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

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Message-ID: <51DF52D4.20500@hitachi.com>
Date:	Fri, 12 Jul 2013 09:50:28 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Jason Baron <jbaron@...hat.com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Borislav Petkov <bpetkov@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: [RFC] [PATCH 1/2 v2] x86: introduce int3-based instruction patching

(2013/07/11 19:51), Jiri Kosina wrote:
>>> + *	- 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
>>> + *
>>> + * Note: must be called under text_mutex.
>>> + */
>>> +void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler)
>>> +{
>>> +	unsigned char int3 = 0xcc;
>>> +
>>
>> Here, you have to protect this code from others, since bp_* are
>> global.
> 
> Caller is responsible for holding the text_mutex, so text_poke_bp() can't 
> race with itself. And the proper consistency between text_poke_bp() and 
> the notifier is achieved by the memory barriers.

Oops, right. I missed your "Note" line

> 
> So what exact scenario do you have in mind here, please?

No, never mind...


Thank you,

-- 
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com


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