Re: [RFC PATCH 0/5] powerpc: KASAN for 64-bit Book3E

On Fri, Feb 15, 2019 at 11:04:36AM +1100, Daniel Axtens wrote:

Building on the work of Christophe, Aneesh and Balbir, I've ported
KASAN to the e6500, a 64-bit Book3E processor which doesn't have a
hashed page table. It applies on top of Christophe's series, v5.

It requires some changes to the KASAN core - please let me know if
these are problematic and we see if an alternative approach is
possible.

The KASAN shadow area is mapped into vmemmap space:
0x8000 0400 0000 0000 to 0x8000 0600 0000 0000.
To do this we require that vmemmap be disabled. (This is the default
in the kernel config that QorIQ provides for the machine in their
SDK anyway - they use flat memory.)

Only outline instrumentation is supported and only KASAN_MINIMAL works.
Only the kernel linear mapping (0xc000...) is checked. The vmalloc and
ioremap areas (also in 0x800...) are all mapped to a zero page. As
with the Book3S hash series, this requires overriding the memory <->
shadow mapping.

Also, as with both previous 64-bit series, early instrumentation is not
supported.

KVM, kexec and xmon have not been tested.

Thanks to those who have done the heavy lifting over the past several years:
 - Christophe's 32 bit series: https://lists.ozlabs.org/pipermail/linuxppc-dev/2019-February/185379.html
 - Aneesh's Book3S hash series: https://lwn.net/Articles/655642/
 - Balbir's Book3S radix series: https://patchwork.ozlabs.org/patch/795211/

While useful if you have an Book3E device, this is mostly intended
as a warm-up exercise for reviving Aneesh's series for book3s hash.
In particular, changes to the kasan core are going to be required
for hash and radix as well.

Thanks for following through with this, could you please share details on
how you've been testing this?

I know qemu supports qemu -cpu e6500, but beyond that what does the machine
look like?

Balbir Singh.