probe point "process(PATH).function(*).return" not ready yet?

[maliubiao]

Code:
probe process("../build/lpg").function("*").reutnr {
printf("%s\n", probefunc());
}
Result:
semantic error: while resolving probe point: identifier 'process' at
hello.stp:8:7
        source: probe process("../build/lpg").function("*").return {
                      ^

semantic error: process return probes not available [man error::inode-uprobes]
Pass 2: analysis failed.  [man error::pass2]

This probe point is in the systemtap language reference, what's wrong?
thanks   .