linux-kernel - Re: [kernel-abi] symbol versioning vs. out-of-tree modules.

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Date:	Wed, 24 Sep 2008 23:36:17 +0400
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Paweł Sikora <pluto@...k.net>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [kernel-abi] symbol versioning vs. out-of-tree modules.

On Wed, Sep 24, 2008 at 05:07:59PM +0200, Paweł Sikora wrote:
> with out-of-tree kernel modules we (users and linux distributions)
> have a problem - with every frequent kernel release we need
> to rebuild them all due to vermagic and possible abi changes.
> this leads to lot of useless work (bumping rpm specs releases,
> preparing rpm packages and so on).

That's your price for using out-of-tree junk.

> naturally we could workaround the modprobe vermagic errors
> but we currently can't detect the big-bang kernel abi changes.

And never will be able to.

> e.g., some kernel function changes its parameter list while
> the exported function(symbol) name still staying unchanged.
> finally we get a modprobe-big-bang.

*bang*

> in fact, we can't use a c++ symbol name mangling to avoid
> such problems but kernel build system could use a linker script
> to versioning symbols (like glibc/libgcc). during the abi change,
> kernel developers could just bump the symbol version and
> external modules could be refused during loading with
> 'unresolved symbol' error which is imho much better solution
> that an oops.

So kernel developers should waste time thinking if some change will
result in some innumerable junk being broken, resulting in symbol
version bump?

> is it acceptable and possible to introducing such solution?

No. Don't even bother.
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