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From: jnc@mercury.lcs.mit.edu (Noel Chiappa)
Subject: Re: [TUHS] Fwd: Choice of Unix for 11/03 and 11/23+ Systems
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    > From: Paul Riley

    > Always darkest before the dawn.

Well, we'll see.


I found _that_ one; process 1 managed to exec() init, do a fork(), and then
the child process exec()'d the shell - then that apparently died, and the code
in init falls through into:

	termall();
	execl(init, minus, 0);

when the single-user shell exits, so then init restarted; rinse, repeat.

So a _lot_ of the code in mch.s seemed to be working correctly; system calls
(2 exec()'s, and a fork()) worked, processing switching worked, device
interrupts (for the disk and console tty) seemed to be working.. Not sure
what's left!

So I looked at mch.s again, to see what else _was_ there, and I noticed a
place where I used R0 as a temp - with the MFPS/MTPS thing to get to the PS,
instructions like:

      BIS	#340, PS

need to change to:

     MFPS	R0
     BIS	#340, R0
     MTPS	R0

and R0 was being used to hold an arg (in pword:), and was being bashed.


So I fixed it, and now the shell starts OK, but attempting to do any command
(e.g. "echo foo"), things hang (the shell doesn't fork). If I type the
interrupt character, the shell exits, and init restarts.

Oh well, hopefully this one won't be too painful to work out. The system's
mostly working, which I think will really help.

     Noel