Just for starters.
1) I am looking at the registers at abend. Is it a 31 bit address with
the high-bit on, or is it a 32 bit address?
2) The programmer uses GETMAIN LOC=32 forgetting that he is passing an
address that is in that area to a subprogram that is not 32bit. Oops.
3) I am looking at a parameter list with 4 parms. The 2nd and the 4th
have the high-bit on. Is the 2nd parm the last parm or is not but
instead it is a 32 bit address and the 4th parm the last parm?
I am a vendor that writes system software that is called by application
programmers. I am not sure how I would validate that a 32 bit address
was 32 bit and not 31 bit. Or, the reverse.
IBM has the same problem when somebody calls their services. That is why
the BAR exists.
Tony Thigpen
Paul Edwards wrote on 05/06/2018 03:30 PM:
Who is disadvantaged by making memory above
2 GiB available to anyone who specifically requests it?
BFN. Paul.
On Sun, 6 May 2018 15:23:38 -0400, Tony Thigpen <[email protected]> wrote:
Bad idea. The 31bit bar is there for a very, very good reason.
Tony Thigpen
Paul Edwards wrote on 05/06/2018 02:51 PM:
Hi. I would like to submit an RFE to IBM to
support a LOC=32 parameter to GETMAIN,
giving 32-bit programs access to a full 4 GiB
instead of the current 2 GiB provided by
LOC=31. IBM can use the LOC=31 bits
plus the top bit of the option byte seen here:
https://www.ibm.com/support/knowledgecenter/SSLTBW_2.3.0/com.ibm.zos.v2r3.ieav200/svc120.htm
When the GETMAIN is executed in AM64,
memory above 2 GiB is potentially returned.
When executed in AM31, normal LOC=31
memory is obtained instead. This way the
application will still work on older systems
that aren't LOC=32 aware.
When obtaining LOC=32 memory, the GETMAIN
routine should search *down* the free memory
chain to find a free area, to preserve the LOC=31
space.
It is up to the application program to ensure that
when manipulating the LOC=32 memory it is in
AM64 and while in AM64 it does not attempt to
use the top bit of any 32-bit register as a flag.
After I submit the RFE it would be good if people
could upvote it. What is the best wording I can
use so that IBM understands what I am asking
for and doesn't reject it?
Thanks. Paul.
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