[SeaBIOS] [PATCH v2] x86emu: Correctly handle 0x66 prefix for some instructions

Julian Pidancet julian.pidancet at gmail.com
Sun Apr 1 23:47:42 CEST 2012

On Thu, Mar 15, 2012 at 10:45 PM, Julian Pidancet
<julian.pidancet at gmail.com> wrote:
> On Thu, Mar 15, 2012 at 10:39 PM, Julian Pidancet
> <julian.pidancet at gmail.com> wrote:
>> On Fri, Mar 9, 2012 at 2:08 AM, Guillem Jover <guillem at hadrons.org> wrote:
>>> On Fri, 2012-03-09 at 00:02:55 +0000, Julian Pidancet wrote:
>>>> Some instructions are not emulated correctly by x86emu when they
>>>> are prefixed by the 0x66 opcode.
>>>> I've identified problems in the emulation of these intructions: ret,
>>>> enter, leave, iret and some forms of call.
>>>> Most of the time, the problem is that these instructions should push or
>>>> pop 32-bit values to/from the stack, instead of 16bit, when they are
>>>> prefixed by the 0x66 special opcode.
>>>> The SeaBIOS project aims to produce a complete legacy BIOS
>>>> implementation as well as a VGA option ROM, entirely written in C and
>>>> using the GCC compiler.
>>>> In 16bit code produced by the GCC compiler, the 0x66 prefix is used
>>>> almost everywhere. This patch is necessary to allow the SeaBIOS VGA
>>>> option ROM to function with Xorg when using the vesa driver.
>>>> v2: - Decrement BP instead of EBP in accordance with the Intel Manual
>>>>     - Assign EIP instead of IP when poping the return address from the
>>>>     stack in 32-bit operand size mode in ret_far_IMM, ret_far, and iret
>>>>     - When poping EFLAGS from the stack in iret in 32-bit operand size
>>>>     mode, apply some mask to preserve Read-only flags.
>>>> Signed-off-by: Julian Pidancet <julian.pidancet at gmail.com>
>>> Looks good to me:
>>> Reviewed-by: Guillem Jover <guillem at hadrons.org>
>>> thanks,
>>> guillem
>> Anyone interested in this ? Is there a maintainer for x86emu ? The
>> MAINTAINERS file in xorg-docs doesn't mention anything about it.
> CCed: Adam Jackson
> Adam, you seem to be the maintainer of the xorg vesa driver. I think
> this patch is closely related. Would you mind taking a look at it ?
> Thanks,

Ping ?


More information about the SeaBIOS mailing list