[PATCH v5 5/6] arm64: add KASAN support

[Catalin Marinas]

On Tue, Aug 11, 2015 at 05:18:18AM +0300, Andrey Ryabinin wrote:
> This patch adds 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 vmalloc area.
> 
> 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.
> 
> 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.
> 
> Signed-off-by: Andrey Ryabinin <ryabinin.a.a at gmail.com>
> Tested-by: Linus Walleij <linus.walleij at linaro.org>

Reviewed-by: Catalin Marinas <catalin.marinas at arm.com>