function::user_string — Retrieves string from user space
1) user_string:string(addr:long)
2) user_string:string(addr:long,err_msg:string)
addrthe user space address to retrieve the string from
err_msgthe error message to return when data isn't available
1) Returns the null terminated C string from a given user space memory address. Reports an error on the rare cases when userspace data is not accessible.
2) Returns the null terminated C string from a given user space memory address. Reports the given error message on the rare cases when userspace data is not accessible.