Am 19.01.2015 um 13:32 schrieb Peter Relson:
Even a non-authorized program which is linked RENT
can write into its STATIC CSECT.
But only if the program is not fetched from an APF-authorized
concatenation (and maybe that's a requirement for PL/I programs with this
characteristic).
In that case, the program can write into the program itself too.
For the static csect, does PL/I do something to keep track of CSECT
mappings and obtain storage for the static csect in user-key storage?
That's the only way that writing into that csect could "overcome" APF
authorization rules.
Peter Relson
z/OS Core Technology Design
I'm talking about simple user programs that are fetched from normal
not APF-authorized libraries. The STATIC CSECT (with compile option NORENT)
is part of the load module, so with normal MVS LOAD, it is fetched
together with
the program text, in user-key storage.
I don't really get the problem with this RENT / read only discussion.
Of course, normally a program linked as RENT should not change its
static stroage, but:
even a program that is linked as RENT may in certain circumstances
need to store some information in static storage. Think of a routine
that is
establishing a cache memory for a table access that is valid for ALL
parallel
running threads or subtasks. Then there should be ONE cache, and of course,
the anchor information for this cache has to be in static storage, and when
establishing the cache or accessing (or changing) the cache (which resides
in dynamic storage, of course), the anchor has to be written into the
static storage.
These cache accesses have to be protected by semaphors etc, of course
(or maschine instructions like compare & swap).
This was present before WSA was invented. If now with new releases of the
OpSys, all modules linked as RENT will be read only, we all are forced to
use WSA even with "classical" languages like PL/1, COBOL and C (without
++);
I don't like this ... for performance reasons. And this even will not
help, because
WSA exists once for every parallel task ... if I want ONE cache for all
parallel tasks,
as in my example, I have to find another solution. With "true static", I
knew where
to put the anchor of that cache.
Kind regards
Bernd
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