linux-kernel - Re: [RFC/PATCH -next 00/21] Address sanitizer for kernel (kasan)

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Message-ID: <CAPAsAGwb2sLmu0o_o-pFP5pXhMs-1sZSJbA3ji=W+JPOZRepgg@mail.gmail.com>
Date:	Sun, 13 Jul 2014 14:39:21 +0400
From:	Andrey Ryabinin <ryabinin.a.a@...il.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Andrey Ryabinin <a.ryabinin@...sung.com>,
	linux-kernel@...r.kernel.org, Dmitry Vyukov <dvyukov@...gle.com>,
	Konstantin Serebryany <kcc@...gle.com>,
	Alexey Preobrazhensky <preobr@...gle.com>,
	Andrey Konovalov <adech.fo@...il.com>,
	Yuri Gribov <tetra2005@...il.com>,
	Konstantin Khlebnikov <koct9i@...il.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Michal Marek <mmarek@...e.cz>,
	Russell King <linux@....linux.org.uk>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kbuild@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	x86@...nel.org, linux-mm@...ck.org
Subject: Re: [RFC/PATCH -next 00/21] Address sanitizer for kernel (kasan) -
 dynamic memory error detector.

2014-07-12 4:59 GMT+04:00 H. Peter Anvin <hpa@...or.com>:
> On 07/09/2014 04:00 AM, Andrey Ryabinin wrote:
>>
>> Address sanitizer dedicates 1/8 of the low memory to the shadow memory and uses direct
>> mapping with a scale and offset to translate a memory address to its corresponding
>> shadow address.
>>
>> Here is function to translate address to corresponding shadow address:
>>
>>      unsigned long kasan_mem_to_shadow(unsigned long addr)
>>      {
>>               return ((addr) >> KASAN_SHADOW_SCALE_SHIFT)
>>                            + kasan_shadow_start - (PAGE_OFFSET >> KASAN_SHADOW_SCALE_SHIFT);
>>      }
>>
>> where KASAN_SHADOW_SCALE_SHIFT = 3.
>>
>
> How does that work when memory is sparsely populated?
>

Sparsemem configurations currently may not work with kasan.
I suppose I will have to move shadow area to vmalloc address space and
make it (shadow) sparse too if needed.

>         -hpa
>
> --
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-- 
Best regards,
Andrey Ryabinin
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