[Solved] GDT doesn't work

[leyley]

And another thing, can I use VirtualBox to debug my program? I want to know the contents of registers.

Yep, definitely RTFM. Here's the link (1st google result for keywords "virtualbox debugger"): http://www.virtualbox.org/manual/ch12.html#idp6899568

Thank you very much, bu debugging I can see my GDT information. It's a jump problem.
I decided to rewrite(redesign) the whole program(RTFM before ) cause ext2 reading needs too many codes:-(.