Question

我编写了一个MBR引导加载程序，它检测到分区但无法加载它们。中断13失败了，有没有人知道我做错了什么，我确信它现在傻傻地试图解决它几个小时

我的引导程序代码是：

[BITS 16]   ;tell the assembler that its a 16 bit code
[ORG 0]
%define PARTITION_TABLE_START 0x1be
%define PARTITION_TABLE_END 0x1ee
%define PARTITION_ENTRY_SIZE 16
%define COPY_DEST 0x7e00
_begin:
; We must copy the bootloader into a different area of memory
mov ax, 0
mov ds, ax
_copy:
mov si, 0x7c00+_begin
mov di, COPY_DEST
mov cx, 0
._continue:
lodsb
stosb
cmp cx, 0x200
je ._finish
inc cx  
jmp ._continue
._finish:
jmp 0x7e0:_start
_start:
; We are running at 0x7e00 now
mov ax, 0x7e0
mov ds, ax
mov es, ax
mov ss, ax

; Save drive number
mov byte[_drive_no], dl

mov si, _welcome_message
call _print


mov si, _find_message
call _print

mov bx, PARTITION_TABLE_START
_csearch:
cmp byte [bx], 0x80
je _bootable_found
cmp bx, PARTITION_TABLE_END
jae _no_bootable_found
add bx, PARTITION_ENTRY_SIZE
jmp _csearch


_bootable_found:
mov si, _found_message
call _print
; BX Contains current entry position
mov ah, 0x02
mov al, 1
mov dh, [bx+1], ; Head
mov cl, [bx+2] ; Sector
shr cl, 2 ; Ignore bit 6-7 they are not for us
mov ch, [bx+3] ; Cylinder (warning only 8 bits supported)
mov byte dl, [_drive_no] ; Drive number
; Destination: 0x7c00
push ax
mov ax, 0x7c0
mov es, ax
mov bx, 0
pop ax
int 0x13
jc _read_error
mov si, _press_any_key_to_load
call _print
mov ah, 0
int 0x16
; Read success lets jump to the new bootloader
jmp 0x7c0:0

_read_error:
mov si, _read_error_msg
call _print
jmp $

_no_bootable_found:
mov si, _no_partition
call _print
jmp $


_print:
    mov ah, 0x0e
._loop: 
    lodsb
    cmp al, 0
    je ._done
    int 0x10
    jmp ._loop
._done:
    ret
_welcome_message: db 'Welcome to NibbleBits bootloader', 10, 13, 0
_find_message: db 'Will find first active partition', 10, 13, 0
_found_message: db 'Active partition found', 10, 13, 0
_no_partition: db 'No active partition could be found', 10, 13, 0
_read_error_msg: db 'Failed to load partition', 10, 13, 0
_press_any_key_to_load: db 'Press any key to load the partition', 10, 13, 0
_drive_no: db 0

TIMES 510 - ($ - $$) db 0   ;fill the rest of sector with 0
DW 0xAA55           ; add boot signature at the end of bootloader
_end:

Answer 1

原来我的代码很好，确实改变了Michael Petch提出的一些东西，但实际的加载很好。问题是当我使用linux＆＃34; dd＆＃34;程序复制bootsector它截断整个文件。我通过启用一个标志来防止截断来解决这个问题。

从硬盘发出加载扇区

1 个答案: