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From: JPARR@UREGINA1.BITNET.UUCP
Newsgroups: comp.sys.amiga
Subject: Ami - MINIX problem for gurus
Message-ID: <8711180347.AA10717@jade.berkeley.edu>
Date: Tue, 17-Nov-87 22:31:15 EST
Article-I.D.: jade.8711180347.AA10717
Posted: Tue Nov 17 22:31:15 1987
Date-Received: Fri, 20-Nov-87 22:02:32 EST
Sender: daemon@ucbvax.BERKELEY.EDU
Lines: 23

Hi all:

     I ran across a technical difficulty when trying to port MINIX to the
Amiga.  How the heck can you do a fork?
     The problem is this.  When a process is first loaded in from disk, it
is nicely relocateable up until the time it runs.  Once it runs, however,
any pointers that it uses will be absolute addresses.  When copying the
parent over to the child, all pointers will still point to the parents
data area.  Amiga DOS must run up against similar problems, what does it do?
     Right now I can think of only two solutions.  The first is to have a
"running" area in memory.  Then whenever a process was scheduled, its image
would have to be copied into this area.  When finished, it would be recopied
back to its own area.  Obviously, this is not the best solution, although
it would work.  (maybe?)
     The second solution would be to remove the ability to fork altogether
and have a single fork_exec call to spawn new processes.  As soon as I do
this, MINIX is no longer very much like MINIX, so this isn't really too
ideal either.  Suggestions?
     (I guess that this means we will have to conceed that Intel did something
right . . . .)

Thanx,
JP