cos2000v2/boot/boot12.asm

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[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