Path: utzoo!attcan!uunet!husc6!rice!sun-spots-request
From: daw@sun.com (Doug Ward)
Newsgroups: comp.sys.sun
Subject: L1-A
Message-ID: <8812151904.AA23589@fedora.sun.com>
Date: 22 Dec 88 20:39:04 GMT
Sender: usenet@rice.edu
Organization: Sun-Spots
Lines: 27
Approved: Sun-Spots@rice.edu
Original-Date: Thu, 15 Dec 88 11:04:27 PST
X-Sun-Spots-Digest: Volume 7, Issue 74, message 13 of 16

There seems to be confusion about how L1-A works.  Once the system is
booted, the L1-A sequence is  recognized in the kernel.  The kernel then
calls a routine in the PROM monitor to abort.  Actually, that's the same
routine that the kernel calls as the lasty thing it does during a halt.

At the cost of making system administration marginally harder, you can
disable L1-A in the kernel.  Then the only window of vulnerability will be
while the PROMS are in control and while boot is in control. 

For 4.0, look at:

zs_async.c:  zsa_xsint() -- this has code to detect breaks for terminal
				consoles and for unplugging the keyboard.

kbd.c:	  kbdinput() -- L1-A is caught here.

The part of the code you're interested in is the sequence of events
leading up to "montrap(*romp->v_abortent);".

The setup is pretty much the same in 3.x.

Personally, I think people who want UNIX machines without consoles and
people who want to power cycle hung machines instead of the "L1-A, g0"
sequence crazy, but I understand why the abort key is such a pain to
Universities.

	-daw