1 # SPDX-License-Identifier: GPL-2.0-only 2 menu "EFI (Extensible Firmware Interface) Support" 3 depends on EFI 4 5 config EFI_ESRT 6 bool 7 depends on EFI 8 default y 9 10 config 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 20 config 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 29 config 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 50 config 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 62 config 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 69 config EFI_RUNTIME_WRAPPERS 70 bool 71 72 config EFI_GENERIC_STUB 73 bool 74 75 config 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_LZ4 80 select HAVE_KERNEL_LZMA 81 select HAVE_KERNEL_LZO 82 select HAVE_KERNEL_XZ 83 select HAVE_KERNEL_ZSTD 84 help 85 Create the bootable image as an EFI application that carries the 86 actual kernel image in compressed form, and decompresses it into 87 memory before executing it via LoadImage/StartImage EFI boot service 88 calls. For compatibility with non-EFI loaders, the payload can be 89 decompressed and executed by the loader as well, provided that the 90 loader implements the decompression algorithm and that non-EFI boot 91 is supported by the encapsulated image. (The compression algorithm 92 used is described in the zboot image header) 93 94 config EFI_ARMSTUB_DTB_LOADER 95 bool "Enable the DTB loader" 96 depends on EFI_GENERIC_STUB && !RISCV && !LOONGARCH 97 default y 98 help 99 Select this config option to add support for the dtb= command 100 line parameter, allowing a device tree blob to be loaded into 101 memory from the EFI System Partition by the stub. 102 103 If the device tree is provided by the platform or by 104 the bootloader this option may not be needed. 105 But, for various development reasons and to maintain existing 106 functionality for bootloaders that do not have such support 107 this option is necessary. 108 109 config EFI_BOOTLOADER_CONTROL 110 tristate "EFI Bootloader Control" 111 select UCS2_STRING 112 default n 113 help 114 This module installs a reboot hook, such that if reboot() is 115 invoked with a string argument NNN, "NNN" is copied to the 116 "LoaderEntryOneShot" EFI variable, to be read by the 117 bootloader. If the string matches one of the boot labels 118 defined in its configuration, the bootloader will boot once 119 to that label. The "LoaderEntryRebootReason" EFI variable is 120 set with the reboot reason: "reboot" or "shutdown". The 121 bootloader reads this reboot reason and takes particular 122 action according to its policy. 123 124 config EFI_CAPSULE_LOADER 125 tristate "EFI capsule loader" 126 depends on EFI 127 help 128 This option exposes a loader interface "/dev/efi_capsule_loader" for 129 users to load EFI capsules. This driver requires working runtime 130 capsule support in the firmware, which many OEMs do not provide. 131 132 Most users should say N. 133 134 config EFI_CAPSULE_QUIRK_QUARK_CSH 135 bool "Add support for Quark capsules with non-standard headers" 136 depends on X86 && !64BIT 137 select EFI_CAPSULE_LOADER 138 default y 139 help 140 Add support for processing Quark X1000 EFI capsules, whose header 141 layout deviates from the layout mandated by the UEFI specification. 142 143 config EFI_TEST 144 tristate "EFI Runtime Service Tests Support" 145 depends on EFI 146 default n 147 help 148 This driver uses the efi.<service> function pointers directly instead 149 of going through the efivar API, because it is not trying to test the 150 kernel subsystem, just for testing the UEFI runtime service 151 interfaces which are provided by the firmware. This driver is used 152 by the Firmware Test Suite (FWTS) for testing the UEFI runtime 153 interfaces readiness of the firmware. 154 Details for FWTS are available from: 155 <https://wiki.ubuntu.com/FirmwareTestSuite> 156 157 Say Y here to enable the runtime services support via /dev/efi_test. 158 If unsure, say N. 159 160 config EFI_DEV_PATH_PARSER 161 bool 162 163 config APPLE_PROPERTIES 164 bool "Apple Device Properties" 165 depends on EFI_STUB && X86 166 select EFI_DEV_PATH_PARSER 167 select UCS2_STRING 168 help 169 Retrieve properties from EFI on Apple Macs and assign them to 170 devices, allowing for improved support of Apple hardware. 171 Properties that would otherwise be missing include the 172 Thunderbolt Device ROM and GPU configuration data. 173 174 If unsure, say Y if you have a Mac. Otherwise N. 175 176 config RESET_ATTACK_MITIGATION 177 bool "Reset memory attack mitigation" 178 depends on EFI_STUB 179 help 180 Request that the firmware clear the contents of RAM after a reboot 181 using the TCG Platform Reset Attack Mitigation specification. This 182 protects against an attacker forcibly rebooting the system while it 183 still contains secrets in RAM, booting another OS and extracting the 184 secrets. This should only be enabled when userland is configured to 185 clear the MemoryOverwriteRequest flag on clean shutdown after secrets 186 have been evicted, since otherwise it will trigger even on clean 187 reboots. 188 189 config EFI_RCI2_TABLE 190 bool "EFI Runtime Configuration Interface Table Version 2 Support" 191 depends on X86 || COMPILE_TEST 192 help 193 Displays the content of the Runtime Configuration Interface 194 Table version 2 on Dell EMC PowerEdge systems as a binary 195 attribute 'rci2' under /sys/firmware/efi/tables directory. 196 197 RCI2 table contains BIOS HII in XML format and is used to populate 198 BIOS setup page in Dell EMC OpenManage Server Administrator tool. 199 The BIOS setup page contains BIOS tokens which can be configured. 200 201 Say Y here for Dell EMC PowerEdge systems. 202 203 config EFI_DISABLE_PCI_DMA 204 bool "Clear Busmaster bit on PCI bridges during ExitBootServices()" 205 help 206 Disable the busmaster bit in the control register on all PCI bridges 207 while calling ExitBootServices() and passing control to the runtime 208 kernel. System firmware may configure the IOMMU to prevent malicious 209 PCI devices from being able to attack the OS via DMA. However, since 210 firmware can't guarantee that the OS is IOMMU-aware, it will tear 211 down IOMMU configuration when ExitBootServices() is called. This 212 leaves a window between where a hostile device could still cause 213 damage before Linux configures the IOMMU again. 214 215 If you say Y here, the EFI stub will clear the busmaster bit on all 216 PCI bridges before ExitBootServices() is called. This will prevent 217 any malicious PCI devices from being able to perform DMA until the 218 kernel reenables busmastering after configuring the IOMMU. 219 220 This option will cause failures with some poorly behaved hardware 221 and should not be enabled without testing. The kernel commandline 222 options "efi=disable_early_pci_dma" or "efi=no_disable_early_pci_dma" 223 may be used to override this option. 224 225 config EFI_EARLYCON 226 def_bool y 227 depends on SERIAL_EARLYCON && !ARM 228 select FONT_SUPPORT 229 select ARCH_USE_MEMREMAP_PROT 230 231 config EFI_CUSTOM_SSDT_OVERLAYS 232 bool "Load custom ACPI SSDT overlay from an EFI variable" 233 depends on ACPI 234 default ACPI_TABLE_UPGRADE 235 help 236 Allow loading of an ACPI SSDT overlay from an EFI variable specified 237 by a kernel command line option. 238 239 See Documentation/admin-guide/acpi/ssdt-overlays.rst for more 240 information. 241 242 config EFI_DISABLE_RUNTIME 243 bool "Disable EFI runtime services support by default" 244 default y if PREEMPT_RT 245 help 246 Allow to disable the EFI runtime services support by default. This can 247 already be achieved by using the efi=noruntime option, but it could be 248 useful to have this default without any kernel command line parameter. 249 250 The EFI runtime services are disabled by default when PREEMPT_RT is 251 enabled, because measurements have shown that some EFI functions calls 252 might take too much time to complete, causing large latencies which is 253 an issue for Real-Time kernels. 254 255 This default can be overridden by using the efi=runtime option. 256 257 config EFI_COCO_SECRET 258 bool "EFI Confidential Computing Secret Area Support" 259 help 260 Confidential Computing platforms (such as AMD SEV) allow the 261 Guest Owner to securely inject secrets during guest VM launch. 262 The secrets are placed in a designated EFI reserved memory area. 263 264 In order to use the secrets in the kernel, the location of the secret 265 area (as published in the EFI config table) must be kept. 266 267 If you say Y here, the address of the EFI secret area will be kept 268 for usage inside the kernel. This will allow the 269 virt/coco/efi_secret module to access the secrets, which in turn 270 allows userspace programs to access the injected secrets. 271 272 config UNACCEPTED_MEMORY 273 bool 274 depends on EFI_STUB 275 help 276 Some Virtual Machine platforms, such as Intel TDX, require 277 some memory to be "accepted" by the guest before it can be used. 278 This mechanism helps prevent malicious hosts from making changes 279 to guest memory. 280 281 UEFI specification v2.9 introduced EFI_UNACCEPTED_MEMORY memory type. 282 283 This option adds support for unaccepted memory and makes such memory 284 usable by the kernel. 285 286 config EFI_EMBEDDED_FIRMWARE 287 bool 288 select CRYPTO_LIB_SHA256 289 290 endmenu 291 292 config UEFI_CPER 293 bool 294 295 config UEFI_CPER_ARM 296 bool 297 depends on UEFI_CPER && ( ARM || ARM64 ) 298 default y 299 300 config UEFI_CPER_X86 301 bool 302 depends on UEFI_CPER && X86 303 default y 304 305 config TEE_STMM_EFI 306 tristate "TEE-based EFI runtime variable service driver" 307 depends on EFI && OPTEE 308 help 309 Select this config option if TEE is compiled to include StandAloneMM 310 as a separate secure partition. It has the ability to check and store 311 EFI variables on an RPMB or any other non-volatile medium used by 312 StandAloneMM. 313 314 Enabling this will change the EFI runtime services from the firmware 315 provided functions to TEE calls. 316 317 To compile this driver as a module, choose M here: the module 318 will be called tee_stmm_efi. 319