linux-kernel - Re: [PATCHSET 00/13] tracing/uprobes: Add support for more fetch methods (v6)

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Message-ID: <8761s4wprj.fsf@sejong.aot.lge.com>
Date:	Thu, 07 Nov 2013 18:00:00 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Namhyung Kim <namhyung.kim@....com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Hyeoncheol Lee <cheol.lee@....com>,
	Hemant Kumar <hkshaw@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	"zhangwei\(Jovi\)" <jovi.zhangwei@...wei.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Subject: Re: [PATCHSET 00/13] tracing/uprobes: Add support for more fetch methods (v6)

On Wed, 6 Nov 2013 19:24:08 +0100, Oleg Nesterov wrote:
> Forgot to mention,
>
> On 11/06, Oleg Nesterov wrote:
>>
>> I meant,
>>
>> 		saved_ip = instruction_pointer(regs);
>>
>> 		// pass the "ip" which was used to calculate
>> 		// the @addr argument to fetch_*() methods
>>
>> 		temp_ip = is_ret_probe(tu) ? func : saved_ip;
>> 		temp_ip -= tu->offset;
>> 		instruction_pointer_set(temp_ip);
>>
>> 		store_trace_args(...);
>
> Note that instruction_pointer_set() is not really nice in any case,
> this can obviously confuse FETCH_MTD_reg("ip").

Yes.

>
> But lets ignore this. The solution is simple, we can pass/use this
> info via current->utask. We can either add the new member, or add
> a union. Or simply reuse xol_vaddr. Doesn't matter.

Okay, I'll take a look.

>
> So the only question is should we rely on instruction_pointer/func
> to translate the address or we should do something else (say, vma).
>
> So far I like this approach.

Me too. :)

So, I'll wait for more feedbacks from others and then send a new
version.  Actually I don't have much to do this these days - probably
until next week (there'll be the KLF).  Please forgive my brevity in
replies.

I'll be back with a new patchset then. :)

Thanks,
Namhyung
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