Re: [PATCH 00/11] (v2) Mitigation against unsafe data speculation (CVE-2017-5753)

[John David Anglin <dave dot anglin at bell dot net>]

On 2018-08-02 2:40 PM, Jeff Law wrote:
> It's been eons.   I think there's enough building blocks on the PA to
> mount a spectre v1 attack.  They've got branch prediction with varying
> degress of speculative execution, caches and user accessable cycle timers.
Yes.
> There's varying degrees of out of order execution all the way back in
> the PA7xxx processors (hit-under-miss) to full o-o-o execution in the
> PA8xxx series (including the PA8900 that's in the rp3440).
However, as far as I know, loads and stores are always ordered.
> I suspect that given enough time we could figure out why the test didn't
> indicate spectre v1 vulnerability on your system and twiddle it, but
> given it's a dead processor, I doubt it's worth the effort.
Spectre output looks like this:
dave@mx3210:~/meltdown$ ./spectre
Reading 40 bytes:
Reading at malicious_x = 0xffffef10... Unclear: 0xFE='?' score=999    
(second best: 0xFC score=999)
Reading at malicious_x = 0xffffef11... Unclear: 0xFC='?' score=999    
(second best: 0xFB score=999)
Reading at malicious_x = 0xffffef12... Unclear: 0xFE='?' score=999    
(second best: 0xFC score=999)

I don't think there's a suitable barrier.  The sync instruction seems 
like overkill.

So, I'm going to install attached change after testing is complete.

Dave

--
John David Anglin  dave.anglin@bell.net

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