Provided by: systemtap-doc_3.1-3ubuntu0.1_all 

NAME
function::returnval - Possible return value of probed function
SYNOPSIS
returnval:long()
ARGUMENTS
None
DESCRIPTION
Return the value of the register in which function values are typically returned. Can be used in probes where $return isn't available. This is only a guess of the actual return value and can be totally wrong. Normally only used in dwarfless probes.
SEE ALSO
tapset::errno(3stap)