The changes I just committed to libkvm require that you update your
   kernel, ps(1), and w(1) at roughly the same time.  If you run an old
   ps(1) or w(1) on a new kernel, it's likely to crash the machine, as
   addresses in /dev/mem are different now, and not validated.

Well, okay, they won't crash your machine any more, but they'll be a
lot more informative if you recompile them.  B-)