Porting U-Boot's UEFI Payload to coreboot

[Simon Glass]

Hi Ahamed,

On Sat, 12 Mar 2022 at 08:23, Ahamed Husni <ahamedhusni73 at gmail.com> wrote:
>
> Hello,
>
> Sorry for the delay. Thank you for the replies.
>
> On Tue, Mar 8, 2022 at 9:39 PM Simon Glass <sjg at chromium.org> wrote:
> >
> > Hi,
> >
> > On Tue, 8 Mar 2022 at 06:57, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
> > >
> > > On 3/8/22 13:59, Ahamed Husni wrote:
> > > > Hi everyone,
> > > >
> > > > I am trying to work on a project to port the U-Boot UEFI code to coreboot
> > > > as a payload.
> > > > I haven't worked with UEFI before except running a basic EFI payload in a
> > > > coreboot/u-boot environment. (Serial output:
> > > > https://gist.github.com/drac98/6166d29f6c3a2baf2f4e791925ea98d3)
> > > >
> > > > I would like to know how UEFI is implemented in U-Boot. Is UEFI integrated
> > > > into u-boot or is it implemented like a payload?
> > >
> > > Hello Ahamed,
> > >
> > > the UEFI API implementation is an integral part of U-Boot.
> > >
> > > >
> > > > Where is the UEFI source code? Is it the following files in the tree
> > > > https://source.denx.de/u-boot/custodians/u-boot-efi
> > > > lib/
> > > > |__ efi/
> > > > |__ efi_driver/
> > > > |__ efi_loader/
> > >
> > > U-Boot can both be run on top of UEFI. This is the code you find in
> > > /lib/efi/. Furthermore UEFI can run as a firmware providing the UEFI
> > > API. This is what you find in /lib/efi_loader/ and /lib/efi_driver/.
> Then I should look at the lib/efi_loader/ and lib/efi_driver/ I guess. Thank you!
>
> > >
> > > You can build U-Boot as payload for coreboot which offers the UEFI API
> > > implementation. See configs/coreboot64_defconfig.
> > >
> > > U-Boot runs ARM and RISC-V Linux successfully via UEFI.
> > >
> > > What architecture are you looking at?
> I'll be mostly working with a x86_64 QEMU target.
> I am proposing this project for the GSoC this year.
> So the architecture could change after discussions.
>
> > >
> > > Simon (on CC) has been working on U-Boot on UEFI and Coreboot while I
> > > have concentrated on the UEFI API implementation in U-Boot.
> @Simon can I CC you to the discussion in coreboot?

Yes that is OK.

>
> >
> > Yes you can use U-Boot as a coreboot payload - this is now running in
> > CI so we make sure it works on each release. I plan to add more test
> > cases to it but have been waiting to see if coreboot can add something
> > similar to its CI.
>
> I used U-Boot (v2019.4) as a coreboot payload to run my hello world EFI payload and it
> worked.
>
> I also tried different combinations of the applications,
> | Arch | U-Boot | EFI | Status |
> |--------|---------|--------|-------------|
> | 32bit | 32bit | 32bit | Success |
> | 64bit | 32bit | 32bit | Success |
> | 64bit | 64bit | 64bit | Fails and reboot |
> | 64bit | 64bit | 32bit | Fails and returns back to shell printing the error code |
> | 64bit | 32bit | 64bit | Fails and returns back to shell printing the error code |
>
> The last two fail because the EFI does not support booting a 64-bit application from a 32-bit EFI (or vice versa) as mentioned in the u-boot docs. Is this something in the UEFI specification?

Yes.

+Ilias Apalodimas might comment on that too.

>
> The third one fails because 64-bit EFI is not supported yet.

It is supported now but there are some problems and it needs some
work. You are welcome to look at it and I can help.

+Christian Melki was testing that

>
> Is there a way to run 64-bit EFI with something like the 32-bit SPL binary used to boot 64-bit u-boot in coreboot(32-bit)?
> Ex: can we boot a 64bit Windows/Linux with 32-bit EFI? It seems linux can work with 32bit EFI from this thread.

It sounds like you found the coreboot64 build which uses SPL to switch
to 64bit, then runs 64-bit U-Boot.

But if I understand correctly, your question is more for Linux and
Windows I think, so I would check there.


>
> Best Regards,
> Husni Faiz.
>
> >
> > +Stefan Reinauer as we have been talking about this
> >
> > It seems better to go that way than trying to duplicate efforts. We
> > have a program now to move UEFI to use driver model properly, for
> > example.
> >
> > Regards,
> > Simon