Когда я запускаю с дискеты то выводит 'Read error!' ;------------------------------------------------------------; ; BOS - FAT12 bootsector ; ;------------------------------------------------------------; ; - FAT12 compatible. ; ; - Loads a binary file from the floppy. ; ; ; ; Thanks to: Petroff Heroj and John S. Fine for examples. ; ; ; ; by: Christoffer Bubach, 2003-2005 ; ; http://bos.asmhackers.net/ asmhacker@gmail.com ; ; ; ;------------------------------------------------------------; ; TODO: ; as i moved some 16-bit stuff to the kernel, i now got ; space to do proper testing (for data-area etc), ; fix that... ; ; TODO2: ; find out why this crap takes ages to load the kernel.. :S ; other notes: ; this code is public domain, and you can use it for ; anything you want. but if you do, please act polite and ; give credit. ; ; 16-bit mem map (seg:off) ; 0x0000:0x0000 -> 0x0000:0x0500 BIOS stuff ; 0x0000:0x0500 -> 0x0000:0x2100 FAT12 rootdir ; 0x0000:0x2100 -> 0x0000:0x3300 FAT for FAT12 ; 0x0000:0x3300 -> 0x0000:0x6c00 14,25kb free space ; 0x0000:0x6c00 -> 0x0000:0x7400 IDT, 256 descriptors ; 0x0000:0x7400 -> 0x0000:0x7c00 GDT, 256 descriptors ; 0x0000:0x7c00 -> 0x0000:0x7e00 bootsector ; 0x0000:0x7e00 <- 0x0000:0xffff ~32,5kb stack for boot ; 0x1000:0x0000 -> 0x9000:0xffff 576kb kernel/free space ; 0xa000:0x0000 -> ............. VGA mem etc. use16 org 0x7C00 boot: jmp near start nop ;------------------------------------------; ; Standard BIOS Parameter Block, "BPB". ; ;------------------------------------------; bpbOEM db 'BOS 0.04' bpbSectSize dw 512 bpbClustSize db 1 bpbReservedSec dw 1 bpbFats db 2 bpbRootSize dw 224 bpbTotalSect dw 2880 bpbMedia db 240 bpbFatSize dw 9 bpbTrackSect dw 18 bpbHeads dw 2 bpbHiddenSect dd 0 bpbLargeSect dd 0 ;---------------------------------; ; extended BPB for FAT12/FAT16 ; ;---------------------------------; bpbDriveNo db 0 bpbReserved db 0 bpbSignature db 41 ; 0 = nothing more. 41 = three more (below).. bpbID dd 1 bpbVolumeLabel db 'BOOT FLOPPY' bpbFileSystem db 'FAT12 ' ;----------------------------------------; ; starting point of bootsector code ; ;----------------------------------------; start: cli xor ax, ax ; initialize all the necessary mov ds, ax ; registers. mov es, ax mov ss, ax mov sp, 0xFFFF ; Stack.. mov [bpbDriveNo], dl sti ;----------------------------------; ; clear screen and print some ; ;----------------------------------; mov ax, 3 ; Set mode 0x03 int 0x10 mov bp, loading ; Print loading message. mov ax, 0x1301 mov bx, 7 mov cx, 12 mov dx, 0x0102 int 0x10 mov bl, 2 ; Set cursor. mov ah, 2 mov dx, 0x0201 int 0x10 mov ah, 9 ; Print 14 green dots. mov al, '.' mov cx, 14 int 0x10 ;---------------------------; ; load FAT and root ; ;---------------------------; mov di, 0x0050 ; Load the root to mov ax, 19 ; 0x0000:0x0500 (0x500/0x10) mov cx, 14 call read_sectors mov di, 0x0210 ; Load the fat to mov ax, 1 ; 0x0000:0x2100 mov cx, 9 call read_sectors ;------------------------; ; search for the file ; ;------------------------; mov dx, [bpbRootSize] mov bx, 0x0500 filesearch: cld mov si, filename mov cx, 11 mov di, bx repe cmpsb je found add bx, 32 dec dx jz error jmp filesearch ;-----------------------------------; ; variables & functions ; ;-----------------------------------; loading db 'Starting BOS' filename db 'KERNEL SYS' failure db 'Read error!' ;-----------------------------------------------; ; read a number of sectors (one at a time) ; ;-----------------------------------------------; ; in: ; ; di = segment to save at ; ; ax = sector to read ; ; cx = number of sectors ; ; out: ; ; di = updated (added for next read) ; ; ax = updated (added for next read) ; ;-----------------------------------------------; read_sectors: pusha mov bl, byte [bpbTrackSect] ; bl = number of sectors per track div bl ; al = ax / bl mov cl, ah ; cl = real sector number add cl, 1 xor ah, ah ; del the rest of the div before mov bl, byte [bpbHeads] ; bl = number of heads div bl ; ah = rest of ( ax / bx ), al = ax / bx mov ch, al ; ch = number of track mov dh, ah ; dh = the head number mov ax, cx ; save cx in ax mov cx, 6 ; try it 6 times .next_try: push es push cx mov cx, ax ; restore cx push cx xor ax, ax mov dl, [bpbDriveNo] ; reset drive push dx int 0x13 jc .failed pop dx pop cx xor bx, bx mov es, di mov ax, 0x0201 ; function 2, 1 sector int 0x13 jnc .ok ; if it was ok, check next.. .failed: pop dx pop ax pop cx pop es loop .next_try ; else try once again if there is an error jmp error ; if cx = 0 and the read operation failed, halt .ok: pop cx ; from the next_try loop pop es popa add di, 32 ; add 32 (512/16) to segment inc ax ; add sector counter loop read_sectors ret ;----------------------------------------------------; ; show a message and wait for a key before reboot ; ;----------------------------------------------------; error: mov bp, failure mov ax, 0x1301 mov bx, 4 mov cx, 11 mov dx, 0x0401 int 0x10 mov ah, 0 int 0x16 int 0x19 ;-----------------------------------; ; the file is found, load it. ; ;-----------------------------------; found: mov bp, [bx+26] ; bp=cluster number from directory entry mov di, 0x1000 ; 1000 (segment) .next_block: xor cx, cx mov cl, [bpbClustSize] ; reset sector count to 1 cluster mov si, bp ; si=next should-be cluster for ; contiguous reads .next_contiguous: mov ax, 3 ; 3 mul si ; multiply cluster number by 3 shr ax, 1 ; divide by two mov bx, ax mov ax, word [(0x2100+bx)] ; ax=FAT element with junk jc .odd_cluster ; jump if the value was odd and ax, 0x0FFF ; leave only lower 12 bits jmp .got_cluster ; got it .odd_cluster: shr ax, 4 ; (leave only bits 4-15) .got_cluster: inc si ; si=current cluster+1 cmp ax, si ; next cluster=current cluster+1? jne .force_read ; is it still contiguous? add cl, [bpbClustSize] ; increase sector count by 1 cluster adc ch, 0 ; add cf+0 to ch jmp .next_contiguous .force_read: xchg bp, ax ; ax=bp (base cluster), bp=new cluster dec ax ; decrease by 2 to get the actual... dec ax ; ...cluster number movzx dx, byte [bpbClustSize] mul dx ; multiply by sectors per cluster add ax, 33 ; add data-area location (33) call read_sectors cmp bp, 0x0FF8 ; is the new cluster EOF (FF8-FFF)? jb .next_block ; if not, read next block ;-----------------------; ; the file is loaded ; ;-----------------------; quit: jmp 0x1000:0x0000 ; jump to loaded file (64kb in mem) ;-------------------------------------; ; set the BOOT-signature at byte 510. ; ;-------------------------------------; rb boot+512-2-$ dw 0xAA55
Точно не BIOS. Взгляни на исходник. Т.к. это единственное сообщение об ошибке в тексте загрузчика, причины его возникновения могут быть разными. Например, отсутствует загружаемый файл.
