From 6d154a74c21df32fcc3b2fbef11039f2487dca75 Mon Sep 17 00:00:00 2001
From: "H. Peter Anvin" <hpa@zytor.com>
Date: Mon, 25 Feb 2008 15:44:24 -0800
Subject: gptmbr: save phdr -> bootsect on the stack, saving one byte

---
 mbr/gptmbr.S | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mbr/gptmbr.S b/mbr/gptmbr.S
index 10dfd45a..4009643f 100644
--- a/mbr/gptmbr.S
+++ b/mbr/gptmbr.S
@@ -115,6 +115,7 @@ next:
 	xorl	%edx,%edx
 	incw	%ax
 	movw	$phdr, %bx
+	pushw	%bx		/* -8(%bp) phdr == bootsect */
 	call	read_sector
 
 	/* Number of partition sectors */
@@ -189,12 +190,13 @@ found_part:
 
 /*
  * boot: invoke the actual bootstrap. %ds:%si points to the
- * partition information in memory.
+ * partition information in memory.  The top word on the stack
+ * is phdr == 0x7c00 == the address of the boot sector.
  */
 boot:
 	movl	(32+16)(%si),%eax
 	movl	(36+16)(%si),%edx
-	movw	$bootsec,%bx
+	popw	%bx
 	call	read_sector
 	cmpw	$0xaa55, -2(%bx)
 	jne	missing_os	/* Not a valid boot sector */
-- 
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