1 # SPDX-License-Identifier: GPL-2.0-only
2 menu "EFI (Extensible Firmware Interface) Support"
6 tristate "EFI Variable Support via sysfs"
7 depends on EFI && (X86 || IA64)
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
19 depends on EFI && !IA64
22 config EFI_VARS_PSTORE
23 tristate "Register efivars backend for pstore"
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.
31 config EFI_VARS_PSTORE_DEFAULT_DISABLE
32 bool "Disable using efivars as a pstore backend by default"
33 depends on EFI_VARS_PSTORE
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.
40 config EFI_RUNTIME_MAP
41 bool "Export efi runtime maps to sysfs"
42 depends on X86 && EFI && KEXEC_CORE
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.
49 See also Documentation/ABI/testing/sysfs-firmware-efi-runtime-map.
51 config EFI_FAKE_MEMMAP
52 bool "Enable EFI fake memory map"
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)
60 This is useful for debugging of EFI memmap related feature.
61 e.g. Address Range Mirroring feature.
63 config EFI_MAX_FAKE_MEM
64 int "maximum allowable number of ranges in efi_fake_mem boot option"
65 depends on EFI_FAKE_MEMMAP
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.
73 config EFI_SOFT_RESERVE
74 bool "Reserve EFI Specific Purpose Memory"
75 depends on EFI && EFI_STUB && ACPI_HMAT
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.
94 config EFI_DXE_MEM_ATTRIBUTES
95 bool "Adjust memory attributes in EFISTUB"
96 depends on EFI && EFI_STUB && X86
99 UEFI specification does not guarantee all memory to be
100 accessible for both write and execute as the kernel expects
102 Use DXE services to check and alter memory protection
103 attributes during boot via EFISTUB to ensure that memory
104 ranges used by the kernel are writable and executable.
106 config EFI_PARAMS_FROM_FDT
109 Select this config option from the architecture Kconfig if
110 the EFI runtime support gets system table address, memory
111 map address, and other parameters from the device tree.
113 config EFI_RUNTIME_WRAPPERS
116 config EFI_GENERIC_STUB
119 config EFI_ARMSTUB_DTB_LOADER
120 bool "Enable the DTB loader"
121 depends on EFI_GENERIC_STUB && !RISCV
124 Select this config option to add support for the dtb= command
125 line parameter, allowing a device tree blob to be loaded into
126 memory from the EFI System Partition by the stub.
128 If the device tree is provided by the platform or by
129 the bootloader this option may not be needed.
130 But, for various development reasons and to maintain existing
131 functionality for bootloaders that do not have such support
132 this option is necessary.
134 config EFI_GENERIC_STUB_INITRD_CMDLINE_LOADER
135 bool "Enable the command line initrd loader" if !X86
136 depends on EFI_STUB && (EFI_GENERIC_STUB || X86)
140 Select this config option to add support for the initrd= command
141 line parameter, allowing an initrd that resides on the same volume
142 as the kernel image to be loaded into memory.
144 This method is deprecated.
146 config EFI_BOOTLOADER_CONTROL
147 tristate "EFI Bootloader Control"
150 This module installs a reboot hook, such that if reboot() is
151 invoked with a string argument NNN, "NNN" is copied to the
152 "LoaderEntryOneShot" EFI variable, to be read by the
153 bootloader. If the string matches one of the boot labels
154 defined in its configuration, the bootloader will boot once
155 to that label. The "LoaderEntryRebootReason" EFI variable is
156 set with the reboot reason: "reboot" or "shutdown". The
157 bootloader reads this reboot reason and takes particular
158 action according to its policy.
160 config EFI_CAPSULE_LOADER
161 tristate "EFI capsule loader"
162 depends on EFI && !IA64
164 This option exposes a loader interface "/dev/efi_capsule_loader" for
165 users to load EFI capsules. This driver requires working runtime
166 capsule support in the firmware, which many OEMs do not provide.
168 Most users should say N.
170 config EFI_CAPSULE_QUIRK_QUARK_CSH
171 bool "Add support for Quark capsules with non-standard headers"
172 depends on X86 && !64BIT
173 select EFI_CAPSULE_LOADER
176 Add support for processing Quark X1000 EFI capsules, whose header
177 layout deviates from the layout mandated by the UEFI specification.
180 tristate "EFI Runtime Service Tests Support"
184 This driver uses the efi.<service> function pointers directly instead
185 of going through the efivar API, because it is not trying to test the
186 kernel subsystem, just for testing the UEFI runtime service
187 interfaces which are provided by the firmware. This driver is used
188 by the Firmware Test Suite (FWTS) for testing the UEFI runtime
189 interfaces readiness of the firmware.
190 Details for FWTS are available from:
191 <https://wiki.ubuntu.com/FirmwareTestSuite>
193 Say Y here to enable the runtime services support via /dev/efi_test.
196 config EFI_DEV_PATH_PARSER
199 config APPLE_PROPERTIES
200 bool "Apple Device Properties"
201 depends on EFI_STUB && X86
202 select EFI_DEV_PATH_PARSER
205 Retrieve properties from EFI on Apple Macs and assign them to
206 devices, allowing for improved support of Apple hardware.
207 Properties that would otherwise be missing include the
208 Thunderbolt Device ROM and GPU configuration data.
210 If unsure, say Y if you have a Mac. Otherwise N.
212 config RESET_ATTACK_MITIGATION
213 bool "Reset memory attack mitigation"
216 Request that the firmware clear the contents of RAM after a reboot
217 using the TCG Platform Reset Attack Mitigation specification. This
218 protects against an attacker forcibly rebooting the system while it
219 still contains secrets in RAM, booting another OS and extracting the
220 secrets. This should only be enabled when userland is configured to
221 clear the MemoryOverwriteRequest flag on clean shutdown after secrets
222 have been evicted, since otherwise it will trigger even on clean
225 config EFI_RCI2_TABLE
226 bool "EFI Runtime Configuration Interface Table Version 2 Support"
227 depends on X86 || COMPILE_TEST
229 Displays the content of the Runtime Configuration Interface
230 Table version 2 on Dell EMC PowerEdge systems as a binary
231 attribute 'rci2' under /sys/firmware/efi/tables directory.
233 RCI2 table contains BIOS HII in XML format and is used to populate
234 BIOS setup page in Dell EMC OpenManage Server Administrator tool.
235 The BIOS setup page contains BIOS tokens which can be configured.
237 Say Y here for Dell EMC PowerEdge systems.
239 config EFI_DISABLE_PCI_DMA
240 bool "Clear Busmaster bit on PCI bridges during ExitBootServices()"
242 Disable the busmaster bit in the control register on all PCI bridges
243 while calling ExitBootServices() and passing control to the runtime
244 kernel. System firmware may configure the IOMMU to prevent malicious
245 PCI devices from being able to attack the OS via DMA. However, since
246 firmware can't guarantee that the OS is IOMMU-aware, it will tear
247 down IOMMU configuration when ExitBootServices() is called. This
248 leaves a window between where a hostile device could still cause
249 damage before Linux configures the IOMMU again.
251 If you say Y here, the EFI stub will clear the busmaster bit on all
252 PCI bridges before ExitBootServices() is called. This will prevent
253 any malicious PCI devices from being able to perform DMA until the
254 kernel reenables busmastering after configuring the IOMMU.
256 This option will cause failures with some poorly behaved hardware
257 and should not be enabled without testing. The kernel commandline
258 options "efi=disable_early_pci_dma" or "efi=no_disable_early_pci_dma"
259 may be used to override this option.
263 depends on SERIAL_EARLYCON && !ARM && !IA64
265 select ARCH_USE_MEMREMAP_PROT
267 config EFI_CUSTOM_SSDT_OVERLAYS
268 bool "Load custom ACPI SSDT overlay from an EFI variable"
270 default ACPI_TABLE_UPGRADE
272 Allow loading of an ACPI SSDT overlay from an EFI variable specified
273 by a kernel command line option.
275 See Documentation/admin-guide/acpi/ssdt-overlays.rst for more
278 config EFI_DISABLE_RUNTIME
279 bool "Disable EFI runtime services support by default"
280 default y if PREEMPT_RT
282 Allow to disable the EFI runtime services support by default. This can
283 already be achieved by using the efi=noruntime option, but it could be
284 useful to have this default without any kernel command line parameter.
286 The EFI runtime services are disabled by default when PREEMPT_RT is
287 enabled, because measurements have shown that some EFI functions calls
288 might take too much time to complete, causing large latencies which is
289 an issue for Real-Time kernels.
291 This default can be overridden by using the efi=runtime option.
293 config EFI_COCO_SECRET
294 bool "EFI Confidential Computing Secret Area Support"
296 Confidential Computing platforms (such as AMD SEV) allow the
297 Guest Owner to securely inject secrets during guest VM launch.
298 The secrets are placed in a designated EFI reserved memory area.
300 In order to use the secrets in the kernel, the location of the secret
301 area (as published in the EFI config table) must be kept.
303 If you say Y here, the address of the EFI secret area will be kept
304 for usage inside the kernel. This will allow the
305 virt/coco/efi_secret module to access the secrets, which in turn
306 allows userspace programs to access the injected secrets.
308 config EFI_EMBEDDED_FIRMWARE
310 select CRYPTO_LIB_SHA256
319 depends on UEFI_CPER && ( ARM || ARM64 )
324 depends on UEFI_CPER && X86