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SubjectRe: [PATCH 00/11] KASan for arm
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Hi Abbott,

On 10/11/2017 01:22 AM, Abbott Liu wrote:
> Hi,all:
> These patches add arch specific code for kernel address sanitizer
> (see Documentation/kasan.txt).
>
> 1/8 of kernel addresses reserved for shadow memory. There was no
> big enough hole for this, so virtual addresses for shadow were
> stolen from user space.
>
> At early boot stage the whole shadow region populated with just
> one physical page (kasan_zero_page). Later, this page reused
> as readonly zero shadow for some memory that KASan currently
> don't track (vmalloc).
>
> After mapping the physical memory, pages for shadow memory are
> allocated and mapped.
>
> KASan's stack instrumentation significantly increases stack's
> consumption, so CONFIG_KASAN doubles THREAD_SIZE.
>
> Functions like memset/memmove/memcpy do a lot of memory accesses.
> If bad pointer passed to one of these function it is important
> to catch this. Compiler's instrumentation cannot do this since
> these functions are written in assembly.
>
> KASan replaces memory functions with manually instrumented variants.
> Original functions declared as weak symbols so strong definitions
> in mm/kasan/kasan.c could replace them. Original functions have aliases
> with '__' prefix in name, so we could call non-instrumented variant
> if needed.
>
> Some files built without kasan instrumentation (e.g. mm/slub.c).
> Original mem* function replaced (via #define) with prefixed variants
> to disable memory access checks for such files.
>
> On arm LPAE architecture, the mapping table of KASan shadow memory(if
> PAGE_OFFSET is 0xc0000000, the KASan shadow memory's virtual space is
> 0xb6e000000~0xbf000000) can't be filled in do_translation_fault function,
> because kasan instrumentation maybe cause do_translation_fault function
> accessing KASan shadow memory. The accessing of KASan shadow memory in
> do_translation_fault function maybe cause dead circle. So the mapping table
> of KASan shadow memory need be copyed in pgd_alloc function.
>
>
> Most of the code comes from:
> https://github.com/aryabinin/linux/commit/0b54f17e70ff50a902c4af05bb92716eb95acefe.

Are you planning on picking up these patches and sending a second
version? I would be more than happy to provide test results once you
have something, this is very useful, thank you!
--
Florian

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