Genode / RISC OS hybrid system

I thought it might be better to have this as a separate thread.

I have done a basic bringup of RISC OS and Genode playing nice together. Test platform is iMX8M because Genode already works on it and I ported RISC OS to it. This is what I have done this far:

• Boot RISC OS from genode
• Use Message Unit for inter core communication
• Kernel debug terminal is connected to server/terminal in Genode. Uses Mesage Unit.
• A test rom module (RISC OS ) that provides a couple of commands.
• gencat , one of the commands takes one arg , a Genode path (posix) and returns a directory list.
• Besides just using the Message Unit regisrer I also (not counting Debug Terminal) passes a physical address from RISC OS to Genode. The address points to memory PCI_ram alloced buffer. (right now only used in “gencat”
• Next thing will be a proper filing system. I have been looking on the existing ones and found that lanman has the simpliest implementation. I just need to replace the SMB functions with my protocol.

Graphics is very simple to achive so I will not do that right now. In fact I might use RISC OS for it.. but letting Genodes drivers set it up before i write RISC OS frambuffer address to the gfx chip.There is very little use of having graphics directly in Genode in this scenario.

In the not so near future I plan to have Genode apps (such as up to date web browser) graphics and ui events be redirected to riscos. This will provide a secure app environment, but still behave like a RISC OS app.

Most drivers will be handled by Genode. Genode have a smart little way of using Linux drivers. It requuires some patching , but is way better than writing them from scratch. Genode also have a compatible license for that.

I also plan for a ARM32 emulator ,, but that is just a fantasy right now. I think that it needs to be done by someone who knows a lot about cpu emulation. I don’t.

My Genode work will be GPL and the RISC OS part will stay with the apache license.

I post regular photos and video on Twitter. My twitter id is @QtARM, go check it out if you have something that can do Twitter.

Graphics is very simple to achieve, so I will not do that right now. In fact, I might use RISC OS for it… but letting Genodes drivers set it up before I write RISC OS framebuffer address to the GFX chip

Treating Genode as a fat HAL seems a good idea

I also plan for a ARM32 emulator, but that is just a fantasy right now. I think that it needs to be done by someone who knows a lot about CPU emulation. I don’t.

The real fantasy would be having it also emulate the 26 bit mode CPU to cope with the legacy antique software

My Genode work will be GPL and the RISC OS part will stay with the apache license.

Sensible segmentation.

go check it out if you have something that can do Twitter.

This forum is about as close as I ever get to social media, so I will await updates here.

So .. The year of 2023 is going to be the year of doing this.. get Genode and RISC OS together!

I have started on bringing up Genode on a core that doesn’t support 32bit execution. When that is more or less finished I aim for 32bit emulation.

I will try to write updates on it here and twitter/mastodon.

Running demo scenario, which unfortunately ends in mmu fault in framebuffer. I can’t interact yet due to lack of usb driver.

What’s your Mastodon, Michael?

Mastodon @ mickenx @ mstdn.social Twitter @QtARM .

ARM emulator work started , using the unicorn emulator. Bringing up that kind of software on Genode is a real challenge. There are a lot of memory/cache handling that needs attention. Genode and the kernel I am using , “base-hw” , is a really thin layer above the hardware.

Anyway 32bit ARM BBC BASIC:

http://micken.se/pix/genodebbc_basic.jpg

I presume you’re aiming for effectively a 2nd processor environment – RAM & ROM but no memory-mapped hardware whatsoever, RO-to-Host communication through a magic SWI range?

I aim to have wimp running mostly in genode, which is very difficult to achieve. But I am optimistic. I will not start a complete rom. The emulator only supports 1:1 mmu mappings it seems and that is very incompatible with riscos. . Right now I am thinking of having the cpu emulation in a separate server like task.

But yes , communication from arm code to host will be swi and or memory.

Oh hey.. I just solved EL switching in Genode. Before today I could only start Genode in EL1 since the switch in Genode didn’t work. It probably was that u-boot left me in a unknown cpu state. I added cpu clearing to startup , and with that el switching works.

If by “1:1” you mean you can’t move pages around, then how would task swapping work… byte copying? Eek.

If you mean any one physical page can only be mapped to one logical address, then screen handling aside, what would that adversely affect other than memory hiding (which is related to task swapping)?

I mean: mapping mem 0×4000 will result in 0×4000 virtual , no matter how you do your translation tables. I hope I am wrong about that :-)

That’s not ideal. Can Genode map your real pages underneath the emulator?

VirtualRO → VirtualHost → PhysicalHost

rather than

VirtualRO → PhysicalRO → VirtualHost

Possible.

My blog on genodians.org is now live:

https://genodians.org/mickenx/2023-01-18-genode-and-riscos-continued

<Clicks ❤️ button>

Er, only 9 days and this?
I need a big emoji for gobsmacked with a heavy shovel…

I can’t wait to see what happens in February.

would this work with other processers?

would this work with other processers?

Yes. The soc needs to be supported by Genode.
There are several out there including Pies.
But, I will focus on rk3588 now.

Including Risc-V I notice.

How’s it going, Michael?