Re: [PATCH v9 17/29] x86/insn-eval: Indicate a 32-bit displacement if ModRM.mod is 0 and ModRM.rm is 101b

[Ricardo Neri]

On Fri, Oct 20, 2017 at 05:44:48PM +0200, Borislav Petkov wrote:
> On Tue, Oct 03, 2017 at 08:54:20PM -0700, Ricardo Neri wrote:
> > Section 2.2.1.3 of the Intel 64 and IA-32 Architectures Software
> > Developer's Manual volume 2A states that when ModRM.mod is zero and
> > ModRM.rm is 101b, a 32-bit displacement follows the ModRM byte. This means
> > that none of the registers are used in the computation of the effective
> > address. A return value of -EDOM indicates callers that they should not
> > use the value of registers when computing the effective address for the
> > instruction.
> > 
> > In long mode, the effective address is given by the 32-bit displacement
> > plus the location of the next instruction. In protected mode, only the
> > displacement is used.
> > 
> > The instruction decoder takes care of obtaining the displacement.
> > 
> > Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> > Cc: Adam Buchbinder <adam.buchbinder@xxxxxxxxx>
> > Cc: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> > Cc: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
> > Cc: Qiaowei Ren <qiaowei.ren@xxxxxxxxx>
> > Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> > Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> > Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> > Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> > Cc: Thomas Garnier <thgarnie@xxxxxxxxxx>
> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> > Cc: Borislav Petkov <bp@xxxxxxx>
> > Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> > Cc: Ravi V. Shankar <ravi.v.shankar@xxxxxxxxx>
> > Cc: x86@xxxxxxxxxx
> > Signed-off-by: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx>
> > ---
> >  arch/x86/lib/insn-eval.c | 25 ++++++++++++++++++++++---
> >  1 file changed, 22 insertions(+), 3 deletions(-)
> 
> Reviewed-by: Borislav Petkov <bp@xxxxxxx>

Thank you!

BR,
Ricardo