linux-kernel - Re: [PATCH v10 06/17] mm: slub: introduce metadata_access_enable()/metadata_access

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Message-id: <54CBB9C9.3060500@samsung.com>
Date:	Fri, 30 Jan 2015 20:05:13 +0300
From:	Andrey Ryabinin <a.ryabinin@...sung.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, Dmitry Vyukov <dvyukov@...gle.com>,
	Konstantin Serebryany <kcc@...gle.com>,
	Dmitry Chernenkov <dmitryc@...gle.com>,
	Andrey Konovalov <adech.fo@...il.com>,
	Yuri Gribov <tetra2005@...il.com>,
	Konstantin Khlebnikov <koct9i@...il.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Christoph Lameter <cl@...ux.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Dave Hansen <dave.hansen@...el.com>,
	Andi Kleen <andi@...stfloor.org>, x86@...nel.org,
	linux-mm@...ck.org, Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>
Subject: Re: [PATCH v10 06/17] mm: slub: introduce
 metadata_access_enable()/metadata_access_disable()

On 01/30/2015 02:12 AM, Andrew Morton wrote:
> On Thu, 29 Jan 2015 18:11:50 +0300 Andrey Ryabinin <a.ryabinin@...sung.com> wrote:
> 
>> Wrap access to object's metadata in external functions with
>> metadata_access_enable()/metadata_access_disable() function calls.
>>
>> This hooks separates payload accesses from metadata accesses
>> which might be useful for different checkers (e.g. KASan).
>>
>> --- a/mm/slub.c
>> +++ b/mm/slub.c
>> @@ -467,13 +467,23 @@ static int slub_debug;
>>  static char *slub_debug_slabs;
>>  static int disable_higher_order_debug;
>>  
>> +static inline void metadata_access_enable(void)
>> +{
>> +}
>> +
>> +static inline void metadata_access_disable(void)
>> +{
>> +}
> 
> Some code comments here would be useful.  What they do, why they exist,
> etc.  The next patch fills them in with
> kasan_disable_local/kasan_enable_local but that doesn't help the reader
> to understand what's going on.  The fact that
> kasan_disable_local/kasan_enable_local are also undocumented doesn't
> help.
> 

Ok, How about this?

/*
 * This hooks separate payload access from metadata access.
 * Useful for memory checkers that have to know when slub
 * accesses metadata.
 */


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