组装-字符串长度

Question

此代码将打印str？据我所知，len应该定义为$-len

section .data
str: db 'I am a program',0ah,0
len: dd len-str
section .text
global _start
_start:
mov edx,[len]
mov ecx,str
mov ebx,1
mov eax,4
int 0x80