1# SPDX-License-Identifier: GPL-2.0-only 2menu "EFI (Extensible Firmware Interface) Support" 3 depends on EFI 4 5config EFI_VARS 6 tristate "EFI Variable Support via sysfs" 7 depends on EFI && (X86 || IA64) 8 default n 9 help 10 If you say Y here, you are able to get EFI (Extensible Firmware 11 Interface) variable information via sysfs. You may read, 12 write, create, and destroy EFI variables through this interface. 13 Note that this driver is only retained for compatibility with 14 legacy users: new users should use the efivarfs filesystem 15 instead. 16 17config EFI_ESRT 18 bool 19 depends on EFI && !IA64 20 default y 21 22config EFI_VARS_PSTORE 23 tristate "Register efivars backend for pstore" 24 depends on PSTORE 25 default y 26 help 27 Say Y here to enable use efivars as a backend to pstore. This 28 will allow writing console messages, crash dumps, or anything 29 else supported by pstore to EFI variables. 30 31config EFI_VARS_PSTORE_DEFAULT_DISABLE 32 bool "Disable using efivars as a pstore backend by default" 33 depends on EFI_VARS_PSTORE 34 default n 35 help 36 Saying Y here will disable the use of efivars as a storage 37 backend for pstore by default. This setting can be overridden 38 using the efivars module's pstore_disable parameter. 39 40config EFI_RUNTIME_MAP 41 bool "Export efi runtime maps to sysfs" 42 depends on X86 && EFI && KEXEC_CORE 43 default y 44 help 45 Export efi runtime memory maps to /sys/firmware/efi/runtime-map. 46 That memory map is used for example by kexec to set up efi virtual 47 mapping the 2nd kernel, but can also be used for debugging purposes. 48 49 See also Documentation/ABI/testing/sysfs-firmware-efi-runtime-map. 50 51config EFI_FAKE_MEMMAP 52 bool "Enable EFI fake memory map" 53 depends on EFI && X86 54 default n 55 help 56 Saying Y here will enable "efi_fake_mem" boot option. 57 By specifying this parameter, you can add arbitrary attribute 58 to specific memory range by updating original (firmware provided) 59 EFI memmap. 60 This is useful for debugging of EFI memmap related feature. 61 e.g. Address Range Mirroring feature. 62 63config EFI_MAX_FAKE_MEM 64 int "maximum allowable number of ranges in efi_fake_mem boot option" 65 depends on EFI_FAKE_MEMMAP 66 range 1 128 67 default 8 68 help 69 Maximum allowable number of ranges in efi_fake_mem boot option. 70 Ranges can be set up to this value using comma-separated list. 71 The default value is 8. 72 73config EFI_SOFT_RESERVE 74 bool "Reserve EFI Specific Purpose Memory" 75 depends on EFI && EFI_STUB && ACPI_HMAT 76 default ACPI_HMAT 77 help 78 On systems that have mixed performance classes of memory EFI 79 may indicate specific purpose memory with an attribute (See 80 EFI_MEMORY_SP in UEFI 2.8). A memory range tagged with this 81 attribute may have unique performance characteristics compared 82 to the system's general purpose "System RAM" pool. On the 83 expectation that such memory has application specific usage, 84 and its base EFI memory type is "conventional" answer Y to 85 arrange for the kernel to reserve it as a "Soft Reserved" 86 resource, and set aside for direct-access (device-dax) by 87 default. The memory range can later be optionally assigned to 88 the page allocator by system administrator policy via the 89 device-dax kmem facility. Say N to have the kernel treat this 90 memory as "System RAM" by default. 91 92 If unsure, say Y. 93 94config EFI_PARAMS_FROM_FDT 95 bool 96 help 97 Select this config option from the architecture Kconfig if 98 the EFI runtime support gets system table address, memory 99 map address, and other parameters from the device tree. 100 101config EFI_RUNTIME_WRAPPERS 102 bool 103 104config EFI_GENERIC_STUB 105 bool 106 107config EFI_ARMSTUB_DTB_LOADER 108 bool "Enable the DTB loader" 109 depends on EFI_GENERIC_STUB && !RISCV 110 default y 111 help 112 Select this config option to add support for the dtb= command 113 line parameter, allowing a device tree blob to be loaded into 114 memory from the EFI System Partition by the stub. 115 116 If the device tree is provided by the platform or by 117 the bootloader this option may not be needed. 118 But, for various development reasons and to maintain existing 119 functionality for bootloaders that do not have such support 120 this option is necessary. 121 122config EFI_GENERIC_STUB_INITRD_CMDLINE_LOADER 123 bool "Enable the command line initrd loader" if !X86 124 depends on EFI_STUB && (EFI_GENERIC_STUB || X86) 125 default y 126 depends on !RISCV 127 help 128 Select this config option to add support for the initrd= command 129 line parameter, allowing an initrd that resides on the same volume 130 as the kernel image to be loaded into memory. 131 132 This method is deprecated. 133 134config EFI_BOOTLOADER_CONTROL 135 tristate "EFI Bootloader Control" 136 default n 137 help 138 This module installs a reboot hook, such that if reboot() is 139 invoked with a string argument NNN, "NNN" is copied to the 140 "LoaderEntryOneShot" EFI variable, to be read by the 141 bootloader. If the string matches one of the boot labels 142 defined in its configuration, the bootloader will boot once 143 to that label. The "LoaderEntryRebootReason" EFI variable is 144 set with the reboot reason: "reboot" or "shutdown". The 145 bootloader reads this reboot reason and takes particular 146 action according to its policy. 147 148config EFI_CAPSULE_LOADER 149 tristate "EFI capsule loader" 150 depends on EFI 151 help 152 This option exposes a loader interface "/dev/efi_capsule_loader" for 153 users to load EFI capsules. This driver requires working runtime 154 capsule support in the firmware, which many OEMs do not provide. 155 156 Most users should say N. 157 158config EFI_CAPSULE_QUIRK_QUARK_CSH 159 bool "Add support for Quark capsules with non-standard headers" 160 depends on X86 && !64BIT 161 select EFI_CAPSULE_LOADER 162 default y 163 help 164 Add support for processing Quark X1000 EFI capsules, whose header 165 layout deviates from the layout mandated by the UEFI specification. 166 167config EFI_TEST 168 tristate "EFI Runtime Service Tests Support" 169 depends on EFI 170 default n 171 help 172 This driver uses the efi.<service> function pointers directly instead 173 of going through the efivar API, because it is not trying to test the 174 kernel subsystem, just for testing the UEFI runtime service 175 interfaces which are provided by the firmware. This driver is used 176 by the Firmware Test Suite (FWTS) for testing the UEFI runtime 177 interfaces readiness of the firmware. 178 Details for FWTS are available from: 179 <https://wiki.ubuntu.com/FirmwareTestSuite> 180 181 Say Y here to enable the runtime services support via /dev/efi_test. 182 If unsure, say N. 183 184config APPLE_PROPERTIES 185 bool "Apple Device Properties" 186 depends on EFI_STUB && X86 187 select EFI_DEV_PATH_PARSER 188 select UCS2_STRING 189 help 190 Retrieve properties from EFI on Apple Macs and assign them to 191 devices, allowing for improved support of Apple hardware. 192 Properties that would otherwise be missing include the 193 Thunderbolt Device ROM and GPU configuration data. 194 195 If unsure, say Y if you have a Mac. Otherwise N. 196 197config RESET_ATTACK_MITIGATION 198 bool "Reset memory attack mitigation" 199 depends on EFI_STUB 200 help 201 Request that the firmware clear the contents of RAM after a reboot 202 using the TCG Platform Reset Attack Mitigation specification. This 203 protects against an attacker forcibly rebooting the system while it 204 still contains secrets in RAM, booting another OS and extracting the 205 secrets. This should only be enabled when userland is configured to 206 clear the MemoryOverwriteRequest flag on clean shutdown after secrets 207 have been evicted, since otherwise it will trigger even on clean 208 reboots. 209 210config EFI_RCI2_TABLE 211 bool "EFI Runtime Configuration Interface Table Version 2 Support" 212 depends on X86 || COMPILE_TEST 213 help 214 Displays the content of the Runtime Configuration Interface 215 Table version 2 on Dell EMC PowerEdge systems as a binary 216 attribute 'rci2' under /sys/firmware/efi/tables directory. 217 218 RCI2 table contains BIOS HII in XML format and is used to populate 219 BIOS setup page in Dell EMC OpenManage Server Administrator tool. 220 The BIOS setup page contains BIOS tokens which can be configured. 221 222 Say Y here for Dell EMC PowerEdge systems. 223 224config EFI_DISABLE_PCI_DMA 225 bool "Clear Busmaster bit on PCI bridges during ExitBootServices()" 226 help 227 Disable the busmaster bit in the control register on all PCI bridges 228 while calling ExitBootServices() and passing control to the runtime 229 kernel. System firmware may configure the IOMMU to prevent malicious 230 PCI devices from being able to attack the OS via DMA. However, since 231 firmware can't guarantee that the OS is IOMMU-aware, it will tear 232 down IOMMU configuration when ExitBootServices() is called. This 233 leaves a window between where a hostile device could still cause 234 damage before Linux configures the IOMMU again. 235 236 If you say Y here, the EFI stub will clear the busmaster bit on all 237 PCI bridges before ExitBootServices() is called. This will prevent 238 any malicious PCI devices from being able to perform DMA until the 239 kernel reenables busmastering after configuring the IOMMU. 240 241 This option will cause failures with some poorly behaved hardware 242 and should not be enabled without testing. The kernel commandline 243 options "efi=disable_early_pci_dma" or "efi=no_disable_early_pci_dma" 244 may be used to override this option. 245 246endmenu 247 248config EFI_EMBEDDED_FIRMWARE 249 bool 250 depends on EFI 251 select CRYPTO_LIB_SHA256 252 253config UEFI_CPER 254 bool 255 256config UEFI_CPER_ARM 257 bool 258 depends on UEFI_CPER && ( ARM || ARM64 ) 259 default y 260 261config UEFI_CPER_X86 262 bool 263 depends on UEFI_CPER && X86 264 default y 265 266config EFI_DEV_PATH_PARSER 267 bool 268 depends on ACPI 269 default n 270 271config EFI_EARLYCON 272 def_bool y 273 depends on SERIAL_EARLYCON && !ARM && !IA64 274 select FONT_SUPPORT 275 select ARCH_USE_MEMREMAP_PROT 276 277config EFI_CUSTOM_SSDT_OVERLAYS 278 bool "Load custom ACPI SSDT overlay from an EFI variable" 279 depends on EFI && ACPI 280 default ACPI_TABLE_UPGRADE 281 help 282 Allow loading of an ACPI SSDT overlay from an EFI variable specified 283 by a kernel command line option. 284 285 See Documentation/admin-guide/acpi/ssdt-overlays.rst for more 286 information. 287