Saving Your Caller's Registers - Not Your Father's Save Area

Project and Program: Application Architecture Development and Integration, LE and Programming Languages

Tags: Proceedings , 2018 , SHARE St. Louis 2018

This session is intended for z/OS assembler programmers, whether novice or experienced. It is also useful to anyone who needs to follow calling chains in a dump.
The standard 18-word, 72-byte save area has been used for over 45 years. It is still the most commonly used save area format. With the introduction of z/Architecture it is no longer adequate for all purposes. Some programs must save the 64-bit registers and/or the Access Registers.
New save area formats are documented in the z/OS MVS Assembler Services Guide. The Linkage Conventions chapter of the book was extensively revised for z/OS 1.12, but the usage of these save areas is still not well understood.
This session will start with a brief review of the 72-byte standard save area, then cover the newer save area formats, identified as F1SA, F4SA, F5SA, F6SA, F7SA and F8SA. The presenter will cover the purpose of each of these save areas and how they are used. The proper method of marking each save area with FxSA will be emphasized.
Proper usage of the use of BAKR to save your caller's registers on the Linkage Stack will also be covered.-Thomas C. Marchant-Compuware Corporation

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