I just ran a simple test program to extract the Storage key from the first
4k:
psatest csect
psatest amode 31
psatest rmode any
bakr r14,r0
lr r12,r15
using psatest,r12
xr r4,r4
la r5,2048
MODESET MODE=SUP
ivsk r4,r5
MODESET MODE=PROB
DISPLAY REG=R4
xr r15,r15
pr
end psatest
- On z/OS 3.1 running on a z15 I get the result: 00000008 => That means
the Fetch protection bit is ON, which is expected.
- On z/OS 3.1 running on a z14 I get the result: 00000000 => That means
the Fetch protection bit is OFF.
That's really weird !!
On Fri, Aug 1, 2025 at 4:17 PM Seymour J Metz <[email protected]> wrote:
> Have you compared the page 0 storage key and the facility lists?
>
>
> --
> Shmuel (Seymour J.) Metz
> http://mason.gmu.edu/~smetz3
> עַם יִשְׂרָאֵל חַי
> נֵ֣צַח יִשְׂרָאֵ֔ל לֹ֥א יְשַׁקֵּ֖ר
>
>
>
>
> ________________________________________
> From: IBM Mainframe Discussion List <[email protected]> on behalf
> of Philippe Leite <[email protected]>
> Sent: Friday, August 1, 2025 3:08 PM
> To: [email protected] <[email protected]>
> Subject: Re: Strange S0C4 on z15
>
>
> External Message: Use Caution
>
>
> When I try to access 4096-8191 then I get S0C4-4, that is the expected
> result.
>
> On Fri, Aug 1, 2025 at 3:58 PM Seymour J Metz <[email protected]> wrote:
>
> > What abought 4096-8191?
> >
> > --
> > Shmuel (Seymour J.) Metz
> > http://mason.gmu.edu/~smetz3
> > עַם יִשְׂרָאֵל חַי
> > נֵ֣צַח יִשְׂרָאֵ֔ל לֹ֥א יְשַׁקֵּ֖ר
> >
> >
> >
> >
> > ________________________________________
> > From: IBM Mainframe Discussion List <[email protected]> on behalf
> > of Philippe Leite <[email protected]>
> > Sent: Friday, August 1, 2025 1:08 PM
> > To: [email protected] <[email protected]>
> > Subject: Re: Strange S0C4 on z15
> >
> >
> > External Message: Use Caution
> >
> >
> > It doesn't matter if CR0 bit 38 is on or off in this case. If this bit is
> > on, It only allows read access to address 0-2047. The PSA part 2048-4095
> is
> > ALWAYS protected. This is expected.
> > The problem I'm facing is that I can view the protected PSA part
> 2048-4095
> > when I'm in a z/OS 3.1 on a z14.
> >
> > When I run a simple program (User key 8) like this:
> >
> > psatest csect
> > psatest amode 31
> > psatest rmode any
> > bakr r14,r0
> > lr r12,r15
> > using psatest,r12
> > l r15,2048
> > xr r15,r15
> > pr
> > end psatest
> >
> > - On z/OS 3.1 running on a z15 this program ABEND S0C4-4 -> This is the
> > expected result.
> > - On z/OS 3.1 running on a z14 this program executes normally. -> This is
> > NOT the expected result !!
> >
> >
> >
> > On Fri, Aug 1, 2025 at 1:23 PM salva <[email protected]> wrote:
> >
> > > At the very least, take the dumps and compare bit 38 of CR0.
> > >
> > > El vie, 1 ago 2025 a las 18:09, Philippe Leite (<
> > > [email protected]>) escribió:
> > >
> > > > As I said to Rob, I already knew this POP rule for a long time, but
> it
> > > > doesn't answer this situation I'm facing.
> > > > It's exactly the same z/OS 3.1 version (same source and PTF level)
> but
> > > it's
> > > > working differently on a z14 and z15.
> > > >
> > > > Philippe Leite
> > > > z/OS System Programmer
> > > >
> > > > On Fri, Aug 1, 2025 at 1:04 PM salva <[email protected]> wrote:
> > > >
> > > > > From the POP:
> > > > >
> > > > > "Fetch-Protection-Override Control
> > > > > Bit 38 of control register 0 is the fetch-protection-
> > > > > override control. When the bit is one, key-controlled
> > > > > fetch protection is ignored for locations at effective
> > > > > addresses 0-2047."
> > > > >
> > > > > I don't know why it's different in your cases.
> > > > >
> > > > > El vie, 1 ago 2025 a las 16:40, Philippe Leite (<
> > > > > [email protected]>) escribió:
> > > > >
> > > > > > Interestingly, I am experiencing the same situation here.
> > > > > > In an LPAR running z/OS 3.1 on a z14, when I send the command
> “TSO
> > > > ISRDDN
> > > > > > B 800.”, I can view the contents of PSA 2048-4095.
> > > > > > But when I am in another LPAR with the same z/OS 3.1 on a z15,
> the
> > > same
> > > > > > command “TSO ISRDDN B 800.” shows me an error message “Storage
> > > > > unavailable.”
> > > > > >
> > > > > >
> > > > > > Philippe Leite
> > > > > > z/OS System Programmer
> > > > > >
> > > > > >
> > > ----------------------------------------------------------------------
> > > > > > For IBM-MAIN subscribe / signoff / archive access instructions,
> > > > > > send email to [email protected] with the message: INFO
> > > IBM-MAIN
> > > > > >
> > > > >
> > > > >
> > ----------------------------------------------------------------------
> > > > > For IBM-MAIN subscribe / signoff / archive access instructions,
> > > > > send email to [email protected] with the message: INFO
> > IBM-MAIN
> > > > >
> > > >
> > > >
> ----------------------------------------------------------------------
> > > > For IBM-MAIN subscribe / signoff / archive access instructions,
> > > > send email to [email protected] with the message: INFO
> IBM-MAIN
> > > >
> > >
> > > ----------------------------------------------------------------------
> > > For IBM-MAIN subscribe / signoff / archive access instructions,
> > > send email to [email protected] with the message: INFO IBM-MAIN
> > >
> >
> > ----------------------------------------------------------------------
> > For IBM-MAIN subscribe / signoff / archive access instructions,
> > send email to [email protected] with the message: INFO IBM-MAIN
> >
> >
> >
> >
> > ----------------------------------------------------------------------
> > For IBM-MAIN subscribe / signoff / archive access instructions,
> > send email to [email protected] with the message: INFO IBM-MAIN
> >
>
> ----------------------------------------------------------------------
> For IBM-MAIN subscribe / signoff / archive access instructions,
> send email to [email protected] with the message: INFO IBM-MAIN
>
>
>
>
> ----------------------------------------------------------------------
> For IBM-MAIN subscribe / signoff / archive access instructions,
> send email to [email protected] with the message: INFO IBM-MAIN
>
----------------------------------------------------------------------
For IBM-MAIN subscribe / signoff / archive access instructions,
send email to [email protected] with the message: INFO IBM-MAIN
