linux/drivers/firmware/efi/Kconfig
Ard Biesheuvel 3d7ee348aa efi/libstub/arm: Add opt-in Kconfig option for the DTB loader
There are various ways a platform can provide a device tree binary
to the kernel, with different levels of sophistication:

- ideally, the UEFI firmware, which is tightly coupled with the
  platform, provides a device tree image directly as a UEFI
  configuration table, and typically permits the contents to be
  manipulated either via menu options or via UEFI environment
  variables that specify a replacement image,

- GRUB for ARM has a 'devicetree' directive which allows a device
  tree image to be loaded from any location accessible to GRUB, and
  supersede the one provided by the firmware,

- the EFI stub implements a dtb= command line option that allows a
  device tree image to be loaded from a file residing in the same
  file system as the one the kernel image was loaded from.

The dtb= command line option was never intended to be more than a
development feature, to allow the other options to be implemented
in parallel. So let's make it an opt-in feature that is disabled
by default, but can be re-enabled at will.

Note that we already disable the dtb= command line option when we
detect that we are running with UEFI Secure Boot enabled.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Alexander Graf <agraf@suse.de>
Acked-by: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20180711094040.12506-7-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-07-16 00:43:12 +02:00

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menu "EFI (Extensible Firmware Interface) Support"
depends on EFI
config EFI_VARS
tristate "EFI Variable Support via sysfs"
depends on EFI
default n
help
If you say Y here, you are able to get EFI (Extensible Firmware
Interface) variable information via sysfs. You may read,
write, create, and destroy EFI variables through this interface.
Note that using this driver in concert with efibootmgr requires
at least test release version 0.5.0-test3 or later, which is
available from:
<http://linux.dell.com/efibootmgr/testing/efibootmgr-0.5.0-test3.tar.gz>
Subsequent efibootmgr releases may be found at:
<http://github.com/vathpela/efibootmgr>
config EFI_ESRT
bool
depends on EFI && !IA64
default y
config EFI_VARS_PSTORE
tristate "Register efivars backend for pstore"
depends on EFI_VARS && PSTORE
default y
help
Say Y here to enable use efivars as a backend to pstore. This
will allow writing console messages, crash dumps, or anything
else supported by pstore to EFI variables.
config EFI_VARS_PSTORE_DEFAULT_DISABLE
bool "Disable using efivars as a pstore backend by default"
depends on EFI_VARS_PSTORE
default n
help
Saying Y here will disable the use of efivars as a storage
backend for pstore by default. This setting can be overridden
using the efivars module's pstore_disable parameter.
config EFI_RUNTIME_MAP
bool "Export efi runtime maps to sysfs"
depends on X86 && EFI && KEXEC_CORE
default y
help
Export efi runtime memory maps to /sys/firmware/efi/runtime-map.
That memory map is used for example by kexec to set up efi virtual
mapping the 2nd kernel, but can also be used for debugging purposes.
See also Documentation/ABI/testing/sysfs-firmware-efi-runtime-map.
config EFI_FAKE_MEMMAP
bool "Enable EFI fake memory map"
depends on EFI && X86
default n
help
Saying Y here will enable "efi_fake_mem" boot option.
By specifying this parameter, you can add arbitrary attribute
to specific memory range by updating original (firmware provided)
EFI memmap.
This is useful for debugging of EFI memmap related feature.
e.g. Address Range Mirroring feature.
config EFI_MAX_FAKE_MEM
int "maximum allowable number of ranges in efi_fake_mem boot option"
depends on EFI_FAKE_MEMMAP
range 1 128
default 8
help
Maximum allowable number of ranges in efi_fake_mem boot option.
Ranges can be set up to this value using comma-separated list.
The default value is 8.
config EFI_PARAMS_FROM_FDT
bool
help
Select this config option from the architecture Kconfig if
the EFI runtime support gets system table address, memory
map address, and other parameters from the device tree.
config EFI_RUNTIME_WRAPPERS
bool
config EFI_ARMSTUB
bool
config EFI_ARMSTUB_DTB_LOADER
bool "Enable the DTB loader"
depends on EFI_ARMSTUB
help
Select this config option to add support for the dtb= command
line parameter, allowing a device tree blob to be loaded into
memory from the EFI System Partition by the stub.
The device tree is typically provided by the platform or by
the bootloader, so this option is mostly for development
purposes only.
config EFI_BOOTLOADER_CONTROL
tristate "EFI Bootloader Control"
depends on EFI_VARS
default n
---help---
This module installs a reboot hook, such that if reboot() is
invoked with a string argument NNN, "NNN" is copied to the
"LoaderEntryOneShot" EFI variable, to be read by the
bootloader. If the string matches one of the boot labels
defined in its configuration, the bootloader will boot once
to that label. The "LoaderEntryRebootReason" EFI variable is
set with the reboot reason: "reboot" or "shutdown". The
bootloader reads this reboot reason and takes particular
action according to its policy.
config EFI_CAPSULE_LOADER
tristate "EFI capsule loader"
depends on EFI
help
This option exposes a loader interface "/dev/efi_capsule_loader" for
users to load EFI capsules. This driver requires working runtime
capsule support in the firmware, which many OEMs do not provide.
Most users should say N.
config EFI_CAPSULE_QUIRK_QUARK_CSH
bool "Add support for Quark capsules with non-standard headers"
depends on X86 && !64BIT
select EFI_CAPSULE_LOADER
default y
help
Add support for processing Quark X1000 EFI capsules, whose header
layout deviates from the layout mandated by the UEFI specification.
config EFI_TEST
tristate "EFI Runtime Service Tests Support"
depends on EFI
default n
help
This driver uses the efi.<service> function pointers directly instead
of going through the efivar API, because it is not trying to test the
kernel subsystem, just for testing the UEFI runtime service
interfaces which are provided by the firmware. This driver is used
by the Firmware Test Suite (FWTS) for testing the UEFI runtime
interfaces readiness of the firmware.
Details for FWTS are available from:
<https://wiki.ubuntu.com/FirmwareTestSuite>
Say Y here to enable the runtime services support via /dev/efi_test.
If unsure, say N.
config APPLE_PROPERTIES
bool "Apple Device Properties"
depends on EFI_STUB && X86
select EFI_DEV_PATH_PARSER
select UCS2_STRING
help
Retrieve properties from EFI on Apple Macs and assign them to
devices, allowing for improved support of Apple hardware.
Properties that would otherwise be missing include the
Thunderbolt Device ROM and GPU configuration data.
If unsure, say Y if you have a Mac. Otherwise N.
config RESET_ATTACK_MITIGATION
bool "Reset memory attack mitigation"
depends on EFI_STUB
help
Request that the firmware clear the contents of RAM after a reboot
using the TCG Platform Reset Attack Mitigation specification. This
protects against an attacker forcibly rebooting the system while it
still contains secrets in RAM, booting another OS and extracting the
secrets. This should only be enabled when userland is configured to
clear the MemoryOverwriteRequest flag on clean shutdown after secrets
have been evicted, since otherwise it will trigger even on clean
reboots.
endmenu
config UEFI_CPER
bool
config UEFI_CPER_ARM
bool
depends on UEFI_CPER && ( ARM || ARM64 )
default y
config UEFI_CPER_X86
bool
depends on UEFI_CPER && X86
default y
config EFI_DEV_PATH_PARSER
bool
depends on ACPI
default n