On Sun, 19 Mar 2017 13:04:50 +1100 (EST) Bruce Evans <b...@optusnet.com.au> wrote: > On Sun, 19 Mar 2017, Ed Maste wrote: >> Log: >> use INT3 instead of NOP for x86 binary padding >> >> We should never end up executing the inter-function padding, so we >> are better off faulting than silently carrying on to whatever function >> happens to be next. >> >> Note that LLD will soon do this by default (although it currently pads >> with zeros). >> >> Reviewed by: dim, kib >> MFC after: 1 month >> Sponsored by: The FreeBSD Foundation >> Differential Revision: https://reviews.freebsd.org/D10047 > > Is this a pessimization? Instruction prefetch near the end of almost > every function now fetches INT3 instead of NOP. Both have to be > decoded to decoded whether to speculatively execute them. INT3 is > unlikely to be speculatively executed, but it takes extra work to > decide not to do so.
I seem to vaguely remember that ud2 should be used to stop speculative execution (and the instruction fetching and possible cache invalidation because of it). _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
