应用对于Android系统来说至关重要，系统会有几个时机对APP进行解析，一个是APK安装的时候会进行解析，还有一个就是系统在重启之后会进行解析，这里就简单的记录一下重启的时候APK的解析过程。
一、SystemServer
系统在启动之后从内核层启动第一个用户控件Init进程，再通过Init进程启动系统中第一个java 进程zygote，随之zygote fock出SystemServer，SystemServer再开始启动一些列系统服务，其中就包括PackageMangerService，在startBootstrapServices函数中：
java
public final void startBootstrapServices(TimingsTraceAndSlog timingsTraceAndSlog) {
.....
// 先调用了PackageManagerService的main函数
Pair<PackageManagerService, IPackageManager> main = PackageManagerService.main(context, installer, domainVerificationService, z, this.mOnlyCore);
// main 函数创建了PackageManagerService 和IPackageManager 的实例
this.mPackageManagerService = (PackageManagerService) main.first;
IPackageManager iPackageManager = (IPackageManager) main.second;
Watchdog.getInstance().resumeWatchingCurrentThread("packagemanagermain");
// 该方法将在 BaseDexClassLoader 中安装一个报告器，同时还将强制报告系统服务器已加载的任何 dex 文件
SystemServerDexLoadReporter.configureSystemServerDexReporter(iPackageManager);
this.mFirstBoot = this.mPackageManagerService.isFirstBoot();
this.mPackageManager = this.mSystemContext.getPackageManager();二、PackageManagerService
在SystemServer中是先调用PackageManagerService的main函数来初始化它自己的，来看看它做了什么：
java
public static Pair<PackageManagerService, IPackageManager> main(Context context,
Installer installer, @NonNull DomainVerificationService domainVerificationService,
boolean factoryTest, boolean onlyCore) {
PackageManagerServiceCompilerMapping.checkProperties();
final TimingsTraceAndSlog t = new TimingsTraceAndSlog(TAG + "Timing",
Trace.TRACE_TAG_PACKAGE_MANAGER);
t.traceBegin("create package manager");
final PackageManagerTracedLock lock = new PackageManagerTracedLock();
final Object installLock = new Object();
// 创建自带handler的线程
HandlerThread backgroundThread = new ServiceThread("PackageManagerBg",
Process.THREAD_PRIORITY_BACKGROUND, true /*allowIo*/);
backgroundThread.start();
Handler backgroundHandler = new Handler(backgroundThread.getLooper());
// 创建PackageManagerServiceInjector 用来持有管理其他一系列重要的类实例
PackageManagerServiceInjector injector = new PackageManagerServiceInjector(
context, lock, installer, installLock, new PackageAbiHelperImpl(),
backgroundHandler,
SYSTEM_PARTITIONS,
// 解析compnent的
(i, pm) -> new ComponentResolver(i.getUserManagerService(), pm.mUserNeedsBadging),
// 权限管理服务
(i, pm) -> PermissionManagerService.create(context,
i.getSystemConfig().getAvailableFeatures()),
// 用户管理服务
(i, pm) -> new UserManagerService(context, pm,
new UserDataPreparer(installer, installLock, context, onlyCore),
lock),
// 系统数据库，用来访问系统数据库的
(i, pm) -> new Settings(Environment.getDataDirectory(),
RuntimePermissionsPersistence.createInstance(),
i.getPermissionManagerServiceInternal(),
domainVerificationService, backgroundHandler, lock),
(i, pm) -> AppsFilterImpl.create(i,
i.getLocalService(PackageManagerInternal.class)),
// compat服务用来管理一些系统特性
(i, pm) -> (PlatformCompat) ServiceManager.getService("platform_compat"),
// 系统配置服务，预置的系统的权限、硬件feature还有其他的一些配置在这里面解析
(i, pm) -> SystemConfig.getInstance(),
// 在软件包上运行 dexopt 命令的辅助类。
(i, pm) -> new PackageDexOptimizer(i.getInstaller(), i.getInstallLock(),
i.getContext(), "*dexopt*"),
// dex 行为管理类会保存所有包的dex位置
(i, pm) -> new DexManager(i.getContext(), i.getPackageDexOptimizer(),
i.getInstaller(), i.getInstallLock()),
(i, pm) -> new ArtManagerService(i.getContext(), i.getInstaller(),
i.getInstallLock()),
(i, pm) -> ApexManager.getInstance(),
(i, pm) -> new ViewCompiler(i.getInstallLock(), i.getInstaller()),
(i, pm) -> (IncrementalManager)
i.getContext().getSystemService(Context.INCREMENTAL_SERVICE),
(i, pm) -> new DefaultAppProvider(() -> context.getSystemService(RoleManager.class),
() -> LocalServices.getService(UserManagerInternal.class)),
(i, pm) -> new DisplayMetrics(),
// 包解析类
(i, pm) -> new PackageParser2(pm.mSeparateProcesses, pm.mOnlyCore,
i.getDisplayMetrics(), pm.mCacheDir,
pm.mPackageParserCallback) /* scanningCachingPackageParserProducer */,
(i, pm) -> new PackageParser2(pm.mSeparateProcesses, pm.mOnlyCore,
i.getDisplayMetrics(), null,
pm.mPackageParserCallback) /* scanningPackageParserProducer */,
(i, pm) -> new PackageParser2(pm.mSeparateProcesses, false, i.getDisplayMetrics(),
null, pm.mPackageParserCallback) /* preparingPackageParserProducer */,
// Prepare a supplier of package parser for the staging manager to parse apex file
// during the staging installation.
// 包安装服务
(i, pm) -> new PackageInstallerService(
i.getContext(), pm, i::getScanningPackageParser),
(i, pm, cn) -> new InstantAppResolverConnection(
i.getContext(), cn, Intent.ACTION_RESOLVE_INSTANT_APP_PACKAGE),
(i, pm) -> new ModuleInfoProvider(i.getContext()),
(i, pm) -> LegacyPermissionManagerService.create(i.getContext()),
(i, pm) -> domainVerificationService,
(i, pm) -> {
HandlerThread thread = new ServiceThread(TAG,
Process.THREAD_PRIORITY_DEFAULT, true /*allowIo*/);
thread.start();
return new PackageHandler(thread.getLooper(), pm);
},
new DefaultSystemWrapper(),
LocalServices::getService,
context::getSystemService,
(i, pm) -> new BackgroundDexOptService(i.getContext(), i.getDexManager(), pm),
(i, pm) -> IBackupManager.Stub.asInterface(ServiceManager.getService(
Context.BACKUP_SERVICE)),
(i, pm) -> new SharedLibrariesImpl(pm, i));
if (Build.VERSION.SDK_INT <= 0) {
Slog.w(TAG, "**** ro.build.version.sdk not set!");
}
// 初始化PackageManagerService
PackageManagerService m = new PackageManagerService(injector, onlyCore, factoryTest, PackagePartitions.FINGERPRINT, Build.IS_ENG, Build.IS_USERDEBUG, Build.VERSION.SDK_INT, Build.VERSION.INCREMENTAL);
t.traceEnd(); // "create package manager"
final CompatChange.ChangeListener selinuxChangeListener = packageName -> {
synchronized (m.mInstallLock) {
final Computer snapshot = m.snapshotComputer();
final PackageStateInternal packageState =
snapshot.getPackageStateInternal(packageName);
if (packageState == null) {
Slog.e(TAG, "Failed to find package setting " + packageName);
return;
}
AndroidPackage pkg = packageState.getPkg();
SharedUserApi sharedUser = snapshot.getSharedUser(
packageState.getSharedUserAppId());
String oldSeInfo = AndroidPackageUtils.getSeInfo(pkg, packageState);
if (pkg == null) {
Slog.e(TAG, "Failed to find package " + packageName);
return;
}
final String newSeInfo = SELinuxMMAC.getSeInfo(pkg, sharedUser,
m.mInjector.getCompatibility());
if (!newSeInfo.equals(oldSeInfo)) {
Slog.i(TAG, "Updating seInfo for package " + packageName + " from: "
+ oldSeInfo + " to: " + newSeInfo);
m.commitPackageStateMutation(null, packageName,
state -> state.setOverrideSeInfo(newSeInfo));
m.mAppDataHelper.prepareAppDataAfterInstallLIF(pkg);
}
}
};
//监听selinux的一些变化
injector.getCompatibility().registerListener(SELinuxMMAC.SELINUX_LATEST_CHANGES,
selinuxChangeListener);
injector.getCompatibility().registerListener(SELinuxMMAC.SELINUX_R_CHANGES,
selinuxChangeListener);
// ota完或者第一次开机为所有用户安装其被
m.installAllowlistedSystemPackages();
// 初始化 IPackageManagerImpl
IPackageManagerImpl iPackageManager = m.new IPackageManagerImpl();
ServiceManager.addService("package", iPackageManager);
// 初始化PackageManagerNative
final PackageManagerNative pmn = new PackageManagerNative(m);
ServiceManager.addService("package_native", pmn);
LocalManagerRegistry.addManager(PackageManagerLocal.class, m.new PackageManagerLocalImpl());
return Pair.create(m, iPackageManager);
}简单的介绍了一下main，下面重头戏在PackageManagerService的初始化过程，它总共有两个构造函数，注意一个只做了赋值，我们这里调用的不是这个构造函数而是另一个
java
public PackageManagerService(PackageManagerServiceInjector injector, boolean onlyCore,
boolean factoryTest, final String buildFingerprint, final boolean isEngBuild,
final boolean isUserDebugBuild, final int sdkVersion, final String incrementalVersion) {
mIsEngBuild = isEngBuild;
......
// 这里部分主要是给PackageMangerService的一些属性赋值
......
// CHECKSTYLE:ON IndentationCheck
t.traceEnd();
t.traceBegin("addSharedUsers");
// 注册各种UID
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);
mSettings.addSharedUserLPw("android.uid.se", SE_UID,
ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);
mSettings.addSharedUserLPw("android.uid.networkstack", NETWORKSTACK_UID,
ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);
mSettings.addSharedUserLPw("android.uid.uwb", UWB_UID,
ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);
t.traceEnd();
......
// 又是一堆初始化赋值
......
// 从systemconfig获取对于机器来说可用的硬件feature，可以在这里之前对feature进行修改
t.traceBegin("get system config");
SystemConfig systemConfig = injector.getSystemConfig();
mAvailableFeatures = systemConfig.getAvailableFeatures();
t.traceEnd();
......
// 这里是读取在mac_permissions.xml下面配置的一些se策略可以有效的限制一些应用的权限
SELinuxMMAC.readInstallPolicy();
......
final VersionInfo ver = mSettings.getInternalVersion();
// 指纹信息是否有更新
mIsUpgrade =
!buildFingerprint.equals(ver.fingerprint);
if (mIsUpgrade) {
PackageManagerServiceUtils.logCriticalInfo(Log.INFO, "Upgrading from "
+ ver.fingerprint + " to " + PackagePartitions.FINGERPRINT);
}
mInitAppsHelper = new InitAppsHelper(this, mApexManager, mInstallPackageHelper,
mInjector.getSystemPartitions());
// when upgrading from pre-M, promote system app permissions from install to runtime
// 是否从M升上来
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.
// 是否从N 升上来
mIsPreNUpgrade = mIsUpgrade && ver.sdkVersion < Build.VERSION_CODES.N;
// 是否从n mr升上来
mIsPreNMR1Upgrade = mIsUpgrade && ver.sdkVersion < Build.VERSION_CODES.N_MR1;
// 是否从Q升上来
mIsPreQUpgrade = mIsUpgrade && ver.sdkVersion < Build.VERSION_CODES.Q;
......
// 根据不同的版本类型创建缓存目录，如果已存在则不创建
mCacheDir = PackageManagerServiceUtils.preparePackageParserCache(
mIsEngBuild, mIsUserDebugBuild, mIncrementalVersion);
final int[] userIds = mUserManager.getUserIds();
PackageParser2 packageParser = mInjector.getScanningCachingPackageParser();
// 初始化安装系统级APP
mOverlayConfig = mInitAppsHelper.initSystemApps(packageParser, packageSettings, userIds,
startTime);
// 初始化安装非系统级APP
mInitAppsHelper.initNonSystemApps(packageParser, userIds, startTime);
packageParser.close();
......
}可以从上面PackageManagerService的初始化可以看到，机器开机的时候安装APP的任务是交给InitAppsHelper这个类来做的，两个函数一个initSystemApps一个initNonSystemApps，分别是初始化系统app和非系统app，两个函数都是对系统中的应用进行安装解析，区别就是针对系统app还是非系统app，我们先从系统app来看看。
三、InitAppsHelper
java
public OverlayConfig initSystemApps(PackageParser2 packageParser,
WatchedArrayMap<String, PackageSetting> packageSettings,
int[] userIds, long startTime) initSystemApps有四个参数，看下其中比较重要的两个参数怎么来的
1、PackageParser2
第一个参数实在PackageManagerService初始化的时候从mInjector获取的，而这里的PackageParser2是在PackaManagerService的main函数初始化的
java
PackageParser2 packageParser = mInjector.getScanningCachingPackageParser();2、WatchedArrayMap<String, PackageSetting>
首先这个参数是通过PackageMangerService的成员变量mSettings获取：
java
final WatchedArrayMap<String, PackageSetting> packageSettings =
mSettings.getPackagesLocked();Settings.getPackagesLocked
java
WatchedArrayMap<String, PackageSetting> getPackagesLocked() {
return mPackages;
}Settings.addPackageLPw 中添加数据
java
PackageSetting addPackageLPw(String name, String realName, File codePath, int uid, int pkgFlags,
int pkgPrivateFlags, @NonNull UUID domainSetId) {
PackageSetting p = mPackages.get(name);
if (p != null) {
if (p.getAppId() == uid) {
return p;
}
PackageManagerService.reportSettingsProblem(Log.ERROR,
"Adding duplicate package, keeping first: " + name);
return null;
}
p = new PackageSetting(name, realName, codePath, pkgFlags, pkgPrivateFlags, domainSetId)
.setAppId(uid);
if (mAppIds.registerExistingAppId(uid, p, name)) {
mPackages.put(name, p);
return p;
}
return null;
}Settings.readSettingsLPw，这个函数中对应用的一些配置信息进行解析，这些信息主要是存在/data/system目录下面
java
boolean readSettingsLPw(@NonNull Computer computer, @NonNull List<UserInfo> users,
ArrayMap<String, Long> originalFirstInstallTimes) {
mPendingPackages.clear();
mInstallerPackages.clear();
originalFirstInstallTimes.clear();
ArrayMap<Long, Integer> keySetRefs = new ArrayMap<>();
ArrayList<Signature> readSignatures = new ArrayList<>();
// 获取一系列配置文件，文件位于/data/system/下面，在setings初始化的时候被赋值
/**
mSystemDir = new File(dataDir, "system");
mSystemDir.mkdirs();
mSettingsFilename = new File(mSystemDir, "packages.xml");
mSettingsReserveCopyFilename = new File(mSystemDir, "packages.xml.reservecopy");
mPreviousSettingsFilename = new File(mSystemDir, "packages-backup.xml");
下面就是对这些配置文件进行解析
*/
try (ResilientAtomicFile atomicFile = getSettingsFile()) {
FileInputStream str = null;
try {
str = atomicFile.openRead();
if (str == null) {
// Not necessary, but will avoid wtf-s in the "finally" section.
findOrCreateVersion(StorageManager.UUID_PRIVATE_INTERNAL).forceCurrent();
findOrCreateVersion(StorageManager.UUID_PRIMARY_PHYSICAL).forceCurrent();
return false;
}
final TypedXmlPullParser parser = Xml.resolvePullParser(str);
int type;
while ((type = parser.next()) != XmlPullParser.START_TAG
&& type != XmlPullParser.END_DOCUMENT) {
// nothing
}
if (type != XmlPullParser.START_TAG) {
mReadMessages.append("No start tag found in settings file\n");
PackageManagerService.reportSettingsProblem(Log.WARN,
"No start tag found in package manager settings");
Slog.wtf(PackageManagerService.TAG,
"No start tag found in package manager settings");
return false;
}
int outerDepth = parser.getDepth();
while ((type = parser.next()) != XmlPullParser.END_DOCUMENT
&& (type != XmlPullParser.END_TAG || parser.getDepth() > outerDepth)) {
if (type == XmlPullParser.END_TAG || type == XmlPullParser.TEXT) {
continue;
}
String tagName = parser.getName();
if (tagName.equals("package")) {
//读取包信息
readPackageLPw(parser, readSignatures, keySetRefs, users,
originalFirstInstallTimes);
} else if (tagName.equals("permissions")) {
mPermissions.readPermissions(parser);
} else if (tagName.equals("permission-trees")) {
mPermissions.readPermissionTrees(parser);
} else if (tagName.equals("shared-user")) {
readSharedUserLPw(parser, readSignatures, users);
} else if (tagName.equals("preferred-packages")) {
// no longer used.
} else if (tagName.equals("preferred-activities")) {
// Upgrading from old single-user implementation;
// these are the preferred activities for user 0.
readPreferredActivitiesLPw(parser, 0);
} else if (tagName.equals(TAG_PERSISTENT_PREFERRED_ACTIVITIES)) {
// TODO: check whether this is okay! as it is very
// similar to how preferred-activities are treated
readPersistentPreferredActivitiesLPw(parser, 0);
} else if (tagName.equals(TAG_CROSS_PROFILE_INTENT_FILTERS)) {
// TODO: check whether this is okay! as it is very
// similar to how preferred-activities are treated
readCrossProfileIntentFiltersLPw(parser, 0);
} else if (tagName.equals(TAG_DEFAULT_BROWSER)) {
readDefaultAppsLPw(parser, 0);
} else if (tagName.equals("updated-package")) {
readDisabledSysPackageLPw(parser, users);
} else if (tagName.equals("renamed-package")) {
String nname = parser.getAttributeValue(null, "new");
String oname = parser.getAttributeValue(null, "old");
if (nname != null && oname != null) {
mRenamedPackages.put(nname, oname);
}
} else if (tagName.equals("last-platform-version")) {
// Upgrade from older XML schema
final VersionInfo internal = findOrCreateVersion(
StorageManager.UUID_PRIVATE_INTERNAL);
final VersionInfo external = findOrCreateVersion(
StorageManager.UUID_PRIMARY_PHYSICAL);
internal.sdkVersion = parser.getAttributeInt(null, "internal", 0);
external.sdkVersion = parser.getAttributeInt(null, "external", 0);
internal.buildFingerprint = external.buildFingerprint =
XmlUtils.readStringAttribute(parser, "buildFingerprint");
internal.fingerprint = external.fingerprint =
XmlUtils.readStringAttribute(parser, "fingerprint");
} else if (tagName.equals("database-version")) {
// Upgrade from older XML schema
final VersionInfo internal = findOrCreateVersion(
StorageManager.UUID_PRIVATE_INTERNAL);
final VersionInfo external = findOrCreateVersion(
StorageManager.UUID_PRIMARY_PHYSICAL);
internal.databaseVersion = parser.getAttributeInt(null, "internal", 0);
external.databaseVersion = parser.getAttributeInt(null, "external", 0);
} else if (tagName.equals("verifier")) {
final String deviceIdentity = parser.getAttributeValue(null, "device");
mVerifierDeviceIdentity = VerifierDeviceIdentity.parse(deviceIdentity);
} else if (TAG_READ_EXTERNAL_STORAGE.equals(tagName)) {
// No longer used.
} else if (tagName.equals("keyset-settings")) {
mKeySetManagerService.readKeySetsLPw(parser, keySetRefs);
} else if (TAG_VERSION.equals(tagName)) {
final String volumeUuid = XmlUtils.readStringAttribute(parser,
ATTR_VOLUME_UUID);
final VersionInfo ver = findOrCreateVersion(volumeUuid);
ver.sdkVersion = parser.getAttributeInt(null, ATTR_SDK_VERSION);
ver.databaseVersion = parser.getAttributeInt(null, ATTR_DATABASE_VERSION);
ver.buildFingerprint = XmlUtils.readStringAttribute(parser,
ATTR_BUILD_FINGERPRINT);
ver.fingerprint = XmlUtils.readStringAttribute(parser, ATTR_FINGERPRINT);
} else if (tagName.equals(
DomainVerificationPersistence.TAG_DOMAIN_VERIFICATIONS)) {
mDomainVerificationManager.readSettings(computer, parser);
} else if (tagName.equals(
DomainVerificationLegacySettings.TAG_DOMAIN_VERIFICATIONS_LEGACY)) {
mDomainVerificationManager.readLegacySettings(parser);
} else {
Slog.w(PackageManagerService.TAG, "Unknown element under <packages>: "
+ parser.getName());
XmlUtils.skipCurrentTag(parser);
}
}
str.close();
} catch (IOException | XmlPullParserException | ArrayIndexOutOfBoundsException e) {
// Remove corrupted file and retry.
atomicFile.failRead(str, e);
// Ignore the result to not mark this as a "first boot".
readSettingsLPw(computer, users, originalFirstInstallTimes);
}
}
return true;
}从上面的函数可以看出Settings这个类的主要职责就是存储修改解析应用的配置信息，这里涉及的东西比较多，不再赘述有兴趣可以自行查阅相关源码。
java
mFirstBoot = !mSettings.readLPw(computer,
mInjector.getUserManagerInternal().getUsers(
/* excludePartial= */ true,
/* excludeDying= */ false,
/* excludePreCreated= */ false));这里是Settings解析的开始在PackageMangerService的构造函数中，这是第二个参数的由来，接着第三个四个参数就比较简单分别是uid和时间戳。
篇幅有限下一篇展开细说