Question

我正在逐步介绍如何从stratch构建操作系统。如果有人问，我可以发布pdf。所以，我有这个“disk_load”调用，它没有任何明显的原因。我已多次检查每个参数，但它不起作用。

以下是代码

test.asm

; Read some sectors from the boot disk using our disk_read function
[org 0x7c00]
mov [BOOT_DRIVE],dl; BIOS stores our boot drive in DL , so it ’s
                    ; best to remember this for later.
mov bp , 0x8000     ; Here we set our stack safely out of the
mov sp , bp         ; way , at 0 x8000

mov bx , 0x9000     ; Load 5 sectors to 0 x0000 (ES ):0 x9000 (BX)
mov dh , 5          ; from the boot disk.
mov dl , [BOOT_DRIVE]
call disk_load

mov dx , [0x9000]   ; Print out the first loaded word , which
call print_hex      ; we expect to be 0xdada , stored
                    ; at address 0 x9000
mov dx , [0x9000 + 512] ; Also , print the first word from the
call print_hex      ; 2nd loaded sector : should be 0 xface
jmp $

%include "print_string.asm" ; Re - use our print_string function
%include "print_hex.asm" ; Re - use our print_hex function
%include "disk_load.asm"
; Include our new disk_load function

; Global variables
BOOT_DRIVE: db 0

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

; We know that BIOS will load only the first 512- byte sector from the disk ,
; so if we purposely add a few more sectors to our code by repeating some
; familiar numbers , we can prove to ourselfs that we actually loaded those
; additional two sectors from the disk we booted from.
times 256 dw 0xdada
times 256 dw 0xface

disk_load.asm

                ; load DH sectors to ES:BX from drive DL
disk_load:
push dx         ; Store DX on stack so later we can recall
                ; how many sectors were request to be read ,
                ; even if it is altered in the meantime
mov ah , 0x02   ; BIOS read sector function
mov al , dh     ; Read DH sectors
mov ch , 0x00   ; Select cylinder 0
mov dh , 0x00   ; Select head 0
mov cl , 0x02   ; Start reading from second sector ( i.e.
                ; after the boot sector )
mov dl, 0x80
int 0x13        ; BIOS interrupt
jc disk_error   ; Jump if error ( i.e. carry flag set )
pop dx          ; Restore DX from the stack
cmp dh , al     ; if AL ( sectors read ) != DH ( sectors expected )
jne disk_error  ; display error message
ret

disk_error:
mov bx,DISK_ERROR_MSG
call print_string
mov dl, ah
call print_hex
jmp $


; Variables
DISK_ERROR_MSG db "Disk read error: ", 0

我收到错误消息 Disk read error: 0x000C 我知道的意思是Media type not found (floppy)

由于print_string和print_hex做得很好，我不会发布它们。

我已经浏览了每一段代码，一切似乎都没问题。

Answer 1

我发现了错误。我试图从磁盘加载5个扇区，但只有3个扇区。

Int 13h不适用于QEMU。程序崩溃了

1 个答案: