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|
; asmsyntax=nasm
[org 0x7c00]
[bits 16]
boot:
cli
mov ax, 0x8000
mov ss, ax
mov sp, 0xffff
push cs
pop ds
xor bx, bx
mov ah, 0x0e
mov si, message
lodsb
.lewp:
int 0x10
lodsb
cmp al, 0
jne .lewp
; Enable A20
mov ax, 0x2401
int 0x15
mov bx, 0x1000
mov es, bx
xor bx, bx ; Load kernel @ 0x10000
mov cx, word [cur_lba]
.sector_loop:
call convert_lba_to_chs
mov ah, 0x02 ; cmd 0x02 - Read Disk Sectors
mov al, 1 ; 1 sector at a time
mov dl, 0 ; drive 0 (fd0)
int 0x13
jc fug
mov ah, 0x0e
mov al, '.'
int 0x10
inc word [cur_lba]
mov cx, word [cur_lba]
cmp cx, 600
jz .sector_loop_end
mov bx, es
add bx, 0x20
mov es, bx
xor bx, bx
jmp .sector_loop
.sector_loop_end:
call durk
; Turn off the floppy motor.
mov dx, 0x3f2
xor al, al
out dx, al
lgdt [cs:test_gdt_ptr]
mov eax, cr0
or al, 1
mov cr0, eax
jmp 0x08:pmode
durk:
push cs
pop ds
xor bx, bx
mov ah, 0x0e
mov si, msg_sectors_loaded
lodsb
.lewp:
int 0x10
lodsb
cmp al, 0
jne .lewp
ret
pmode:
[bits 32]
mov ax, 0x10
mov ds, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ss, ax
mov esp, 0x4000
xor eax, eax
xor ebx, ebx
xor ecx, ecx
xor edx, edx
xor ebp, ebp
xor esi, esi
xor edi, edi
jmp 0x10000
hlt
test_gdt_ptr:
dw (test_gdt_end-test_gdt)
dd test_gdt
test_gdt:
dd 0
dd 0
dd 0x0000ffff
dd 0x00cf9a00
dd 0x0000ffff
dd 0x00cf9200
dd 0
dd 0
dd 0
dd 0
test_gdt_end:
[bits 16]
fug:
xor bx, bx
mov ah, 0x0e
mov si, fug_message
lodsb
.lewp:
int 0x10
lodsb
cmp al, 0
jne .lewp
cli
hlt
; Input:
;
; AX = LBA
;
; Output:
;
; CX and DH = C/H/S address formatted for Int13,2
; CL = sector (LBA % sectors_per_track) + 1
;
; 1.44M floppy stats:
; (sectors_per_track: 18)
; (heads: 2)
; (sectors: 2880)
convert_lba_to_chs:
mov ax, cx
; AX = LBA/spt, DX = LBA%spt
xor dx, dx
div word [sectors_per_track]
; CL = sector (LBA % sectors_per_track) + 1
mov cl, dl
inc cl
; CH = track (LBA / sectors_per_track) / heads
mov ch, al
shr ch, 1
; AX = (LBA/spt)/heads, DX = (LBA/spt)%heads
xor dx, dx
div word [heads]
; DH = sector (LBA / sectors_per_track) % heads
mov dh, dl
ret
cur_lba:
dw 9
sectors_per_track:
dw 18
heads:
dw 2
msg_sectors_loaded:
db "sectors loaded", 0x0d, 0x0a, 0
message:
db "boot!", 0x0d, 0x0a, 0
fug_message:
db "FUG!", 0x0d, 0x0a, 0
times 510-($-$$) db 0
dw 0xaa55
|
