全面解析Android系统指纹启动流程-编程学习网

本章主要整理Android 指纹启动流程，侧重于hal和framework部分。

一.从Android系统启动流程看指纹启动流程

下图图片出处 →

第一阶段

Boot ROM，Android设备上电后，首先会从处理器片上ROM的启动引导代码开始执行，片上ROM会寻找Bootloader代码，并加载到内存。主要就是上电让系统启动。

第二阶段

Bootloader开始执行，首先负责完成硬件的初始化，然后找到Linux内核代码，并加载到内存。

启动过程中，bootloader(默认是bootable/bootloader/lk)会根据机器硬件信息选择合适的devicetree（dts）装入内存，如果采用pin id兼容，那么在此时就可以通过读取ID pin的值（这个是硬件拉的，跟硬件工程师确认是怎么对应IC的即可）判断指纹的IC了。

第三阶段

Kernel，Linux内核开始启动，初始化各种软硬件环境，加载驱动程序，挂载根文件系统，在系统文件中寻找init.rc文件，并启动init进程。Kernel中，加载指纹驱动，根据传入的dts信息创建设备节点，注册设备。

第四阶段

Init，初始化和启动属性服务，并且启动Zygote进程。

找到android.hardware.biometrics.fingerprint@2.1-service.rc，启动android.hardware.biometrics.fingerprint@2.1-service，会去open fingerprint.deault.so，等待与上层通信。

第五阶段

Zygote进程启动，创建java虚拟机并为java虚拟机注册JNI方法，创建服务器端Socket，启动SystemServer进程。

第六阶段

SystemServer进程启动，启动Binder线程池和SystemServiceManager，并且启动各种系统服务。会启动Fingerprintservice

以上是从Android启动流程看每个阶段指纹的启动流程，下面依次详细展开介绍。

二.驱动层

主要就是设备节点驱动的注册，在此不再详细说了，重点关注probe函数。

三.hal层

首先，hardware/interfaces/biometrics/fingerprint/2.1/default/android.hardware.biometrics.fingerprint@2.1-service.rc（以下简称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

会使位于系统vendor/bin/hw下的android.hardware.biometrics.fingerprint@2.1-service（以下简称2.1 bin）开机自启动，启动后会注册2.1 service

该bin服务对应的代码在：hardware/interfaces/biometrics/fingerprint/2.1/default/service.cpp，整个注册过程只有两步，首先实例化传入的 IBiometricsFingerprint 接口对象，然后通过 registerAsService 将服务注册到 hwservicemanager。


int main() {
    android::sp<IBiometricsFingerprint> bio = BiometricsFingerprint::getInstance();
 
    configureRpcThreadpool(1, true );
 
    if (bio != nullptr) {
        if (::android::OK != bio->registerAsService()) { //
 
 
 
 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;
    }

对FingerprintService再往上一层的封装是FingerprintManager，应用app可以直接和它通信

frameworks/base/core/java/android/hardware/fingerprint/FingerprintManager.java （以下为搜索mService的代码，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());

以上代码大家可以发现FingerprintManager其实并没有真正实现什么接口，都是调用的IFingerprintService，这里就用到aidl了，FingerprintManager通过aidl的Stub获取了Fingerprintservice，然后在这里去调用这个service的方法，以操作service，这就是aidl的作用。

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


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.总结

根据以上可以画出这样一张流程图（以下以汇顶指纹为例，流程上都是一样的）

System APP下发注册命令->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->指纹CA收到命令->指纹TA收到命令->SPI采集数据\算法进行注册等

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