linux-kernel - Re: [patch 4/4] Markers Support for Proprierary Modules

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Date:	Thu, 20 Mar 2008 23:05:40 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	"Frank Ch. Eigler" <fche@...hat.com>
Cc:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	Jon Masters <jcm@...masters.org>, Jon Masters <jcm@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Christoph Hellwig <hch@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [patch 4/4] Markers Support for Proprierary Modules

* Frank Ch. Eigler <fche@...hat.com> wrote:

> Ingo Molnar <mingo@...e.hu> writes:
> 
> >> There seems to be good arguments for markers to support proprierary 
> >> modules. So I am throwing this one-liner in and let's see how people 
> >> react. [...]
> >
> > ugh, this is unbelievably stupid move technically - so a very strong 
> > NACK. Allowing marker use in unfixable modules (today it's placing 
> > markers into unfixable modules, 
> 
> As the thread suggested, this can benefit us more than it benefits
> them, because it may let us see more into the blobs.
> 
> > tomorrow it's marker use by such modules) has only one clear and 
> > predictable effect: it turns marker calls into essential ABIs [...]
> 
> The marker_probe_*register calls are already EXPORT_SYMBOL_GPL'd, so 
> that covers your "tomorrow" case.  NACK that all you like when/if 
> someone proposes changing that.

i very much know that they are exported that way. It's the concept i'm 
against - dont we have 9 million lines of proper kernel source code to 
worry about? Why are we even arguing about this? Binary modules should 
be as isolated as possible - it's a totally untrusted entity and history 
has shown it again and again that the less infrastructure coupling we 
have to them, the better.

> > [if the proprietary modules attach to kernel markers ...] then all 
> > the pressure is on those who _can_ fix their code - meaning the 
> > kernel subsystem maintainers that use [you mean: define] markers.
> 
> (In a way, it would be a nice problem to have.  At this moment, there 
> are still no markers actually committed within -mm nor -linus.)

... which makes it doubly problematic to expose them to binary-only 
modules in any way, shape or form. Really, once _any_ kernel facility is 
used by such a module, it's pain for us to change it from that point on. 
Once markers are a 10 year concept that nobody in their right mind would 
want to change, sure, we dont _care_ about whether it's export or not, 
and basic courtesy might say that it's OK to do it. But to proactively 
export any aspect of a half-done piece of infrastructure is crazy.

	Ingo
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