按着書上給的代碼打進去後,把tasm裝進虛拟機後,要注意一下的是:它選擇的不是安裝路徑,而是源檔案的盤。
還有在虛拟機運作中,老是出現NOLoad,為什麼找不到loader.bin呢?排錯排了很久,最後使用老辦法,發現是定義
LoaderFileName db "LOADER BIN", 0;
LoaderFileName db "LOADER BIN", 0 ;
我還真搞不清楚這兩個定義有那裡不同,但就是用CD光牒上的代碼的時候,才可以運作找到loader。why?
實在太奇怪了。
發現用debug調試.bin的時候,到13h程式就不能走下去了。就算我把軟碟加載進去了,也不行。
代碼:
%define _BOOT_DEBUG_
%ifdef _BOOT_DEBUG_
org 0100h
%else
org 07c00h
%endif
%ifdef _BOOT_DEBUG
BaseOfStack equ 0100h
%else
BaseOfStack equ 07c00h
%endif
BaseOfLoader equ 09000h;Loader.bin ±»¼ÓÔص½µÄλÖ᪡ª¶ÎµØÖ·
OffsetOfLoader equ 0100h ;Loader.bon ±»¼ÓÔص½µÄλÖ᪡ªÆ«ÒƵØÖ·
RootDirSectors equ 14 ;¸ùĿ¼ռÓõĿռä
SectorNoOfRootDirectory equ 19 ;Root Directory µÄµÚÒ»¸öÉÈÇøºÅ
SectorNoOfFAT1 equ 1; FAT1µÄµÚÒ»¸öÉÈÇøºÅ£¨=BPB_RsvdSecCnt£©
DeltaSectorNo equ 17
jmp short LABEL_START
nop; Õâ¸ö nop ²»¿ÉÉÙ
;ÏÂÃæÊÇFAT12´ÅÅ̵ÄÍ·
BS_OEMName db 'ForrestY' ;OEM String,±ØÐëÊÇ8×Ö½Ú
BPB_BytsPerSec DW 512 ;ÿÉÈÇø×Ö½ÚÊý
BPB_SecPerClus DB 1 ;ÿ×å¶àÉÙÉÈÇø
BPB_RsvdSecCnt DW 1 ;Boot ¼Ç¼ռÓöàÉÙÉÈÇø
BPB_NumFATs DB 2 ;¹²ÓжàÉÙ FAT ±í
BPB_RootEntCnt DW 224 ;¸ùĿ¼ÎļþÊý×î´óÖµ
BPB_TotSec16 DW 2880 ;Âß¼ÉÈÇø×ÜÊý
BPB_Media DB 0xF0 ;ýÌåÃèÊö·û
BPB_FATSz16 DW 9 ;ÿFATÉÈÇøÊý
BPB_SecPerTrk DW 18 ;ÿ´ÅµÀÉÈÇøÊý
BPB_NumHeads DW 2 ;´ÅÍ·Êý£¨ÃæÊý£©
BPB_HiddSec DW 0 ;Òþ²ØÉÈÇøÊý
BPB_TotSec32 DD 0 ;Èç¹û wTotalSectorCountÊÇ0£¬ÓÉÕâ¸öÖµ¼Ç¼ÉÈÇøÊý
BS_DrvNum DB 0 ;ÖжÏ13 µÄÇý¶¯Æ÷ºÅ
BS_Rservedl DB 0 ;δʹÓÃ
BS_BootSig DB 29h ; À©Õ¹Òýµ¼±ê¼Ç£¨29h£©
BS_VolID DD 0 ; ¾íÐòÁкÅ
BS_VolLab DB 'Tinix0.01 '; ¾í±ê£¬±ØÐë11×Ö½Ú
BS_FileSysType DB 'FAT12 ' ; ÎļþϵͳÀàÐÍ£¬±ØÐë8×Ö½Ú
LABEL_START:
mov ax, cs
mov ds, ax
mov es, ax
mov ss, ax
mov sp, BaseOfStack
xor ah, ah
xor dl, dl
int 13h
;ÏÂÃæ ÔÚAÅ˵ĸùĿ¼ѰÕÒ Loader.bin
mov word [wSectorNo], SectorNoOfRootDirectory
LABEL_SEARCH_IN_ROOT_DIR_BEGIN:
cmp word [wRootDirSizeForLoop], 0
jz LABEL_NO_LOADERBIN
dec word [wRootDirSizeForLoop]
mov ax, BaseOfLoader
mov es, ax
mov bx, OffsetOfLoader
mov ax, [wSectorNo]
mov cl, 1
call ReadSector
mov si, LoaderFileName
mov di, OffsetOfLoader
cld ;×÷Óã¿
mov dx, 10h
LABEL_SEARCH_FOR_LOADERBIN:
cmp dx, 0
jz LABEL_GOTO_NEXT_SECTOR_IN_ROOT_DIR
dec dx
mov cx, 11
LABEL_CMP_FILENAME:
cmp cx, 0
jz LABEL_FILENAME_FOUND
dec cx
lodsb
cmp al, BYTE [es:di]
jz LABEL_GO_ON
jmp LABEL_DIFFERENT
LABEL_GO_ON:
inc di
jmp LABEL_CMP_FILENAME
LABEL_DIFFERENT:
and di, 0FFE0H
add di, 20h
mov si, LoaderFileName
jmp LABEL_SEARCH_FOR_LOADERBIN
LABEL_GOTO_NEXT_SECTOR_IN_ROOT_DIR:
add word [wSectorNo], 1
jmp LABEL_SEARCH_IN_ROOT_DIR_BEGIN
LABEL_NO_LOADERBIN:
mov dh, 2
call DispStr
%ifdef _BOOT_DEBUG_
mov ax, 4c00h
int 21h
%else
jmp $
%endif
LABEL_FILENAME_FOUND:
mov ax, RootDirSectors
and di, 0ffe0h
add di, 01ah
mov cx, word [es:di]
push cx
add cx, ax
add cx, DeltaSectorNo
mov ax, BaseOfLoader
mov es, ax
mov bx, OffsetOfLoader
mov ax, cx
LABEL_GOON_LOADING_FILE:
push ax
push bx
mov ah, 0Eh
mov al, '.'
mov bl, 0fh
int 10h
pop bx
pop ax
mov cl, 1
call ReadSector
pop ax
call GetFATEntry
cmp ax, 0FFFH
jz LABEL_FILE_LOADED
push ax
mov dx, RootDirSectors
add ax, dx
add ax, DeltaSectorNo
add bx, [BPB_BytsPerSec]
jmp LABEL_GOON_LOADING_FILE
LABEL_FILE_LOADED:
jmp BaseOfLoader:OffsetOfLoader
;***************************************
;********************************
wRootDirSizeForLoop dw RootDirSectors
wSectorNo dw 0
bOdd db 0
;LoaderFileName db "LOADER BIN", 0;0 loader.bin
LoaderFileName db "LOADER BIN", 0 ;
MessageLength equ 9
BootMessage: db "Booting "
Message1 db "Ready. "
Message2 db "No LOADER"
;*********************************
;ReadSector
;********************************
ReadSector:
push bp
mov bp, sp
sub esp, 2
mov byte [bp -2], cl
push bx
mov bl, [BPB_SecPerTrk]
div bl
inc ah ;Z++
mov cl, ah
mov dh, al
shr al, 1
mov ch, al
and dh, 1
pop bx
mov dl, [BS_DrvNum]
.GoOnReading:
mov ah, 2
mov al, BYTE [bp -2]
int 13h
jc .GoOnReading
add esp, 2
pop bp
ret
;*******End of ReadSector
;**********************
;DispStr
DispStr:
mov ax, MessageLength
mul dh
add ax, BootMessage
mov bp, ax
mov ax, ds
mov es, ax
mov cx, MessageLength
mov ax, 01301h
mov bx, 0007h
mov dl, 0
int 10h
ret
;***End of DispStr
;;****************************
;GetFATEntry
GetFATEntry:
push es
push bx
push ax
mov ax, BaseOfLoader
sub ax, 0100h
mov es, ax
pop ax; mov byte [bOdd], 0
mov bx, 3
mul bx
mov bx, 2
div bx
cmp dx, 0
jz LABEL_EVEN
mov byte [bOdd], 1
LABEL_EVEN:
xor dx, dx
mov bx, [BPB_BytsPerSec]
div bx
push dx
mov bx, 0
add ax, SectorNoOfFAT1
mov cl, 2
call ReadSector
pop dx
add bx, dx
mov ax, [es:bx]
cmp byte [bOdd], 1
jnz LABEL_EVEN_2
shr ax, 4
LABEL_EVEN_2:
and ax, 0FFFH
LABEL_GET_FAT_ENRY_OK:
pop bx
pop es
ret
;End of GetFATEntry
times 510-($-$$) db 0 ; Ìî³äʣϵĿռ䣬ʹÉú³ÉµÄ¶þ½øÖÆ´úÂëÇ¡ºÃΪ512×Ö½Ú
dw 0xaa55 ;