linux-kernel - Re: [PATCH v1 5/8] mm, kasan: Stackdepot implementation. Enable stackdepot for SLAB

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Message-ID: <CAG_fn=VetOrSwqseiRwCFVr-nTTemczMixbbafgEJdqDRB4p7Q@mail.gmail.com>
Date:	Thu, 28 Jan 2016 14:27:44 +0100
From:	Alexander Potapenko <glider@...gle.com>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:	kasan-dev@...glegroups.com, Christoph Lameter <cl@...ux.com>,
	linux-kernel@...r.kernel.org, Dmitriy Vyukov <dvyukov@...gle.com>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>, linux-mm@...ck.org,
	Andrey Konovalov <adech.fo@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>, rostedt@...dmis.org
Subject: Re: [PATCH v1 5/8] mm, kasan: Stackdepot implementation. Enable
 stackdepot for SLAB

On Thu, Jan 28, 2016 at 1:51 PM, Alexander Potapenko <glider@...gle.com> wrote:
>
> On Jan 28, 2016 8:40 AM, "Joonsoo Kim" <iamjoonsoo.kim@....com> wrote:
>>
>> Hello,
>>
>> On Wed, Jan 27, 2016 at 07:25:10PM +0100, Alexander Potapenko wrote:
>> > Stack depot will allow KASAN store allocation/deallocation stack traces
>> > for memory chunks. The stack traces are stored in a hash table and
>> > referenced by handles which reside in the kasan_alloc_meta and
>> > kasan_free_meta structures in the allocated memory chunks.
>>
>> Looks really nice!
>>
>> Could it be more generalized to be used by other feature that need to
>> store stack trace such as tracepoint or page owner?
> Certainly yes, but see below.
>
>> If it could be, there is one more requirement.
>> I understand the fact that entry is never removed from depot makes things
>> very simpler, but, for general usecases, it's better to use reference
>> count
>> and allow to remove. Is it possible?
> For our use case reference counting is not really necessary, and it would
> introduce unwanted contention.
> There are two possible options, each having its advantages and drawbacks: we
> can let the clients store the refcounters directly in their stacks (more
> universal, but harder to use for the clients), or keep the counters in the
> depot but add an API that does not change them (easier for the clients, but
> potentially error-prone).
>
> I'd say it's better to actually find at least one more user for the stack
> depot in order to understand the requirements, and refactor the code after
> that.
>> Thanks.
>>
(resending to linux-kernel@ because the previous mail bounced)


-- 
Alexander Potapenko
Software Engineer

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