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Date: Fri, 20 Oct 2017 11:07:41 -0700
From: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
To: Borislav Petkov <bp@suse.de>
Cc: Ingo Molnar <mingo@redhat.com>, Thomas Gleixner <tglx@linutronix.de>,
        "H. Peter Anvin" <hpa@zytor.com>, Andy Lutomirski <luto@kernel.org>,
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        Dave Hansen <dave.hansen@linux.intel.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Masami Hiramatsu <mhiramat@kernel.org>, Huang Rui <ray.huang@amd.com>,
        Jiri Slaby <jslaby@suse.cz>, Jonathan Corbet <corbet@lwn.net>,
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        Shuah Khan <shuah@kernel.org>, linux-kernel@vger.kernel.org,
        x86@kernel.org, ricardo.neri@intel.com,
        Adam Buchbinder <adam.buchbinder@gmail.com>,
        Colin Ian King <colin.king@canonical.com>,
        Lorenzo Stoakes <lstoakes@gmail.com>,
        Qiaowei Ren <qiaowei.ren@intel.com>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Kees Cook <keescook@chromium.org>,
        Thomas Garnier <thgarnie@google.com>,
        Dmitry Vyukov <dvyukov@google.com>
Subject: Re: [PATCH v9 17/29] x86/insn-eval: Indicate a 32-bit displacement
 if ModRM.mod is 0 and ModRM.rm is 101b
Message-ID: <20171020180741.GC12298@voyager>
References: <1507089272-32733-1-git-send-email-ricardo.neri-calderon@linux.intel.com>
 <1507089272-32733-18-git-send-email-ricardo.neri-calderon@linux.intel.com>
 <20171020154439.yaklbxd3bkhlx32k@pd.tnic>
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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@linux.intel.com>
> > Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
> > Cc: Colin Ian King <colin.king@canonical.com>
> > Cc: Lorenzo Stoakes <lstoakes@gmail.com>
> > Cc: Qiaowei Ren <qiaowei.ren@intel.com>
> > Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> > Cc: Masami Hiramatsu <mhiramat@kernel.org>
> > Cc: Adrian Hunter <adrian.hunter@intel.com>
> > Cc: Kees Cook <keescook@chromium.org>
> > Cc: Thomas Garnier <thgarnie@google.com>
> > Cc: Peter Zijlstra <peterz@infradead.org>
> > Cc: Borislav Petkov <bp@suse.de>
> > Cc: Dmitry Vyukov <dvyukov@google.com>
> > Cc: Ravi V. Shankar <ravi.v.shankar@intel.com>
> > Cc: x86@kernel.org
> > Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
> > ---
> >  arch/x86/lib/insn-eval.c | 25 ++++++++++++++++++++++---
> >  1 file changed, 22 insertions(+), 3 deletions(-)
> 
> Reviewed-by: Borislav Petkov <bp@suse.de>

Thank you!

BR,
Ricardo