linux-kernel - Re: [announce] [patch] KVM paravirtualization for Linux

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Message-ID: <20070105232853.GA20677@elte.hu>
Date:	Sat, 6 Jan 2007 00:28:53 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Zachary Amsden <zach@...are.com>
Cc:	kvm-devel <kvm-devel@...ts.sourceforge.net>,
	linux-kernel@...r.kernel.org, Avi Kivity <avi@...ranet.com>
Subject: Re: [announce] [patch] KVM paravirtualization for Linux


* Zachary Amsden <zach@...are.com> wrote:

> >>What you really want is more like 
> >>EXPORT_SYMBOL_READABLE_GPL(paravirt_ops);
> >>    
> >
> >yep. Not a big issue - what is important is to put the paravirt ops 
> >into the read-only section so that it's somewhat harder for rootkits 
> >to modify. (Also, it needs to be made clear that this is fundamental, 
> >lowlevel system functionality written by people under the GPLv2, so 
> >that if you utilize it beyond its original purpose, using its 
> >internals, you likely create a work derived from the kernel. 
> >Something simple as irq disabling probably doesnt qualify, and that 
> >we exported to modules for a long time, but lots of other details do. 
> >So the existence of paravirt_ops isnt a free-for all.)
> 
> I agree completely.  It would be nice to have a way to make certain 
> kernel structures available, but non-mutable to non-GPL modules.

the thing is, we are not 'making these available to non-GPL modules'. 
The _GPL postfix does not turn the other normal exports from grey into 
white. The _GPL postfix turns exports into almost-black for non-GPL 
modules. The rest is still grey.

in this case, i'd only make local_irq_*() available to modules (of any 
type), not the other paravirt ops. Exporting the whole of paravirt_ops 
was a mistake, and this has to be fixed before 2.6.20. I'll cook up a 
patch.

> >yes - this limit is easily triggered via the KVM/Qemu virtual serial 
> >drivers. You can think of "kvm_paravirt" as "Linux paravirt", it's 
> >just a flag.
> 
> Can't you just test paravirt_enabled() in that case?

yep - i've changed this in my tree.

	Ingo
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