can anyone tell me which function to call to pause the kernel

[walkerlala]

I successfully insert some function into the kernel code and make it 
execute when the kernel start up, but I just can't make the kernel stop 
executing. Are there any functions which can pause the kernel so that I 
prompt the user, and let the user input a command(maybe a comment to 
display the current time. Something like a shell would do) and interact ?
(I had checked the "sys_***" functions in this page:
     http://docs.cs.up.ac.za/programming/asm/derick_tut/syscalls.html
  but just can't find a proper one )