[U-Boot] [PATCH 0/9] EFI payload / application support

[Leif Lindholm]

On Tue, Dec 22, 2015 at 02:57:47PM +0100, Alexander Graf wrote:
> This is my Christmas present for my openSUSE friends :).
> 
> U-Boot is a great project for embedded devices. However, convincing
> everyone involved that only for "a few oddball ARM devices" we need to
> support different configuration formats from grub2 when all other platforms
> (PPC, System Z, x86) are standardized on a single format is a nightmare.
> 
> So we started to explore alternatives. At first, people tried to get
> grub2 running using the u-boot api interface. However, FWIW that one
> doesn't support relocations, so you need to know where to link grub2 to
> at compile time. It also seems to be broken more often than not. And on
> top of it all, it's a one-off interface, so yet another thing to maintain.
> 
> That led to a nifty idea. What if we can just implement the EFI application
> protocol on top of U-Boot? Then we could compile a single grub2 binary for
> uEFI based systems and U-Boot based systems and as soon as that one's loaded,
> everything looks and feels (almost) the same.
> 
> This patch set is the result of pursuing this endeavor.

Thanks, this is a very cool thing.
I meant to reply sooner, but Christmas got in the way.

>   - I am successfully able to run grub2 and Linux EFI binaries with this code.
>   - When enabled, the resulting U-Boot binary only grows by ~10kb,
>     so it's very light weight.
>   - It works on 32bit ARM and AArch64. 
>   - All storage devices are directly accessible
>   - No runtime services (all calls return unimplemented)

Yeah, this is a bit of a pain point. The time services, virtual memory
services and reset being the key ones.

>   - No EFI variables

This would obviously (from my point of view) be desirable, but at
least initially, we can do most things without persistent variables.

> Of course, there are still a few things one could do on top:
> 
>   - Implement removable media booting (search for /efi/boot/boota{a64,rm}.efi)

Yeah, that would be top of my wishlist.

>   - Improve disk media detection (don't scan, use what information we have)
>   - Add EFI variable support using NVRAM
>   - Add GFX support

GFX support was actually never implemented for U-Boot GRUB, so from
this p.o.v. it is not a shortcoming over the existing impementation.

>   - Make EFI Shell work ;)

    - Network device support.

I also spotted a couple of minor things while playing around (things
like image exit being missing), but these will be easy to flush out.


I'll leave reviewing of the u-boot side of things to people who know
the codebase better, and restrict myself to commenting on the
UEFIness.

/
    Leif

> But so far, I'm very happy with the state of the patches. They completely
> eliminate potential arguments against U-Boot internally and give users the
> chance to run with the same level of comfort on all firmware types.
> 
> 
> Alex
> 
> Alexander Graf (9):
>   disk/part.c: Expose a list of available block drivers
>   include/efi_api.h: Add more detailed API definitions
>   efi_loader: Add PE image loader
>   efi_loader: Add boot time services
>   efi_loader: Add console interface
>   efi_loader: Add runtime services
>   efi_loader: Add disk interfaces
>   efi_loader: Add "bootefi" command
>   efi_loader: hook up in build environment
> 
>  arch/arm/cpu/armv8/u-boot.lds     |   8 +
>  arch/arm/cpu/u-boot.lds           |  13 +
>  arch/arm/lib/sections.c           |   2 +
>  common/Makefile                   |   1 +
>  common/cmd_bootefi.c              | 168 ++++++++
>  disk/part.c                       |  25 ++
>  include/efi_api.h                 | 197 +++++++--
>  include/efi_loader.h              |  87 ++++
>  include/part.h                    |   2 +
>  include/pe.h                      | 277 +++++++++++++
>  lib/Kconfig                       |   1 +
>  lib/Makefile                      |   1 +
>  lib/efi_loader/Kconfig            |   8 +
>  lib/efi_loader/Makefile           |  11 +
>  lib/efi_loader/efi_boottime.c     | 838 ++++++++++++++++++++++++++++++++++++++
>  lib/efi_loader/efi_console.c      | 371 +++++++++++++++++
>  lib/efi_loader/efi_disk.c         | 227 +++++++++++
>  lib/efi_loader/efi_image_loader.c | 203 +++++++++
>  lib/efi_loader/efi_runtime.c      |  59 +++
>  19 files changed, 2462 insertions(+), 37 deletions(-)
>  create mode 100644 common/cmd_bootefi.c
>  create mode 100644 include/efi_loader.h
>  create mode 100644 include/pe.h
>  create mode 100644 lib/efi_loader/Kconfig
>  create mode 100644 lib/efi_loader/Makefile
>  create mode 100644 lib/efi_loader/efi_boottime.c
>  create mode 100644 lib/efi_loader/efi_console.c
>  create mode 100644 lib/efi_loader/efi_disk.c
>  create mode 100644 lib/efi_loader/efi_image_loader.c
>  create mode 100644 lib/efi_loader/efi_runtime.c
> 
> -- 
> 2.1.4
>