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

From: Vladimir Murzin
Date: Mon Aug 24 2015 - 12:16:57 EST

On 24/08/15 17:00, Andrey Ryabinin wrote:
> 2015-08-24 18:44 GMT+03:00 Vladimir Murzin <vladimir.murzin@xxxxxxx>:
>> 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?


>> 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]
>> Cheers
>> Vladimir

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