[CentOS] C7 Kernel module compilation

Il 07/08/19 01:02, Phil Perry ha scritto:
> On 06/08/2019 14:45, Alessandro Baggi wrote:
>> Il 05/08/19 20:07, Akemi Yagi ha scritto:
>>> On Mon, Aug 5, 2019 at 9:21 AM Alessandro Baggi
>>> <alessandro.baggi at gmail.com> wrote:
>>>>
>>>> Il 05/08/19 18:07, Akemi Yagi ha scritto:
>>>>> On Mon, Aug 5, 2019 at 9:01 AM Alessandro Baggi
>>>>> <alessandro.baggi at gmail.com> wrote:
>>>
>>>>> Do you have secureboot enabled? Then yes, that requires a proper key.
>>>>>
>>>>> Akemi
>>>>
>>>> Yes I have secureboot enabled. If usefull to others in list this could
>>>> helps:
>>>>
>>>> https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Kernel_Administration_Guide/sect-signing-kernel-modules-for-secure-boot.html 
>>>>
>>>>
>>>> I think also that  centos's wiki must be updated because steps are 
>>>> valid
>>>> for centos 5 and because key-signing is required for secure boot I 
>>>> think
>>>> that a proper section must be inserted.
>>>
>>> Update not finished yet but the above link has been added near the top
>>> of the wiki article.
>>>
>>> Akemi
>>> _______________________________________________
>>> CentOS mailing list
>>> CentOS at centos.org
>>> https://lists.centos.org/mailman/listinfo/centos
>>>
>>
>> Sorry, I was wrong, secureboot is disabled so I don't need to sign new 
>> modules.
>>
>> How I can solve my problem?
>>
>> Thanks in advance
> 
> Please post the actual error message in dmesg or /var/log/messages.
> 
> It's likely that the kernel is just grumbling that the module is not 
> signed (missing key), but it's just noise unless you're using 
> SecureBoot. Posting the actual message in full will help determine if 
> that is the case.
> 
> Thanks
> 
> Phil
> 
> 
> _______________________________________________
> CentOS mailing list
> CentOS at centos.org
> https://lists.centos.org/mailman/listinfo/centos

Hi, thank you for your reply,
I solve adding in "General Setup" values of current kernel on 
localversion option and adding Module.symver from 
/boot/symver-version.gz to module directory.

Now I get another problem compiling the third party module (i2c-nct6775):

"CONFIG_RETPOLINE=y but not supported by the compiler. Compiler update 
recomended. Stop."

I tried using scl gcc7 and 8 but get the same issue.

I checked that retpoline is related to Spectre but checking on centos with:

cat /sys/devices/system/cpu/vulnerabilities/spectre_v2

I get:

Mitigation: IBRS (kernel), IBPB

and RETPOLINE seems disabled (I'm wrong?).

I ridden in a blog post that I can disable this check commenting out 
some lines starting from N. 166 of arch/Makefile but I don't think this 
is the best approach.

At this point I can't understand what means the previous error and why I 
get this error when compiling i2c-nct6775.

Can someone point me in the right direction?

Thanks in advance.