Andi Kleen wrote:

quoted

I managed to get all this done in head.S before going into C code; is 
that not still possible?  Or is there a later patch to do this.
    

Why write in assembler what you can write in C?
  

This stuff is very basic, and you could consider it as being part of the 
kernel's C runtime model, and therefore can be expected to be available 
everywhere.  In particular, the use of current is so prevalent that you 
really can't call anything without having the PDA set up.

    J