linux-kernel - Re: [PATCH] [1/5] CPA: Split static_protections into required_static_prot and advised_static

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Date:	Sat, 9 Feb 2008 18:09:23 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Andi Kleen <andi@...stfloor.org>
cc:	Andi Kleen <ak@...e.de>, mingo@...e.hu,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [1/5] CPA: Split static_protections into required_static_prot
 and advised_static_prot

On Sat, 9 Feb 2008, Andi Kleen wrote:
> > > Note the behaviour for pageattr and thus DEBUG_RODATA / debugging
> > > sitations where you don't care about your TLB this
> > > does not change, this makes only a difference for the initial init_32
> > > direct mapping setup.
> > 
> > Your patches do change the behaviour. The range checking breaks the
> > enforcement of some restrictions for the sake of keeping the large
> > page intact.
> 
> You mean in try_preserve_large_page()?
> 
> No actually they were not completely enforced previously at all, because
> it did only check the restrictions of the first page.

Right, you poked my nose to it. I did not think about it when I coded
it. It is wrong and needs to be fixed, but not by the range check you
introduced.
 
> On the end of my patch series the enforcement is actually stricter
> than it was before, although not 100%.

As far as I can tell it is more relaxed, as it will make overlapping
regions of rodata and rwdata completely rw instead of splitting it up.

Thanks,
	tglx
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