# SPDX-License-Identifier: GPL-2.0-only menu "EFI (Extensible Firmware Interface) Support" depends on EFI config EFI_ESRT bool depends on EFI default y config EFI_VARS_PSTORE tristate "Register efivars backend for pstore" depends on PSTORE select UCS2_STRING default y help Say Y here to enable use efivars as a backend to pstore. This will allow writing console messages, crash dumps, or anything else supported by pstore to EFI variables. config EFI_VARS_PSTORE_DEFAULT_DISABLE bool "Disable using efivars as a pstore backend by default" depends on EFI_VARS_PSTORE default n help Saying Y here will disable the use of efivars as a storage backend for pstore by default. This setting can be overridden using the efivars module's pstore_disable parameter. config EFI_SOFT_RESERVE bool "Reserve EFI Specific Purpose Memory" depends on EFI && EFI_STUB && ACPI_HMAT default ACPI_HMAT help On systems that have mixed performance classes of memory EFI may indicate specific purpose memory with an attribute (See EFI_MEMORY_SP in UEFI 2.8). A memory range tagged with this attribute may have unique performance characteristics compared to the system's general purpose "System RAM" pool. On the expectation that such memory has application specific usage, and its base EFI memory type is "conventional" answer Y to arrange for the kernel to reserve it as a "Soft Reserved" resource, and set aside for direct-access (device-dax) by default. The memory range can later be optionally assigned to the page allocator by system administrator policy via the device-dax kmem facility. Say N to have the kernel treat this memory as "System RAM" by default. If unsure, say Y. config EFI_DXE_MEM_ATTRIBUTES bool "Adjust memory attributes in EFISTUB" depends on EFI && EFI_STUB && X86 default y help UEFI specification does not guarantee all memory to be accessible for both write and execute as the kernel expects it to be. Use DXE services to check and alter memory protection attributes during boot via EFISTUB to ensure that memory ranges used by the kernel are writable and executable. config EFI_PARAMS_FROM_FDT bool help Select this config option from the architecture Kconfig if the EFI runtime support gets system table address, memory map address, and other parameters from the device tree. config EFI_RUNTIME_WRAPPERS bool config EFI_GENERIC_STUB bool config EFI_ZBOOT bool "Enable the generic EFI decompressor" depends on EFI_GENERIC_STUB && !ARM select HAVE_KERNEL_GZIP select HAVE_KERNEL_LZ4 select HAVE_KERNEL_LZMA select HAVE_KERNEL_LZO select HAVE_KERNEL_XZ select HAVE_KERNEL_ZSTD help Create the bootable image as an EFI application that carries the actual kernel image in compressed form, and decompresses it into memory before executing it. For compatibility with non-EFI loaders, the payload can be decompressed and executed by the loader as well, provided that the loader implements the decompression algorithm. (The compression algorithm used is described in the zboot header) config EFI_ARMSTUB_DTB_LOADER bool "Enable the DTB loader" depends on EFI_GENERIC_STUB && !RISCV && !LOONGARCH default y 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. If the device tree is provided by the platform or by the bootloader this option may not be needed. But, for various development reasons and to maintain existing functionality for bootloaders that do not have such support this option is necessary. config EFI_BOOTLOADER_CONTROL tristate "EFI Bootloader Control" select UCS2_STRING default n help This module installs a reboot hook, such that if reboot() is invoked with a string argument NNN, "NNN" is copied to the "LoaderEntryOneShot" EFI variable, to be read by the bootloader. If the string matches one of the boot labels defined in its configuration, the bootloader will boot once to that label. The "LoaderEntryRebootReason" EFI variable is set with the reboot reason: "reboot" or "shutdown". The bootloader reads this reboot reason and takes particular action according to its policy. config EFI_CAPSULE_LOADER tristate "EFI capsule loader" depends on EFI help This option exposes a loader interface "/dev/efi_capsule_loader" for users to load EFI capsules. This driver requires working runtime capsule support in the firmware, which many OEMs do not provide. Most users should say N. config EFI_CAPSULE_QUIRK_QUARK_CSH bool "Add support for Quark capsules with non-standard headers" depends on X86 && !64BIT select EFI_CAPSULE_LOADER default y help Add support for processing Quark X1000 EFI capsules, whose header layout deviates from the layout mandated by the UEFI specification. config EFI_TEST tristate "EFI Runtime Service Tests Support" depends on EFI default n help This driver uses the efi. function pointers directly instead of going through the efivar API, because it is not trying to test the kernel subsystem, just for testing the UEFI runtime service interfaces which are provided by the firmware. This driver is used by the Firmware Test Suite (FWTS) for testing the UEFI runtime interfaces readiness of the firmware. Details for FWTS are available from: Say Y here to enable the runtime services support via /dev/efi_test. If unsure, say N. config EFI_DEV_PATH_PARSER bool config APPLE_PROPERTIES bool "Apple Device Properties" depends on EFI_STUB && X86 select EFI_DEV_PATH_PARSER select UCS2_STRING help Retrieve properties from EFI on Apple Macs and assign them to devices, allowing for improved support of Apple hardware. Properties that would otherwise be missing include the Thunderbolt Device ROM and GPU configuration data. If unsure, say Y if you have a Mac. Otherwise N. config RESET_ATTACK_MITIGATION bool "Reset memory attack mitigation" depends on EFI_STUB help Request that the firmware clear the contents of RAM after a reboot using the TCG Platform Reset Attack Mitigation specification. This protects against an attacker forcibly rebooting the system while it still contains secrets in RAM, booting another OS and extracting the secrets. This should only be enabled when userland is configured to clear the MemoryOverwriteRequest flag on clean shutdown after secrets have been evicted, since otherwise it will trigger even on clean reboots. config EFI_RCI2_TABLE bool "EFI Runtime Configuration Interface Table Version 2 Support" depends on X86 || COMPILE_TEST help Displays the content of the Runtime Configuration Interface Table version 2 on Dell EMC PowerEdge systems as a binary attribute 'rci2' under /sys/firmware/efi/tables directory. RCI2 table contains BIOS HII in XML format and is used to populate BIOS setup page in Dell EMC OpenManage Server Administrator tool. The BIOS setup page contains BIOS tokens which can be configured. Say Y here for Dell EMC PowerEdge systems. config EFI_DISABLE_PCI_DMA bool "Clear Busmaster bit on PCI bridges during ExitBootServices()" help Disable the busmaster bit in the control register on all PCI bridges while calling ExitBootServices() and passing control to the runtime kernel. System firmware may configure the IOMMU to prevent malicious PCI devices from being able to attack the OS via DMA. However, since firmware can't guarantee that the OS is IOMMU-aware, it will tear down IOMMU configuration when ExitBootServices() is called. This leaves a window between where a hostile device could still cause damage before Linux configures the IOMMU again. If you say Y here, the EFI stub will clear the busmaster bit on all PCI bridges before ExitBootServices() is called. This will prevent any malicious PCI devices from being able to perform DMA until the kernel reenables busmastering after configuring the IOMMU. This option will cause failures with some poorly behaved hardware and should not be enabled without testing. The kernel commandline options "efi=disable_early_pci_dma" or "efi=no_disable_early_pci_dma" may be used to override this option. config EFI_EARLYCON def_bool y depends on SERIAL_EARLYCON && !ARM select FONT_SUPPORT select ARCH_USE_MEMREMAP_PROT config EFI_CUSTOM_SSDT_OVERLAYS bool "Load custom ACPI SSDT overlay from an EFI variable" depends on ACPI default ACPI_TABLE_UPGRADE help Allow loading of an ACPI SSDT overlay from an EFI variable specified by a kernel command line option. See Documentation/admin-guide/acpi/ssdt-overlays.rst for more information. config EFI_DISABLE_RUNTIME bool "Disable EFI runtime services support by default" default y if PREEMPT_RT help Allow to disable the EFI runtime services support by default. This can already be achieved by using the efi=noruntime option, but it could be useful to have this default without any kernel command line parameter. The EFI runtime services are disabled by default when PREEMPT_RT is enabled, because measurements have shown that some EFI functions calls might take too much time to complete, causing large latencies which is an issue for Real-Time kernels. This default can be overridden by using the efi=runtime option. config EFI_COCO_SECRET bool "EFI Confidential Computing Secret Area Support" help Confidential Computing platforms (such as AMD SEV) allow the Guest Owner to securely inject secrets during guest VM launch. The secrets are placed in a designated EFI reserved memory area. In order to use the secrets in the kernel, the location of the secret area (as published in the EFI config table) must be kept. If you say Y here, the address of the EFI secret area will be kept for usage inside the kernel. This will allow the virt/coco/efi_secret module to access the secrets, which in turn allows userspace programs to access the injected secrets. config UNACCEPTED_MEMORY bool depends on EFI_STUB help Some Virtual Machine platforms, such as Intel TDX, require some memory to be "accepted" by the guest before it can be used. This mechanism helps prevent malicious hosts from making changes to guest memory. UEFI specification v2.9 introduced EFI_UNACCEPTED_MEMORY memory type. This option adds support for unaccepted memory and makes such memory usable by the kernel. config EFI_EMBEDDED_FIRMWARE bool select CRYPTO_LIB_SHA256 endmenu config UEFI_CPER bool config UEFI_CPER_ARM bool depends on UEFI_CPER && ( ARM || ARM64 ) default y config UEFI_CPER_X86 bool depends on UEFI_CPER && X86 default y config TEE_STMM_EFI tristate "TEE-based EFI runtime variable service driver" depends on EFI && OPTEE help Select this config option if TEE is compiled to include StandAloneMM as a separate secure partition. It has the ability to check and store EFI variables on an RPMB or any other non-volatile medium used by StandAloneMM. Enabling this will change the EFI runtime services from the firmware provided functions to TEE calls. To compile this driver as a module, choose M here: the module will be called tee_stmm_efi.