[RFC PATCH V1 0/8] KASAN ppc64 support

[Andrey Ryabinin]

2015-08-17 12:50 GMT+03:00 Aneesh Kumar K.V <aneesh.kumar at linux.vnet.ibm.com>:
> Because of the above I concluded that we may not be able to do
> inline instrumentation. Now if we are not doing inline instrumentation,
> we can simplify kasan support by not creating a shadow mapping at all
> for vmalloc and vmemmap region. Hence the idea of returning the address
> of a zero page for anything other than kernel linear map region.
>

Yes, mapping zero page needed only for inline instrumentation.
You simply don't need to check shadow for vmalloc/vmemmap.

So, instead of redefining kasan_mem_to_shadow() I'd suggest to
add one more arch hook. Something like:

bool kasan_tracks_vaddr(unsigned long addr)
{
     return REGION_ID(addr) == KERNEL_REGION_ID;
}

And in check_memory_region():
       if (!(kasan_enabled() && kasan_tracks_vaddr(addr)))
               return;