arm MACHINE and MACHINE_ARCH issues

[Alan Barrett <apb%cequrux.com@localhost>]

On Sun, 20 Jul 2014, Matt Thomas wrote:
> > - how sysctl hw.machine_arch should be handled
>
> Right now it return the MACHINE_ARCH the executable was built 
> for via an ELF note.

I'd expect sysctl hw.something to report information about the 
hardware that's in use, or perhaps the hardware that the kernel 
was built for.  It seems weird to report information about how the 
currently running executable was built.

Perhaps we need different sysctl nodes to report the kernel's 
idea of MACHINE_ARCH and the userland executable's idea of 
MACHINE_ARCH.

> [lots of information]

Please could you document this somewhere.  Some possible places 
that come to mind are sys/arch/README, sys/arch/*arm*/???, 
distrib/notes/*arm*/install.

--apb (Alan Barrett)