Since several people are not sure about this, I figured an easily skipped little grammar point can't hurt too much.
Passive past would be something like "Goodbye had been said too many times before [by her]"
In active voice, the subject does something to the object.
In passive voice, the object is affected [by the subject]. (I wanted to write "is done something to" instead of "affected", but that feels ugly - the issue with affected is that it is also an adjective; I really mean the past participle here)
The object becomes the subject, and vice versa. The be auxiliary needs to be present. If be is not here, it ain't passive. If be is here… be can be used in active voice so you can't know for sure, but if there's a "by ..." clause, or if adding one feels natural, that a good hint.
The intent of the passive voice is usually to focus on the object or the action, of de-emphasis the subject, of even to drop it because it's not important, it's redundant or even to create some suspense regarding who performed the action.
(English is a second language to me, though what I wrote completely applies to my first language too)