Re: [MI400] Dave McKenzie's UNDELete utility - a LifeSaver!

[Dave McKenzie <davemck@xxxxxxxxxxxxx>]

Well, probably something about the instruction has changed.  In every
new release of OS/400 (or whatever it's called today) IBM makes changes
to the machine code generator.  The offset of the instruction (3B54 when
I compiled it many releases ago) may have changed, or the register used
(3 at the time) may have changed.  Modifying machine instructions really
requires in-depth examination of the machine code.

That's what I meant by "curiosity and amusement".  I didn't mean for
people to try to recreate the pgm from source.

Gary didn't realize what mayhem he might be unleashing by asking for the
source :-)

My advice is "Don't try this at home!" unless you want to delve deeper
than any sane person should into registers and machine instruction
encoding.

--Dave

On Wed, 2004-09-01 at 09:38, Allen Hartley wrote:
> I compiled the UNDELM program and used SST to change the instruction 
> 3B54 to a value of F86100C8 and ran the program I get nothing back, just 
> a blank record.  What am I doing wrong.
> 
> Allen
> 
> Dave McKenzie wrote:
> 
> >Hmmm... let me see.
> >
> >Actually the source in undelsrc.zip is the RISC source.  However, you
> >can't just compile it to get a running pgm.  You have to modify a
> >machine instruction with SST.  (This is what Leif calls "Naughty,
> >Naughty, Naughty" :-)  But since it's only ONE instruction, maybe it
> >only deserves one "Naughty".
> >
> >BTW, I posted the source only for people's curiosity and amusement, at
> >the request of Gary Guthrie (may he rest in peace).