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[org 0x7C00]
%define KSTART 0x7E00
boot:
; init segment registers
xor ax, ax
mov ds, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ss, ax
; init stack
mov bp, 0x7C00
mov sp, bp
; print message
mov ebx, .msg
call print_str
; print boot drive
pusha
movzx eax, dl
call print_hex
call newline
popa
; load stage2 and stage3
call load_stages
; reclaim MBR space for stack
mov bp, KSTART
mov sp, bp
; pass offset of the file system as argument
mov edi, KSIZE+512
; jump into stage2
jmp KSTART
.msg: db 10, 13, "cuddles stage1", 10, 13, "boot drive: 0x", 0
load_stages:
mov ebx, .msg
call print_str
; mov si, 18 ; sectors per track
; mov di, 2 ; number of heads
; check if hard drive
; test dl, 0x80
; jz .start_load ; use defaults if not a hard drive
; backup dl
push dx
; get geometry
mov ah, 8
int 0x13
; restore dl
pop ax
mov dl, al
movzx si, cl
and si, 0x3f
movzx di, dh
inc di
.start_load:
pusha
mov ebx, .sectors
call print_str
movzx eax, si
call print_dec
call newline
mov ebx, .heads
call print_str
movzx eax, di
call print_dec
call newline
popa
; setup buffer
mov ax, KSTART/0x10
mov es, ax
mov bx, 0
mov cl, 2 ; sector=2
mov dh, 0 ; head=0
mov ch, 0 ; cylinder=0
.load:
mov ah, 0x02 ; read sectors from drive
mov al, 1 ; number of sectors
int 0x13
jc .fail ; CF set on error
; check read sectors count
cmp al, 1
jne .fail
; increase buffer pointer
mov ax, es
add ax, 512/0x10
mov es, ax
; check if finished
cmp ax, (KSTART+KSIZE)/0x10
jae .success
; next sector
inc cl
movzx ax, cl
cmp ax, si
jbe .load
; next head
mov cl, 1
inc dh
movzx ax, dh
cmp ax, di
jb .load
; next cylinder
mov dh, 0
inc ch
jmp .load
.success:
; restore es
mov ax, 0
mov es, ax
ret
.fail:
mov ebx, .fail_msg
call print_str
hlt
.msg: db "loading stage2 and stage3 from disk", 10, 13, 0
.fail_msg: db "disk failure, try rebooting", 10, 13, 0
.sectors: db "sectors per track: ", 0
.heads: db "number of heads: ", 0
%include "stage1/print.asm"
times 440-($-$$) db 0
db "hugs"
times 510-($-$$) db 0
dw 0xAA55
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