currentTime 为 0  SCAN_NO_DEX

            // Collect all system packages.
            mSystemAppDir = new File(Environment.getRootDirectory(), "app");
            mSystemInstallObserver = new AppDirObserver(//监视/system/app
                mSystemAppDir.getPath(), OBSERVER_EVENTS, true);
            mSystemInstallObserver.startWatching();
            scanDirLI(mSystemAppDir, PackageParser.PARSE_IS_SYSTEM  //扫描该目录下的所有apk，进行安装
                    | PackageParser.PARSE_IS_SYSTEM_DIR, scanMode, 0);

            // Collect all vendor packages.
            mVendorAppDir = new File("/vendor/app");
            mVendorInstallObserver = new AppDirObserver(//监视/vendor/app
                mVendorAppDir.getPath(), OBSERVER_EVENTS, true);
            mVendorInstallObserver.startWatching();
            scanDirLI(mVendorAppDir, PackageParser.PARSE_IS_SYSTEM //扫描该目录下的所有apk，进行安装
                    | PackageParser.PARSE_IS_SYSTEM_DIR, scanMode, 0);

            if (DEBUG_UPGRADE) Log.v(TAG, "Running installd update commands");
            mInstaller.moveFiles();

            // Prune any system packages that no longer exist.//去除不存在的系统packages
            final List possiblyDeletedUpdatedSystemApps = new ArrayList();
            if (!mOnlyCore) {
                Iterator psit = mSettings.mPackages.values().iterator();
                while (psit.hasNext()) {
                    PackageSetting ps = psit.next();

                    /*
                     * If this is not a system app, it can't be a
                     * disable system app.
                     */
                    if ((ps.pkgFlags & ApplicationInfo.FLAG_SYSTEM) == 0) {//系统app
                        continue;
                    }

                    /*
                     * If the package is scanned, it's not erased.
                     */
                    final PackageParser.Package scannedPkg = mPackages.get(ps.name);
                    if (scannedPkg != null) {
                        /*
                         * If the system app is both scanned and in the
                         * disabled packages list, then it must have been
                         * added via OTA. Remove it from the currently
                         * scanned package so the previously user-installed
                         * application can be scanned.
                         *///如果系统app刚被扫描并且在disabled列表，则它肯定是通过ota添加的，从当前扫描的package中移除它，所以以前用户安装的可以被扫描到
                        if (mSettings.isDisabledSystemPackageLPr(ps.name)) {
                            Slog.i(TAG, "Expecting better updatd system app for " + ps.name
                                    + "; removing system app");
                            removePackageLI(ps, true);
                        }

                        continue;
                    }

                    if (!mSettings.isDisabledSystemPackageLPr(ps.name)) {
                        psit.remove();
                        String msg = "System package " + ps.name
                                + " no longer exists; wiping its data";
                        reportSettingsProblem(Log.WARN, msg);
                        removeDataDirsLI(ps.name);
                    } else {
                        final PackageSetting disabledPs = mSettings.getDisabledSystemPkgLPr(ps.name);
                        if (disabledPs.codePath == null || !disabledPs.codePath.exists()) {
                            possiblyDeletedUpdatedSystemApps.add(ps.name);
                        }
                    }
                }
            }

            //look for any incomplete package installations未安装完全的package
            ArrayList deletePkgsList = mSettings.getListOfIncompleteInstallPackagesLPr();
            //clean up list
            for(int i = 0; i < deletePkgsList.size(); i++) {
                //clean up here
                cleanupInstallFailedPackage(deletePkgsList.get(i));//移除安装失败的package
            }
            //delete tmp files
            deleteTempPackageFiles();//移除临时文件

            if (!mOnlyCore) {
                EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_DATA_SCAN_START,
                        SystemClock.uptimeMillis());
                mAppInstallObserver = new AppDirObserver(
                    mAppInstallDir.getPath(), OBSERVER_EVENTS, false);
                mAppInstallObserver.startWatching();//监控/data/app目录
                scanDirLI(mAppInstallDir, 0, scanMode, 0);//扫描该目录下的package

                mDrmAppInstallObserver = new AppDirObserver( //DRM，英文全称Digital Rights Management, 可以翻译为：内容数字版权加密保护技术
                    mDrmAppPrivateInstallDir.getPath(), OBSERVER_EVENTS, false);
                mDrmAppInstallObserver.startWatching();//监控/data/app-private目录
                scanDirLI(mDrmAppPrivateInstallDir, PackageParser.PARSE_FORWARD_LOCK,//扫描该目录下的package
                        scanMode, 0);

                /**
                 * Remove disable package settings for any updated system
                 * apps that were removed via an OTA. If they're not a
                 * previously-updated app, remove them completely.
                 * Otherwise, just revoke their system-level permissions.
                 */
                for (String deletedAppName : possiblyDeletedUpdatedSystemApps) {
                    PackageParser.Package deletedPkg = mPackages.get(deletedAppName);
                    mSettings.removeDisabledSystemPackageLPw(deletedAppName);

                    String msg;
                    if (deletedPkg == null) {
                        msg = "Updated system package " + deletedAppName
                                + " no longer exists; wiping its data";
                        removeDataDirsLI(deletedAppName);
                    } else {
                        msg = "Updated system app + " + deletedAppName
                                + " no longer present; removing system privileges for "
                                + deletedAppName;

                        deletedPkg.applicationInfo.flags &= ~ApplicationInfo.FLAG_SYSTEM;

                        PackageSetting deletedPs = mSettings.mPackages.get(deletedAppName);
                        deletedPs.pkgFlags &= ~ApplicationInfo.FLAG_SYSTEM;
                    }
                    reportSettingsProblem(Log.WARN, msg);
                }
            } else {
                mAppInstallObserver = null;
                mDrmAppInstallObserver = null;
            }

            EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_SCAN_END,
                    SystemClock.uptimeMillis());
            Slog.i(TAG, "Time to scan packages: "
                    + ((SystemClock.uptimeMillis()-startTime)/1000f)
                    + " seconds");

            // If the platform SDK has changed since the last time we booted,
            // we need to re-grant app permission to catch any new ones that
            // appear.  This is really a hack, and means that apps can in some
            // cases get permissions that the user didn't initially explicitly
            // allow...  it would be nice to have some better way to handle
            // this situation.
            final boolean regrantPermissions = mSettings.mInternalSdkPlatform
                    != mSdkVersion;
            if (regrantPermissions) Slog.i(TAG, "Platform changed from "
                    + mSettings.mInternalSdkPlatform + " to " + mSdkVersion
                    + "; regranting permissions for internal storage");
            mSettings.mInternalSdkPlatform = mSdkVersion;

            updatePermissionsLPw(null, null, UPDATE_PERMISSIONS_ALL //赋予package相应请求的权限
                    | (regrantPermissions
                            ? (UPDATE_PERMISSIONS_REPLACE_PKG|UPDATE_PERMISSIONS_REPLACE_ALL)
                            : 0));

            // can downgrade to reader
            mSettings.writeLPr();//写/data/system/packages.xml

            EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_READY,
                    SystemClock.uptimeMillis());

            // Now after opening every single application zip, make sure they
            // are all flushed.  Not really needed, but keeps things nice and
            // tidy.
            Runtime.getRuntime().gc();

            mRequiredVerifierPackage = getRequiredVerifierLPr();
        } // synchronized (mPackages)
        } // synchronized (mInstallLock)
    }

PackageManagerService的初始化工作都是在它的构造函数中完成的，主要完成一下任务：

1、  添加一些用户id，如system、phone等;

2、   建立并启动PackageHandler消息循环，用于处理apk安装请求如adbinstall packageinstaller安装apk时就会发送消息;

3、  解析/system/etc/permission下的xml文件，主要是platform.xml,建立permission和gid之间的关系,可以 指定一个权限与几个组对应，当一个apk被授予这个权限时它也同时属于这几个组，readPermission(parser, perm);给一些底层用户分配一些权限，如shell授予各种permission，把一个权限赋予一个uid，当apk使用这个uid运行时，就具备 了这个权限系统增加的一些应用需要link的扩展的jar库，系统每增加一个硬件，都要添加相应的featrue,将解析结果放入 mAvailableFeatures;

4、  检查/data/system/packages.xml是否存在，里面记录了系统的ppermission,以及每个apk的 name,codePath,flags,ts,version,userid等，这些信息主要是通过apk安装的时候解析 AndroidManifest.xml获取到的，解析完apk后将更新信息写入这个文件并保存到flash，下次开机直接从里面读取相关信息添加到内存 相关列表中，当有apk安装，升级，删除时会更新这个文件；

5、  检查BootClassPath，mSharedLibraries及/system/framework下的jar是否需要dexopt,需要则通过dexopt进行优化,这里面主要是调用mInstaller.dexopt进行相应的优化；

6、  建立 java 层的 installer 与 c 层的 installd 的 socket 联接,使得在上层的 install,remove,dexopt等功能最终由installd在底层实现；

7、  启动AppDirObserver线程往中监测/system/framework,/system/app,/data/app/data/app- private目录的事件，主要监听add和remove事件，对于目录监听底层通过innotify机制实现，inotify是一种文件系统的变化通知 机制如文件增加、删除等事件可以立刻让用户态得知，它为用户态监视文件系统的变化提供了强大的支持，当有add event时调用scanPackageLI(File,int,int)处理，当有remove event时调用removePackageLI处理；

8、  调用scanDirLI启动apk解析，解析目录包括：/system/framework、/system/app、/vendor/app、/data/app、/data/app-private；

9、  移除临时文件；

10、 赋予package相应请求的权限；

11、 将解析出的Package的相关信息保存到相关全局变量，还有文件。

 

下面来分析前面每一步大概都做了些什么：

一、添加用户:

添加用户调用的是Settings的addSharedUserLPw

SharedUserSetting addSharedUserLPw(String name, int uid, int pkgFlags) {
       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);//新建一个SharedUserSetting结构
       s.userId = uid;
       if (addUserIdLPw(uid, s, name)) {//保存到mUserIds或mOtherUserIds
           mSharedUsers.put(name, s);//添加到mSharedUsers
           return s;
       }
       return null;

首先检查mSharedUsers中是否有这个用户，没有的话则新建一个SharedUserSetting，调用addUserIdLPw保存到mUserIds或mOtherUserIds，并添加到mSharedUsers。

private boolean addUserIdLPw(int uid, Object obj, Object name) {
      if (uid > Process.LAST_APPLICATION_UID) {//大于应用程序最大pid
          return false;
      }

      if (uid >= Process.FIRST_APPLICATION_UID) {//uid大于应用程序id的起始值
          int N = mUserIds.size();
          final int index = uid - Process.FIRST_APPLICATION_UID;
          while (index >= N) {//先添加元素，后面设置值
              mUserIds.add(null);
              N++;
          }
          if (mUserIds.get(index) != null) {
              PackageManagerService.reportSettingsProblem(Log.ERROR,
                      "Adding duplicate user id: " + uid
                      + " name=" + name);
              return false;
          }
          mUserIds.set(index, obj);//把该uid和对应的PackageSetting保存
      } else {//系统用户
          if (mOtherUserIds.get(uid) != null) {
              PackageManagerService.reportSettingsProblem(Log.ERROR,
                      "Adding duplicate shared id: " + uid
                      + " name=" + name);
              return false;
          }
          mOtherUserIds.put(uid, obj);//添加到mOtherUserIds
      }
      return true;
  }

二、建立并启动PackageHandler消息循环

PackageHandler用来处理安装apk等过程中的各种消息，后面降到apk安装的时候会涉及到。

这个比较简单，主要就新建一个PackageHandler，用来处理消息。

三、解析/system/etc/permission下的xml文件

主要是读取并解析/etc/permissions的xml文件，如我的平板上面：

看一下读取的流程：

相关代码：

void readPermissions() {//从/etc/permission读取权限配置信息
        // Read permissions from .../etc/permission directory.
        File libraryDir = new File(Environment.getRootDirectory(), "etc/permissions");
        if (!libraryDir.exists() || !libraryDir.isDirectory()) {
            Slog.w(TAG, "No directory " + libraryDir + ", skipping");
            return;
        }
        if (!libraryDir.canRead()) {
            Slog.w(TAG, "Directory " + libraryDir + " cannot be read");
            return;
        }

        // Iterate over the files in the directory and scan .xml files
        for (File f : libraryDir.listFiles()) {
            // We'll read platform.xml last
            if (f.getPath().endsWith("etc/permissions/platform.xml")) {
                continue;
            }

            if (!f.getPath().endsWith(".xml")) {
                Slog.i(TAG, "Non-xml file " + f + " in " + libraryDir + " directory, ignoring");
                continue;
            }
            if (!f.canRead()) {
                Slog.w(TAG, "Permissions library file " + f + " cannot be read");
                continue;
            }

            readPermissionsFromXml(f);
        }

        // Read permissions from .../etc/permissions/platform.xml last so it will take precedence
        final File permFile = new File(Environment.getRootDirectory(),
                "etc/permissions/platform.xml");//最后读取
        readPermissionsFromXml(permFile);
}

readPermissions先读取除platform.xml的其他文件，并调用readPermissionsFromXml进行解析,继续看一下readPermissionsFromXml

private void readPermissionsFromXml(File permFile) {
       FileReader permReader = null;
       try {
           permReader = new FileReader(permFile);
       } catch (FileNotFoundException e) {
           Slog.w(TAG, "Couldn't find or open permissions file " + permFile);
           return;
       }

       try {
           XmlPullParser parser = Xml.newPullParser();
           parser.setInput(permReader);

           XmlUtils.beginDocument(parser, "permissions");

           while (true) {
               XmlUtils.nextElement(parser);
               if (parser.getEventType() == XmlPullParser.END_DOCUMENT) {
                   break;
               }

               String name = parser.getName();
               if ("group".equals(name)) {
                   String gidStr = parser.getAttributeValue(null, "gid");
                   if (gidStr != null) {
                       int gid = Integer.parseInt(gidStr);
                       mGlobalGids = appendInt(mGlobalGids, gid);//保存到mGlobalGids
                   } else {
                       Slog.w(TAG, " without gid at "
                               + parser.getPositionDescription());
                   }

                   XmlUtils.skipCurrentTag(parser);
                   continue;
               } else if ("permission".equals(name)) {//定义了权限和组id（gid）的关系，该组拥有什么权限
                   String perm = parser.getAttributeValue(null, "name");//权限地名字
                   if (perm == null) {
                       Slog.w(TAG, " without name at "
                               + parser.getPositionDescription());
                       XmlUtils.skipCurrentTag(parser);
                       continue;
                   }
                   perm = perm.intern();
                   readPermission(parser, perm);//进一步解析,解析结果保存到 mSettings.mPermissions

               } else if ("assign-permission".equals(name)) {//那一个uid都拥有什么权限(把什么权限赋予哪个uid)
                   String perm = parser.getAttributeValue(null, "name");//获取权限名
                   if (perm == null) {
                       Slog.w(TAG, " without name at "
                               + parser.getPositionDescription());
                       XmlUtils.skipCurrentTag(parser);
                       continue;
                   }
                   String uidStr = parser.getAttributeValue(null, "uid");//获取用户名
                   if (uidStr == null) {
                       Slog.w(TAG, " without uid at "
                               + parser.getPositionDescription());
                       XmlUtils.skipCurrentTag(parser);
                       continue;
                   }
                   int uid = Process.getUidForName(uidStr);//该用户名对应的uid
                   if (uid < 0) {
                       Slog.w(TAG, " with unknown uid \""
                               + uidStr + "\" at "
                               + parser.getPositionDescription());
                       XmlUtils.skipCurrentTag(parser);
                       continue;
                   }
                   perm = perm.intern();
                   HashSet perms = mSystemPermissions.get(uid);//从mSystemPermissions查找是否已为该uid分配权限
                   if (perms == null) {
                       perms = new HashSet();
                       mSystemPermissions.put(uid, perms);//添加到mSystemPermissions
                   }
                   perms.add(perm);//添加 该权限
                   XmlUtils.skipCurrentTag(parser);

               } else if ("library".equals(name)) {//系统共享库
                   String lname = parser.getAttributeValue(null, "name");
                   String lfile = parser.getAttributeValue(null, "file");
                   if (lname == null) {
                       Slog.w(TAG, " without name at "
                               + parser.getPositionDescription());
                   } else if (lfile == null) {
                       Slog.w(TAG, " without file at "
                               + parser.getPositionDescription());
                   } else {
                       //Log.i(TAG, "Got library " + lname + " in " + lfile);
                       mSharedLibraries.put(lname, lfile);//添加到mSharedLibraries
                   }
                   XmlUtils.skipCurrentTag(parser);
                   continue;

               } else if ("feature".equals(name)) {//系统特征 (壁纸等)
                   String fname = parser.getAttributeValue(null, "name");
                   if (fname == null) {
                       Slog.w(TAG, " without name at "
                               + parser.getPositionDescription());
                   } else {
                       //Log.i(TAG, "Got feature " + fname);
                       FeatureInfo fi = new FeatureInfo();
                       fi.name = fname;
                       mAvailableFeatures.put(fname, fi);//添加到mAvailableFeatures
                   }
                   XmlUtils.skipCurrentTag(parser);
                   continue;

               } else {
                   XmlUtils.skipCurrentTag(parser);
                   continue;
               }

           }
           permReader.close();
       } catch (XmlPullParserException e) {
           Slog.w(TAG, "Got execption parsing permissions.", e);
       } catch (IOException e) {
           Slog.w(TAG, "Got execption parsing permissions.", e);
       }
   }

readPermissionsFromXml主要是:

1、读取permission name添加到mSettings.mPermissions
2、读取gid添加到mSettings.mPermissions

readPermissionsFromXml:

permission

a、读取permission name添加到mSettings.mPermissions

b、读取gid添加到mSettings.mPermissions

assign-permission

a、设置相应uid所具有的权限，保存到mSystemPermissions

 library

a、.jar包保存到mSharedLibraries

 feature

a、  硬件相关信息保存到mAvailableFeatures

 

我们来看一下platform.xml:

xml version="1.0" encoding="utf-8"?>





    <permission name="android.permission.READ_NETWORK_USAGE_HISTORY">
        <group gid="net_bw_stats" />
    permission>


    <permission name="android.permission.MODIFY_NETWORK_ACCOUNTING">
        <group gid="net_bw_acct" />
    permission>






    <assign-permission name="android.permission.WRITE_EXTERNAL_STORAGE" uid="shell" />
    <assign-permission name="android.permission.SEND_SMS" uid="shell" />
    <assign-permission name="android.permission.CALL_PHONE" uid="shell" />
    <assign-permission name="android.permission.READ_CONTACTS" uid="shell" />
    <assign-permission name="android.permission.WRITE_CONTACTS" uid="shell" />
    <assign-permission name="android.permission.READ_CALENDAR" uid="shell" />
    <assign-permission name="android.permission.WRITE_CALENDAR" uid="shell" />
    <assign-permission name="android.permission.READ_USER_DICTIONARY" uid="shell" />
    <assign-permission name="android.permission.WRITE_USER_DICTIONARY" uid="shell" />
    <assign-permission name="android.permission.ACCESS_FINE_LOCATION" uid="shell" />
    <assign-permission name="android.permission.ACCESS_COARSE_LOCATION" uid="shell" />
    <assign-permission name="android.permission.ACCESS_LOCATION_EXTRA_COMMANDS" uid="shell" />
    <assign-permission name="android.permission.ACCESS_NETWORK_STATE" uid="shell" />
    <assign-permission name="android.permission.ACCESS_WIFI_STATE" uid="shell" />
    <assign-permission name="android.permission.BLUETOOTH" uid="shell" />

    <assign-permission name="android.permission.GET_TASKS" uid="shell" />
    <assign-permission name="android.permission.CHANGE_CONFIGURATION" uid="shell" />
    <assign-permission name="android.permission.REORDER_TASKS" uid="shell" />
    <assign-permission name="android.permission.SET_ANIMATION_SCALE" uid="shell" />
    <assign-permission name="android.permission.SET_PREFERRED_APPLICATIONS" uid="shell" />
    <assign-permission name="android.permission.WRITE_SETTINGS" uid="shell" />
    <assign-permission name="android.permission.WRITE_SECURE_SETTINGS" uid="shell" />
    <assign-permission name="android.permission.BROADCAST_STICKY" uid="shell" />

    <assign-permission name="android.permission.SET_DEBUG_APP" uid="shell" />
    <assign-permission name="android.permission.SET_PROCESS_LIMIT" uid="shell" />
    <assign-permission name="android.permission.SET_ALWAYS_FINISH" uid="shell" />
    <assign-permission name="android.permission.DUMP" uid="shell" />
    <assign-permission name="android.permission.SIGNAL_PERSISTENT_PROCESSES" uid="shell" />
    <assign-permission name="android.permission.KILL_BACKGROUND_PROCESSES" uid="shell" />

    <assign-permission name="android.permission.FORCE_BACK" uid="shell" />
    <assign-permission name="android.permission.BATTERY_STATS" uid="shell" />
    <assign-permission name="android.permission.INTERNAL_SYSTEM_WINDOW" uid="shell" />
    <assign-permission name="android.permission.INJECT_EVENTS" uid="shell" />
    <assign-permission name="android.permission.RETRIEVE_WINDOW_CONTENT" uid="shell" />
    <assign-permission name="android.permission.SET_ACTIVITY_WATCHER" uid="shell" />
    <assign-permission name="android.permission.READ_INPUT_STATE" uid="shell" />
    <assign-permission name="android.permission.SET_ORIENTATION" uid="shell" />
    <assign-permission name="android.permission.INSTALL_PACKAGES" uid="shell" />
    <assign-permission name="android.permission.CLEAR_APP_USER_DATA" uid="shell" />
    <assign-permission name="android.permission.DELETE_CACHE_FILES" uid="shell" />
    <assign-permission name="android.permission.DELETE_PACKAGES" uid="shell" />
    <assign-permission name="android.permission.ACCESS_SURFACE_FLINGER" uid="shell" />
    <assign-permission name="android.permission.READ_FRAME_BUFFER" uid="shell" />
    <assign-permission name="android.permission.DEVICE_POWER" uid="shell" />
    <assign-permission name="android.permission.INSTALL_LOCATION_PROVIDER" uid="shell" />
    <assign-permission name="android.permission.BACKUP" uid="shell" />
    <assign-permission name="android.permission.FORCE_STOP_PACKAGES" uid="shell" />
    <assign-permission name="android.permission.STOP_APP_SWITCHES" uid="shell" />
    <assign-permission name="android.permission.ACCESS_CONTENT_PROVIDERS_EXTERNALLY" uid="shell" />
    <assign-permission name="android.permission.GRANT_REVOKE_PERMISSIONS" uid="shell" />
    <assign-permission name="android.permission.SET_KEYBOARD_LAYOUT" uid="shell" />
    <assign-permission name="android.permission.GET_DETAILED_TASKS" uid="shell" />
    <assign-permission name="android.permission.SET_SCREEN_COMPATIBILITY" uid="shell" />
    <assign-permission name="android.permission.READ_EXTERNAL_STORAGE" uid="shell" />
    <assign-permission name="android.permission.WRITE_EXTERNAL_STORAGE" uid="shell" />
    <assign-permission name="android.permission.INTERACT_ACROSS_USERS" uid="shell" />
    <assign-permission name="android.permission.INTERACT_ACROSS_USERS_FULL" uid="shell" />
    <assign-permission name="android.permission.MANAGE_USERS" uid="shell" />
    <assign-permission name="android.permission.BLUETOOTH_STACK" uid="shell" />

    <assign-permission name="android.permission.MODIFY_AUDIO_SETTINGS" uid="media" />
    <assign-permission name="android.permission.ACCESS_DRM" uid="media" />
    <assign-permission name="android.permission.ACCESS_SURFACE_FLINGER" uid="media" />
    <assign-permission name="android.permission.WAKE_LOCK" uid="media" />

    <assign-permission name="android.permission.ACCESS_SURFACE_FLINGER" uid="graphics" />

    
            
              
			  
			  
				
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