Path: utzoo!utgpu!attcan!uunet!mcvax!hp4nl!botter!star.cs.vu.nl!ast
From: ast@cs.vu.nl (Andy Tanenbaum)
Newsgroups: comp.os.minix
Subject: Re: 1.3c bootblok.s broken +FIX (was Re: 1.3c upgrade results[LONG])
Keywords: Minix, 1.3c, bugs, bootblok
Message-ID: <1498@ast.cs.vu.nl>
Date: 10 Oct 88 10:29:43 GMT
References: <1429@ast.cs.vu.nl> <14243@comp.vuw.ac.nz> <1454@ast.cs.vu.nl> <14265@comp.vuw.ac.nz>
Reply-To: ast@cs.vu.nl (Andy Tanenbaum)
Organization: VU Informatica, Amsterdam
Lines: 61

In article <14265@comp.vuw.ac.nz> jonathan@comp.vuw.ac.nz (Jonathan) writes:
>A Minix kernel built from bootblok.s as posted in 1.3c will *never*
>boot off a 360k floppy.  A context diff fixing this is included.
>I've tested it result on both 1.2M and 360k.

I have tried this fix also, and it seems to work.  It looks like ax was not
0 at the time of the call to the BIOS to reset, so it didn't reset.  I hope
bootblok.s now works everywhere.  Feedback is definitely welcome.  I have to
open the box full of styrofoam now, so let's see if I can get it right this
time.  Many thanks to Jonathan for the excellent detective work.

Sometimes we are all so used to USENET technology that we forget how amazing
it really is.  Try this on your mother some time: "A guy in Holland wrote some
software that I use on my computer, and he found a bug in it.  He announced
this on a computer network, and two days later another guy in New Zealand
found it and told me and 10,000 other interested people how to fix it.  Of the
100,000 lines in the software, there was one line missing."  I tried to describe
USENET to my father once, and his reaction was: "What century am I living in?"

In case anyone missed Jonathan's fix, it is listed below.

Andy Tanenbaum (ast@cs.vu.nl)



: This is a shar archive.  Extract with sh, not csh.
: This archive ends with exit, so do not worry about trailing junk.
: --------------------------- cut here --------------------------
PATH=/bin:/usr/bin:/usr/ucb
echo Extracting 'bootblok.cdif'
sed 's/^X//' > 'bootblok.cdif' << '+ END-OF-FILE ''bootblok.cdif'
X*** bootblok.old	Mon Oct 10 11:17:14 1988
X--- bootblok.s	Mon Oct 10 11:07:16 1988
X***************
X*** 136,142 ****
X  	mov	DSKBASE,ax
X  	seg	es
X  	mov	DSKBASE+2,dx
X! 	int	0x13		| diskette reset
X  
X  L1:
X  
X--- 136,143 ----
X  	mov	DSKBASE,ax
X  	seg	es
X  	mov	DSKBASE+2,dx
X! 	xor	ax,ax		| diskette reset
X! 	int	0x13
X  
X  L1:
X  
+ END-OF-FILE bootblok.cdif
chmod 'u=rw,g=r,o=r' 'bootblok.cdif'
set `wc -c 'bootblok.cdif'`
count=$1
case $count in
325)	:;;
*)	echo 'Bad character count in ''bootblok.cdif' >&2
		echo 'Count should be 325' >&2
esac
exit 0