GSOC 2018 ARM Cortex Processor

[Warner Losh]

There's not currently any other FreeBSD port that works on a system without
a MMU. The buffer cache assumes that we can fault in pages as needed based
on virtual address access. The TEXT sharing between programs assumes we can
map the same page into multiple processes. The shared libraries we have
assume something similar, and in some cases copy on write on top of that
(though that's no different from a HW perspective than these first few
cases).

So, if you're willing to live without these features, or find some other
way to accomplish the same sorts of things, a cortex M/R port would be
tricky. Also, FreeBSD's kernel size may present some obstacles. We're
optimized for a rich memory environment, so we trade extra copies of code
to speed up execution of code, which matches the x86 market, as well as the
high-end of embedded quite well.

If you are looking for a BSD to port to these processors, you might
consider looking at what www.retrobsd.org has done with their 2.11BSD port
to the MIPS processor in the PIC32 core with the MIPS M4K architecture. It
runs in as little as 128k of RAM, while FreeBSD these days needs at least
128MB of RAM without careful tuning...

Warner

On Tue, Mar 13, 2018 at 12:07 AM, Michael Zhilin <mizhka at gmail.com> wrote:

> Hi,
>
> Disclaimer: I'm neither ARM expect nor GSoC person.
>
> I may be wrong, but FreeBSD (or Linux, doesn't matter) requires MMU which
> is my tossing in Cortex M/R family of ARM processors. So it's technically
> difficult/impossible to port it on non-MMU processor.
>
> Added freebsd-arm@ for wide audience.
>
> Thank you!
>
>
>
> On Tue, Mar 13, 2018 at 1:12 PM, Vishal Gupta <vishalgupta7972 at gmail.com>
> wrote:
>
> > Hi,
> > I am interested in working on the project to port FreeBSD to ARM Cortex M
> > or R series microprocessor. Some queries related to the project are :-
> > 1) What are the expected deliverable for the project.
> > 2) Where to put my draft proposal for review so that it can be improved.
> >
> > An early reply is awaited.
> >
> > Thanks and regards,
> > Vishal Gupta
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> >
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