設置堆棧段並在裝配中偏移

Question

我設置4k堆棧空間是從引導加載程序的末尾開始的。 之后，我讀取了16個扇區（= 8k）的代碼，地址為0x2000：0x0000。 這是我的操作系統的內核。 我分支到它。

問題是，如何設置從內核末尾開始的8k堆棧空間？

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

嘗試

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

這應該將堆棧設置為您想要的位置。 通常不需要其他設置。

請注意，您不需要為此禁用中斷，因為x86 CPU在將新的段選擇器加載到ss后隱式禁用了一條指令的中斷。