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Kernel update: device trees and kernel threads

I've spent a lot of time in airports/planes/hotels recently, which is good news for the moxie linux port. It runs about 6.5M instructions, booting up to the point where a couple of kernel threads are created. However, a few context switches later it all comes tumbling down. I didn't have any of my kernel books with me, so I stopped hacking at that point rather than try to guess/decode how some of the internals are supposed to work.

My port is using a device tree to describe the system architecture. This makes it easier to build a single kernel image that can boot on multiple moxie implementations. There's a good paper on this relatively new infrastructure here: If you've been following this project, you may recall that console I/O is implemented differently on the gdb and qemu simulators. For the gdb simulator we use a software interrupt instruction (swi) to escape to the simulator, but the qemu port uses a real simulated serial device. This means they need different console devices in the kernel to print boot messages. The device tree is a nice way to describe differences like this and have a single kernel image to boot in both environments.

Also, as predicted, I actually used moxie gdb's reverse debugging feature to help debug my kernel bring-up. It was really useful a couple of times and has probably saved me the amount of effort required to implement it in the first place already!

The next week is going to be very busy for me, so I don't expect to get much done. We'll see...

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