linux-kernel - Re: [PATCH 2/2] kgdb,debug_core,kgdbts: End DEBUG_RODATA limitation using kprobe breakpoints

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Message-ID: <4F703AE6.5020809@hitachi.com>
Date:	Mon, 26 Mar 2012 18:46:14 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Jason Wessel <jason.wessel@...driver.com>
Cc:	linux-kernel@...r.kernel.org, kgdb-bugreport@...ts.sourceforge.net,
	tim.bird@...sony.com
Subject: Re: [PATCH 2/2] kgdb,debug_core,kgdbts: End DEBUG_RODATA limitation
 using kprobe breakpoints

(2012/03/23 23:38), Jason Wessel wrote:
> On 03/23/2012 09:08 AM, Masami Hiramatsu wrote:
>> (2012/03/22 20:57), Jason Wessel wrote:
>>> I will use the arch specific provision to override the
>>> kgdb_arch_set_breakpoint() and use the text_poke() directly.
>>
>> Thanks! that's what I meant. You can use __weak attribute.
>>
> 
> I created and tested a patch yesterday which is show below.  I will
> post a new series at some point soon which addresses this problem as
> well as a number of problems found with the kgdb test suite.

Yeah, that's better.

BTW, I'm not sure the policy of kgdb about mutex, but it seems
that you need to hold a text_mutex when you call the text_poke()
since it uses a fixmap page-area for mapping read-only text page
to writable page. So, without locking (at least ensuring no one
using) text_mutex, it seems not be safe. (some other code may be
trying to change the code by using same fixmap pages)

Thank you,

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