PMS初始化做了什么

1.前言

在SystemServer初始化过程当中，会调用PackageManagerService.main方法进行pms的初始化，那么我们就看看pms的初始化过程经历了什么。

public static PackageManagerService main(Context context, Installer installer,
        boolean factoryTest, boolean onlyCore) {
    PackageManagerService m = new PackageManagerService(context, installer,
            factoryTest, onlyCore);
    ServiceManager.addService("package", m);
    return m;
}

2.从pms构造函数说起

pms的构造函数相当长，根据gityuan大神的提示，按照log的打印进行分布查看却是清晰了很多。

2.1 BOOT_PROGRESS_PMS_START

mContext = context;
mFactoryTest = factoryTest;
mOnlyCore = onlyCore;
mLazyDexOpt = "eng".equals(SystemProperties.get("ro.build.type"));
mMetrics = new DisplayMetrics();
mSettings = new Settings(mPackages);
mSettings.addSharedUserLPw("android.uid.system", Process.SYSTEM_UID,
        ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);
mSettings.addSharedUserLPw("android.uid.phone", RADIO_UID,
        ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);
mSettings.addSharedUserLPw("android.uid.log", LOG_UID,
        ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);
mSettings.addSharedUserLPw("android.uid.nfc", NFC_UID,
        ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);
mSettings.addSharedUserLPw("android.uid.bluetooth", BLUETOOTH_UID,
        ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);
mSettings.addSharedUserLPw("android.uid.shell", SHELL_UID,
        ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);

// TODO: add a property to control this?
long dexOptLRUThresholdInMinutes;
if (mLazyDexOpt) {
    dexOptLRUThresholdInMinutes = 30; // only last 30 minutes of apps for eng builds.
} else {
    dexOptLRUThresholdInMinutes = 7 * 24 * 60; // apps used in the 7 days for users.
}
mDexOptLRUThresholdInMills = dexOptLRUThresholdInMinutes * 60 * 1000;

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;
mPackageDexOptimizer = new PackageDexOptimizer(this);
mMoveCallbacks = new MoveCallbacks(FgThread.get().getLooper());

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

getDefaultDisplayMetrics(context, mMetrics);

SystemConfig systemConfig = SystemConfig.getInstance();
mGlobalGids = systemConfig.getGlobalGids();
mSystemPermissions = systemConfig.getSystemPermissions();
mAvailableFeatures = systemConfig.getAvailableFeatures();

synchronized (mInstallLock) {
// writer
synchronized (mPackages) {
    mHandlerThread = new ServiceThread(TAG,
            Process.THREAD_PRIORITY_BACKGROUND, true /*allowIo*/);
    mHandlerThread.start();
    mHandler = new PackageHandler(mHandlerThread.getLooper());
    Watchdog.getInstance().addThread(mHandler, WATCHDOG_TIMEOUT);

    File dataDir = Environment.getDataDirectory();
    mAppDataDir = new File(dataDir, "data");
    mAppInstallDir = new File(dataDir, "app");
    mAppLib32InstallDir = new File(dataDir, "app-lib");
    mAsecInternalPath = new File(dataDir, "app-asec").getPath();
    mUserAppDataDir = new File(dataDir, "user");
    mDrmAppPrivateInstallDir = new File(dataDir, "app-private");

    sUserManager = new UserManagerService(context, this,
            mInstallLock, mPackages);

    // Propagate permission configuration in to package manager.
    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);
        }
    }

    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();

• 构造Settings对象，添加shareUserId
• 构造SystemConfig，获取mSystemPermissions灯属性
• 创建data/data,data/app/,data/app-lib,data-asec,data/user,data/app-privat等file对象
• 从systemConfig中获取到所有的共享库，添加到mSharedLibraries中，

2.2 PMS_SYSTEM_SCAN_START

final int scanFlags = SCAN_NO_PATHS | SCAN_DEFER_DEX | SCAN_BOOTING | SCAN_INITIAL;

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

if (bootClassPath != null) {
    String[] bootClassPathElements = splitString(bootClassPath, ':');
    for (String element : bootClassPathElements) {
        alreadyDexOpted.add(element);
    }
} else {
    Slog.w(TAG, "No BOOTCLASSPATH found!");
}

if (systemServerClassPath != null) {
    String[] systemServerClassPathElements = splitString(systemServerClassPath, ':');
    for (String element : systemServerClassPathElements) {
        alreadyDexOpted.add(element);
    }
} else {
    Slog.w(TAG, "No SYSTEMSERVERCLASSPATH found!");
}

final List<String> allInstructionSets = InstructionSets.getAllInstructionSets();
final String[] dexCodeInstructionSets =
        getDexCodeInstructionSets(
                allInstructionSets.toArray(new String[allInstructionSets.size()]));

/**
 * Ensure all external libraries have had dexopt run on them.
 */
if (mSharedLibraries.size() > 0) {
    // NOTE: For now, we're compiling these system "shared libraries"
    // (and framework jars) into all available architectures. It's possible
    // to compile them only when we come across an app that uses them (there's
    // already logic for that in scanPackageLI) but that adds some complexity.
    for (String dexCodeInstructionSet : dexCodeInstructionSets) {
        for (SharedLibraryEntry libEntry : mSharedLibraries.values()) {
            final String lib = libEntry.path;
            if (lib == null) {
                continue;
            }

            try {
                int dexoptNeeded = DexFile.getDexOptNeeded(lib, null, dexCodeInstructionSet, false);
                if (dexoptNeeded != DexFile.NO_DEXOPT_NEEDED) {
                    alreadyDexOpted.add(lib);
                    mInstaller.dexopt(lib, Process.SYSTEM_UID, true, dexCodeInstructionSet, dexoptNeeded);
                }
            } catch (FileNotFoundException e) {
                Slog.w(TAG, "Library not found: " + lib);
            } catch (IOException e) {
                Slog.w(TAG, "Cannot dexopt " + lib + "; is it an APK or JAR? "
                        + e.getMessage());
            }
        }
    }
}

File frameworkDir = new File(Environment.getRootDirectory(), "framework");

// Gross hack for now: we know this file doesn't contain any
// code, so don't dexopt it to avoid the resulting log spew.
alreadyDexOpted.add(frameworkDir.getPath() + "/framework-res.apk");

// Gross hack for now: we know this file is only part of
// the boot class path for art, so don't dexopt it to
// avoid the resulting log spew.
alreadyDexOpted.add(frameworkDir.getPath() + "/core-libart.jar");

/**
 * There are a number of commands implemented in Java, which
 * we currently need to do the dexopt on so that they can be
 * run from a non-root shell.
 */
String[] frameworkFiles = frameworkDir.list();
if (frameworkFiles != null) {
    // TODO: We could compile these only for the most preferred ABI. We should
    // first double check that the dex files for these commands are not referenced
    // by other system apps.
    for (String dexCodeInstructionSet : dexCodeInstructionSets) {
        for (int i=0; i<frameworkFiles.length; i++) {
            File libPath = new File(frameworkDir, frameworkFiles[i]);
            String path = libPath.getPath();
            // Skip the file if we already did it.
            if (alreadyDexOpted.contains(path)) {
                continue;
            }
            // Skip the file if it is not a type we want to dexopt.
            if (!path.endsWith(".apk") && !path.endsWith(".jar")) {
                continue;
            }
            try {
                int dexoptNeeded = DexFile.getDexOptNeeded(path, null, dexCodeInstructionSet, false);
                if (dexoptNeeded != DexFile.NO_DEXOPT_NEEDED) {
                    mInstaller.dexopt(path, Process.SYSTEM_UID, true, dexCodeInstructionSet, dexoptNeeded);
                }
            } catch (FileNotFoundException e) {
                Slog.w(TAG, "Jar not found: " + path);
            } catch (IOException e) {
                Slog.w(TAG, "Exception reading jar: " + path, e);
            }
        }
    }
}

final VersionInfo ver = mSettings.getInternalVersion();
mIsUpgrade = !Build.FINGERPRINT.equals(ver.fingerprint);
// when upgrading from pre-M, promote system app permissions from install to runtime
mPromoteSystemApps =
        mIsUpgrade && ver.sdkVersion <= Build.VERSION_CODES.LOLLIPOP_MR1;

// save off the names of pre-existing system packages prior to scanning; we don't
// want to automatically grant runtime permissions for new system apps
if (mPromoteSystemApps) {
    Iterator<PackageSetting> pkgSettingIter = mSettings.mPackages.values().iterator();
    while (pkgSettingIter.hasNext()) {
        PackageSetting ps = pkgSettingIter.next();
        if (isSystemApp(ps)) {
            mExistingSystemPackages.add(ps.name);
        }
    }
}

// Collect vendor overlay packages.
// (Do this before scanning any apps.)
// For security and version matching reason, only consider
// overlay packages if they reside in VENDOR_OVERLAY_DIR.
File vendorOverlayDir = new File(VENDOR_OVERLAY_DIR);
scanDirLI(vendorOverlayDir, PackageParser.PARSE_IS_SYSTEM
        | PackageParser.PARSE_IS_SYSTEM_DIR, scanFlags | SCAN_TRUSTED_OVERLAY, 0);

// Find base frameworks (resource packages without code).
scanDirLI(frameworkDir, PackageParser.PARSE_IS_SYSTEM
        | PackageParser.PARSE_IS_SYSTEM_DIR
        | PackageParser.PARSE_IS_PRIVILEGED,
        scanFlags | SCAN_NO_DEX, 0);

// Collected privileged system packages.
final File privilegedAppDir = new File(Environment.getRootDirectory(), "priv-app");
scanDirLI(privilegedAppDir, PackageParser.PARSE_IS_SYSTEM
        | PackageParser.PARSE_IS_SYSTEM_DIR
        | PackageParser.PARSE_IS_PRIVILEGED, scanFlags, 0);

// Collect ordinary system packages.
final File systemAppDir = new File(Environment.getRootDirectory(), "app");
scanDirLI(systemAppDir, PackageParser.PARSE_IS_SYSTEM
        | PackageParser.PARSE_IS_SYSTEM_DIR, scanFlags, 0);

// Collect all vendor packages.
File vendorAppDir = new File("/vendor/app");
try {
    vendorAppDir = vendorAppDir.getCanonicalFile();
} catch (IOException e) {
    // failed to look up canonical path, continue with original one
}
scanDirLI(vendorAppDir, PackageParser.PARSE_IS_SYSTEM
        | PackageParser.PARSE_IS_SYSTEM_DIR, scanFlags, 0);

// Collect all OEM packages.
final File oemAppDir = new File(Environment.getOemDirectory(), "app");
scanDirLI(oemAppDir, PackageParser.PARSE_IS_SYSTEM
        | PackageParser.PARSE_IS_SYSTEM_DIR, scanFlags, 0);

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

// Prune any system packages that no longer exist.
final List<String> possiblyDeletedUpdatedSystemApps = new ArrayList<String>();
if (!mOnlyCore) {
    Iterator<PackageSetting> 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) {
            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.
             */
            if (mSettings.isDisabledSystemPackageLPr(ps.name)) {
                logCriticalInfo(Log.WARN, "Expecting better updated system app for "
                        + ps.name + "; removing system app.  Last known codePath="
                        + ps.codePathString + ", installStatus=" + ps.installStatus
                        + ", versionCode=" + ps.versionCode + "; scanned versionCode="
                        + scannedPkg.mVersionCode);
                removePackageLI(ps, true);
                mExpectingBetter.put(ps.name, ps.codePath);
            }

            continue;
        }

        if (!mSettings.isDisabledSystemPackageLPr(ps.name)) {
            psit.remove();
            logCriticalInfo(Log.WARN, "System package " + ps.name
                    + " no longer exists; wiping its data");
            removeDataDirsLI(null, 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
ArrayList<PackageSetting> deletePkgsList = mSettings.getListOfIncompleteInstallPackagesLPr();
//clean up list
for(int i = 0; i < deletePkgsList.size(); i++) {
    //clean up here
    cleanupInstallFailedPackage(deletePkgsList.get(i));
}
//delete tmp files
deleteTempPackageFiles();

// Remove any shared userIDs that have no associated packages
mSettings.pruneSharedUsersLPw();

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);

    /**
     * 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(null, 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;
        }
        logCriticalInfo(Log.WARN, msg);
    }

    /**
     * Make sure all system apps that we expected to appear on
     * the userdata partition actually showed up. If they never
     * appeared, crawl back and revive the system version.
     */
    for (int i = 0; i < mExpectingBetter.size(); i++) {
        final String packageName = mExpectingBetter.keyAt(i);
        if (!mPackages.containsKey(packageName)) {
            final File scanFile = mExpectingBetter.valueAt(i);

            logCriticalInfo(Log.WARN, "Expected better " + packageName
                    + " but never showed up; reverting to system");

            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 {
                Slog.e(TAG, "Ignoring unexpected fallback path " + scanFile);
                continue;
            }

            mSettings.enableSystemPackageLPw(packageName);

            try {
                scanPackageLI(scanFile, reparseFlags, scanFlags, 0, null);
            } catch (PackageManagerException e) {
                Slog.e(TAG, "Failed to parse original system package: "
                        + e.getMessage());
            }
        }
    }
}
mExpectingBetter.clear();

// Now that we know all of the shared libraries, update all clients to have
// the correct library paths.
updateAllSharedLibrariesLPw();

for (SharedUserSetting setting : mSettings.getAllSharedUsersLPw()) {
    // NOTE: We ignore potential failures here during a system scan (like
    // the rest of the commands above) because there's precious little we
    // can do about it. A settings error is reported, though.
    adjustCpuAbisForSharedUserLPw(setting.packages, null /* scanned package */,
            false /* force dexopt */, false /* defer dexopt */);
}

// Now that we know all the packages we are keeping,
// read and update their last usage times.
mPackageUsage.readLP();

扫描阶段，这个阶段主要是对 包进行解析，得到组件信息等内容，并且根据需要进行dex优化。

• 首先将BOOTCLASSPATH，SYSTEMSERVERCLASSPATH这两个环境变量下的路径加入到不需要dex优化列表，在我的小米note手机上，BOOTCLASSPATH内容为下,

  /system/bin/sh: /system/framework/core-libart.jar:/system/framework/conscrypt.jar:/system/framework/okhttp.jar:/system/framework/core-junit.jar:/system/framework/bouncycastle.jar:/system/framework/ext.jar:/system/framework/framework.jar:/system/framework/telephony-common.jar:/system/framework/voip-common.jar:/system/framework/ims-common.jar:/system/framework/apache-xml.jar:/system/framework/org.apache.http.legacy.boot.jar:/system/framework/tcmiface.jar:/system/framework/qcmediaplayer.jar:/system/framework/WfdCommon.jar:/system/framework/qcom.fmradio.jar:/system/framework/oem-services.jar:/system/framework/com.qti.dpmframework.jar:/system/framework/dpmapi.jar:/system/framework/com.qti.location.sdk.jar:/system/app/miui/miui.apk:/system/app/miuisystem/miuisystem.apk: not found

SYSTEMSERVERCLASSPATH内容为下

/system/bin/sh: /system/framework/services.jar:/system/framework/wifi-service.jar:/system/framework/ethernet-service.jar: not found

• 获取构建时指定的cpu指令
• 根据cpu指令得到SharedLibrarie，判断是否需要dex优化，进行dex优化，并加入到alreadyDexOpted列表中
• 将framework/framework-res.apk，framework/core-libart.jar，等加入到已优化列表
• 将framework目录下，其他的apk或者jar，进行dex优化并加入已优化列表
• 收集解析/vendor/overlay，/system/framework，/system/priv-app，/system/app，/vendor/priv-app，/vendor/app，/oem/app目录下app的信息
• 删除系统不存在的包removePackageLI
• 清理安装失败的包 cleanupInstallFailedPackage
• 删除临时文件
• 移除不想干的包中的shared userIDs

2.3 BOOT_PROGRESS_PMS_DATA_SCAN_START

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);

      /**
       * 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(null, 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;
          }
          logCriticalInfo(Log.WARN, msg);
      }

      /**
       * Make sure all system apps that we expected to appear on
       * the userdata partition actually showed up. If they never
       * appeared, crawl back and revive the system version.
       */
      for (int i = 0; i < mExpectingBetter.size(); i++) {
          final String packageName = mExpectingBetter.keyAt(i);
          if (!mPackages.containsKey(packageName)) {
              final File scanFile = mExpectingBetter.valueAt(i);

              logCriticalInfo(Log.WARN, "Expected better " + packageName
                      + " but never showed up; reverting to system");

              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 {
                  Slog.e(TAG, "Ignoring unexpected fallback path " + scanFile);
                  continue;
              }

              mSettings.enableSystemPackageLPw(packageName);

              try {
                  scanPackageLI(scanFile, reparseFlags, scanFlags, 0, null);
              } catch (PackageManagerException e) {
                  Slog.e(TAG, "Failed to parse original system package: "
                          + e.getMessage());
              }
          }
      }
  }
  mExpectingBetter.clear();

  // Now that we know all of the shared libraries, update all clients to have
  // the correct library paths.
  updateAllSharedLibrariesLPw();

  for (SharedUserSetting setting : mSettings.getAllSharedUsersLPw()) {
      // NOTE: We ignore potential failures here during a system scan (like
      // the rest of the commands above) because there's precious little we
      // can do about it. A settings error is reported, though.
      adjustCpuAbisForSharedUserLPw(setting.packages, null /* scanned package */,
              false /* force dexopt */, false /* defer dexopt */);
  }

  // Now that we know all the packages we are keeping,
  // read and update their last usage times.
  mPackageUsage.readLP();

• mOnlyCore为false的情况下，会扫描/data/app，/data/app-private目录，

2.4 PMS_SCAN_END

int updateFlags = UPDATE_PERMISSIONS_ALL;
  if (ver.sdkVersion != mSdkVersion) {
      Slog.i(TAG, "Platform changed from " + ver.sdkVersion + " to "
              + mSdkVersion + "; regranting permissions for internal storage");
      updateFlags |= UPDATE_PERMISSIONS_REPLACE_PKG | UPDATE_PERMISSIONS_REPLACE_ALL;
  }
  updatePermissionsLPw(null, null, updateFlags);
  ver.sdkVersion = mSdkVersion;

  // If this is the first boot or an update from pre-M, and it is a normal
  // boot, then we need to initialize the default preferred apps across
  // all defined users.
  if (!onlyCore && (mPromoteSystemApps || !mRestoredSettings)) {
      for (UserInfo user : sUserManager.getUsers(true)) {
          mSettings.applyDefaultPreferredAppsLPw(this, user.id);
          applyFactoryDefaultBrowserLPw(user.id);
          primeDomainVerificationsLPw(user.id);
      }
  }

  // If this is first boot after an OTA, and a normal boot, then
  // we need to clear code cache directories.
  if (mIsUpgrade && !onlyCore) {
      Slog.i(TAG, "Build fingerprint changed; clearing code caches");
      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();

  // clear only after permissions and other defaults have been updated
  mExistingSystemPackages.clear();
  mPromoteSystemApps = false;

  // All the changes are done during package scanning.
  ver.databaseVersion = Settings.CURRENT_DATABASE_VERSION;

  // can downgrade to reader
  mSettings.writeLPr();

• 当sdk版本不一致时，需要更新权限
• 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
• 当权限和其他默认项都完成更新，则清理相关信息
• 信息写回packages.xml文件

这部分不是很懂。

2.5 BOOT_PROGRESS_PMS_READY

  mRequiredVerifierPackage = getRequiredVerifierLPr();
    mRequiredInstallerPackage = getRequiredInstallerLPr();

    mInstallerService = new PackageInstallerService(context, this);

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

} // synchronized (mPackages)
} // synchronized (mInstallLock)

// 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();

// Expose private service for system components to use.
LocalServices.addService(PackageManagerInternal.class, new PackageManagerInternalImpl());

• 初始化PackageInstallerService
• gc，回收下内存

3.Settings

这个类负责读取data/system下的几个xml文件。收集其中的一些信息。

• packages.xml 记录所有安装app的信息
• packages-backup.xml 备份文件
• packages-stopped.xml 记录系统被强制停止的文件
• packages-stopped-backup.xml 备份文件
• packages.list 记录应用的数据信息

4.scanDirLI

这个方法会调用scanPackageLI对apk进行扫描解析，在这里，会构造PackageParser.Package对象，并进行解析。

final PackageParser.Package pkg;
 try {
     pkg = pp.parsePackage(scanFile, parseFlags);
 } catch (PackageParserException e) {
     throw PackageManagerException.from(e);
 }

重点看解析部分的代码。

public Package parsePackage(File packageFile, int flags) throws PackageParserException {
     if (packageFile.isDirectory()) {
         return parseClusterPackage(packageFile, flags);
     } else {
         return parseMonolithicPackage(packageFile, flags);
     }
 }

三名两个的区别就是 单个apk文件和apks。不管是单个 还是文件夹，都会调用parseBaseApk去解析，

res = new Resources(assets, mMetrics, null);
assets.setConfiguration(0, 0, null, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        Build.VERSION.RESOURCES_SDK_INT);
parser = assets.openXmlResourceParser(cookie, ANDROID_MANIFEST_FILENAME);

final String[] outError = new String[1];
final Package pkg = parseBaseApk(res, parser, flags, outError);

在这里，会拿到配置文件，调用4个参数的这个方法去解析。这个方法里面都是类似这样的代码。

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;
                if (!parseBaseApplication(pkg, res, parser, attrs, flags, outError)) {
                    return null;
                }
            }

用xml解析 去解析配置文件中的各个标签，并且在parseBaseApplication中，会解析初我们的四大组件并存储起来。

if (tagName.equals("activity")) {
                Activity a = parseActivity(owner, res, parser, attrs, flags, outError, false,
                        owner.baseHardwareAccelerated);
                if (a == null) {
                    mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED;
                    return false;
                }

                owner.activities.add(a);

            }

这里就不多说了。

4. dex优化

在Installer中，

public int dexopt(String apkPath, int uid, boolean isPublic, String pkgName,
        String instructionSet, int dexoptNeeded, boolean vmSafeMode,
        boolean debuggable, String outputPath) {
    StringBuilder builder = new StringBuilder("dexopt");
    builder.append(' ');
    builder.append(apkPath);
    builder.append(' ');
    builder.append(uid);
    builder.append(isPublic ? " 1" : " 0");
    builder.append(' ');
    builder.append(pkgName);
    builder.append(' ');
    builder.append(instructionSet);
    builder.append(' ');
    builder.append(dexoptNeeded);
    builder.append(vmSafeMode ? " 1" : " 0");
    builder.append(debuggable ? " 1" : " 0");
    builder.append(' ');
    builder.append(outputPath != null ? outputPath : "!");
    return execute(builder.toString());
}

进行参数封装，

public int execute(String cmd) {
    String res = transact(cmd);
    try {
        return Integer.parseInt(res);
    } catch (NumberFormatException ex) {
        return -1;
    }
}

在transact中，通过connect，socket连接installd守护进程，并通过writeCommand写入dex优化命令，用installd来完成dex优化。

参考资料

• gityuan
• Android 5.0 源代码

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