linux-kernel - Re: my first post

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Message-ID: <20130717130539.557c4f62@mdontu-l>
Date:	Wed, 17 Jul 2013 13:05:39 +0300
From:	Mihai Donțu <mihai.dontu@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: Re: my first post

On Wed, 17 Jul 2013 14:09:20 +0800 merrysoft@....com wrote:
> I have meeted a problem with linux kernel 2.6.X.X that my user app
> wants to get thread kernel stack frame ponter(FP) from user space by
> system call or /proc system or any other ways except driver. I do not
> want to write a driver,) to finish it. I have endured this problem
> for a long time.
> 
> would anyone please to give me a hint to solve the problem.
> 

(I'm ignoring the questionable practicality of this)

People have gone to great lengths not to reveal sensitive addresses
from ring 0, %rsp/%rbp being subject to this restriction. If you
configure your kernel to expose full /dev/mem (CONFIG_STRICT_DEVMEM=n),
then using the image for your running kernel and with a bit of DWARF
knowledge, I _think_ it's possible to list the current running threads
and their contexts (ie. CPU registers). Otherwise, I don't believe
there's any way you can achieve this, other than exploiting a bug. :-)

-- 
Mihai Donțu
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