Re: Cygwin bash's built-in test command crashes on Windows 2008 Server 64bit under KVM

[Avi Kivity <avi@redhat.com>]

Jamie Kirkpatrick wrote:
> All
>
> This is my first post to the list but this seems to be the only place
> I can get this problem to be looked at by hopefully the correct
> people: I've bounced it around in #kvm on freenode and we've all
> agreed its a development issue / bug that needs looking at.
>
> Anyway, without further ado: my machine is a Core 2 Due Quad Core
> based box running Debian Lenny and a 2.6.27 kernel as the host OS.  I
> am using KVM-82 right now and track all current releases of the KVM
> code.
>
> The issue I have run into seems to be very specific to the hardware
> setup I have and the fact that I'm running this version of Windows
> under virtualization.  I have been trying for some time to get Git to
> work under this OS and for one reason or another I was trying the
> cygwin based install.  Problems started appearing as soon as I install
> cygwin, and during the installation process even: various post-install
> config scripts crash and I get the usual windows JIT debugger window
> popping up etc.
>
> Upon further investigation I have tracked the problem down to a
> problem with Cygwin bash's builtin "test" implementation ( the []
> syntax in shell scripting ).  I can cause the crash by simply invoking
> this syntax from a command line.  This problem has been noted before
> and has been posted about elsewhere: first on the cygwin list, and
> then after on the Xen list.  Everyone seems to agree that based on
> more extensive testing from other people that this is being caused by
> something in the virtualzation stack.
>
> Two messages of note are:
>
> http://sourceware.org/ml/cygwin/2008-01/msg00582.html
> http://www.nabble.com/Xen-3.2.1---Win-2003-2008-Server-64-bit-guests:-cygwin-bash-builtin-%22test%22-crashes-td19001336.html
>
> I've spent a long time trying to track this down: I've tried various
> versions of KVM and have tried playing around with windows lots as
> well.  No luck.  I'm lost on this but it seems to me that this just
> should not happen and if there is a bug in the way Xen and KVM treat
> things then it needs fixing...hence the post.
>
> If someone wants to try and squash / identify this bug further I'm
> availible as a tester:  I am a c++ developer by day but I don't know
> the KVM code or how you go about debugging it.  If someone can prime
> me in that direction perhaps I could look at it as well.
>
> Anyway, anything I can do to help and I will.
>   

I tried to track this down.  Apparently the guest clobbers gs during the 
exit routine.

Since it happens in the guest, it's a little difficult to track down.  
It can be done using the guest debugger, in this way:

- start bash in the debugger
- stop the program
- add a watchpoint to break when the value of gs:[0x30] changes
- single-step the program until the watchpoint triggers

However, my Windows debugging skills are pretty much nonexistent.  Can 
you guide me through this?  I'm using windbg.

-- 
error compiling committee.c: too many arguments to function