This improves page sharing. Permissions are retained during sharing,
and we should now be able to share multiple pages. Additionally, this
lays the groundwork for mutable sharing.
Signed-off-by: Sean Cross <sean@xobs.io>
This lays groundwork to support lending pages from one process to
another, and to restore permissions when pages are handed back.
Signed-off-by: Sean Cross <sean@xobs.io>