Shave a byte off the MBR code.

diff --git a/mbr/mbr.S b/mbr/mbr.S
index 1e6842b..ea74a86 100644 (file)
--- a/mbr/mbr.S
+++ b/mbr/mbr.S
@@ -32,7 +32,7 @@
 stack          = 0x7c00
 driveno                = (stack-6)
 sectors                = (stack-8)
-secpercyl      = (stack-10)
+secpercyl      = (stack-12)
 
 BIOS_page = 0x462
 
@@ -92,6 +92,7 @@ next:
        andw    $0x3f, %cx      /* Sector count */
        pushw   %cx             /* Save sectors on the stack */
        xorw    %ax, %ax
+       pushw   %ax             /* High word of sectors/cylinder */
        movb    %dh, %al        /* dh = number of heads */
        incw    %ax             /* From 0-based to count */
        mulw    %cx             /* Heads*sectors -> sectors per cylinder */
@@ -111,9 +112,8 @@ next:
  */
 read_sector:
 read_sector_cbios:
-       movl    %eax, %edx
-       shrl    $16, %edx
-       divw    (secpercyl)
+       xorl    %edx, %edx
+       divl    (secpercyl)
        rorb    %ah
        rorb    %ah
        movb    %ah, %cl