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

On Tue, Jul 25, 2017 at 4:49 AM, Ard Biesheuvel
[off-list ref] 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