[PATCH 11/12] kexec: allow architectures to override boot mapping

[Pratyush Anand]

On Thu, Apr 28, 2016 at 2:58 PM, Russell King
<rmk+kernel at arm.linux.org.uk> wrote:
> kexec physical addresses are the boot-time view of the system.  For
> certain ARM systems (such as Keystone 2), the boot view of the system
> does not match the kernel's view of the system: the boot view uses a
> special alias in the lower 4GB of the physical address space.
>
> To cater for these kinds of setups, we need to translate between the
> boot view physical addresses and the normal kernel view physical
> addresses.  This patch extracts the current transation points into
> linux/kexec.h, and allows an architecture to override the functions.
>
> Due to the translations required, we unfortunately end up with six
> translation functions, which are reduced down to four that the
> architecture can override.
>
> Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>

I must be missing something when I am thinking that, had we passed
arch_phys_to_idmap_offset to user space, this patch would not have
been needed, and things would have been more simpler. Please help me
to understand why passing arch_phys_to_idmap_offset to user space
would not be a good idea.

~Pratyush