From: H. Peter Anvin <hpa@zytor.com>
Date: Thu, 12 Jul 2007 00:44:18 +0000 (-0700)
Subject: MBR: shave off another byte
X-Git-Tag: syslinux-3.52-pre4~4
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=6bfbea466b2304fb8ad4c1d718f9c73635ead1c5;p=profile%2Fivi%2Fsyslinux.git

MBR: shave off another byte

Shave off another byte by using the not-frequently-used jmpw *%sp
instruction!
---

diff --git a/mbr/mbr.S b/mbr/mbr.S
index d2e7d0f..0822b53 100644
--- a/mbr/mbr.S
+++ b/mbr/mbr.S
@@ -262,12 +262,12 @@ boot:
 	jc	disk_error
 	cmpw	$0xaa55, (bootsec+510)
 	jne	missing_os		/* Not a valid boot sector */
-	movw	$driveno, %sp
+	movw	$driveno, %sp	/* driveno == bootsec-6 */
 	popw	%dx		/* dl -> drive number */
 	popw	%di		/* es:di -> $PnP vector */
 	popw	%es
 	cli
-	jmp	bootsec
+	jmpw	*%sp		/* %sp == bootsec */
 
 disk_error:
 	call	error