Re: [Qemu-devel] [PATCH] target-i386: fix addr16 prefix

[Richard Henderson <rth@twiddle.net>]

On 03/02/2016 07:04 AM, Paolo Bonzini wrote:
> While ADDSEG will only be false in 16-bit mode for LEA, it can be
> false even in other cases when 16-bit addresses are obtained via
> the 67h prefix in 32-bit mode.  In this case, gen_lea_v_seg forgets
> to add a nonzero FS or GS base if CS/DS/ES/SS are all zero.  This
> case is pretty rare but happens when booting Windows 95/98, and
> this patch fixes it.
> 
> The bug is visible since commit d6a291498, but it was introduced
> together with gen_lea_v_seg and it probably could be reproduced
> with a "addr16 gs movsb" instruction as early as in commit
> ca2f29f555805d07fb0b9ebfbbfc4e3656530977.
> 
> Cc: rth@twiddle.net
> Reported-by: Hervé Poussineau <hpoussin@reactos.org>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  target-i386/translate.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)

Reviewed-by: Richard Henderson <rth@twiddle.net>

It doesn't even seem to be uncommon inside the win98 kernel, once you start
looking for that addr16 gs pattern.

Thanks,


r~