load remaining boot1 sectors

boot0.s

@@ -3,7 +3,8 @@
 ; --------------------------------------------------------------------
 ; R | 0x000000 - 0x000400: real-mode interrupt vector table
 ; R | 0x000400 - 0x000500: bios data area
-; U | 0x000500 - 0x007c00: stack
+; U | 0x000500 - 0x007000: stack
+; U | 0x007000 - 0x007c00: globals
 ; U | 0x007c00 - 0x007e00: boot sector
 ; U | 0x007e00 - 0x080000: conventional usable memory
 ; R | 0x080000 - 0x0a0000: extended bios data area (maximum possible size)
@@ -12,33 +13,12 @@
 ; R | 0x0c8000 - 0x0f0000: bios expansiosn
 ; R | 0x0f0000 - 0x100000: motherboard bios
 
-; BIOS puts our boot sector at 0000:7c00
-org 0x7c00
-; We're (probably) in real mode
-bits 16 
+%include "defines.s"
 
-; BASE STACK FRAME VARIABLE OFFSETS
-; --------------------------------------------------------------------
-; The boot drive number given to us by the BIOS.
-BOOT_DRIVE             equ 0x02
-; Boot drive geometry
-SECTORS_PER_TRACK      equ 0x04
-N_HEADS                equ 0x06
-; Starting LBA of the GPT partition entries array.
-GPT_ENTRIES_START_LBA  equ 0x08
-; Number of GPT entries, saturated to 16 bits.
-GPT_N_ENTRIES_16       equ 0x0a
-; Number of sectors to advance by once we've read every GPT entry in the current sector.
-GPT_SECTOR_STRIDE      equ 0x0c
-; Number of bytes to advance by in the current sector once we've read a GPT entry.
-GPT_BYTE_STRIDE        equ 0x0e
-; Number of GPT entries which can fit in a single sector.
-GPT_ENTRIES_PER_SECTOR equ 0x10
-GPT_CURRENT_ENTRY_IDX  equ 0x12
-GPT_SECTOR_ENTRY_IDX   equ 0x14
-GPT_SECTORS_LOADED     equ 0x16
-GPT_CURRENT_LBA        equ 0x18
-STAGE2_GPT_ENTRY_ADDR  equ 0x1a
+; BIOS puts our boot sector at 0000:7c00
+[org BOOT0_LOADPOINT]
+; We're (probably) in real mode
+[bits 16]
 
 main:
   ; Disable interrupts
@@ -49,10 +29,10 @@ main:
   mov ds, ax
   mov es, ax
 
-  ; Put the stack base at 0x7c00.
-  ; Stack grows high->low, so we'll grow away from our program text at 0x7c00.
+  ; Put the stack base at 0x7000.
+  ; Stack grows high->low, so we'll grow away from our globals and program text.
   mov ss, ax
-  mov bp, 0x7c00
+  mov bp, STACK_BASE
   mov sp, bp
 
   ; Segment for VGA (0xb800 * 16 = 0xb8000)
@@ -237,7 +217,7 @@ main:
   ja panic
 .stage2_end_lba_ok:
 
-  mov bx, 0x8200
+  mov bx, BOOT1_LOADPOINT
   call read_lba
   jmp bx
 
@@ -252,8 +232,6 @@ read_lba:
   ; head       = temp % n_heads
   ; cylinder   = temp / n_heads
   xor dx, dx
-  ; FIXME: we should probably get our globals from somewhere else, in case we want to change bp for
-  ; a function call
   ; Divide by sectors per track. dx = mod (sector - 1), ax = div (temp)
   div word [bp - SECTORS_PER_TRACK]
   ; Put the sector into cx (the bios call will use cl)