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Date: Tue, 17 May 2022 09:16:50 -0700
From: Russ Weight <russell.h.weight@...el.com>
To: Xu Yilun <yilun.xu@...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 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.
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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