Booting questions ....

[John Baldwin]

On Friday 05 November 2004 03:34 pm, Willem Jan Withagen wrote:
> John Baldwin wrote:
>
> [about the loader having flat addressspace....]
>
> >>But is it unsegmented? (perhaps I have a wrong idea of a flat address
> >>space)
> >
> > Yes, it is unsegmented.  You can translate physical addresses to virtual
> > addresses using PTOV() and vice versa using VTOP().
>
> I've run accross these calls, just need to figure out how to work them.
>
> >>What I mean with this is that I can iterate from 0xa000 to 0xffffffff
> >> with a "char *p" and do test_bytes( 0xa000, 0xffffffff, 0xff). (assuming
> >> this all has memory)
> >
> > Yes.
>
> Would be nice....
>
> >>Next is then which ranges are valid to test, and then things really start
> >>to get complicated and arch dependant. Which is why I ended up in
> >> machdep.c right after the setting up of the memory ranges.
> >
> > Heh, the above memory mapping is also i386 specific.  Alpha only has a
> > small bit of memory mapped in the loader, same with sparc64, etc.
>
> Ehhhh, again more reasons to put this in the kernel, or something that
> closely resembles a kernel.

Well, part of the problem there is that the early kernel code is all MD 
anyway.  I think your best bet really is to write your own mini-kernel that 
the loader can load to do this, but it will require MD stubs for early 
bootstrapping as well as some kind of API for mapping a page so you can test 
it and then unmap it, which is required for x86 machines with > 4GB of RAM 
for example.

-- 
John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org