Re: Relocating an amigappc kernel by the boot loader

[Ignatios Souvatzis <is%netbsd.org@localhost>]

On Wed, Feb 17, 2010 at 10:10:30AM +0100, Frank Wille wrote:

> Agreed. But some of those commands make my installation drop into ddb now
> (I have to check if it's a real panic or a Debugger() call). That's not
> nice to watch.

That's a serious bug, because *any* user of kvm could do the same
by careful selection of access patterns. If you can find out where
the crash happens, we could maybe extract a test program that
doesn't rely on a wrongly-linked kernel to expose the bug, for
testing other ppc architectures.

> I can easily extract such a tool out of my boot loader, so we don't have
> to rely on any GPL tools.
 
> I guess the relocation tool should work under NetBSD, not AmigaOS (or
> both?).

Both.

> Maybe we could even check the kernel automatically during multi-
> user boot and relocate it, when its VMA doesn't match the loaded kernel?

I don't like that much. It requires a writable root file system
and a writeable kernel (think file flags!). 

Such stuff should only be done by people who are aware of it. And
not to their working copy of the kernel directly.

Btw - what about a bootblock? I suspect, now that we have a two-stage
loader for Amiga, the first stage could be the same as the m68k first
stage, and only the 2nd stage would know about PPC.

For additional comfort, check for the executable type of the kernel
and switch to ppc if necessary ;-) - but as init and sh would need 
to be of the right type, this is not really first priority - as long
as we don't have an in-kernel m68k emulator.

> Lots. A RAM module in bank 1 will be mapped downwards from 0x?8000000 and
> a module in bank 2 will be mapped upwards from 0x?8000000. The '?' can be
> any of 4, 5, 6, 7, depending on the size of RAM (I think).
> 
> At least all the RAM will always be in a single 256MB segment, so I can
> BAT-map it.

oh.... sort of make sense. We should document that somewhere in
the source tree, to avoid mailing list adventure games by future
amiga(|ppc) archeologists.

Regards,
        -is