On 7/4/22 15:39, Tom Rini wrote:
On Mon, Jul 04, 2022 at 03:27:26PM +0200, Heinrich Schuchardt wrote:
On 7/4/22 14:51, Peter Robinson wrote:
Hi Peng,
I did a test to do overlay for U-Boot runtime dtb, but after overlay finish, U-Boot DM driver not work properly because the of_node pointer is changed in a device.
So I am thinking whether this is valid to overlay to runtime U-Boot dtb or not. The reason I try this is that I wanna overlay the EFI capsule signature to U-Boot dtb, then capsule update with authentication could work, otherwise I need integrate the signature in dts and rebuild the image. I understand current U-Boot not support overlay U-Boot runtime dtb, just thinking whether this is valid or should we support it.
Applying overlays to the control device-tree is not supported. Allowing console access on a system where you plan to apply authenticated capsules seems unwise from a security viewpoint. So we should not support your scenario.
Note that Peng didn't say "apply an overlay from the console". I had assumed the desire was to see about doing all of this automatically as part of processing the update/etc.
I thought we had something similar already, so that we could start with a "generic" device tree, figure out we're on board X, grab that device tree (as we're a FIT image and had N dtbs), and then switch to that. But right now I only spot the logic for selecting that dtb in SPL and telling full U-Boot to use that tree.
His question was about avoiding rebuilding the image. So he wants to apply an overlay at run-time not at build time to change the key used to check capsule signatures. This should not be allowed.
Best regards
Heinrich