Re: [Qemu-devel] TCG/GCC breakage

[Aurelien Jarno]

On Wed, Mar 11, 2009 at 12:40:20AM -0300, Glauber Costa wrote:
> I'm seeing a strange behaviour here using qemu-system-x86_64
> (kvm not even compiled in) on an i386 host
> 
> I'm suspecting gcc is doing something nasty in here, but I'll open it
> up here to see if any
> of you have any suggestion.
> 
> I get segfaults very early in execution, and after some investigation,
> I figured out that
> ebp register is corrupted. I can't determine where the corruption starts.

Does QEMU segfault, or processes in the guest? How to reproduce that?
Which QEMU version are you using? I am able to run a Debian Etch x86_64 
guest without problem here.

> I then did rm x86-64-softmmu/op_helper.o; make CC=gcc34, so only this
> file get compiled
> by an older gcc, and it worked again.

Which versions of gcc did you tried? I am using gcc 4.3 here.

> So it seems to me gcc may be generating gibberish somewhere in
> helpers, but since
> this code is a bit fragile, it might well be some mistake on our part.
> 
> Ideas on how to attack it ?
> 

You may want to use the -d option to find the offending helper function.

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
address@hidden                 http://www.aurel32.net