157 lines
2.2 KiB
NASM
157 lines
2.2 KiB
NASM
[BITS 16] ;tell the assembler that its a 16 bit code
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jmp short bootcode
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nop
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bpOEMid db "XNOE "
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bpBytesPerSector dw 512
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bpSectorsPerCluster db 1
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bpReservedSectors dw 1
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bpNoFATs db 2
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bpRootDirEntries dw 256
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bpLVSectors dw 8419
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bpMediumID db 0F0h
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bpSectorsPerFat dw 9
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bpSectorsPerTrack dw 18
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bpSides dw 2
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bpHiddenSectors dd 0
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bpLargeSectors dd 0
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bpDriveNo dw 0
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bpSignature db 41
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bpVolumeID dd 00000000h
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bpVolumeLabel db "XNOE OS "
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bpFileSystem db "FAT16 "
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bootcode:
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mov ax, 7c0h
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mov ds, ax
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mov byte [drive], dl
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mov si, boot_msg
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call _boot_print
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mov ax, ds
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mov es, ax
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mov bx, buffer
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mov ah, 2
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mov al, 16
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mov cl, 20
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mov ch, 0
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mov dh, 0
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mov dl, byte [drive]
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int 13h
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mov cx, [bpRootDirEntries]
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mov di, buffer
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mov ax, 0
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; jmp $
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kernel_finder:
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xchg cx, dx
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mov di, buffer
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add di, ax
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; mov si, di
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; call _boot_print
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; mov si, new_line
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; call _boot_print
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mov si, kernel_file
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mov cx, 11
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rep cmpsb
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je kernel_found
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add ax, 20h
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xchg cx, dx
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loop kernel_finder
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mov si, kernel_nf
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call _boot_print
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jmp $
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kernel_found:
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mov ax, [es:di+0fh]
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mov word [cluster], ax
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fat_loader:
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mov ax, ds
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mov es, ax
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mov bx, buffer
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mov ah, 2
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mov al, 9
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mov cl, 2
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mov ch, 0
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mov dh, 0
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mov dl, byte [drive]
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int 13h
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kernel_loader:
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mov ax, 2000h
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mov es, ax
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mov bx, word [pointer]
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mov al, byte [cluster]
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mov word [buffer+20h], ax
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add al, 34
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mov cl, al
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mov al, 1
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mov ah, 2
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mov ch, 0
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mov dh, 0
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mov dl, byte [drive]
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int 13h
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add word [pointer], 512
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mov si, word [cluster]
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add si, buffer
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add si, 1
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cmp word [si], 0ffffh
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je kernel_loaded
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add word [cluster], 1
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jmp kernel_loader
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kernel_loaded:
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mov dword [buffer], 0xdeadbeef
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jmp 2000h:0h
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_boot_print:
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mov ah, 0eh
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mov cx, 1
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mov bh, 0
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_boot_print_loop:
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lodsb
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cmp al, 0
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je _boot_print_exit
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int 10h
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jmp _boot_print_loop
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_boot_print_exit:
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ret
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boot_msg db "Boot Sector OK!", 13, 10, 0
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kernel_nf db "KERNEL.BIN Missing!", 13, 10, 0
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new_line db " ", 0
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kernel_file db "KERNEL BIN"
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cluster dw 0
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pointer dw 0
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drive db 0
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TIMES 510 - ($ - $$) db 0 ;fill the rest of sector with 0
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DW 0xAA55 ; add boot signature at the end of bootloader
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buffer: |