Provided by: systemtap-doc_2.3-1ubuntu1.4_all 

NAME
function::user_string_warn - Retrieves string from user space
SYNOPSIS
user_string_warn:string(addr:long)
ARGUMENTS
addr
the user space address to retrieve the string from
DESCRIPTION
Returns the null terminated C string from a given user space memory address. Reports "" on the rare cases
when userspace data is not accessible and warns (but does not abort) about the failure.
SystemTap Tapset Reference March 2016 FUNCTION::USER_STRIN(3stap)