On Fri, 17 Mar 2017 14:32:13 -0500, John McKown wrote: > >> > On Mar 17, 2017, at 9:09 AM, Dyck, Lionel B. (TRA) wrote: >> > >> > It's not the LA that is the problem - it is the conditional branch >> instructions that don't have the common sense not to branch where they >> shouldn't :-) > >Yeah. The hardware designers should have made an "eXecute" bit to go along >with the other "metadata" bits (such as key and change) so that a >attempting to branch to a frame which is not marked "eXecute" would cause >an exception. But even that doesn't help since you could still "wild >branch" into a code sequence. Maybe we should just all go to the IBMi >series. Lots of really advanced ideas in that box. > Some systems (TOPS-10?) have had that and an execute-only bit, used for IP protection. You could branch to it, but not fetch from it. Nor dump it.
You can't store into a REFR program (if REFRPROT) is enabled, but you can still branch to a writeable frame. Some conflict with JIT recompilation. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
