linux-kernel - Re: [RFC] [PATCH 1/2 v2] x86: introduce int3-based instruction patching

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Date:	Thu, 11 Jul 2013 09:10:53 -0700
From:	"H. Peter Anvin" <hpa@...ux.intel.com>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
CC:	Jiri Kosina <jkosina@...e.cz>,
	Steven Rostedt <rostedt@...dmis.org>,
	Jason Baron <jbaron@...hat.com>,
	Borislav Petkov <bpetkov@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: [RFC] [PATCH 1/2 v2] x86: introduce int3-based instruction patching

On 07/11/2013 03:23 AM, Masami Hiramatsu wrote:
>> + *
>> + * The way it is done:
>> + *	- add a int3 trap to the address that will be patched
>> + *	- sync cores
> 
> You don't need this "sync cores". (and your code didn't) :)
> 

I believe you do, lest you get "Frankenstructions".  I believe you don't
need the second one, however.  I should dig up my notes on this.

>> + *	- update all but the first byte of the patched range
>> + *	- sync cores
>> + *	- replalace the first byte (int3) by the first byte of
>> + *	  replacing opcode
>> + *	- sync cores
>> + *


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