GitLab

libpagemap was storing a virtual pfn in an int, which works on arm64
with 39 bits of virtual address space but fails on x86_64.  Use an
unsigned long instead.

Fixes errors when running procrank on x86_64:
warning: could not read usage for 1

Change-Id: I171c8ee49faa51accf3c1bb69059d549aee04979