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Date: Sun, 13 Jul 2014 14:39:21 +0400
Message-ID: <CAPAsAGwb2sLmu0o_o-pFP5pXhMs-1sZSJbA3ji=W+JPOZRepgg@mail.gmail.com>
Subject: Re: [RFC/PATCH -next 00/21] Address sanitizer for kernel (kasan) -
 dynamic memory error detector.
From: Andrey Ryabinin <ryabinin.a.a@gmail.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andrey Ryabinin <a.ryabinin@samsung.com>, linux-kernel@vger.kernel.org,
        Dmitry Vyukov <dvyukov@google.com>,
        Konstantin Serebryany <kcc@google.com>,
        Alexey Preobrazhensky <preobr@google.com>,
        Andrey Konovalov <adech.fo@gmail.com>,
        Yuri Gribov <tetra2005@gmail.com>,
        Konstantin Khlebnikov <koct9i@gmail.com>,
        Sasha Levin <sasha.levin@oracle.com>, Michal Marek <mmarek@suse.cz>,
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2014-07-12 4:59 GMT+04:00 H. Peter Anvin <hpa@zytor.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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