This exit must be reentrant. The exit must have RMODE(24) and AMODE(ANY).

It is extremely important that the writer of the RACROUTE REQUEST=FASTAUTH exit routine be aware of the environment in which the routine will be executing. This routine is not invoked using standard linkage conventions. Its running environment offers limited function as indicated in the following list:

1. The execution key is unpredictable.
2. The exit might receive control in either supervisor or problem state.
3. The exit might or might not be given control APF-authorized.
4. The exit might be given control in SRB mode; that is, the REQUEST=FASTAUTH might have been issued by a caller running as an SRB.
5. The exit should not issue any SVCs.
6. The exit routine might be given control in either 24- or 31-bit mode.
7. The exit is responsible for saving and restoring certain registers it uses. The RACROUTE REQUEST=FASTAUTH exit parameter list contains a pointer (RFXWA) to a 16-word work area. The exit can use the first 15 words of this area to save and restore registers.
   On entry to the exit:

   • R1 contains the address of the exit parameter list, which contains a pointer to the 16-word FASTAUTH work area. In the FASTAUTH work area:
     • The 12th word contains the RACF® reason code that REQUEST=FASTAUTH processing has determined up to this point.
     • The 13th word contains the RACF return code that REQUEST=FASTAUTH processing has determined up to this point.
     • The 14th word contains 0.
     • The 15th word contains 0, and can be used by the exit to pass information to the postprocessing exit or the FASTAUTH caller.
   • R14 contains the return address.
   • R15 contains the address of the exit entry point.

   If the exit changes register 5, the exit must save that register and restore it before returning to RACF. The exit can modify any of the other registers without restoring the value the register had on entry to the exit.

   Of course, the R14 value is needed to return to RACF.

8. If ICHRFC00 or IGC0013{ is placed in the fixed link pack area (FLPA), the exit should also be in FLPA.

The RACROUTE REQUEST=FASTAUTH ICHRFX01 parameter list is the RACROUTE REQUEST=FASTAUTH input parameter list. Either the RFXP mapping or the FAST mapping in z/OS Security Server RACF Data Areas maps the parameter list.