Re: [User-mode-linux-devel] UML/PPC status

[Chris E. <cem...@ch...>]

On Mon, 1 May 2000, Jeff Dike wrote:

[snip]
> > There's one reference to EDX in finish_exec() - what's that one
> > for?
> 
> You need to worry about this one.  Elf binaries take a value in EDI
> (on i386) which is an address of an initialization procedure or
> something.  Linux doesn't use it, so it goes in as zero.  Look
> through asm-ppc/*elf*.h for something similar.

There doesn't seem to be anything similar.  There's a comment
somewhere saying that i386 takes a pointer to a function to call on
exit in EDX, and not mentioning other architectures.

Do you know of a good online reference for Elf things like this?

> >  I've deleted a large chunk of arch/um/kernel/syscall_kern.c for
> > system calls which don't seem to exist on PPC.
> 
> This sucks.

Indeed.  I now have an #ifdef.  I think it'd be useful to define a
symbol like __UM_$(SUBARCH)__ or something similar for this sort of
thing.  At least some of the syscalls there will be i386 only, rather
than just non-ppc (vm86 springs to mind).

> > +#define UM_SP_OFFSET UESP 
> > +#define UM_IP_OFFSET EIP 
>
> These are wrong, and I bet the ppc equivalents you've got are wrong,
> too.

Yes, you're absolutely right...  brain failure on my part.

> I would prefer that you have your Makefile make links to arch/ppc
> files that you're just going to steal whole.  That keeps the patch
> size down, and gives this kernel the benefit of whatever changes are
> made in those files in the future.

I've done that for bitops.c.  The assembler functions are trickier,
as they seem to need quite a bit of the environment from arch/ppc.
I'll look into it.

Chris
-- 
Chris Emerson, obsessed Cambridge juggler
E-mail: cem...@ch...
Web page: http://www.chiark.greenend.org.uk/~cemerson/