<snip> If I didn't have to save/restore R15 and R1, then I could totally get away with something very close to standard linkage </snip>
Huh? You can precisely use standard linkage. Standard linkage starts with "save all". It does not require "restore all". If a service (or protocol) does not specifically tell you to preserve registers 15,0,1 then you do not to do so. As Tom Marchant mentioned, not saving all is simply short-sighted, since you might need that information for diagnostics. Using BAKR/PR to save/restore is an easy way to avoid this problem. The other part that goes with Ed Jaffe's astonishment about problem state, is that the ETXR is also entered in TCB key (even if the ATTACH was issued in some other key). If Ed's astonishment results from a recent event, that indicates that he has not previously had much need for doing supervisor state stuff in ETXR's. z/OS (AKA OS/390 AKA MVS) presumably decided not to create a dependency for normal users with respect to how ETXR's work. Is it an IRB? Yes. Must it be an IRB? Not in theory. Maybe in practice now, due to compatibility concerns, it must be. Can you get away with saving nothing and just branching back to the address in reg 14? Today, yes. Maybe forever, yes. But that would be a silly thing to code to. Peter Relson z/OS Core Technology Design ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
