Usage notes

The exit must be reentrant.
The exit can receive control in cross memory mode.
The exit must use BAKR to save registers. No save area is provided on entry. It is called in AR mode and must save both general and access registers.
To install the SAF callable services router installation exit, create the load module, name it IRRSXT00, and load it into the link pack area (LPA).
The exit must provide its own recovery routine. If the exit routine terminates abnormally, its recovery routine gets control. If a recovery routine is not provided or if the recovery routine percolates, the recovery routine of the caller of the service stub will get control.
To determine the caller of the SAF callable service, use the function code in register 0 to determine which callable service is being called. Refer to Table 1, for the list of components and products that are possible callers of each service.
The usage notes that follow the callable service descriptions are also helpful in determining the caller.

Many services receive the CRED as a parameter. The CRED contains an audit function code, defined in macro IRRPAFC, which identifies the z/OS UNIX function calling the service. You can find additional information on which callable services are called by z/OS UNIX functions in the z/OS Security Server (RACF®) Auditor's Guide, under Classes that Control Auditing for z/OS UNIX System Services.