Date: Thu, 20 Dec 2001 13:08:38 +0100 From: corecode <corecode@corecode.ath.cx> 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>
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--=.7YkSKMa)ps6rS( Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 20 Dec 2001 14:2:16 +0800 Leslie Jackson <cewandys@yahoo.com> 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
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