On 02/08/18 21:19, John David Anglin wrote: > 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. >
It's your call as port maintainers. I've created a PR for each unfixed architecture. Please can you commit the patch against that so that I can track things for back-porting. Thanks, R. > Dave > > > pa-spectre.d > > > Index: config/pa/pa.c > =================================================================== > --- config/pa/pa.c (revision 263228) > +++ config/pa/pa.c (working copy) > @@ -428,6 +428,9 @@ > #undef TARGET_STARTING_FRAME_OFFSET > #define TARGET_STARTING_FRAME_OFFSET pa_starting_frame_offset > > +#undef TARGET_HAVE_SPECULATION_SAFE_VALUE > +#define TARGET_HAVE_SPECULATION_SAFE_VALUE speculation_safe_value_not_needed > + > struct gcc_target targetm = TARGET_INITIALIZER; > > /* Parse the -mfixed-range= option string. */ >
