This problem is complex in theory but simple in (your) practice. Save/restore the lower halves with an STM/LM R14,R12,12(R13) on entry/exit.
Save and restore the upper half of any register you destroy using a save area of your choice. The lower half of an otherwise unused register is good. A fullword in GETMAIN storage is good. AR 0 is good. QED Charles -----Original Message----- From: IBM Mainframe Assembler List [mailto:ASSEMBLER-LIST@LISTSERV.UGA.EDU] On Behalf Of Dave Clark Sent: Monday, January 24, 2022 11:15 AM To: ASSEMBLER-LIST@LISTSERV.UGA.EDU Subject: Re: Saving Caller's 64-bit Regsiters "IBM Mainframe Assembler List" <ASSEMBLER-LIST@LISTSERV.UGA.EDU> wrote on 01/24/2022 02:01:29 PM: > When I'm following save area chains in a dump, starting with R13, I look > at the second word. If it is an address, I know that the save area at that > address is a standard 72-byte save area. If it is F4SA, F5SA, F7SA, or F8SA, > offset X'80' from R13 is the address of the save area, and I know what > format it is. That is all well and good -- when you're looking at a dump. But I'm given to understand that none of that information is helpful when a called program receives control from a 2nd- or 3rd-party caller (i.e., any caller not written on-site) in terms of being able to tell how much storage the caller allocated for the savearea whose address is passed to the called program. Now, if I've got that wrong, then please enlighten me. Thanks. Sincerely, Dave Clark -- int.ext: 91078 direct: (937) 531-6378 home: (937) 751-3300 Winsupply Group Services 3110 Kettering Boulevard Dayton, Ohio 45439 USA (937) 294-5331 **************************************************************************** ***************** This email message and any attachments is for use only by the named addressee(s) and may contain confidential, privileged and/or proprietary information. If you have received this message in error, please immediately notify the sender and delete and destroy the message and all copies. All unauthorized direct or indirect use or disclosure of this message is strictly prohibited. No right to confidentiality or privilege is waived or lost by any error in transmission. **************************************************************************** *****************
