Question

通过创建一个简单的内核握住了我的手。我正在写引导程序。

我正在尝试在我的引导程序之外访问内存，这让我感到悲伤。尝试读取BIOS磁盘读取中断（代码0xAA）后，出现错误"fixed disk drive not ready"（代码int 0x13）。

This is the tutorial section I'm up to，以及电子书中相应的第28页（推荐阅读！）

这是我的引导程序boot_sect_main.asm：

;
; Simple bootsector that prints a line
;
[org 0x7c00]            ; Offset for start of loaded bootsector at mem address 0x7c00
                        ; Offets are treated absolutely -- i.e. from the beginning of memory, but
                        ; our code gives the offset from the start of our loaded code, i.e. the 

; Initialization
mov [BOOT_DRIVE], dl    ; BIOS stores boot drive in dl. Save for later.

mov bp, 0x8000          ; Set the stack far away from us
mov sp, bp 

; Load data
mov bx, 0x9000          ; Load sectors  0x0000:0x9000 (ES:BX)
mov dh, 2
mov dl, [BOOT_DRIVE]
call disk_load

mov dx, [0x9000]        ; Print first loaded word (expect to be 0xdada, see EOF)
call print_hex

mov dx, [0x9000 + 512]  ; Print first word from 2nd loaded sector
call print_hex

; Main
jmp $

%include "lib_str.asm"
%include "lib_disk.asm"

; Global variables
BOOT_DRIVE:   db 0
BOOT_MESSAGE: db "Booting custom OS...", 0

; Bootsector padding & magic number
times 510 - ($-$$) db 0
dw 0xaa55

times 256 dw 0xdada
times 256 dw 0xface

这是我的lib_disk.asm，在这里触发磁盘读取中断0x13：

; disk_load loads the DH sectors to ES:BX
; from drive DL.
; --paramaters--
; bx: offset. E.g. 0x9000 reads from 0x0000:0x9000.
; dh: number of sectors to read
; dl: boot drive
disk_load:
  pusha
  push dx          ; Store DX so we can recall how many sectors we
                   ; requested to read.
  mov ah, 0x02     ; BIOS read sector function
  mov al, dh       ; Read DH sectors
  mov ch, 0        ; Cylinder 0
  mov dh, 0        ; Head 0
  mov cl, 2        ; Start reading from second sector
                   ; (i.e. after boot sector)
  int 0x13         ; BIOS interrupt to read the disk
                   ; [es:bx] <- pointer to buffer with data

  jc disk_error    ; Jump if error (i.e. carry flag set)

  pop dx           ; Restore number of sectors we requested
  cmp dh, al       ; If didn't read the right number of sectors...
  jne sector_error ; Error

  popa
  ret              ; Otherwise return

; disk_error prints the disk error message
; and hangs.
disk_error:
  mov bx, DISK_ERROR_MESSAGE
  call print_str
  call print_nl
  mov bx, 0
  mov bh, ah       ; ah = error code
  mov ax, bx
  call print_hex
  jmp $

; sector_error prints the sector error
; message, and then hands
sector_error:
  mov ax, SECTOR_ERROR_MESSAGE
  call print_str
  call print_nl
  jmp $

DISK_ERROR_MESSAGE:   db "Disk read error!", 0
SECTOR_ERROR_MESSAGE: db "Sector read error!", 0

我尝试使用以下各项运行qemu：

> qemu -fda main.asm
> qemu main.asm -boot c
> qemu -drive file=main.bin,index=0,media=disk,format=raw
> qemu -drive file=main.bin,index=0,media=disk,format=raw -boot c

似乎没有任何效果！我在这里做什么错了？

谢谢。

编写引导加载程序和内核-通过QEMU启动自定义引导加载程序时，“固定驱动器未就绪”

0 个答案: