linux-kernel - Re: [PATCH v2 5/5] arm64: add KASan support

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Message-ID: <20150825091547.GA21300@arm.com>
Date:	Tue, 25 Aug 2015 10:15:47 +0100
From:	Will Deacon <will.deacon@....com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	David Keitel <dkeitel@...eaurora.org>,
	Alexander Potapenko <glider@...gle.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH v2 5/5] arm64: add KASan support

On Mon, Aug 24, 2015 at 06:47:36PM +0100, Russell King - ARM Linux wrote:
> On Mon, Aug 24, 2015 at 05:15:22PM +0300, Andrey Ryabinin wrote:
> > Yes, ~130Mb (3G/1G split) should work. 512Mb shadow is optional.
> > The only advantage of 512Mb shadow is better handling of user memory
> > accesses bugs
> > (access to user memory without copy_from_user/copy_to_user/strlen_user etc API).
> 
> No need for that to be handed by KASan.  I have patches in linux-next,
> now acked by Will, which prevent the kernel accessing userspace with
> zero memory footprint.  No need for remapping, we have a way to quickly
> turn off access to userspace mapped pages on non-LPAE 32-bit CPUs.
> (LPAE is not supported yet - Catalin will be working on that using the
> hooks I'm providing once he returns.)

Hey, I only acked the "Efficiency cleanups" series so far! The PAN emulation
is still on my list.

Will
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