linux-kernel - Re: [PATCH v2 08/11] block: sed-opal: ioctl for writing to shadow mbr

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Date:   Wed, 21 Mar 2018 02:43:21 +0100
From:   Jonas Rabenstein <jonas.rabenstein@...dium.uni-erlangen.de>
To:     Scott Bauer <scott.bauer@...el.com>
Cc:     Jonas Rabenstein <jonas.rabenstein@...dium.uni-erlangen.de>,
        Christoph Hellwig <hch@....de>,
        Jonathan Derrick <jonathan.derrick@...el.com>,
        Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 08/11] block: sed-opal: ioctl for writing to shadow mbr

On Tue, Mar 20, 2018 at 04:09:08PM -0600, Scott Bauer wrote:
> On Tue, Mar 20, 2018 at 10:36:04AM +0100, Jonas Rabenstein wrote:
> > On Mon, Mar 19, 2018 at 08:52:24PM +0100, Christoph Hellwig wrote:
> > > On Mon, Mar 19, 2018 at 07:36:50PM +0100, Jonas Rabenstein wrote:
> > > > Allow modification of the shadow mbr. If the shadow mbr is not marked as
> > > > done, this data will be presented read only as the device content. Only
> > > > after marking the shadow mbr as done and unlocking a locking range the
> > > > actual content is accessible.
> > > 
> > > I hate doing this as an ioctls.  Can we make this a sysfs binary file
> > > so that people can use dd or cat to write the shadow mbr?
> > I already thought about providing a sysfs interface for all that instead
> > of using ioctls. But as I am pretty new to kernel programming I do not
> > have all the required insight. Especially, as writing the mbr requires
> > the sed-opal password I am unsure how a clean sysfs interface to provide
> > the password together with a simple dd would look like.
> > Moreover I already have a patch that changes the 'void *data' argument
> > to setup_opal_dev to a kobject pointer. As far as I know, this is the
> > first step to get into the sysfs hierarchy. But as I do not have access
> > to an NVMe drive and have no idea about its implementation, this change
> > works only for the scsi side.
> 
> Post what you have as an RFC (review for comment) and I will test for the NVMe
> side, and or start a port for NVMe. It doesn't have to be perfect since you're
> sending it out as RFC. It's just a base for us to test/look at to see if we
> still like the sysfs way.
Seems, like I failed to make my point in the previous message. I do not
have more than adding a directory 'sed_opal' in sysfs for each sed-opal
enabled disk. But that directory is completely empty. My further plans
are, to fill up that directory with some public info like the one that
gets printed by a call to TCG's 'sedutil-cli --query' command.
The interesting part - where I am clueless how to achieve it -  would be
to have a binary sysfs attribute (like mentioned by Christoph) for the
features (like shadow mbr) requiring some kind of authentication. Until
there is any (good) idea, I do not think it is time for an RFC?

-- Jonas