linux-kernel - Re: [PATCH v3 4/8] x86: speed up int3-based patching using direct write

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Message-ID: <5284B5D2.70206@hitachi.com>
Date:	Thu, 14 Nov 2013 20:36:50 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Petr Mladek <pmladek@...e.cz>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Jiri Kosina <jkosina@...e.cz>, linux-kernel@...r.kernel.org,
	x86@...nel.org
Subject: Re: [PATCH v3 4/8] x86: speed up int3-based patching using direct
 write

(2013/11/14 19:41), Petr Mladek wrote:
> @@ -837,7 +882,7 @@ static void recover_iter(struct text_poke_bp_iter *iterator,
>  	}
>  
>  	/* Finally, put back the first byte from the old code */
> -	err = text_poke(addr, old_opcode, sizeof(bp_int3));
> +	err = text_poke_part(addr, old_opcode, sizeof(bp_int3));
>  	/* we can not continue if the interrupt is still there */
>  	BUG_ON(err);
>  }
> @@ -865,7 +910,9 @@ static void recover_iter(struct text_poke_bp_iter *iterator,
>   * It is a bit more paranoid than text_poke_bp because it checks the actual
>   * code before patching. This is a good practice proposed by the ftrace code.
>   *
> - * Note: This function must be called under text_mutex.
> + * Note: This function must be called under text_mutex. Also the caller is
> + * responsible for making the patched code read-write, for example using
> + * set_kernel_text_rw() and set_all_modules_text_rw()

OK, I got the reason why we can do it.
But if so, we should change all existing caller of text_poke_bp() to
call it in this patch, or they must fail at this point.

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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