[J-core] Port Idea: Little Kernel

Rob Landley rob at landley.net
Thu Nov 9 19:24:31 EST 2017

On 11/04/2017 05:29 AM, Ken Phillis Jr wrote:
> I know most of the current work is centered around Linux. I believe
> that some users are more interested in a Real Time Operating System
> with a much smaller Code base for expansion. This brings the idea of
> adding a port to the Little Kernel Project [1]. The Little Kernel is
> known to have an overall binary size of about 20KB on ARM based
> platforms. Also, The Little Kernel is used by google for Zircon[2]
> microkernel found in Fuchsia OS[3].

I pointed people here at Fuchsia when it came out:


And I've also repeatedly pointed people at xv6:


Alas, nobody's made time for either yet, I've got my hands full with
toybox and $DAYJOB, and if I did wind up with extra time I'd really need
to add j-core SOC board and j2 -cpu emulation to qemu.

(Qemu commit 143021b26ffe is already making a couple of instructions
sh4a-specific. In theory the technique for adding a j2 target wouldn't
be that different. Right now we just run qemu under an sh4 kernel with
j2 userspace binaries when we want to test in emulation, because then
the only j2 userspace instruction missing is cmpxchg, which means
futexes don't work. I'm aware there's a kernel patch saying futexes need
fixing, but unless Rich gets around to that independently it's behind
adding qemu support on my own todo list.)


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