Re: [GIT PULL] kbuild changes for v4.9-rc1

[Nikolay Borisov <n.borisov.lkml@gmail.com>]

On 18.12.2016 13:03, Arend Van Spriel wrote:
> On 18-12-2016 11:49, Jiri Slaby wrote:
>> On 12/18/2016, 12:59 AM, Linus Torvalds wrote:
>>> On Sat, Dec 17, 2016 at 12:57 AM, Jiri Slaby <jslaby@suse.cz> wrote:
>>>>
>>>> Yes, disk drivers won't load:
>>>> [    2.141973] virtio_pci: disagrees about version of symbol mcount
>>>> [    2.144415] virtio_pci: Unknown symbol mcount (err -22)
>>>
>>> This makes no sense.
>>>
>>> mcount isn't even one of the symbols that the patch by Adam is touching.
>>
>> asm-prototypes.h in his patch includes asm/ftrace.h, where the function
>> is declared. That should be enough IIUC scripts/Makefile.build.
>>
>>> There's something else screwed up here. Not to mention that others
>>> don't have your issue.
>>
>> I suppose people don't run i386 kernels or have different config.
>>
>>> Do you have some other hacks in this area? Are you testing actual
>>> plain 4.9, or do you (for example) still carry Arnd's patch around
>>> that turned out to not work (reverted by f27c2f69cc8e in my tree)?
>>
>> Not at all. This was plain 4.9 packaged by suse -- only rpm-related
>> fixes. I tried plain 4.9 without rpm right now with the same output:
>> # insmod soundcore.ko
>> [   31.582326] soundcore: disagrees about version of symbol mcount
>> [   31.586183] soundcore: Unknown symbol mcount (err -22)
>> insmod: ERROR: could not insert module soundcore.ko: Invalid parameters
> 
> I hit an mcount issue a while back (years?) which was due to building a
> driver with gcc v4.x while kernel was built using gcc v4.y. Not claiming
> that is your issue though.

I've usually had the same thing happen to me if things were compiled
with different gcc versions . Essentially in newer gcc (starting with
4.6 I believe) CC_USING_FENTRY is defined, meaning that there is no
mcount() symbol but rather __fentry__. This is the likely problem here.


> 
> Regards,
> Arend
>