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From:   Dwaipayan Ray <dwaipayanray1@gmail.com>
Date:   Thu, 6 May 2021 20:32:43 +0530
Message-ID: <CABJPP5D_azxBiKq08_m_WVmcEy8qbMCa0EsAgu57t2T+eDJA0A@mail.gmail.com>
Subject: Re: [PATCH] checkpatch: warn about direct use of send_sig_info and force_sig_info
To:     Marco Elver <elver@google.com>
Cc:     "Eric W . Biederman" <ebiederm@xmission.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Andy Whitcroft <apw@canonical.com>,
        Joe Perches <joe@perches.com>,
        Lukas Bulwahn <lukas.bulwahn@gmail.com>
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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>

Thanks,
Dwaipayan.

> +                       WARN("USE_SIGINFO_HELPER",
> +                            "Where possible, avoid using '$1' directly and use a signal-specific helper setting required siginfo fields (see include/linux/sched/signal.h).\n" . $herecurr);
> +               }
> +
>  # check for deprecated apis
>                 if ($line =~ /\b($deprecated_apis_search)\b\s*\(/) {
>                         my $deprecated_api = $1;
> --
> 2.31.1.607.g51e8a6a459-goog
>