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ORG 0x7C00
SECTION .text
USE16
boot: ; dl comes with disk
; initialize segment registers
xor ax, ax
mov ds, ax
mov es, ax
mov ss, ax
; initialize stack
mov sp, 0x7C00
mov [disk], dl
mov si, name
call print
call print_line
mov bh, 0
mov bl, [disk]
mov ax, (startup_start - boot) / 512
mov bx, startup_start
mov cx, (startup_end - startup_start) / 512
xor dx, dx
call load
mov si, finished
call print
call print_line
jmp startup
; load some sectors from disk to a buffer in memory
; buffer has to be below 1MiB
; IN
; ax: start sector
; bx: offset of buffer
; cx: number of sectors (512 Bytes each)
; dx: segment of buffer
; CLOBBER
; ax, bx, cx, dx, si
; TODO rewrite to (eventually) move larger parts at once
; if that is done increase buffer_size_sectors in startup-common to that (max 0x80000 - startup_end)
load:
cmp cx, 64
jbe .good_size
pusha
mov cx, 64
call load
popa
add ax, 64
add dx, 64 * 512 / 16
sub cx, 64
jmp load
.good_size:
mov [DAPACK.addr], ax
mov [DAPACK.buf], bx
mov [DAPACK.count], cx
mov [DAPACK.seg], dx
; mov bx, [DAPACK.addr]
; call print_num
;
; mov al, '#'
; call print_char
;
; mov bx, [DAPACK.count]
; call print_num
;
; mov al, ' '
; call print_char
;
; mov bx, [DAPACK.seg]
; call print_num
;
; mov al, ':'
; call print_char
;
; mov bx, [DAPACK.buf]
; call print_num
;
; call print_line
mov dl, [disk]
mov si, DAPACK
mov ah, 0x42
int 0x13
jc error
ret
error:
mov si, errored
call print
call print_line
.halt:
cli
hlt
jmp .halt
%include "print16.asm"
line: db 13,10,0
disk: db 0
DAPACK:
db 0x10
db 0
.count: dw 0 ; int 13 resets this to # of blocks actually read/written
.buf: dw 0 ; memory buffer destination address (0:7c00)
.seg: dw 0 ; in memory page zero
.addr: dd 0 ; put the lba to read in this spot
dd 0 ; more storage bytes only for big lba's ( > 4 bytes )
times 510-($-$$) db 0
db 0x55
db 0xaa