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