function::probefunc.3stap man page
function::probefunc — Return the probe point's function name, if known
This function returns the name of the function being probed based on the current address, as computed by symname(addr) or usymname(uaddr) depending on probe context (whether the probe is a user probe or a kernel probe).
this function's behaviour differs between SystemTap 2.0 and earlier versions. Prior to 2.0, probefunc obtained the function name from the probe point string as returned by pp, and used the current address as a fallback.
Consider using ppfunc instead.