Capturing User-Level Function Calls/Returns

Hi,
What is the most efficient way to capture occurrence of a function 
call/return of a binary program in userspace?
It seems the answer is Uprobes. 1) Am I right?
But Uprobes use "int" instruction which leads to a switch into kernel 
mode. 2) Wouldn't it be better to avoid this transition?
I'm looking forward to your reply and will be happy to read your 
opinions.
Regards.