[J-core] Port Idea: Little Kernel

[Rob Landley]

Sorry for the delay, a week into travel I usually have a sick day. Takes
my system that long to notice something's awry...

On 11/11/2017 08:49 PM, Cedric BAIL wrote:
> On Sat, Nov 11, 2017 at 5:15 PM, Rob Landley <rob at landley.net> wrote:
>> For the moment I'm using an sh4 kernel with an sh2 userspace (both from
>> my mkroot project), which is a problem because if -cpu j2 excludes sh4
>> instructions, that kernel won't run.
> 
> Indeed, it doesn't :-) Kind of expected actually, but I would prefer a
> positiv test. Also for the moment I have choosen -cpu jcore and not
> j2. The reason is that the latest discussion we had here, seems to
> indicate to me that :
> - j1 -> j2 with mul microcoded
> - j3 -> j2 + mmu
> 
> So none of them will really have a different cpu from qemu point of
> view. Maybe a j32 would make sense, if new instruction would only
> happear with the j64 (Not just 64bits mode, but SIMD and FPU one too).

Ooh, that's a good naming scheme. Now we've actually started speccing
the next round of design work, Jeff's expressed reluctance to call the
next version j3 because he doesn't want to aggro Renesas' trademark lawyers.

We already planned to do j64, and we could even say the nommu version is
"j32n" :)

>> Rich said he had a way to run fdpic binaries in qemu-sh4 (application
>> mode), but when I tried it justnow it said invalid elf image for this
>> architecture. Possibly I have a stale qemu binary on my netbook, I
>> should rebuild and see what that does. (More likely last time I built
>> static pie instead of fdpic...)
> 
> I haven't played with the application mode yet. I guess would be also
> an option for moving forward my qemu port. That will be easier to get
> going with as I already have a toolchain.

I just downloaded your qemu fork, I'll try to poke at it today.

>> I can try to whip up some qemu test images, but don't have them ready
>> offhand. (In japan, can't go digging through usb backups from here. :)
> 
> :-)

Haven't done this yet, I should pull out my turtle board and make sure
stuff runs on it before posting it...

Rob