svn commit: r327876 - in head/sys/arm64: arm64 include

[Andrew Turner]

> On 12 Jan 2018, at 14:37, Warner Losh <imp at bsdimp.com> wrote:
> 
> 
> 
> On Fri, Jan 12, 2018 at 7:15 AM, Andrew Turner <andrew at freebsd.org <mailto:andrew at freebsd.org>> wrote:
> 
> 
>> On 12 Jan 2018, at 14:10, Marcin Wojtas <mw at semihalf.com <mailto:mw at semihalf.com>> wrote:
>> 
>> Hi Andrew,
>> 
>> 
>> 
>> 2018-01-12 15:01 GMT+01:00 Andrew Turner <andrew at freebsd.org <mailto:andrew at freebsd.org>>:
>>> Author: andrew
>>> Date: Fri Jan 12 14:01:38 2018
>>> New Revision: 327876
>>> URL: https://svnweb.freebsd.org/changeset/base/327876 <https://svnweb.freebsd.org/changeset/base/327876>
>>> 
>>> Log:
>>>  Workaround Spectre Variant 2 on arm64.
>>> 
>>>  We need to handle two cases:
>>> 
>>>  1. One process attacking another process.
>>>  2. A process attacking the kernel.
>>> 
>>>  For the first case we clear the branch predictor state on context switch
>>>  between different processes. For the second we do this when taking an
>>>  instruction abort on a non-userspace address.
>>> 
>>>  To clear the branch predictor state a per-CPU function pointer has been
>>>  added. This is set by the new cpu errata code based on if the CPU is
>>>  known to be affected.
>>> 
>>>  On Cortex-A57, A72, A73, and A75 we call into the PSCI firmware as newer
>>>  versions of this will clear the branch predictor state for us.
>>> 
>>>  It has been reported the ThunderX is unaffected, however the ThunderX2 is
>>>  vulnerable. The Qualcomm Falkor core is also affected. As FreeBSD doesn't
>>>  yet run on the ThunderX2 or Falkor no workaround is included for these CPUs.
>> 
>> Regardless ThunderX2 / Falkor work-arounds, do I understand correctly
>> that pure CA72 machines, such as Marvell Armada 7k/8k are immune to
>> Variant 2 now?
> 
> It is my understanding that the A72 will be immune with this patch and an updated Arm Trusted Firmware as documented in [1].
> 
> Andrew
> 
> [1] https://github.com/ARM-software/arm-trusted-firmware/wiki/ARM-Trusted-Firmware-Security-Advisory-TFV-6 <https://github.com/ARM-software/arm-trusted-firmware/wiki/ARM-Trusted-Firmware-Security-Advisory-TFV-6>
> 
> Are you also working on aarch32 mitigation?

No. I think a similar technique could be used, however as aarch32 has instructions to invalidate the branch predictor these can be used directly.

Andrew