[U-Boot] [PATCH v3 0/7] efi_loader: non-volatile variables support

AKASHI Takahiro takahiro.akashi at linaro.org
Tue Jun 4 06:52:04 UTC 2019

This patch set is an attempt to implement non-volatile attribute for
UEFI variables. Under the current implementation,
* SetVariable API doesn't recognize non-volatile attribute
* While some variables are defined non-volatile in UEFI specification,
  they are NOT marked as non-volatile in the code.
* env_save() (or "env save" command) allows us to save all the variables
  into persistent storage, but it may cause volatile UEFI variables,
  along with irrelevant U-Boot variables, to be saved unconditionally.

Those observation rationalizes that the implementation of UEFI variables
should be revamped utilizing dedicated storage for them.

This patch set is yet experimental and rough-edged(See known issues below),
but shows how UEFI variables can be split from U-Boot environment.

When StMM services is supported as a backing variables storage, 
efi_get_variable/efi_get_next_variable_name/efi_set_variable() will
be replaced with stub functions to communicate with secure world.

To enable this feature, the following configs must be enabled:

You can also define a non-volatile variable from command interface:
=> setenv -e -nv FOO baa

Known issues/restriction/TODO:
* UEFI spec defines "globally defined variables" with specific
  attributes, but with this patch, we don't check against the user-supplied
  attribute for any variable.
* Only FAT can be enabled for persistent storage for UEFI non-volatile
* The whole area of storage will be saved at every update of one variable.
  It can be optimized.
* An error during saving may cause inconsistency between cache (hash table)
  and the storage.
* Cache is of fixed size and can be quite big for normal usage.
* I still see some Travis CI errors.

Patch#1 to #4 are core part of changes.
Patch#5 to #6 are to change some existing variables' attributes.
Patch#7 is to extend env command for non-volatile variables.

Changes in v3 (Jun 4, 2019)
* remove already-merged patches
* revamp the code again
* introduce CONFIG_EFI_VARIABLE_USE_ENV for this configuration.
  Once another backing storage, i.e. StMM services for secure boot,
  is supported, another option will be added.

Changes in v2 (Apr 24, 2019)
* rebased on efi-2019-07
* revamp the implementation

v1 (Nov 28, 2018)
* initial

AKASHI Takahiro (7):
  env: save UEFI non-volatile variables in dedicated storage
  efi_loader: variable: support non-volatile attribute
  efi_loader: variable: split UEFI variables from U-Boot environment
  efi_loader: load saved non-volatile variables at init
  efi_loader: bootmgr: make BootNext non-volatile
  cmd: efidebug: make some boot variables non-volatile
  cmd: env: add -nv option for UEFI non-volatile variable

 cmd/efidebug.c                    |   3 +
 cmd/nvedit.c                      |   3 +-
 cmd/nvedit_efi.c                  |  15 +-
 env/Kconfig                       |  39 ++++
 env/env.c                         | 155 ++++++++++++-
 env/fat.c                         | 105 +++++++++
 include/asm-generic/global_data.h |   3 +
 include/environment.h             |  31 +++
 lib/efi_loader/Kconfig            |  10 +
 lib/efi_loader/efi_bootmgr.c      |   3 +-
 lib/efi_loader/efi_setup.c        |   6 +
 lib/efi_loader/efi_variable.c     | 354 +++++++++++++++++++++++-------
 12 files changed, 641 insertions(+), 86 deletions(-)


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