Re: APUS and IOs question

On Fri, 10 Nov 2006, Benjamin Herrenschmidt wrote:

quoted

My plan for moving APUS to arch/powerpc involves writing a new
bootloader (I'm currently hacking binutils to support AmigaOS binaries)
that builds a proper flattened device tree and calls the kernel, but I'm
not sure where the kernel virtual mapping that allows the kernel to run
from a fixed address should be set up -- if in the bootloader, the
kernel needs to be aware that changing the MMU settings will yield
interesting results, and if in the kernel, we need some platform
specific init code to handle that.

Well, the problem is that you basially have to hack the linear mapping,
thus hitting anything that relies on __pa/__va or operating in real mode
indeed.

How do you do for exception vectors ? Since those have to be either at 0
or at ff* ? You stick branches at 0 to jump to where the kernel
resides ?

IIRC (Roman please correct me if I'm wrong), APUS has them at ff* because the
memory at adress 0 is slower.

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds