无文件系统的u盘启动与文件加载处理程序-boot部分

摘要: vi编辑与阅读代码，nasm编译文件，dd写映像文件，bochs/真机运行程序
配合loader可以用于载入kernel文件
;bash脚本 [载入loader,loader_pro]
#!/bin/bash
nasm -o boot.bin boot.asm
nasm -I include/ -o loader.bin loader.asm
nasm -o loader_pro.bin loader_pro.asm
cat boot.bin loader.bin loader_pro.bin > j_boot.bin
sudo dd if=boot.bin of=c.img bs=5...

org 07c00h
jmp short BOOT_START
nop
BOOT_START:
;init
mov     ax,cs
mov     ds,ax
mov     es,ax
mov     ss,ax
mov     sp,BaseOfStack
;clear screen
call    cls
;message ->BootMessage [(cs:BootMessage,4,(0,0))]
mov        ax,cs
push    ax
mov     ax,BootMessage
push    ax
mov     ax,4
push    ax
mov     ax,0000h
push    ax
call    dispstr
add     sp,8
;--message end
;test disk
xor     ax,ax
mov     ah,41h
mov     bx,055aah
mov     dl,80h
int     13h
;--test end
jc      BOOT_ERROR
;message ->pass test [(cs:PassMessage,4,(1,0))]
mov     ax,cs
push    ax
mov     ax,PassMessage
push    ax
mov     ax,4
push    ax
mov     ax,0100h
push    ax
call    dispstr
add     sp,8
;--message end
jmp     BOOT_LOADER
BOOT_ERROR:
;message ->fail test [(cs:ErrorMessage,5,(1,0))]
mov     ax,cs
push    ax
mov     ax,ErrorMessage
push    ax
mov     ax,5
push    ax
mov     ax,0100h
push    ax
call    dispstr
add     sp,8
;--message end
jmp $

;load loader
BOOT_LOADER:
call    cls
;message ->LoadMessage [(cs:LoadMessage,7,(0,0))]
mov     ax,cs
push    ax
mov     ax,LoadMessage
push    ax
mov     ax,7
push    ax
mov     ax,0000h
push    ax
call    dispstr
add     sp,8
;--message end
;readsector [1,100,1000h:0h]
mov        eax,1
push    eax
mov        ax,100
push    ax
mov        ax,1000h
push    ax
mov        ax,0h
push    ax
call    readsector
add        sp,10
;--end readsector
;jmp to loader
jmp     1000h:0000h
;--end jmp
jmp     $

;data ->BootData
BaseOfStack equ 07c00h
BootMessage:
db  "boot   "
PassMessage:
db  "pass   "
ErrorMessage:
db  "error  "
LoadMessage:
db  "loading"
TestMessage:
db  "test   "
DAP:
PacketSize:        db  10h
Reserved:        db  0
BlockCount:        dw  100
BufferAddr_off:    dw  0000h
BufferAddr_Seg:    dw  1000h
BlockNum:        dq  1
;--data end

;function ->cls [clean screen]
cls:
mov ax,0600h
mov bx,0700h
mov cx,0
mov dx,0184fh
int 10h
mov ah,02h
mov bh,00h
mov dx,00h
int 10h
ret
;--function end

;function ->dispstr(u32 source,u16 lens,u16 (pos_x,pos_y)) [display string]
;[source es:bp 串地址,lens cx 串长度,pos_x dh 行,pos_y dl 列]
dispstr:
mov    ax,sp
add sp,2
pop    dx
pop    cx
pop    ax
mov    bp,ax
pop ax
mov es,ax
sub sp,10
mov ax,01301h
mov bx,0007
int 10h
ret
;--function end

;function ->readsector(u32 Blocknum,u16 blockcount,u16 seg,u16 off)
;[Blocknum 起始块数量,blockcount 读取块总数,seg:off 缓存区地址]
readsector:
add sp,2
pop    ax
mov    [DAP+4],ax
pop    ax
mov    [DAP+6],ax
pop    ax
mov    [DAP+2],ax
pop    eax
mov    [DAP+8],eax
sub sp,12
mov ax,0
mov ds,ax
mov ax,DAP
mov si,ax
mov dl,80h
mov ah,42h
int 13h
ret
;--function end

times   200h-2-($-$$)  db  0
dw  0xaa55