Linux does the same, this avoids ifdef or extra includes in ported drivers.
Reviewed by: emaste, hselasky
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D25702
the LinuxKPI for accessing user-space memory in the kernel.
Add functions to hold and wire physical page(s) based on a given range
of user-space virtual addresses.
Add functions to get and put a reference on, wire, hold, mark
accessed, copy and dirty a physical page.
Add new VM related structures and defines as a preparation step for
advancing the memory map capabilities of the LinuxKPI.
Add function to figure out if a virtual address was allocated using
malloc().
Add function to convert a virtual kernel address into its physical
page pointer.
Obtained from: kmacy @
MFC after: 1 week
Sponsored by: Mellanox Technologies
