tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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 if X86
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 && !IA64
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 EFI && 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.