Re: [Nasm-devel] [nasm:master] disasm: Fix for disassembly of BOUND

[Cyrill G. <gor...@gm...>]

On Wed, Nov 04, 2015 at 10:51:36AM -0800, H. Peter Anvin wrote:
> > 
> > Signed-off-by: Mark Scott <na...@ms...>
> > Signed-off-by: Cyrill Gorcunov <gor...@gm...>
> > 
> 
> This is wrong, though; EVEX is permitted in 32-bit mode just as VEX is.
> 
> The key thing is that bits [7:5] have to be 1 in 32-bit mode.  It is
> unclear what happens if these bits are 110 as that depends on if it is
> decoded using the modr/m decoder or not.  For VEX prefixes we accept
> them as VEX in that case, which may not match the CPU.
> 
> The evex_p0 test seems to have been taken out of thin air; I don't think
> that is a requirement for EVEX.
> 
> So, I believe the logic should in fact be the exactly same logic that we
> have for VEX:
> 
>             if (segsize == 64 || (data[1] & 0xc0) == 0xc0) {

Ah, good point! Thanks for clarification, Peter! I'll fix