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79 lines
2.6 KiB
79 lines
2.6 KiB
What: /sys/firmware/efi/vars |
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Date: April 2004 |
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Contact: Matt Domsch <[email protected]> |
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Description: |
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This directory exposes interfaces for interactive with |
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EFI variables. For more information on EFI variables, |
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see 'Variable Services' in the UEFI specification |
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(section 7.2 in specification version 2.3 Errata D). |
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In summary, EFI variables are named, and are classified |
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into separate namespaces through the use of a vendor |
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GUID. They also have an arbitrary binary value |
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associated with them. |
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The efivars module enumerates these variables and |
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creates a separate directory for each one found. Each |
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directory has a name of the form "<key>-<vendor guid>" |
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and contains the following files: |
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=============== ======================================== |
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attributes: A read-only text file enumerating the |
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EFI variable flags. Potential values |
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include: |
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EFI_VARIABLE_NON_VOLATILE |
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EFI_VARIABLE_BOOTSERVICE_ACCESS |
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EFI_VARIABLE_RUNTIME_ACCESS |
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EFI_VARIABLE_HARDWARE_ERROR_RECORD |
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EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS |
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See the EFI documentation for an |
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explanation of each of these variables. |
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data: A read-only binary file that can be read |
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to attain the value of the EFI variable |
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guid: The vendor GUID of the variable. This |
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should always match the GUID in the |
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variable's name. |
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raw_var: A binary file that can be read to obtain |
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a structure that contains everything |
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there is to know about the variable. |
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For structure definition see "struct |
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efi_variable" in the kernel sources. |
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This file can also be written to in |
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order to update the value of a variable. |
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For this to work however, all fields of |
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the "struct efi_variable" passed must |
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match byte for byte with the structure |
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read out of the file, save for the value |
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portion. |
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**Note** the efi_variable structure |
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read/written with this file contains a |
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'long' type that may change widths |
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depending on your underlying |
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architecture. |
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size: As ASCII representation of the size of |
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the variable's value. |
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=============== ======================================== |
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In addition, two other magic binary files are provided |
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in the top-level directory and are used for adding and |
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removing variables: |
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=============== ======================================== |
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new_var: Takes a "struct efi_variable" and |
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instructs the EFI firmware to create a |
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new variable. |
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del_var: Takes a "struct efi_variable" and |
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instructs the EFI firmware to remove any |
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variable that has a matching vendor GUID |
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and variable key name. |
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=============== ========================================
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