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efi_loader: efi variable support

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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@gmail.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
This commit is contained in:
Rob Clark
2017-09-13 18:05:37 -04:00
committed by Alexander Graf
parent 946160f334
commit ad644e7c18
7 changed files with 388 additions and 5 deletions
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19
include/efi.h
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@@ -324,6 +324,25 @@ extern char image_base[];
/* Start and end of U-Boot image (for payload) */
extern char _binary_u_boot_bin_start[], _binary_u_boot_bin_end[];
/*
* Variable Attributes
*/
#define EFI_VARIABLE_NON_VOLATILE 0x0000000000000001
#define EFI_VARIABLE_BOOTSERVICE_ACCESS 0x0000000000000002
#define EFI_VARIABLE_RUNTIME_ACCESS 0x0000000000000004
#define EFI_VARIABLE_HARDWARE_ERROR_RECORD 0x0000000000000008
#define EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS 0x0000000000000010
#define EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS 0x0000000000000020
#define EFI_VARIABLE_APPEND_WRITE 0x0000000000000040
#define EFI_VARIABLE_MASK (EFI_VARIABLE_NON_VOLATILE | \
EFI_VARIABLE_BOOTSERVICE_ACCESS | \
EFI_VARIABLE_RUNTIME_ACCESS | \
EFI_VARIABLE_HARDWARE_ERROR_RECORD | \
EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS | \
EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS | \
EFI_VARIABLE_APPEND_WRITE)
/**
* efi_get_sys_table() - Get access to the main EFI system table
*