Fiasco.OC-UX on MIPS?

[Paul Boddie]

On Thursday 22. August 2019 15.34.05 Paul Boddie wrote:
> On Thursday 22. August 2019 14.15.55 Matthias Lange wrote:
> > 
> > Did you set the correct qemu options in your Makeconf.boot? And you may
> > have to specify the correct platform type because the default afik
> > 'boston', like
> > 
> >   make O=mybuild qemu PT=malta E=hello
> > 
> > Also check the qemu cmdline that it contains "-M malta".
> 
> I set the qemu options on the command line (noted below), but I imagine that
> Makeconf.boot would also be a reasonable place. I tend to forget about all
> these different files after a while.
> 
> In the Fiasco and L4Re "make config" procedures, I did set the platform type
> to Malta, but it seems that you are suggesting also indicating this on the
> command line, too.

Just a quick update: I have since tried running qemu via the Makefile with the 
machine and console output parameters indicated using QEMU_OPTIONS; the 
emulator does start up and run code at the expected bootstrap locations but it 
doesn't seem to produce any output.

make O=mybuild qemu E=hello QEMU_OPTIONS='-nographic -M malta'

I suspect that there is some kind of restarting happening because when using 
the monitor to check the program counter, it showed the bootstrap code start 
address even after being allowed to run for a while. I guess I could 
investigate debugging options in the bootstrap code, especially since I was 
doing that with real hardware last year.

The bootstrap address is, of course, defined in the following file:

src/l4/pkg/bootstrap/server/src/Make.rules

It is set by this definition:

DEFAULT_RELOC_mips32:= 0x802d0000

And it appears to be this address that appears in the qemu monitor.

[...]

> > Qemu is always a good start. It allows very quick development and test
> > cycles. In the end you of course have to test on hardware.
> 
> If I can get it to work, maybe it will be more useful than UX, although I
> did find UX to be fairly useful on my IA32 machine.

I will add that I have been able to build Fiasco to run as a process in my 
MIPS GNU/Linux environment, having hopefully figured out usable linker 
options, modules, and so on. In order to satisfy the kernel, I have provided 
some emulated support for privileged registers and the memory management unit, 
although the latter will need integrating with (or be replaced by) host-level 
memory mapping operations under normal operation.

Currently, I am working through adding the UX functionality as it is needed 
and, with some physical memory having been provided for the kernel (using mmap 
and indicating memory descriptors), I now need to handle signals and jump to 
the appropriate exception handlers, starting off with handling the timer 
interrupt being produced by the irq0 program.

Paul