全面解析Android系統(tǒng)指紋啟動流程

更新時間：2021年04月12日 11:56:02 作者：追風(fēng)少女hrht

這篇文章主要介紹了全面解析Android系統(tǒng)指紋啟動流程，對Android啟動原理感興趣的同學(xué)可以參考下

本章主要整理Android 指紋啟動流程，側(cè)重于hal和framework部分。

一.從Android系統(tǒng)啟動流程看指紋啟動流程

下圖圖片出處 →

第一階段

Boot ROM，Android設(shè)備上電后，首先會從處理器片上ROM的啟動引導(dǎo)代碼開始執(zhí)行，片上ROM會尋找Bootloader代碼，并加載到內(nèi)存。主要就是上電讓系統(tǒng)啟動。

第二階段

Bootloader開始執(zhí)行，首先負責(zé)完成硬件的初始化，然后找到Linux內(nèi)核代碼，并加載到內(nèi)存。

啟動過程中，bootloader(默認是bootable/bootloader/lk)會根據(jù)機器硬件信息選擇合適的devicetree（dts）裝入內(nèi)存，如果采用pin id兼容，那么在此時就可以通過讀取ID pin的值（這個是硬件拉的，跟硬件工程師確認是怎么對應(yīng)IC的即可）判斷指紋的IC了。

第三階段

Kernel，Linux內(nèi)核開始啟動，初始化各種軟硬件環(huán)境，加載驅(qū)動程序，掛載根文件系統(tǒng)，在系統(tǒng)文件中尋找init.rc文件，并啟動init進程。Kernel中，加載指紋驅(qū)動，根據(jù)傳入的dts信息創(chuàng)建設(shè)備節(jié)點，注冊設(shè)備。

第四階段

Init，初始化和啟動屬性服務(wù)，并且啟動Zygote進程。

找到android.hardware.biometrics.fingerprint@2.1-service.rc，啟動android.hardware.biometrics.fingerprint@2.1-service，會去open fingerprint.deault.so，等待與上層通信。

第五階段

Zygote進程啟動，創(chuàng)建java虛擬機并為java虛擬機注冊JNI方法，創(chuàng)建服務(wù)器端Socket，啟動SystemServer進程。

第六階段

SystemServer進程啟動，啟動Binder線程池和SystemServiceManager，并且啟動各種系統(tǒng)服務(wù)。會啟動Fingerprintservice

以上是從Android啟動流程看每個階段指紋的啟動流程，下面依次詳細展開介紹。

二.驅(qū)動層

主要就是設(shè)備節(jié)點驅(qū)動的注冊，在此不再詳細說了，重點關(guān)注probe函數(shù)。

三.hal層

首先，hardware/interfaces/biometrics/fingerprint/2.1/default/android.hardware.biometrics.fingerprint@2.1-service.rc（以下簡稱2.1 rc）

service vendor.fps_hal /vendor/bin/hw/android.hardware.biometrics.fingerprint@2.1-service
    # "class hal" causes a race condition on some devices due to files created
    # in /data. As a workaround, postpone startup until later in boot once
    # /data is mounted.
    class late_start
    user system
    group system input
    writepid /dev/cpuset/system-background/tasks

會使位于系統(tǒng)vendor/bin/hw下的android.hardware.biometrics.fingerprint@2.1-service（以下簡稱2.1 bin）開機自啟動，啟動后會注冊2.1 service

該bin服務(wù)對應(yīng)的代碼在：hardware/interfaces/biometrics/fingerprint/2.1/default/service.cpp，整個注冊過程只有兩步，首先實例化傳入的 IBiometricsFingerprint 接口對象，然后通過 registerAsService 將服務(wù)注冊到 hwservicemanager。

int main() {
    android::sp<IBiometricsFingerprint> bio = BiometricsFingerprint::getInstance();
 
    configureRpcThreadpool(1, true /*callerWillJoin*/);
 
    if (bio != nullptr) {
        if (::android::OK != bio->registerAsService()) { //*****注冊服務(wù)*****
            return 1;
        }
    } else {
        ALOGE("Can't create instance of BiometricsFingerprint, nullptr");
    }
 
    joinRpcThreadpool();
 
    return 0; // should never get here
}

hardware/interfaces/biometrics/fingerprint/2.1/default/BiometricsFingerprint.cpp，重點關(guān)注openHal函數(shù)，會去打開fingerprint.default.so

fingerprint_device_t* BiometricsFingerprint::openHal() {
    int err;
    const hw_module_t *hw_mdl = nullptr;
    ALOGD("Opening fingerprint hal library...");
    //*******打開fingerprint.default.so********
    if (0 != (err = hw_get_module(FINGERPRINT_HARDWARE_MODULE_ID, &hw_mdl))) {
        ALOGE("Can't open fingerprint HW Module, error: %d", err);
        return nullptr;
    }
 
    if (hw_mdl == nullptr) {
        ALOGE("No valid fingerprint module");
        return nullptr;
    }
 
    fingerprint_module_t const *module =
        reinterpret_cast<const fingerprint_module_t*>(hw_mdl);
    if (module->common.methods->open == nullptr) {
        ALOGE("No valid open method");
        return nullptr;
    }
 
    hw_device_t *device = nullptr;
 
    if (0 != (err = module->common.methods->open(hw_mdl, nullptr, &device))) {
        ALOGE("Can't open fingerprint methods, error: %d", err);
        return nullptr;
    }
 
    if (kVersion != device->version) {
        // enforce version on new devices because of HIDL@2.1 translation layer
        ALOGE("Wrong fp version. Expected %d, got %d", kVersion, device->version);
        return nullptr;
    }
 
    fingerprint_device_t* fp_device =
        reinterpret_cast<fingerprint_device_t*>(device);
 
    if (0 != (err =
            fp_device->set_notify(fp_device, BiometricsFingerprint::notify))) {
        ALOGE("Can't register fingerprint module callback, error: %d", err);
        return nullptr;
    }
 
    return fp_device;
}

關(guān)于fingerprint.default.so這個都是供應(yīng)商提供的，一般都不開源，不過Android原生也是有這部分代碼的（當(dāng)然只是看看，并不能使用）

hardware/libhardware/include/hardware/fingerprint.h

hardware/libhardware/modules/fingerprint/fingerprint.c

這部分代碼不再展開貼在這里了，大家可以自行去看看，主要就是fingerprint_open打開設(shè)備（設(shè)備節(jié)點），然后定義了一系列函數(shù)。

dev->common.tag = HARDWARE_DEVICE_TAG;
dev->common.version = FINGERPRINT_MODULE_API_VERSION_2_0;
dev->common.module = (struct hw_module_t*) module;
dev->common.close = fingerprint_close;

dev->pre_enroll = fingerprint_pre_enroll;
dev->enroll = fingerprint_enroll;
dev->get_authenticator_id = fingerprint_get_auth_id;
dev->cancel = fingerprint_cancel;
dev->remove = fingerprint_remove;
dev->set_active_group = fingerprint_set_active_group;
dev->authenticate = fingerprint_authenticate;
dev->set_notify = set_notify_callback;

四.framework層

首先是SystemServer啟動后，會去判斷設(shè)備是否支持指紋，如果有start FingerprintService

frameworks/base/services/java/com/android/server/SystemServer.java

if (mPackageManager.hasSystemFeature(PackageManager.FEATURE_FINGERPRINT)) {
    traceBeginAndSlog("StartFingerprintSensor");
    mSystemServiceManager.startService(FingerprintService.class);
    traceEnd();
}

此處mPackageManager.hasSystemFeature(PackageManager.FEATURE_FINGERPRINT)的判斷，大家可以去frameworks/base/core/java/android/content/pm/PackageManager.java中追代碼看看，邏輯很簡單。

就是判斷系統(tǒng)內(nèi)vendor/etc/permissions目錄下是否有：android.hardware.fingerprint.xml 文件

調(diào)試的那篇說過這個配置是setting里有沒有指紋選項的關(guān)鍵：

PRODUCT_COPY_FILES := frameworks/native/data/etc/android.hardware.fingerprint.xml:vendor/etc/permissions/android.hardware.fingerprint.xml

下面轉(zhuǎn)到，frameworks/base/services/core/java/com/android/server/fingerprint/FingerprintService.java，以下代碼前半部分是與hal 2.1 service通信的部分，通過mDaemon = IBiometricsFingerprint.getService()，獲取2.1 service

后半部分可以看出其繼承IFingerprintService.aidl，這個aidl類就是實現(xiàn)Manager和Service通信的橋梁。

 public synchronized IBiometricsFingerprint getFingerprintDaemon() {
        if (mDaemon == null) {
            Slog.v(TAG, "mDaemon was null, reconnect to fingerprint");
            try {
                mDaemon = IBiometricsFingerprint.getService();
            } catch (java.util.NoSuchElementException e) {
                // Service doesn't exist or cannot be opened. Logged below.
            } catch (RemoteException e) {
                Slog.e(TAG, "Failed to get biometric interface", e);
            }
            if (mDaemon == null) {
                Slog.w(TAG, "fingerprint HIDL not available");
                return null;
            }
 
            mDaemon.asBinder().linkToDeath(this, 0);
 
            try {
                mHalDeviceId = mDaemon.setNotify(mDaemonCallback);
            } catch (RemoteException e) {
                Slog.e(TAG, "Failed to open fingerprint HAL", e);
                mDaemon = null; // try again later!
            }
 
            if (DEBUG) Slog.v(TAG, "Fingerprint HAL id: " + mHalDeviceId);
            if (mHalDeviceId != 0) {
                loadAuthenticatorIds();
                updateActiveGroup(ActivityManager.getCurrentUser(), null);
                doFingerprintCleanupForUser(ActivityManager.getCurrentUser());
            } else {
                Slog.w(TAG, "Failed to open Fingerprint HAL!");
                MetricsLogger.count(mContext, "fingerprintd_openhal_error", 1);
                mDaemon = null;
            }
 
 
 
 
 
//************************************************************************************//
 
 
 
 private final class FingerprintServiceWrapper extends IFingerprintService.Stub {
        @Override // Binder call
        public long preEnroll(IBinder token) {
            checkPermission(MANAGE_FINGERPRINT);
            return startPreEnroll(token);
        }
 
        @Override // Binder call
        public int postEnroll(IBinder token) {
            checkPermission(MANAGE_FINGERPRINT);
            return startPostEnroll(token);
        }
 
        @Override // Binder call
        public void enroll(final IBinder token, final byte[] cryptoToken, final int userId,
                final IFingerprintServiceReceiver receiver, final int flags,
                final String opPackageName) {
            checkPermission(MANAGE_FINGERPRINT);
            final int limit = mContext.getResources().getInteger(
                    com.android.internal.R.integer.config_fingerprintMaxTemplatesPerUser);
 
            final int enrolled = FingerprintService.this.getEnrolledFingerprints(userId).size();
            if (enrolled >= limit) {
                Slog.w(TAG, "Too many fingerprints registered");
                return;
            }
        }
        return mDaemon;
    }

對FingerprintService再往上一層的封裝是FingerprintManager，應(yīng)用app可以直接和它通信

frameworks/base/core/java/android/hardware/fingerprint/FingerprintManager.java （以下為搜索mService的代碼，大家可以自己去看看）

    private IFingerprintService mService;
        if (mService != null) try {
            mService.authenticate(mToken, sessionId, userId, mServiceReceiver, flags,
 
        if (mService != null) {
                mService.authenticate(mToken, sessionId, userId, mServiceReceiver,
               
        if (mService != null) try {
            mService.enroll(mToken, token, userId, mServiceReceiver, flags,
            
        if (mService != null) try {
            result = mService.preEnroll(mToken);
        if (mService != null) try {
            result = mService.postEnroll(mToken);
        if (mService != null) try {
            mService.setActiveUser(userId);
        if (mService != null) try {
            mService.remove(mToken, fp.getFingerId(), fp.getGroupId(), userId, mServiceReceiver);
            mService.remove(mToken, fp.getFingerId(), fp.getGroupId(), userId, mServiceReceiver);
        if (mService != null) try {
            mService.enumerate(mToken, userId, mServiceReceiver);
            
        if (mService != null) {
                mService.rename(fpId, userId, newName);
        if (mService != null) try {
            return mService.getEnrolledFingerprints(userId, mContext.getOpPackageName());
        if (mService != null) try {
            return mService.hasEnrolledFingerprints(
        if (mService != null) try {
            return mService.hasEnrolledFingerprints(userId, mContext.getOpPackageName());
        if (mService != null) {
                return mService.isHardwareDetected(deviceId, mContext.getOpPackageName());
        if (mService != null) {
                return mService.getAuthenticatorId(mContext.getOpPackageName());
        if (mService != null) {
                mService.resetTimeout(token);
        if (mService == null) {
        if (mService != null) try {
            mService.cancelEnrollment(mToken);
        if (mService != null) try {
            mService.cancelAuthentication(mToken, mContext.getOpPackageName());

以上代碼大家可以發(fā)現(xiàn)FingerprintManager其實并沒有真正實現(xiàn)什么接口，都是調(diào)用的IFingerprintService，這里就用到aidl了，F(xiàn)ingerprintManager通過aidl的Stub獲取了Fingerprintservice，然后在這里去調(diào)用這個service的方法，以操作service，這就是aidl的作用。

frameworks/base/core/java/android/hardware/fingerprint/IFingerprintService.aidl （大家如果去看完整的代碼，這里的接口是和FingerprintManager中調(diào)用的完全一致的）

interface IFingerprintService {
    // Authenticate the given sessionId with a fingerprint
    void authenticate(IBinder token, long sessionId, int userId,
            IFingerprintServiceReceiver receiver, int flags, String opPackageName,
            in Bundle bundle, IBiometricPromptReceiver dialogReceiver);
 
    // Cancel authentication for the given sessionId
    void cancelAuthentication(IBinder token, String opPackageName);
 
    // Start fingerprint enrollment
    void enroll(IBinder token, in byte [] cryptoToken, int groupId, IFingerprintServiceReceiver receiver,
            int flags, String opPackageName);
 
    // Cancel enrollment in progress
    void cancelEnrollment(IBinder token);
 
    // Any errors resulting from this call will be returned to the listener
    void remove(IBinder token, int fingerId, int groupId, int userId,
            IFingerprintServiceReceiver receiver);
 
    // Rename the fingerprint specified by fingerId and groupId to the given name
    void rename(int fingerId, int groupId, String name);
 
    // Get a list of enrolled fingerprints in the given group.
    List<Fingerprint> getEnrolledFingerprints(int groupId, String opPackageName);
 
    // Determine if HAL is loaded and ready
    boolean isHardwareDetected(long deviceId, String opPackageName);
 
    // Get a pre-enrollment authentication token
    long preEnroll(IBinder token);
 
    // Finish an enrollment sequence and invalidate the authentication token
    int postEnroll(IBinder token);

五.總結(jié)

根據(jù)以上可以畫出這樣一張流程圖（以下以匯頂指紋為例，流程上都是一樣的）

System APP下發(fā)注冊命令->FingerprintManager收到命令->FingerprintService收到命令->（2.1 service）BiometricsFingerprint收到命令->(fingerprint.default.so)Fingerprint.cpp收到命令->指紋CA收到命令->指紋TA收到命令->SPI采集數(shù)據(jù)\算法進行注冊等