From: Rusty Russell <rusty@rustcorp.com.au>
To: Arjan van de Ven <arjan@infradead.org>
Subject: Re: [PATCH 5/6] module: make modversion_info contain a pointer, not an array.
Date: Thu, 29 Jan 2009 08:59:40 +1030
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Cc: linux-kernel@vger.kernel.org, Shawn Bohrer <shawn.bohrer@gmail.com>,
       Jon Masters <jonathan@jonmasters.org>
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On Thursday 29 January 2009 01:22:31 Arjan van de Ven wrote:
> On Thu, 29 Jan 2009 00:05:52 +1030
> Rusty Russell <rusty@rustcorp.com.au> wrote:
> 
> > 
> > With allmodconfig (minus non-building modules) on 32-bit x86:
> > Total size of modules before: 60009790 bytes
> > Total size of modules after: 55927866 bytes
> > 
> > Saving 7% of module size for CONFIG_MODVERSIONS=y; and these sections
> > are kept resident as well.
> > 
> 
> that reminds me.. can we just simplify MODVERSIONS to be a md5sum (or
> sha1 whatver) of the .config file in the VERMAGIC ?
> it's a lot more reliable in detecting incompatibilities, and a lot
> less space consumed.

Unfortunately people really seem to want the finer granularity that MODVERSIONS (sometimes) provides :(  I've tried killing it off several times, and always failed.

We did discuss changing modversions not to descend more than one level deep into types (ie. MODVERSION(int fn(struct foo *)) would depend on the type of struct foo, but not the type of any struct pointers in struct foo) to reduce the problem where header changes cause type definitions to be exposed or hidden and thus change the modversion.

I asked someone to do some analysis on what effect this would have on signatures in real releases, but never heard back (it was in Austin last year, and there was beer...)

Cheers,
Rusty.


 undefined types


> 
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