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

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Date:	Mon, 24 Aug 2015 17:16:50 +0100
From:	Vladimir Murzin <vladimir.murzin@....com>
To:	Andrey Ryabinin <ryabinin.a.a@...il.com>
CC:	Linus Walleij <linus.walleij@...aro.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....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 24/08/15 17:00, Andrey Ryabinin wrote:
> 2015-08-24 18:44 GMT+03:00 Vladimir Murzin <vladimir.murzin@....com>:
>>
>> Another option would be having "sparse" shadow memory based on page
>> extension. I did play with that some time ago based on ideas from
>> original v1 KASan support for x86/arm - it is how 614be38 "irqchip:
>> gic-v3: Fix out of bounds access to cpu_logical_map" was caught.
>> It doesn't require any VA reservations, only some contiguous memory for
>> the page_ext itself, which serves as indirection level for the 0-order
>> shadow pages.
> 
> We won't be able to use inline instrumentation (I could live with that),
> and most importantly, we won't be able to use stack instrumentation.
> GCC needs to know shadow address for inline and/or stack instrumentation
> to generate correct code.

It's definitely a trade-off ;)

Just for my understanding does that stack instrumentation is controlled
via -asan-stack?

Thanks
Vladimir

> 
>> In theory such design can be reused by others 32-bit arches and, I
>> think, nommu too. Additionally, the shadow pages might be movable with
>> help of driver-page migration patch series [1].
>> The cost is obvious - performance drop, although I didn't bother
>> measuring it.
>>
>> [1] https://lwn.net/Articles/650917/
>>
>> Cheers
>> Vladimir
>>
> 

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