1

我正在尝试从我的 ISOSYS 引导加载程序为我的 OS32 操作系统加载第二阶段引导加载程序，但我似乎做不到。CF 似乎总是被设置。这是从 CD/DVD 启动的，我使用的是 Debian GNU/Linux 7.6 (Wheezy)

这是 isosys.asm：

;===============================================================
;
;               ISOSYS v1.0 in isosys.asm
;
; Program for booting OS32 and OS32-based systems from CD/DVDs
; using the ElTorito boot standard.
;
; By Omar, 2014
;
; ===============================================================

; set up bios...
bits 16
org 0x7c00

; beginning of sector 1, byte 0:

; jump over functions block
jmp Start

;
; Print()
;      prints a string to standard output
; AL = 0 : terminate
;

Print:
   lodsb            ; grab a byte from SI and place it in AL
   cmp al, 0         ; is AL = 0?
   jc PrintDone         ; yep, we're done so return
   mov ah, 0eh
   int 0x10         ; nope, print the character
   jmp Print         ; loop until no more characters to be printed
PrintDone:
   ret            ; return to wherever we were!

;
; Start()
;      bootloader entry point
;

Start:
   mov si, creditmsg
   call Print         ; print the first message
   mov dh, 1         ; read 1 sector

.ReadSector:
   cli            ; disable interrupts
   push dx            ; push this stack value
   sti            ; re-enable interrupts

   mov ax, 0x1000         ; read sector into address 0x1000
   xor bx, bx         ; read sector into offset 0x0
   mov ah, 0x02         ; read sector function
   mov al, dh         ; read 1 sector
   mov ch, 0x0         ; must be 0x0 to read sector
   mov dh, 0         ; reading head 0
   mov cl, 0x02         ; start reading from sector 2 to load the second stage

   mov [CDDriveNumber], dl      ; store our drive number is variable CDDriveNumber
   cli            ; disable interrupts
   pusha            ; save the stack
   sti            ; enable interrupts

   int 0x13         ; INT 13h
   jc Error         ; handle error because Carry Flag is set

   pop dx            ; Restore DX

.ExecuteSector:
   ; now that our sector was loaded into address 0x1000:0x0, let's execute it!
   jmp 0x1000:0x0         ; jump to execute the sector
;
; Error()
;      handles errors when carry is set
;

Error:
   mov si, errmsg
   call Print         ; print an error message

   cli            ; disable interrupts to prevent problems
   hlt            ; halt the system... :(

; data section

creditmsg db "ISOSYS v1.0 by Omar Mohammad, Init...", 0
errmsg db "Cannot load the second stage. (File not found maybe?)", 0
CDDriveNumber db 0

times 2048 - ($-$$) db 0      ; fill in 2048 bytes with zeroes

; end of sector 1! :D Any more code here would take bytes 2048 and 2049 but we don't    need that...

这是boot.asm，第二阶段：

bits 16
org 0x1000

Main:
   xor bx, bx
   mov ah, 0eh
   mov al, 'A'
   int 0x10

   cli
   hlt

times 2048 - ($-$$) db 0

nasm -f bin isosys.asm -o ISOSYS我用然后编译nasm -f bin boot.asm -o BOOT 然后我做了mkdir iso然后cp ISOSYS iso/然后cp BOOT iso/生成了ISO： genisoimage -no-emul-boot -boot-load-size 4 -eltorito-boot ISOSYS -o boot.iso iso/

我在 VirtualBox 中运行它，但它说的是无法加载第二阶段（可能找不到文件？），这意味着设置了携带标志，但我似乎找不到错误。

有什么帮助吗？帮助将不胜感激！:*

4

1 回答 1

2

您的堆栈处理完全关闭。您将dx（为什么？）推入cli‥<code>sti 块（为什么？），然后pusha不要popa。

在实际将段寄存器设置为您希望加载代码的位置mov es,ax之后，您还缺少一个。mov ax, 0x1000

您无法使用 CHS 功能 (AH=02h) 读取 ISO，您必须使用带有参数块的 LBA 功能 (AH=42h)。举个例子。

于 2014-12-24T02:32:58.503 回答