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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 07.12.16 at 16:38, <andrew.cooper3@xxxxxxxxxx> wrote:
> 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.

And I specifically avoided it as being wrong in the context of the
32-bit test harness. Would pc_rel suit you better than ip_rel?

Jan


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