IBM System/360 System Programmer's Guide

Reference SVC Routine
Code Types
5 3,4
6 2,3,4
7 2,3,4
8 4
Reference Notes
• Register 5 contains the address of the super-
visor request tlock (SVRB), if a type 2, 3,
or 4 SVC routine is in control. If a type 1
SVC routine is in control, register 5 con-
tains the address of the last active request
tlock.
• Register 6 through 12 contain unpredictable
information.
•
Register
13
contains the same information as
when
the SVC routine was called.
•
Register
14
contains the return address.
•
Register
15
contains
the
same information as
when the
SVC routine was called.
You must use registers 0, 1, and 15 if you want
to pass inforrr.ation to the calling program. The
contents of registers 2 through 14 are restored
when control is returned to the calling prograrr.
Because relocatatle address constants are not
relocated when a type 3 or 4 SVC routine is
loaded into main storage, you cannot use them in
coding these routines; nor can you use macro-
instructions whose expansions contain relocatable
address constants. Types 1 ana 2 are not
affected by this restriction since they are part
of the resident control program.
You can extend the SVRB, in 8-byte increments,
from 96 bytes up to 144 bytes. The extended area
is available as a work area during execution of
your routine only if you specify the extension
during the system generation process. When your
SVC routine receives control, register 5 contains
the address of the SVRB to which the extended
save area is appended.
You cannot issue the WAIT macro-instruction
unless you have changed the system mask to allow
I/O and external interruptions. If you have
allowed these interruptions, you can issue WAIT
macro-instructions that await either single or
multiple events. The event control block (ECB)
for single-event waits or the ECB list and ECBs
for mUltiple-event waits must be in dynamic main
storage.
When you issue an XCTL macro-instruction in a
routine under control of a type 4 SVRB, the new
load module is brought into a transient area.
The contents of registers 2 through 13 are
unchanged when control is passed to the load
module; register 15 contains the entry point of
the called load module.
Adding SVC Routines to the control Progran: 35

IBM System/360 Specifications

General

Brand	IBM
Model	System/360
Category	Desktop
Language	English