Sockets API input register information

Before invoking the sockets API, the general purpose registers (GPRs) need to contain the following registers:

Register: Contents
0-1: N/A
2-12: N/A, unless referenced by a macro parameter
13: Pointer to a standard save area in the key of the caller
14-15: N/A

The contents of the access registers (ARs) on entry to the sockets API call are not used.

When control returns to the caller, the access registers (ARs) contain:

Register: Contents
0-1: Used as work registers by the system
2-14: Unchanged
15: Used as a work register by the system

If a caller depends on register contents to remain the same before and after issuing a service, the caller must save the contents of a register before issuing the service and restore them after the system returns control.