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From: Namhyung Kim <namhyung@kernel.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>, Namhyung Kim <namhyung.kim@lge.com>,
        Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
        Hyeoncheol Lee <cheol.lee@lge.com>,
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        LKML <linux-kernel@vger.kernel.org>,
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        "zhangwei\(Jovi\)" <jovi.zhangwei@huawei.com>,
        Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Subject: Re: [PATCHSET 00/13] tracing/uprobes: Add support for more fetch methods (v6)
References: <1383029621-7384-1-git-send-email-namhyung@kernel.org>
	<20131102155458.GA6981@redhat.com> <87ob60366m.fsf@sejong.aot.lge.com>
	<87fvrc35kj.fsf@sejong.aot.lge.com> <20131104155131.GD4440@redhat.com>
Date: Tue, 05 Nov 2013 10:59:02 +0900
In-Reply-To: <20131104155131.GD4440@redhat.com> (Oleg Nesterov's message of
	"Mon, 4 Nov 2013 16:51:31 +0100")
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On Mon, 4 Nov 2013 16:51:31 +0100, Oleg Nesterov wrote:
> On 11/04, Namhyung Kim wrote:
>> On Mon, 04 Nov 2013 17:46:41 +0900, Namhyung Kim wrote:
>> > On Sat, 2 Nov 2013 16:54:58 +0100, Oleg Nesterov wrote:
>> >> - this only allows to read the data from the same binary.
>> >
>> > Right.  This is also an unnecessary restriction.  We should be able to
>> > access data in other binary.
>>
>> Hmm.. I guess this gonna be not simple
>
> Yes ;)
>
> - perhaps it can only be
>> supported for per-process uprobe with known virtual addresses?
>
> "Known" is very limited. Even in the simplest case (like your test-case
> from from 0/13), you simply can't know the address of "int glob" if you
> compile it with "-pie -fPIC".
>
> As for other binaries (say libc) the problem is even worse, and
> randomize_va_space adds even more pain.

Hmm.. right.  We should deal with relative addresses from the base
mapping address of a binary.

>
> But in any case, I strongly believe that it doesn't make any sense to
> rely on tu->inode in get_user_vaddr().

I'll think about it more.

Thanks,
Namhyung