Re: [PATCH] x86/kbuild: enable modversions for symbols exported from asm

Hannes Frederic Sowa
2016-12-02T14:36:46Z

On 01.12.2016 17:12, Michal Marek wrote:
> On 2016-12-01 04:39, Nicholas Piggin wrote:
>> On Thu, 01 Dec 2016 02:35:54 +0000
>> Ben Hutchings <ben@decadent.org.uk> wrote:
>>> As I understand it, genksyms incorporates the definitions of a
>>> function's parameter and return types - not just their names - and all
>>> the types they refer to, recursively. So a structure size change
>>> should change the version of all functions where the function and its
>>> caller pass that structure between them, however indirectly. It finds
>>> such indirect ABI breakage for me fairly regularly, though of course I
>>> don't know that it finds everything.
>>
>> It is only the type name.
>>
>> Not only that but even if you did extend it further to structure type
>> arrangement then you still have to deal with other structures followed
>> via pointers. Or (rarer but not unheard of):
>>
>> - changes to structures without changes of the types of their members
>> - changes to arguments without changes of their type
>
> This is already covered by genksyms. Try make V=1 with
> CONFIG_MODVERSIONS=y and add the -D option to one of the genksyms
> command. I wanted to paste the expanded signature for
> register_filesystem() as an example, but vger would probably drop the
> mail for being too big :).

It is easier to just use e.g. `make net/core/dev.symtypes` and look at
the generated file.

Bye,
Hannes