Arnd Bergmann [off-list ref] writes:

On Wednesday, July 13, 2016 10:36:14 AM CEST Dave Young wrote:

quoted

On 07/12/16 at 03:50pm, Mark Rutland wrote:

quoted

On Tue, Jul 12, 2016 at 04:24:10PM +0200, Arnd Bergmann wrote:

quoted

On Tuesday, July 12, 2016 10:18:11 AM CEST Vivek Goyal wrote:

/proc/devicetree (aka /sys/firmware/devicetree) is a filesystem derived
from the raw DTB (which is exposed at /sys/firmware/fdt).

The blob that was handed to the kernel at boot time is exposed at
/sys/firmware/fdt.

I believe the blob can be read and passed to kexec kernel in kernel code without
the extra fd.

But consider we can kexec to a different kernel and a different initrd so there
will be use cases to pass a total different dtb as well. From my understanding
it is reasonable but yes I think we should think carefully about the design.

Ok, I can see four interesting use cases here:

- Using the dtb that the kernel has saved at boot time. Ideally this should not
  require an additional step of signing it, since the running kernel already
  trusts it.

- using current view of the hardware, flattened into a new dtb.
  This should already be trusted, as it's what we're running now (boot +
  runtime changes)

-- 
Stewart Smith
OPAL Architect, IBM.