how i can determine utcb loaction in order to make thread

[Jason Philip]

I am very puzzled, I can't seem to find utcb location in
L4Ka::pistachio. One example do this:

L4_ThreadId_t mylocalid = L4_MyLocalId ();
utcb_base = *(L4_Word_t *) &mylocalid;
utcb_base &= ~(L4_UtcbAreaSize (kip) - 1);

where the current thread is initial thread (main), but i try
this it do not work. Can someone suggest proper way to determine 
the utcb location so that I can create a new thread? Please