Date:   Sun, 25 Oct 2020 12:12:52 -0700
From:   Moritz Fischer <mdf@...nel.org>
To:     Russ Weight <russell.h.weight@...el.com>
Cc:     mdf@...nel.org, linux-fpga@...r.kernel.org,
        linux-kernel@...r.kernel.org, trix@...hat.com, lgoncalv@...hat.com,
        yilun.xu@...el.com, hao.wu@...el.com, matthew.gerlach@...el.com
Subject: Re: [PATCH v5 1/7] fpga: sec-mgr: intel fpga security manager class
 driver

Hi Russ,

On Tue, Oct 20, 2020 at 05:31:12PM -0700, Russ Weight wrote:
> I see that I need to remove "intel" from the subject line on this patch.
> I'll take care of that.
> 
> I still have an outstanding question about treating a class-driver as a
> managed resource of the parent device. I'm reposting the question inline.

Yes please.
> 
> On 10/20/20 5:16 PM, Russ Weight wrote:
> > Create the FPGA Security Manager class driver. The security
> > manager provides interfaces to manage secure updates for the
> > FPGA and BMC images that are stored in FLASH. The driver can
> > also be used to update root entry hashes and to cancel code
> > signing keys.
> >
> > This patch creates the class driver and provides sysfs
> > interfaces for displaying root entry hashes, canceled code
> > signing keys and flash counts.
> >
> > Signed-off-by: Russ Weight <russell.h.weight@...el.com>
> > Signed-off-by: Xu Yilun <yilun.xu@...el.com>
> > Reviewed-by: Tom Rix <trix@...hat.com>
> > ---
> > v5:
> >   - Added the devm_fpga_sec_mgr_unregister() function, following recent
> >     changes to the fpga_manager() implementation.
> >   - Changed some *_show() functions to use sysfs_emit() instead of sprintf(
> > v4:
> >   - Changed from "Intel FPGA Security Manager" to FPGA Security Manager"
> >     and removed unnecessary references to "Intel".
> >   - Changed: iops -> sops, imgr -> smgr, IFPGA_ -> FPGA_, ifpga_ to fpga_
> > v3:
> >   - Modified sysfs handler check in check_sysfs_handler() to make
> >     it more readable.
> > v2:
> >   - Bumped documentation dates and versions
> >   - Added Documentation/fpga/ifpga-sec-mgr.rst 
> >   - Removed references to bmc_flash_count & smbus_flash_count (not supported)
> >   - Split ifpga_sec_mgr_register() into create() and register() functions
> >   - Added devm_ifpga_sec_mgr_create()
> >   - Removed typedefs for imgr ops
> > ---
> >  .../ABI/testing/sysfs-class-fpga-sec-mgr      |  67 +++
> >  Documentation/fpga/fpga-sec-mgr.rst           |  50 ++
> >  Documentation/fpga/index.rst                  |   1 +
> >  MAINTAINERS                                   |   9 +
> >  drivers/fpga/Kconfig                          |   9 +
> >  drivers/fpga/Makefile                         |   3 +
> >  drivers/fpga/fpga-sec-mgr.c                   | 487 ++++++++++++++++++
> >  include/linux/fpga/fpga-sec-mgr.h             |  83 +++
> >  8 files changed, 709 insertions(+)
> >  create mode 100644 Documentation/ABI/testing/sysfs-class-fpga-sec-mgr
> >  create mode 100644 Documentation/fpga/fpga-sec-mgr.rst
> >  create mode 100644 drivers/fpga/fpga-sec-mgr.c
> >  create mode 100644 include/linux/fpga/fpga-sec-mgr.h
> >
> > diff --git a/Documentation/ABI/testing/sysfs-class-fpga-sec-mgr b/Documentation/ABI/testing/sysfs-class-fpga-sec-mgr
> > new file mode 100644
> > index 000000000000..843f0b58f171
> > --- /dev/null
> > +++ b/Documentation/ABI/testing/sysfs-class-fpga-sec-mgr
> > @@ -0,0 +1,67 @@
> > +What: 		/sys/class/fpga_sec_mgr/fpga_secX/name
> > +Date:		Oct 2020
> > +KernelVersion:  5.11
> > +Contact:	Russ Weight <russell.h.weight@...el.com>
> > +Description:	Name of low level fpga security manager driver.
> > +
> > +What: 		/sys/class/fpga_sec_mgr/fpga_secX/security/sr_root_entry_hash
> > +Date:		Oct 2020
> > +KernelVersion:  5.11
> > +Contact:	Russ Weight <russell.h.weight@...el.com>
> > +Description:	Read only. Returns the root entry hash for the static
> > +		region if one is programmed, else it returns the
> > +		string: "hash not programmed".  This file is only
> > +		visible if the underlying device supports it.
> > +		Format: "0x%x".
> > +
> > +What: 		/sys/class/fpga_sec_mgr/fpga_secX/security/pr_root_entry_hash
> > +Date:		Oct 2020
> > +KernelVersion:  5.11
> > +Contact:	Russ Weight <russell.h.weight@...el.com>
> > +Description:	Read only. Returns the root entry hash for the partial
> > +		reconfiguration region if one is programmed, else it
> > +		returns the string: "hash not programmed".  This file
> > +		is only visible if the underlying device supports it.
> > +		Format: "0x%x".
> > +
> > +What: 		/sys/class/fpga_sec_mgr/fpga_secX/security/bmc_root_entry_hash
> > +Date:		Oct 2020
> > +KernelVersion:  5.11
> > +Contact:	Russ Weight <russell.h.weight@...el.com>
> > +Description:	Read only. Returns the root entry hash for the BMC image
> > +		if one is programmed, else it returns the string:
> > +		"hash not programmed".  This file is only visible if the
> > +		underlying device supports it.
> > +		Format: "0x%x".
> > +
> > +What: 		/sys/class/fpga_sec_mgr/fpga_secX/security/sr_canceled_csks
> > +Date:		Oct 2020
> > +KernelVersion:  5.11
> > +Contact:	Russ Weight <russell.h.weight@...el.com>
> > +Description:	Read only. Returns a list of indices for canceled code
> > +		signing keys for the static region. The standard bitmap
> > +		list format is used (e.g. "1,2-6,9").
> > +
> > +What: 		/sys/class/fpga_sec_mgr/fpga_secX/security/pr_canceled_csks
> > +Date:		Oct 2020
> > +KernelVersion:  5.11
> > +Contact:	Russ Weight <russell.h.weight@...el.com>
> > +Description:	Read only. Returns a list of indices for canceled code
> > +		signing keys for the partial reconfiguration region. The
> > +		standard bitmap list format is used (e.g. "1,2-6,9").
> > +
> > +What: 		/sys/class/fpga_sec_mgr/fpga_secX/security/bmc_canceled_csks
> > +Date:		Oct 2020
> > +KernelVersion:  5.11
> > +Contact:	Russ Weight <russell.h.weight@...el.com>
> > +Description:	Read only. Returns a list of indices for canceled code
> > +		signing keys for the BMC.  The standard bitmap list format
> > +		is used (e.g. "1,2-6,9").
> > +
> > +What: 		/sys/class/fpga_sec_mgr/fpga_secX/security/user_flash_count
> > +Date:		Oct 2020
> > +KernelVersion:  5.11
> > +Contact:	Russ Weight <russell.h.weight@...el.com>
> > +Description:	Read only. Returns number of times the user image for the
> > +		static region has been flashed.
> > +		Format: "%u".
> > diff --git a/Documentation/fpga/fpga-sec-mgr.rst b/Documentation/fpga/fpga-sec-mgr.rst
> > new file mode 100644
> > index 000000000000..4a1d6519b1d3
> > --- /dev/null
> > +++ b/Documentation/fpga/fpga-sec-mgr.rst
> > @@ -0,0 +1,50 @@
> > +.. SPDX-License-Identifier: GPL-2.0
> > +
> > +========================================
> > +FPGA Security Manager Class Driver
> > +========================================
> > +
> > +The FPGA Security Manager class driver provides a common
> > +API for user-space tools to manage updates for secure FPGA
> > +devices. Device drivers that instantiate the Security
> > +Manager class driver will interact with a HW secure update
> > +engine in order to transfer new FPGA and BMC images to FLASH so
> > +that they will be automatically loaded when the FPGA card reboots.
> > +
> > +A significant difference between the FPGA Manager and the FPGA
> > +Security Manager is that the FPGA Manager does a live update (Partial
> > +Reconfiguration) to a device, whereas the FPGA Security Manager
> > +updates the FLASH images for the Static Region and the BMC so that
> > +they will be loaded the next time the FPGA card boots. Security is
> > +enforced by hardware and firmware. The security manager interacts
> > +with the firmware to initiate an update, pass in the necessary data,
> > +and collect status on the update.
> > +
> > +In addition to managing secure updates of the FPGA and BMC images,
> > +the FPGA Security Manager update process may also used to
> > +program root entry hashes and cancellation keys for the FPGA static
> > +region, the FPGA partial reconfiguration region, and the BMC.
> > +
> > +Secure updates make use of the request_firmware framework, which
> > +requires that image files are accessible under /lib/firmware. A request
> > +for a secure update returns immediately, while the update itself
> > +proceeds in the context of a kernel worker thread. Sysfs files provide
> > +a means for monitoring the progress of a secure update and for
> > +retrieving error information in the event of a failure.
> > +
> > +Sysfs Attributes
> > +================
> > +
> > +The API consists of two groups of sysfs attributes as described below.
> > +
> > +1. Files in the *security* sub-directory can be used to read security
> > +   information including: Root Entry Hashes (REH), Cancelled Code
> > +   Signing Keys (CSK), and the flash update count for FPGA images.
> > +
> > +2. Files in the *update* sub-directory can be used to instantiate and
> > +   monitor a secure update.
> > +
> > +
> > +See `<../ABI/testing/sysfs-class-fpga-sec-mgr>`__ for a full
> > +description of the sysfs attributes for the FPGA Security
> > +Manager.
> > diff --git a/Documentation/fpga/index.rst b/Documentation/fpga/index.rst
> > index f80f95667ca2..0b2f427042af 100644
> > --- a/Documentation/fpga/index.rst
> > +++ b/Documentation/fpga/index.rst
> > @@ -8,6 +8,7 @@ fpga
> >      :maxdepth: 1
> >  
> >      dfl
> > +    fpga-sec-mgr
> >  
> >  .. only::  subproject and html
> >  
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 4538378de6f5..7997fff716a8 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -6901,6 +6901,15 @@ F:	Documentation/fpga/
> >  F:	drivers/fpga/
> >  F:	include/linux/fpga/
> >  
> > +FPGA SECURITY MANAGER DRIVERS
> > +M:	Russ Weight <russell.h.weight@...el.com>
> > +L:	linux-fpga@...r.kernel.org
> > +S:	Maintained
> > +F:	Documentation/ABI/testing/sysfs-class-fpga-sec-mgr
> > +F:	Documentation/fpga/fpga-sec-mgr.rst
> > +F:	drivers/fpga/fpga-sec-mgr.c
> > +F:	include/linux/fpga/fpga-sec-mgr.h
> > +
> >  FPU EMULATOR
> >  M:	Bill Metzenthen <billm@...bpc.org.au>
> >  S:	Maintained
> > diff --git a/drivers/fpga/Kconfig b/drivers/fpga/Kconfig
> > index 7cd5a29fc437..6810b23b178d 100644
> > --- a/drivers/fpga/Kconfig
> > +++ b/drivers/fpga/Kconfig
> > @@ -215,4 +215,13 @@ config FPGA_MGR_ZYNQMP_FPGA
> >  	  to configure the programmable logic(PL) through PS
> >  	  on ZynqMP SoC.
> >  
> > +config FPGA_SEC_MGR
> > +	tristate "FPGA Security Manager"
> > +	help
> > +	  The Security Manager class driver presents a common
> > +	  user API for managing secure updates for FPGA
> > +	  devices, including flash images for the FPGA static
> > +	  region and for the BMC. Select this option to enable
> > +	  updates for secure FPGA devices.
> > +
> >  endif # FPGA
> > diff --git a/drivers/fpga/Makefile b/drivers/fpga/Makefile
> > index d8e21dfc6778..0e357262faed 100644
> > --- a/drivers/fpga/Makefile
> > +++ b/drivers/fpga/Makefile
> > @@ -21,6 +21,9 @@ obj-$(CONFIG_FPGA_MGR_ZYNQMP_FPGA)	+= zynqmp-fpga.o
> >  obj-$(CONFIG_ALTERA_PR_IP_CORE)         += altera-pr-ip-core.o
> >  obj-$(CONFIG_ALTERA_PR_IP_CORE_PLAT)    += altera-pr-ip-core-plat.o
> >  
> > +# FPGA Security Manager Framework
> > +obj-$(CONFIG_FPGA_SEC_MGR)		+= fpga-sec-mgr.o
> > +
> >  # FPGA Bridge Drivers
> >  obj-$(CONFIG_FPGA_BRIDGE)		+= fpga-bridge.o
> >  obj-$(CONFIG_SOCFPGA_FPGA_BRIDGE)	+= altera-hps2fpga.o altera-fpga2sdram.o
> > diff --git a/drivers/fpga/fpga-sec-mgr.c b/drivers/fpga/fpga-sec-mgr.c
> > new file mode 100644
> > index 000000000000..95b5a7ccbe44
> > --- /dev/null
> > +++ b/drivers/fpga/fpga-sec-mgr.c
> > @@ -0,0 +1,487 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * FPGA Security Manager
> > + *
> > + * Copyright (C) 2019-2020 Intel Corporation, Inc.
> > + */
> > +
> > +#include <linux/fpga/fpga-sec-mgr.h>
> > +#include <linux/idr.h>
> > +#include <linux/module.h>
> > +#include <linux/slab.h>
> > +#include <linux/vmalloc.h>
> > +
> > +static DEFINE_IDA(fpga_sec_mgr_ida);
> > +static struct class *fpga_sec_mgr_class;
> > +
> > +struct fpga_sec_mgr_devres {
> > +	struct fpga_sec_mgr *smgr;
> > +};
> > +
> > +#define to_sec_mgr(d) container_of(d, struct fpga_sec_mgr, dev)
> > +
> > +static ssize_t
> > +show_canceled_csk(struct fpga_sec_mgr *smgr,
> > +		  int (*get_csk)(struct fpga_sec_mgr *smgr,
> > +				 unsigned long *csk_map, unsigned int nbits),
> > +		  int (*get_csk_nbits)(struct fpga_sec_mgr *smgr),
> > +		  char *buf)
> > +{
> > +	unsigned long *csk_map = NULL;
> > +	unsigned int nbits;
> > +	int ret;
> > +
> > +	ret = get_csk_nbits(smgr);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	nbits = (unsigned int)ret;
> > +	csk_map = vmalloc(sizeof(unsigned long) * BITS_TO_LONGS(nbits));
> > +	if (!csk_map)
> > +		return -ENOMEM;
> > +
> > +	ret = get_csk(smgr, csk_map, nbits);
> > +	if (ret)
> > +		goto vfree_exit;
> > +
> > +	ret = bitmap_print_to_pagebuf(1, buf, csk_map, nbits);
> > +
> > +vfree_exit:
> > +	vfree(csk_map);
> > +	return ret;
> > +}
> > +
> > +static ssize_t
> > +show_root_entry_hash(struct fpga_sec_mgr *smgr,
> > +		     int (*get_reh)(struct fpga_sec_mgr *smgr, u8 *hash,
> > +				    unsigned int size),
> > +		     int (*get_reh_size)(struct fpga_sec_mgr *smgr),
> > +		     char *buf)
> > +{
> > +	int size, i, cnt, ret;
> > +	u8 *hash;
> > +
> > +	ret = get_reh_size(smgr);
> > +	if (ret < 0)
> > +		return ret;
> > +	else if (!ret)
> > +		return sysfs_emit(buf, "hash not programmed\n");
> > +
> > +	size = ret;
> > +	hash = vmalloc(size);
> > +	if (!hash)
> > +		return -ENOMEM;
> > +
> > +	ret = get_reh(smgr, hash, size);
> > +	if (ret)
> > +		goto vfree_exit;
> > +
> > +	cnt = sprintf(buf, "0x");
> > +	for (i = 0; i < size; i++)
> > +		cnt += sprintf(buf + cnt, "%02x", hash[i]);
> > +	cnt += sprintf(buf + cnt, "\n");
> > +
> > +vfree_exit:
> > +	vfree(hash);
> > +	return ret ? : cnt;
> > +}
> > +
> > +#define DEVICE_ATTR_SEC_CSK(_name) \
> > +static ssize_t _name##_canceled_csks_show(struct device *dev, \
> > +					  struct device_attribute *attr, \
> > +					  char *buf) \
> > +{ \
> > +	struct fpga_sec_mgr *smgr = to_sec_mgr(dev); \
> > +	return show_canceled_csk(smgr, \
> > +	       smgr->sops->_name##_canceled_csks, \
> > +	       smgr->sops->_name##_canceled_csk_nbits, buf); \
> > +} \
> > +static DEVICE_ATTR_RO(_name##_canceled_csks)
> > +
> > +#define DEVICE_ATTR_SEC_ROOT_ENTRY_HASH(_name) \
> > +static ssize_t _name##_root_entry_hash_show(struct device *dev, \
> > +				     struct device_attribute *attr, \
> > +				     char *buf) \
> > +{ \
> > +	struct fpga_sec_mgr *smgr = to_sec_mgr(dev); \
> > +	return show_root_entry_hash(smgr, \
> > +	       smgr->sops->_name##_root_entry_hash, \
> > +	       smgr->sops->_name##_reh_size, buf); \
> > +} \
> > +static DEVICE_ATTR_RO(_name##_root_entry_hash)
> > +
> > +static ssize_t user_flash_count_show(struct device *dev,
> > +				     struct device_attribute *attr, char *buf)
> > +{
> > +	struct fpga_sec_mgr *smgr = to_sec_mgr(dev);
> > +	int cnt = smgr->sops->user_flash_count(smgr);
> > +
> > +	return cnt < 0 ? cnt : sysfs_emit(buf, "%u\n", cnt);
> > +}
> > +static DEVICE_ATTR_RO(user_flash_count);
> > +
> > +DEVICE_ATTR_SEC_ROOT_ENTRY_HASH(sr);
> > +DEVICE_ATTR_SEC_ROOT_ENTRY_HASH(pr);
> > +DEVICE_ATTR_SEC_ROOT_ENTRY_HASH(bmc);
> > +DEVICE_ATTR_SEC_CSK(sr);
> > +DEVICE_ATTR_SEC_CSK(pr);
> > +DEVICE_ATTR_SEC_CSK(bmc);
> > +
> > +static struct attribute *sec_mgr_security_attrs[] = {
> > +	&dev_attr_user_flash_count.attr,
> > +	&dev_attr_bmc_root_entry_hash.attr,
> > +	&dev_attr_sr_root_entry_hash.attr,
> > +	&dev_attr_pr_root_entry_hash.attr,
> > +	&dev_attr_sr_canceled_csks.attr,
> > +	&dev_attr_pr_canceled_csks.attr,
> > +	&dev_attr_bmc_canceled_csks.attr,
> > +	NULL,
> > +};
> > +
> > +#define check_attr(attribute, _name) \
> > +	((attribute) == &dev_attr_##_name.attr && smgr->sops->_name)
> > +
> > +static umode_t sec_mgr_visible(struct kobject *kobj,
> > +			       struct attribute *attr, int n)
> > +{
> > +	struct fpga_sec_mgr *smgr = to_sec_mgr(kobj_to_dev(kobj));
> > +
> > +	/*
> > +	 * Only display optional sysfs attributes if a
> > +	 * corresponding handler is provided
> > +	 */
> > +	if (check_attr(attr, user_flash_count) ||
> > +	    check_attr(attr, bmc_root_entry_hash) ||
> > +	    check_attr(attr, sr_root_entry_hash) ||
> > +	    check_attr(attr, pr_root_entry_hash) ||
> > +	    check_attr(attr, sr_canceled_csks) ||
> > +	    check_attr(attr, pr_canceled_csks) ||
> > +	    check_attr(attr, bmc_canceled_csks))
> > +		return attr->mode;
> > +
> > +	return 0;
> > +}
> > +
> > +static struct attribute_group sec_mgr_security_attr_group = {
> > +	.name = "security",
> > +	.attrs = sec_mgr_security_attrs,
> > +	.is_visible = sec_mgr_visible,
> > +};
> > +
> > +static ssize_t name_show(struct device *dev,
> > +			 struct device_attribute *attr, char *buf)
> > +{
> > +	struct fpga_sec_mgr *smgr = to_sec_mgr(dev);
> > +
> > +	return sysfs_emit(buf, "%s\n", smgr->name);
> > +}
> > +static DEVICE_ATTR_RO(name);
> > +
> > +static struct attribute *sec_mgr_attrs[] = {
> > +	&dev_attr_name.attr,
> > +	NULL,
> > +};
> > +
> > +static struct attribute_group sec_mgr_attr_group = {
> > +	.attrs = sec_mgr_attrs,
> > +};
> > +
> > +static const struct attribute_group *fpga_sec_mgr_attr_groups[] = {
> > +	&sec_mgr_attr_group,
> > +	&sec_mgr_security_attr_group,
> > +	NULL,
> > +};
> > +
> > +static bool check_sysfs_handler(struct device *dev,
> > +				void *sysfs_handler, void *size_handler,
> > +				const char *sysfs_handler_name,
> > +				const char *size_handler_name)
> > +{
> > +	/*
> > +	 * sysfs_handler and size_handler must either both be
> > +	 * defined or both be NULL.
> > +	 */
> > +	if (sysfs_handler && !size_handler) {
> > +		dev_err(dev, "%s registered without %s\n",
> > +			sysfs_handler_name, size_handler_name);
> > +		return false;
> > +	} else if (!sysfs_handler && size_handler) {
> > +		dev_err(dev, "%s registered without %s\n",
> > +			size_handler_name, sysfs_handler_name);
> > +		return false;
> > +	}
> > +	return true;
> > +}
> > +
> > +#define check_reh_handler(_dev, _sops, _name) \
> > +	check_sysfs_handler(_dev, (_sops)->_name##_root_entry_hash, \
> > +			    (_sops)->_name##_reh_size, \
> > +			    __stringify(_name##_root_entry_hash), \
> > +			    __stringify(_name##_reh_size))
> > +
> > +#define check_csk_handler(_dev, _sops, _name) \
> > +	check_sysfs_handler(_dev, (_sops)->_name##_canceled_csks, \
> > +			    (_sops)->_name##_canceled_csk_nbits, \
> > +			    __stringify(_name##_canceled_csks), \
> > +			    __stringify(_name##_canceled_csk_nbits))
> > +
> > +/**
> > + * fpga_sec_mgr_create - create and initialize an FPGA
> > + *			  security manager struct
> > + *
> > + * @dev:  fpga security manager device from pdev
> > + * @name: fpga security manager name
> > + * @sops: pointer to a structure of fpga callback functions
> > + * @priv: fpga security manager private data
> > + *
> > + * The caller of this function is responsible for freeing the struct
> > + * with ifpg_sec_mgr_free(). Using devm_fpga_sec_mgr_create() instead
> > + * is recommended.
> > + *
> > + * Return: pointer to struct fpga_sec_mgr or NULL
> > + */
> > +struct fpga_sec_mgr *
> > +fpga_sec_mgr_create(struct device *dev, const char *name,
> > +		    const struct fpga_sec_mgr_ops *sops, void *priv)
> > +{
> > +	struct fpga_sec_mgr *smgr;
> > +	int id, ret;
> > +
> > +	if (!check_reh_handler(dev, sops, bmc) ||
> > +	    !check_reh_handler(dev, sops, sr) ||
> > +	    !check_reh_handler(dev, sops, pr) ||
> > +	    !check_csk_handler(dev, sops, bmc) ||
> > +	    !check_csk_handler(dev, sops, sr) ||
> > +	    !check_csk_handler(dev, sops, pr)) {
> > +		return NULL;
> > +	}
> > +
> > +	if (!name || !strlen(name)) {
> > +		dev_err(dev, "Attempt to register with no name!\n");
> > +		return NULL;
> > +	}
> > +
> > +	smgr = kzalloc(sizeof(*smgr), GFP_KERNEL);
> > +	if (!smgr)
> > +		return NULL;
> > +
> > +	id = ida_simple_get(&fpga_sec_mgr_ida, 0, 0, GFP_KERNEL);
> > +	if (id < 0)
> > +		goto error_kfree;
> > +
> > +	mutex_init(&smgr->lock);
> > +
> > +	smgr->name = name;
> > +	smgr->priv = priv;
> > +	smgr->sops = sops;
> > +
> > +	device_initialize(&smgr->dev);
> > +	smgr->dev.class = fpga_sec_mgr_class;
> > +	smgr->dev.parent = dev;
> > +	smgr->dev.id = id;
> > +
> > +	ret = dev_set_name(&smgr->dev, "fpga_sec%d", id);
> > +	if (ret) {
> > +		dev_err(dev, "Failed to set device name: fpga_sec%d\n", id);
> > +		goto error_device;
> > +	}
> > +
> > +	return smgr;
> > +
> > +error_device:
> > +	ida_simple_remove(&fpga_sec_mgr_ida, id);
> > +
> > +error_kfree:
> > +	kfree(smgr);
> > +
> > +	return NULL;
> > +}
> > +EXPORT_SYMBOL_GPL(fpga_sec_mgr_create);
> > +
> > +/**
> > + * fpga_sec_mgr_free - free an FPGA security manager created
> > + *			with fpga_sec_mgr_create()
> > + *
> > + * @smgr:	FPGA security manager structure
> > + */
> > +void fpga_sec_mgr_free(struct fpga_sec_mgr *smgr)
> > +{
> > +	ida_simple_remove(&fpga_sec_mgr_ida, smgr->dev.id);
> > +	kfree(smgr);
> > +}
> > +EXPORT_SYMBOL_GPL(fpga_sec_mgr_free);
> > +
> > +static void devm_fpga_sec_mgr_release(struct device *dev, void *res)
> > +{
> > +	struct fpga_sec_mgr_devres *dr = res;
> > +
> > +	fpga_sec_mgr_free(dr->smgr);
> > +}
> > +
> > +/**
> > + * devm_fpga_sec_mgr_create - create and initialize an FPGA
> > + *			       security manager struct
> > + *
> > + * @dev:  fpga security manager device from pdev
> > + * @name: fpga security manager name
> > + * @sops: pointer to a structure of fpga callback functions
> > + * @priv: fpga security manager private data
> > + *
> > + * This function is intended for use in a FPGA Security manager
> > + * driver's probe function.  After the security manager driver creates
> > + * the fpga_sec_mgr struct with devm_fpga_sec_mgr_create(), it should
> > + * register it with devm_fpga_sec_mgr_register().
> > + * The fpga_sec_mgr struct allocated with this function will be freed
> > + * automatically on driver detach.
> > + *
> > + * Return: pointer to struct fpga_sec_mgr or NULL
> > + */
> > +struct fpga_sec_mgr *
> > +devm_fpga_sec_mgr_create(struct device *dev, const char *name,
> > +			 const struct fpga_sec_mgr_ops *sops, void *priv)
> > +{
> > +	struct fpga_sec_mgr_devres *dr;
> > +
> > +	dr = devres_alloc(devm_fpga_sec_mgr_release, sizeof(*dr), GFP_KERNEL);
> > +	if (!dr)
> > +		return NULL;
> > +
> > +	dr->smgr = fpga_sec_mgr_create(dev, name, sops, priv);
> > +	if (!dr->smgr) {
> > +		devres_free(dr);
> > +		return NULL;
> > +	}
> > +
> > +	devres_add(dev, dr);
> > +
> > +	return dr->smgr;
> > +}
> > +EXPORT_SYMBOL_GPL(devm_fpga_sec_mgr_create);
> > +
> > +/**
> > + * fpga_sec_mgr_register - register an FPGA security manager
> > + *
> > + * @smgr: fpga security manager struct
> > + *
> > + * Return: 0 on success, negative error code otherwise.
> > + */
> > +int fpga_sec_mgr_register(struct fpga_sec_mgr *smgr)
> > +{
> > +	int ret;
> > +
> > +	ret = device_add(&smgr->dev);
> > +	if (ret)
> > +		goto error_device;
> 
> The comment header for device_add() includes the following text:
> 
>  * NOTE: _Never_ directly free @dev after calling this function, even
>  * if it returned an error! Always use put_device() to give up your
>  * reference instead.
>  *
>  * Rule of thumb is: if device_add() succeeds, you should call
>  * device_del() when you want to get rid of it. If device_add() has
>  * *not* succeeded, use *only* put_device() to drop the reference
>  * count.
> 
> This implementation of the security manager requires that the parent
> driver treat the fpga_sec_mgr data structure as a a managed resource
> of the parent device using the devm_ version of the create() function.
> 
> The device structure that is passed to device_add() is embedded in the
> fpga_sec_mgr data structure.
> 
> Does this conflict with the core driver functions? Is it possible that
> we are deleting a device structure that is still being tracked by the
> core driver code?

I think it's fine since you'd call the unregister part in the remove()
function of your driver.

If you'd have failed on device_add(), though, you'd have returned an
error from the probe() function.

> 
> - Russ
> 
> > +
> > +	dev_info(&smgr->dev, "%s registered\n", smgr->name);
> > +
> > +	return 0;
> > +
> > +error_device:
> > +	ida_simple_remove(&fpga_sec_mgr_ida, smgr->dev.id);
> > +
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL_GPL(fpga_sec_mgr_register);
> > +
> > +/**
> > + * fpga_sec_mgr_unregister - unregister an FPGA security manager
> > + *
> > + * @mgr: fpga manager struct
> > + *
> > + * This function is intended for use in an FPGA security manager
> > + * driver's remove() function.
> > + */
> > +void fpga_sec_mgr_unregister(struct fpga_sec_mgr *smgr)
> > +{
> > +	dev_info(&smgr->dev, "%s %s\n", __func__, smgr->name);
> > +
> > +	device_unregister(&smgr->dev);
> > +}
> > +EXPORT_SYMBOL_GPL(fpga_sec_mgr_unregister);
> > +
> > +static int fpga_sec_mgr_devres_match(struct device *dev, void *res,
> > +				     void *match_data)
> > +{
> > +	struct fpga_sec_mgr_devres *dr = res;
> > +
> > +	return match_data == dr->smgr;
> > +}
> > +
> > +static void devm_fpga_sec_mgr_unregister(struct device *dev, void *res)
> > +{
> > +	struct fpga_sec_mgr_devres *dr = res;
> > +
> > +	fpga_sec_mgr_unregister(dr->smgr);
> > +}
> > +
> > +/**
> > + * devm_fpga_sec_mgr_register - resource managed variant of
> > + *				fpga_sec_mgr_register()
> > + *
> > + * @dev: managing device for this FPGA security manager
> > + * @smgr: fpga security manager struct
> > + *
> > + * This is the devres variant of fpga_sec_mgr_register() for which the
> > + * unregister function will be called automatically when the managing
> > + * device is detached.
> > + */
> > +int devm_fpga_sec_mgr_register(struct device *dev, struct fpga_sec_mgr *smgr)
> > +{
> > +	struct fpga_sec_mgr_devres *dr;
> > +	int ret;
> > +
> > +	/*
> > +	 * Make sure that the struct fpga_sec_mgr * that is passed in is
> > +	 * managed itself.
> > +	 */
> > +	if (WARN_ON(!devres_find(dev, devm_fpga_sec_mgr_release,
> > +				 fpga_sec_mgr_devres_match, smgr)))
> > +		return -EINVAL;
> > +
> > +	dr = devres_alloc(devm_fpga_sec_mgr_unregister, sizeof(*dr), GFP_KERNEL);
> > +	if (!dr)
> > +		return -ENOMEM;
> > +
> > +	ret = fpga_sec_mgr_register(smgr);
> > +	if (ret) {
> > +		devres_free(dr);
> > +		return ret;
> > +	}
> > +
> > +	dr->smgr = smgr;
> > +	devres_add(dev, dr);
> > +
> > +	return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(devm_fpga_sec_mgr_register);
> > +
> > +static void fpga_sec_mgr_dev_release(struct device *dev)
> > +{
> > +}
> > +
> > +static int __init fpga_sec_mgr_class_init(void)
> > +{
> > +	pr_info("FPGA Security Manager\n");
> > +
> > +	fpga_sec_mgr_class = class_create(THIS_MODULE, "fpga_sec_mgr");
> > +	if (IS_ERR(fpga_sec_mgr_class))
> > +		return PTR_ERR(fpga_sec_mgr_class);
> > +
> > +	fpga_sec_mgr_class->dev_groups = fpga_sec_mgr_attr_groups;
> > +	fpga_sec_mgr_class->dev_release = fpga_sec_mgr_dev_release;
> > +
> > +	return 0;
> > +}
> > +
> > +static void __exit fpga_sec_mgr_class_exit(void)
> > +{
> > +	class_destroy(fpga_sec_mgr_class);
> > +	ida_destroy(&fpga_sec_mgr_ida);
> > +}
> > +
> > +MODULE_DESCRIPTION("FPGA Security Manager Driver");
> > +MODULE_LICENSE("GPL v2");
> > +
> > +subsys_initcall(fpga_sec_mgr_class_init);
> > +module_exit(fpga_sec_mgr_class_exit)
> > diff --git a/include/linux/fpga/fpga-sec-mgr.h b/include/linux/fpga/fpga-sec-mgr.h
> > new file mode 100644
> > index 000000000000..dd596c6c3748
> > --- /dev/null
> > +++ b/include/linux/fpga/fpga-sec-mgr.h
> > @@ -0,0 +1,83 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Header file for FPGA Security Manager
> > + *
> > + * Copyright (C) 2019-2020 Intel Corporation, Inc.
> > + */
> > +#ifndef _LINUX_FPGA_SEC_MGR_H
> > +#define _LINUX_FPGA_SEC_MGR_H
> > +
> > +#include <linux/device.h>
> > +#include <linux/mutex.h>
> > +#include <linux/types.h>
> > +
> > +struct fpga_sec_mgr;
> > +
> > +/**
> > + * struct fpga_sec_mgr_ops - device specific operations
> > + * @user_flash_count:	    Optional: Return sysfs string output for FPGA
> > + *			    image flash count
> > + * @sr_root_entry_hash:	    Optional: Return sysfs string output for static
> > + *			    region root entry hash
> > + * @pr_root_entry_hash:	    Optional: Return sysfs string output for partial
> > + *			    reconfiguration root entry hash
> > + * @bmc_root_entry_hash:    Optional: Return sysfs string output for BMC
> > + *			    root entry hash
> > + * @sr_canceled_csks:	    Optional: Return sysfs string output for static
> > + *			    region canceled keys
> > + * @pr_canceled_csks:	    Optional: Return sysfs string output for partial
> > + *			    reconfiguration canceled keys
> > + * @bmc_canceled_csks:	    Optional: Return sysfs string output for bmc
> > + *			    canceled keys
> > + * @bmc_canceled_csk_nbits: Optional: Return BMC canceled csk vector bit count
> > + * @sr_canceled_csk_nbits:  Optional: Return SR canceled csk vector bit count
> > + * @pr_canceled_csk_nbits:  Optional: Return PR canceled csk vector bit count
> > + * @bmc_reh_size:	    Optional: Return byte size for BMC root entry hash
> > + * @sr_reh_size:	    Optional: Return byte size for SR root entry hash
> > + * @pr_reh_size:	    Optional: Return byte size for PR root entry hash
> > + */
> > +struct fpga_sec_mgr_ops {
> > +	int (*user_flash_count)(struct fpga_sec_mgr *smgr);
> > +	int (*bmc_root_entry_hash)(struct fpga_sec_mgr *smgr, u8 *hash,
> > +				   unsigned int size);
> > +	int (*sr_root_entry_hash)(struct fpga_sec_mgr *smgr, u8 *hash,
> > +				  unsigned int size);
> > +	int (*pr_root_entry_hash)(struct fpga_sec_mgr *smgr, u8 *hash,
> > +				  unsigned int size);
> > +	int (*bmc_canceled_csks)(struct fpga_sec_mgr *smgr,
> > +				 unsigned long *csk_map, unsigned int nbits);
> > +	int (*sr_canceled_csks)(struct fpga_sec_mgr *smgr,
> > +				unsigned long *csk_map, unsigned int nbits);
> > +	int (*pr_canceled_csks)(struct fpga_sec_mgr *smgr,
> > +				unsigned long *csk_map, unsigned int nbits);
> > +	int (*bmc_reh_size)(struct fpga_sec_mgr *smgr);
> > +	int (*sr_reh_size)(struct fpga_sec_mgr *smgr);
> > +	int (*pr_reh_size)(struct fpga_sec_mgr *smgr);
> > +	int (*bmc_canceled_csk_nbits)(struct fpga_sec_mgr *smgr);
> > +	int (*sr_canceled_csk_nbits)(struct fpga_sec_mgr *smgr);
> > +	int (*pr_canceled_csk_nbits)(struct fpga_sec_mgr *smgr);
> > +};
> > +
> > +struct fpga_sec_mgr {
> > +	const char *name;
> > +	struct device dev;
> > +	const struct fpga_sec_mgr_ops *sops;
> > +	struct mutex lock;		/* protect data structure contents */
> > +	void *priv;
> > +};
> > +
> > +struct fpga_sec_mgr *
> > +fpga_sec_mgr_create(struct device *dev, const char *name,
> > +		    const struct fpga_sec_mgr_ops *sops, void *priv);
> > +
> > +struct fpga_sec_mgr *
> > +devm_fpga_sec_mgr_create(struct device *dev, const char *name,
> > +			 const struct fpga_sec_mgr_ops *sops, void *priv);
> > +
> > +int fpga_sec_mgr_register(struct fpga_sec_mgr *smgr);
> > +int devm_fpga_sec_mgr_register(struct device *dev,
> > +			       struct fpga_sec_mgr *smgr);
> > +void fpga_sec_mgr_unregister(struct fpga_sec_mgr *smgr);
> > +void fpga_sec_mgr_free(struct fpga_sec_mgr *smgr);
> > +
> > +#endif
> 

Cheers,
Moritz

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