linux.conf.au, January 2003
      PRINCIPLES: System Calls & Traps

arch/<arch>/kernel/entry.S
Hard-coded table of functions

Functions called from here must be declared "asmlinkage", eg.
asmlinkage long sys_time(int *tloc)
{

Negative return sets errno, eg "return -ENOENT;"

Traps are similar to asynchronous system calls
eg. page fault, segmentation fault