如何调试SEGV_ACCERR

我有一个使用Kickflip和ButterflyTV libRTMP传输视频的应用程序

现在有99%的时间应用程序正常工作,但我不时会遇到一个我无法调试的本机分段错误,因为消息太含糊了:

01-24 10:52:25.576 199-199/? A/DEBUG: *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
01-24 10:52:25.576 199-199/? A/DEBUG: Build fingerprint: 'google/hammerhead/hammerhead:6.0.1/M4B30Z/3437181:user/release-keys'
01-24 10:52:25.576 199-199/? A/DEBUG: Revision: '11'
01-24 10:52:25.576 199-199/? A/DEBUG: ABI: 'arm'
01-24 10:52:25.576 199-199/? A/DEBUG: pid: 14302, tid: 14382, name: MuxerThread  >>> tv.myapp.broadcast.dev <<<
01-24 10:52:25.576 199-199/? A/DEBUG: signal 11 (SIGSEGV), code 2 (SEGV_ACCERR), fault addr 0x9fef1000
01-24 10:52:25.636 199-199/? A/DEBUG: Abort message: 'Setting to ready!'
01-24 10:52:25.636 199-199/? A/DEBUG:     r0 9c6f9500  r1 9c6f94fc  r2 9fee900c  r3 00007ff4
01-24 10:52:25.636 199-199/? A/DEBUG:     r4 9fee9010  r5 9fef0ffd  r6 00007ff1  r7 9fef0d88
01-24 10:52:25.636 199-199/? A/DEBUG:     r8 cfe40980  r9 9e0a6900  sl 00007ff4  fp 9c6f94fc
01-24 10:52:25.636 199-199/? A/DEBUG:     ip 9c6f9058  sp 9c6f94dc  lr 000000e9  pc b3a33cb6  cpsr 800f0030
01-24 10:52:25.650 199-199/? A/DEBUG: backtrace:
01-24 10:52:25.651 199-199/? A/DEBUG:     #00 pc 00004cb6  /data/app/tv.myapp.broadcast.dev-2/lib/arm/librtmp-jni.so
01-24 10:52:25.651 199-199/? A/DEBUG:     #01 pc 00005189  /data/app/tv.myapp.broadcast.dev-2/lib/arm/librtmp-jni.so (rtmp_sender_write_video_frame+28)
01-24 10:52:25.651 199-199/? A/DEBUG:     #02 pc 00005599  /data/app/tv.myapp.broadcast.dev-2/lib/arm/librtmp-jni.so (Java_net_butterflytv_rtmp_1client_RTMPMuxer_writeVideo+60)
01-24 10:52:25.651 199-199/? A/DEBUG:     #03 pc 014e84e7  /data/app/tv.myapp.broadcast.dev-2/oat/arm/base.odex (offset 0xa66000) (int net.butterflytv.rtmp_client.RTMPMuxer.writeVideo(byte[], int, int, int)+122)
01-24 10:52:25.651 199-199/? A/DEBUG:     #04 pc 014dbd55  /data/app/tv.myapp.broadcast.dev-2/oat/arm/base.odex (offset 0xa66000) (void io.kickflip.sdk.av.muxer.RtmpMuxerMix.writeThread()+2240)
01-24 10:52:25.651 199-199/? A/DEBUG:     #05 pc 014d8c41  /data/app/tv.myapp.broadcast.dev-2/oat/arm/base.odex (offset 0xa66000) (void io.kickflip.sdk.av.muxer.RtmpMuxerMix.access$000(io.kickflip.sdk.av.muxer.RtmpMuxerMix)+60)
01-24 10:52:25.651 199-199/? A/DEBUG:     #06 pc 014d819f  /data/app/tv.myapp.broadcast.dev-2/oat/arm/base.odex (offset 0xa66000) (void io.kickflip.sdk.av.muxer.RtmpMuxerMix$1.run()+98)
01-24 10:52:25.651 199-199/? A/DEBUG:     #07 pc 721e78d1  /data/dalvik-cache/arm/system@framework@boot.oat (offset 0x1ed6000)

同样,在2小时的流中,这可能不会发生,或者可能发生在流中10分钟.调试非常困难,因为我无法强制发生错误.

有没有办法改善我得到的调试信息？SEGV_ACCER究竟是什么意思？我已经读过这个"意味着你试图访问一个你无权访问的地址." 但我不确定这是什么意思,因为我可以在没有发生错误的情况下流几个小时.

有没有办法捕获信号并继续？

编辑:要添加更多信息,这是应用程序崩溃的本机库的一部分(使用ndk-stack找到):

JNIEXPORT jint JNICALL
Java_net_butterflytv_rtmp_1client_RTMPMuxer_writeVideo(JNIEnv *env, jobject instance,
                                                       jbyteArray data_, jint offset, jint length,
                                                       jint timestamp) {
    jbyte *data = (*env)->GetByteArrayElements(env, data_, NULL);
    jint result = rtmp_sender_write_video_frame(data, length, timestamp, 0, 0);
    (*env)->ReleaseByteArrayElements(env, data_, data, 0);

    return result;
}


int rtmp_sender_write_video_frame(uint8_t *data,
                                  int size,
                                  uint64_t dts_us,
                                  int key,
                                  uint32_t abs_ts)
{


    uint8_t * buf;
    uint8_t * buf_offset;
    int val = 0;
    int total;
    uint32_t ts;
    uint32_t nal_len;
    uint32_t nal_len_n;
    uint8_t *nal;
    uint8_t *nal_n;
    char *output ;
    uint32_t offset = 0;
    uint32_t body_len;
    uint32_t output_len;

    buf = data;
    buf_offset = data;
    total = size;
    ts = (uint32_t)dts_us;

    //ts = RTMP_GetTime() - start_time;
    offset = 0;

    nal = get_nal(&nal_len, &buf_offset, buf, total);

(...)


}



static uint8_t * get_nal(uint32_t *len, uint8_t **offset, uint8_t *start, uint32_t total)
{
    uint32_t info;
    uint8_t *q ;
    uint8_t *p  =  *offset;
    *len = 0;




    if ((p - start) >= total)
        return NULL;

    while(1) {
        info =  find_start_code(p, 3);

        if (info == 1)
            break;
        p++;
        if ((p - start) >= total)
            return NULL;
    }
    q = p + 4;
    p = q;

    while(1) {
        info =  find_start_code(p, 3);

        if (info == 1)
            break;
        p++;
        if ((p - start) >= total)
            //return NULL;
            break;
    }


    *len = (p - q);
    *offset = p;
    return q;
}


static uint32_t find_start_code(uint8_t *buf, uint32_t zeros_in_startcode)
{
    uint32_t info;
    uint32_t i;

    info = 1;
    if ((info = (buf[zeros_in_startcode] != 1)? 0: 1) == 0)
        return 0;

    for (i = 0; i < zeros_in_startcode; i++)
        if (buf[i] != 0)
        {
            info = 0;
            break;
        };

    return info;
}

崩溃发生buf[zeros_in_startcode]在find_start_code.我也删除了一些android_log行(不要认为这很重要？).

根据我的理解,这个缓冲区应该是可访问的,没有意义它只是"有时"崩溃.

PS.这是我从Java调用本机代码的地方:

private void writeThread() {

       while (true) {

           Frame frame = null;
           synchronized (mBufferLock) {
              if (!mConfigBuffer.isEmpty()) {
                   frame = mConfigBuffer.peek();
               } else if (!mBuffer.isEmpty()) {
                   frame = mBuffer.remove();
               }
               if (frame == null) {
                   try {
                       mBufferLock.wait();
                   } catch (InterruptedException e) {
                   }
               }
           }

           if (frame == null) {
               continue;
           } else if (frame instanceof Sentinel) {
               break;
           }


           int writeResult = 0;

           synchronized (mWriteFence) {
               if (!mConnected) {
                   debug(WARN, "Skipping frame due to disconnection");
                   continue;
               }

               if (frame.getFrameType() == Frame.VIDEO_FRAME) {              
                   writeResult = mRTMPMuxer.writeVideo(frame.getData(), frame.getOffset(), frame.getSize(), frame.getTime());
               } else if (frame.getFrameType() == Frame.AUDIO_FRAME) {
                   writeResult = mRTMPMuxer.writeAudio(frame.getData(), frame.getOffset(), frame.getSize(), frame.getTime());

               }

               if (writeResult < 0) {
                       mRtmpListener.onDisconnected();
                       mConnected = false;
               } else {
                   //Now we remove the config frame, only if sending was successful!
                   if (frame.isConfig()) {
                       synchronized (mBufferLock) {
                           mConfigBuffer.remove();
                       }
                   }
               }
           }

       }

   }

请注意,即使我根本不发送音频,也会发生崩溃.

"您可以将数据存储在a中byte[].这样可以非常快速地从托管代码访问.但是,在本机方面,您无法保证能够访问数据而无需复制它."

请参阅https://developer.android.com/training/articles/perf-jni.html

一些想法和事情要尝试:

它倒下的代码是非常通用的,所以可能没有错误

必须是frame数据已被删除/损坏/锁定/移动

Java垃圾收集器是否已删除或重新定位数据？

您可以将详细的调试写入文件,在每个帧上覆盖它,因此您只有一个包含最后调试信息的小日志.

发送frame变量信息(使用ByteBuffer)的本地副本mRTMPMuxer.writeVideo
与常规byte缓冲区不同,ByteBuffer存储未在托管上分配heap,并且始终可以直接从本机代码访问.

履行

//allocates memory from the native heap
ByteBuffer data = ByteBuffer.allocateDirect(frame.getData().length);
data.clear();
//System.gc();
//copy data
data.get(frame.getData(), 0, frame.getData().length);
//data = (frame.getData() == null) ? null : frame.getData().clone();
int offset  = frame.getOffset();
int size    = frame.getSize();
int time    = frame.getTime();
writeResult = mRTMPMuxer.writeVideo(data , offset, size, time);

JNIEXPORT jint JNICALL
Java_net_butterflytv_rtmp_1client_RTMPMuxer_writeVideo(
    JNIEnv *env,
    jobject instance,
    jobject data_, //NOT jbyteArray data_,
    jint offset,
    jint length,
    jint timestamp) 
{
    jbyte *data = env->GetDirectBufferAddress(env, data);//GetDirectBufferAddress NOT GetByteArrayElements
    jint result = rtmp_sender_write_video_frame(data, length, timestamp, 0, 0);
    //(*env)->ReleaseByteArrayElements(env, data_, data, 0);//????
    return result;
}

调试

来自本机代码的SO捕获异常的一些代码:

    static uint32_t find_start_code(uint8_t *buf, uint32_t zeros_in_startcode){
    //...
    try {
        if ((info = (buf[zeros_in_startcode] != 1)? 0: 1) == 0) return 0;//your code
    }
    // You can catch std::exception for more generic error handling
    catch (std::exception e){
        throwJavaException (env, e.what());//see method below
    }
    //...

然后一个新的方法:

    void throwJavaException(JNIEnv *env, const char *msg)
    {
     // You can put your own exception here
     jclass c = env->FindClass("java/lang/RuntimeException");
     if (NULL == c)
     {
         //B plan: null pointer ...
         c = env->FindClass("java/lang/NullPointerException");
     }
     env->ThrowNew(c, msg);
    }
}

不要太挂SEGV_ACCERR,你有一个分段错误,SIGSEGV(由程序试图读取或写入非法的内存位置,在你的情况下读取).
来自siginfo.h:

SEGV_MAPERR表示您尝试访问未映射到任何内容的地址. SEGV_ACCERR表示您尝试访问您无权访问的地址.

这可能是有趣的:

问:我注意到有RTMP支持.但是已经合并了一个删除RTMP的补丁.
问:你能告诉我为什么吗？
答:我们不认为RTMP服务于移动广播用例以及HLS,
A:所以我们不希望将有限的资源用于支持它.

请参阅:https://github.com/Kickflip/kickflip-android-sdk/issues/33

我建议你注册一个问题:
https://github.com/Kickflip/kickflip-android-sdk/issues
https://github.com/ButterflyTV/LibRtmp-Client-for-Android/issues