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README.efi describes two different concepts: * U-Boot exposing the UEFI API * U-Boot running on top of UEFI. This patch splits the document in two. Religious references are removed. The separation of the concepts makes sense before detailing the internals of U-Boot exposing the UEFI API in a future patch. Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de> Signed-off-by: Alexander Graf <agraf@suse.de>
87 lines
2.1 KiB
Plaintext
87 lines
2.1 KiB
Plaintext
#
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# Copyright (C) 2015 Google, Inc
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#
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# SPDX-License-Identifier: GPL-2.0+
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#
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EFI on U-Boot
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=============
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This document provides information about the implementation of the UEFI API [1]
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in U-Boot.
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=========== Table of Contents ===========
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Motivation
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How do I get it?
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Status
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Future work
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Motivation
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----------
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With this API support in place, you can run any UEFI payload (such as the Linux
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kernel, grub2 or gummiboot) on U-Boot. This dramatically simplifies boot loader
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configuration, as U-Boot based systems now look and feel (almost) the same way
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as TianoCore based systems.
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How do I get it?
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----------------
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EFI support for 32bit ARM and AArch64 is already included in U-Boot. All you
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need to do is enable
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CONFIG_CMD_BOOTEFI=y
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CONFIG_EFI_LOADER=y
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in your .config file and you will automatically get a bootefi command to run
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an efi application as well as snippet in the default distro boot script that
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scans for removable media efi binaries as fallback.
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Status
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------
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I am successfully able to run grub2 and Linux EFI binaries with this code on
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ARMv7 as well as AArch64 systems.
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When enabled, the resulting U-Boot binary only grows by ~10KB, so it's very
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light weight.
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All storage devices are directly accessible from the uEFI payload
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Removable media booting (search for /efi/boot/boota{a64,arm}.efi) is supported.
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Simple use cases like "Plug this SD card into my ARM device and it just
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boots into grub which boots into Linux", work very well.
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Running HelloWord.efi
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---------------------
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You can run a simple 'hello world' EFI program in U-Boot.
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Enable the option CONFIG_CMD_BOOTEFI_HELLO.
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Then you can boot into U-Boot and type:
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> bootefi hello
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The 'hello world EFI' program will then run, print a message and exit.
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Future work
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-----------
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Of course, there are still a few things one could do on top:
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- Improve disk media detection (don't scan, use what information we
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have)
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- Add EFI variable support using NVRAM
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- Add GFX support
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- Make EFI Shell work
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- Network device support
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- Support for payload exit
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- Payload Watchdog support
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[1] http://uefi.org/
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