linux-kernel - Re: Fast LKM symbol resolution with SysV ELH hash table

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Message-ID: <20091019191016.GA3922@kroah.com>
Date:	Mon, 19 Oct 2009 12:10:16 -0700
From:	Greg KH <greg@...ah.com>
To:	Carmelo Amoroso <carmelo73@...il.com>
Cc:	Alan Jenkins <sourcejedi.lkml@...glemail.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	linux-kbuild <linux-kbuild@...r.kernel.org>
Subject: Re: Fast LKM symbol resolution with SysV ELH hash table

On Mon, Oct 19, 2009 at 05:02:51PM +0200, Carmelo Amoroso wrote:
> 2009/10/19 Greg KH <greg@...ah.com>:
> > On Mon, Oct 19, 2009 at 01:45:20PM +0200, Carmelo Amoroso wrote:
> >> Just a few other notes. The current implementation I did based on SysV
> >> has a drawback that is not backward compatible, so you cannot use old
> >> modules with a kernel with the option enabled due to changes on struct
> >> kernel_symbol.
> >
> > Why would this be a problem? ?Whenever making a kernel config change,
> > you should be able to rebuild everything, as lots of other configuration
> > options are that way.
> >
> 
> This is not always true... there could be cases in which you cannot
> recompile old modules (e.g vendors that provide non GPL modules)

But we do not care at all about that kind of thing, sorry.

> >> Anyway I've just figured out how to change it to remove this limitation.
> >> I need some time to review these patches. ?Further, the newer
> >> implementation based on GNU hash which we are working on right now,
> >> will not require the extra .undef.hash ELF sections because hash
> >> values are already embedded into the GNU hash table, with a reduction
> >> in terms of footprint.
> >
> > Footprint in the memory for the loaded module, or just in the footprint
> > for the module on the disk?
> >
> 
> both

Why would the already-loaded module size increase?

I guess I'll just wait to see the code before worrying about this :)

thanks,

greg k-h
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