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.
Note: 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.
Usage: To enable this feature, the following configs must be enabled: CONFIG_ENV_IS_IN_FAT CONFIG_ENV_FAT_INTERFACE CONFIG_ENV_EFI_FAT_DEVICE_AND_PART CONFIG_ENV_EFI_FAT_FILE
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 variables. * 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(-)