Re: [PATCH v2 00/25] Apple M1 SoC platform bring-up

Hector Martin
2021-02-24T15:57:05Z

On 22/02/2021 00.20, Hector Martin wrote:
> I haven't tested things at EL0 yet, but it looks like the stateful
> instructions known to be usable in EL0 (AMX) already default to trap on
> this platform, so we should be safe there. Everything else looks like it
> probably either shouldn't work in EL0 (I sure hope the address
> translation one doesn't...) or is probably stateless. I'll dig deeper
> and test EL0 in the future, but so far things look OK (for some
> questionable values of OK :) ).

Follow-up: I have EL0 testing scaffolding now, and I found some more
mutable state (an IMP-DEF, pre-standard version of FEAT_AFP, using a
separate status register for the bits), but thankfully it traps at EL0
by default.

And then I found some other mutable IMP-DEF state that does not trap at
EL0. And which is a 0-day CVE in macOS, because it doesn't
save/restore/clear it either, nor does it trap there.

E-mailing security@apple.com...

--
Hector Martin (marcan@marcan.st)
Public Key: https://mrcn.st/pub