6. Indirect Access to Stack Values

• To reference operands on the stack, remember that the values pointed to by the EBP (Base Pointer) and ESP registers are relative to the SS (Stack Segment) register.

• The EBP register is often used to point to the base of a frame of reference (a stack frame) within the stack.

• This example shows how you can access values on the stack using indirect memory operands with 16-bit BP as the base register.

          push    bp              ; Save current value of BP
          mov     bp, sp          ; Set stack frame
          push    ax              ; Push first;  SP = BP - 2
          push    bx              ; Push second; SP = BP - 4
          push    cx              ; Push third;  SP = BP - 6
          .
          .
          .
          mov     ax, [bp-6]      ; Put third word in AX
          mov     bx, [bp-4]      ; Put second word in BX
          mov     cx, [bp-2]      ; Put first word in CX
          .
          .
          .
          add     sp, 6           ; Restore stack pointer
                                  ;   (two bytes per push)
          pop     bp              ; Restore BP