This is spelled out in the Schengen Borders Code in some detail. If I recall correctly:
A resident (as opposed to a citizen) of a EU country may enter via another Schengen border without a passport, but only if they have an onward itinerary that takes them to their country of residence. You can’t fly to Germany and then drive to Portugal.
To enter Portugal directly, no you do not need a passport, a valid residence permit is sufficient. Which makes sense. A passport was originally meant as a “right to travel, please let this person pass”, hence all the flowery language on the second page or whatever. Entering the country of your residence isn’t traveling, it’s going home. 
I did happen to look at this latter question quite specifically. I cannot quote chapter and verse ATM but I was really curious about it and I do recall this part.
So if your country revokes your passport, and you can get someone to let you on a plane or a boat and get yourself to Portugal, they’ll let you in. Things being what they are, you’re likely to get questioned or something like that, but you have legal standing.
(Whether they renew your residency at expiration because you no longer have a passport to present is another matter. I have done no research into this. However, you might also play hell with getting that police report… )
I posted a tangentially-related detailed discussion of all this here (it relates to stamps not the actual passport but it is related):
SBC is an interesting read, if you’re into that sort of thing.