On Mon, 10 Jun 2019 13:57:12 -0700 Charles Mills <[email protected]> wrote:

:>> Key0 is much much more dangerous than supervisor state (IMHO)

:>Interesting. I never thought of that, but I agree. Which is the more likely
:>error?

:>- You accidentally code some privileged instruction that you did not intend?

Perhaps with a wild branch. Or you branch to user code.

:>- You code the wrong register number in an instruction, or destroy or forget
:>to initialize the contents of a register (at least on some code paths), or a
:>register gets incremented too far?

Supervisor state does not you to accidentally overwrite storage in a system
key. You need to set the PSW key or use one of the explicit keyed
instructions.

:>Charles
:>
:>
:>-----Original Message-----
:>From: IBM Mainframe Discussion List [mailto:[email protected]] On
:>Behalf Of Binyamin Dissen
:>Sent: Sunday, June 9, 2019 11:48 PM
:>To: [email protected]
:>Subject: Re: Any way to set the PKM in "open code".
:>
:>On Sun, 9 Jun 2019 20:15:40 -0400 Rob Schramm <[email protected]> wrote:
:>
:>:>I suspect John's answer will be
:>:>1) because it's cool to try new things
:>
:>Well, to do that he could encapsulate this code in a PC-CP with an altered
:>AKM. 
:>
:>:>2) because I want to limit the destruction if it goes wrong.
:>
:>Key0 is much much more dangerous than supervisor state (IMHO)
:>
:>:>Waiting for the real answer,
:>:>Rob
:>:>
:>:>On Sun, Jun 9, 2019, 6:22 PM Binyamin Dissen <[email protected]>
:>:>wrote:
:>:>
:>:>> On Fri, 7 Jun 2019 08:57:38 -0500 John McKown <
:>:>> [email protected]>
:>:>> wrote:
:>:>>
:>:>> :>I am not finding this. I want to change the PKM for my running, APF
:>:>> :>authorized, program to include key 0. Why? So that I can switch in and
:>:>> out
:>:>> :>of key 0 using an SPKA instruction rather than MODESET. But mainly so
:>:>> that
:>:>> :>I can use the MVCSK and MVCDK instructions to read & update key 0,
:>fetch
:>:>> :>protected, storage without going into key 0.
:>:>>
:>:>> :>Or am I just being silly (again)?
:>:>>
:>:>> Why not simply run supervisor state which allows access to all keys?
:>
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--
Binyamin Dissen <[email protected]>
http://www.dissensoftware.com

Director, Dissen Software, Bar & Grill - Israel


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