Re: [PATCH v19 2/5] fpga: m10bmc-sec: create max10 bmc secure update

From: Xu Yilun <yilun.xu@intel.com>
To: Russ Weight <russell.h.weight@intel.com>
Cc: mdf@kernel.org, hao.wu@intel.com, lee.jones@linaro.org,
	linux-fpga@vger.kernel.org, linux-kernel@vger.kernel.org,
	trix@redhat.com, marpagan@redhat.com, lgoncalv@redhat.com,
	matthew.gerlach@linux.intel.com,
	basheer.ahmed.muddebihal@intel.com, tianfei.zhang@intel.com
Subject: Re: [PATCH v19 2/5] fpga: m10bmc-sec: create max10 bmc secure update
Date: Tue, 17 May 2022 00:19:07 +0800	[thread overview]
Message-ID: <20220516161907.GA37553@yilunxu-OptiPlex-7050> (raw)
In-Reply-To: <20220510195635.140722-3-russell.h.weight@intel.com>

On Tue, May 10, 2022 at 12:56:32PM -0700, Russ Weight wrote:
> Create a sub driver for the FPGA Card BMC in order to support secure
> updates.  This patch creates the Max10 BMC Secure Update driver
> and provides sysfs files for displaying the current root entry hashes
> for the FPGA static region, the FPGA PR region, and the card BMC.

Could you describe a little more about what is the root entry, and how
the root entry hashes (maybe also the cancel code signing key) work to
ensure secure update?

> 
> Signed-off-by: Russ Weight <russell.h.weight@intel.com>
> Reviewed-by: Tom Rix <trix@redhat.com>
> ---
> v19:
>   - Change "card bmc" naming back to "m10 bmc" naming to be consistent
>     with the parent driver.
> v18:
>   - Changed the ABI documentation for the Root Entry Hashes to specify
>     string as the format for the output.
>   - Updated comments, strings and config options to more consistently
>     refer to the driver as the Intel FPGA Card BMC Secure Update driver.
>   - Removed an instance of dev_dbg().
>   - Deferred the call to firmware_upload_register() to a later patch
>     where the required ops are provided. The bmc_sec_remove() function is
>     also removed from this patch and added in a later patch.
>   - Switched from MODULE_ALIAS() to MODULE_DEVICE_TABLE() in anticipation
>     of additional cards to be supported by the same driver.
> v17:
>   - Update the Date and KernelVersion for the ABI documentation to Jul 2022
>     and 5.19 respectively.
>   - Updated the copyright end-date to 2022 for the secure update driver.
>   - Change m10bmc to cardbmc to reflect the fact that the future devices
>     will not necessarily use the MAX10. This affects filenames, configs, and
>     symbol names.
>   - Removed references to the FPGA Image Load class driver and replaced
>     them with the new firmware-upload service from the firmware loader.
>   - Firmware upload requires a unique name for the firmware device. Use
>     xarray_alloc to generate a unique number to append to the name.
>   - Changed the license from GPL to GPLv2 per commit bf7fbeeae6db: 'module:
>     Cure the MODULE_LICENSE "GPL" vs. "GPL v2" bogosity'
> v16:
>   - No Change
> v15:
>   - Updated the Dates and KernelVersions in the ABI documentation
>   - Change driver name from "n3000bmc-secure" to "n3000bmc-sec-update".
>   - Change CONFIG_FPGA_M10_BMC_SECURE to CONFIG_FPGA_M10_BMC_SEC_UPDATE.
>   - Change instances of *bmc-secure to *bmc-sec-update in file name
>     and symbol names.
>   - Change instances of *m10bmc_secure* to *m10bmc-sec_update* in symbol
>     names.
>   - Change instances of *lops* to *ops* in symbol names.
> v14:
>   - Changed symbol and text references to reflect the renaming of the
>     Security Manager Class driver to FPGA Image Load.
> v13:
>   - Updated copyright to 2021
>   - Updated ABI documentation date and kernel version
>   - Call updated fpga_sec_mgr_register() and fpga_sec_mgr_unregister()
>     functions instead of devm_fpga_sec_mgr_create() and
>     devm_fpga_sec_mgr_register().
> v12:
>   - Updated Date and KernelVersion fields in ABI documentation
> v11:
>   - Added Reviewed-by tag
> v10:
>   - Changed the path expressions in the sysfs documentation to
>     replace the n3000 reference with something more generic to
>     accomodate other devices that use the same driver.
> v9:
>   - Rebased to 5.12-rc2 next
>   - Updated Date and KernelVersion in ABI documentation
> v8:
>   - Previously patch 2/6, otherwise no change
> v7:
>   - Updated Date and KernelVersion in ABI documentation
> v6:
>   - Added WARN_ON() call for (sha_num_bytes / stride) to assert
>     that the proper count is passed to regmap_bulk_read().
> v5:
>   - No change
> v4:
>   - Moved sysfs files for displaying the root entry hashes (REH)
>     from the FPGA Security Manager class driver to here. The
>     m10bmc_reh() and m10bmc_reh_size() functions are removed and
>     the functionality from these functions is moved into a
>     show_root_entry_hash() function for displaying the REHs.
>   - Added ABI documentation for the new sysfs entries:
>     sysfs-driver-intel-m10-bmc-secure
>   - Updated the MAINTAINERS file to add the new ABI documentation
>     file: sysfs-driver-intel-m10-bmc-secure
>   - Removed unnecessary ret variable from m10bmc_secure_probe()
>   - Incorporated new devm_fpga_sec_mgr_register() function into
>     m10bmc_secure_probe() and removed the m10bmc_secure_remove()
>     function.
> v3:
>   - Changed from "Intel FPGA Security Manager" to FPGA Security Manager"
>   - Changed: iops -> sops, imgr -> smgr, IFPGA_ -> FPGA_, ifpga_ to fpga_
>   - Changed "MAX10 BMC Secure Engine driver" to "MAX10 BMC Secure
>     Update driver"
>   - Removed wrapper functions (m10bmc_raw_*, m10bmc_sys_*). The
>     underlying functions are now called directly.
>   - Changed "_root_entry_hash" to "_reh", with a comment explaining
>     what reh is.
> v2:
>   - Added drivers/fpga/intel-m10-bmc-secure.c file to MAINTAINERS.
>   - Switched to GENMASK(31, 16) for a couple of mask definitions.
>   - Moved MAX10 BMC address and function definitions to a separate
>     patch.
>   - Replaced small function-creation macros with explicit function
>     declarations.
>   - Removed ifpga_sec_mgr_init() and ifpga_sec_mgr_uinit() functions.
>   - Adapted to changes in the Intel FPGA Security Manager by splitting
>     the single call to ifpga_sec_mgr_register() into two function
>     calls: devm_ifpga_sec_mgr_create() and ifpga_sec_mgr_register().
> ---
>  .../sysfs-driver-intel-m10-bmc-sec-update     |  29 ++++
>  MAINTAINERS                                   |   7 +
>  drivers/fpga/Kconfig                          |  12 ++
>  drivers/fpga/Makefile                         |   3 +
>  drivers/fpga/intel-m10-bmc-sec-update.c       | 133 ++++++++++++++++++
>  5 files changed, 184 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-driver-intel-m10-bmc-sec-update
>  create mode 100644 drivers/fpga/intel-m10-bmc-sec-update.c
> 
> diff --git a/Documentation/ABI/testing/sysfs-driver-intel-m10-bmc-sec-update b/Documentation/ABI/testing/sysfs-driver-intel-m10-bmc-sec-update
> new file mode 100644
> index 000000000000..2bb271695e14
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-driver-intel-m10-bmc-sec-update
> @@ -0,0 +1,29 @@
> +What:		/sys/bus/platform/drivers/intel-m10bmc-sec-update/.../security/sr_root_entry_hash
> +Date:		Jul 2022
> +KernelVersion:	5.19
> +Contact:	Russ Weight <russell.h.weight@intel.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: string.
> +
> +What:		/sys/bus/platform/drivers/intel-m10bmc-sec-update/.../security/pr_root_entry_hash
> +Date:		Jul 2022
> +KernelVersion:	5.19
> +Contact:	Russ Weight <russell.h.weight@intel.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: string.
> +
> +What:		/sys/bus/platform/drivers/intel-m10bmc-sec-update/.../security/bmc_root_entry_hash
> +Date:		Jul 2022
> +KernelVersion:	5.19
> +Contact:	Russ Weight <russell.h.weight@intel.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: string.
> diff --git a/MAINTAINERS b/MAINTAINERS
> index cf883b1ec852..759a7788dad9 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -7784,6 +7784,13 @@ F:	Documentation/fpga/
>  F:	drivers/fpga/
>  F:	include/linux/fpga/
>  
> +INTEL MAX10 BMC SECURE UPDATES
> +M:	Russ Weight <russell.h.weight@intel.com>
> +L:	linux-fpga@vger.kernel.org
> +S:	Maintained
> +F:	Documentation/ABI/testing/sysfs-driver-intel-m10-bmc-sec-update
> +F:	drivers/fpga/intel-m10-bmc-sec-update.c
> +
>  FPU EMULATOR
>  M:	Bill Metzenthen <billm@melbpc.org.au>
>  S:	Maintained
> diff --git a/drivers/fpga/Kconfig b/drivers/fpga/Kconfig
> index 991b3f361ec9..0831eecc9a09 100644
> --- a/drivers/fpga/Kconfig
> +++ b/drivers/fpga/Kconfig
> @@ -243,4 +243,16 @@ config FPGA_MGR_VERSAL_FPGA
>  	  configure the programmable logic(PL).
>  
>  	  To compile this as a module, choose M here.
> +
> +config FPGA_M10_BMC_SEC_UPDATE
> +	tristate "Intel MAX10 BMC Secure Update driver"
> +	depends on MFD_INTEL_M10_BMC && FW_UPLOAD
> +	help
> +	  Secure update support for the Intel MAX10 board management
> +	  controller.
> +
> +	  This is a subdriver of the Intel MAX10 board management controller
> +	  (BMC) and provides support for secure updates for the BMC image,
> +	  the FPGA image, the Root Entry Hashes, etc.
> +
>  endif # FPGA
> diff --git a/drivers/fpga/Makefile b/drivers/fpga/Makefile
> index 5935b3d0abd5..139ac1b573d3 100644
> --- a/drivers/fpga/Makefile
> +++ b/drivers/fpga/Makefile
> @@ -22,6 +22,9 @@ obj-$(CONFIG_FPGA_MGR_VERSAL_FPGA)	+= versal-fpga.o
>  obj-$(CONFIG_ALTERA_PR_IP_CORE)		+= altera-pr-ip-core.o
>  obj-$(CONFIG_ALTERA_PR_IP_CORE_PLAT)	+= altera-pr-ip-core-plat.o
>  
> +# FPGA Secure Update Drivers
> +obj-$(CONFIG_FPGA_M10_BMC_SEC_UPDATE)	+= intel-m10-bmc-sec-update.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/intel-m10-bmc-sec-update.c b/drivers/fpga/intel-m10-bmc-sec-update.c
> new file mode 100644
> index 000000000000..a36856d897c9
> --- /dev/null
> +++ b/drivers/fpga/intel-m10-bmc-sec-update.c
> @@ -0,0 +1,133 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Intel MAX10 Board Management Controller Secure Update Driver
> + *
> + * Copyright (C) 2019-2022 Intel Corporation. All rights reserved.
> + *
> + */
> +#include <linux/bitfield.h>
> +#include <linux/device.h>
> +#include <linux/firmware.h>
> +#include <linux/mfd/intel-m10-bmc.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +
> +struct m10bmc_sec {
> +	struct device *dev;
> +	struct intel_m10bmc *m10bmc;
> +};
> +
> +/* Root Entry Hash (REH) support */
> +#define REH_SHA256_SIZE		32
> +#define REH_SHA384_SIZE		48
> +#define REH_MAGIC		GENMASK(15, 0)
> +#define REH_SHA_NUM_BYTES	GENMASK(31, 16)
> +
> +static ssize_t
> +show_root_entry_hash(struct device *dev, u32 exp_magic,
> +		     u32 prog_addr, u32 reh_addr, char *buf)
> +{
> +	struct m10bmc_sec *sec = dev_get_drvdata(dev);
> +	unsigned int stride = regmap_get_reg_stride(sec->m10bmc->regmap);

reverse xmax tree declarations is recommended. You may initiate the
variable after declaration.

> +	int sha_num_bytes, i, ret, cnt = 0;
> +	u8 hash[REH_SHA384_SIZE];
> +	u32 magic;
> +
> +	ret = m10bmc_raw_read(sec->m10bmc, prog_addr, &magic);
> +	if (ret)
> +		return ret;
> +
> +	if (FIELD_GET(REH_MAGIC, magic) != exp_magic)
> +		return sysfs_emit(buf, "hash not programmed\n");
> +
> +	sha_num_bytes = FIELD_GET(REH_SHA_NUM_BYTES, magic) / 8;
> +	if (sha_num_bytes != REH_SHA256_SIZE &&
> +	    sha_num_bytes != REH_SHA384_SIZE)   {
> +		dev_err(sec->dev, "%s bad sha num bytes %d\n", __func__,
> +			sha_num_bytes);
> +		return -EINVAL;
> +	}
> +
> +	WARN_ON(sha_num_bytes % stride);

The user will still get the output value which is broken. So why not
check the condition earlier, and stop user from accessing the interface
if it cannot work.

> +	ret = regmap_bulk_read(sec->m10bmc->regmap, reh_addr,
> +			       hash, sha_num_bytes / stride);
> +	if (ret) {
> +		dev_err(dev, "failed to read root entry hash: %x cnt %x: %d\n",
> +			reh_addr, sha_num_bytes / stride, ret);
> +		return ret;
> +	}
> +
> +	for (i = 0; i < sha_num_bytes; i++)
> +		cnt += sprintf(buf + cnt, "%02x", hash[i]);
> +	cnt += sprintf(buf + cnt, "\n");
> +
> +	return cnt;
> +}
> +
> +#define DEVICE_ATTR_SEC_REH_RO(_name, _magic, _prog_addr, _reh_addr) \
> +static ssize_t _name##_root_entry_hash_show(struct device *dev, \
> +					    struct device_attribute *attr, \
> +					    char *buf) \
> +{ return show_root_entry_hash(dev, _magic, _prog_addr, _reh_addr, buf); } \
> +static DEVICE_ATTR_RO(_name##_root_entry_hash)
> +
> +DEVICE_ATTR_SEC_REH_RO(bmc, BMC_PROG_MAGIC, BMC_PROG_ADDR, BMC_REH_ADDR);
> +DEVICE_ATTR_SEC_REH_RO(sr, SR_PROG_MAGIC, SR_PROG_ADDR, SR_REH_ADDR);
> +DEVICE_ATTR_SEC_REH_RO(pr, PR_PROG_MAGIC, PR_PROG_ADDR, PR_REH_ADDR);
> +
> +static struct attribute *m10bmc_security_attrs[] = {
> +	&dev_attr_bmc_root_entry_hash.attr,
> +	&dev_attr_sr_root_entry_hash.attr,
> +	&dev_attr_pr_root_entry_hash.attr,
> +	NULL,
> +};
> +
> +static struct attribute_group m10bmc_security_attr_group = {
> +	.name = "security",
> +	.attrs = m10bmc_security_attrs,
> +};
> +
> +static const struct attribute_group *m10bmc_sec_attr_groups[] = {
> +	&m10bmc_security_attr_group,
> +	NULL,
> +};
> +
> +#define SEC_UPDATE_LEN_MAX 32
> +static int m10bmc_sec_probe(struct platform_device *pdev)
> +{
> +	struct m10bmc_sec *sec;
> +
> +	sec = devm_kzalloc(&pdev->dev, sizeof(*sec), GFP_KERNEL);
> +	if (!sec)
> +		return -ENOMEM;
> +
> +	sec->dev = &pdev->dev;
> +	sec->m10bmc = dev_get_drvdata(pdev->dev.parent);
> +	dev_set_drvdata(&pdev->dev, sec);
> +
> +	return 0;
> +}
> +
> +static const struct platform_device_id intel_m10bmc_sec_ids[] = {
> +	{
> +		.name = "n3000bmc-sec-update",
> +	},
> +	{ }
> +};
Please move the MODULE_DEVICE_TABLE() here, without blank lines.

Thanks,
Yilun

> +
> +static struct platform_driver intel_m10bmc_sec_driver = {
> +	.probe = m10bmc_sec_probe,
> +	.driver = {
> +		.name = "intel-m10bmc-sec-update",
> +		.dev_groups = m10bmc_sec_attr_groups,
> +	},
> +	.id_table = intel_m10bmc_sec_ids,
> +};
> +module_platform_driver(intel_m10bmc_sec_driver);
> +
> +MODULE_DEVICE_TABLE(platform, intel_m10bmc_sec_ids);
> +MODULE_AUTHOR("Intel Corporation");
> +MODULE_DESCRIPTION("Intel MAX10 BMC Secure Update");
> +MODULE_LICENSE("GPL");
> -- 
> 2.25.1