Re: [RFC PATCH 0/2] improve vmalloc allocation

Joel Fernandes
2018-10-23T19:30:51Z

On Tue, Oct 23, 2018 at 11:13:36AM -0600, Shuah Khan wrote:
> On 10/23/2018 11:05 AM, Michal Hocko wrote:
> > On Tue 23-10-18 08:26:40, Matthew Wilcox wrote:
> >> On Tue, Oct 23, 2018 at 09:02:56AM -0600, Shuah Khan wrote:
> > [...]
> >>> The way it can be handled is by adding a test module under lib. test_kmod,
> >>> test_sysctl, test_user_copy etc.
> >>
> >> The problem is that said module can only invoke functions which are
> >> exported using EXPORT_SYMBOL. And there's a cost to exporting them,
> >> which I don't think we're willing to pay, purely to get test coverage.
> >
> > Yes, I think we do not want to export internal functionality which might
> > be still interesting for the testing coverage. Maybe we want something
> > like EXPORT_SYMBOL_KSELFTEST which would allow to link within the
> > kselftest machinery but it wouldn't allow the same for general modules
> > and will not give any API promisses.
> >
>
> I like this proposal. I think we will open up lot of test opportunities with
> this approach.
>
> Maybe we can use this stress test as a pilot and see where it takes us.

I am a bit worried that such an EXPORT_SYMBOL_KSELFTEST mechanism can be abused by
out-of-tree module writers to call internal functionality.

How would you prevent that?

thanks,

- Joel