The current implementation doesn't work for addresses outside of the canonical ranges of 48-bit address: http://en.wikipedia.org/wiki/X86-64#Canonical_form_addresses. Even if we can't print the exact address (may be a hardware limitation) we may be able to at least report <invalid address> rather than just 0 which implies null pointer errors.

To test segfault on 0xDEADbeefFACEfeed.