[PATCH] kexec:arm: support zImage with appended device tree

[Hoeun Ryu]

On Mon, 2017-06-26 at 10:14 +0100, Russell King wrote:
> On Fri, Jun 23, 2017 at 05:55:38PM +0900, Hoeun Ryu wrote:
> > 
> > Arm linux supports zImage with appended dtb
> > (CONFIG_ARM_APPENDED_DTB) and
> > the concatenated image is generated like `cat zImage dtb >
> > zImage_w_dtb`.
> We support that only for the purpose of allowing old boot loaders
> that
> are not DT aware to load kernels that require DT.  If it weren't for
> that, we wouldn't have it.
> 
> I don't see why we should propagate this hack to other systems such
> as
> kexec, especially when they have native DT support.
> 

We have some cases when we would like to use different dtb from the
running system when using kexec and I think that's why kexec-tools
supports --dtb command line option.

For example, I have the second kernel for the crash dump with different
kernel configuration and the different dtb from the running system. I'd
like to exclude some nodes/properties from dtb like memory reservations
or unnecessary devices to keep the second kernel/dtb minimal.

The concatenated zImage for arm has a benefit (whether it's intended or
not) to make it possible for users to merge multiple boot images into a
simple single file.
What I'd like to do is just to support the concatenated zImage so that
users can use --load(-panic) zImage_with_dtb_from_the_running_system
instead of --load(-panic) zImage --dtb
different_dtb_from_the_running_system.

Thank you for the review.