The "standard" method for port save and restore is as follows:

when writing to the port:

mov PxShadow,value
mov Px,PxShadow

when saving
push a
push PxShadow

when restoring
pop a
mov Px,a
pop a

It IS possible to read the port SFR, it is something about using "modifying instructions" if you read the description of ANL on PG 20 of the programmers guide and instruction set you will see one example.

Erik