$LOCKED_PAGE_START is used with $LOCKED_PAGE_END to delineate code that may be locked at image initialization time by the $LOCK_PAGE_INIT macro. The code delineated by these macros must contain complete routines-execution may not fall through either macro, nor may the locked code be branched into or out of. Any attempt to branch into or out of the locked code section or to fall through the macros will be flagged by the compiler with an error.