[U-Boot] [PATCH v2 14/21] efi_loader: efi variable support

[Simon Glass]

Hi Rob,

On 10 September 2017 at 05:21, Rob Clark <robdclark at gmail.com> wrote:
> Add EFI variable support, mapping to u-boot environment variables.
> Variables are pretty important for setting up boot order, among other
> things.  If the board supports saveenv, then it will be called in
> ExitBootServices() to persist variables set by the efi payload.  (For
> example, fallback.efi configuring BootOrder and BootXXXX load-option
> variables.)
>
> Variables are *not* currently exposed at runtime, post ExitBootServices.
> On boards without a dedicated device for storage, which the loaded OS
> is not trying to also use, this is rather tricky.  One idea, at least
> for boards that can persist RAM across reboot, is to keep a "journal"
> of modified variables in RAM, and then turn halt into a reboot into
> u-boot, plus store variables, plus halt.  Whatever the solution, it
> likely involves some per-board support.
>
> Mapping between EFI variables and u-boot variables:
>
>   efi_$guid_$varname = {attributes}(type)value
>
> For example:
>
>   efi_8be4df61-93ca-11d2-aa0d-00e098032b8c_OsIndicationsSupported=
>      "{ro,boot,run}(blob)0000000000000000"
>   efi_8be4df61-93ca-11d2-aa0d-00e098032b8c_BootOrder=
>      "(blob)00010000"
>
> The attributes are a comma separated list of these possible
> attributes:
>
>   + ro   - read-only
>   + boot - boot-services access
>   + run  - runtime access
>
> NOTE: with current implementation, no variables are available after
> ExitBootServices, and all are persisted (if possible).
>
> If not specified, the attributes default to "{boot}".
>
> The required type is one of:
>
>   + utf8 - raw utf8 string
>   + blob - arbitrary length hex string
>
> Signed-off-by: Rob Clark <robdclark at gmail.com>
> ---
>  cmd/bootefi.c                 |   4 +
>  include/efi.h                 |  19 +++
>  include/efi_loader.h          |  10 ++
>  lib/efi_loader/Makefile       |   2 +-
>  lib/efi_loader/efi_boottime.c |   6 +
>  lib/efi_loader/efi_runtime.c  |  17 ++-
>  lib/efi_loader/efi_variable.c | 335 ++++++++++++++++++++++++++++++++++++++++++
>  7 files changed, 388 insertions(+), 5 deletions(-)
>  create mode 100644 lib/efi_loader/efi_variable.c

What does hex2mem() do? Please add a comment

This code looks fine but we need a simple way to test it. I think
Herinrich is working on a single hello world test. That could be
enhanced to set and read variables.