question about roottask

 Hi, All
         I am reading something about the L4. And puzzle about the roottask(rootserver?).

         In system start, init_root_servers() will create sigma0,sigma1 and rootserver through funtion create_root_server().
 
         I think the rootserver must do something,such as load elf. So that the user program such as pingpong can be loaded and run. But where's the implement. I mean in create_root_server(), i didn't find the source code to load elf.

        what's more, Why the  rootserver is not created through Thread_Control()? 

        Thanks!
        Bob