Kernel selection in Lua loader

The Lua loader appears to be using a mechanism other than the
"kernels=..." specification in /boot/loader.conf to slect potential
kernels to load.  I'm not claiming this is "bad" -- just "different."

I noticed because I sometimes build a kernel that ... panics, or some
such thing, so I hve had occasion to make use of kernel.old.  But in the
process of engaging a developer and trying patches, the default behavior
is that kernel.old gets overwritten next time I build a kernel.

So I had taken to copying /boot/*.old to /boot/*.save manually as the
occasion warrants; I modified /boot/loader.conf to include:

kernels="kernel kernel.old kernel.save"

and the Forth loader presented (precisely) those kernels as the
available options for selecting a kernel to load and boot.

Usually, if I manually copy/move kernels around, I also save the kernel
that misbehaved (in case further poking around in its internals may be
warranted); a typical name for such a beast is "kernel.panic" (as I
usually have at most a single such misbehaving kernel around).

Thus, I noticed when I did my smoke-test boot after freshily building:

FreeBSD g1-215.catwhisker.org 12.0-CURRENT FreeBSD 12.0-CURRENT #108  r329703M/329706:1200058: Wed Feb 21 04:04:36 PST 2018     root_at_g1-215.catwhisker.org:/common/S3/obj/usr/src/amd64.amd64/sys/CANARY  amd64

with the Lua loader, I was being offered a choice among 4 kernels
(rather than the expected 3).  Cycling through them (twice; I wanted
to be sure the behavior was reproducible), I noted that the presented
options were:

* default/kernel
* kernel.old
* kernel.save
* kernel.panic

(in that sequence).  I did not attempt to select any of the non-default
options, however. :-)

Nor did I remove the 'kernels="kernel kernel.old kernel.save"'
specificaton from /boot/loader.conf to see what would happen.

Peace,
david
-- 
David H. Wolfskill				david_at_catwhisker.org
Yes, the indictments don't "prove" guilt; that's what trials are for.

See http://www.catwhisker.org/~david/publickey.gpg for my public key.