linux/Documentation/ABI/testing/sysfs-secvar
Nayna Jain bd5d9c743d powerpc: expose secure variables to userspace via sysfs
PowerNV secure variables, which store the keys used for OS kernel
verification, are managed by the firmware. These secure variables need to
be accessed by the userspace for addition/deletion of the certificates.

This patch adds the sysfs interface to expose secure variables for PowerNV
secureboot. The users shall use this interface for manipulating
the keys stored in the secure variables.

Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Eric Richter <erichte@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1573441836-3632-3-git-send-email-nayna@linux.ibm.com
2019-11-13 00:33:22 +11:00

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What: /sys/firmware/secvar
Date: August 2019
Contact: Nayna Jain <nayna@linux.ibm.com>
Description: This directory is created if the POWER firmware supports OS
secureboot, thereby secure variables. It exposes interface
for reading/writing the secure variables
What: /sys/firmware/secvar/vars
Date: August 2019
Contact: Nayna Jain <nayna@linux.ibm.com>
Description: This directory lists all the secure variables that are supported
by the firmware.
What: /sys/firmware/secvar/format
Date: August 2019
Contact: Nayna Jain <nayna@linux.ibm.com>
Description: A string indicating which backend is in use by the firmware.
This determines the format of the variable and the accepted
format of variable updates.
What: /sys/firmware/secvar/vars/<variable name>
Date: August 2019
Contact: Nayna Jain <nayna@linux.ibm.com>
Description: Each secure variable is represented as a directory named as
<variable_name>. The variable name is unique and is in ASCII
representation. The data and size can be determined by reading
their respective attribute files.
What: /sys/firmware/secvar/vars/<variable_name>/size
Date: August 2019
Contact: Nayna Jain <nayna@linux.ibm.com>
Description: An integer representation of the size of the content of the
variable. In other words, it represents the size of the data.
What: /sys/firmware/secvar/vars/<variable_name>/data
Date: August 2019
Contact: Nayna Jain h<nayna@linux.ibm.com>
Description: A read-only file containing the value of the variable. The size
of the file represents the maximum size of the variable data.
What: /sys/firmware/secvar/vars/<variable_name>/update
Date: August 2019
Contact: Nayna Jain <nayna@linux.ibm.com>
Description: A write-only file that is used to submit the new value for the
variable. The size of the file represents the maximum size of
the variable data that can be written.