Re: [Xen-devel] [PATCH] x86emul: defer rIP-relative address calculation

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 07/12/16 14:07, Jan Beulich wrote:
> By putting it after all instruction fetching has been done, we can both
> simplify the existing handling of immediate operands and take care of
> any future instructions allowing rIP-relative operands and getting
> additional bytes fetched in x86_decode_*() (the current cases of extra
> bytes getting fetched there are only for operands without ModR/M bytes,
> or with them only allowing their register forms).
>
> Similarly the new placement of truncate_ea() will take care of any
> future cases of non-standard memory operands (the one existing case -
> opcodes A0...A3 - are fine with and without this, as they fetch an
> ad_bytes sized unsigned address anyway).
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

This is rather clearer to follow.

Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, although...

>
> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
> @@ -1925,6 +1925,7 @@ x86_decode(
>      uint8_t b, d, sib, sib_index, sib_base;
>      unsigned int def_op_bytes, def_ad_bytes, opcode;
>      enum x86_segment override_seg = x86_seg_none;
> +    bool ip_rel = false;

I would name this specifically rip_rel, as that is the term used in all
the manuals.

~Andrew

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