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  1. #1
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    Par défaut SVP HELP secteur de boot.

    Bonjour tout le monde,

    J'essaye d'écrire un secteur de boot qui permet de chercher un fichier sur une disquette et le copier en RAM, en s'appuyant sur ces tutos:

    http://tothpaul.developpez.com/boot/

    http://viralpatel.net/taj/tutorial/h...bootloader.php

    j'arrive a afficher un "HELLO WORLD" qui marche sur l'emulateur " portable PC/XT emulator" après avoir créer une disquette virtuelle avec "VFD" et y copier mon secteur avec "hex workshop".

    Code :
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    use16	;Tells the assembler that its a 16 bit code
    org $7C00	;Origin, tell the assembler that where the code will
    				;be in memory after it is been loaded
     
    MOV SI, HelloString ;Store string pointer to SI
    CALL PrintString	;Call print string procedure
    hlt		;Infinite loop, hang it here.
     
     
    PrintCharacter: ;Procedure to print character on screen
    	;Assume that ASCII value is in register AL
    MOV AH, 0x0E	;Tell BIOS that we need to print one charater on screen.
    MOV BH, 0x00	;Page no.
    MOV BL, 0x07	;Text attribute 0x07 is lightgrey font on black background
     
    INT 0x10	;Call video interrupt
    RET		;Return to calling procedure
     
     
     
    PrintString:	;Procedure to print string on screen
    	;Assume that string starting pointer is in register SI
     
    next_character: ;Lable to fetch next character from string
    MOV AL, [SI]	;Get a byte from string and store in AL register
    INC SI		;Increment SI pointer
    OR AL, AL	;Check if value in AL is zero (end of string)
    JZ exit_function ;If end then return
    CALL PrintCharacter ;Else print the character which is in AL register
    JMP next_character	;Fetch next character from string
    exit_function:	;End label
    RET		;Return from procedure
     
     
    ;Data
    HelloString db 'Hello World', 0 ;HelloWorld string ending with 0
     
    TIMES 510 - ($ - $$) db 0	;Fill the rest of sector with 0
    DW 0xAA55			;Add boot signature at the end of bootloader
    Helas, je peux pas aller plus loin c-à-d chercher un fichier sur la disquette et le copier ds la RAM.
    J'ai essayé plusieurs codes dénichés sur le web sans succès!!
    Voici un exemple:

    Code :
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    use16	
    ORG $7C00				  
     
    LOAD_SEGMENT = 0x1000			  
    FAT_SEGMENT  = 0x0ee0			  
     
    ;===========================================
    start:
        jmp main			   ;jump to beginning of code
        nop
    ;----------------------------------------
     OEM:	     db "DevOS   "    ;OEM String
     SectSize:   dw  0x200	       ;Bytes per sector
     ClustSize: db	1	      ;Sectors per cluster
     ResSect:   dw	1	      ;#of reserved sectors
     FatCnt:     db  2	       ;#of fat copies
     RootSize:   dw  224	       ;size of root directory
     TotalSect: dw 2880	     ;total ;of sectors if below 32 MB
     Media:      db  0xF0	       ;Media Descriptor
     FatSize:    dw  9	       ;Size of each FAT
     TrackSect: dw	9	      ;Sectors per track
     HeadCnt:   dw	2	      ;number of read-write heads
     HiddenSect: db   0		;number of hidden sectors
     Sect32:     db   0		;;sectors if over 32 MB
     BootDrive:  db  0	       ;holds drive that the boot sector came from
     Reserved:   db  0	       ;reserved, empty
     BootSign:   db  0x29	       ;extended boot sector signature
     VolID:      db "seri"	      ;disk serial
     acVolLabel:  db "MYVOLUME   " ;just placeholder. We don't yet use volume labels.
     acFSType:    db "FAT16   "    ;file system type
     
    ;===============================
    main:
      cli			     
      ;mov  dl, BootDrive    ;save what drive we booted from (should be 0x0)
      mov  ax, cs		 ;CS is set to 0x0, because that is where boot sector is loaded (0:07c00)
      mov  ds, ax		 ;DS = CS = 0x0 
      mov  es, ax		 ;ES = CS = 0x0
      mov  ss, ax		 ;SS = CS = 0x0
      mov  sp, 0x7C00	 ;Stack grows down from offset 0x7C00 toward 0x0000.
      ;sti                                   ; we don't need hardware interrupts
    ;-----------------------  
     
      mov  dl, [BootDrive]	 ;drive to reset
      xor  ax, ax		 ;subfunction 0
      int  0x13		;call interrupt 13h
      jc   bootFailure	;display error message if carry set (error)  
     
    ;-------------
     ; display loading message
      mov	 si,	loadmsg
      call	 WriteString
    ;---------------------
      mov	  ax, LOAD_SEGMENT
      mov	  es, ax
      mov	  ax, 32
      xor	  dx, dx
      mul	  word	[RootSize]
      div	  word	[SectSize]	     ;Divide (dx:ax,sectsize) -> (ax,dx)
      mov	  cx, ax		      
      mov	  [root_scts], cx
     
      xor	ax, ax			    ;find the root directory
      mov	al,  [FatCnt]	   ;ax = number of FAT tables
      mov	bx, word  [FatSize]	   ;bx = sectors per FAT
      mul	bx			    ;ax = #FATS * sectors per FAT
      add	ax, word  [HiddenSect]	  ;Add hidden sectors to ax
      adc	ax, word  [HiddenSect+2]
      add	ax, word  [ResSect]	   ;Add reserved sectors to ax
      mov	[root_strt], ax
     
      read_next_sector:
        push   cx
        push   ax
        xor    bx, bx
        call   ReadSector
     
      check_entry:
        mov    cx, 11		       ;Directory entries filenames are 11 bytes.
        mov    di, bx		       ;es:di = Directory entry address
        mov    si, kernelname		;ds:si = Address of kernelname we are looking for.
        repz   cmpsb		       ;Compare kernelname to memory.
        je	   found_file		       ;If found, jump away.
        add    bx, word  32        ;Move to next entry. Complete entries are 32 bytes.
        cmp    bx, word  [SectSize]      ;Have we moved out of the sector yet?
        jne    check_entry		       ;If not, try next directory entry.
     
        pop    ax
        inc    ax			       ;check next sector when we loop again
        pop    cx
        loopnz read_next_sector	       ;loop until either found or not
        jmp    bootFailure		       ;could not find file: abort
     
      found_file:
        mov    ax, [es:bx+0x1a]
        mov    [file_strt], ax
     
    ;------------------------------
        mov   ax, FAT_SEGMENT
        mov   es, ax
     
        ;Calculate offset of FAT:
        mov   ax, word  [ResSect]	     ;Add reserved sectors to ax  
        add   ax, word  [HiddenSect]    ;Add hidden sectors to ax
        adc   ax, word  [HiddenSect+2]
     
        ;Read all FAT sectors into memory:
        mov   cx, word  [FatSize]	     ;Number of sectors in FAT
        xor   bx, bx		      ;Memory offset to read into (es:bx)
      read_next_fat_sector:
        push  cx
        push  ax
        call  ReadSector
        pop   ax
        pop   cx
        inc   ax
        add   bx, word  [SectSize]
        loopnz read_next_fat_sector       ;continue with next sector
     
    ;----------------------------
     
        ;Set memory segment that will receive the file:
        mov     ax, LOAD_SEGMENT
        mov     es, ax
        ;Set memory offset for loading to 0.
        xor     bx, bx
     
        ;Set memory segment for FAT:
        mov     cx, [file_strt]		;CX now points to file's first FAT entry
     
      read_file_next_sector:
        ;Locate sector:
        mov     ax, cx		      ;Sector to read is equal to current FAT entry
        add     ax, [root_strt]		;Plus the start of the root directory
        add     ax, [root_scts]		;Plus the size of the root directory
        sub     ax, 2		      ;... but minus 2
     
        ;Read sector:
        push    cx			      ;Read a sector from disk, but save CX
        call    ReadSector		      ;as it contains our FAT entry
        pop     cx
        add     bx, [SectSize]	     ;Move memory pointer to next section
     
        ;Get next sector from FAT:
        push    ds			      ;Make DS:SI point to FAT table
        mov     dx, FAT_SEGMENT	      ;in memory.
        mov     ds, dx
     
        mov     si, cx		      ;Make SI point to the current FAT entry
        mov     dx, cx		      ;(offset is entry value * 1.5 bytes)
        ;shr     dx
        add     si, dx
     
        mov     dx, [ds:si] 	      ;Read the FAT entry from memory
        test    dx, 1		      ;See which way to shift
        jz	    read_next_file_even
        and     dx, 0x0fff
        jmp     read_next_file_cluster_done
    read_next_file_even:	
        shr     dx, 4
    read_next_file_cluster_done:	
        pop     ds			      ;Restore DS to the normal data segment
        mov     cx, dx		      ;Store the new FAT entry in CX
        cmp     cx, 0xff8		      ;If the FAT entry is greater or equal
        jl	    read_file_next_sector     ;to 0xff8, then we've reached end-of-file
     
    ;--------------------------------
        ; Make es and ds point to segment where 2nd stage was loaded.
        mov     ax, word  LOAD_SEGMENT
        mov     es, ax
        mov     ds, ax
        ; Jump to second stage start of code:    
        jmp     LOAD_SEGMENT:0
    ;-------------------
    ;then reboot.
    bootFailure:
      mov	 si, diskerror
      call	 WriteString
     
      call	 Reboot
    ;=============================
    ; functions
    ;============================
     
     WriteString:
      lodsb 		  ; load byte at ds:si into al (advancing si)
      or	 al, al 	  ; test if character is 0 (end)
      jz	 WriteString_done ; jump to end if 0.
     
      mov	 ah, 0xe	  ; Subfunction 0xe of int 10h (video teletype output).
      mov	 bx, 7		  ; Set bh (page number) to 0, and bl (attribute) to white (9).
      int	 0x10		  ; call BIOS interrupt.
     
      jmp	 WriteString	  ; Repeat for next character.
     
     WriteString_done:
      ret
    ;----------------------------------------
     Reboot:
      mov	si, rebootmsg	 ; Load address of reboot message into si
      call	 WriteString	  ; print the string
      xor	 ax, ax 	  ; subfuction 0
      int	 0x16		  ; call bios to wait for key
     
      db  0xEA	       ; machine language to jump to FFFF:0000 (reboot)
      dw  0x0000
      dw  0xFFFF
    ;---------------------------------------------
     
    ReadSector:
      xor	  cx, cx		      ; Set try count = 0
     
     readsect:
      push	  ax			      ; Store logical block
      push	  cx			      ; Store try number
      push	  bx			      ; Store data buffer offset
     
      mov	  bx, [TrackSect]	     ; Get sectors per track
      xor	  dx, dx
      div	  bx			      ; Divide (dx:ax/bx to ax,dx)
    				      ; Quotient (ax) =  LBA / SectorsPerTrack
    				      ; Remainder (dx) = LBA mod SectorsPerTrack
      inc	  dx			      ; Add 1 to remainder, since sector 
      mov	  cl, dl		      ; Store result in cl for int 13h call.
     
      mov	  bx, [HeadCnt] 	     ; Get number of heads
      xor	  dx, dx
      div	  bx			      ; Divide (dx:ax/bx to ax,dx)
    				      ; Quotient (ax) = Cylinder
    				      ; Remainder (dx) = head
      mov	  ch, al		      ; ch = cylinder                      
      xchg	  dl, dh		      ; dh = head number
     mov	  ax, 0x0201		      ; Subfunction 2, read 1 sector
      pop	  bx			      ; Restore data buffer offset.
      int	  0x13
      jc	  readfail
     
      ; On success, return to caller.
      pop	  cx			      ; Discard try number
      pop	  ax			      ; Get logical block from stack
      ret
     
      readfail:   
      pop	  cx			      ; Get try number             
      inc	  cx			      ; Next try
      cmp	  cx, word  4	      ; Stop at 4 tries
      je	  bootFailure
     
      ; Reset the disk system:
      xor	  ax, ax
      int	  0x13
     
      ; Get logical block from stack and retry.
      pop	  ax
      jmp	  readsect
     
    ;=============================  
    ;PROGRAM DATA
    ;======================
    kernelname:	   db "KERNEL  BIN"
    rebootmsg:	  db "Press any key to reboot.",0
    diskerror:	  db "Disk error. ",0
    loadmsg:	  db "Loading KERNEL...",0
     
    root_strt:   db 0	 ;hold offset of root directory on disk
    root_scts:   db 0	 ;holds ;sectors in root directory
    file_strt:   db 0 ;holds offset of bootloader on disk
     
    ;====================================
     DB 510 - ($ - $$) DUP(0)  ; remplir à hauteur de 510 octets
     DW $AA55		   ; et placer le marqueur de disque bootable

    J'ai besoin de votre aide SVP.
    Merci

  2. #2
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    Par défaut

    essaye avec le petit utilitaire "amorc.com" dans le répertoire "util" de cette archive: http://bifur.olympe.in/zip/mrt14.zip (c'est mon ptit OS maison tout pourrit)

    il permet de modifier le programme d'amorçage d'une disquette pour que celle ci charge le fichier "syst.baz" a l'adresse 5000h:0000h puis fait un saut sur celui ci

    c'est pas très commenté je te l'accorde mais c'est en français et au besoin je peut expliquer plus en détail

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