From owner-freebsd-current Wed Jul 1 08:53:01 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id IAA01826 for freebsd-current-outgoing; Wed, 1 Jul 1998 08:53:01 -0700 (PDT) (envelope-from owner-freebsd-current@FreeBSD.ORG) Received: from austin.polstra.com (austin.polstra.com [206.213.73.10]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id IAA01818 for ; Wed, 1 Jul 1998 08:52:56 -0700 (PDT) (envelope-from jdp@austin.polstra.com) Received: from austin.polstra.com (jdp@localhost) by austin.polstra.com (8.8.8/8.8.8) with ESMTP id IAA04039; Wed, 1 Jul 1998 08:52:46 -0700 (PDT) (envelope-from jdp) Message-Id: <199807011552.IAA04039@austin.polstra.com> To: wpaul@skynet.ctr.columbia.edu Subject: Re: 'fatal trap 12' on boot (smp and up) In-Reply-To: <199806302138.RAA05124@skynet.ctr.columbia.edu> References: <199806302138.RAA05124@skynet.ctr.columbia.edu> Organization: Polstra & Co., Seattle, WA Cc: current@FreeBSD.ORG Date: Wed, 01 Jul 1998 08:52:46 -0700 From: John Polstra Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG In article <199806302138.RAA05124@skynet.ctr.columbia.edu>, Bill Paul wrote: > Basically, there's a jump and a no-op, about 60 bytes of stuff, then > the start of the boot code. The jump skips over the 60 bytes of whatever. > Initially I duplicated all of this in start.S and yes, it worked. But > I wanted to see how much of this was really necessary so I started > whittling things down. It turns out that all you really need to make > the bastard happy is the jump and the no-op. Hey, the jump plus nop form the "magic number". :-) As I recall, the original a.out magic number (0407) was simply the opcode word of the PDP-11 jump instruction. Some things never change. John -- John Polstra jdp@polstra.com John D. Polstra & Co., Inc. Seattle, Washington USA "Self-knowledge is always bad news." -- John Barth To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message