linux-kernel - Re: help needed with EXPORT

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Date:	Mon, 23 Aug 2010 10:44:08 +0530
From:	Aijaz Baig <aijazbaig1@...il.com>
To:	netfilter-devel@...r.kernel.org, jengelh@...ozas.de
Cc:	linux-kernel@...r.kernel.org
Subject: Re: help needed with EXPORT_SYMBOL

Hello,

Yeah I do understand that part, but there has to be a way to do what I
am trying to do here isn't it?

And can anyone tell me can kallsyms_lookup() be used in such a
situation? If yes than how do I use it?

Regards,
Aijaz 

On Sat, Aug 21, 2010 at 2:53 PM, Jan  Engelhardt <jengelh@...ozas.de>
wrote:
On Saturday 2010-08-21 08:57, Aijaz Baig wrote:
        
>So why is it that when my netfilter module is exporting something to
>the kernel and im tryin to use it from within a core kernel file, the
>compiler flags a 'undefined reference to' error?
        
There, you answered yourself. Exports only go one way. And that is
core -> module -> module.

On Sat, 2010-08-21 at 12:27 +0530, Aijaz Baig wrote:
> Hello,
> 
> Ive been trying to EXPORT a SYMBOL from a netfilter module (actually a
> hook) to the KERNEL. Various modules seem to export various symbols to
> the kernel (or so it seems), an example being x_tables which exports a
> whole lot of functions like xt_register_target and so on and all other
> netfilter modules which use these functions dont seem to have any
> problems.
> 
> So why is it that when my netfilter module is exporting something to the
> kernel and im tryin to use it from within a core kernel file, the
> compiler flags a 'undefined reference to' error?
> 
> I googled and came to the conclusion from the kernelnewbies mailing list
> that using kallsyms_lookup() seems to be the answer or is it?
> So, if I do intend to use kallsyms_lookup how do I use it? There aren't
> so many instances of it being used it seems.
>  
> Ive seen it being used in dev/core.c like so:
> symname = kallsyms_lookup((unsigned long)sym, &symsize,&offset,&modname,
> namebuf);
> 
> I am basically trying to call a function that MY module EXPORTs inside
> one of the core linux routines. This would also mean that my netfilter
> module must be compiled (and linked also maybe?..not so sound with link
> time stuff) before the address becomes visible so that kallsyms_lookup
> can find it. So do I really shd be using it and if so, how?
> 
> Any input is appreciated.
> 
> Regards,
> Aijaz Baig.
> 
> 



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