Re: [Xen-devel] x86_emulate(): forgot to generate_exception_if() for 0xff?

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

Why do you think that? Grp4 only defines valid opcodes for reg==000b and
001b. Grp5 defines valid opcodes for all except reg=111b. So the current
code seems correct.

 -- Keir

On 19/12/07 09:34, "Liu, Eric E" <eric.e.liu@xxxxxxxxx> wrote:

> Hi all,
> In arch/x86/x86_emulate.c: x86_emulate():
>    1716     case 0xfe: /* Grp4 */
>    1717         generate_exception_if((m odrm_reg & 7) >= 2, EXC_UD);
>    1718     case 0xff: /* Grp5 */
>    1719         switch ( modrm_reg & 7 )
>    1720         {
>    1721         case 0: /* inc */
>    1722             emulate_1op("inc", dst, _regs.eflags);
>    1723             break;
>    1724         case 1: /* dec */
>    1725             emulate_1op("dec", dst, _regs.eflags);
>    1726             break;
> 
> Here we only check 0xfe for "reg >= 2"? I think we should also check
> 0xff -- we should swap line 1717 and 1718?
> 
> Thanks!
> --Eric (Liu, Feng)
> 
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