loader lszfs command

Hi,

People have been pestering me to update the Forth code to present
a menu of ZFS datasets (*cough* boot environments *cough*).

Would love to, but existing code seems broken.

Can *anybody* produce meaningful output from the following?

http://svnweb.freebsd.org/base?view=revision&revision=241284

All I get on every system I've tried (multiple versions, including HEAD)
produce the following:

 OK lszfs zroot
ZFS: i/o error - all block copies unavailable
operation not permitted

It's really hard for me to start with something that's broken. Can
I get confirmation that this doesn't appear to be working as intended?
If so, I'll go ahead and try to fix it, but need to confirm that I'm ( a )
not
crazy and ( b ) seeing the same thing everybody else is seeing.
-- 
Devin