Thank you very much for replying.

I actually notice that there are many static functions in that file. However, some of them show up in symbol table, the rest do not. So  what you are saying is that there is no connection between being a static function and showing up in kernel symbol table. Then what causes the difference appearing in symbol table or not? In other word, if i add a new static function and like it in kallsyms, what should I do?

Thanks,
Ji