linux-kernel - Re: Re: [PATCH RFC 2/6] arm64: Kprobes with single stepping support

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Date:	Thu, 14 Nov 2013 01:05:23 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Sandeepa Prabhu <sandeepa.prabhu@...aro.org>,
	Will Deacon <will.deacon@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"patches@...aro.org" <patches@...aro.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"steve.capper@...aro.org" <steve.capper@...aro.org>,
	"nico@...aro.org" <nico@...aro.org>,
	"srikar@...ux.vnet.ibm.com" <srikar@...ux.vnet.ibm.com>,
	"dsaxena@...aro.org" <dsaxena@...aro.org>,
	"Vijaya.Kumar@...iumnetworks.com" <Vijaya.Kumar@...iumnetworks.com>,
	Jiang Liu <liuj97@...il.com>,
	"yrl.pp-manager.tt@...achi.com" <yrl.pp-manager.tt@...achi.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: Re: [PATCH RFC 2/6] arm64: Kprobes with single stepping support

(2013/11/13 1:59), Steven Rostedt wrote:
> On Tue, 12 Nov 2013 16:25:26 +0530
> Sandeepa Prabhu <sandeepa.prabhu@...aro.org> wrote:
> 
> 
>>>
>>> BTW, I'm currently trying a general housecleaning of __kprobes
>>> annotations. It may also have impact on your patch.
>>> https://lkml.org/lkml/2013/11/8/187
>> Hmm, we can help testing your patchset on arm64 platforms. Also have
>> many doubts on the changes you are working [blacklisting probes etc]
>>
>> Basically I had tried placing kprobe on memcpy() and the model hung
>> (insmod never returned back!). Fast-model I have does not have option
>> of any debug so no clue what happened!.
>> memcpy() is low-level call being used internally within kprobes, so
>> probably we cannot handle probe on that routine, but then how to make
>> sure all such API are rejected by kprobe sub-system ?
> 
> Working on ports of ftrace, I found that many of the functions in lib/
> are used by several locations that just can't be traced, due to how
> low level they are. I just simply blacklisted the entire lib/
> directory (See the top of lib/Makefile)
> 
> I wonder if there's an easy way to blacklist entire directories from
> being used by kprobes too. Or at least do it by a file per file basis.

Hm, perhaps we can do some magic in post-build script as kallsyms does.
1) make an object file
2) extract symbols from the file
3) put the symbols into data section as a list of strings
4) analyze the list at boot (init) time by using kallsyms
how about this? :)

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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