[Windbg] Windbg 初階上課筆記

[Windbg] Windbg 初階上課筆記

最近在公司裡上了一堂 Windbg 的入門課,

其實還真是很久沒碰 Windows 平台的 debugging 了,

以前雖然有用過一點 Windbg,不過也差不多忘光光了 =_=…

下面就把上課的筆記記一下,有需要可以回來查 (英文懶得翻中文啦)~

 

Useful tools

  • Process explorer
  • Process dump
  • LiveKD
  • NotMyFault

 

Windbg basic operations

  • Open crash dump with File > Open crash dump
  • Load symbols
  • .symfix C:\symbols: Set local symbol folder
  • .reload: Reload symbols
  • .sympath: Show current symbol path

 

List threads

  • ~: List all threads

 

Switch thread

  • ~0s: Change to thread 0
  • ~1s: Change to thread 1

 

Show stacks

  • ~*k: List all threads’ stacks
  • ~*kv: List all threads’s stacks with 3 function arguments
  • k: List current thread’s stack
  • kv: List current thread’s stack with 3 function arguments
  • kp: List current thread’s stack with all function arguments (need symbol)

 

Show environment

  • lm: List modules
  • lmv: List module versions
  • lmvm: List specific module versions

 

Crash dump automatic analysis

  • !analyze –v: Analyze a crash
  • !analyze –v –hang: Analyze a hang

 

Show exception context

  • Get context address from `kv`
  • .cxr <address> 
    • If there is “???” shown in the result of .cxr, it indicates an invalid address access or memory corruption

 

Disassemble code

  • u: Disassemble code at the address
  • ub: Disassemble code before that address

 

CPU high analysis

  • !runaway 7: Check thread used CPU time and total elapsed time
    • If thread CPU used time occupies a large portion of total execution time, it might indicate a CPU high symptom.

 

Analyze deadlock

  • !analyze –v –hang
    • However, it might not give correct result
  • !locks
    • Show current locks
  • !cs –s –l –o
    • Show critical section owner
  • ub <return address for EnterCriticalSection line>
    • Show the critical section it is going to enter

 

Analyze Stack overflow (recursive)

  • ~*k
    • Shows a lot of same functions in call stack
  • !teb
    • Show stack base and limit
  • dps <stack limit> <stack base>
    • Show stack range content

 

Analyze .NET framework process crash

  • There is “mscorwks” in call stack
  • Show .NET version
    • lmvm mscorwks
  • Load sos extension dll
    • .load C:\Windows\Microsoft.NET\<version>\SOS.dll
    • .unload sos
  • Print .NET exception with sos extension dll
    • !pe

 

Analyze WoW64 process

  • There is “wow64” in call stack
  • Show current machine type
    • .effmach
  • Set machine type to x86
    • .effmach x86
  • !sw can switch between x86 and x64
  • .load wow64exts
    • Then we can see x86 call stacks
  • To see MessageBox parameters
    • du <argument address>

 

Analyze memory leak

  • Turn on gflags by executing Windows Kits > Global Flags > System Registry > Create user mode stack trace database
  • Show current gflag
    • !gflag
  • Show heaps
    • !heap –s
    • !heap –k –h <heap id>

 

Analyze infinite wait

  • Analyze with !analyze
    • !analyze –v –hang
  • Show WaitForMultipleObjects arguments
    • 1st argument = number of handles
    • 2nd argument = handle array
    • dp <2nd argument address>
  • Show each handle
    • !handle <handle address> f

 

Analyze kernel dump

  • List current process
    • !process
  • List all processes
    • !process 0 0
    • !process 0 7: with call stack
  • Get IRP list from output of !process <process address>
  • Show IRP
    • !irp <irp address>
  • Get device object from “Device” in IRP list, then show its info
    • !devobj <device obj address>
  • Get file object from “File” in IRP list, then show its info
    • !fileobj <file obj address>
  • Show thread info
    • !thread
    • !thread <thread address>
  • Change thread
    • .thread <thread address>
  • Show page table entry
    • !pte <address>
  • Check if is running on VM
    • lmvm vmmemctl: for VMware

 

Analyze kernel dump for memory problem

  • Show memory 
    • !vm
  • If NonPagedPool Usage is close to NonPagedPool Max, or if PagedPool Usage is closed to PagedPool Max, there could be memory stress problem.
    • !poolused 2: non-paged memory
    • !poolused 4: paged memory
  • Show running processors and threads
    • !running
    • !running –i –t: include idle processor, and show call stack
  • Show system info
    • !sysinfo cpuinfo
    • !sysinfo 

 

Analyze complete kernel dump

  • There is “Kernel Complete Dump File: Full address space is available” in the output of windbg
  • Change process
    • .process /r /P <process address>
  • Change thread
    • .thread <thread address>

 

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