Re: FreeBSD and Coreboot

On 2019-05-27 19:14, Warner Losh wrote:
> On Mon, May 27, 2019, 7:18 PM Nathan Whitehorn <nwhitehorn_at_freebsd.org>
> wrote:
>
>>
>> On 2019-05-27 15:50, Eric McCorkle wrote:
>>> On 5/27/19 5:53 PM, Edward Napierala wrote:
>>>> On Mon, 27 May 2019 at 16:14, Eric McCorkle <eric_at_metricspace.net>
>> wrote:
>>>> [..]
>>>>
>>>>> 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.
>>>> Out of curiosity - why the kernel and not loader(8)?
>>>>
>>> If I understand coreboot correctly, loader would have to directly
>>> manipulate devices _without a BIOS_.  That is, it would have to have an
>>> entire device detection/interface layer, which I don't believe is the
>>> case today.
>>>
>>> At least in the EFI case, loader is talking through the system's EFI
>>> implementation, which takes care of all that for you.  BIOS works in a
>>> similar way.  My sense is getting loader to the point where it could be
>>> a coreboot (without Seabios/GRUB/Tianocore) would be quite an
>> undertaking.
>> On IBM PowerNV systems, which also don't provide interfaces to a
>> second-stage loader, we just abandoned loader(8). It's way too much work.
>>
> How do you use tunables and loadable modules?
>
> Warner
>

The firmware on PowerNV has a way to write tunables to the device-tree,
which we rehydrate into something that looks like it came from loader.

We don't usefully support loadable modules at the moment. The firmware
can optionally load exactly one file from the boot filesystem and pass
it to the kernel (for Linux, the initrd). There are a couple of ways to
imagine exploiting this for kernel modules, but all of them are kind of
crummy.
-Nathan