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