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    SubjectRe: [PATCH v20 3/5] fpga: m10bmc-sec: expose max10 flash update count
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    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@intel.com>
    >> Reviewed-by: Tom Rix <trix@redhat.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@intel.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.

    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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