记一次 .NET某工业视觉软件崩溃分析

一：背景

1. 讲故事

前两天给训练营里的一位学员分析了一个dump，学员因为弄了一整天也没找到祸根，被我一下子弄出来了，极度想看看我是怎么分析的？由于在微信上不能一言两语表尽，干脆写一篇文章出来详细的讲讲吧，哈哈，训练营里的学员得有求必应哈。。。话不多说，我们一起探索下这个程序的崩溃之路吧。

二：WinDbg分析

1. 为什么会崩溃

这个比较简单，因为默认会自动定位到崩溃的线程，使用 .ecxr 切到崩溃前的上下文即可，然后使用 k 观察崩溃点，参考如下：



0:044> .ecxr

rax=0000000000000000 rbx=00000217a6c78f90 rcx=0000000000000000

rdx=0000000000000000 rsi=000000242c46fdd0 rdi=00000217ff1594a0

rip=00007ffdb35eb699 rsp=000000242c46fb40 rbp=000000242c46fc70

 r8=00007ffdb35eb699  r9=00000217ea61fc08 r10=00000000e0434352

r11=0000000000000001 r12=00000217a6c78f90 r13=0000000000000000

r14=0000000000000000 r15=0000000000000000

iopl=0         nv up ei pl nz na pe nc

cs=0033  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00000202

KERNELBASE!RaiseException+0x69:

00007ffd`b35eb699 0f1f440000      nop     dword ptr [rax+rax]

0:044> k

  *** Stack trace for last set context - .thread/.cxr resets it

 # Child-SP          RetAddr               Call Site

00 00000024`2c46fb40 00007ffd`51bf8c6f     KERNELBASE!RaiseException+0x69

01 00000024`2c46fc20 00007ffd`51890108     clr!UMThunkStubRareDisableWorker+0x3f

02 00000024`2c46fc50 00007ffc`dc826748     clr!UMThunkStub+0x128

03 00000024`2c46fce0 00007ffc`dc827406     MVCAMSDK_X64+0x6748

04 00000024`2c46fd80 00007ffc`dc9d21eb     MVCAMSDK_X64!CameraGrabber_GetCameraDevInfo+0xb96

05 00000024`2c46fe50 00007ffc`dc9d227f     MVCAMSDK_X64!CameraGigeEnumerateDevice+0x167f2b

06 00000024`2c46fe80 00007ffd`b5a07374     MVCAMSDK_X64!CameraGigeEnumerateDevice+0x167fbf

07 00000024`2c46feb0 00007ffd`b5ebcc91     kernel32!BaseThreadInitThunk+0x14

08 00000024`2c46fee0 00000000`00000000     ntdll!RtlUserThreadStart+0x21

从卦中可以看到程序是在clr 的 UMThunkStubRareDisableWorker 函数中故意抛出的异常，接下来观察下该函数代码。



    extern "C" VOID __stdcall UMThunkStubRareDisableWorker(Thread* pThread, UMEntryThunk* pUMEntryThunk, Frame* pFrame)

    {

        if (!CanRunManagedCode())

        {

            pThread->m_fPreemptiveGCDisabled = 0;

            COMPlusThrowBoot(E_PROCESS_SHUTDOWN_REENTRY);

        }

    }

    BOOL CanRunManagedCode(BOOL fCannotRunIsUserError, HINSTANCE hInst)

    {

        if (g_fForbidEnterEE == TRUE)

            return FALSE;

        if ((g_fEEShutDown & ShutDown_Finalize2) && !GCHeap::GetGCHeap()->IsCurrentThreadFinalizer())

            return FALSE;

        if (g_pPreallocatedOutOfMemoryException == NULL)

            return FALSE;

        return TRUE;

    }

从卦中的代码看是因为 CanRunManagedCode() 返回false导致的，到内存中观察这几个变量即可。



0:044> dp clr!g_fForbidEnterEE L1

00007ffd`5201d548  00000000`00000000

0:044> dp clr!g_fEEShutDown L1

00007ffd`520140b0  00000000`00000007

0:044> dp clr!g_pPreallocatedOutOfMemoryException L1

00007ffd`52013e08  00000217`e4f513d8

看到卦中的几个变量大概就知道了，原来当前程序正在等待终结器线程执行完毕的 EEShutDown 状态。

2. 真的处于关闭状态吗

刚才只是通过变量观察，接下来我们观察线程栈来进一步求证，分别切到主线程和终结器线程观察调用栈，参考如下：



0:000> ~0s;k;~2s;k

win32u!NtUserMsgWaitForMultipleObjectsEx+0x14:

00007ffd`b3dfa104 c3              ret

 # Child-SP          RetAddr               Call Site

00 00000024`2773f578 00007ffd`b3f40c8e     win32u!NtUserMsgWaitForMultipleObjectsEx+0x14

...

08 00000024`2773f9c0 00007ffd`518828ff     clr!CLREventBase::WaitEx+0xab

09 00000024`2773fa30 00007ffd`51882842     clr!WaitForEndOfShutdown_OneIteration+0xb3

0a 00000024`2773fac0 00007ffd`5171f703     clr!WaitForEndOfShutdown+0x1a

0b 00000024`2773faf0 00007ffd`518243f9     clr!EEShutDown+0xd3

0c 00000024`2773fb40 00007ffd`51823f34     clr!HandleExitProcessHelper+0x29

0d 00000024`2773fb70 00007ffd`51823e14     clr!_CorExeMainInternal+0xf8

0e 00000024`2773fc00 00007ffd`96d7d6ea     clr!CorExeMain+0x14

0f 00000024`2773fc40 00007ffd`96c3ac42     mscoreei!CorExeMain+0xfa

10 00000024`2773fca0 00007ffd`b5a07374     mscoree!CorExeMain_Exported+0x72

11 00000024`2773fcd0 00007ffd`b5ebcc91     kernel32!BaseThreadInitThunk+0x14

12 00000024`2773fd00 00000000`00000000     ntdll!RtlUserThreadStart+0x21

paddle_inference_c!paddle::CreatePaddlePredictor<paddle::AnalysisConfig,3>+0x180be:

00007ffc`d39a1a9e 488b01          mov     rax,qword ptr [rcx] ds:00000217`89df37b0=00007ffcd7791ff0

 # Child-SP          RetAddr               Call Site

00 00000024`27eff080 00007ffc`d39a1a8f     paddle_inference_c!paddle::CreatePaddlePredictor<paddle::AnalysisConfig,3>+0x180be

01 00000024`27eff0b0 00007ffc`d39a1a8f     paddle_inference_c!paddle::CreatePaddlePredictor<paddle::AnalysisConfig,3>+0x180af

02 00000024`27eff0e0 00007ffc`d39a1a8f     paddle_inference_c!paddle::CreatePaddlePredictor<paddle::AnalysisConfig,3>+0x180af

...

0e 00000024`27eff3b0 00007ffc`f20cbbde     paddle_inference_c!PD_PredictorDestroy+0x39

0f 00000024`27eff3e0 00007ffc`f943796a     0x00007ffc`f20cbbde

10 00000024`27eff4b0 00007ffc`f9437930     Sdcb_PaddleInference!Sdcb.PaddleInference.PaddlePredictor.Dispose+0x1a

11 00000024`27eff4e0 00007ffd`518915e6     Sdcb_PaddleInference!Sdcb.PaddleInference.PaddlePredictor.Finalize+0x10

12 00000024`27eff510 00007ffd`5173b6c6     clr!FastCallFinalizeWorker+0x6

13 00000024`27eff540 00007ffd`5173bd73     clr!FastCallFinalize+0x5a

14 00000024`27eff580 00007ffd`5173bcae     clr!MethodTable::CallFinalizer+0xb7

15 00000024`27eff5c0 00007ffd`5173b8e7     clr!CallFinalizer+0x5e

...

1e 00000024`27effa50 00000000`00000000     ntdll!RtlUserThreadStart+0x21

其实到这里逻辑全部清楚了，用户点击了关闭程序，但此时终结器线程正在执行，所以执行引擎需要等待它执行完，在这期间是禁止除终结器线程之外的任何线程再对托管方法的调用，一旦有就会抛出异常，画个简图如下：

3. call托管方法在哪里

在错误的时间出现了一个对的人，这是一种意难平，接下来把这个对的人给找出来，即 UMThunkStubRareDisableWorker方法的第二个参数pUMEntryThunk，因为这里面的 m_pManagedTarget 即托管方法的入口点，模型如下：



class UMEntryThunk

{

    private:

    // The start of the managed code

    const BYTE* m_pManagedTarget;

    // This is used for profiling.

    PTR_MethodDesc m_pMD;

}

那如何挖呢？观察UMThunkStubRareDisableWorker方法汇编代码即可。

0:044> k

  *** Stack trace for last set context - .thread/.cxr resets it

 # Child-SP          RetAddr               Call Site

00 00000024`2c46fb40 00007ffd`51bf8c6f     KERNELBASE!RaiseException+0x69

01 00000024`2c46fc20 00007ffd`51890108     clr!UMThunkStubRareDisableWorker+0x3f

02 00000024`2c46fc50 00007ffc`dc826748     clr!UMThunkStub+0x128

03 00000024`2c46fce0 00007ffc`dc827406     MVCAMSDK_X64+0x6748

04 00000024`2c46fd80 00007ffc`dc9d21eb     MVCAMSDK_X64!CameraGrabber_GetCameraDevInfo+0xb96

05 00000024`2c46fe50 00007ffc`dc9d227f     MVCAMSDK_X64!CameraGigeEnumerateDevice+0x167f2b

06 00000024`2c46fe80 00007ffd`b5a07374     MVCAMSDK_X64!CameraGigeEnumerateDevice+0x167fbf

07 00000024`2c46feb0 00007ffd`b5ebcc91     kernel32!BaseThreadInitThunk+0x14

08 00000024`2c46fee0 00000000`00000000     ntdll!RtlUserThreadStart+0x21

0:044> uf 00007ffd`51890108

00007ffd`5188ffe0 4154            push    r12

00007ffd`5188ffe2 55              push    rbp

00007ffd`5188ffe3 4883ec78        sub     rsp,78h

00007ffd`5188ffe7 488d6c2420      lea     rbp,[rsp+20h]

00007ffd`5188ffec c6454000        mov     byte ptr [rbp+40h],0

00007ffd`5188fff0 e8abe0ffff      call    clr!GetThread (00007ffd`5188e0a0)

00007ffd`5188fff5 4885c0          test    rax,rax

00007ffd`5188fff8 746f            je      clr!UMThunkStub+0x89 (00007ffd`51890069)  Branch

...

00007ffd`518900f9 4c895548        mov     qword ptr [rbp+48h],r10

00007ffd`518900fd 498bcc          mov     rcx,r12

00007ffd`51890100 498bd2          mov     rdx,r10

00007ffd`51890103 e8288b3600      call    clr!UMThunkStubRareDisableWorker (00007ffd`51bf8c30)

根据x64调用协定，参数是放在 r10 寄存器中，而r10刚好放在 rbp+48h 中，所以挖出这个栈位置即可，简单计算为。



0:044> ? 00000024`2c46fce0-0x8-0x8-0x8-0x78+0x20

Evaluate expression: 155361672304 = 00000024`2c46fc70

0:044> dp 00000024`2c46fc70+0x48 L1

00000024`2c46fcb8  00000217`ff1594a0

0:044> dp 00000217`ff1594a0 L1

00000217`ff1594a0  00007ffc`f2f49380

0:044> !U 00007ffc`f2f49380

Unmanaged code

00007ffc`f2f49380 e98bbd0500      jmp     00007ffc`f2fa5110

00007ffc`f2f49385 5f              pop     rdi

00007ffc`f2f49386 0f              ???

00007ffc`f2f49387 25e8e35194      and     eax,9451E3E8h

00007ffc`f2f4938c 5e              pop     rsi

00007ffc`f2f4938d 5e              pop     rsi

00007ffc`f2f4938e 1124e8          adc     dword ptr [rax+rbp*8],esp

00007ffc`f2f49391 db5194          fist    dword ptr [rcx-6Ch]

00007ffc`f2f49394 5e              pop     rsi

00007ffc`f2f49395 5e              pop     rsi

0:044> !ip2md 00007ffc`f2fa5110

MethodDesc:   00007ffcf33bd9e8

Method Name:  baslerCamera.MVCam.CameraGrabberFrameCallback(IntPtr, IntPtr, baslerCamera.tSdkFrameHead ByRef, IntPtr)

Class:        00007ffcf33c1c98

MethodTable:  00007ffcf33be828

mdToken:      0000000006000067

Module:       00007ffcf2352f60

IsJitted:     yes

CodeAddr:     00007ffcf2fa5110

Transparency: Critical

从 baslerCamera 来看是一个工业相机，接下来赶紧寻找源代码，截图如下：

图中的 m_FrameCallback 是一个delegate函数，并通过 CameraGrabber_SetRGBCallback 方法传给了C++，所以在关闭程序的时候一定要先释放掉这个 calllback 来和C++撇清关系，否则就会有灾难的降临。

三：总结

在我的dump分析之旅中曾遇到过一次相似的生产故障，本篇文章主要还是对训练营里这位朋友的有求必应吧，不过说实话，多分析几个像这样的dump，会极大的提升你的高级调试能力。