Message-id: <53BE8333.6060404@samsung.com>
Date: Thu, 10 Jul 2014 16:12:35 +0400
From: Andrey Ryabinin <a.ryabinin@samsung.com>
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To: Dave Hansen <dave.hansen@intel.com>, linux-kernel@vger.kernel.org
Cc: 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>,
        Russell King <linux@arm.linux.org.uk>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        Christoph Lameter <cl@linux.com>, Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kbuild@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        x86@kernel.org, linux-mm@kvack.org
Subject: Re: [RFC/PATCH RESEND -next 01/21] Add kernel address sanitizer
 infrastructure.
References: <1404905415-9046-1-git-send-email-a.ryabinin@samsung.com>
 <1404905415-9046-2-git-send-email-a.ryabinin@samsung.com>
 <53BDA568.5030607@intel.com>
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On 07/10/14 00:26, Dave Hansen wrote:
> On 07/09/2014 04:29 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 - PAGE_OFFSET) >> KASAN_SHADOW_SCALE_SHIFT)
>>                              + kasan_shadow_start;
>>      }
> 
> How does this interact with vmalloc() addresses or those from a kmap()?
> 

It's used only for lowmem:

static inline bool addr_is_in_mem(unsigned long addr)
{
	return likely(addr >= PAGE_OFFSET && addr < (unsigned long)high_memory);
}


static __always_inline void check_memory_region(unsigned long addr,
						size_t size, bool write)
{

	....
	if (!addr_is_in_mem(addr))
		return;
	// check shadow here

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