# In version 4 of this patch set, the implementation is changed to meet # Wolfgang's requirements. # I believe that this is NOT intrusive, and that my approach here is NOT # selfish at all. If Wolfgang doesn't accept this approach, however, # I would like to go for "Plan B" for UEFI variables implementation.
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.
Basic ideas: * Each variable may be labelled with a "context." Variables with different contexts will be loaded/saved in different storages. Currently, we define two contexts:
ENVCTX_UBOOT: U-Boot environment variables ENVCTX_UEFI: UEFI variables
* Each variable may have a third attribute, "variable storage." There are three new flags defined: ('flags' are a bit-wise representation of attributes.)
ENV_FLAGS_VARSTORAGE_VOLATILE: A variable only exists during runtime. ENV_FLAGS_VARSTORAGE_NON_VOLATILE: A variable is persistent, but explicit "load" and "save" command is required. ENV_FLAGS_VARSTORAGE_NON_VOLATILE_AUTOSAVE: A variable is persistent, any change will be written back to storage immediately.
* Following those extensions, new interfaces are introduced: for hashtable, hsearch_r -> hsearch_ext hmatch_r -> hmatch_ext hdelete_r -> hdelete_ext himport_r -> himport_ext hexport_r -> hexport_ext for env, env_save -> env_save_ext env_load -> env_load_ext env_import -> env_import_ext env_export -> env_export_ext They will take one or two additional arguments, context and flags, comparing with the existing corresponding interfaces.
* Even with those changes, existing interfaces will maintain its semantics, as if all the U-Boot environment variables were with UEFI_UBOOT context and VARSTORAGE_NON_VOLATILE attribute. (The only exception is "env_load()." See below.)
* There is one thing visible to users; *Exported* variables now have attribute information, which is appended to variable's name in a format of ":xxx" For example, => printenv arch:san=arm baudrate:san=115200 board:san=qemu-arm ... This information is necessary to preserve attributes across reboot (save/load).
* Each environment storage driver must be modified so as to be aware of contexts. (See flash and fat in my patch set.)
Known issues/restriction/TODO: * Existing interfaces may be marked obsolute or deleted in the future.
* Currently, only flash and fat drivers are modified to support contexts. * Currently, only fat driver is modified to support UEFI context.
-> Applying changes to the other drivers is straightforward.
* ENV_IS_NOWHERE doesn't work if we want to disable U-Boot environment, but still want to enable UEFI (hence UEFI variables).
-> One solution would be to add *intermediate* configurations to set ENV_IS_NOWHERE properly in such a case.
* Any context won't have VARSTORAGE_NON_VOLATILE and VARSTORAGE_NON_VOLATILE_AUTOSAVE entries at the same time. This is because it will make "save" operation ugly and unnecessarily complicated as we discussed in ML.
-> In this sense, NON_VOLATILE[or _AUTOSAVE] should be attributed to a context itself.
* env_load() may lose some of compatibility; It now always imports variables *without* clearing existing entries (i.e. H_NOCLEAR specified) in order to support multiple contexts simultaneously.
-> I have no other good idea to solve this issue.
* Unfortunately, some of existing U-Boot variables seem to be "volatile" in nature. For example, we will see errors at boot time: ... Loading Environment from Flash... OK ## Error inserting "fdtcontroladdr" variable, errno=22 In: pl011@9000000 Out: pl011@9000000 Err: pl011@9000000 ## Error inserting "stdin" variable, errno=22 ## Error inserting "stdout" variable, errno=22 ## Error inserting "stderr" variable, errno=22
-> We will have to changes their attributes one-by-one. (Those can also be set through ENV_FLAGS_LIST_STATIC in env_flags.h).
* As described above, attribute information is visible to users. I'm afraid that it might lead to any incompatibility somewhere. (I don't notice any issues though.)
* The whole area of storage will be saved at *every* update of one UEFI variable. It should be optimized if possible.
* An error during "save" operation may cause inconsistency between cache (hash table) and the storage.
-> This is not UEFI specific though.
* Patch#15 may be unnecessary.
* Add tests if necessary.
Note: If we need "secure storage" for UEFI variables, efi_get_variable/ efi_get_next_variable_name/efi_set_variable() should be completely replaced with stub functions to communicate with secure world. This patch won't affect such an implementation.
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
Patch#1 to #5 are to add 'context' support to env interfaces. Patch#6 to #13 are to add 'variable storage' attribute to env interfaces. Patch#14 to #16 are to modify UEFI variable implementation to utilize new env interfaces.
Changes in v4 (July 17, 2019) * remove already-merged patches * revamp after Wolfgang's suggestion
Changes in v3 (June 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 (16): hashtable: extend interfaces to handle entries with context env: extend interfaces to import/export U-Boot environment per context env: extend interfaces to label variable with context env: flash: add U-Boot environment context support env: fat: add U-Boot environment context support env: add variable storage attribute support env: add/expose attribute helper functions for hashtable hashtable: import/export entries with flags hashtable: extend hdelete_ext for autosave env: save non-volatile variables only env: save a context immediately if 'autosave' variable is changed env: extend interfaces to get/set attributes cmd: env: show variable storage attribute in "env flags" command env: fat: support UEFI context env,efi_loader: define flags for well-known global UEFI variables efi_loader: variable: rework with new extended env interfaces
cmd/nvedit.c | 186 ++++++++++++++++++++++-------- env/Kconfig | 42 ++++++- env/common.c | 82 ++++++++++--- env/env.c | 92 +++++++++++---- env/fat.c | 112 +++++++++++++++--- env/flags.c | 149 +++++++++++++++++++++++- env/flash.c | 28 +++-- include/asm-generic/global_data.h | 7 +- include/efi_loader.h | 1 + include/env_default.h | 1 + include/env_flags.h | 63 +++++++++- include/environment.h | 89 ++++++++++++-- include/exports.h | 4 + include/search.h | 16 +++ lib/efi_loader/Kconfig | 12 ++ lib/efi_loader/Makefile | 2 +- lib/efi_loader/efi_setup.c | 5 + lib/efi_loader/efi_variable.c | 50 ++++++-- lib/hashtable.c | 143 ++++++++++++++++++++--- 19 files changed, 925 insertions(+), 159 deletions(-)