RE: [MI400] using _pcoptr proc. was: Attention Users of *SYSTEM State

["Steve Richter" <srichter@xxxxxxxxxxxxx>]

oh, it works if your program is system state.  but when IBM takes away the
ability to make a program system state, this method will no longer work.
Got it!

Actually, I still dont understand the system state thing.  A few months ago
I wrote a rudimentary PowerPC assembler.  I then used that assembler to
assemble some simple PPC code and placed that code in a user space.  I then
used SST to patch an RPG program to make it branch to my user space
assembler code.

When I was not crashing my system because of a PPC coding error I was able
to do things like change the sub type of a user space. I was also able to
read the bytes of a program object ( the return address in my patched RPG
program ) and run those bytes thru a basic disassembler that I wrote.

Using the 8 byte pointers of the PowerPC CPU, I set the pointer to the start
of the object ( the 32 byte object header ).  Then I change the sub type
field to an arbitrary value.  It made the user space disappear!   I thought
your program had to be system state to change the sub type of an object or
read the bytes of a program object?

-Steve

-----Original Message-----
From: mi400-bounces@xxxxxxxxxxxx [mailto:mi400-bounces@xxxxxxxxxxxx]On
Behalf Of Douglas Handy
Sent: Thursday, March 10, 2005 1:16 PM
To: MI Programming on the AS400 / iSeries
Subject: Re: [MI400] using _pcoptr proc. was: Attention Users of *SYSTEM
State


Steve,

> How does this code that Gene posted run without getting a storage
protection
> violation (MCH6801) ?

Isn't that the point of Gene's request for a sanctioned API to do this
instead of the unauthorized means necessary now?
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