binman replace broken? (was: Re: [PATCH 0/2] RFC: add fdt_add_pubkey tool)

[Simon Glass]

Hi Jan,

On Wed, 10 Nov 2021 at 13:49, Jan Kiszka <jan.kiszka at siemens.com> wrote:
>
> On 10.11.21 08:20, Jan Kiszka wrote:
> > On 10.11.21 07:55, Jan Kiszka wrote:
> >> On 10.11.21 01:58, Simon Glass wrote:
> >>> Hi,
> >>>
> >>> On Tue, 9 Nov 2021 at 02:17, Jan Kiszka <jan.kiszka at siemens.com> wrote:
> >>>>
> >>>> On 08.11.21 16:28, Roman Kopytin wrote:
> >>>>> In order to reduce the coupling between building the kernel and
> >>>>> U-Boot, I'd like a tool that can add a public key to U-Boot's dtb
> >>>>> without simultaneously signing a FIT image. That tool doesn't seem to
> >>>>> exist, so I stole the necessary pieces from mkimage et al and put it
> >>>>> in a single .c file.
> >>>>>
> >>>>> I'm still working on the details of my proposed "require just k out
> >>>>> these n required keys" and how it should be implemented, but it will
> >>>>> probably involve teaching this tool a bunch of new options. These
> >>>>> patches are not necessarily ready for inclusion (unless someone else
> >>>>> finds fdt_add_pubkey useful as is), but I thought I might as well send
> >>>>> it out for early comments.
> >>>>
> >>>> I'd also like to see the usage of this hooked into the build process.
> >>>>
> >>>> And to my understanding of [1], that approach will provide a feature
> >>>> that permits hooking with the build but would expect the key as dtsi
> >>>> fragment. Can we consolidate the approaches?
> >>>>
> >>>> My current vision of a user interface would be a Kconfig option that
> >>>> takes a list of key files to be injected. Maybe make that three lists,
> >>>> one for "required=image", one for "required=conf", and one for optional
> >>>> keys (if that has a use case in practice, no idea).
> >>>
> >>> Also please take a look at binman which is designed to handle create
> >>> (or later updating from Yocto) the devicetree or firmware image.
> >>>
> >>
> >> Yes, binman is another problem area, but not for the public key
> >> injection, rather for permitting to sign fit images that are described
> >> for binman (rather than for mkimage). I'm currently back to dd for
> >> signing the U-Boot container in
> >> arch/arm/dts/k3-am65-iot2050-boot-image.dtsi, or I would have to split
> >> that FIT image description from that file - both not optimal.
> >
> > OK, this can already be optimized with "binman replace" - once I
> > understood where fdtmap can go and where not. Why no support for using
> > map files?
> >
>
> Well, too quick: "binman replace" writes everything into a temporary
> directory, including the updated image - and then deletes this directory
> on exit. So the original image will not be updated, and the update is lost.
>
> I tried to quickly fix it by adding a rename before FinaliseOutputDir,
> but it feels like I'm working against the design of the internal
> interfaces here.

If you want to see how things work, check out ftest.py which has all
the tests. If there is a test for it, it probably works. If not, it
might not.

Regards,
SImon