65 строки
3.2 KiB
Plaintext
65 строки
3.2 KiB
Plaintext
|
UEFI, the Unified Extensible Firmware Interface, is a specification
|
||
|
|
governing the behaviours of compatible firmware interfaces. It is
|
||
|
|
maintained by the UEFI Forum - http://www.uefi.org/.
|
||
|
|
|
||
|
|
UEFI is an evolution of its predecessor 'EFI', so the terms EFI and
|
||
|
|
UEFI are used somewhat interchangeably in this document and associated
|
||
|
|
source code. As a rule, anything new uses 'UEFI', whereas 'EFI' refers
|
||
|
|
to legacy code or specifications.
|
||
|
|
|
||
|
|
UEFI support in Linux
|
||
|
|
=====================
|
||
|
|
Booting on a platform with firmware compliant with the UEFI specification
|
||
|
|
makes it possible for the kernel to support additional features:
|
||
|
|
- UEFI Runtime Services
|
||
|
|
- Retrieving various configuration information through the standardised
|
||
|
|
interface of UEFI configuration tables. (ACPI, SMBIOS, ...)
|
||
|
|
|
||
|
|
For actually enabling [U]EFI support, enable:
|
||
|
|
- CONFIG_EFI=y
|
||
|
|
- CONFIG_EFI_VARS=y or m
|
||
|
|
|
||
|
|
The implementation depends on receiving information about the UEFI environment
|
||
|
|
in a Flattened Device Tree (FDT) - so is only available with CONFIG_OF.
|
||
|
|
|
||
|
|
UEFI stub
|
||
|
|
=========
|
||
|
|
The "stub" is a feature that extends the Image/zImage into a valid UEFI
|
||
|
|
PE/COFF executable, including a loader application that makes it possible to
|
||
|
|
load the kernel directly from the UEFI shell, boot menu, or one of the
|
||
|
|
lightweight bootloaders like Gummiboot or rEFInd.
|
||
|
|
|
||
|
|
The kernel image built with stub support remains a valid kernel image for
|
||
|
|
booting in non-UEFI environments.
|
||
|
|
|
||
|
|
UEFI kernel support on ARM
|
||
|
|
==========================
|
||
|
|
UEFI kernel support on the ARM architectures (arm and arm64) is only available
|
||
|
|
when boot is performed through the stub.
|
||
|
|
|
||
|
|
When booting in UEFI mode, the stub deletes any memory nodes from a provided DT.
|
||
|
|
Instead, the kernel reads the UEFI memory map.
|
||
|
|
|
||
|
|
The stub populates the FDT /chosen node with (and the kernel scans for) the
|
||
|
|
following parameters:
|
||
|
|
________________________________________________________________________________
|
||
|
|
Name | Size | Description
|
||
|
|
================================================================================
|
||
|
|
linux,uefi-system-table | 64-bit | Physical address of the UEFI System Table.
|
||
|
|
--------------------------------------------------------------------------------
|
||
|
|
linux,uefi-mmap-start | 64-bit | Physical address of the UEFI memory map,
|
||
|
|
| | populated by the UEFI GetMemoryMap() call.
|
||
|
|
--------------------------------------------------------------------------------
|
||
|
|
linux,uefi-mmap-size | 32-bit | Size in bytes of the UEFI memory map
|
||
|
|
| | pointed to in previous entry.
|
||
|
|
--------------------------------------------------------------------------------
|
||
|
|
linux,uefi-mmap-desc-size | 32-bit | Size in bytes of each entry in the UEFI
|
||
|
|
| | memory map.
|
||
|
|
--------------------------------------------------------------------------------
|
||
|
|
linux,uefi-mmap-desc-ver | 32-bit | Version of the mmap descriptor format.
|
||
|
|
--------------------------------------------------------------------------------
|
||
|
|
linux,uefi-stub-kern-ver | string | Copy of linux_banner from build.
|
||
|
|
--------------------------------------------------------------------------------
|
||
|
|
|
||
|
|
For verbose debug messages, specify 'uefi_debug' on the kernel command line.
|