[PATCH 06/12] ARM: kexec: advertise location of bootable RAM

[linux@arm.linux.org.uk (Russell King - ARM Linux)]

On Fri, Apr 29, 2016 at 08:26:00PM +0530, Pratyush Anand wrote:
> Hi Russell,
> 
> On Thu, Apr 28, 2016 at 2:58 PM, Russell King
> <rmk+kernel@arm.linux.org.uk> wrote:
> > Advertise the location of bootable RAM to kexec-tools.  kexec needs to
> > know where it can place the kernel in RAM, and so be executable when
> > the system needs to jump into it.
> >
> > Advertise these areas in /proc/iomem with a "System RAM (boot alias)"
> > tag.
> >
> > Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
> 
> Can you please also share git tree path of corresponding kexec-tools changes?
> 
> Could it be a better idea (if things in user space become simpler)
> that in stead of patch 5 and 6, we pass arch_phys_to_idmap_offset to
> user space, and then user space manipulates existing "Crash kernel"
> and "System RAM" resources.

Given that it's only _one_ platform right now, I don't think that
additional complexity is worth it.  It means that we have to invent
some API to do it, and I don't see why userspace should even care
about having the delta exported - especially when the conversion
may not be as trivial.

The method I've implemented here keeps things completely independent
of whatever conversion between boot and running physical addresses
may be present on the kernel side as far as userspace is concerned.

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