PackageManagerService启动

            Android的应用管理主要是通过PackageManagerService(PMS)来完成的。PackageManagerService服务负责各种APK包的安装，卸载，优化和查询。PMS在启动时会扫描所有APK文件和Jar包，然后把它们的信息读出来，保存在内存中，这样系统运行时就能迅速找到各种应用和组件的信息。扫描过程中如果遇到没有优化的文件，还要执行转换工作，将app文件从dex格式转换成oat格式(Android5.0以前转换为odex格式)。这一节主要是来了解PMS的启动流程。

# SystemServer.java
vate void startBootstrapServices() {
        // Wait for installd to finish starting up so that it has a chance to
        // create critical directories such as /data/user with the appropriate
        // permissions.  We need this to complete before we initialize other services.
        Installer installer = mSystemServiceManager.startService(Installer.class);

      // Activity manager runs the show.
        mActivityManagerService = mSystemServiceManager.startService(
                ActivityManagerService.Lifecycle.class).getService();
        mActivityManagerService.setSystemServiceManager(mSystemServiceManager);
        mActivityManagerService.setInstaller(installer);

// Start the package manager.
        Slog.i(TAG, "Package Manager");
        mPackageManagerService = PackageManagerService.main(mSystemContext, installer,
                mFactoryTestMode != FactoryTest.FACTORY_TEST_OFF, mOnlyCore);
        mFirstBoot = mPackageManagerService.isFirstBoot();
        mPackageManager = mSystemContext.getPackageManager();

}

 private void startOtherServices() {
    ......
    //启动MountService，后续PackageManager会需要使用
    mSystemServiceManager.startService(MOUNT_SERVICE_CLASS);
    mPackageManagerService.performBootDexOpt();
    ...... 
     mSystemServiceManager.startBootPhase(SystemService.PHASE_SYSTEM_SERVICES_READY);
    ......
    mPackageManagerService.systemReady();
}

# PMS 
public static final PackageManagerService main(Context context, Installer installer,
            boolean factoryTest, boolean onlyCore) {
        PackageManagerService m = new PackageManagerService(context, installer,
                factoryTest, onlyCore);
      //将pms服务注册到ServiceManager，这是binder服务的常规注册流程
        ServiceManager.addService("package", m);
        return m;
    }

         分析:该方法的主要功能创建PMS对象，并将其注册到ServiceManager.关于PMS对象的构造方法很长，分为以下几个部分,每个部分会输出相应的EventLog.

#1 

# BOOT_PROGRESS_PMS_START

EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_START,
        SystemClock.uptimeMillis());
mContext = context;
mFactoryTest = factoryTest;
mOnlyCore = onlyCore; //标记是否只加载核心服务
//对于eng版本则延迟执行dexopt操作
mLazyDexOpt = "eng".equals(SystemProperties.get("ro.build.type"));
mMetrics = new DisplayMetrics();
mSettings = new Settings(mPackages); //创建Settings对象

...

long dexOptLRUThresholdInMinutes;
if (mLazyDexOpt) {
    dexOptLRUThresholdInMinutes = 30; //对于eng版本，则只会对30分钟之内使用过的app执行dex优化
} else {
    dexOptLRUThresholdInMinutes = 7 * 24 * 60; //否则，用户一周内使用过的app执行dex优化
}
mDexOptLRUThresholdInMills = dexOptLRUThresholdInMinutes * 60 * 1000;
...

mInstaller = installer; //保存installer对象
mPackageDexOptimizer = new PackageDexOptimizer(this); //用于dex优化
//运行在”android.fg"线程的handler对象
mMoveCallbacks = new MoveCallbacks(FgThread.get().getLooper());

mOnPermissionChangeListeners = new OnPermissionChangeListeners(
        FgThread.get().getLooper());

...

//获取系统配置信息
SystemConfig systemConfig = SystemConfig.getInstance();
mGlobalGids = systemConfig.getGlobalGids();
mSystemPermissions = systemConfig.getSystemPermissions();
mAvailableFeatures = systemConfig.getAvailableFeatures();

创建Settings类

#Settings.java

 Settings(Context context) {
        this(context, Environment.getDataDirectory());
    }

    Settings(Context context, File dataDir) {
        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");
    }

分析:此处mSystemDir是指目录/data/system，在该目录有以下5个文件：1 packages.xml记录所有安装app的信息
2 packages-backup.xml 备份文件 3 packages-stopped.xml记录系统被强制停止的文件 4 packages-stopped-backup.xml 备份文件 5 packages.list 记录应用的数据信息

# SystemConfig.java
public static SystemConfig getInstance() {
        synchronized (SystemConfig.class) {
            if (sInstance == null) {
                sInstance = new SystemConfig();
            }
            return sInstance;
        }
    }

	 SystemConfig() {
        // Read configuration from system
        readPermissions(Environment.buildPath(
                Environment.getRootDirectory(), "etc", "sysconfig"), false);
        // Read configuration from the old permissions dir
        readPermissions(Environment.buildPath(
                Environment.getRootDirectory(), "etc", "permissions"), false);
        // Only read features from OEM config
        readPermissions(Environment.buildPath(
                Environment.getOemDirectory(), "etc", "sysconfig"), true);
        readPermissions(Environment.buildPath(
                Environment.getOemDirectory(), "etc", "permissions"), true);
    }

分析:readPermissions()解析指定目录下的所有xml文件，比如将标签<library>所指的动态库保存到 PKMS的成员变量mSharedLibraries。可见，SystemConfig创建过程是对以下这四个目录中的所有xml进行解析:1 /system/etc/sysconfig 2 /system/etc/permissions 3 /oem/etc/sysconfig 4 /oem/etc/permissions

#SystemConfig.java
 
 void readPermission(XmlPullParser parser, String name)
            throws IOException, XmlPullParserException {

        name = name.intern();

        PermissionEntry perm = mPermissions.get(name);
        if (perm == null) {
            perm = new PermissionEntry(name);
            mPermissions.put(name, perm);
        }
        int outerDepth = parser.getDepth();
        int type;
        while ((type=parser.next()) != XmlPullParser.END_DOCUMENT
               && (type != XmlPullParser.END_TAG
                       || parser.getDepth() > outerDepth)) {
            if (type == XmlPullParser.END_TAG
                    || type == XmlPullParser.TEXT) {
                continue;
            }

            String tagName = parser.getName();
            if ("group".equals(tagName)) {
                String gidStr = parser.getAttributeValue(null, "gid");
                if (gidStr != null) {
                    int gid = Process.getGidForName(gidStr);
                    perm.gids = appendInt(perm.gids, gid);
                } else {
                    Slog.w(TAG, "<group> without gid at "
                            + parser.getPositionDescription());
                }
            }
            XmlUtils.skipCurrentTag(parser);
        }
    }
}

分析: 该方法是解析指定目录下所有的具有可读权限的，且以xml后缀文件。

#PMS  #PMS_SYSTEM_SCAN_START
  
  long startTime = SystemClock.uptimeMillis();
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_SYSTEM_SCAN_START,
        startTime);

final int scanFlags = SCAN_NO_PATHS | SCAN_DEFER_DEX | SCAN_BOOTING | SCAN_INITIAL;
//该集合中存放的是已经优化或者不需要优先的文件
final ArraySet<String> alreadyDexOpted = new ArraySet<String>();

final String bootClassPath = System.getenv("BOOTCLASSPATH");
final String systemServerClassPath = System.getenv("SYSTEMSERVERCLASSPATH");

//将环境变量BOOTCLASSPATH所执行的文件加入alreadyDexOpted
if (bootClassPath != null) {
    String[] bootClassPathElements = splitString(bootClassPath, ':');
    for (String element : bootClassPathElements) {
        alreadyDexOpted.add(element);
    }
}

//将环境变量SYSTEMSERVERCLASSPATH所执行的文件加入alreadyDexOpted
if (systemServerClassPath != null) {
    String[] systemServerClassPathElements = splitString(systemServerClassPath, ':');
    for (String element : systemServerClassPathElements) {
        alreadyDexOpted.add(element);
    }
}
...

//此处共享库是由SystemConfig实例化过程赋值的
if (mSharedLibraries.size() > 0) {
    for (String dexCodeInstructionSet : dexCodeInstructionSets) {
        for (SharedLibraryEntry libEntry : mSharedLibraries.values()) {
            final String lib = libEntry.path;
            ...
            int dexoptNeeded = DexFile.getDexOptNeeded(lib, dexCodeInstructionSet,
                    "speed", false);
            if (dexoptNeeded != DexFile.NO_DEXOPT_NEEDED) {
                alreadyDexOpted.add(lib);
                //执行dexopt操作
                mInstaller.dexopt(lib, Process.SYSTEM_UID, dexCodeInstructionSet,
                        dexoptNeeded, DEXOPT_PUBLIC /*dexFlags*/);
            }
        }
    }
}

//此处frameworkDir目录为/system/framework
File frameworkDir = new File(Environment.getRootDirectory(), "framework");

//添加以下两个文件添加到已优化集合
alreadyDexOpted.add(frameworkDir.getPath() + "/framework-res.apk");
alreadyDexOpted.add(frameworkDir.getPath() + "/core-libart.jar");

String[] frameworkFiles = frameworkDir.list();
if (frameworkFiles != null) {
    for (String dexCodeInstructionSet : dexCodeInstructionSets) {
        for (int i=0; i<frameworkFiles.length; i++) {
            File libPath = new File(frameworkDir, frameworkFiles[i]);
            String path = libPath.getPath();
            //跳过已优化集合中的文件
            if (alreadyDexOpted.contains(path)) {
                continue;
            }
            //跳过后缀不为apk和jar的文件
            if (!path.endsWith(".apk") && !path.endsWith(".jar")) {
                continue;
            }

            int dexoptNeeded = DexFile.getDexOptNeeded(path, dexCodeInstructionSet,
                    "speed", false);
            if (dexoptNeeded != DexFile.NO_DEXOPT_NEEDED) {
                //执行dexopt操作
                mInstaller.dexopt(path, Process.SYSTEM_UID, dexCodeInstructionSet,
                        dexoptNeeded, DEXOPT_PUBLIC /*dexFlags*/);
            }

        }
    }
}

final VersionInfo ver = mSettings.getInternalVersion();
mIsUpgrade = !Build.FINGERPRINT.equals(ver.fingerprint);
mPromoteSystemApps = mIsUpgrade && ver.sdkVersion <= Build.VERSION_CODES.LOLLIPOP_MR1;

if (mPromoteSystemApps) {
    Iterator<PackageSetting> pkgSettingIter = mSettings.mPackages.values().iterator();
    while (pkgSettingIter.hasNext()) {
        PackageSetting ps = pkgSettingIter.next();
        if (isSystemApp(ps)) {
            mExistingSystemPackages.add(ps.name);
        }
    }
}

//收集供应商包名：/vendor/overlay
File vendorOverlayDir = new File(VENDOR_OVERLAY_DIR);
scanDirLI(vendorOverlayDir, PackageParser.PARSE_IS_SYSTEM
        | PackageParser.PARSE_IS_SYSTEM_DIR, scanFlags | SCAN_TRUSTED_OVERLAY, 0);

//收集包名：/system/framework
scanDirLI(frameworkDir, PackageParser.PARSE_IS_SYSTEM
        | PackageParser.PARSE_IS_SYSTEM_DIR
        | PackageParser.PARSE_IS_PRIVILEGED,
        scanFlags | SCAN_NO_DEX, 0);

//收集私有的系统包名：/system/priv-app
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);

//收集一般地系统包名：/system/app
final File systemAppDir = new File(Environment.getRootDirectory(), "app");
scanDirLI(systemAppDir, PackageParser.PARSE_IS_SYSTEM
        | PackageParser.PARSE_IS_SYSTEM_DIR, scanFlags, 0);

//收集私有供应商包名：/vendor/priv-app
final File privilegedVendorAppDir = new File(Environment.getVendorDirectory(), "priv-app");
scanDirLI(privilegedVendorAppDir, PackageParser.PARSE_IS_SYSTEM
        | PackageParser.PARSE_IS_SYSTEM_DIR
        | PackageParser.PARSE_IS_PRIVILEGED, scanFlags, 0);

//收集所有的供应商包名：/vendor/app
File vendorAppDir = new File(Environment.getVendorDirectory(), "app");
vendorAppDir = vendorAppDir.getCanonicalFile();
scanDirLI(vendorAppDir, PackageParser.PARSE_IS_SYSTEM
        | PackageParser.PARSE_IS_SYSTEM_DIR, scanFlags, 0);

//收集所有OEM包名：/oem/app
final File oemAppDir = new File(Environment.getOemDirectory(), "app");
scanDirLI(oemAppDir, PackageParser.PARSE_IS_SYSTEM
        | PackageParser.PARSE_IS_SYSTEM_DIR, scanFlags, 0);

//移除文件
mInstaller.moveFiles();

//删除不在存在的系统包
final List<String> possiblyDeletedUpdatedSystemApps = new ArrayList<String>();
if (!mOnlyCore) {
    Iterator<PackageSetting> psit = mSettings.mPackages.values().iterator();
    while (psit.hasNext()) {
        PackageSetting ps = psit.next();

        if ((ps.pkgFlags & ApplicationInfo.FLAG_SYSTEM) == 0) {
            continue;
        }

        final PackageParser.Package scannedPkg = mPackages.get(ps.name);
        if (scannedPkg != null) {
            if (mSettings.isDisabledSystemPackageLPr(ps.name)) {
                removePackageLI(ps, true);
                mExpectingBetter.put(ps.name, ps.codePath);
            }
            continue;
        }

        if (!mSettings.isDisabledSystemPackageLPr(ps.name)) {
            psit.remove();
            removeDataDirsLI(null, ps.name);
        } else {
            final PackageSetting disabledPs = mSettings.getDisabledSystemPkgLPr(ps.name);
            if (disabledPs.codePath == null || !disabledPs.codePath.exists()) {
                possiblyDeletedUpdatedSystemApps.add(ps.name);
            }
        }
    }
}

//清理所有安装不完整的包
ArrayList<PackageSetting> deletePkgsList = mSettings.getListOfIncompleteInstallPackagesLPr();
for(int i = 0; i < deletePkgsList.size(); i++) {
    cleanupInstallFailedPackage(deletePkgsList.get(i));
}
//删除临时文件
deleteTempPackageFiles();

//移除不相干包中的所有共享userID
mSettings.pruneSharedUsersLPw();

# InstallerConnection.java

public int dexopt(String apkPath, int uid, String instructionSet, int dexoptNeeded, int dexFlags) {
    return dexopt(apkPath, uid, "*", instructionSet, dexoptNeeded,
            null, dexFlags);
}

public int dexopt(String apkPath, int uid, String pkgName, String instructionSet, int dexoptNeeded, String outputPath, int dexFlags) {
   StringBuilder builder = new StringBuilder("dexopt");
   builder.append(' ');
   builder.append(apkPath);
   builder.append(' ');
   builder.append(uid);
   builder.append(' ');
   builder.append(pkgName);
   builder.append(' ');
   builder.append(instructionSet);
   builder.append(' ');
   builder.append(dexoptNeeded);
   builder.append(' ');
   builder.append(outputPath != null ? outputPath : "!");
   builder.append(' ');
   builder.append(dexFlags);
   return execute(builder.toString());    }

分析:通过socket发送给installd守护进程来执行相应的dexopt操作。

# PMS # PMS_DATA_SCAN_START

if (!mOnlyCore) { //处理非系统app
    EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_DATA_SCAN_START, SystemClock.uptimeMillis());
    //收集/data/app包名
    scanDirLI(mAppInstallDir, 0, scanFlags | SCAN_REQUIRE_KNOWN, 0);
    //收集/data/app-private包名
    scanDirLI(mDrmAppPrivateInstallDir, PackageParser.PARSE_FORWARD_LOCK,
            scanFlags | SCAN_REQUIRE_KNOWN, 0);

    for (String deletedAppName : possiblyDeletedUpdatedSystemApps) {
        PackageParser.Package deletedPkg = mPackages.get(deletedAppName);
        mSettings.removeDisabledSystemPackageLPw(deletedAppName);

        String msg;
        if (deletedPkg == null) {
            removeDataDirsLI(null, deletedAppName);
        } else {
            deletedPkg.applicationInfo.flags &= ~ApplicationInfo.FLAG_SYSTEM;

            PackageSetting deletedPs = mSettings.mPackages.get(deletedAppName);
            deletedPs.pkgFlags &= ~ApplicationInfo.FLAG_SYSTEM;
        }
    }

    for (int i = 0; i < mExpectingBetter.size(); i++) {
        final String packageName = mExpectingBetter.keyAt(i);
        if (!mPackages.containsKey(packageName)) {
            final File scanFile = mExpectingBetter.valueAt(i);

            final int reparseFlags;
            if (FileUtils.contains(privilegedAppDir, scanFile)) {
                reparseFlags = PackageParser.PARSE_IS_SYSTEM
                        | PackageParser.PARSE_IS_SYSTEM_DIR
                        | PackageParser.PARSE_IS_PRIVILEGED;
            } else if (FileUtils.contains(systemAppDir, scanFile)) {
                reparseFlags = PackageParser.PARSE_IS_SYSTEM
                        | PackageParser.PARSE_IS_SYSTEM_DIR;
            } else if (FileUtils.contains(vendorAppDir, scanFile)) {
                reparseFlags = PackageParser.PARSE_IS_SYSTEM
                        | PackageParser.PARSE_IS_SYSTEM_DIR;
            } else if (FileUtils.contains(oemAppDir, scanFile)) {
                reparseFlags = PackageParser.PARSE_IS_SYSTEM
                        | PackageParser.PARSE_IS_SYSTEM_DIR;
            } else {
                continue;
            }

            mSettings.enableSystemPackageLPw(packageName);

            try {
                // 扫描包名
                scanPackageLI(scanFile, reparseFlags, scanFlags, 0, null);
            } catch (PackageManagerException e) {
                ...
            }
        }
    }
}
mExpectingBetter.clear();

updateAllSharedLibrariesLPw();

for (SharedUserSetting setting : mSettings.getAllSharedUsersLPw()) {
    adjustCpuAbisForSharedUserLPw(setting.packages, null /* scanned package */,
            false /* force dexopt */, false /* defer dexopt */,
            false /* boot complete */);
}

mPackageUsage.readLP();

# PMS # PMS_SCAN_END


ventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_SCAN_END,
        SystemClock.uptimeMillis());

int updateFlags = UPDATE_PERMISSIONS_ALL;
if (ver.sdkVersion != mSdkVersion) {
    updateFlags |= UPDATE_PERMISSIONS_REPLACE_PKG | UPDATE_PERMISSIONS_REPLACE_ALL;
}
//当sdk版本不一致时，需要更新权限
updatePermissionsLPw(null, null, StorageManager.UUID_PRIVATE_INTERNAL, updateFlags);
ver.sdkVersion = mSdkVersion;

if (!onlyCore && (mPromoteSystemApps || !mRestoredSettings)) {
    for (UserInfo user : sUserManager.getUsers(true)) {
        mSettings.applyDefaultPreferredAppsLPw(this, user.id);
        applyFactoryDefaultBrowserLPw(user.id);
        primeDomainVerificationsLPw(user.id);
    }
}

//当这是ota后的首次启动，正常启动则需要清除目录的缓存代码
if (mIsUpgrade && !onlyCore) {
    for (int i = 0; i < mSettings.mPackages.size(); i++) {
        final PackageSetting ps = mSettings.mPackages.valueAt(i);
        if (Objects.equals(StorageManager.UUID_PRIVATE_INTERNAL, ps.volumeUuid)) {
            deleteCodeCacheDirsLI(ps.volumeUuid, ps.name);
        }
    }
    ver.fingerprint = Build.FINGERPRINT;
}

checkDefaultBrowser();
//当权限和其他默认项都完成更新，则清理相关信息
mExistingSystemPackages.clear();
mPromoteSystemApps = false;

ver.databaseVersion = Settings.CURRENT_DATABASE_VERSION;
//信息写回packages.xml文件
mSettings.writeLPr();

#PMS  # PMS_READY

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

mRequiredVerifierPackage = getRequiredVerifierLPr();
mRequiredInstallerPackage = getRequiredInstallerLPr();
mInstallerService = new PackageInstallerService(context, this);

mIntentFilterVerifierComponent = getIntentFilterVerifierComponentNameLPr();
mIntentFilterVerifier = new IntentVerifierProxy(mContext,
        mIntentFilterVerifierComponent);

# PackageInstallerService
public PackageInstallerService(Context context, PackageManagerService pm) {
    mContext = context;
    mPm = pm;
    mInstallThread = new HandlerThread(TAG);
    mInstallThread.start();

    mInstallHandler = new Handler(mInstallThread.getLooper());

    mCallbacks = new Callbacks(mInstallThread.getLooper());

    mSessionsFile = new AtomicFile(
            new File(Environment.getSystemSecureDirectory(), "install_sessions.xml"));
    mSessionsDir = new File(Environment.getSystemSecureDirectory(), "install_sessions");
    mSessionsDir.mkdirs();

    synchronized (mSessions) {
        readSessionsLocked();

        reconcileStagesLocked(StorageManager.UUID_PRIVATE_INTERNAL);

        final ArraySet<File> unclaimedIcons = newArraySet(
                mSessionsDir.listFiles());

        for (int i = 0; i < mSessions.size(); i++) {
            final PackageInstallerSession session = mSessions.valueAt(i);
            unclaimedIcons.remove(buildAppIconFile(session.sessionId));
        }

        for (File icon : unclaimedIcons) {
            icon.delete();
        }
    }
}		

总结:PKMS初始化过程，分为5个阶段：
1 PMS_START阶段：1.1 创建Settings对象；1.2 将6类shareUserId到mSettings；1.3 初始化SystemConfig；1.4 创建名为“PackageManager”的handler线程mHandlerThread;1.5 创建UserManagerService多用户管理服务；1.6 通过解析4大目录中的xmL文件构造共享mSharedLibraries；
2 PMS_SYSTEM_SCAN_START阶段：2.1 mSharedLibraries共享库中的文件执行dexopt操作；2.2 system/framework目录中满足条件的apk或jar文件执行dexopt操作；2.3 扫描系统apk;
3 PMS_DATA_SCAN_START阶段：3.1 扫描/data/app目录下的apk;3.2 扫描/data/app-private目录下的apk;
4 PMS_SCAN_END阶段：4.1 将上述信息写回/data/system/packages.xml;
5 PMS_READY阶段：5.1 创建服务PackageInstallerService；