android PakageManagerService启动流程分析详解手机开发

PakageManagerService的启动流程图

_2016_10_12_10_58_13

1.PakageManagerService概述

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。后面PakageManagerService简称PMS。

2.SystemServer启动PackageManagerService

我之前的ATA文章有说到,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启动PMS关键源码如下:

 
    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(); 
      //... 
    }  
 

关键点

  • PMS的main函数,该函数是PKM的核心。

3.PMS的main方法

PackageManagerService的主要功能是,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。例如PKMS解析APK包中的AndroidMainfest.xml,并根据其中声明的Activity标签来创建对应的对象并加以保管。PMS的main方法的代码如下:

 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; 
 } 
 

该方法看似很简单,只有几行代码,然而执行事件却比较长,这是因为PMS在其构造函数中做了很多的“重体力活”,这也是android启动速度慢的主要因素之一。安装的应用越多,系统启动开机时间越长。
PMS构造函数的主要工作流程

  • 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。

4.PMS的前期准备工作

4.1探究Setting

 
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; 
        //是否在工厂测试模式下,假定为false 
        mFactoryTest = factoryTest; 
        mOnlyCore = onlyCore; 
        //如果此系统是“eng”版,扫描Package后,不对package做dex优化 
        mLazyDexOpt = "eng".equals(SystemProperties.get("ro.build.type")); 
        //用于存储与显示屏相关的一些属性,例如屏幕的宽高分辨率等。 
        mMetrics = new DisplayMetrics(); 
        mSettings = new Settings(mPackages); 
        //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.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); 
 
4.1.1Android系统中UID/GID

UID为用户ID的缩写,GID为用户组ID的缩写,这两个概念均与Linux系统中进程的权限管理有关。一般来说,每一个进程都有一个对应的UID,表示该进程属于哪个用户,不同用户有不同权限。一个进程也可分属不同的用户组,每个用户组都有对应的权限。
在android系统中,系统定义的UID/GID在Process.java文件中,关键源码如下所示

 
    /** 
     * Defines the UID/GID under which system code runs. 
     */ 
    public static final int SYSTEM_UID = 1000; 
 
    /** 
     * Defines the UID/GID under which the telephony code runs. 
     */ 
    public static final int PHONE_UID = 1001; 
 
    /** 
     * Defines the UID/GID for the user shell. 
     * @hide 
     */ 
    public static final int SHELL_UID = 2000; 
 
    /** 
     * Defines the UID/GID for the log group. 
     * @hide 
     */ 
    public static final int LOG_UID = 1007; 
 
    /** 
     * Defines the UID/GID for the WIFI supplicant process. 
     * @hide 
     */ 
    public static final int WIFI_UID = 1010; 
 
    /** 
     * Defines the UID/GID for the mediaserver process. 
     * @hide 
     */ 
    public static final int MEDIA_UID = 1013; 
 
    /** 
     * Defines the UID/GID for the DRM process. 
     * @hide 
     */ 
    public static final int DRM_UID = 1019; 
 
    /** 
     * Defines the UID/GID for the group that controls VPN services. 
     * @hide 
     */ 
    public static final int VPN_UID = 1016; 
 
    /** 
     * Defines the UID/GID for the NFC service process. 
     * @hide 
     */ 
    public static final int NFC_UID = 1027; 
 
    /** 
     * Defines the UID/GID for the Bluetooth service process. 
     * @hide 
     */ 
    public static final int BLUETOOTH_UID = 1002; 
 
    /** 
     * Defines the GID for the group that allows write access to the internal media storage. 
     * @hide 
     */ 
    public static final int MEDIA_RW_GID = 1023; 
 
    /** 
     * Access to installed package details 
     * @hide 
     */ 
    public static final int PACKAGE_INFO_GID = 1032; 
 
    /** 
     * Defines the UID/GID for the shared RELRO file updater process. 
     * @hide 
     */ 
    public static final int SHARED_RELRO_UID = 1037; 
 
    /** 
     * Defines the start of a range of UIDs (and GIDs), going from this 
     * number to {@link #LAST_APPLICATION_UID} that are reserved for assigning 
     * to applications. 
     */ 
    public static final int FIRST_APPLICATION_UID = 10000; 
 
    /** 
     * Last of application-specific UIDs starting at 
     * {@link #FIRST_APPLICATION_UID}. 
     */ 
    public static final int LAST_APPLICATION_UID = 19999; 
 
    /** 
     * First uid used for fully isolated sandboxed processes (with no permissions of their own) 
     * @hide 
     */ 
    public static final int FIRST_ISOLATED_UID = 99000; 
 
    /** 
     * Last uid used for fully isolated sandboxed processes (with no permissions of their own) 
     * @hide 
     */ 
    public static final int LAST_ISOLATED_UID = 99999; 
4.1.2 探究SharedUserSetting

Setting中有一个mShareUsers成员,该成员存储的是字符串变量name与SharedUserSetting健值对。

 
SharedUserSetting addSharedUserLPw(String name, int uid, int pkgFlags, int pkgPrivateFlags) { 
        //mSharedUsers是一个HashMap.key为字符串,值为ShareUserSetting对象 
        SharedUserSetting s = mSharedUsers.get(name); 
        if (s != null) { 
            if (s.userId == uid) { 
                return s; 
            } 
           //... 
                       return null; 
        } 
        创建一个SharedUserSetting对象,并设置为userid为uid 
        s = new SharedUserSetting(name, pkgFlags, pkgPrivateFlags); 
        s.userId = uid; 
        if (addUserIdLPw(uid, s, name)) { 
            mSharedUsers.put(name, s); 
            return s; 
        } 
        return null; 
    } 
 

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

  • 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

接下来分析addUserIdLPw的功能,它主要就是将SharedUserSettings对象保存到对应的数组中,代码如下

private boolean addUserIdLPw(int uid, Object obj, Object name) { 
        //uid不能超出限制,Android对uid进行归纳,系统APK所在进程小于10000 
        //应用APK所在进程的uid从10000开始 
        if (uid > Process.LAST_APPLICATION_UID) { 
            return false; 
        } 
        //FIRST_APPLICATION_UID = 10000,属于应用APK 
        if (uid >= Process.FIRST_APPLICATION_UID) { 
            int N = mUserIds.size(); 
            //计算索引,其值是uid和FIRST_APPLICATION_UID的差 
            final int index = uid - Process.FIRST_APPLICATION_UID; 
            while (index >= N) { 
                mUserIds.add(null); 
                N++; 
            } 
            //如果索引位置不为空,返回 
            if (mUserIds.get(index) != null) { 
                PackageManagerService.reportSettingsProblem(Log.ERROR, 
                        "Adding duplicate user id: " + uid 
                        + " name=" + name); 
                return false; 
            } 
            //mUserIds保存应用Package的uid,obj是SharedUserSettings 
            mUserIds.set(index, obj); 
        } else { 
            if (mOtherUserIds.get(uid) != null) { 
                PackageManagerService.reportSettingsProblem(Log.ERROR, 
                        "Adding duplicate shared id: " + uid 
                                + " name=" + name); 
                return false; 
            } 
            mOtherUserIds.put(uid, obj); 
        } 
        return true; 
    } 
 

4.2 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,将其存放到PKM中,关键源码如下:

        // 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。 
            //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(); 
 

进一步我们再观察SystemConfig是如何解析系统权限xml文件的,在SystemConfig的构造函数中,它会去分别读取etc目录下的sysconfig,permissions,sysconfig目录下的文件。

        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); 
    } 

我们看看到底这些目录下放着什么样的文件,例如/etc/permissions目录下的文件如下图:
Screenshot_2016_10_10_15_35_50

我们再打开第一个文件来探究,没错,这个文件代表蓝牙权限,表示该设备支持蓝牙。具体代码如下

<?xml version="1.0" encoding="utf-8"?> 
 
<permissions> 
    <feature name="android.hardware.bluetooth" /> 
</permissions> 
 

总结一下PMS的前期工作,其实就是扫描并解析XML文件,将其中的信息保存到特定的数据结构中。

5.PMS扫描Package

第二个阶段的工作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。

5.1系统库的dex优化

以下的代码主要是对系统库BOOTCLASSPATH指定,或platform.xml定义,或者/system/frameworks目录下的jar
和apk包进行一次检查,该dex优化的优化.dex优化后会在相应的目录生成.odex文件。/system/frameworks如下图:
Screenshot_2016_10_11_19_12_30
Screenshot_2016_10_11_19_41_03
关键源码如下:

            // Set flag to monitor and not change apk file paths when 
            // scanning install directories. 
            //定义扫描参数 
            final int scanFlags = SCAN_NO_PATHS | SCAN_DEFER_DEX | SCAN_BOOTING | SCAN_INITIAL; 
            //用于存储已经dex优化过或者不需要优化的包 
            final ArraySet<String> alreadyDexOpted = new ArraySet<String>(); 
 
            /** 
             * Add everything in the in the boot class path to the 
             * list of process files because dexopt will have been run 
             * if necessary during zygote startup. 
             */ 
             //获取java启动类库的路径,在init.rc文件中通过BOOTCLASSPATH环境变量输出 
             //主要是/system/framework/下的系统jar包 
            final String bootClassPath = System.getenv("BOOTCLASSPATH"); 
            final String systemServerClassPath = System.getenv("SYSTEMSERVERCLASSPATH"); 
            if (bootClassPath != null) { 
                String[] bootClassPathElements = splitString(bootClassPath, ':'); 
                //循环遍历/system/framework/下的系统jar包的绝对路径,添加到alreadyDexOpted 
                for (String element : bootClassPathElements) { 
                    alreadyDexOpted.add(element); 
                } 
            }  
            if (mSharedLibraries.size() > 0) { 
                //... 
                 if (dexoptNeeded != DexFile.NO_DEXOPT_NEEDED) { 
                                alreadyDexOpted.add(lib); 
                                //dex优化 
                                mInstaller.dexopt(lib, Process.SYSTEM_UID, true, dexCodeInstructionSet, dexoptNeeded);         
 
                } 
            } 
 
            //... 
 
            File frameworkDir = new File(Environment.getRootDirectory(), "framework"); 
            //framework-res.apk定义了系统常用的资源,还有几个重要的Activity,如长按Power键弹出选择框 
            //不需要dex优化 
            alreadyDexOpted.add(frameworkDir.getPath() + "/framework-res.apk"); 
 
            alreadyDexOpted.add(frameworkDir.getPath() + "/core-libart.jar"); 
 
            //扫描framework/下的apk或者jar进行dex优化 
            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(); 
                        // 跳过已经存在的包 
                        if (alreadyDexOpted.contains(path)) { 
                            continue; 
                        } 
                        // 不是apk或者jar的不做处理 
                        if (!path.endsWith(".apk") && !path.endsWith(".jar")) { 
                            continue; 
                        } 
                        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); 
                            } 
 
                    } 
                } 
            } 
 

5.2扫描系统的APK

对apk或者jar进行dex优化后,现在PKM进入了重点阶段,扫描系统的APK,每一个APK对应一个Package对象,主要是扫描APK的AndroidManifest.xml,解析application标签及其子标签actvity、service、recever等,也就是android的四大组件,解析后将它们保存到Package对应的数据结构中,最后将它们注册到PKM中,要扫描以下几个目录:

  • /system/frameworks:该目录下的文件都是系统库,例如service.jar、framework.jar、framework-res.apk。不过只扫描framework-res.apk文件
  • /system/app:该目录下全是默认的系统应用和厂商特定的APK文件,例如Buletooth.apk、和SystemUI.apk等

解析AndroidManifest.xml关键的源码如下:

private Package parseBaseApk(Resources res, XmlResourceParser parser, int flags, 
            String[] outError) throws XmlPullParserException, IOException { 
 
             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(); 
            //解析<application> 
            if (tagName.equals("application")) { 
                if (foundApp) { 
                    if (RIGID_PARSER) { 
                        outError[0] = "<manifest> has more than one <application>"; 
                        mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED; 
                        return null; 
                    } else { 
                        Slog.w(TAG, "<manifest> has more than one <application>"); 
                        XmlUtils.skipCurrentTag(parser); 
                        continue; 
                    } 
                } 
 
                foundApp = true; 
                //解析<application>及其子标签 
                if (!parseBaseApplication(pkg, res, parser, attrs, flags, outError)) { 
                    return null; 
                } 
            //解析<application> 
            } else if (tagName.equals("overlay")) { 
 
            } else if (tagName.equals("key-sets")) { 
 
            } else if (tagName.equals("permission-group")) { 
 
            } else if (tagName.equals("permission")) { 
 
            } else if (tagName.equals("permission-tree")) { 
            //解析<uses-permission> 
            } else if (tagName.equals("uses-permission")) { 
 
            } else if (tagName.equals("uses-permission-sdk-m") 
                    || tagName.equals("uses-permission-sdk-23")) { 
 
            } else if (tagName.equals("uses-configuration")) { 
 
            } else if (tagName.equals("uses-feature")) { 
 
            } else if (tagName.equals("feature-group")) { 
 
            } else if (tagName.equals("uses-sdk")) { 
 
            } else if (tagName.equals("supports-screens")) { 
 
            } else if (tagName.equals("instrumentation")) { 
 
            } else if (tagName.equals("original-package")) { 
 
            } else if (tagName.equals("adopt-permissions")) { 
 
            } else if (tagName.equals("uses-gl-texture")) { 
 
            } else if (tagName.equals("compatible-screens")) { 
 
            } else if (tagName.equals("supports-input")) { 
 
            } else if (tagName.equals("eat-comment")) { 
 
            } else if (RIGID_PARSER) { 
 
 
            } else { 
 
            } 
        } 
} 

具体看一下怎么解析application标签下的四大组件的,依次解析activity,receiver,service,provider,其中可以发现,receiver被当成activity来解析了,PKM通过PackageParser类将解析后的四大组件保存到对应数据结构中,也就是存放到PackageParser的activities,receivers,providers,services对象中。关键源码如下:

private boolean parseBaseApplication(Package owner, Resources res, 
            XmlPullParser parser, AttributeSet attrs, int flags, String[] outError){ 
            //... 
 while ((type = parser.next()) != XmlPullParser.END_DOCUMENT 
                && (type != XmlPullParser.END_TAG || parser.getDepth() > innerDepth)) { 
            if (type == XmlPullParser.END_TAG || type == XmlPullParser.TEXT) { 
                continue; 
            } 
 
            String tagName = parser.getName(); 
            //activity标签 
            if (tagName.equals("activity")) { 
                //解析activity标签 
                Activity a = parseActivity(owner, res, parser, attrs, flags, outError, false, 
                        owner.baseHardwareAccelerated); 
                //添加activity到owner.activities中 
                owner.activities.add(a); 
            //receiver标签 
            } else if (tagName.equals("receiver")) { 
                //解析receiver标签,receiver其实被当成Activity来解析了。 
                Activity a = parseActivity(owner, res, parser, attrs, flags, outError, true, false); 
                if (a == null) { 
                    mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED; 
                    return false; 
                } 
            //添加activity到owner.activities中 
                owner.receivers.add(a); 
            //service标签 
            } else if (tagName.equals("service")) { 
                //解析service标签 
                Service s = parseService(owner, res, parser, attrs, flags, outError); 
                if (s == null) { 
                    mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED; 
                    return false; 
                } 
            //添加service到owner.services中 
                owner.services.add(s); 
            //provider标签 
            } else if (tagName.equals("provider")) { 
                Provider p = parseProvider(owner, res, parser, attrs, flags, outError); 
                if (p == null) { 
                    mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED; 
                    return false; 
                } 
 
                owner.providers.add(p); 
 
            } else if (tagName.equals("activity-alias")) { 
            } else if (parser.getName().equals("meta-data")) { 
 
            } else if (tagName.equals("uses-library")) { 
 
 
            } else if (tagName.equals("uses-package")) { 
            } 
        }             
} 

在PackageParser扫描完一个APK后,此时系统已经根据APK中的AndroidMainifest.xml,创建了一个Package对象,下一步是将该Package加入到系统中。此时调用scanPackageDirtyLI方法,scanPackageDirtyLI首先会对packageName为“android”的apk做单独的处理,该apk其实就是framework-res.apk,它包含了几个常见的activity

  • ChooserActivity:当startActivity有多个Acitvity符合时,系统会弹出此Acitivity,由用户选择合适的应用来处理
  • ShutDownActivity:关机前弹出的选择对话框
  • RingtonePickerAcitivity:铃声选择Activity

scanPackageDirtyLI关键代码如下:

private PackageParser.Package scanPackageDirtyLI(PackageParser.Package pkg, int parseFlags, 
            int scanFlags, long currentTime, UserHandle user) throws PackageManagerException { 
        final File scanFile = new File(pkg.codePath); 
        if (pkg.applicationInfo.getCodePath() == null || 
                pkg.applicationInfo.getResourcePath() == null) { 
            // Bail out. The resource and code paths haven't been set. 
            throw new PackageManagerException(INSTALL_FAILED_INVALID_APK, 
                    "Code and resource paths haven't been set correctly"); 
        } 
 
        if ((parseFlags&PackageParser.PARSE_IS_SYSTEM) != 0) { 
            pkg.applicationInfo.flags |= ApplicationInfo.FLAG_SYSTEM; 
        } else { 
            // Only allow system apps to be flagged as core apps. 
            pkg.coreApp = false; 
        } 
 
        if ((parseFlags&PackageParser.PARSE_IS_PRIVILEGED) != 0) { 
            pkg.applicationInfo.privateFlags |= ApplicationInfo.PRIVATE_FLAG_PRIVILEGED; 
        } 
 
        if (mCustomResolverComponentName != null && 
                mCustomResolverComponentName.getPackageName().equals(pkg.packageName)) { 
            setUpCustomResolverActivity(pkg); 
        } 
 
        if (pkg.packageName.equals("android")) { 
            synchronized (mPackages) { 
                if (mAndroidApplication != null) { 
                   //...   
                } 
 
                //保存该package信息 
                mPlatformPackage = pkg; 
                pkg.mVersionCode = mSdkVersion; 
                //保存该package的ApplicationInfo 
                mAndroidApplication = pkg.applicationInfo; 
 
                if (!mResolverReplaced) { 
                    //mResolveActivity为ChooserActivity信息的ActivityInfo 
                    mResolveActivity.applicationInfo = mAndroidApplication; 
                    mResolveActivity.name = ResolverActivity.class.getName(); 
                    mResolveActivity.packageName = mAndroidApplication.packageName; 
                    mResolveActivity.processName = "system:ui"; 
                    mResolveActivity.launchMode = ActivityInfo.LAUNCH_MULTIPLE; 
                    mResolveActivity.documentLaunchMode = ActivityInfo.DOCUMENT_LAUNCH_NEVER; 
                    mResolveActivity.flags = ActivityInfo.FLAG_EXCLUDE_FROM_RECENTS; 
                    mResolveActivity.theme = R.style.Theme_Holo_Dialog_Alert; 
                    mResolveActivity.exported = true; 
                    mResolveActivity.enabled = true; 
                    //mResolveInfo用于存储系统解析Intent后得到的结果信息,在从PKM查询满足某个Intent的 
                    //Activity时,返回的就是ResolveInfo,再根据ResolveInfo的activityInfo的信息得到                         //Activity 
                    mResolveInfo.activityInfo = mResolveActivity; 
                    mResolveInfo.priority = 0; 
                    mResolveInfo.preferredOrder = 0; 
                    mResolveInfo.match = 0; 
                    mResolveComponentName = new ComponentName( 
                            mAndroidApplication.packageName, mResolveActivity.name); 
                } 
            } 
        } 
 } 

“android“该Package与系统有非常重要的作用,这里保存特殊处理保存该Package的信息,主要是为了提高运行过程中的效率,例如ChooserActivity使用的地方非常多。
接下里scanPackageDirtyLI方法会对系统其它的Package做处理,关键源码如下:

//mPackages用于保存系统内的所有Package,以packageName为key 
 if (mPackages.containsKey(pkg.packageName) 
                || mSharedLibraries.containsKey(pkg.packageName)) { 
           //... 
                   } 
 
        if ((scanFlags & SCAN_REQUIRE_KNOWN) != 0) { 
            if (mExpectingBetter.containsKey(pkg.packageName)) { 
                logCriticalInfo(Log.WARN, 
                        "Relax SCAN_REQUIRE_KNOWN requirement for package " + pkg.packageName); 
            } else { 
                PackageSetting known = mSettings.peekPackageLPr(pkg.packageName); 
                if (known != null) { 
                    if (DEBUG_PACKAGE_SCANNING) { 
                        Log.d(TAG, "Examining " + pkg.codePath 
                                + " and requiring known paths " + known.codePathString 
                                + " & " + known.resourcePathString); 
                    } 
                    if (!pkg.applicationInfo.getCodePath().equals(known.codePathString) 
                            || !pkg.applicationInfo.getResourcePath().equals(known.resourcePathString)) { 
                        throw new PackageManagerException(INSTALL_FAILED_PACKAGE_CHANGED, 
                                "Application package " + pkg.packageName 
                                + " found at " + pkg.applicationInfo.getCodePath() 
                                + " but expected at " + known.codePathString + "; ignoring."); 
                    } 
                } 
            } 
        } 
 
        // Initialize package source and resource directories 
        File destCodeFile = new File(pkg.applicationInfo.getCodePath()); 
        File destResourceFile = new File(pkg.applicationInfo.getResourcePath()); 
 
        SharedUserSetting suid = null; 
        PackageSetting pkgSetting = null; 
 
        if (!isSystemApp(pkg)) { 
            // Only system apps can use these features. 
            pkg.mOriginalPackages = null; 
            pkg.mRealPackage = null; 
            pkg.mAdoptPermissions = null; 
        } 
        //... 
        final String pkgName = pkg.packageName; 
 
        final long scanFileTime = scanFile.lastModified(); 
        final boolean forceDex = (scanFlags & SCAN_FORCE_DEX) != 0; 
        //确定运行该package的进程名,一般用package作为进程名 
        pkg.applicationInfo.processName = fixProcessName( 
                pkg.applicationInfo.packageName, 
                pkg.applicationInfo.processName, 
                pkg.applicationInfo.uid); 
 
        File dataPath; 
        if (mPlatformPackage == pkg) { 
            // The system package is special. 
            dataPath = new File(Environment.getDataDirectory(), "system"); 
 
            pkg.applicationInfo.dataDir = dataPath.getPath(); 
 
        } else { 
            // This is a normal package, need to make its data directory. 
            //该函数返回data/data/packageName 
            dataPath = Environment.getDataUserPackageDirectory(pkg.volumeUuid, 
                    UserHandle.USER_OWNER, pkg.packageName); 
 
            boolean uidError = false; 
            if (dataPath.exists()) { 
                //.. 
            } else { 
                if (DEBUG_PACKAGE_SCANNING) { 
                    if ((parseFlags & PackageParser.PARSE_CHATTY) != 0) 
                        Log.v(TAG, "Want this data dir: " + dataPath); 
                } 
                //该方法调用installer发送install命令,其实就是在/data/data/目录下建立packageName目录 
                //然后为系统所有的user安装此apk 
                int ret = createDataDirsLI(pkg.volumeUuid, pkgName, pkg.applicationInfo.uid, 
                        pkg.applicationInfo.seinfo); 
                //安装错误 
                if (ret < 0) { 
                    // Error from installer 
                    throw new PackageManagerException(INSTALL_FAILED_INSUFFICIENT_STORAGE, 
                            "Unable to create data dirs [errorCode=" + ret + "]"); 
                } 
 
            } 
 
            pkgSetting.uidError = uidError; 
        } 
 
        final String path = scanFile.getPath(); 
        final String cpuAbiOverride = deriveAbiOverride(pkg.cpuAbiOverride, pkgSetting); 
        //在/data/data/pageName/lib下建立和CPU类型对应的目录,例如ARM平台的事arm/,MIP平台的事mips/ 
        if ((scanFlags & SCAN_NEW_INSTALL) == 0) { 
            derivePackageAbi(pkg, scanFile, cpuAbiOverride, true /* extract libs */); 
 
            //系统package的native库统一放在/system/lib下, 
            //所以系统不会提取系统package目录apk包中的native库 
            if (isSystemApp(pkg) && !pkg.isUpdatedSystemApp() && 
                    pkg.applicationInfo.primaryCpuAbi == null) { 
                setBundledAppAbisAndRoots(pkg, pkgSetting); 
                setNativeLibraryPaths(pkg); 
            } 
 
        } else { 
            if ((scanFlags & SCAN_MOVE) != 0) { 
            // 
            setNativeLibraryPaths(pkg); 
        } 
        //... 
        if ((scanFlags & SCAN_NO_DEX) == 0) { 
            //对该APK做dex优化 
            int result = mPackageDexOptimizer.performDexOpt(pkg, null /* instruction sets */, 
                    forceDex, (scanFlags & SCAN_DEFER_DEX) != 0, false /* inclDependencies */); 
      //如果该apk已经存在,要先杀掉该APK的进程 
         if ((scanFlags & SCAN_REPLACING) != 0) { 
            killApplication(pkg.applicationInfo.packageName, 
                        pkg.applicationInfo.uid, "replace pkg"); 
        } 
        //在此之前,四大组件信息都是Package对象的私有的,在这里把它们注册到PKM内部的财产管理对象中。 
        //这样,PKMS就可对外提供统一的组件信息。 
        synchronized (mPackages) { 
                ... 
            //注册该Package中的provider到PKM的mProviders上 
            int N = pkg.providers.size(); 
            StringBuilder r = null; 
            int i; 
            for (i=0; i<N; i++) { 
                PackageParser.Provider p = pkg.providers.get(i); 
                p.info.processName = fixProcessName(pkg.applicationInfo.processName, 
                        p.info.processName, pkg.applicationInfo.uid); 
                mProviders.addProvider(p); 
                p.syncable = p.info.isSyncable; 
                if (p.info.authority != null) { 
                   //...            
                    } 
            //注册该Package中的service到PKM的mServices上 
            N = pkg.services.size(); 
            r = null; 
            for (i=0; i<N; i++) { 
                PackageParser.Service s = pkg.services.get(i); 
                s.info.processName = fixProcessName(pkg.applicationInfo.processName, 
                        s.info.processName, pkg.applicationInfo.uid); 
                mServices.addService(s); 
                if ((parseFlags&PackageParser.PARSE_CHATTY) != 0) { 
                    if (r == null) { 
                        r = new StringBuilder(256); 
                    } else { 
                        r.append(' '); 
                    } 
                    r.append(s.info.name); 
                } 
            } 
            if (r != null) { 
                if (DEBUG_PACKAGE_SCANNING) Log.d(TAG, "  Services: " + r); 
            } 
            //注册该Package中的receiver到PKM的mReceivers上 
            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); 
                } 
            } 
            if (r != null) { 
                if (DEBUG_PACKAGE_SCANNING) Log.d(TAG, "  Receivers: " + r); 
            } 
            //注册该Package中的activity到PKM的mActivities上 
            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); 
                } 
            } 
            if (r != null) { 
                if (DEBUG_PACKAGE_SCANNING) Log.d(TAG, "  Activities: " + r); 
            } 
            //... 
          return pkg; 
    } 
 

5.3扫描非系统apk

在PackageManagerService构造函数扫描完系统apk后,接下来就是扫描非系统apk,这些apk在/data/app或者/data/app-private中。如下图:
Screenshot_2016_10_11_19_41_42
下面是关键源码,scanDirLI已经在前面分析过了。跟系统apk的调用过程差不多。

        if (!mOnlyCore) { 
                EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_DATA_SCAN_START, 
                        SystemClock.uptimeMillis()); 
                scanDirLI(mAppInstallDir, 0, scanFlags | SCAN_REQUIRE_KNOWN, 0); 
 
                scanDirLI(mDrmAppPrivateInstallDir, PackageParser.PARSE_FORWARD_LOCK, 
                        scanFlags | SCAN_REQUIRE_KNOWN, 0); 
        } 
 

5.4扫描结果保存到文件中

在PackageManagerService构造函数收尾阶段,PMS将前面收集的信息再整理一次,将已安装的apk信息写到package.xml、pacakage.list和package-stopped.xml中

            //整理更新Permisssion的信息 
            updatePermissionsLPw(null, null, updateFlags); 
            //... 
 
            //将信息写到package.xml,pacakage.list和package-stopped.xml中 
            mSettings.writeLPr(); 
 
            EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_READY, 
                    SystemClock.uptimeMillis()); 
 
            mRequiredVerifierPackage = getRequiredVerifierLPr(); 
            mRequiredInstallerPackage = getRequiredInstallerLPr(); 
 
        } // synchronized (mPackages) 
        } // synchronized (mInstallLock) 
 
        //gc 
        Runtime.getRuntime().gc(); 
  • packages.xml:系统对程序安装,卸载和更新等操作时会更新该文件,PMS扫描完目标文件夹后创建该文件,保存了Package相关的信息。
  • packages.list:保存着系统中所有的非系统自带的APK信息,程序安装,卸载和更新会更新该文件。
  • packages-stoped.xml:保存系统中被用户强制停止的Package的信息。

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。

原创文章,作者:奋斗,如若转载,请注明出处:https://blog.ytso.com/tech/app/5882.html

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