bootnorm.asm: move disk access packet out of 440-446

#84 (comment)

source/fdisk/bootnorm.asm

@@ -16,10 +16,11 @@
  RELOCATED_OFFSET equ 0x0600
  PARTTBL_SIZE equ 64
  PARTTBL_OFFSET equ 0x1be
+ CODE_SIZE equ 440
 
 org RELOCATED_OFFSET
 
-start: 
+start:
  cli
  xor ax, ax
  mov ss, ax ; initialize stack
@@ -137,19 +138,17 @@ fatal: pop si ; this is the first character
  jmp short .wait_forever
 
 
-driveno db 0x0
-
 ;-----------------------------------------------------------------------------
 ; Padding bytes, BIOS disk access packet used by ext. INT13 LBA read function,
 ; reserved space for partition table and BIOS signature
 
 DAP_PACKET_SIZE equ 16
-PADDING_BYTES equ PARTTBL_OFFSET - DAP_PACKET_SIZE - ($ - $$)
+PADDING_BYTES equ CODE_SIZE - DAP_PACKET_SIZE - ($ - $$)
 
 %if PADDING_BYTES < 0
  ; Not strictly needed, because this is catched by the times
  ; directive below. But this gives a more meaningful error message.
- %error "bootsector too large, try decreasing code size"
+ %error "code too large, try to decrease size"
 %endif
 
 ; padding bytes to ensure bootsector is 512 bytes in size
@@ -175,7 +174,18 @@ dap:
  %error "Wrong DAP size"
 %endif
 
+
+reserved times 6 db 0 ; bytes 0x440-0x446 may contain operating
+ ; system specific data
 parttbl:
  times PARTTBL_SIZE db 0 ; space for partition table
 signature:
  db 0x55, 0xaa ; BIOS signature
+
+%if $ - $$ != 512
+ %error "wrong bootsector size"
+%endif
+
+
+absolute RELOCATED_OFFSET
+driveno resb 1 ; used as byte to store boot drive