The system provides the linkage stack where a target program can
save the calling program's access registers
(ARs) and general
purpose registers
(GPRs). Use of the linkage stack has the following
advantages:
- The linkage stack saves both ARs and 64-bit GPRs, whereas many
forms of the caller-provided save area save only GPRs.
- The system provides the linkage stack for use by all programs.
The stack eliminates the need for the AR mode calling program to
obtain storage for a save area and then pass the address to its target
program.
- The save areas are located in one place, rather than chained throughout
the user's address space.
- User programs cannot accidentally make changes to the linkage
stack.