Re: linux-next: build warning after merge of the landlock tree

Arnd Bergmann
2023-10-03T13:40:56Z

On Tue, Oct 3, 2023, at 15:15, Mickaël Salaün wrote:
> PowerPC-64 follows the LP64 data model and then uses int-l64.h (instead of
> int-ll64.h like most architectures) for user space code.
>
> Here is the same code with the (suggested) "%lu" token on x86_86:
>
> samples/landlock/sandboxer.c: In function ‘populate_ruleset_net’:
> samples/landlock/sandboxer.c:170:77: error: format ‘%lu’ expects
> argument of type ‘long unsigned int’, but argument 3 has type ‘__u64’
> {aka ‘long long unsigned int’} [-Werror=format=]
> 170 | "Failed to update the ruleset
> with port \"%lu\": %s\n",
> |
> ~~^
> |
> |
> |
> long unsigned int
> |
> %llu
> 171 | net_port.port,
> strerror(errno));
> | ~~~~~~~~~~~~~
> | |
> | __u64 {aka long long
> unsigned int}
>
>
> We would then need to cast __u64 to unsigned long long to avoid this warning,
> which may look useless, of even buggy, for people taking a look at this sample.
>
> Anyway, it makes more sense to cast it to __u16 because it is the
> expected type for a TCP port. I'm updating the patch with that.
> Konstantin, please take this fix for the next series:
> https://git.kernel.org/mic/c/fc9de206a61a
>
>
> On Tue, Oct 03, 2023 at 02:27:37PM +1100, Stephen Rothwell wrote:
>> Hi all,
>>
>> After merging the landlock tree, today's linux-next build (powerpc
>> allyesconfig) produced this warning:
>>
>> samples/landlock/sandboxer.c: In function 'populate_ruleset_net':
>> samples/landlock/sandboxer.c:170:78: warning: format '%llu' expects argument of type 'long long unsigned int', but argument 3 has type '__u64' {aka 'long unsigned int'} [-Wformat=]
>> 170 | "Failed to update the ruleset with port \"%llu\": %s\n"

I think defining the __SANE_USERSPACE_TYPES__ macro should take care of this,
then __u64 has the same type as it does in the kernel.

Arnd