From 4a0db9e4fe62b042e28495f7a0f29646093dfa06 Mon Sep 17 00:00:00 2001
From: hpa <hpa>
Date: Sat, 5 Apr 2003 00:38:00 +0000
Subject: [PATCH] Actually come up with stack-switch code which has a prayer of
 working

---
 comboot.inc  |  2 +-
 pxelinux.asm | 25 ++++++++++++++++++++-----
 syslinux.doc |  5 +++--
 3 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/comboot.inc b/comboot.inc
index 4646369..c7efe82 100644
--- a/comboot.inc
+++ b/comboot.inc
@@ -1,7 +1,7 @@
 ;; $Id$
 ;; -----------------------------------------------------------------------
 ;;   
-;;   Copyright 1994-2002 H. Peter Anvin - All Rights Reserved
+;;   Copyright 1994-2003 H. Peter Anvin - All Rights Reserved
 ;;
 ;;   This program is free software; you can redistribute it and/or modify
 ;;   it under the terms of the GNU General Public License as published by
diff --git a/pxelinux.asm b/pxelinux.asm
index 793134e..2c25b01 100644
--- a/pxelinux.asm
+++ b/pxelinux.asm
@@ -1662,21 +1662,36 @@ unload_pxe:
 		; We need to switch to our local stack here...
 		pusha
 		pushf
+		push gs
 
 		mov si,sp
+		mov ax,ss
+		mov gs,ax
+		sub ax,[BaseStack+4]		; Are we using the base stack
+						; (as opposed to the COMBOOT stack)?
+		je .is_base_stack
+
+		lgs si,[SavedSSSP]		; COMBOOT stack
+.is_base_stack:
+
 		mov cx,[InitStack]
 		mov di,StackBuf
 		mov [BaseStack],di
 		mov [BaseStack+4],es
 		sub cx,si
 		sub di,cx
-		mov dx,cx			; New SP
-		ss rep movsb
+		mov [SavedSSSP],cx		; New SP
+		mov [SavedSSSP+2],es
+		gs rep movsb
 
-		cli
-		mov ss,cx			; CX == 0 here
-		mov sp,dx
+		and ax,ax			; Remeber which stack
+		jne .combootstack
+
+		; Update the base stack pointer since it's in use
+		lss sp,[SavedSSSP]
 		
+.combootstack:
+		pop gs
 		popf
 		popa
 %endif
diff --git a/syslinux.doc b/syslinux.doc
index d6e579b..f685958 100644
--- a/syslinux.doc
+++ b/syslinux.doc
@@ -623,5 +623,6 @@ archive, go to:
 
    http://www.zytor.com/mailman/listinfo/syslinux
 
-The mailing list changed in early 2002.  The old mailing list at
-kernel.org is no longer in use.
+Please DO NOT send HTML messages or attachments to the mailing list
+(including multipart/alternative or similar.)  All such messages will
+be bounced.
-- 
2.7.4