How does the Death Star gravity work?

As we all know the Death Star is spherical. I don't know if it generates gravity on its own or has a gravity generator, but that's not important. I think we have basically two scenarios:

1. Gravity works the same way as Earth. If you are in the lower hemisphere, you are upside down, but that's normal for you.

   If that's the case, when would the gravity shift? What if you're taking an elevator, would it be same as in the Total Recall remake?

2. Everyone has the same gravity. Same as if you were in one big house.

   Now what if the trench ran in the lower hemisphere. Would the stormtroopers in the turrets be upside down?

I accept any sort of canon.