assembly - x86汇编(NASM)中双美元符号的含义是什么

Question

表达式是:

times 512-($-$$) db 0

我知道美元符号的含义，但我不知道它加倍时的含义。

双美元符号是什么意思？

Answer 1

当所有其他方法都失败时，请阅读Fine Manual(第3.5节“表达式”):

NASM supports two special tokens in expressions, allowing calculations to involve the current assembly position: the $ and $$ tokens. $ evaluates to the assembly position at the beginning of the line containing the expression; so you can code an infinite loop using JMP $. $$ evaluates to the beginning of the current section; so you can tell how far into the section you are by using ($−$$).

因此，您问题中的示例仅将当前部分填充为零(大小为512)。