On 01/04/18 14:59, Klaus P. Ohrhallinger wrote: > On 04.01.2018 19:51, Jan Kokemüller wrote: > >> It is possible to emulate a high resolution counter with a thread that >> continuously increments a variable . This is the reason why browser >> vendors are currently disabling the SharedArrayBuffer feature . >> >> : >> https://gist.github.com/ErikAugust/724d4a969fb2c6ae1bbd7b2a9e3d4bb6#gistcomment-2311156 >> : >> https://blog.mozilla.org/security/2018/01/03/mitigations-landing-new-class-timing-attack/ > > I tried the phtread example from  but even with some tweaking is does > not work at all. > > This is a multiprocessor system, with moderate load. > > As far as I understand the matter, it can only work if both threads > share the same cpu cache, otherwise the counter variable is either never > up-to-date, or has to be fetched and stored from/to memory, which is way > too slow for this purpose. > > Any suggestions ? > > --- > > CPU: Intel(R) Xeon(R) CPU E5420 @ 2.50GHz (2500.14-MHz > K8-class CPU) > FreeBSD/SMP: Multiprocessor System Detected: 8 CPUs > FreeBSD/SMP: 2 package(s) x 4 core(s)
Interestingly, the Xeon 5400 series is not listed as vulnerable in the Intel documentation where the 5500 and 5600s are; I checked as I have a bunch of E5440s in service. https://security-center.intel.com/advisory.aspx?intelid=INTEL-SA-00088&languageid=en-fr imb _______________________________________________ firstname.lastname@example.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"