From: H. Peter Anvin <hpa@zytor.com>
Date: Fri, 15 May 2009 01:04:25 +0000 (-0700)
Subject: core/diskstart: handle more than 2^16 dwords
X-Git-Tag: syslinux-4.00-pre1~132
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=8af553fa455f857e151994acec91ad957e4b910b;p=profile%2Fivi%2Fsyslinux.git

core/diskstart: handle more than 2^16 dwords

Handle more than 2^16 dwords in the checksumming loop.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
---

diff --git a/core/diskstart.inc b/core/diskstart.inc
index c4fefbf..81b284f 100644
--- a/core/diskstart.inc
+++ b/core/diskstart.inc
@@ -577,22 +577,23 @@ load_rest:
 ;
 verify_checksum:
 		mov si,ldlinux_sys
-		mov cx,[LDLDwords]
-		mov edx,-LDLINUX_MAGIC
+		mov ecx,[LDLDwords]
+		mov eax,-LDLINUX_MAGIC
 		push ds
 .checksum:
-		lodsd
-		add edx,eax
-		and di,di
+		add eax,[si]
+		add si,4
 		jnz .nowrap
-		mov ax,ds
-		add ax,1000h
-		mov ds,ax
+		; Handle segment wrap
+		mov dx,ds
+		add dx,1000h
+		mov ds,dx
 .nowrap:
-		loop .checksum
+		dec ecx
+		jnz .checksum
 		pop ds
 
-		and edx,edx			; Should be zero
+		and eax,eax			; Should be zero
 		jz all_read			; We're cool, go for it!
 
 ;