设置堆栈段并在装配中偏移

Question

我设置4k堆栈空间是从引导加载程序的末尾开始的。 之后，我读取了16个扇区（= 8k）的代码，地址为0x2000：0x0000。 这是我的操作系统的内核。 我分支到它。

问题是，如何设置从内核末尾开始的8k堆栈空间？

bootloader.asm

; bootloaders are always loaded to offset 0x7c00.
; so, define base to 7c00h.
  org 7c00h

; jmp to start function.
  jmp hg._start

; bootloader function.
; set stack and segment registers.
hg._start:
  ; set stack space. (4K)
  mov ax, 07c0h
  add ax, 288 ; (4096+512)/16 bytes per paragraph.
              ; note that this bootloader loads
              ; remaining 8 sectors via int 13h:02.
  mov ss, ax
  mov sp, 4096

  mov ax, 07c0h
  mov ds, ax  ; set data segment to base of the
              ; bootloader. this can get rid of
              ; some memory access errors.

  ; from now on, we had set up segments.
  ; now we can get into real work, loading remaining
  ; 8 sectors with int 13h:02.

  ; load code to 0x2000:0x0000. (0x20000)
  mov bx, 2000h
  mov es, bx
  mov bx, 0

  mov ah, 02 ; int 13h:02 -> bios read function.
  mov al, 16 ; read 8k of code.
  mov ch, 01 ; track to read.
  mov cl, 02 ; sector to read. (from 1 = mbr)
  mov dh, 01 ; head to read.
  mov dl, 80h; drive to read (0=fd0, 1=fd1, 80h=hd0, 81h=hd1)
  int 13h

  times 510-($-$$) db 0
  db 55h
  db 0aah

Answer 1

尝试

mov ax,2000h
mov ss,ax
mov sp,4000h

这应该将堆栈设置为您想要的位置。 通常不需要其他设置。

请注意，您不需要为此禁用中断，因为x86 CPU在将新的段选择器加载到ss后隐式禁用了一条指令的中断。