You could always do a subsys and then PC/PR..... ;-) Sent from my iPhone
> On Dec 15, 2016, at 7:40 PM, Charles Mills <charl...@mcn.org> wrote: > > @Peter, thanks. I would be happy enough to run the Key 0 code in supervisor > state. I'm not happy to run the entire C++ application in supervisor state > (or Key 0). Do you think I am off-base? > > And getting back from supervisor state has the same problem as getting back > from key 0: requires an SVC (or an LPSW). > >> he could not switch back to his "original key". But to accomplish that in > general would require the system to keep a chain of keys > > I was thinking not of an entire "undo" chain like a Windows application but > just the ability to get back to my "NZERO" key -- the key in the TCB. If I > had a magic wand then MODESET would leave on up to three bits on exit: the > current key, key 9, and the TCB key (typically 8). > > Charles > > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On > Behalf Of Peter Relson > Sent: Thursday, December 15, 2016 4:21 PM > To: IBM-MAIN@LISTSERV.UA.EDU > Subject: Re: Question on SPKA and Control Register 3 > >> I think I mentioned that I believe in "least privilege." I don't want >> to > run >> an entire LE/C++ started task in supervisor state. > > When "belief" gets into the way of "function", it could be time to > re-examine. Perhaps you should look for a way that does not require you to > be doing key 0 stuff (or conversely does not require you to intermix > changing between key 0 and key 8 while in problem state) > > The prevailing opinion is that avoiding running in key 0 when you can is a > good thing. > But there is very little concern about running in supervisor state when you > don't need to (if it makes life easier) > > If you want efficiency for your case, then you must use supervisor state. > >> After it showed up on a customer's STROBE report, we switched over to >> using LPSW instead... > > If you're unlucky enough to hit the edge case, you will lose the PER bit by > doing so. There might be other things that could similarly be lost. > System services are provided for a reason. You bypass them at the customer's > risk. > >> Principle of astonishment > The only thing at all surprising should be, as Charles found, that he could > not switch back to his "original key". But to accomplish that in general > would require the system to keep a chain of keys so that you could backtrack > step by step. We would never do that when the user has a simple alternative > -- supervisor state. "Least privilege" is a nice guideline, but it's not a > rule, particularly when you care about performance. If you're interested > enough to run in key 0, running in supervisor state is a small step, not > even a leap. > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
