[Linux-kernel-mentees] [RFC PATCH] checkpatch: add shebang check to EXECUTE_PERMISSIONS

[Ujjwal Kumar]

checkpatch.pl checks for invalid EXECUTE_PERMISSIONS on source
files. The script leverages filename extensions and its path in
the repository to decide whether to allow execute permissions on
the file or not.

Based on current check conditions, a perl script file having
execute permissions, without '.pl' extension in its filename
and not belonging to 'scripts/' directory is reported as ERROR
which is a false-positive.

Adding a shebang check along with current conditions will make
the check more generalised and improve checkpatch reports.
To do so, without breaking the core design decision of checkpatch,
we can fetch the first line from the patch itself and match it for
a shebang pattern.

There can be cases where the first line is not part of the patch.
In that case there may be a false-positive report but in the end we
will have less false-positives as we will be handling some of the
unhandled cases.

Signed-off-by: Ujjwal Kumar <ujjwalkumar0501 at gmail.com>
---
Apologies, I forgot to include linux-kernel at vger.kernel.org so I'm
now resending.

 scripts/checkpatch.pl | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index fab38b493cef..e596d30794bf 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -1795,6 +1795,23 @@ sub get_stat_here {
 	return $herectx;
 }

+sub get_shebang {
+	my ($linenr, $realfile) = @_;
+	my $rawline = "";
+	my $shebang = "";
+
+	$rawline = raw_line($linenr, 3);
+	if (defined $rawline &&
+		$rawline =~ /^\@\@ -\d+(?:,\d+)? \+(\d+)(,(\d+))? \@\@/) {
+		if (defined $1 && $1 == 1) {
+			$shebang = raw_line($linenr, 4);
+			$shebang = substr $shebang, 1;
+		}
+	}
+
+	return $shebang;
+}
+
 sub cat_vet {
 	my ($vet) = @_;
 	my ($res, $coded);
@@ -2680,7 +2697,9 @@ sub process {
 # Check for incorrect file permissions
 		if ($line =~ /^new (file )?mode.*[7531]\d{0,2}$/) {
 			my $permhere = $here . "FILE: $realfile\n";
+			my $shebang = get_shebang($linenr, $realfile);
 			if ($realfile !~ m at scripts/@ &&
+			    $shebang !~ /^#!\s*(\/\w)+.*/ &&
 			    $realfile !~ /\.(py|pl|awk|sh)$/) {
 				ERROR("EXECUTE_PERMISSIONS",
 				      "do not set execute permissions for source files\n" . $permhere);

base-commit: d67bc7812221606e1886620a357b13f906814af7
--
2.26.2