Subject: Re: [RFC PATCH V1 0/8] KASAN ppc64 support

From: Benjamin Herrenschmidt <[email-masked]>
Date: Mon, 17 Aug 2015 16:54:52 +1000

On Mon, 2015-08-17 at 12:06 +0530, Aneesh Kumar K.V wrote:
> Hi,
> 
> This patchset implements kernel address sanitizer for ppc64.
> Since ppc64 virtual address range is divided into different regions,
> we can't have one contigous area for the kasan shadow range. Hence
> we don't support the INLINE kasan instrumentation. With Outline
> instrumentation, we override the shadow_to_mem and mem_to_shadow
> callbacks, so that we map only the kernel linear range (ie,
> region with ID 0xc). For region with ID 0xd and 0xf (vmalloc
> and vmemmap ) we return the address of the zero page. This
> works because kasan doesn't track both vmemmap and vmalloc address.
So bear with me, I don't know anything about KASAN, but if you want a
shadow, can't you just add a fixed offset to the address and thus
effectively shadow each region independently while keeping the inline
helpers ?

Cheers,
Ben.

> Aneesh Kumar K.V (8):
>   powerpc/mm: Add virt_to_pfn and use this instead of opencoding
>   kasan: MODULE_VADDR is not available on all archs
>   kasan: Rename kasan_enabled to kasan_report_enabled
>   kasan: Don't use kasan shadow pointer in generic functions
>   kasan: Enable arch to hook into kasan callbacks.
>   kasan: Allow arch to overrride kasan shadow offsets
>   powerpc/mm: kasan: Add kasan support for ppc64
>   powerpc: Disable kasan for kernel/ and mm/ directory
> 
> -aneesh
> 
>  arch/powerpc/include/asm/kasan.h         | 74 
> ++++++++++++++++++++++++++++++++
>  arch/powerpc/include/asm/page.h          |  5 ++-
>  arch/powerpc/include/asm/pgtable-ppc64.h |  1 +
>  arch/powerpc/include/asm/ppc_asm.h       | 10 +++++
>  arch/powerpc/include/asm/string.h        | 13 ++++++
>  arch/powerpc/kernel/Makefile             |  2 +
>  arch/powerpc/kernel/prom_init_check.sh   |  2 +-
>  arch/powerpc/kernel/setup_64.c           |  3 ++
>  arch/powerpc/lib/mem_64.S                |  6 ++-
>  arch/powerpc/lib/memcpy_64.S             |  3 +-
>  arch/powerpc/lib/ppc_ksyms.c             | 10 +++++
>  arch/powerpc/mm/Makefile                 |  4 ++
>  arch/powerpc/mm/kasan_init.c             | 44 +++++++++++++++++++
>  arch/powerpc/mm/slb_low.S                |  4 ++
>  arch/powerpc/platforms/Kconfig.cputype   |  1 +
>  include/linux/kasan.h                    |  3 ++
>  mm/kasan/kasan.c                         |  9 ++++
>  mm/kasan/kasan.h                         | 20 ++++++++-
>  mm/kasan/report.c                        | 19 ++++----
>  19 files changed, 216 insertions(+), 17 deletions(-)
>  create mode 100644 arch/powerpc/include/asm/kasan.h
>  create mode 100644 arch/powerpc/mm/kasan_init.c
>