installd进程流程分析

installd服务启动

在systemserver中installer服务作为一个重要服务在：startBootstrapServices中启动：

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

installer代码较为简洁，主要为一些创建、删除应用目录、创建、删除odex文件，创建、删除oat文件、计算app大小、迁移app等功能：

    private void connect() {
        获取installd守护进程的binder
        IBinder binder = ServiceManager.getService("installd");
        if (binder != null) {
            try {
                binder.linkToDeath(new DeathRecipient() {
                    @Override
                    public void binderDied() {
                        Slog.w(TAG, "installd died; reconnecting");
                        connect();
                    }
                }, 0);
            } catch (RemoteException e) {
                binder = null;
            }
        }

        if (binder != null) {
            获取installd服务的代理
            mInstalld = IInstalld.Stub.asInterface(binder);
            try {
                invalidateMounts();
            } catch (InstallerException ignored) {
            }
        } else {
            Slog.w(TAG, "installd not found; trying again");
            BackgroundThread.getHandler().postDelayed(() -> {
                connect();
            }, DateUtils.SECOND_IN_MILLIS);
        }
    }

举例：清除应用数据目录：

    public long createAppData(String uuid, String packageName, int userId, int flags, int appId,
            String seInfo, int targetSdkVersion) throws InstallerException {
        if (!checkBeforeRemote()) return -1;
        try {
            调用installd守护进程完成真正工作
            return mInstalld.createAppData(uuid, packageName, userId, flags, appId, seInfo,
                    targetSdkVersion);
        } catch (Exception e) {
            throw InstallerException.from(e);
        }
    }

\frameworks\native\cmds\installd\Android.bp编译文件中：

cc_binary {
    name: "installd",
    defaults: ["installd_defaults"],
    srcs: ["installd.cpp"],

    static_libs: ["libdiskusage"],

    init_rc: ["installd.rc"],
}

installd.cpp中主函数如下：

int main(const int argc, char *argv[]) {
    return android::installd::installd_main(argc, argv);
}

static int installd_main(const int argc ATTRIBUTE_UNUSED, char *argv[]) {
    int ret;
    int selinux_enabled = (is_selinux_enabled() > 0);

    setenv("ANDROID_LOG_TAGS", "*:v", 1);
    android::base::InitLogging(argv);

    SLOGI("installd firing up");

    union selinux_callback cb;
    cb.func_log = log_callback;
    selinux_set_callback(SELINUX_CB_LOG, cb);
    初始化android全局路径，data，app，protected app，ephemeral app，app native library，sd-card ASEC mount point，media，external app，profiles，system and vendor directories.
    if (!initialize_globals()) {
        SLOGE("Could not initialize globals; exiting.\n");
        exit(1);
    }
    初始化路径
    if (initialize_directories() < 0) {
        SLOGE("Could not create directories; exiting.\n");
        exit(1);
    }

    if (selinux_enabled && selinux_status_open(true) < 0) {
        SLOGE("Could not open selinux status; exiting.\n");
        exit(1);
    }
    启动InstalldNativeService
    if ((ret = InstalldNativeService::start()) != android::OK) {
        SLOGE("Unable to start InstalldNativeService: %d", ret);
        exit(1);
    }

    IPCThreadState::self()->joinThreadPool();

    LOG(INFO) << "installd shutting down";

    return 0;
}

InstalldNativeService：

start中将该服务发布到了native层的servicemanager中：

status_t InstalldNativeService::start() {
    IPCThreadState::self()->disableBackgroundScheduling(true);
    将InstalldNativeService服务发布到native层的ServiceManager中
    status_t ret = BinderService::publish();
    if (ret != android::OK) {
        return ret;
    }
    sp ps(ProcessState::self());
    ps->startThreadPool();
    ps->giveThreadPoolName();
    return android::OK;
}

查看InstalldNativeService.h定义如下：

class InstalldNativeService : public BinderService, public os::BnInstalld {

BinderService.cpp:

static status_t publish(bool allowIsolated = false) {
        sp sm(defaultServiceManager());
        将服务加入到ServiceManager中
        return sm->addService(
                String16(SERVICE::getServiceName()),
                new SERVICE(), allowIsolated);
    }

所有的install.java中定义功能最终都是通过binder调用了native层的查看InstalldNativeService来实现，如：

binder::Status InstalldNativeService::clearAppProfiles(const std::string& packageName) {
    ENFORCE_UID(AID_SYSTEM);
    CHECK_ARGUMENT_PACKAGE_NAME(packageName);
    std::lock_guard lock(mLock);

    binder::Status res = ok();
    if (!clear_primary_reference_profile(packageName)) {
        res = error("Failed to clear reference profile for " + packageName);
    }
    if (!clear_primary_current_profiles(packageName)) {
        res = error("Failed to clear current profiles for " + packageName);
    }
    return res;
}


binder::Status InstalldNativeService::clearAppData(const std::unique_ptr& uuid,
        const std::string& packageName, int32_t userId, int32_t flags, int64_t ceDataInode) {
    ENFORCE_UID(AID_SYSTEM);
    CHECK_ARGUMENT_UUID(uuid);
    CHECK_ARGUMENT_PACKAGE_NAME(packageName);
    std::lock_guard lock(mLock);

    const char* uuid_ = uuid ? uuid->c_str() : nullptr;
    const char* pkgname = packageName.c_str();

    binder::Status res = ok();
    if (flags & FLAG_STORAGE_CE) {
        auto path = create_data_user_ce_package_path(uuid_, userId, pkgname, ceDataInode);
        if (flags & FLAG_CLEAR_CACHE_ONLY) {
            path = read_path_inode(path, "cache", kXattrInodeCache);
        } else if (flags & FLAG_CLEAR_CODE_CACHE_ONLY) {
            path = read_path_inode(path, "code_cache", kXattrInodeCodeCache);
        }
        if (access(path.c_str(), F_OK) == 0) {
            if (delete_dir_contents(path) != 0) {
                res = error("Failed to delete contents of " + path);
            }
        }
    }
    if (flags & FLAG_STORAGE_DE) {
        std::string suffix = "";
        bool only_cache = false;
        if (flags & FLAG_CLEAR_CACHE_ONLY) {
            suffix = CACHE_DIR_POSTFIX;
            only_cache = true;
        } else if (flags & FLAG_CLEAR_CODE_CACHE_ONLY) {
            suffix = CODE_CACHE_DIR_POSTFIX;
            only_cache = true;
        }

        auto path = create_data_user_de_package_path(uuid_, userId, pkgname) + suffix;
        if (access(path.c_str(), F_OK) == 0) {
            if (delete_dir_contents(path) != 0) {
                res = error("Failed to delete contents of " + path);
            }
        }
        if (!only_cache) {
            if (!clear_primary_current_profile(packageName, userId)) {
                res = error("Failed to clear current profile for " + packageName);
            }
        }
    }
    return res;
}