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Date: Tue, 9 Apr 2024 10:32:28 +0200
From: Jens Wiklander <jens.wiklander@...aro.org>
To: Avri Altman <Avri.Altman@....com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
"op-tee@...ts.trustedfirmware.org" <op-tee@...ts.trustedfirmware.org>,
Shyam Saini <shyamsaini@...ux.microsoft.com>, Ulf Hansson <ulf.hansson@...aro.org>,
Linus Walleij <linus.walleij@...aro.org>, Jerome Forissier <jerome.forissier@...aro.org>,
Sumit Garg <sumit.garg@...aro.org>, Ilias Apalodimas <ilias.apalodimas@...aro.org>,
Bart Van Assche <bvanassche@....org>, Randy Dunlap <rdunlap@...radead.org>,
Ard Biesheuvel <ardb@...nel.org>, Arnd Bergmann <arnd@...db.de>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Tomas Winkler <tomas.winkler@...el.com>,
Alex Bennée <alex.bennee@...aro.org>
Subject: Re: [PATCH v4 1/3] rpmb: add Replay Protected Memory Block (RPMB) subsystem
On Sat, Apr 6, 2024 at 12:27 PM Avri Altman <Avri.Altman@....com> wrote:
>
> > A number of storage technologies support a specialised hardware
> > partition designed to be resistant to replay attacks. The underlying
> > HW protocols differ but the operations are common. The RPMB partition
> > cannot be accessed via standard block layer, but by a set of specific
> > RPMB commands: WRITE, READ, GET_WRITE_COUNTER, and PROGRAM_KEY.
> What about the other rpmb operations?
> There are 7 operations in eMMC.
I'm sorry, I don't have access to the spec currently. Do you have a
special operation in mind? Is it better to mention no operation since
UFS has even more operations?
>
> ............
>
> > +/**
> > + * rpmb_dev_find_device() - return first matching rpmb device
> > + * @data: data for the match function
> > + * @match: the matching function
> > + *
> > + * Iterate over registered RPMB devices, and call @match() for each passing
> > + * it the RPMB device and @data.
> > + *
> > + * The return value of @match() is checked for each call. If it returns
> > + * anything other 0, break and return the found RPMB device.
> > + *
> > + * It's the callers responsibility to call rpmb_dev_put() on the returned
> > + * device, when it's done with it.
> > + *
> > + * Returns: a matching rpmb device or NULL on failure
> > + */
> > +struct rpmb_dev *rpmb_dev_find_device(const void *data,
> > + const struct rpmb_dev *start,
> > + int (*match)(struct rpmb_dev *rdev,
> > + const void *data))
> > +{
> > + struct rpmb_dev *rdev;
> > + struct list_head *pos;
> > +
> > + mutex_lock(&rpmb_mutex);
> > + if (start)
> > + pos = start->list_node.next;
> > + else
> > + pos = rpmb_dev_list.next;
> > +
> > + while (pos != &rpmb_dev_list) {
> Why not just list_for_each_entry instead?
We want to continue from where we left off last time.
>
> > + rdev = container_of(pos, struct rpmb_dev, list_node);
> > + if (match(rdev, data)) {
> > + rpmb_dev_get(rdev);
> > + goto out;
> > + }
> > + pos = pos->next;
> > + }
> > + rdev = NULL;
> > +
> > +out:
> > + mutex_unlock(&rpmb_mutex);
> > +
> > + return rdev;
> > +}
>
> .....................
>
> > +/**
> > + * rpmb_dev_register - register RPMB partition with the RPMB subsystem
> > + * @dev: storage device of the rpmb device
> > + * @ops: device specific operations
> > + *
> > + * While registering the RPMB partition extract needed device information
> > + * while needed resources are available.
> > + *
> > + * Returns: a pointer to a 'struct rpmb_dev' or an ERR_PTR on failure
> > + */
> > +struct rpmb_dev *rpmb_dev_register(struct device *dev,
> > + struct rpmb_descr *descr)
> > +{
> > + struct rpmb_dev *rdev;
> > +
> > + if (!dev || !descr || !descr->route_frames || !descr->dev_id ||
> > + !descr->dev_id_len)
> > + return ERR_PTR(-EINVAL);
> > +
> > + rdev = kzalloc(sizeof(*rdev), GFP_KERNEL);
> > + if (!rdev)
> > + return ERR_PTR(-ENOMEM);
> > + rdev->descr = *descr;
> > + rdev->descr.dev_id = kmemdup(descr->dev_id, descr->dev_id_len,
> > + GFP_KERNEL);
> In addition to the dev_id, wouldn't it make sense to have your own IDA as well?
Currently, we don't need it.
>
> > + if (!rdev->descr.dev_id) {
> > + kfree(rdev);
> > + return ERR_PTR(-ENOMEM);
> > + }
> > +
> > + rdev->parent_dev = dev;
> > +
> > + dev_dbg(rdev->parent_dev, "registered device\n");
> > +
> > + mutex_lock(&rpmb_mutex);
> > + list_add_tail(&rdev->list_node, &rpmb_dev_list);
> > + blocking_notifier_call_chain(&rpmb_interface,
> > RPMB_NOTIFY_ADD_DEVICE,
> > + rdev);
> > + mutex_unlock(&rpmb_mutex);
> > +
> > + return rdev;
> > +}
> > +EXPORT_SYMBOL_GPL(rpmb_dev_register);
>
> ............
>
> > new file mode 100644
> > index 000000000000..251d6b7e6d15
> > --- /dev/null
> > +++ b/include/linux/rpmb.h
> > @@ -0,0 +1,136 @@
> > +/* SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0 */
> > +/*
> > + * Copyright (C) 2015-2019 Intel Corp. All rights reserved
> > + * Copyright (C) 2021-2022 Linaro Ltd
> > + */
> > +#ifndef __RPMB_H__
> > +#define __RPMB_H__
> > +
> > +#include <linux/types.h>
> > +#include <linux/device.h>
> > +#include <linux/notifier.h>
> > +
> > +/**
> > + * enum rpmb_type - type of underlying storage technology
> > + *
> > + * @RPMB_TYPE_EMMC : emmc (JESD84-B50.1)
> > + * @RPMB_TYPE_UFS : UFS (JESD220)
> > + * @RPMB_TYPE_NVME : NVM Express
> > + */
> > +enum rpmb_type {
> > + RPMB_TYPE_EMMC,
> > + RPMB_TYPE_UFS,
> > + RPMB_TYPE_NVME,
> > +};
> > +
> > +/**
> > + * struct rpmb_descr - RPMB descriptor provided by the underlying block
> > device
> The use of the term "rpmb descriptor" may be slightly misleading.
> This is because in UFS there are various descriptors that identifies various characteristics,
> e.g. device descriptor, geometry descriptor, unit descriptor etc.,
> and recently UFS4.0 introduced a new descriptor - RPMB descriptor....
Would RPMB description be better? Or do you have some other idea?
Thanks,
Jens
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