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