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From: arm@cadre.ARPA (Alan Martello)
Newsgroups: net.unix-wizards
Subject: /dev/kUmem and other memory questions
Message-ID: <437@cadre.ARPA>
Date: Tue, 21-May-85 20:36:55 EDT
Article-I.D.: cadre.437
Posted: Tue May 21 20:36:55 1985
Date-Received: Fri, 24-May-85 20:31:43 EDT
Distribution: net
Organization: Decision Systems Lab., University of Pittsburgh
Lines: 25

lately, I have been wondering about accessing the memory of myself or
another process which I own.  I know that lots of programs (e.g. ps) does it
via /dev/kmem.  With that, am I correct in stating that you just examine the
namelist and you have the location in the CURRENT /dev/kmem (subject to
change without notice, dependent on number of variables, their size, etc.).
It states in my 4.2 mans that "per process data for the current process is
at virtual 0x7ffff000".  I this is all well and good, but what about
someone else's memory?  Also, even with this access, I can't write to
my own kernel memory (even though in some sense, it is mine).  I don't
really have an application in mind, but I though it would be rather
interesting to ponder this.  Another question I had was what is /dev/kUmem?
I assumed kernel user mem but my mans have no mention of this (PLEASE, no
flames if I missed something obvious).  I noticed /dev/kUmem has major device
number 3 (same as /dev/mem, /dev/kmem, and /dev/null).  Any wizards want to
comment on that one?  Ok, one final question: what happens when you run a
program.  It appears that it 1) reads your program, 2) loads it 3) somehow
runs it (must be magic).  My question stems with can you touch that 
running executable somehow (just like you can touch the running system
through /dev/kmem).  Either direct replies or postings are welcome.
Thanks in advance.

-- Al Martello
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