I recall distinctly the hardware having fetch protection but there being no apparent OS support for it.
Charles Composed on a mobile: please excuse my brevity "Shmuel Metz (Seymour J.)" <[email protected]> wrote: >In ><ofad40972b.2f224bfe-on85257b21.005f5b59-85257b21.00638...@us.ibm.com>, >on 03/01/2013 > at 01:07 PM, Jim Mulder <[email protected]> said: > >>My understanding from folklore is that the REFR attribute predates >>MVS, and its purpose was to designate modules for which a new copy >>of the module could be safely loaded (refreshing) after a storage >>related machine check. > >Correct. > >>So if you are asking why the designers at that time did not choose >>to also use the REFR attribute for write protection purposes, I >>can only speculate. Since that predated address spaces, the only >>choice for write protection would be using storage key 0. I don't >>know whether or not there was any means at that time for >>providing key 0 storage within a region. > >There was, e.g., subpool 252. > >>But to allow the code to be fetched while executing in the >>region's key, key 0 storage would have to be non-fetch protected. > >As I recall, none of the subpools for load modules were fetch >protected. In fact, I don't recall any support for fetch protect in >OS/360, although IBM might have added it for RSS. > >-- > Shmuel (Seymour J.) Metz, SysProg and JOAT > Atid/2 <http://patriot.net/~shmuel> >We don't care. We don't have to care, we're Congress. >(S877: The Shut up and Eat Your spam act of 2003) > >---------------------------------------------------------------------- >For IBM-MAIN subscribe / signoff / archive access instructions, >send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
