Re: [PATCH v5 7/7] tpm: replace or remove printk error messages

[Nayna <nayna-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>]

On 10/27/2016 07:23 PM, Jarkko Sakkinen wrote:
> On Wed, Oct 26, 2016 at 11:01:00PM +0530, Nayna wrote:
>>
>>
>> On 10/26/2016 04:26 PM, Jarkko Sakkinen wrote:
>>> On Wed, Oct 26, 2016 at 07:52:53AM +0530, Nayna wrote:
>>>>
>>>>
>>>> On 10/21/2016 08:32 PM, Jarkko Sakkinen wrote:
>>>>> On Fri, Oct 21, 2016 at 08:52:14AM +0530, Nayna wrote:
>>>>>>
>>>>>>
>>>>>> On 10/20/2016 04:54 PM, Jarkko Sakkinen wrote:
>>>>>>> On Thu, Oct 20, 2016 at 07:34:37AM +0000, Winkler, Tomas wrote:
>>>>>>>>> On Tue, Oct 18, 2016 at 08:49:45PM -0400, Nayna Jain wrote:
>>>>>>>>>> This patch removes the unnecessary error messages on failing to
>>>>>>>>>> allocate memory and replaces pr_err/printk with dev_dbg/dev_info as
>>>>>>>>>> applicable.
>>>>>>>>>>
>>>>>>>>>> Suggested-by: Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
>>>>>>>>>> Signed-off-by: Nayna Jain <nayna-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
>>>>>>>>>
>>>>>>>>> Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
>>>>>>>>>
>>>>>>>>> /Jarkko
>>>>>>>>>
>>>>>>>>>> ---
>>>>>>>>>>      drivers/char/tpm/tpm_acpi.c | 17 +++++------------
>>>>>>>>>>      drivers/char/tpm/tpm_of.c   | 30 ++++++++++--------------------
>>>>>>>>>>      2 files changed, 15 insertions(+), 32 deletions(-)
>>>>>>>>>>
>>>>>>>>>> diff --git a/drivers/char/tpm/tpm_acpi.c b/drivers/char/tpm/tpm_acpi.c
>>>>>>>>>> index 859bdba..22e42da 100644
>>>>>>>>>> --- a/drivers/char/tpm/tpm_acpi.c
>>>>>>>>>> +++ b/drivers/char/tpm/tpm_acpi.c
>>>>>>>>>> @@ -60,11 +60,8 @@ int read_log_acpi(struct tpm_chip *chip)
>>>>>>>>>>      	status = acpi_get_table(ACPI_SIG_TCPA, 1,
>>>>>>>>>>      				(struct acpi_table_header **)&buff);
>>>>>>>>>>
>>>>>>>>>> -	if (ACPI_FAILURE(status)) {
>>>>>>>>>> -		printk(KERN_ERR "%s: ERROR - Could not get TCPA table\n",
>>>>>>>>>> -		       __func__);
>>>>>>>>>> +	if (ACPI_FAILURE(status))
>>>>>>>>>>      		return -EIO;
>>>>>>>>>> -	}
>>>>>>>>>>
>>>>>>>>>>      	switch(buff->platform_class) {
>>>>>>>>>>      	case BIOS_SERVER:
>>>>>>>>>> @@ -78,25 +75,21 @@ int read_log_acpi(struct tpm_chip *chip)
>>>>>>>>>>      		break;
>>>>>>>>>>      	}
>>>>>>>>>>      	if (!len) {
>>>>>>>>>> -		printk(KERN_ERR "%s: ERROR - TCPA log area empty\n",
>>>>>>>>> __func__);
>>>>>>>>>> +		dev_dbg(&chip->dev, "%s: ERROR - TCPA log area empty\n",
>>>>>>>>>> +			__func__);
>>>>>>>>
>>>>>>>>
>>>>>>>> Why to keep __func__ here, dev_dbg already does it for you.
>>>>>>>
>>>>>>> Good catch. I would actually consider also changing this to
>>>>>>>
>>>>>>> dev_err(dev, FW_BUG "TCPA log area empty\n");
>>>>>>>
>>>>>>> If TCPA exists but it's empty, that's most likely a FW bug.
>>>>>>
>>>>>> If it can be possibly a FW bug, should it fail the probe also just like
>>>>>> -ENOMEM error ?
>>>>>
>>>>> I think so but I hold for second opinion on this. I mean wouldn't
>>>>> it seem like a bit broken situation where TCPA tabe would exist but
>>>>> would also be empty?
>>>>
>>>> Hmm, is it possible for this to be firmware implementation dependent ?
>>>
>>> Let me put it this way. Why would anyone expose TCPA to the user space
>>> that is empty? What would be the point?
>>
>> If I understand correctly,  the reserved memory for event log would be
>> allocated much earlier and firmware would directly write to this allocated
>> memory. So, if there is a firmware bug, and events are not recorded, it will
>> get exposed to userspace as empty event log and this might also help
>> applications to know that it is broken.  Is there any wrong assumption here
>> ?
>
> I think the right question to ask is can event log be legally empty?

No

> If not, then FW_BUG should be used here.
Ok. yeah. and then I think we would want it to fail the probe ?

Thanks & Regards,
    - Nayna

>
> /Jarkko
>


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