It's been a while since my last update. What can I say... summer was nice.
But now, back to business! I've just committed some long overdue patches to the upstream GNU tools:
- Add a device tree blob to the gdb simulator. This lets us describe the gdb sim target to our single kernel image as described in this posting.
- A GCC size optimization. Load 0 into a register via xor.
- Improve function prologue code generation, and a corresponding gdb change.
- Use 6 registers to pass function arguments as [described here].
This gets us to booting the kernel, loading BusyBox, running some shell code and... crashing on the first fork. No problemo. Nothing a small matter of programming can't fix. However, there are some other distractions...
Verilog is lots of fun! It looks like regular programming, but it feels more like building a kinetic sculpture.
There's also the small matter of not having an interrupt controller! So there's some work here to design an interrupt controller, implement it in verilog, simulate it qemu (and possibly the gdb sim), and port the kernel over to using it. This should be interesting...