Message-ID: <55DB4372.5010406@arm.com>
Date: Mon, 24 Aug 2015 17:16:50 +0100
From: Vladimir Murzin <vladimir.murzin@arm.com>
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To: Andrey Ryabinin <ryabinin.a.a@gmail.com>
CC: Linus Walleij <linus.walleij@linaro.org>,
        Russell King - ARM Linux <linux@arm.linux.org.uk>,
        Arnd Bergmann <arnd@arndb.de>,
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Subject: Re: [PATCH v2 5/5] arm64: add KASan support
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On 24/08/15 17:00, Andrey Ryabinin wrote:
> 2015-08-24 18:44 GMT+03:00 Vladimir Murzin <vladimir.murzin@arm.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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