[RFC PATCH untested] arm64: kernel: implement fast refcount checking

[Kees Cook]

On Tue, Jul 25, 2017 at 4:49 AM, Ard Biesheuvel
<ard.biesheuvel at linaro.org> wrote:
> Hi all,
>
> I had a stab at porting the fast refcount checks to arm64. It is slightly
> less straight-forward than x86 given that we need to support both LSE and
> LL/SC, and fallback to the latter if running a kernel built with support
> for the former on hardware that does not support it.
>
> It is build tested with and without LSE support, and boots fine on non-LSE
> hardware in both cases.

Ah! Very cool. Hopefully you and Li can compare notes; I think they've
been working on an implementation too.

> Suggestions welcome as to how to test and/or benchmark this,

I'll post a patch for LKDTM that I've been using. It's more
comprehensive than the existing ATOMIC checks (which predated the
refcount-only protection).

-Kees

-- 
Kees Cook
Pixel Security