Re: [WIP RFC PATCH 0/6] Generic Firmware Variable Filesystem

[Nayna <nayna@linux.vnet.ibm.com>]

On 06/03/2019 07:56 PM, Daniel Axtens wrote:
>
>> I would just recommend putting this in sysfs.  Make a new subsystem
>> (i.e. class) and away you go.
>>
>>> My hope with fwvarfs is to provide a generic place for firmware
>>> variables so that we don't need to expand the list of firmware-specific
>>> filesystems beyond efivarfs. I am also aiming to make things simple to
>>> use so that people familiar with firmware don't also have to become
>>> familiar with filesystem code in order to expose firmware variables to
>>> userspace.
>>> fwvarfs can also be used for variables that are not security relevant as
>>> well. For example, with the EFI backend (patch 3), both secure and
>>> insecure variables can be read.
>> I don't remember why efi variables were not put in sysfs, I think there
>> was some reasoning behind it originally.  Perhaps look in the linux-efi
>> archives.
> I'll have a look: I suspect the appeal of efivarfs is that it allows for
> things like non-case-sensitive matching on the GUID part of the filename
> while retaining case-sensitivity on the part of the filename
> representing the variable name.

It seems efivars were first implemented in sysfs and then later 
separated out as efivarfs.
Refer - Documentation/filesystems/efivarfs.txt.

So, the reason wasn't that sysfs should not be used for exposing 
firmware variables,
but for the size limitations which seems to come from UEFI Specification.

Is this limitation valid for the new requirement of secure variables ?

Copying Matthew who can give us more insights...

Thanks & Regards,
      - Nayna