linux-kernel - Re: [PATCH 4/5] break up slow_virt_to

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Date:	Thu, 11 Apr 2013 19:12:46 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Dave Hansen <dave@...1.net>
Cc:	hpa@...ux.intel.com, linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH 4/5] break up slow_virt_to_phys()

On Thu, Apr 11, 2013 at 09:28:59AM -0700, Dave Hansen wrote:
> It's harsh for the cases where __pa()'s result never gets used
> directly, like for checking against 'high_memory'. If it gets used
> (like in /dev/mem's case) the kernel really is doing something it does
> not intend to do. It's essentially reading or writing garbage.
>
> On the other hand, I guess if we've been letting it do that bad thing
> for years, we might as well continue. We're not causing any _more_
> damage.

Well, if it wasn't an already used interface I'd say we forbid accesses
which are void of sense and issue a WARN_ON but who knows who'll come
screaming if we did that.

> I'm leaning toward making it a WARN_ON() at the moment. :)

Right, well, yeah, people would still be able to shoot themselves in the
foot over /dev/mem but now they'll at least be warned about it. Kernel's
job's done. :)

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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