FreeBSD and Coreboot

Hello everyone,

I'm through enough of my job change that I can start working on FreeBSD
again.  One thing I've had on my list to examine is using FreeBSD with
coreboot, so I wanted to put out a call for anyone who has done work on
this, or knows anything about it.

Here is what I know:

* Coreboot _can_ boot kernels directly, but this requires two things: 1)
you must flash your BIOS every time you update a kernel, 2) the kernel
must be able to work without the usual device initialization that the
BIOS does.

* Coreboot has two significant payload options beyond a kernel: Seabios
and GRUB (supposedly Tianocore EFI is an option, but it apparently
doesn't really work).

* Scrounging the coreboot wiki seems to produce some conflicting
information.  One page claims that the FreeBSD kernel can boot directly
as a coreboot payload; another claims GRUB or Seabios to be the only
options.

* The PC Engines boards evidently use coreboot, and I've heard multiple
reports of them running FreeBSD systems without a problem.  I don't know
whether they use GRUB or Seabios.  (Aside: I'm thinking about ordering
some of these boards for my own use, so I'm generally interested in how
well they function with FreeBSD)


My plan is roughly this:

* Refurbish the GRUB port, get it working again in QEMU (possibly on one
of my machines), also possibly push a patch to GRUB to use the keybufs
mechanism to pass in GELI keys.

* Get coreboot with GRUB/Seabios booting FreeBSD in QEMU

* Possibly create a coreboot port (uncertain how this would work, since
Coreboot has its own extensive config menu)

* Hold my breath and test it out on real hardware (I have a Librem 13 r1
for this purpose)

* Possibly try getting the FreeBSD kernel to work as a coreboot payload.


Here's what I don't know/what would be useful knowledge for me:

* Anyone else who's been experimenting/working on coreboot support, and
what they found

* Any working examples of using Coreboot with FreeBSD

* Down the road, anything about adapting the FreeBSD kernel to work with
a new boot platform (ie. low level details about how to set it up in
memory on a bare-metal system and start execution)