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

[Matteo Frigo <athena@fftw.org>]

Avi Kivity <avi@redhat.com> writes:

> More questions:
> - is the bad 'mov gs' instruction reached on AMD?  or is it avoided
> somehow?  What about bare metal?

The instruction is indeed reached on amd, and gs is 0x2b after
the instruction.  I don't know about bare metal.

> - does the attached program fail when compiled and run in cygwin on an
> AMD host?

The program runs as follows:

w2k3-64:/cygdrive/v$ gcc -O gs.c
w2k3-64:/cygdrive/v$ ./a.exe 
gs: 2b
gs:0x30: 7efdb000
test

> - does setjmp()/longjmp() come from the Windows run-time library, or 
> from cygwin?

The setjmp()/longjmp() is in the cygwin library /bin/cygwin1.dll .
bash calls longjmp() at the end of the expr built-in, which causes the
problem reported by the original poster.

I should also mention that, as an experiment, I have replaced the mov
gs,ax instruction with a couple of no-ops in cygwin1.dll, and cygwin
runs fine on Intel with this patch.

Regards,
Matteo Frigo