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Provide a description of the bootefi command. Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
135 lines
4 KiB
ReStructuredText
135 lines
4 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+
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.. Copyright 2020, Heinrich Schuchardt <xypron.glpk@gmx.de>
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bootefi command
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===============
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Synopsis
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--------
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::
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bootefi [image_addr] [fdt_addr]
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bootefi bootmgr [fdt_addr]
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bootefi hello [fdt_addr]
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bootefi selftest [fdt_addr]
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Description
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-----------
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The *bootefi* command is used to launch a UEFI binary which can be either of
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* UEFI application
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* UEFI boot services driver
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* UEFI run-time services driver
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An operating system requires a hardware description which can either be
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presented as ACPI table (CONFIG\_GENERATE\_ACPI\_TABLE=y) or as device-tree
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The load address of the device-tree may be provided as parameter *fdt\_addr*. If
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this address is not specified, the bootefi command will try to fall back in
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sequence to:
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* the device-tree specified by environment variable *fdt\_addr*
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* the device-tree specified by environment variable *fdtcontroladdr*
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The load address of the binary is specified by parameter *image_address*. A
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command sequence to run a UEFI application might look like
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::
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load mmc 0:2 $fdt_addr_r dtb
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load mmc 0:1 $kernel_addr_r /EFI/grub/grubaa64.efi
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bootefi $kernel_addr_r $fdt_addr_r
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The last file loaded defines the image file path in the loaded image protocol.
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Hence the executable should always be loaded last.
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The value of the environment variable *bootargs* is converted from UTF-8 to
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UTF-16 and passed as load options in the loaded image protocol to the UEFI
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binary.
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Note
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UEFI binaries that are contained in FIT images are launched via the
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*bootm* command.
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UEFI boot manager
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'''''''''''''''''
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The UEFI boot manager is invoked by the *bootefi bootmgr* sub-command.
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Here boot options are defined by UEFI variables with a name consisting of the
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letters *Boot* followed by a four digit hexadecimal number, e.g. *Boot0001* or
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*BootA03E*. The boot variable defines a label, the device path of the binary to
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execute as well as the load options passed in the loaded image protocol.
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If the UEFI variable *BootNext* is defined, it specifies the number of the boot
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option to execute next. If no binary can be loaded via *BootNext* the variable
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*BootOrder* specifies in which sequence boot options shalled be tried.
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The values of these variables can be managed using the U-Boot command
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*efidebug*.
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UEFI hello world application
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''''''''''''''''''''''''''''
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U-Boot can be compiled with a hello world application that can be launched using
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the *bootefi hello* sub-command. A session might look like
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::
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=> setenv bootargs 'Greetings to the world'
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=> bootefi hello
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Booting /MemoryMapped(0x0,0x10001000,0x1000)
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Hello, world!
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Running on UEFI 2.8
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Have SMBIOS table
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Have device tree
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Load options: Greetings to the world
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UEFI selftest
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'''''''''''''
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U-Boot can be compiled with UEFI unit tests. These unit tests are invoked using
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the *bootefi selftest* sub-command.
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Which unit test is executed is controlled by the environment variable
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*efi\_selftest*. If this variable is not set, all unit tests that are not marked
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as 'on request' are executed.
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To show a list of the available unit tests the value *list* can be used
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::
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=> setenv efi_selftest list
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=> bootefi selftest
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Available tests:
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'block image transfer' - on request
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'block device'
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'configuration tables'
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...
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A single test is selected for execution by setting the *efi\_selftest*
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environment variable to match one of the listed identifiers
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::
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=> setenv efi_selftest 'block image transfer'
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=> bootefi selftest
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Some of the tests execute the ExitBootServices() UEFI boot service and will not
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return to the command line but require a board reset.
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Configuration
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-------------
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To use the *bootefi* command you must specify CONFIG\_CMD\_BOOTEFI=y.
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The *bootefi hello* sub-command requries CMD\_BOOTEFI\_HELLO=y.
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The *bootefi selftest* sub-command depends on CMD\_BOOTEFI\_SELFTEST=y.
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See also
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--------
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* *bootm* for launching UEFI binaries packed in FIT images
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* *booti*, *bootm*, *bootz* for launching a Linux kernel without using the
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UEFI sub-system
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* *efidebug* for setting UEFI boot variables
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