Re: [PATCH 3/4] x86/insn: Extract more information about instructions

From: "H. Peter Anvin" <hpa@zytor.com>
To: Sasha Levin <sasha.levin@oracle.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: vegard.nossum@oracle.com, penberg@kernel.org,
	jamie.iles@oracle.com, mingo@redhat.com, tglx@linutronix.de,
	x86@kernel.org, linux-kernel@vger.kernel.org,
	linux-mm@vger.kernel.org
Subject: Re: [PATCH 3/4] x86/insn: Extract more information about instructions
Date: Tue, 15 Apr 2014 20:26:32 -0700	[thread overview]
Message-ID: <534DF868.2020901@zytor.com> (raw)
In-Reply-To: <534D4BF3.3020102@oracle.com>

On 04/15/2014 08:10 AM, Sasha Levin wrote:
> 
> Mnemonics don't have 1:1 relationship with opcodes. So, for example,
> if kmemcheck needs to check (and it does) whether a given instruction
> is an "ADD", it would need to compare it to 9 different opcodes.
> 

Excuse me, but on what planet does, for example, it makes sense if a
particular instruction is a "MOV", for example?  The trend in x86
opcodes have varied over the years and at some points it seems to have
been trendy to have very general mnemonics (consider MOV CR, MOV DR) and
at some points quite the opposite (hence MOVD, MOVQ, MOVDQA, MOVDQU,
MOVAPS, MOVUPS, MOVAPD, MOVUPD, VMOVxxx).

So it is not at all clear that this makes any kind of sense whatsoever,
and is more likely just going to be abused.

	-hpa