The creator_file() function is called in the master object each time a
new object is created. The 'filename' of the object is passed as the
sole parameter, and the string that creator_file() returns is set as
the new object's uid. If the AUTO_SETEUID option is enabled at com‐
pile-time of the driver, it is also set as the new object's euid.
One exception: if the AUTO_TRUST_BACKBONE option is enabled at compile-
time of the driver, and creator_file() returns the backbone uid (as
specified by get_bb_uid() in the master object), the object is given
the uid and euid of the object that loaded it.