I have a boot loader that is user in a flopy disque (FAT12 File syst) and I want to load the kernel and the Interuption hundler routine (I use INT 20H).
When I load only one file (here the kernel) every thing works well but when I try to load 2 (Kernel+IntHandler) I have this error msg in bochs
int13_diskette: ctrl not ready.
When I debuged the programme I found that the fist file is loaded but when loading the second the problem occurs and the values of (Track,Sector,Head) = (7,13,0).
And here is the code(The original boot loader is not mine):
Code: Select all
[BITS 16]
[ORG 0x0]
jmp short start ; Standard start of boot sector
nop
bOEM db 'Test OS '
bSectSize dw 512 ; bytes/sector NEEDED ! FIXED
bClustSize db 1 ; sectors/allocation unit NEEDED ! (FIXED)
bResSect dw 1 ; # reserved sectors NEEDED ! (FIXED)
bFatCnt db 2 ; # of fats NEEDED
bRootSize dw 224 ; # of root directories NEEDED
bTotalSec dw 2880 ; # sectors total in image
bMedia db 240 ; media descrip: fd=2side9sec, etc...
bFatSize dw 9 ; # sectors in a fat NEEDED
bTrackSec dw 18 ; # sectors/track NEEDED ! FIXED
bHeadCnt dw 2 ; # heads
bHiddenSec dd 0 ; # hidden sectors
bHugeSec dd 0 ; # sectors if > 65536
bBootDrv db 00 ; drive number NEEDED ! FIXED
bReserved db 00
bBootSign db 41 ; extended boot signature
bVolID dd 0
bVolLabel db 'TEST OSV1.0'
bFSType db 'FAT12 '
; *********************
; Main program
; *********************
start:
mov [bBootDrv], dl ; Save boot drive
cli ; Disable the interrupts
mov ax, 0x07c0 ; setup the segment registers
mov ds, ax
mov es, ax
;It's in comment because I supected that there was a stack overflow
; mov ax, 0x0000 ; setup the stack
;mov ss, ax
; mov sp, 0xffff
sti ; Enable the interrupts
mov si, loading ; show 'Loading'
call print
; ********************
; Misc functions
; ********************
mov si, kernel ; which name?
;chargerFic:
;PUSH SI
getrootdir: ; catch the root directory
xor cx, cx
xor dx, dx
mov ax, 0x0020 ; ax=((32*RootSize)/512)+2
mul word [bRootSize]
div word [bSectSize]
;ADD AX,2 ;**********************************
xchg ax, cx
mov al, byte [bFatCnt]
mul word [bFatSize]
add ax, word [bResSect]
mov word [datasector], ax
add word [datasector], cx
mov bx, 0x0200 ; load to 7c00:0200
call readsectors
mov cx, word [bRootSize] ; counter
mov di, 0x0200 ; take first location
;POP SI
.loop:
push cx
mov cx, 0x000B ; check for 11 chars
push di
push si
rep cmpsb ; is it equal?
pop si
pop di
je getfat
pop cx
add di, 0x0020 ; next one, please
loop .loop
jmp error
getfat:
mov si, dot ; show dot to ensure something is done
call print
mov dx, word [di + 0x001A]
mov word [cluster], dx ; 1. file cluster
xor ax, ax
mov al, byte [bFatCnt] ; Fat Count
mul word [bFatSize] ; Fat Size
mov cx, ax
mov ax, word [bResSect] ; reserved sectors
mov bx, 0x0200 ; copy to 7c00:0200
call readsectors
; Load the kernel file
mov ax,word[segFic] ; load kernel to 1000:0000
mov es, ax
MOV BX,word[offsetFic]
push bx
mov si, dot ; show dot to ensure something is done
call print
load:
mov ax, word [cluster] ; cluster-counter
pop bx ; set buffer
sub ax, 0x0002 ; cluster-2
xor cx, cx
mov cl, byte [bClustSize] ; byte -> word
mul cx
add ax, word [datasector] ; base sector for data
xor cx, cx
mov cl, byte [bClustSize] ; Cluster Size
call readsectors
push bx
mov ax, word [cluster] ; check cluster
mov cx, ax ; copy cluster
mov dx, ax ; copy cluster
shr dx, 0x0001 ; dx / 2
add cx, dx ; sum for (3/2)
mov bx, 0x0200 ; FAT location
add bx, cx ; index into FAT
mov dx, word [bx] ; read two bytes
test ax, 0x0001
jnz .odd
.even:
and dx, 0000111111111111b ; only the low twelve
jmp .done
.odd:
shr dx, 0x0004 ; only the high twelve
.done:
mov word [cluster], dx ; store cluster
cmp dx, 0x0FF0 ; EOF?
jb load
MOV SI,IT
CMP WORD[segFic],0x0000 ;Si on a pas encore charger le fichier GESTIT.TOS alors on continue
JE suit
MOV WORD[segFic],0x0000
MOV WORD[offsetFic],0x0400
mov ax, 0x07c0 ; car on a changer ES
mov es, ax
MOV WORD[cluster],0x0000
;XOR AX,AX ;On re-initialise le controleur de la disquette
; MOV DL,1
;INT 0x13
JMP getrootdir
suit:
mov si, dot ; show 'a' to ensure something is done
call print
jmp dword 0x1000:0x0000 ; Jump to kernel
retf
error: ; Damn, an error occured
mov si, error_
call print
xor ax, ax
int 0x16 ; get key
int 0x19 ; reboot
print:
lodsb ; load byte at ds:si into al
or al, al ; test if char is 0 (end)
jz end
mov ah, 0x0E ; put char
mov bx, 0007 ; attribute
int 0x10 ; call BIOS
jmp print
end:
retn
readsectors:
.main
mov di, 0x0003 ; try to read 5 times
.sloop
push ax
push bx
push cx
xor dx, dx ; set dx:ax for operation
div word [bTrackSec] ; calc
inc dl ; set sector 0
mov byte [absSector], dl
xor dx, dx ; set dx:ax for operation
div word [bHeadCnt] ; calc
mov byte [absHead], dl
mov byte [absTrack], al
mov ax, 0x201 ; read one sector
mov ch, byte [absTrack] ; track
mov cl, byte [absSector] ; sector
mov dh, byte [absHead] ; head
mov dl, byte [bBootDrv] ; drive
int 0x13 ; call BIOS
jnc .goal ; error?
xor ax, ax ; reset disk
int 0x13 ; call BIOS
dec di ; error counter-1
pop cx
pop bx
pop ax
jnz .sloop ; read again
int 0x18
.goal
pop cx
pop bx
pop ax
add bx, word [bSectSize] ; next buffer
inc ax ; next sector
loop .main ; read next
retn
absSector db 0x00
absHead db 0x00
absTrack db 0x00
datasector dw 0x0000
cluster dw 0x0000
offsetFic dw 0x0000
segFic dw 0x1000
kernel db "KERNEL TOS"
IT db "GESTINT TOS"
loading db 'Loading',0
dot db '.', 0
error_ db 'Error',0
TIMES 510-($-$$) DB 0
DW 0xAA55
And thank you.