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