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UEFI subsystem

Lauching UEFI images

Bootefi command

The bootefi command is used to start UEFI applications or to install UEFI drivers. It takes two parameters

bootefi <image address> [fdt address]
  • image address - the memory address of the UEFI binary
  • fdt address - the memory address of the flattened device tree

The environment variable 'bootargs' is passed as load options in the UEFI system table. The Linux kernel EFI stub uses the load options as command line arguments.

.. kernel-doc:: cmd/bootefi.c
   :internal:

Boot manager

The UEFI specification foresees to define boot entries and boot sequence via UEFI variables. Booting according to these variables is possible via

bootefi bootmgr [fdt address]
  • fdt address - the memory address of the flattened device tree

The relevant variables are:

  • Boot0000-BootFFFF define boot entries
  • BootNext specifies next boot option to be booted
  • BootOrder specifies in which sequence the boot options shall be tried if BootNext is not defined or booting via BootNext fails
.. kernel-doc:: lib/efi_loader/efi_bootmgr.c
   :internal:

Efidebug command

The efidebug command is used to set and display boot options as well as to display information about internal data of the UEFI subsystem (devices, drivers, handles, loaded images, and the memory map).

.. kernel-doc:: cmd/efidebug.c
   :internal:

Initialization of the UEFI sub-system

.. kernel-doc:: lib/efi_loader/efi_setup.c
   :internal:

Boot services

.. kernel-doc:: lib/efi_loader/efi_boottime.c
   :internal:

Image relocation

.. kernel-doc:: lib/efi_loader/efi_image_loader.c
   :internal:

Memory services

.. kernel-doc:: lib/efi_loader/efi_memory.c
   :internal:

SetWatchdogTimer service

.. kernel-doc:: lib/efi_loader/efi_watchdog.c
   :internal:

Runtime services

.. kernel-doc:: lib/efi_loader/efi_runtime.c
   :internal:

Variable services

.. kernel-doc:: include/efi_variable.h
   :internal:

.. kernel-doc:: lib/efi_loader/efi_variable.c
   :internal:

UEFI drivers

UEFI driver uclass

.. kernel-doc:: lib/efi_driver/efi_uclass.c
   :internal:

Block device driver

.. kernel-doc:: lib/efi_driver/efi_block_device.c
   :internal:

Protocols

Block IO protocol

.. kernel-doc:: lib/efi_loader/efi_disk.c
   :internal:

File protocol

.. kernel-doc:: lib/efi_loader/efi_file.c
   :internal:

Graphical output protocol

.. kernel-doc:: lib/efi_loader/efi_gop.c
   :internal:

Load file 2 protocol

The load file 2 protocol can be used by the Linux kernel to load the initial RAM disk. U-Boot can be configured to provide an implementation.

.. kernel-doc:: lib/efi_loader/efi_load_initrd.c
   :internal:

Network protocols

.. kernel-doc:: lib/efi_loader/efi_net.c
   :internal:

Random number generator protocol

.. kernel-doc:: lib/efi_loader/efi_rng.c
   :internal:

Text IO protocols

.. kernel-doc:: lib/efi_loader/efi_console.c
   :internal:

Unicode Collation protocol

.. kernel-doc:: lib/efi_loader/efi_unicode_collation.c
   :internal:

Firmware management protocol

.. kernel-doc:: lib/efi_loader/efi_firmware.c
   :internal:

Unit testing

The following library functions are provided to support writing UEFI unit tests. The should not be used elsewhere.

.. kernel-doc:: include/efi_selftest.h
   :internal: