Already exists from IBM: Prime PSA.

Keith Moe
Amdahl/BMC retired


     On Wednesday, March 29, 2023, 04:24:25 PM PDT, Charles Mills 
<charl...@mcn.org> wrote:  
 
 Did anyone suggest this before?

On ***a test system only*** writing a special privileged program to fill all of 
the addresses from 0 to x'7F' except x'10'-x'13' with X'FF's. That might 
trigger errors and expose programs that were surviving the use of "normal" 
values from low addresses. And yes, you would have to account for prefixing. 

And please correct me if this makes no sense. I have not been real conversant 
with the exact usage of low memory since the early S/370 days.

Charles


-----Original Message-----
From: IBM Mainframe Assembler List [mailto:ASSEMBLER-LIST@LISTSERV.UGA.EDU] On 
Behalf Of syama prasad
Sent: Wednesday, March 29, 2023 4:09 PM
To: ASSEMBLER-LIST@LISTSERV.UGA.EDU
Subject: Re: Blocking Low core access from Assembler programs

 Hi,
Thanks for all the responses. It looks like there is no practical way to detect 
unintentional run-time access to page zero. Programs range fromĀ  50+ years old 
to quite recent. a recompile of everything with FLAG(PAGE0) and fixing obvious 
errors, followed by a test environment run of a few months under zOS 2.5 to 
catch any run-time errors seems to be the best way forward.
  

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