Shared mapping

Hi, Is there a way, w.r.t memory contents, to make a process B see what process A sees through shared memory mappings? Suppose Process A has mapped a device file (say F) at address 0xaaaaaaaa in its address space. Is it possible for process B to see the same device file F contents as process A via shared memory mappings? If mapped in process B's address space, would process B continue to to see the old contents if process A were to map a new device file (say N) at the same address 0xaaaaaaaa in its address space or do they have independent mappings? So basically I'm trying to understand if there could be virtual to virtual mappings (e.g. process B mapping process A's memory, so that B sees whatever A sees)? Thanks for your help! -Riya