efi_loader: bootmgr: add booting from removable media
Under the current implementation, booting from removable media using a architecture-specific default image name, say BOOTAA64.EFI, is supported only in distro_bootcmd script. See the commit 74522c89 ("efi_loader: Add distro boot script for removable media"). This is, however, half-baked implementation because 1) UEFI specification requires this feature to be implemented as part of Boot Manager's responsibility: 3 - Boot Manager 3.5.1 Boot via the Simple File Protocol When booting via the EFI_SIMPLE_FILE_SYSTEM_PROTOCOL, the FilePath will start with a device path that points to the device that implements the EFI_SIMPLE_FILE_SYSTEM_PROTOCOL or the EFI_BLOCK_IO_PROTOCOL. The next part of the FilePath may point to the file name, including subdirectories, which contain the bootable image. If the file name is a null device path, the file name must be generated from the rules defined below. ... 3.5.1.1 Removable Media Boot Behavior To generate a file name when none is present in the FilePath, the firmware must append a default file name in the form \EFI\BOOT\BOOT{machine type short-name}.EFI ... 2) So (1) entails the hehavior that the user's preference of boot media order should be determined by Boot#### and BootOrder variables. With this patch, the semantics mentioned above is fully implemented. For example, if you want to boot the system from USB and SCSI in this order, * define Boot0001 which contains only a device path to the USB device (without any file path/name) * define Boot0002 which contains only a device path to the SCSI device, and * set BootOrder to Boot0001:Boot0002 To avoid build error for sandbox, default file name "BOOTSANDBOX.efi" is defined even if it is out of scope of UEFI specification. Signed-off-by:AKASHI Takahiro <takahiro.akashi@linaro.org> Signed-off-by:
Masahisa Kojima <masahisa.kojima@linaro.org> On sandbox use binary name corresponding to host architecture. Reviewed-by:
Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
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