On 12/30/2011 5:52 AM, Peter Relson wrote:
I have noted a couple of omissions in the PoPs that I will submit
a Readers Comment for
I didn't notice that any of the things you mentioned regarding the PoOp
are necessarily omissions or things to be corrected (but I might have
missed it). You questioned the list of semiprivileged instructions, I
believe. That depends on what is meant by semiprivileged. If it means
"subject to one of the authorization mechanisms shown in table 5-6" then
TRAP2/TRAP are not. RP is not.
The wording in the PoOp tends to be extremely precise (not 100% correct,
but pretty darn close). I caution against assuming that terms mean what
they do not say they mean.
I understand, and I believe you. But, there are times (perhaps when
separate chapters are written or updated by different people) when
the consistency is not what I, personally, would like.
Consider
the Preface description of Chapter 10 says that chapter:
"contains detailed descriptions of all of the semiprivileged
and privileged instructions except for the I/O instructions."
Chapter 3 mentions a "semiprivileged program" - what is that?
(Chapter 5 also uses this term without
defining it)
Chapter 4 says "Another group of instructions, called semiprivileged
instructions, are executed by a CPU in the problem
state only if specific authority tests are met;
otherwise, a privileged-operation exception or a
special-operation exception is recognized."
Chapter 5 says "There are 23 semiprivileged instructions and also the
privileged LOAD ADDRESS SPACE PARAMETERS instruction
that are controlled by the authorization mechanisms."
(so, to go back to your point, LASP, and several
other instructions in the referenced table are
_not_ semiprivileged; it would be nice if that
table simply indicated if each instruction is
privileged or semiprivileged)
The table, Figure 5-6, titled "Summary of Authorization
Mechanisms" includes semiprivileged instructions _and_
some others; Looking carefully, I cannot discern which
of these 36 instructions are the 23 semiprivileged
instructions.
Chapter 10 has a table, Figure 10-1, in which RP has a characteristic
of 'Q', which is described as: "Privileged-operation
exception for semiprivileged instructions"
so it looks like RP is semiprivileged
In that same table, TRAP2 and TRAP4 have characteristic
'SO' which says "Special-operation exception" and I
find ambiguous: these instructions will not raise a
'Privileged-operation exception', according to the
table, so they are not privileged. Neither fish nor
fowl, eh?
So, this is the kind of thing I find difficult and in need of clarification.
Peter Relson
z/OS Core Technology Design
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