Configuring the "Debugging Tools"

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  1. Posts : 1,377

    Configuring the "Debugging Tools"

    For updated WinDBG install and configuration instructions please visit the following link - WinDBG - Install and Configure for BSOD Analysis

    How to Analyse Bugcheck and Process Crash Dumps

    Download the debugger package that matches YOUR machine's Windows version

    In other words, if you're running 32-bit Windows, install the 32-bit version of the "Debugging Tools for Windows", irrespective of whether you intend to debug 32-bit or 64-bit code. Likewise for x64 - download and install the x64 package, and you'll still be able to debug 32-bit crashes. Few home and small business users would be running Itaniums, so don't accidentally download the IA-64 (Itanium) build. Itanium is a vastly different architecture to "x64" (AMD64, also known as EM64T when sold by Intel).
    Override the default install path and install to c:\debuggers instead
    This is entirely optional but you'll be happier, especially if you intend to do a fair amount of dump analysis. Choose the "custom" install option and use c:\debuggers (or d:\debuggers or whatever other drive) as the install path. It makes it easier to work with the tools and removes that pesky "Program Files" space from the path name. The debugger package is a lot more command-line oriented than many apps nowadays.
    Register WinDBG as the default handler for dump files
    Another entirely optional step that makes life easier. By registering WinDBG (the main debugger you'll want to use) as the default handler for common dump file types, you'll be able to double-click on a dump and have it open in WinDBG without having to go through the "File | Open..." menu operation every time. This registration needs to be performed from an elevated CMD prompt (run CMD as administrator):
    C:\>cd debuggers
    C:\debuggers>windbg.exe -IA
    In response, WinDBG should pop up a dialog box that says this:
    WinDbg:6.11.0001.402 AMD64
    WinDbg successfully registered file assocations for .DMP, .HDMP, .MDMP, .KDMP and .WEW.
    Set your symbol path
    This is NOT optional. In fact, getting it wrong is the #1 reason for frustration when learning to debug. There are several ways to get it right, and this is possibly the simplest:

    a) Start WinDBG
    b) WITHOUT opening any dump files, click File, "Symbol File Path..."
    c) Set the path to be the following:It can be any valid local path, c:\Symbols or e:\MySymbols or whatever, but the SRV and http portions must be exactly as above. Don't move the local path around too much though because the idea is to build up a local cache of symbols that minimises your waiting time while symbols are being downloaded from MS. That local cache can grow quite large over time, if you do a lot of dump analysis, and the debugger will be subsequently quicker to open new dumps because of the larger symbols cache.

    d) Exit WinDBG. It should ask you whether you wish to save workspace settings. "Yes" is almost always the appropriate answer to WinDBG's workspace prompts. From now onwards the symbol path should already be set whenever you start WinDBG.

    With the correct symbol path configured, whenever the debugger encounters a new binary for which it must find symbols, it will:

    1. Check first in C:\SymCache. If a matching symbol is not found...
    2. Check whether the symbol is available from the MS symbol server. If it is, copy it down to C:\SymCache so it can be cached for faster future operation.

    In practice, the MS symbol server will contain symbols for MS binaries (exe, dll, sys), but not for 3rd-party modules. As a consequence, the lack of symbols availability can be interpreted as a hint that this may not be a Microsoft component.

    Opening and analysing dumps
    Once you've done the preparatory steps above, you can double-click (if registered) or "File | Open Crash Dump..." in WinDBG to get it to open and analyse a minidump or any other memory dump, including crashes from user-mode processes. If you want to re-invoke its automated analysis engine, use the !ANALYZE -V command. The "v" switch stands for "verbose" - it produces additional detail which may be useful.

    The debugger will attempt to find the relevant symbols and then produce a diagnosis, to the best of its automated abilities. Look for a line like this in the output:

    Probably caused by : win32k.sys ( win32k!FindTimer+57 )

    If the automated diagnosis references a non-default driver, the first task is to update the driver. If that doesn't help and subsequent dumps all still point at the same driver again, try removing it as a test.

    In this case, win32k.sys is pinpointed and that is a very important driver which is a part of Windows itself.

    When the "probably caused by" verdict points at an OS component, the situation is more complex and minidump analysis is not always sufficient to find the true cause of the crash.

    More (Optional) Debugger Trickery For The Interested
    A minidump contains 3 main items of information:

    1) The stack of the thread which directly caused the crash. This can be viewed with the various 'k' (stack unwind) commands:
    1: kd> kL
    Child-SP RetAddr Call Site
    fffffa60`09cd0528 fffff800`01cb60ee nt!KeBugCheckEx
    fffffa60`09cd0530 fffff800`01cb5abc nt!KiBugCheckDispatch+0x6e
    fffffa60`09cd0670 fffff800`01cc96bd nt!KiSystemServiceHandler+0x7c
    fffffa60`09cd06b0 fffff800`01cd0cff nt!RtlpExecuteHandlerForException+0xd
    fffffa60`09cd06e0 fffff800`01c8dd83 nt!RtlDispatchException+0x22f
    fffffa60`09cd0dd0 fffff800`01cb61a9 nt!KiDispatchException+0xc3
    fffffa60`09cd13d0 fffff800`01cb4d8d nt!KiExceptionDispatch+0xa9
    fffffa60`09cd15b0 fffff960`0011c947 nt!KiGeneralProtectionFault+0xcd
    fffffa60`09cd1740 fffff960`00121e2d win32k!FindTimer+0x57
    fffffa60`09cd1790 fffff800`01cb5df3 win32k!NtUserKillTimer+0x5d
    fffffa60`09cd17d0 00000000`7790c24a nt!KiSystemServiceCopyEnd+0x13
    A "stack" is a thread-specific region of memory used for several purposes such as the temporary storage of data, the passing of data between different functions, and for many other more specialised needs such as quick string reversal ("debugger" reversed becomes "reggubed"). The "stack unwind" shown above reveals that the nt!KeBugCheckEx (blue screen) function was called by nt!KiBugCheckDispatch, which was in turn called by nt!KiSystemServiceHandler, and so on downwards. Therefore, function displayed by the debugger at the top of the stack is the latest in terms of chronological order. The specific stack at the time of a crash can be likened to a crash "signature" which can be used to search for other instances of similar problems, and hence potential solutions.

    2) The processor register context of that thread:
    1: kd> r
    rax=fffffa6009cd0630 rbx=fffffa6009cd17d0 rcx=000000000000003b
    rdx=00000000c0000005 rsi=fffff80001cb5df3 rdi=fffff80001e64df4
    rip=fffff80001cb6350 rsp=fffffa6009cd0528 rbp=fffffa6009cd1508
    r8=fffff9600011c947 r9=fffffa6009cd0ee0 r10=0000000000000000
    r11=0000000000000001 r12=fffffa6009cc4000 r13=fffffa6009cd4000
    r14=fffff80001c61000 r15=fffff80001daf4ec
    iopl=0 nv up ei ng nz na po nc
    cs=0010 ss=0018 ds=002b es=002b fs=0053 gs=002b efl=00000286
    fffff800`01cb6350 48894c2408 mov qword ptr [rsp+8],rcx ss:0018:fffffa60`09cd0530=000000000000003b
    Registers can be thought of as the fastest memory available to the processor. IA-32 (x86) and AMD64 (x64) both provide "general purpose" and specialised registers, and AMD64 is an extension of the simpler IA-32 architecture. Note that "registers" are not in any direct way related to the "registry", despite the name similarity.

    In the example above, the 64-bit Instruction Pointer register (RIP) which contains the address of the next instruction to execute was in nt!KeBugCheckEx at the time of the crash, which is not surprising given that's the "bluescreen" function. The actual problem function which led to the crash is several frames lower in the stack - also highlighted in red.

    3) A list of loaded modules at the time of the crash. The 'lm' (list modules) command can list these:
    1: kd> lm
    start end module name
    fffff800`01c1b000 fffff800`01c61000 hal (deferred)
    fffff800`01c61000 fffff800`02179000 nt (pdb symbols) c:\symcache\ntkrnlmp.pdb\149C563625CA49CEA2881CEDF5D55CCF2\ntkrnlmp.pdb
    fffff960`00050000 fffff960`00301000 win32k (pdb symbols) c:\symcache\win32k.pdb\97A727330C184A9B9E1BDA0C3293AA142\win32k.pdb
    fffff960`00410000 fffff960`0041a000 TSDDD (deferred)
    fffff960`00620000 fffff960`00631000 cdd (deferred)
    In the partial module listing above, the debugger has only encountered "nt" (NTOSKRNL itself) and win32k.sys code in the stack, which is why it has downloaded symbols (they have a PDB extension) from the MS symbol server for those two binaries, but not for hal.dll, TSDDD.dll, and cdd.dll. Their symbol status is listed as "deferred".
    Even More Debugger Trickery For The Really Interested
    Minidumps can also easily reveal basic information about the Windows version, service pack level, time of the crash, and system uptime:
    1: kd> vertarget
    Windows 7 Kernel Version 7600 MP (4 procs) Free x64
    Product: WinNt, suite: TerminalServer SingleUserTS
    Built by:

    Machine Name:
    Kernel base = 0xfffff800`01c61000 PsLoadedModuleList = 0xfffff800`01e26db0
    Debug session time: Thu Apr 2 07:07:55.076 2009 (GMT+11)
    System Uptime: 0 days 0:02:00.122
    Say you've identified a driver that you believe to be responsible, and now you want to see more particulars about that binary. Use 'lmvm' with the module name:
    1: kd> lmvm tdrpm147
    start end module name
    fffffa60`0140c000 fffffa60`01590000 tdrpm147 (deferred)
    Image path: \SystemRoot\system32\DRIVERS\tdrpm147.sys
    Image name: tdrpm147.sys
    Timestamp: Mon Oct 13 21:14:16 2008 (48F31F78)
    CheckSum: 0018472C
    ImageSize: 00184000
    Translations: 0000.04b0 0000.04e4 0409.04b0 0409.04e4
    To get more info on the processor(s):
    1: kd> !cpuinfo
    CP F/M/S Manufacturer MHz PRCB Signature MSR 8B Signature Features
    1 6,15,11 GenuineIntel 2405 000000b600000000 20193ffe
    Cached Update Signature 000000b600000000
    Initial Update Signature 000000b600000000
    To see the generic description for any given bugcheck code:
    1: kd> !analyze -show D1
    An attempt was made to access a pageable (or completely invalid) address at an
    interrupt request level (IRQL) that is too high. This is usually
    caused by drivers using improper addresses.
    If kernel debugger is available get stack backtrace.
    Arg1: 0000000000000000, memory referenced
    Arg2: 0000000000000000, IRQL
    Arg3: 0000000000000000, value 0 = read operation, 1 = write operation
    Arg4: 0000000000000000, address which referenced memory
    And the most useful command of all - it brings up the debugger's comprehensive help document (debuggers.chm):
    1: kd> .hh

    Full dumps allow for much more meaningful analysis but they're hundreds of MB or even several GB in size, depending on the dump type, and for a 2-minute look at someone's BSoD problem a minidump is perfectly sufficient. If their system is crashing frequently and the dumps all point at the same 3rd-party driver - bingo. Otherwise, if virtually every dump points at a different culprit and they mostly look inscrutable, chances are it's a hardware issue or something which would require more advanced analysis methods.
    Last edited by H2SO4; 28 Sep 2009 at 08:48.
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  2. Posts : 285
    Windows 7 Home Premium x64


    Thank you for sharing this nice tutorial!

    I did not yet installed the Windows debugger, but I have a question.

    In the tutorial, I read this:

    c) Set the path to be the following:
    I don't understand the above, I never have created a path with SRV*, and the directory, and then a http:// link, can you give an example of how to set the path correctly?

    Best regards, and I hope to see a new tutorial from your hand soon ;-)

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  3. Posts : 1,377
    Thread Starter

    zx81 said:

    Thank you for sharing this nice tutorial!

    I did not yet installed the Windows debugger, but I have a question.

    In the tutorial, I read this:

    c) Set the path to be the following:
    I don't understand the above, I never have created a path with SRV*, and the directory, and then a http:// link, can you give an example of how to set the path correctly?

    Best regards, and I hope to see a new tutorial from your hand soon ;-)

    Hello zx81. I recall having used your namesake computer somewhere around 1982/83. Ah, the memories :)

    I understand your natural reluctance to call something that looks like the text string above a "path", but it makes sense to the debugger. The SRV... syntax means that what follows is a multi-part value. In detail:

    SRV*<path_1>*<path_2> tells the debugger to first try find the symbol in <path_1>, then resort to <path_2> if necessary. If it turns out that <path_2> does have the necessary symbol, it will be automatically copied to <path_1> for faster future access.

    These are all valid symbol paths, assuming the C:/D:/E: drives and target folders exist on the machine in question:




    The fact that <path_1> is a "DOS" path while <path_2> is reached via HTTP is incidental. This is also a valid sympath, although it obviously doesn't reach the MS symbol server:


    If appropriate, it is also OK to combine multipath "SRV" entries with traditional syntax (as found in the system PATH environment variable):


    Obviously, the example above would be somewhat slower for general-purpose debugging because it would cause the debugger to look in E:\SomeApp\Symbols every single time, before resorting to the SymCache+HTTP combination.

    A truly convoluted sympath may be something like this:


    In practice, once you get to the point where your debugging needs necessitate sympaths that complex, it's better to set up separate "workspaces" for different types of debugging, but that just confuses the issue for our purposes here.

    I hope that explanation makes more sense. If not, please let me know!
    Last edited by H2SO4; 09 Nov 2009 at 08:11. Reason: Wrapping paths to the next line for readability
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  4. Posts : 285
    Windows 7 Home Premium x64


    Thank you for making the SRV* syntax clear to me, and perhaps others not yet understanding this.

    Very nice tutorial!
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  5. Posts : 3

    Hi H2SO4,

    why my windbg stop at

    Microsoft (R) Windows Debugger Version 6.11.0001.404 X86
    Copyright (c) Microsoft Corporation. All rights reserved.
    Loading Dump File [C:\1.dmp]
    Mini Kernel Dump File: Only registers and stack trace are available
    DbsSplayTreeRangeMap::Add: ignoring zero-sized range at ?ffffffff`83f3ead4?
    Symbol search path is: SRV*c:\temp*
    Executable search path is: 
    Windows 7 Kernel Version 7600 MP (2 procs) Free x86 compatible
    Product: WinNt, suite: TerminalServer SingleUserTS
    Built by: 7600.16385.x86fre.win7_rtm.090713-1255
    Machine Name:
    Kernel base = 0x83e18000 PsLoadedModuleList = 0x83f60810
    Debug session time: Fri Dec 11 05:27:07.971 2009 (GMT+8)
    System Uptime: 0 days 9:30:09.750
    Loading Kernel Symbols
    Loading User Symbols
    Loading unloaded module list
    i wait it for about 2 hours.Crazy
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  6. Posts : 632
    windows 7 x64 Home Premium

    I am having trouble with the third step in this tutorial, "register WinDBG as the default handler for dump files". Whenever I try the "cd debuggers" command, I get the message "The system cannot find the path specified."

    I have tried the custom install outlined in the tutorial above. which didn't work, so I also tried a standard install... to no avail. Anyone have any tips on what steps/commands I might be missing? I'm sure the trouble is with my command prompt skillz, as they are non-existent. Thanks!
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  7. Posts : 71

    Use chdir /d command followed by the folder location to get into the folder where you installed Windbg folder, first.
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  8. Posts : 28,845
    Win 8 Release candidate 8400


    H2SO4 is no longer here.

    RE: path. you could also add the directory to the path statement

    RE: the 2 hour hang. That may be all the info available in that dump

    Good luck and let me know if you need help

    Ken J+
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  9. Posts : 632
    windows 7 x64 Home Premium

    Thanks Geo64 and zigzag! Got it to work!

    For any noobs who follow:
    1. Open a command prompt as an admin, that'll give you:

    2. Enter "chdir /d C:\debuggers"... this will give you a new prompt "C:\debuggers"

    3. Enter "windbg.exe -IA" and Et Voila!

    Thanks again guys!
    Last edited by stevieray; 13 Dec 2009 at 10:36. Reason: fixed error
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  10. Posts : 71

    Great! You're welcome.
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