1# SPDX-License-Identifier: GPL-2.0-only 2menu "EFI (Extensible Firmware Interface) Support" 3 depends on EFI 4 5config EFI_ESRT 6 bool 7 depends on EFI 8 default y 9 10config EFI_VARS_PSTORE 11 tristate "Register efivars backend for pstore" 12 depends on PSTORE 13 select UCS2_STRING 14 default y 15 help 16 Say Y here to enable use efivars as a backend to pstore. This 17 will allow writing console messages, crash dumps, or anything 18 else supported by pstore to EFI variables. 19 20config EFI_VARS_PSTORE_DEFAULT_DISABLE 21 bool "Disable using efivars as a pstore backend by default" 22 depends on EFI_VARS_PSTORE 23 default n 24 help 25 Saying Y here will disable the use of efivars as a storage 26 backend for pstore by default. This setting can be overridden 27 using the efivars module's pstore_disable parameter. 28 29config EFI_SOFT_RESERVE 30 bool "Reserve EFI Specific Purpose Memory" 31 depends on EFI && EFI_STUB && ACPI_HMAT 32 default ACPI_HMAT 33 help 34 On systems that have mixed performance classes of memory EFI 35 may indicate specific purpose memory with an attribute (See 36 EFI_MEMORY_SP in UEFI 2.8). A memory range tagged with this 37 attribute may have unique performance characteristics compared 38 to the system's general purpose "System RAM" pool. On the 39 expectation that such memory has application specific usage, 40 and its base EFI memory type is "conventional" answer Y to 41 arrange for the kernel to reserve it as a "Soft Reserved" 42 resource, and set aside for direct-access (device-dax) by 43 default. The memory range can later be optionally assigned to 44 the page allocator by system administrator policy via the 45 device-dax kmem facility. Say N to have the kernel treat this 46 memory as "System RAM" by default. 47 48 If unsure, say Y. 49 50config EFI_DXE_MEM_ATTRIBUTES 51 bool "Adjust memory attributes in EFISTUB" 52 depends on EFI && EFI_STUB && X86 53 default y 54 help 55 UEFI specification does not guarantee all memory to be 56 accessible for both write and execute as the kernel expects 57 it to be. 58 Use DXE services to check and alter memory protection 59 attributes during boot via EFISTUB to ensure that memory 60 ranges used by the kernel are writable and executable. 61 62config EFI_PARAMS_FROM_FDT 63 bool 64 help 65 Select this config option from the architecture Kconfig if 66 the EFI runtime support gets system table address, memory 67 map address, and other parameters from the device tree. 68 69config EFI_RUNTIME_WRAPPERS 70 bool 71 72config EFI_GENERIC_STUB 73 bool 74 75config EFI_ZBOOT 76 bool "Enable the generic EFI decompressor" 77 depends on EFI_GENERIC_STUB && !ARM 78 select HAVE_KERNEL_GZIP 79 select HAVE_KERNEL_ZSTD 80 help 81 Create the bootable image as an EFI application that carries the 82 actual kernel image in compressed form, and decompresses it into 83 memory before executing it via LoadImage/StartImage EFI boot service 84 calls. For compatibility with non-EFI loaders, the payload can be 85 decompressed and executed by the loader as well, provided that the 86 loader implements the decompression algorithm and that non-EFI boot 87 is supported by the encapsulated image. (The compression algorithm 88 used is described in the zboot image header) 89 90config EFI_ARMSTUB_DTB_LOADER 91 bool "Enable the DTB loader" 92 depends on EFI_GENERIC_STUB && !RISCV && !LOONGARCH 93 default y 94 help 95 Select this config option to add support for the dtb= command 96 line parameter, allowing a device tree blob to be loaded into 97 memory from the EFI System Partition by the stub. 98 99 If the device tree is provided by the platform or by 100 the bootloader this option may not be needed. 101 But, for various development reasons and to maintain existing 102 functionality for bootloaders that do not have such support 103 this option is necessary. 104 105config EFI_BOOTLOADER_CONTROL 106 tristate "EFI Bootloader Control" 107 select UCS2_STRING 108 default n 109 help 110 This module installs a reboot hook, such that if reboot() is 111 invoked with a string argument NNN, "NNN" is copied to the 112 "LoaderEntryOneShot" EFI variable, to be read by the 113 bootloader. If the string matches one of the boot labels 114 defined in its configuration, the bootloader will boot once 115 to that label. The "LoaderEntryRebootReason" EFI variable is 116 set with the reboot reason: "reboot" or "shutdown". The 117 bootloader reads this reboot reason and takes particular 118 action according to its policy. 119 120config EFI_CAPSULE_LOADER 121 tristate "EFI capsule loader" 122 depends on EFI 123 help 124 This option exposes a loader interface "/dev/efi_capsule_loader" for 125 users to load EFI capsules. This driver requires working runtime 126 capsule support in the firmware, which many OEMs do not provide. 127 128 Most users should say N. 129 130config EFI_CAPSULE_QUIRK_QUARK_CSH 131 bool "Add support for Quark capsules with non-standard headers" 132 depends on X86 && !64BIT 133 select EFI_CAPSULE_LOADER 134 default y 135 help 136 Add support for processing Quark X1000 EFI capsules, whose header 137 layout deviates from the layout mandated by the UEFI specification. 138 139config EFI_TEST 140 tristate "EFI Runtime Service Tests Support" 141 depends on EFI 142 default n 143 help 144 This driver uses the efi.<service> function pointers directly instead 145 of going through the efivar API, because it is not trying to test the 146 kernel subsystem, just for testing the UEFI runtime service 147 interfaces which are provided by the firmware. This driver is used 148 by the Firmware Test Suite (FWTS) for testing the UEFI runtime 149 interfaces readiness of the firmware. 150 Details for FWTS are available from: 151 <https://wiki.ubuntu.com/FirmwareTestSuite> 152 153 Say Y here to enable the runtime services support via /dev/efi_test. 154 If unsure, say N. 155 156config EFI_DEV_PATH_PARSER 157 bool 158 159config APPLE_PROPERTIES 160 bool "Apple Device Properties" 161 depends on EFI_STUB && X86 162 select EFI_DEV_PATH_PARSER 163 select UCS2_STRING 164 help 165 Retrieve properties from EFI on Apple Macs and assign them to 166 devices, allowing for improved support of Apple hardware. 167 Properties that would otherwise be missing include the 168 Thunderbolt Device ROM and GPU configuration data. 169 170 If unsure, say Y if you have a Mac. Otherwise N. 171 172config RESET_ATTACK_MITIGATION 173 bool "Reset memory attack mitigation" 174 depends on EFI_STUB 175 help 176 Request that the firmware clear the contents of RAM after a reboot 177 using the TCG Platform Reset Attack Mitigation specification. This 178 protects against an attacker forcibly rebooting the system while it 179 still contains secrets in RAM, booting another OS and extracting the 180 secrets. This should only be enabled when userland is configured to 181 clear the MemoryOverwriteRequest flag on clean shutdown after secrets 182 have been evicted, since otherwise it will trigger even on clean 183 reboots. 184 185config EFI_RCI2_TABLE 186 bool "EFI Runtime Configuration Interface Table Version 2 Support" 187 depends on X86 || COMPILE_TEST 188 help 189 Displays the content of the Runtime Configuration Interface 190 Table version 2 on Dell EMC PowerEdge systems as a binary 191 attribute 'rci2' under /sys/firmware/efi/tables directory. 192 193 RCI2 table contains BIOS HII in XML format and is used to populate 194 BIOS setup page in Dell EMC OpenManage Server Administrator tool. 195 The BIOS setup page contains BIOS tokens which can be configured. 196 197 Say Y here for Dell EMC PowerEdge systems. 198 199config EFI_DISABLE_PCI_DMA 200 bool "Clear Busmaster bit on PCI bridges during ExitBootServices()" 201 help 202 Disable the busmaster bit in the control register on all PCI bridges 203 while calling ExitBootServices() and passing control to the runtime 204 kernel. System firmware may configure the IOMMU to prevent malicious 205 PCI devices from being able to attack the OS via DMA. However, since 206 firmware can't guarantee that the OS is IOMMU-aware, it will tear 207 down IOMMU configuration when ExitBootServices() is called. This 208 leaves a window between where a hostile device could still cause 209 damage before Linux configures the IOMMU again. 210 211 If you say Y here, the EFI stub will clear the busmaster bit on all 212 PCI bridges before ExitBootServices() is called. This will prevent 213 any malicious PCI devices from being able to perform DMA until the 214 kernel reenables busmastering after configuring the IOMMU. 215 216 This option will cause failures with some poorly behaved hardware 217 and should not be enabled without testing. The kernel commandline 218 options "efi=disable_early_pci_dma" or "efi=no_disable_early_pci_dma" 219 may be used to override this option. 220 221config EFI_EARLYCON 222 def_bool y 223 depends on SERIAL_EARLYCON && !ARM 224 select FONT_SUPPORT 225 select ARCH_USE_MEMREMAP_PROT 226 227config EFI_CUSTOM_SSDT_OVERLAYS 228 bool "Load custom ACPI SSDT overlay from an EFI variable" 229 depends on ACPI 230 default ACPI_TABLE_UPGRADE 231 help 232 Allow loading of an ACPI SSDT overlay from an EFI variable specified 233 by a kernel command line option. 234 235 See Documentation/admin-guide/acpi/ssdt-overlays.rst for more 236 information. 237 238config EFI_DISABLE_RUNTIME 239 bool "Disable EFI runtime services support by default" 240 default y if PREEMPT_RT 241 help 242 Allow to disable the EFI runtime services support by default. This can 243 already be achieved by using the efi=noruntime option, but it could be 244 useful to have this default without any kernel command line parameter. 245 246 The EFI runtime services are disabled by default when PREEMPT_RT is 247 enabled, because measurements have shown that some EFI functions calls 248 might take too much time to complete, causing large latencies which is 249 an issue for Real-Time kernels. 250 251 This default can be overridden by using the efi=runtime option. 252 253config EFI_COCO_SECRET 254 bool "EFI Confidential Computing Secret Area Support" 255 help 256 Confidential Computing platforms (such as AMD SEV) allow the 257 Guest Owner to securely inject secrets during guest VM launch. 258 The secrets are placed in a designated EFI reserved memory area. 259 260 In order to use the secrets in the kernel, the location of the secret 261 area (as published in the EFI config table) must be kept. 262 263 If you say Y here, the address of the EFI secret area will be kept 264 for usage inside the kernel. This will allow the 265 virt/coco/efi_secret module to access the secrets, which in turn 266 allows userspace programs to access the injected secrets. 267 268config UNACCEPTED_MEMORY 269 bool 270 depends on EFI_STUB 271 help 272 Some Virtual Machine platforms, such as Intel TDX, require 273 some memory to be "accepted" by the guest before it can be used. 274 This mechanism helps prevent malicious hosts from making changes 275 to guest memory. 276 277 UEFI specification v2.9 introduced EFI_UNACCEPTED_MEMORY memory type. 278 279 This option adds support for unaccepted memory and makes such memory 280 usable by the kernel. 281 282config EFI_EMBEDDED_FIRMWARE 283 bool 284 select CRYPTO_LIB_SHA256 285 286endmenu 287 288config UEFI_CPER 289 bool 290 291config UEFI_CPER_ARM 292 bool 293 depends on UEFI_CPER && ( ARM || ARM64 ) 294 default y 295 296config UEFI_CPER_X86 297 bool 298 depends on UEFI_CPER && X86 299 default y 300 301config TEE_STMM_EFI 302 tristate "TEE-based EFI runtime variable service driver" 303 depends on EFI && OPTEE 304 help 305 Select this config option if TEE is compiled to include StandAloneMM 306 as a separate secure partition. It has the ability to check and store 307 EFI variables on an RPMB or any other non-volatile medium used by 308 StandAloneMM. 309 310 Enabling this will change the EFI runtime services from the firmware 311 provided functions to TEE calls. 312 313 To compile this driver as a module, choose M here: the module 314 will be called tee_stmm_efi. 315