linux-imx/Documentation/ABI/testing/sysfs-class-firmware-attributes

What: /sys/class/firmware-attributes//attributes// Date: February 2021 KernelVersion: 5.11 Contact: Divya Bharathi Divya.Bharathi@Dell.com, Prasanth KSR prasanth.ksr@dell.com Dell.Client.Kernel@dell.com Description: A sysfs interface for systems management software to enable configuration capability on supported systems. This directory exposes interfaces for interacting with configuration options.

	Unless otherwise specified in an attribute description all attributes are optional
	and will accept UTF-8 input.

	type:
	    A file that can be read to obtain the type of attribute.
	    This attribute is mandatory.

	The following are known types:

		- enumeration: a set of pre-defined valid values
		- integer: a range of numerical values
		- string

	HP specific types
	-----------------
		- ordered-list - a set of ordered list valid values


	All attribute types support the following values:

	current_value:
			A file that can be read to obtain the current
			value of the <attr>.

			This file can also be written to in order to update the value of a
			<attr>

			This attribute is mandatory.

	default_value:
			A file that can be read to obtain the default
			value of the <attr>

	display_name:
			A file that can be read to obtain a user friendly
			description of the at <attr>

	display_name_language_code:
					A file that can be read to obtain
					the IETF language tag corresponding to the
					"display_name" of the <attr>

	"enumeration"-type specific properties:

	possible_values:
				A file that can be read to obtain the possible
				values of the <attr>. Values are separated using
				semi-colon (``;``).

	"integer"-type specific properties:

	min_value:
			A file that can be read to obtain the lower
			bound value of the <attr>

	max_value:
			A file that can be read to obtain the upper
			bound value of the <attr>

	scalar_increment:
				A file that can be read to obtain the scalar value used for
				increments of current_value this attribute accepts.

	"string"-type specific properties:

	max_length:
			A file that can be read to obtain the maximum
			length value of the <attr>

	min_length:
			A file that can be read to obtain the minimum
			length value of the <attr>

	Dell specific class extensions
	------------------------------

	On Dell systems the following additional attributes are available:

	dell_modifier:
			A file that can be read to obtain attribute-level
			dependency rule. It says an attribute X will become read-only or
			suppressed, if/if-not attribute Y is configured.

			modifier rules can be in following format::

			    [ReadOnlyIf:<attribute>=<value>]
			    [ReadOnlyIfNot:<attribute>=<value>]
			    [SuppressIf:<attribute>=<value>]
			    [SuppressIfNot:<attribute>=<value>]

			For example::

			    AutoOnFri/dell_modifier has value,
				    [SuppressIfNot:AutoOn=SelectDays]

			This means AutoOnFri will be suppressed in BIOS setup if AutoOn
			attribute is not "SelectDays" and its value will not be effective
			through sysfs until this rule is met.

	Enumeration attributes also support the following:

	dell_value_modifier:
				A file that can be read to obtain value-level dependency.
				This file is similar to dell_modifier but here,	an
				attribute's current value will be forcefully changed based
				dependent attributes value.

				dell_value_modifier rules can be in following format::

				    <value>[ForceIf:<attribute>=<value>]
				    <value>[ForceIfNot:<attribute>=<value>]

				For example::

				    LegacyOrom/dell_value_modifier has value:
					    Disabled[ForceIf:SecureBoot=Enabled]

				This means LegacyOrom's current value will be forced to
				"Disabled" in BIOS setup if SecureBoot is Enabled and its
				value will not be effective through sysfs until this rule is
				met.

	HP specific class extensions
	------------------------------

	On HP systems the following additional attributes are available:

	"ordered-list"-type specific properties:

	elements:
				A file that can be read to obtain the possible
				list of values of the <attr>. Values are separated using
				semi-colon (``;``) and listed according to their priority.
				An element listed first has the highest priority. Writing
				the list in a different order to current_value alters
				the priority order for the particular attribute.

What: /sys/class/firmware-attributes/*/authentication/ Date: February 2021 KernelVersion: 5.11 Contact: Divya Bharathi Divya.Bharathi@Dell.com, Prasanth KSR prasanth.ksr@dell.com Dell.Client.Kernel@dell.com Description: Devices support various authentication mechanisms which can be exposed as a separate configuration object.

	For example a "BIOS Admin" password and "System" Password can be set,
	reset or cleared using these attributes.

	- An "Admin" password is used for preventing modification to the BIOS
	  settings.
	- A "System" password is required to boot a machine.

	Change in any of these two authentication methods will also generate an
	uevent KOBJ_CHANGE.

	is_enabled:
				A file that can be read to obtain a 0/1 flag to see if
				<attr> authentication is enabled.
				This attribute is mandatory.

	role:
				The type of authentication used.
				This attribute is mandatory.

				Known types:
					bios-admin:
						Representing BIOS administrator password
					power-on:
						Representing a password required to use
						the system
					system-mgmt:
						Representing System Management password.
						See Lenovo extensions section for details
					HDD:
						Representing HDD password
						See Lenovo extensions section for details
					NVMe:
						Representing NVMe password
						See Lenovo extensions section for details

	mechanism:
				The means of authentication.  This attribute is mandatory.
				Only supported type currently is "password".

	max_password_length:
				A file that can be read to obtain the
				maximum length of the Password

	min_password_length:
				A file that can be read to obtain the
				minimum length of the Password

	current_password:
				A write only value used for privileged access such as
				setting	attributes when a system or admin password is set
				or resetting to a new password

				This attribute is mandatory when mechanism == "password".

	new_password:
				A write only value that when used in tandem with
				current_password will reset a system or admin password.

	Note, password management is session specific. If Admin password is set,
	same password must be written into current_password file (required for
	password-validation) and must be cleared once the session is over.
	For example::

		echo "password" > current_password
		echo "disabled" > TouchScreen/current_value
		echo "" > current_password

	Drivers may emit a CHANGE uevent when a password is set or unset
	userspace may check it again.

	On Dell, Lenovo and HP systems, if Admin password is set, then all BIOS attributes
	require password validation.
	On Lenovo systems if you change the Admin password the new password is not active until
	the next boot.

	Lenovo specific class extensions
	--------------------------------

	On Lenovo systems the following additional settings are available:

	role: system-mgmt	This gives the same authority as the bios-admin password to control
				security related features. The authorities allocated can be set via
				the BIOS menu SMP Access Control Policy

	role: HDD & NVMe	This password is used to unlock access to the drive at boot. Note see
				'level' and 'index' extensions below.

	lenovo_encoding:
				The encoding method that is used. This can be either "ascii"
				or "scancode". Default is set to "ascii"

	lenovo_kbdlang:
				The keyboard language method that is used. This is generally a
				two char code (e.g. "us", "fr", "gr") and may vary per platform.
				Default is set to "us"

	level:
				Available for HDD and NVMe authentication to set 'user' or 'master'
				privilege level.
				If only the user password is configured then this should be used to
				unlock the drive at boot. If both master and user passwords are set
				then either can be used. If a master password is set a user password
				is required.
				This attribute defaults to 'user' level

	index:
				Used with HDD and NVME authentication to set the drive index
				that is being referenced (e.g hdd1, hdd2 etc)
				This attribute defaults to device 1.

	certificate, signature, save_signature:
				These attributes are used for certificate based authentication. This is
				used in conjunction with a signing server as an alternative to password
				based authentication.
				The user writes to the attribute(s) with a BASE64 encoded string obtained
				from the signing server.
				The attributes can be displayed to check the stored value.

				Some usage examples:

					Installing a certificate to enable feature::

						echo "supervisor password" > authentication/Admin/current_password
						echo "signed certificate" > authentication/Admin/certificate

					Updating the installed certificate::

						echo "signature" > authentication/Admin/signature
						echo "signed certificate" > authentication/Admin/certificate

					Removing the installed certificate::

						echo "signature" > authentication/Admin/signature
						echo "" > authentication/Admin/certificate

					Changing a BIOS setting::

						echo "signature" > authentication/Admin/signature
						echo "save signature" > authentication/Admin/save_signature
						echo Enable > attribute/PasswordBeep/current_value

				You cannot enable certificate authentication if a supervisor password
				has not been set.
				Clearing the certificate results in no bios-admin authentication method
				being configured allowing anyone to make changes.
				After any of these operations the system must reboot for the changes to
				take effect.

	certificate_thumbprint:
				Read only attribute used to display the MD5, SHA1 and SHA256 thumbprints
				for the certificate installed in the BIOS.

	certificate_to_password:
				Write only attribute used to switch from certificate based authentication
				back to password based.
				Usage::

					echo "signature" > authentication/Admin/signature
					echo "password" > authentication/Admin/certificate_to_password

	HP specific class extensions
	--------------------------------

	On HP systems the following additional settings are available:

	role: enhanced-bios-auth:
				This role is specific to Secure Platform Management (SPM) attribute.
				It requires configuring an endorsement (kek) and signing certificate (sk).

What: /sys/class/firmware-attributes/*/attributes/pending_reboot Date: February 2021 KernelVersion: 5.11 Contact: Divya Bharathi Divya.Bharathi@Dell.com, Prasanth KSR prasanth.ksr@dell.com Dell.Client.Kernel@dell.com Description: A read-only attribute reads 1 if a reboot is necessary to apply pending BIOS attribute changes. Also, an uevent_KOBJ_CHANGE is generated when it changes to 1.

		==	=========================================
		0	All BIOS attributes setting are current
		1	A reboot is necessary to get pending BIOS
			attribute changes applied
		==	=========================================

	Note, userspace applications need to follow below steps for efficient
	BIOS management,

	1.	Check if admin password is set. If yes, follow session method for
		password management as briefed under authentication section above.
	2.	Before setting any attribute, check if it has any modifiers
		or value_modifiers. If yes, incorporate them and then modify
		attribute.

	Drivers may emit a CHANGE uevent when this value changes and userspace
	may check it again.

What: /sys/class/firmware-attributes/*/attributes/reset_bios Date: February 2021 KernelVersion: 5.11 Contact: Divya Bharathi Divya.Bharathi@Dell.com, Prasanth KSR prasanth.ksr@dell.com Dell.Client.Kernel@dell.com Description: This attribute can be used to reset the BIOS Configuration. Specifically, it tells which type of reset BIOS configuration is being requested on the host.

	Reading from it returns a list of supported options encoded as:

		- 'builtinsafe' (Built in safe configuration profile)
		- 'lastknowngood' (Last known good saved configuration profile)
		- 'factory' (Default factory settings configuration profile)
		- 'custom' (Custom saved configuration profile)

	The currently selected option is printed in square brackets as
	shown below::

	    # echo "factory" > /sys/class/firmware-attributes/*/device/attributes/reset_bios
	    # cat /sys/class/firmware-attributes/*/device/attributes/reset_bios
	    builtinsafe lastknowngood [factory] custom

	Note that any changes to this attribute requires a reboot
	for changes to take effect.

What: /sys/class/firmware-attributes/*/attributes/debug_cmd Date: July 2021 KernelVersion: 5.14 Contact: Mark Pearson markpearson@lenovo.com Description: This write only attribute can be used to send debug commands to the BIOS. This should only be used when recommended by the BIOS vendor. Vendors may use it to enable extra debug attributes or BIOS features for testing purposes.

	Note that any changes to this attribute requires a reboot for changes to take effect.


	HP specific class extensions - Secure Platform Manager (SPM)
	--------------------------------

What: /sys/class/firmware-attributes/*/authentication/SPM/kek Date: March 2023 KernelVersion: 5.18 Contact: "Jorge Lopez" jorge.lopez2@hp.com Description: 'kek' Key-Encryption-Key is a write-only file that can be used to configure the RSA public key that will be used by the BIOS to verify signatures when setting the signing key. When written, the bytes should correspond to the KEK certificate (x509 .DER format containing an OU). The size of the certificate must be less than or equal to 4095 bytes.

What: /sys/class/firmware-attributes/*/authentication/SPM/sk Date: March 2023 KernelVersion: 5.18 Contact: "Jorge Lopez" jorge.lopez2@hp.com Description: 'sk' Signature Key is a write-only file that can be used to configure the RSA public key that will be used by the BIOS to verify signatures when configuring BIOS settings and security features. When written, the bytes should correspond to the modulus of the public key. The exponent is assumed to be 0x10001.

What: /sys/class/firmware-attributes/*/authentication/SPM/status Date: March 2023 KernelVersion: 5.18 Contact: "Jorge Lopez" jorge.lopez2@hp.com Description: 'status' is a read-only file that returns ASCII text in JSON format reporting the status information.

	  "State": "not provisioned | provisioned | provisioning in progress",
	  "Version": "Major.Minor",
	  "Nonce": <16-bit unsigned number display in base 10>,
	  "FeaturesInUse": <16-bit unsigned number display in base 10>,
	  "EndorsementKeyMod": "<256 bytes in base64>",
	  "SigningKeyMod": "<256 bytes in base64>"

What: /sys/class/firmware-attributes/*/attributes/Sure_Start/audit_log_entries Date: March 2023 KernelVersion: 5.18 Contact: "Jorge Lopez" jorge.lopez2@hp.com Description: 'audit_log_entries' is a read-only file that returns the events in the log.

		Audit log entry format

		Byte 0-15:   Requested Audit Log entry  (Each Audit log is 16 bytes)
		Byte 16-127: Unused

What: /sys/class/firmware-attributes/*/attributes/Sure_Start/audit_log_entry_count Date: March 2023 KernelVersion: 5.18 Contact: "Jorge Lopez" jorge.lopez2@hp.com Description: 'audit_log_entry_count' is a read-only file that returns the number of existing audit log events available to be read. Values are separated using comma. (,)

		[No of entries],[log entry size],[Max number of entries supported]

	log entry size identifies audit log size for the current BIOS version.
	The current size is 16 bytes but it can be up to 128 bytes long in future BIOS
	versions.