cos2000v2/boot/boot12.asm

[BITS 16]
[ORG 0x7C00]

section .text

start:
    jmp	near Boot
			
Disk_ID			    db	"COS2000A"	;Fabricant + n<> de s<>rie Formatage
Sectors_Size		dw	512		;Nombre d'octets/secteur
Sectors_Per_Cluster	db	1		;Nombre de secteurs/cluster
Reserved_Sectors	dw	1		;Nombre de secteurs r<>serv<72>
Fats_Number		    db	2		;Nombre de copies de la FAT
Fits_Number		    dw	224		;Taille du r<>pertoire racine
Sectors_Per_Disk	dw	2880		;Nombre secteurs du volume si < 32 Mo
Media_Descriptor	db	0xF0		;Descripteur de m<>dia
Sectors_Per_Fat		dw	9		;Nombre secteurs/FAT
Sectors_Per_Track	dw	18		;Nombre secteurs/piste
Heads_Number		dw	2		;Nombre de tete de lecture/<2F>criture
Sectors_Hidden		dd	0		;Nombre de secteurs cach<63>s
Sectors_Per_Disk2	dd	0		;Nombre secteurs du volume si > 32 Mo
Boot_Drive		    db	0		;Lecteur de d<>marrage
Reserved		    db	0		;NA (pour NT seulement)
Extended_Boot_ID	db	0x29		;Signature Boot <20>tendu 29h
Serial_Number		dd	0x01020304	;N<> de s<>rie
Disk_Name		    db	"COS2000    "	;Nom de volume
Fat_Type		    db	"FAT12   "	;Type de syst<73>me de fichiers

Boot_Message		db "Cos2000",0
Entre_Message       db "Fichier",0
Loading_Message		db "Charger",0
System_File		    db "Al",0,"o",0,"a",0,"d",0,"e",0,0x0F,0,0x38,"r",0,".",0,"s",0,"y",0,"s",0,0,0,0,0,0xFF,0xFF,0xFF,0xFF
Is_Ok			    db " [  OK  ]",0x0A,0x0D,0
Is_Failed		    db " [ERREUR]",0x0A,0x0D,0
The_Dot			    db '.',0

Boot_Error:
    mov	    si,Is_Failed
    call	ShowString
    xor     ax,ax
    int	    0x16
    int	    0x19

Boot_Ok:
	mov	    si,Is_Ok
	call	ShowString
	ret

Boot:
    push	cs
    push	cs
    pop	es
    pop	ds
	mov	[Boot_Drive],dl
    cli        
    mov	ax,0x9000
    mov	ss,ax
    mov	sp,0xFFFF
    sti
    mov si,Boot_Message
    call ShowString	
    xor	ax,ax
    int	0x13
    jc	Boot_Error
	mov	cx,[Reserved_Sectors]
    add	cx,[Sectors_Hidden]
    adc	cx,[Sectors_Hidden+2]
    mov	bx,[Sectors_Per_Fat]
    mov di,Fat_Buffer
    push bx
    push cx
readfat:
    call    ReadSector
    jc  Boot_Error
	inc cx
	add di,[Sectors_Size]
	dec bx
	jnz readfat          
    pop cx
    pop bx
    xor	ax,ax
    mov	al,[Fats_Number]
    mul	bx
    add	cx,ax
    mov	ax,32
    mul	word [Fits_Number]
    div	word [Sectors_Size]
    add	ax,cx
    sub	ax,2
    mov	word [Serial_Number],ax
    xor	dx,dx
	call	Boot_Ok
    mov si,Loading_Message
    call ShowString	
Find_System:
    mov	di,Buffer
    call	ReadSector
    jc	Near Boot_Error
    xor	bx,bx
Next_Root_Entrie:
    cmp	byte [di],0
    je	near Boot_Error
    push	di
    push	cx
    mov	si,System_File
    mov	cx,32
    rep	cmpsb
    pop	cx
    pop	di
    je	System_Found
    add	di,32
    add	bx,32
    inc	dx
    cmp	dx,[Fits_Number]
    ja	near Boot_Error
    cmp	bx,[Sectors_Size]
    jb	Next_Root_Entrie
    inc	cx
    jmp	Find_System
System_Found:
    call Boot_Ok
    mov si,Entre_Message
    call ShowString	
    mov	cx,[di+26+32]
    mov	ax,0x0080
    mov	es,ax
    push	es
    mov	di,0x0
    push	di
	mov	si,The_Dot
Resume_Loading:
    cmp	cx,0x0FF0
    jae	Finish_Loading
    push	cx
    add	cx,word [Serial_Number]
    call	ReadSector
    pop	cx
    jc  near Boot_Error
	call    ShowString
    add	    di,[Sectors_Size]
    call	NextFatGroup
    jc	near Boot_Error
    jmp	Resume_Loading
Finish_Loading:
	call	Boot_Ok
    retf

;====================READSECTOR=======================
;Lit le secteur logique LBA CX et le met en es:di
;-> CX (limit<69> <20> 65536 secteurs, soit 32 Mo avec secteur 512 octets)
;<- Flag Carry si erreur
;=====================================================
ReadSector:
	pusha
	mov ax,cx
	xor	dx,dx
	div	word [Sectors_Per_Track]
	inc	dl
	mov	bl,dl
	xor	dx,dx
	div word [Heads_Number]
	mov dh, [Boot_Drive]
	xchg    dl,dh
	mov	cx,ax
	xchg	cl,ch
	shl	cl,6
	or	cl, bl
	mov	bx,di
	mov	si, 4
	mov	al, 1
Read_Again:
  	mov	ah, 2
  	int	0x13
  	jnc	Read_Done
  	dec	si
  	jnz	Read_Again
Read_Done:
  	popa
	ret

;===================NEXTFATGROUP======================
;Renvoie en CX le groupe qui succ<63>de dans la FAT le groupe CX
;-> CX
;<-
;=====================================================
NextFatGroup:
	push	bx
	push	dx
	push	di
	mov	    ax,cx
	mov	    bx,ax
	and	    bx,0000000000000001b
	shr	    ax,1
	mov	    cx,3
	mul	    cx
	mov	    di,Fat_Buffer
	add	    di,ax
	cmp	    bx,0
	jnz	    Even_Group
Odd_Group:
	mov	    dx,[di]
	and	    dx,0x0FFF
	mov	    cx,dx
	jmp	    Next_Group_Found
Even_Group:
	mov	    dx,[di+1]
	and	    dx,0xFFF0
	shr	    dx,4
	mov	    cx,dx
Next_Group_Found:
	pop	    di
	pop	    dx
	pop	    bx
	ret

;======================SHOWSTR========================
;Affiche la chaine de caract<63>re point<6E> par ds:si <20> l'<27>cran
;-> DS, SI
;<- Flag Carry si erreur
;=====================================================
ShowString:
	    pusha
Next_Char:
        lodsb
        or	al,al
        jz	End_Show
        mov	ah,0x0E
        mov	bx,0x07
        int	0x10
        jmp	Next_Char
End_Show:
	    popa
        ret

times 510-($-$$) db ' '

dw	0xAA55

Buffer		equ $
Fat_Buffer	equ $+512

section .bss

;Buffer		resb 512
;Fat_Buffer	resb 10000