Theo  wrote:
> You can get the ARM cores to yourself if you want.  It is possible to keep
u-boot
> in memory to provide 'firmware' services that your operating system doesn't
> provide, and there's also TrustZone, although I don't think the Pi
> environment uses that out of the box (I'm less familiar with Pi4).

Can the firmware services alluded to be called by a user logged in
through a "normal" connection? I.e., bypassing normal security and
authentication mechanisms? That's not an issue if the firmware is
removed/overwritten by the loaded operating system, but if u-boot
remains I understand much better the objections raised by open source
advocates.

> If you want to do bare-metal things without U-boot, there's BakingPi:
> https://www.cl.cam.ac.uk/projects/raspberrypi/tutorials/os/
> although that's written for the Pi1 and will need small changes for Pis
> 0/2/3.  I'm not sure it'll work on Pi4.  There are some PRs for supporting
> other Pis (Alex hasn't been able to work on it for a while):
> https://github.com/Chadderz121/bakingpi-www

Thank you for a highly informative reply. I'm not competent to do much
with BakingPi, certainly nothing remotely useful, but it gives insights
which I didn't have before.

bob prohaska

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