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efi_loader: UEFI variable persistence

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Persist non-volatile UEFI variables in a file on the EFI system partition.

The file is written whenever a non-volatile UEFI variable is changed after
initialization of the UEFI sub-system.

The file is read during the UEFI sub-system initialization to restore
non-volatile UEFI variables.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
This commit is contained in:
Heinrich Schuchardt 2020-03-19 18:21:58 +00:00
parent 198bf6418e
commit 5f7dcf079d
5 changed files with 319 additions and 1 deletions
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62
include/efi_variable.h
View file

@ -79,4 +79,66 @@ efi_status_t efi_query_variable_info_int(u32 attributes,
u64 *remaining_variable_storage_size,
u64 *maximum_variable_size);
#define EFI_VAR_FILE_NAME "ubootefi.var"
#define EFI_VAR_BUF_SIZE 0x4000
#define EFI_VAR_FILE_MAGIC 0x0161566966456255 /* UbEfiVa, version 1 */
/**
* struct efi_var_entry - UEFI variable file entry
*
* @length: length of enty, multiple of 8
* @attr: variable attributes
* @time: authentication time (seconds since start of epoch)
* @guid: vendor GUID
* @name: UTF16 variable name
*/
struct efi_var_entry {
u32 length;
u32 attr;
u64 time;
efi_guid_t guid;
u16 name[];
};
/**
* struct efi_var_file - file for storing UEFI variables
*
* @reserved: unused, may be overwritten by memory probing
* @magic: identifies file format
* @length: length including header
* @crc32: CRC32 without header
* @var: variables
*/
struct efi_var_file {
u64 reserved;
u64 magic;
u32 length;
u32 crc32;
struct efi_var_entry var[];
};
/**
* efi_var_to_file() - save non-volatile variables as file
*
* File ubootefi.var is created on the EFI system partion.
*
* Return: status code
*/
efi_status_t efi_var_to_file(void);
/**
* efi_var_from_file() - read variables from file
*
* File ubootefi.var is read from the EFI system partitions and the variables
* stored in the file are created.
*
* In case the file does not exist yet or a variable cannot be set EFI_SUCCESS
* is returned.
*
* Return: status code
*/
efi_status_t efi_var_from_file(void);
#endif