If you're not sure of something, try it! Here's my take, though it has not been tested.
RC4000 RSECT
LA 15,4000
BR 14
END RC4000
Other people made good suggestions, my example is the requirement reduced to the absolute minimum. I used RSECT rather than CSECT for two reasons.
- RSECT implies that the CSECT is read only, and the Assembler applies the same tests as specifying RENT.
- The read only attribute is carried into the load module. No verification is done, but it's there.
The read only attribute is used when linking the z/OS nucleus. The nucleus loader (which is part of the IPL procedure) uses it, but I no longer recall how it's used. Not that any of us are going to relink the nucleus. It's been 30 years, probably longer, since I've done it.