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From:   Marco Elver <elver@google.com>
Date:   Thu, 6 May 2021 18:11:40 +0200
Message-ID: <CANpmjNMsbyG7T2+BW2+QEtHnnznOVJQvydddOP+VLQZK8nTG2w@mail.gmail.com>
Subject: Re: [PATCH] checkpatch: warn about direct use of send_sig_info and force_sig_info
To:     Lukas Bulwahn <lukas.bulwahn@gmail.com>
Cc:     Dwaipayan Ray <dwaipayanray1@gmail.com>,
        "Eric W . Biederman" <ebiederm@xmission.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Andy Whitcroft <apw@canonical.com>,
        Joe Perches <joe@perches.com>
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Precedence: bulk

On Thu, 6 May 2021 at 18:02, Lukas Bulwahn <lukas.bulwahn@gmail.com> wrote:
> On Thu, May 6, 2021 at 5:02 PM Dwaipayan Ray <dwaipayanray1@gmail.com> wrote:
> > On Thu, May 6, 2021 at 6:59 PM Marco Elver <elver@google.com> wrote:
> > >
> > > Setting up siginfo and using send_sig_info() and force_sig_info()
> > > directly is discouraged. Instead, new code wanting to generate signals
> > > should use the appropriate helper specific to the signal.
> > >
> > > Eric mentioned that he'd like to make these static at some point, but
> > > until that can happen, let's try to avoid introducing new users of them.
> > >
> > > Cc: Eric W. Biederman <ebiederm@xmission.com>
> > > Signed-off-by: Marco Elver <elver@google.com>
> > > ---
> > > Eric,
> > >
> > > While siginfo doesn't need changing often, when it does, it's quite the
> > > adventure. We now have the various static asserts. The other thing is
> > > usage of {send,force}_sig_info.
> > >
> > > I think the best option right now is to teach checkpatch.pl about it
> > > until they become static.
> > >
> > > Fyi, I noticed one such new user here:
> > > https://lkml.kernel.org/r/20210421024826.13529-1-wangjunqiang@iscas.ac.cn
> > >
> > > Thanks,
> > > -- Marco
> > > ---
> > >  scripts/checkpatch.pl | 6 ++++++
> > >  1 file changed, 6 insertions(+)
> > >
> > > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> > > index ccb412a74725..3a86aafc3bcd 100755
> > > --- a/scripts/checkpatch.pl
> > > +++ b/scripts/checkpatch.pl
> > > @@ -7153,6 +7153,12 @@ sub process {
> > >                              "Where possible, use lockdep_assert_held instead of assertions based on spin_is_locked\n" . $herecurr);
> > >                 }
> > >
> > > +# check for direct use of send_sig_info(), force_sig_info()
> > > +               if ($line =~ /\b((force|send)_sig_info)\(/) {
> >
> > I think this might be a little better as:
> > if ($line =~ /\b((?:force|send)_sig_info)\(/) {
> >
> > Otherwise it's good as it is.
> > Tested-by: Dwaipayan Ray <dwaipayanray1@gmail.com>
> >
>
> Dwaipayan, do you want to also document this new rule on the
> checkpatch documentation?
> Marco, maybe you can assist us here with some pointer (lore.kernel.org
> link) to the original discussion you had.

It started somewhere here:
https://lkml.kernel.org/r/m17dkjttpj.fsf@fess.ebiederm.org

Eric has the full history here -- if I missed something, hopefully
he'll nack or ack.

Thanks,
-- Marco