There are various ways a platform can provide a device tree binary to the kernel, with different levels of sophistication: - ideally, the UEFI firmware, which is tightly coupled with the platform, provides a device tree image directly as a UEFI configuration table, and typically permits the contents to be manipulated either via menu options or via UEFI environment variables that specify a replacement image, - GRUB for ARM has a 'devicetree' directive which allows a device tree image to be loaded from any location accessible to GRUB, and supersede the one provided by the firmware, - the EFI stub implements a dtb= command line option that allows a device tree image to be loaded from a file residing in the same file system as the one the kernel image was loaded from.
The dtb= command line option was never intended to be more than a development feature, to allow the other options to be implemented in parallel. So let's make it an opt-in feature that is disabled by default, but can be re-enabled at will. Note that we already disable the dtb= command line option when we detect that we are running with UEFI Secure Boot enabled. Signed-off-by: Ard Biesheuvel <[email protected]> --- drivers/firmware/efi/Kconfig | 12 ++++++++++++ drivers/firmware/efi/libstub/arm-stub.c | 7 ++++--- 2 files changed, 16 insertions(+), 3 deletions(-) diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig index 781a4a337557..fc1cb2961d5b 100644 --- a/drivers/firmware/efi/Kconfig +++ b/drivers/firmware/efi/Kconfig @@ -87,6 +87,18 @@ config EFI_RUNTIME_WRAPPERS config EFI_ARMSTUB bool +config EFI_ARMSTUB_DTB_LOADER + bool "Enable the DTB loader" + depends on EFI_ARMSTUB + help + Select this config option to add support for the dtb= command + line parameter, allowing a device tree blob to be loaded into + memory from the EFI System Partition by the stub. + + The device tree is typically provided by the platform or by + the bootloader, and so this option is mostly for development + purposes only. + config EFI_BOOTLOADER_CONTROL tristate "EFI Bootloader Control" depends on EFI_VARS diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c index 01a9d78ee415..c98b1856fc3d 100644 --- a/drivers/firmware/efi/libstub/arm-stub.c +++ b/drivers/firmware/efi/libstub/arm-stub.c @@ -202,9 +202,10 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table, * 'dtb=' unless UEFI Secure Boot is disabled. We assume that secure * boot is enabled if we can't determine its state. */ - if (secure_boot != efi_secureboot_mode_disabled && - strstr(cmdline_ptr, "dtb=")) { - pr_efi(sys_table, "Ignoring DTB from command line.\n"); + if (!IS_ENABLED(CONFIG_EFI_ARMSTUB_DTB_LOADER) || + secure_boot != efi_secureboot_mode_disabled) { + if (strstr(cmdline_ptr, "dtb=")) + pr_efi(sys_table, "Ignoring DTB from command line.\n"); } else { status = handle_cmdline_files(sys_table, image, cmdline_ptr, "dtb=", -- 2.11.0 -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
