Messages in this thread |  | | Date | Sun, 30 Apr 2017 19:15:27 +0200 | From | Borislav Petkov <> | Subject | Re: [v6 PATCH 06/21] x86/insn-eval: Add utility functions to get segment selector |
| |
On Wed, Apr 26, 2017 at 01:44:43PM -0700, Ricardo Neri wrote: > I regard that the role of this function is to obtain the the segment > selector from either of the prefixes or inferred from the operands. It > is the role of caller to determine if the segment selector should be > ignored.
No, this is wrong. The function is called resolve_seg_selector() and it gives you the segment selector. CS, DS, ES, and SS in 64-bit mode are treated as null segments and your function should return/signal exactly that, i.e, saying that those should be ignored in that case.
> I double-checked the latest version of the Intel Software Development > manual [2], in the table 3-5 in section 3.7.4 mentions that DS is > default segment for all data references, except string destinations. I > tested this code with the UMIP-protected instructions and whenever I use > %edi the default segment is %ds.
Yes, all correct. Except that we're adding a more-or-less generic x86 insn decoder so we should make it so...
> Is this example valid? The documentation of MOVS specifies that it > always moves DS:(E)SI to ES:(E)DI.
... that the decoder should do exactly that:
if (MOVS and rDI) return SEG_ES;
And you're handing in struct insn * so you can easily check which insn you're looking at.
Thanks.
-- Regards/Gruss, Boris.
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --
|  |