PMS全称PackageManagerService，PMS是Android系统核心服务之一，处理包管理相关的工作，常见的比如安装、卸载应用等。PMS是系统服务，那么应用层肯定有个PackageManager作为binder call client端来供使用，但是这里要注意，PackageManager是个抽象类，一般使用的是它的实现类：ApplicationPackageManager。因此PackageManager功能的具体实现还是ApplicationPackageManager这个实现类。PMS主要功能：
- 安装、卸载应用
- 查询permission相关信息
- 查询Application相关信息(application、activity、receiver、service、provider及相应属性等)
- 查询已安装应用
- 增加、删除permission
- 清除用户数据、缓存、代码等
在SystemServer启动时会调用startBootstrapServices()来启动引导服务，在startBootstrapServices中会启动PackageManagerService:
...
mPackageManagerService = PackageManagerService.main(mSystemContext, installer, mFactoryTestMode != FactoryTest.FACTORY_TEST_OFF, mOnlyCore);
这里PMS的构造方法：
public static PackageManagerService main(Context context, Installer installer,
boolean factoryTest, boolean onlyCore) {
// Self-check for initial settings.
PackageManagerServiceCompilerMapping.checkProperties();
//初始化PMS
PackageManagerService m = new PackageManagerService(context, installer,
factoryTest, onlyCore);
m.enableSystemUserPackages();
//将package服务注册到ServiceManager大管家
ServiceManager.addService("package", m);
return m;
}PMS的构造方法一共有700多行，在代码中，将PMS的构造流程分为了5个阶段，每个阶段会使用EventLog.writeEvent打印系统日志。
- BOOT_PROGRESS_PMS_START（开始阶段）
- BOOT_PROGRESS_PMS_SYSTEM_SCAN_START（扫描系统阶段）
- BOOT_PROGRESS_PMS_DATA_SCAN_START（扫描Data分区阶段）
- BOOT_PROGRESS_PMS_SCAN_END（扫描结束阶段）
- BOOT_PROGRESS_PMS_READY（准备阶段）
开始阶段(BOOT_PROGRESS_PMS_START)
public PackageManagerService(Context context, Installer installer,
boolean factoryTest, boolean onlyCore) {
//打印开始日志
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_START,
SystemClock.uptimeMillis());
if (mSdkVersion <= 0) {
Slog.w(TAG, "**** ro.build.version.sdk not set!");
}
mContext = context;
mPermissionReviewRequired = context.getResources().getBoolean(
R.bool.config_permissionReviewRequired);
mFactoryTest = factoryTest;
mOnlyCore = onlyCore;
//用于存储屏幕的相关信息
mMetrics = new DisplayMetrics();
//创建Settings对象 (1)
mSettings = new Settings(mPackages);
// 添加system, phone, log, nfc, bluetooth, shell这六种shareUserId到mSettings；
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);
......
mInstaller = installer;
//创建Dex优化工具类
mPackageDexOptimizer = new PackageDexOptimizer(installer, mInstallLock, context,
"*dexopt*");
mMoveCallbacks = new MoveCallbacks(FgThread.get().getLooper());
mOnPermissionChangeListeners = new OnPermissionChangeListeners(
FgThread.get().getLooper());
getDefaultDisplayMetrics(context, mMetrics);
//得到全局系统配置信息
SystemConfig systemConfig = SystemConfig.getInstance();
//获取全局的groupId
mGlobalGids = systemConfig.getGlobalGids();
//获取系统权限
mSystemPermissions = systemConfig.getSystemPermissions();
mAvailableFeatures = systemConfig.getAvailableFeatures();
mProtectedPackages = new ProtectedPackages(mContext);
//安装APK时需要的锁，保护所有对installd的访问。
synchronized (mInstallLock) {
//更新APK时需要的锁，保护内存中已经解析的包信息等内容
synchronized (mPackages) {
//创建后台线程ServiceThread
mHandlerThread = new ServiceThread(TAG,
Process.THREAD_PRIORITY_BACKGROUND, true /*allowIo*/);
mHandlerThread.start();
//创建PackageHandler绑定到ServiceThread的消息队列
mHandler = new PackageHandler(mHandlerThread.getLooper());
mProcessLoggingHandler = new ProcessLoggingHandler();
//将PackageHandler添加到Watchdog的检测集中
Watchdog.getInstance().addThread(mHandler, WATCHDOG_TIMEOUT);
mDefaultPermissionPolicy = new DefaultPermissionGrantPolicy(this);
//在Data分区创建一些目录
File dataDir = Environment.getDataDirectory();
mAppInstallDir = new File(dataDir, "app");
mAppLib32InstallDir = new File(dataDir, "app-lib");
mEphemeralInstallDir = new File(dataDir, "app-ephemeral");
mAsecInternalPath = new File(dataDir, "app-asec").getPath();
mDrmAppPrivateInstallDir = new File(dataDir, "app-private");
mRegionalizationAppInstallDir = new File(dataDir, "app-regional");
//创建多用户管理服务
sUserManager = new UserManagerService(context, this, mPackages);
mFoundPolicyFile = SELinuxMMAC.readInstallPolicy();
//解析packages.xml等文件的信息，保存到Settings的对应字段中。packages.xml中记录系统中所有安装的应用信息，包括基本信息、签名和权限。如果packages.xml有安装的应用信息，readLPw方法会返回true，mFirstBoot的值为false，说明PMS不是首次被启动。
mFirstBoot = !mSettings.readLPw(sUserManager.getUsers(false));mSettings 用于保存所有包的动态设置
Settings(Object lock) {
this(Environment.getDataDirectory(), lock);
}
Settings(File dataDir, Object lock) {
mLock = lock;
mRuntimePermissionsPersistence = new RuntimePermissionPersistence(mLock);
mSystemDir = new File(dataDir, "system");
mSystemDir.mkdirs(); //创建/data/system
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);
mStoppedPackagesFilename = new File(mSystemDir, "packages-stopped.xml");
mBackupStoppedPackagesFilename = new File(mSystemDir, "packages-stopped-backup.xml");
}mSystemDir是指目录/data/system,有5个子文件：
- 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
mInstaller
Installer继承自SystemService，和PMS、AMS一样是系统的服务(引导服务)，PMS很多的操作都是由Installer来完成的，比如APK的安装和卸载。在Installer内部，通过socket与installd通信，8.0以上改成了IInstalld和installd进行Binder通信，由位于nativie层的installd来完成具体的操作。
systemConfig
用于得到全局系统配置信息。比如系统的权限就可以通过SystemConfig来获取。
mPackageDexOptimizer
Dex优化的工具类。
mHandler（PackageHandler类型）
PackageHandler继承自Handler，PMS通过PackageHandler驱动APK的复制和安装工作。
PackageHandler处理的消息队列如果过于繁忙，有可能导致系统卡住， 因此将它添加到Watchdog的监测集中。
Watchdog主要有两个用途，一个是定时检测系统关键服务（AMS和WMS等）是否可能发生死锁，还有一个是定时检测线程的消息队列是否长时间处于工作状态（可能阻塞等待了很长时间）。如果出现上述问题，Watchdog会将日志保存起来，必要时还会杀掉自己所在的进程，也就是SystemServer进程。
sUserManager（UserManagerService类型）
多用户管理服务
2、扫描系统阶段(BOOT_PROGRESS_PMS_SYSTEM_SCAN_START)
//打印扫描系统阶段日志
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_SYSTEM_SCAN_START,
startTime);
// Set flag to monitor and not change apk file paths when
// scanning install directories.
final int scanFlags = SCAN_NO_PATHS | SCAN_DEFER_DEX | SCAN_BOOTING | SCAN_INITIAL;
final String bootClassPath = System.getenv("BOOTCLASSPATH");
final String systemServerClassPath = System.getenv("SYSTEMSERVERCLASSPATH");
if (bootClassPath == null) {
Slog.w(TAG, "No BOOTCLASSPATH found!");
}
if (systemServerClassPath == null) {
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 {
// Shared libraries do not have profiles so we perform a full
// AOT compilation (if needed).
int dexoptNeeded = DexFile.getDexOptNeeded(
lib, dexCodeInstructionSet,
getCompilerFilterForReason(REASON_SHARED_APK),
false /* newProfile */);
if (dexoptNeeded != DexFile.NO_DEXOPT_NEEDED) {
mInstaller.dexopt(lib, Process.SYSTEM_UID, dexCodeInstructionSet,
dexoptNeeded, DEXOPT_PUBLIC /*dexFlags*/,
getCompilerFilterForReason(REASON_SHARED_APK),
StorageManager.UUID_PRIVATE_INTERNAL,
SKIP_SHARED_LIBRARY_CHECK);
}
} catch (FileNotFoundException e) {
Slog.w(TAG, "Library not found: " + lib);
} catch (IOException | InstallerException e) {
Slog.w(TAG, "Cannot dexopt " + lib + "; is it an APK or JAR? "
+ e.getMessage());
}
}
}
}
//在/system中创建framework目录
File frameworkDir = new File(Environment.getRootDirectory(), "framework");
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;
// When upgrading from pre-N, we need to handle package extraction like first boot,
// as there is no profiling data available.
mIsPreNUpgrade = mIsUpgrade && ver.sdkVersion < Build.VERSION_CODES.N;
mIsPreNMR1Upgrade = mIsUpgrade && ver.sdkVersion < Build.VERSION_CODES.N_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 the right directory.
String overlayThemeDir = SystemProperties.get(VENDOR_OVERLAY_THEME_PROPERTY);
//扫描/vendor/overlay目录下的文件
if (!overlayThemeDir.isEmpty()) {
scanDirTracedLI(new File(VENDOR_OVERLAY_DIR, overlayThemeDir), mDefParseFlags
| PackageParser.PARSE_IS_SYSTEM
| PackageParser.PARSE_IS_SYSTEM_DIR
| PackageParser.PARSE_TRUSTED_OVERLAY, scanFlags | SCAN_TRUSTED_OVERLAY, 0);
}
scanDirTracedLI(new File(VENDOR_OVERLAY_DIR), mDefParseFlags
| PackageParser.PARSE_IS_SYSTEM
| PackageParser.PARSE_IS_SYSTEM_DIR
| PackageParser.PARSE_TRUSTED_OVERLAY, scanFlags | SCAN_TRUSTED_OVERLAY, 0);
// Find base frameworks (resource packages without code).
//收集包名：/system/framework
scanDirTracedLI(frameworkDir, mDefParseFlags
| PackageParser.PARSE_IS_SYSTEM
| PackageParser.PARSE_IS_SYSTEM_DIR
| PackageParser.PARSE_IS_PRIVILEGED,
scanFlags | SCAN_NO_DEX, 0);
// Collected privileged system packages.
//收集私有的系统包名：/system/priv-app
final File privilegedAppDir = new File(Environment.getRootDirectory(), "priv-app");
scanDirTracedLI(privilegedAppDir, mDefParseFlags
| PackageParser.PARSE_IS_SYSTEM
| PackageParser.PARSE_IS_SYSTEM_DIR
| PackageParser.PARSE_IS_PRIVILEGED, scanFlags, 0);
// Collect ordinary system packages.
//收集一般的系统包名：/system/app
final File systemAppDir = new File(Environment.getRootDirectory(), "app");
scanDirTracedLI(systemAppDir, mDefParseFlags
| PackageParser.PARSE_IS_SYSTEM
| PackageParser.PARSE_IS_SYSTEM_DIR, scanFlags, 0);
// Collect all vendor packages.
//收集所有的供应商包名：/vendor/app
File vendorAppDir = new File("/vendor/app");
try {
vendorAppDir = vendorAppDir.getCanonicalFile();
} catch (IOException e) {
// failed to look up canonical path, continue with original one
}
scanDirTracedLI(vendorAppDir, mDefParseFlags
| PackageParser.PARSE_IS_SYSTEM
| PackageParser.PARSE_IS_SYSTEM_DIR, scanFlags, 0);
// Collect all OEM packages.
//收集所有OEM包名：/oem/app
final File oemAppDir = new File(Environment.getOemDirectory(), "app");
scanDirTracedLI(oemAppDir, mDefParseFlags
| PackageParser.PARSE_IS_SYSTEM
| PackageParser.PARSE_IS_SYSTEM_DIR, scanFlags, 0);
// Collect all Regionalization packages form Carrier's res packages.
if (RegionalizationEnvironment.isSupported()) {
Log.d(TAG, "Load Regionalization vendor apks");
final List<File> RegionalizationDirs =
RegionalizationEnvironment.getAllPackageDirectories();
for (File f : RegionalizationDirs) {
File RegionalizationSystemDir = new File(f, "system");
// Collect packages in <Package>/system/priv-app
scanDirLI(new File(RegionalizationSystemDir, "priv-app"),
PackageParser.PARSE_IS_SYSTEM | PackageParser.PARSE_IS_SYSTEM_DIR
| PackageParser.PARSE_IS_PRIVILEGED, scanFlags, 0);
// Collect packages in <Package>/system/app
scanDirLI(new File(RegionalizationSystemDir, "app"),
PackageParser.PARSE_IS_SYSTEM | PackageParser.PARSE_IS_SYSTEM_DIR,
scanFlags, 0);
// Collect overlay in <Package>/system/vendor
scanDirLI(new File(RegionalizationSystemDir, "vendor/overlay"),
PackageParser.PARSE_IS_SYSTEM | PackageParser.PARSE_IS_SYSTEM_DIR,
scanFlags | SCAN_TRUSTED_OVERLAY, 0);
}
}
// Prune any system packages that no longer exist.
// 这个列表代表有可能有升级包的系统App
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)) { //1
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);
//将这个系统App的PackageSetting从PMS的mPackages中移除
removePackageLI(scannedPkg, true);
//将升级包的路径添加到mExpectingBetter列表中
mExpectingBetter.put(ps.name, ps.codePath);
}
continue;
}
if (!mSettings.isDisabledSystemPackageLPr(ps.name)) {
psit.remove();
logCriticalInfo(Log.WARN, "System package " + ps.name
+ " no longer exists; it's data will be wiped");
// Actual deletion of code and data will be handled by later
// reconciliation step
} else {
final PackageSetting disabledPs = mSettings.getDisabledSystemPkgLPr(ps.name);
//这个系统App升级包信息在mDisabledSysPackages中,但是没有发现这个升级包存在
if (disabledPs.codePath == null || !disabledPs.codePath.exists()) {//2
possiblyDeletedUpdatedSystemApps.add(ps.name);
}
}
}
}
//look for any incomplete package installations
//清理所有安装不完整的包
ArrayList<PackageSetting> deletePkgsList = mSettings.getListOfIncompleteInstallPackagesLPr();
for (int i = 0; i < deletePkgsList.size(); i++) {
// Actual deletion of code and data will be handled by later
// reconciliation step
final String packageName = deletePkgsList.get(i).name;
logCriticalInfo(Log.WARN, "Cleaning up incompletely installed app: " + packageName);
synchronized (mPackages) {
mSettings.removePackageLPw(packageName);
}
}
//delete tmp files
//删除临时文件
deleteTempPackageFiles();
// Remove any shared userIDs that have no associated packages
mSettings.pruneSharedUsersLPw();系统扫描阶段的主要工作有以下3点：
- 创建/system的子目录，比如/system/framework、/system/priv-app和/system/app等等
- 扫描系统文件，比如/vendor/overlay、/system/framework、/system/app等等目录下的文件。
- 对扫描到的系统文件做后续处理。
关于第3点，一次OTA升级对于一个系统App会有三种情况：
- 这个系统APP无更新。
- 这个系统APP有更新。
- 新的OTA版本中，这个系统APP已经被删除。
当系统App升级，PMS会将该系统App的升级包设置数据（PackageSetting）存储到Settings的mDisabledSysPackages列表中（具体见PMS的replaceSystemPackageLIF方法），mDisabledSysPackages的类型为ArrayMap<String, PackageSetting>。mDisabledSysPackages中的信息会被PMS保存到packages.xml中的<updated-package>标签下（具体见Settings的writeDisabledSysPackageLPr方法）。
注释1处说明这个系统App有升级包，那么就将该系统App的PackageSetting从mDisabledSysPackages列表中移除，并将系统App的升级包的路径添加到mExpectingBetter列表中，mExpectingBetter的类型为ArrayMap<String, File>等待后续处理。
注释2处如果这个系统App的升级包信息存储在mDisabledSysPackages列表中，但是没有发现这个升级包存在，则将它加入到possiblyDeletedUpdatedSystemApps列表中，意为“系统App的升级包可能被删除”，之所以是“可能”，是因为系统还没有扫描Data分区，只能暂放到possiblyDeletedUpdatedSystemApps列表中，等到扫描完Data分区后再做处理。
3、扫描Data分区阶段(BOOT_PROGRESS_PMS_DATA_SCAN_START)
//如果设备没有加密，那么就开始扫描Data分区
if (!mOnlyCore) {
//打印扫描Data分区阶段日志
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_DATA_SCAN_START,
SystemClock.uptimeMillis());
//扫描/data/app目录下的文件
scanDirTracedLI(mAppInstallDir, 0, scanFlags | SCAN_REQUIRE_KNOWN, 0);
//扫描/data/app-private目录下的文件
scanDirTracedLI(mDrmAppPrivateInstallDir, mDefParseFlags
| PackageParser.PARSE_FORWARD_LOCK,
scanFlags | SCAN_REQUIRE_KNOWN, 0);
//扫描/data/app-ephemeral目录下的文件
scanDirLI(mEphemeralInstallDir, mDefParseFlags
| PackageParser.PARSE_IS_EPHEMERAL,
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.
* 处理possiblyDeletedUpdatedSystemApps列表
*
*/
for (String deletedAppName : possiblyDeletedUpdatedSystemApps) {
PackageParser.Package deletedPkg = mPackages.get(deletedAppName);
mSettings.removeDisabledSystemPackageLPw(deletedAppName);
String msg;
if (deletedPkg == null) {
//1 如果这个系统App的包信息不在PMS的变量mPackages中，说明是残留的App信息，后续会删除它的数据
msg = "Updated system package " + deletedAppName
+ " no longer exists; it's data will be wiped";
// Actual deletion of code and data will be handled by later
// reconciliation step
} else {
//2 如果这个系统App在mPackages中，说明是存在于Data分区，不属于系统App，那么移除其系统权限。
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.
*/
//遍历mExpectingBetter列表
for (int i = 0; i < mExpectingBetter.size(); i++) {
final String packageName = mExpectingBetter.keyAt(i);
if (!mPackages.containsKey(packageName)) {
//得到系统App的升级包路径
final File scanFile = mExpectingBetter.valueAt(i);
logCriticalInfo(Log.WARN, "Expected better " + packageName
+ " but never showed up; reverting to system");
//3 根据系统App所在的目录设置扫描的解析参数
int reparseFlags = mDefParseFlags;
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;
}
//4 将packageName对应的包设置数据（PackageSetting）添加到mSettings的mPackages中
mSettings.enableSystemPackageLPw(packageName);
try {
//5 扫描系统App的升级包
scanPackageTracedLI(scanFile, reparseFlags, scanFlags, 0, null);
} catch (PackageManagerException e) {
Slog.e(TAG, "Failed to parse original system package: "
+ e.getMessage());
}
}
}
}
//清除mExpectingBetter列表
mExpectingBetter.clear();扫描Data分区阶段主要做了以下几件事：
- 扫描/data/app和/data/app-private目录下的文件。
- 遍历possiblyDeletedUpdatedSystemApps列表，注释1处如果这个系统App的包信息不在PMS的变量mPackages中，说明是残留的App信息，后续会删除它的数据。注释2处如果这个系统App的包信息在mPackages中，说明是存在于Data分区，不属于系统App，那么移除其系统权限。
- 遍历mExpectingBetter列表，注释3处根据系统App所在的目录设置扫描的解析参数，注释4处的方法内部会将packageName对应的包设置数据（PackageSetting）添加到mSettings的mPackages中。注释5处扫描系统App的升级包，最后清除mExpectingBetter列表。
4、扫描结束阶段(BOOT_PROGRESS_PMS_SCAN_END)
//打印扫描结束阶段日志
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_SCAN_END,
SystemClock.uptimeMillis());
// 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.
//当sdk版本不一致时，需要更新权限
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, StorageManager.UUID_PRIVATE_INTERNAL, 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.
//如果是第一次启动或者是Android M升级后的第一次启动，需要初始化所有用户定义的默认首选App
if (!onlyCore && (mPromoteSystemApps || mFirstBoot)) {
for (UserInfo user : sUserManager.getUsers(true)) {
mSettings.applyDefaultPreferredAppsLPw(this, user.id);
applyFactoryDefaultBrowserLPw(user.id);
primeDomainVerificationsLPw(user.id);
}
}
//在引导过程中尽早为系统用户准备存储，
//因为核心系统应用程序，如设置Provider和SystemUI无法等待用户启动
final int storageFlags;
if (StorageManager.isFileEncryptedNativeOrEmulated()) {
storageFlags = StorageManager.FLAG_STORAGE_DE;
} else {
storageFlags = StorageManager.FLAG_STORAGE_DE | StorageManager.FLAG_STORAGE_CE;
}
reconcileAppsDataLI(StorageManager.UUID_PRIVATE_INTERNAL, UserHandle.USER_SYSTEM,
storageFlags);
// If this is first boot after an OTA, and a normal boot, then
// we need to clear code cache directories.
// Note that we do *not* clear the application profiles. These remain valid
// across OTAs and are used to drive profile verification (post OTA) and
// profile compilation (without waiting to collect a fresh set of profiles).
// OTA后的第一次启动，会清除代码缓存目录
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)) {
// No apps are running this early, so no need to freeze
clearAppDataLIF(ps.pkg, UserHandle.USER_ALL,
StorageManager.FLAG_STORAGE_DE | StorageManager.FLAG_STORAGE_CE
| Installer.FLAG_CLEAR_CODE_CACHE_ONLY);
}
}
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;
// All the changes are done during package scanning.
ver.databaseVersion = Settings.CURRENT_DATABASE_VERSION;
// 把Settings的内容保存到packages.xml中
mSettings.writeLPr();扫描结束结束阶段主要做了以下几件事：
- 如果当前平台SDK版本和上次启动时的SDK版本不同，重新更新APK的授权。
- 如果是第一次启动或者是Android M升级后的第一次启动，需要初始化所有用户定义的默认首选App。
- OTA升级后的第一次启动，会清除代码缓存目录。
- 把Settings的内容保存到packages.xml中，这样此后PMS再次创建时会读到此前保存的Settings的内容。
5、准备阶段(BOOT_PROGRESS_PMS_READY)
//打印准备阶段日志
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_READY,
SystemClock.uptimeMillis());
if (!mOnlyCore) {
mRequiredVerifierPackage = getRequiredButNotReallyRequiredVerifierLPr();
mRequiredInstallerPackage = getRequiredInstallerLPr();
mRequiredUninstallerPackage = getRequiredUninstallerLPr();
mIntentFilterVerifierComponent = getIntentFilterVerifierComponentNameLPr();
mIntentFilterVerifier = new IntentVerifierProxy(mContext,
mIntentFilterVerifierComponent);
mServicesSystemSharedLibraryPackageName = getRequiredSharedLibraryLPr(
PackageManager.SYSTEM_SHARED_LIBRARY_SERVICES);
mSharedSystemSharedLibraryPackageName = getRequiredSharedLibraryLPr(
PackageManager.SYSTEM_SHARED_LIBRARY_SHARED);
} else {
mRequiredVerifierPackage = null;
if (mOnlyPowerOffAlarm) {
mRequiredInstallerPackage = getRequiredInstallerLPr();
} else {
mRequiredInstallerPackage = null;
}
mRequiredUninstallerPackage = null;
mIntentFilterVerifierComponent = null;
mIntentFilterVerifier = null;
mServicesSystemSharedLibraryPackageName = null;
mSharedSystemSharedLibraryPackageName = null;
}
//创建PackageInstallerService，用于管理安装会话的服务，它会为每次安装过程分配一个SessionId
mInstallerService = new PackageInstallerService(context, this);
//进行一次垃圾收集
untime.getRuntime().gc();
// The initial scanning above does many calls into installd while
// holding the mPackages lock, but we're mostly interested in yelling
// once we have a booted system.
mInstaller.setWarnIfHeld(mPackages);
// 将PackageManagerInternalImpl（PackageManager的本地服务）添加到LocalServices中，LocalServices用于存储运行在当前的进程中的本地服务
LocalServices.addService(PackageManagerInternal.class, new PackageManagerInternalImpl());总结
PMS属于引导服务，由SyetemServer启动，PMS启动又分为5个阶段：
- BOOT_PROGRESS_PMS_START（开始阶段）
- BOOT_PROGRESS_PMS_SYSTEM_SCAN_START（扫描系统阶段）
- BOOT_PROGRESS_PMS_DATA_SCAN_START（扫描Data分区阶段）
- BOOT_PROGRESS_PMS_SCAN_END（扫描结束阶段）
- BOOT_PROGRESS_PMS_READY（准备阶段）
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