Creating minidump instructions and WOW64

[Andrew Scherkus]

While following the instructions to create a minidump to diagnose a hang [1], the resulting dump contained a bunch of WOW64 crud that I wasn't able to get past (the usual !wow64exts.sw / .effmach x86 didn't seem to work).

So either...

  1) My WinDbg-fu is weak and I'm doing it wrong (wouldn't surprise me, tips/tricks welcome)

  2) The instructions should be updated to use the 32-bit version of WinDbg (which is what I resorted to)

  3) The instructions should be updated to use procdump [2]

  4) ???

I'm liking (3) -- there's some cool stuff in there like the -h flag for creating a dump if the windows message loop hangs for more than 5 seconds (!) and it doesn't require going through the Windows SDK installer wizard thingy.

Any comments / ideas before I do (3)?

Andrew

[1] http://dev.chromium.org/for-testers/bug-reporting-guidelines/hanging-tabs 

[2] http://technet.microsoft.com/en-us/sysinternals/dd996900.aspx

[Alex Pakhunov]

Usual recommendation about #2 is that unless you need to see the ugly guts of Wow64 (64bit code, thunks, etc.) use the 32bit debugger. Otherwise, you have to work on your WinDbg-fu more. :-)

One (random) guess is that .dump stores either x86 or x64 stack only - depending on the current .effmach setting. Therefore you need to make sure that you switch to x86 before taking the dump. 

--
Chromium Developers mailing list: chromi...@chromium.org
View archives, change email options, or unsubscribe:
http://groups.google.com/a/chromium.org/group/chromium-dev

--

Alex.

[Ryan Sleevi]

Looks like Process Explorer is generating 64-bit dumps of 32-bit
processes, which is Not Desired.

Switching the directions to (3) seems like the right approach, if and
until Process Explorer is updated/changed.

[Eric Roman]

You can get the 32-bit callstacks out of the 64 bit dumps with this:

> .effmach x86

> .load wow64exts

> ~*k =@ebp @ebp @ebp

This particular "k" command is an ugly hack, but hey, "it works" :)

I am not sure why WinDBG doesn't support this more directly with their wow64 extensions, sure would have been nice...

Changing the instructions for generating dumps seems fine, I am not opposed to generating 32-bit dumps instead.

The downside of course is if the hang actually is in 64-bit code, then you now won't be able to diagnose it from the dump.

Note that I also have an internal G+ post that talks about about wrangling the 32-bit parts out of a 64 bit dump.

Cheers.