From owner-freebsd-hackers Thu Dec 20 4: 9: 2 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from mailout07.sul.t-online.com (mailout07.sul.t-online.com [194.25.134.83]) by hub.freebsd.org (Postfix) with ESMTP id 84A7B37B416; Thu, 20 Dec 2001 04:08:58 -0800 (PST) Received: from fwd04.sul.t-online.de by mailout07.sul.t-online.de with smtp id 16H20O-00022B-07; Thu, 20 Dec 2001 13:08:56 +0100 Received: from spirit.corecode.ath.cx (320050403952-0001@[80.128.114.172]) by fmrl04.sul.t-online.com with esmtp id 16H20A-04UHUeC; Thu, 20 Dec 2001 13:08:42 +0100 Received: from elevation.zuhause.stoert.net (elevation.zuhause.stoert.net [192.168.66.46]) by spirit.corecode.ath.cx (8.11.6/8.11.6) with ESMTP id fBKC8fg56145; Thu, 20 Dec 2001 13:08:41 +0100 (CET) (envelope-from corecode@elevation.zuhause.stoert.net) Received: (from corecode@localhost) by elevation.zuhause.stoert.net (8.11.6/8.11.6) id fBKC8fW00289; Thu, 20 Dec 2001 13:08:41 +0100 (CET) (envelope-from corecode) Date: Thu, 20 Dec 2001 13:08:38 +0100 From: corecode To: cewandys@yahoo.com Cc: msmith@FreeBSD.ORG, freebsd-hackers@FreeBSD.ORG Subject: Re: Thanx and another question Message-Id: <20011220130838.6c9d9d64.corecode@corecode.ath.cx> In-Reply-To: <20011220055601.E6ABC37B405@hub.freebsd.org> References: <20011220055601.E6ABC37B405@hub.freebsd.org> X-Mailer: Sylpheed version 0.6.6 (GTK+ 1.2.10; i386--freebsd4.4) Mime-Version: 1.0 Content-Type: multipart/signed; protocol="application/pgp-signature"; boundary="=.7YkSKMa)ps6rS(" X-Sender: 320050403952-0001@t-dialin.net Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG --=.7YkSKMa)ps6rS( Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 20 Dec 2001 14:2:16 +0800 Leslie Jackson wrote: > Now i think i've got a basic knowledge about the BIOS data area. > But reading the code of boot0.s, i got another question as in the > following code: > > main.5: incw dx # Next item > addb $0x10,bl # Next entry > jnc main.3 # Till done > > The partition table in MBR only has 4 items, why check for 16 times?? it doesn't check for 16. it adds 0x10 to bl and if bl overflows (prolly the end of the partition table. as sizeof(ever entry) == 0x10 and the 4th ends at 0x1fc another (a 5th) increment will overflow bl and result in a set carry flag. hope this helps cheerz corecode -- /"\ http://corecode.ath.cx/ \ / \ ASCII Ribbon Campaign / \ Against HTML Mail and News --=.7YkSKMa)ps6rS( Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.6 (FreeBSD) iD8DBQE8IdTJr5S+dk6z85oRAjRhAKDBJZ1WF1uNwL94VYjM0H4Yyg8dygCgrFC0 HDklbxnTPI2CRViRGn6XB0g= =a45p -----END PGP SIGNATURE----- --=.7YkSKMa)ps6rS(-- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message