[PATCH v2] checkpatch: warn about direct use of send_sig_info and force_sig_info

[Marco Elver <elver@google.com>]

Setting up siginfo and using send_sig_info() or 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>
Tested-by: Dwaipayan Ray <dwaipayanray1@gmail.com>
Signed-off-by: Marco Elver <elver@google.com>
---
v2:
* Use ?: because we don't need $2 (suggested by Dwaipayan Ray).

v1: https://lkml.kernel.org/r/20210506132827.3198497-1-elver@google.com
---
 scripts/checkpatch.pl | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index ccb412a74725..59f6eb3a2026 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)\(/) {
+			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