It looks correct, but I have a few style comments.
Use of "magic numbers" can obscure the code; I'd use the symbol from IHAPSA
The extraneous DROP R10 before USING ASVT,R10 is confusing.
You don't need to bump the pointer to AVTENTY before the loop.
Something like
USING PSA,R0
L R10,CVTPTR
USING CVTMAP,R10
L R11,CVTASVT
USING ASVT,R11
L R9,ASVTMAXU
LOOPASVT TM ASVTENTY,ASVTAVAL
BO NEXTASVT
L R10,ASVTENTY
USING ASCB,R10
...
NEXTASVT LA R11,4(,R11)
BCT R9,LOOPASVT
...
IHAPSA ,
CVT DSECT=YES
IHAASVT ,
...
Also, please read Peter's message.
--
Shmuel (Seymour J.) Metz
http://mason.gmu.edu/~smetz3
________________________________________
From: IBM Mainframe Discussion List [[email protected]] on behalf of
Bernd Oppolzer [[email protected]]
Sent: Sunday, February 5, 2023 5:33 AM
To: [email protected]
Subject: Re: Searching the ASVT
Thank you all for this discussion;
I have learned something new :-)
Would you kindly look at this coding and tell me, if it is correct in
your opinion,
and if it is allowed to execute this by non-privileged programs?
What macro calls do I need to get the needed definitions (CVT, ASVT, ASCB)?
Thanks in advance,
have a nice day
Bernd
*
*---------------------------------------------------------------------
* walk thru all ASCBs
*---------------------------------------------------------------------
*
L R10,16 LOAD ADDR OF CVT
USING CVT,R10 SET ADDRESSABILITY TO CVT
L R10,CVTASVT POINT TO ADDRESS SPACE VECTOR TABLE
DROP R10
USING ASVT,R10 SET ADDRESSABILITY TO ASVT
L R9,ASVTMAXU LOAD MAX. NUMBER OF ADDRESS SPACES.
LA R11,ASVTENTY LOAD ADDRESS OF FIRST ASCB POINTER
DROP R10
*
*---------------------------------------------------------------------
* R11 is moved over the table of all ASCB pointers
* R10 is no longer needed
* R9 contains the number of entries in the ASCB table
*---------------------------------------------------------------------
*
LOOPASVT DS 0H
TM 0(R11),ASVTAVAL VALID ASCB Available ?
BO NEXTASVT NO, CHECK NEXT ASVT ENTRY
*
*---------------------------------------------------------------------
* Examine ASCB
* Use R10 to address the ASCB
*---------------------------------------------------------------------
*
L R10,0(R11)
USING ASCB,R10
*
*---------------------------------------------------------------------
* access fields of current ASCB
*---------------------------------------------------------------------
*
* --- to be entered here ---
*
*---------------------------------------------------------------------
* advance R11 to next ASCB address
*---------------------------------------------------------------------
*
NEXTASVT DS 0H
LA R11,4(,R11) Advance to NEXT ASVT ENTRY
BCT R9,LOOPASVT
*
Am 05.02.2023 um 07:39 schrieb Tony Harminc:
> On Sat, 4 Feb 2023 at 18:00, [email protected] <[email protected]> wrote:
>
>
>> I am on a z/os 2.2 system, trying to rseurrect some old code.
>> .
>> can some one confirm the instructions for Searching the
>> Address Space Vector Table (ASVT) on z/OS 2.2
>> .
>> This program loads R10 with CVTASVT
>> L R10,CVTASVT GET ASVT ADDRESS
>> USING ASVT,R10 ESTABLISH ADDRESSABILITY
>>
> That's fine.
>
>
>> It then issues a Load Address For the first entry ?
>> This doesn't look correct to me ?
>> LA R11,ASVTENTY GET # OF FIRST ENTRY
>>
> It's fine. The ASVT has a bunch of header stuff, and then an array of
> fullword pointers starting at ASVTENTY. The PL/X declaration may make it a
> bit clearer.
>
> Next its test for an ASCB that is assigned.
>> TM 0(R11),ASVTAVAL VALID ASCB Available ?
>> BO RUNLOP1 NO, CHECK NEXT ASVT ENTRY
>>
> It's fine.I suppose there may be a serialization issue, e.g. an ASVT
> entry's assignment status may change after you've looked. But programs that
> either index the ASVT with the ASID (x 4), or those that go sequentially
> through the array and do <something> with each active address space have
> done it this way forever (i.e. since 1972), and I'm sure many are still out
> there working fine. Like anything, it's conceivable IBM could change this
> at some point, but it's such a basic interface in MVS--> z/OS that they
> would surely introduce some new data structure or API to access the list of
> ASCBs rather than change the ASVT and break things all over the place.
>
>
>> Besides the Load Address above - How should this module
>> advance to the Next ASVT entry ?
>>
> There's nothing wrong with the LA. The start of the array of ASCB pointers
> is at whatever offset ASVTENTY is at, and that hasn't changed in 50 years.
> The content of the header info has grown, but not the offset of the array
> of pointers.
>
>
>> Shoud I issue the following to get to the next ASVT
>> L R10,ASVTFRST
>>
> No. I think you're thinking that the entire ASVT has multiple instances
> that are chained together. There's only one, with an array of pointers on
> the end. ASVTFRST points somewhere you don't want - I think the first
> *available* ASCB, though IBM doesn't document the ASCB creation logic, and
> I assume things have changed with reusable ASIDs. Presumably you are not
> planning to modify the ASVT, so you're not looking for an available
> entry... If you are, well Just Don't. But effectively ASVTFRST is element 0
> of the array of ASCB pointers, and there's no ASID 0. So if you have the
> address of ASVTFRST (not the address that is *in* ASVTFRST), then you can
> multiply the ASID by 4 and use it as an origin-0 array index. If you start
> at ASVTENTY then it's origin-1, so add 4 (or 1 before you multiply by 4).
> Or if you want to look at all active ASCBs then start with the first array
> element, follow the pointer *if it's active*, and do whatever it is you
> want to do with each ASCB.
>
>
>> The current code issues the following instruction, which
>> looks incorrect according to IHAASVT
>> LA R11,4(,R11) Advance NEXT ASVT ENTRY
>>
> It's fine. I suppose if you want to be pedantic you could use L'ASVTENTY
> instead of hardcoding 4, but seriously, that's not going to change, and if
> it does all kinds of other things will break.
>
> Tony H.
>
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