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137 lines
3.3 KiB
NASM
137 lines
3.3 KiB
NASM
[org 0x7c00]
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[bits 16]
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;cmp dl, 0x05
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;je welcome
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mov [bootdev], dl ; Save boot device number
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; Use the boot drive number passed to us by BIOS in register DL
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welcome:
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xor ax,ax ; We want a segment of 0 for DS for this question
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mov ds,ax ; Set AX to appropriate segment value for your situation
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mov es,ax ; In this case we'll default to ES=DS
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mov bx,0x8000 ; Stack segment can be any usable memory
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mov ss,bx ; This places it with the top of the stack @ 0x80000.
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mov sp,ax ; Set SP=0 so the bottom of stack will be @ 0x8FFFF
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cld ; Set the direction flag to be positive direction
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mov si, wolf_wel_msg
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call wolf_print
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start:
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mov ah, 0x00
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int 0x16
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cmp al, "0"
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je load_it_all_0
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cmp al, "1"
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je load_it_all_1
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jmp over
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load_it_all_0:
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mov si, wolf_kernel_load
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call wolf_print
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pushf
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stc
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mov ah,00
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int 13h
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.read_sector:
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mov ax, 0x0
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mov es, ax ; ES = 0
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mov bx, 0x2000 ; BX = 0x1000. ES:BX=0x0:0x1000
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; ES:BX = starting address to read sector(s) into
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mov ah, 02 ; Int 13h/AH=2 = Read Sectors From Drive
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mov al, 01 ; Sectors to read = 1
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mov ch, 00 ; CH=Cylinder. Second sector of disk
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; is at Cylinder 0 not 1
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mov cl, 03 ; Sector to read = 2
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mov dh, 00 ; Head to read = 0
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; DL hasn't been destroyed by our bootloader code and still
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; contains boot drive # passed to our bootloader by the BIOS
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mov dl, [bootdev]
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int 13h
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jc wolf_error
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popf
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jmp 0x0:0x2000
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cli
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hlt
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load_it_all_1:
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mov si, wolf_kernel_load
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call wolf_print
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pushf
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stc
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mov ah,00
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int 13h
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.read_sector:
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mov ax, 0x0
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mov es, ax ; ES = 0
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mov bx, 0x1000 ; BX = 0x1000. ES:BX=0x0:0x1000
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; ES:BX = starting address to read sector(s) into
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mov ah, 02 ; Int 13h/AH=2 = Read Sectors From Drive
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mov al, 01 ; Sectors to read = 1
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mov ch, 00 ; CH=Cylinder. Second sector of disk
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; is at Cylinder 0 not 1
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mov cl, 02 ; Sector to read = 2
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mov dh, 00 ; Head to read = 0
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; DL hasn't been destroyed by our bootloader code and still
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; contains boot drive # passed to our bootloader by the BIOS
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mov dl, [bootdev]
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int 13h
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jc wolf_error
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popf
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jmp 0x0:0x1000
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cli
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hlt
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wolf_error:
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mov si, wolf_error_msg
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call wolf_print
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mov si, wolf_error_msg1
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call wolf_print
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mov ah,00
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int 16h
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xor ax,ax
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int 19h
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wolf_print:
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lodsb
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or al,al
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jz exit
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mov ah,0x0e
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int 10h
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jmp wolf_print
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exit:
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ret
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over:
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jmp start
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; Moved the data before the boot signature but after the code
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wolf_wel_msg db 'Welcome to this publication..., press a key',0x0D,0x0A,0
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wolf_kernel_load db 'Loading program',0x0D,0x0A,0
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wolf_error_msg db 'Program not found!',0x0D,0x0A,0
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wolf_error_msg1 db 'Press any key to restart..',0
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bootdev db 0 ; Boot device number
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times 510-($-$$) db 0
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dw 0xAA55
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