get_thread_area returns an entry in the current threads Thread Local Storage (TLS) array. The index of the entry corresponds to the value of u_info->entry_number, passed in by the user. If the value is in bounds, get_thread_info copies the corresponding TLS entry into the area pointed to by u_info.
get_thread_area returns 0 on success. Otherwise, it returns -1 and sets errno appropriately.