Jakub Jermar wrote:
> yesterday I tried to mask off the DF flag from the RFLAGS register 
> during the SYSCALL instruction by specifying this bit in the SFMASK MSR 
> register while running HelenOS.
> 
> With QEMU, this didn't work (but it worked in Simics, for instance), so 
> I suspect that there is something wrong with handling RFLAGS.DF during 
> SYSCALL. Anyone wants to have a look?

I have looked into the problem a little more and found out that the
culprit here is probably a missing update of the DF variable in the
helper_syscall() function, in target-i386/helper.c.  See the attached
patch.

The patch fixes the problem for me, but is probably not complete (i.e.
there might be other places that need a similar treatment), but I can't
really tell since I am not a qemu expert.

Jakub