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

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Date:   Tue, 3 Oct 2023 15:15:22 +0200
From:   Mickaël Salaün <mic@...ikod.net>
To:     Stephen Rothwell <sfr@...b.auug.org.au>
Cc:     Konstantin Meskhidze <konstantin.meskhidze@...wei.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        willemdebruijn.kernel@...il.com, gnoack3000@...il.com,
        linux-security-module@...r.kernel.org, netdev@...r.kernel.org,
        netfilter-devel@...r.kernel.org, yusongping@...wei.com,
        artem.kuzin@...wei.com, Geert Uytterhoeven <geert@...ux-m68k.org>,
        Arnd Bergmann <arnd@...db.de>,
        Randy Dunlap <rdunlap@...radead.org>
Subject: Re: linux-next: build warning after merge of the landlock tree

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",
>       |                                                                           ~~~^
>       |                                                                              |
>       |                                                                              long long unsigned int
>       |                                                                           %lu
>   171 |                                 net_port.port, strerror(errno));
>       |                                 ~~~~~~~~~~~~~                                 
>       |                                         |
>       |                                         __u64 {aka long unsigned int}
> 
> Introduced by commit
> 
>   24889e7a2079 ("samples/landlock: Add network demo")
> 
> -- 
> Cheers,
> Stephen Rothwell