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Message-ID: <20220518071010.GA55267@yilunxu-OptiPlex-7050>
Date: Wed, 18 May 2022 15:10:10 +0800
From: Xu Yilun <yilun.xu@...el.com>
To: Russ Weight <russell.h.weight@...el.com>
Cc: mdf@...nel.org, hao.wu@...el.com, lee.jones@...aro.org,
linux-fpga@...r.kernel.org, linux-kernel@...r.kernel.org,
trix@...hat.com, marpagan@...hat.com, lgoncalv@...hat.com,
matthew.gerlach@...ux.intel.com,
basheer.ahmed.muddebihal@...el.com, tianfei.zhang@...el.com
Subject: Re: [PATCH v20 3/5] fpga: m10bmc-sec: expose max10 flash update count
On Tue, May 17, 2022 at 09:16:50AM -0700, Russ Weight wrote:
>
>
> On 5/16/22 21:13, Xu Yilun wrote:
> > On Mon, May 16, 2022 at 04:49:39PM -0700, Russ Weight wrote:
> >> Extend the MAX10 BMC Secure Update driver to provide a sysfs file to
> >> expose the flash update count.
> >>
> >> Signed-off-by: Russ Weight <russell.h.weight@...el.com>
> >> Reviewed-by: Tom Rix <trix@...hat.com>
> >> ---
> >> v20:
> >> - No change
> >> v19:
> >> - Change "card bmc" naming back to "m10 bmc" naming to be consistent
> >> with the parent driver.
> >> v18:
> >> - No change
> >> v17:
> >> - Update the Date and KernelVersion for the ABI documentation to Jul 2022
> >> and 5.19 respectively.
> >> - Change "m10bmc" in symbol names to "cardbmc" to reflect the fact that the
> >> future devices will not necessarily use the MAX10.
> >> v16:
> >> - No Change
> >> v15:
> >> - Updated the Dates and KernelVersions in the ABI documentation
> >> v14:
> >> - No change
> >> v13:
> >> - Updated ABI documentation date and kernel version
> >> v12:
> >> - Updated Date and KernelVersion fields in ABI documentation
> >> v11:
> >> - No change
> >> v10:
> >> - Changed the path expression 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 3/6, otherwise no change
> >> v7:
> >> - Updated Date and KernelVersion in ABI documentation
> >> v6:
> >> - Changed flash_count_show() parameter list to achieve
> >> reverse-christmas tree format.
> >> - Added WARN_ON() call for (FLASH_COUNT_SIZE / stride) to ensure
> >> that the proper count is passed to regmap_bulk_read().
> >> v5:
> >> - Renamed sysfs node user_flash_count to flash_count and updated the
> >> sysfs documentation accordingly.
> >> v4:
> >> - Moved the sysfs file for displaying the flash count from the
> >> FPGA Security Manager class driver to here. The
> >> m10bmc_user_flash_count() function is removed and the
> >> functionality is moved into a user_flash_count_show()
> >> function.
> >> - Added ABI documentation for the new sysfs entry
> >> v3:
> >> - 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.
> >> v2:
> >> - Renamed get_qspi_flash_count() to m10bmc_user_flash_count()
> >> - Minor code cleanup per review comments
> >> - Added m10bmc_ prefix to functions in m10bmc_iops structure
> >> ---
> >> .../sysfs-driver-intel-m10-bmc-sec-update | 8 +++++
> >> drivers/fpga/intel-m10-bmc-sec-update.c | 36 +++++++++++++++++++
> >> 2 files changed, 44 insertions(+)
> >>
> >> diff --git a/Documentation/ABI/testing/sysfs-driver-intel-m10-bmc-sec-update b/Documentation/ABI/testing/sysfs-driver-intel-m10-bmc-sec-update
> >> index 2bb271695e14..1132e39b2125 100644
> >> --- a/Documentation/ABI/testing/sysfs-driver-intel-m10-bmc-sec-update
> >> +++ b/Documentation/ABI/testing/sysfs-driver-intel-m10-bmc-sec-update
> >> @@ -27,3 +27,11 @@ Description: Read only. Returns the root entry hash for the BMC image
> >> "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/flash_count
> >> +Date: Jul 2022
> >> +KernelVersion: 5.19
> >> +Contact: Russ Weight <russell.h.weight@...el.com>
> >> +Description: Read only. Returns number of times the secure update
> >> + staging area has been flashed.
> >> + Format: "%u".
> >> diff --git a/drivers/fpga/intel-m10-bmc-sec-update.c b/drivers/fpga/intel-m10-bmc-sec-update.c
> >> index f9f39d2cfe5b..3f183202de3b 100644
> >> --- a/drivers/fpga/intel-m10-bmc-sec-update.c
> >> +++ b/drivers/fpga/intel-m10-bmc-sec-update.c
> >> @@ -78,7 +78,43 @@ 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);
> >>
> >> +#define FLASH_COUNT_SIZE 4096 /* count stored as inverted bit vector */
> >> +
> >> +static ssize_t flash_count_show(struct device *dev,
> >> + struct device_attribute *attr, char *buf)
> >> +{
> >> + struct m10bmc_sec *sec = dev_get_drvdata(dev);
> >> + unsigned int stride, num_bits;
> >> + u8 *flash_buf;
> >> + int cnt, ret;
> >> +
> >> + stride = regmap_get_reg_stride(sec->m10bmc->regmap);
> >> + num_bits = FLASH_COUNT_SIZE * 8;
> >> +
> >> + flash_buf = kmalloc(FLASH_COUNT_SIZE, GFP_KERNEL);
> >> + if (!flash_buf)
> >> + return -ENOMEM;
> >> +
> >> + WARN_ON(FLASH_COUNT_SIZE % stride);
> > The same concern here. Stop users from getting the broken value.
>
> Sure - I will change this.
>
> I was using WARN_ON() because it indicates a problem in the device or
> the driver itself. It is not really validating information from userspace.
Understood. So it is OK we keep the WARN_ON, or WARN_ON_ONCE？But we
should still have some code to handle the issue gracefully rather
than just passing the broken value to user.
Thanks
Yilun
>
> As I understand it, WARN_ON() is used to log such events to the kernel
> log. If this isn't an appropriate use of WARN_ON(), then when should I
> consider using it?
>
> Thanks,
> - Russ
> >
> >> + ret = regmap_bulk_read(sec->m10bmc->regmap, STAGING_FLASH_COUNT,
> >> + flash_buf, FLASH_COUNT_SIZE / stride);
> >> + if (ret) {
> >> + dev_err(sec->dev,
> >> + "failed to read flash count: %x cnt %x: %d\n",
> >> + STAGING_FLASH_COUNT, FLASH_COUNT_SIZE / stride, ret);
> >> + goto exit_free;
> >> + }
> >> + cnt = num_bits - bitmap_weight((unsigned long *)flash_buf, num_bits);
> >> +
> >> +exit_free:
> >> + kfree(flash_buf);
> >> +
> >> + return ret ? : sysfs_emit(buf, "%u\n", cnt);
> >> +}
> >> +static DEVICE_ATTR_RO(flash_count);
> >> +
> >> static struct attribute *m10bmc_security_attrs[] = {
> >> + &dev_attr_flash_count.attr,
> >> &dev_attr_bmc_root_entry_hash.attr,
> >> &dev_attr_sr_root_entry_hash.attr,
> >> &dev_attr_pr_root_entry_hash.attr,
> >> --
> >> 2.25.1
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