kbuild: check for leaked CONFIG_ symbols to userspace

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

scripts/headers_check.pl

@@ -16,7 +16,7 @@
 #
 # 2) It is checked that prototypes does not use "extern"
 #
-# 3) TODO: check for leaked CONFIG_ symbols
+# 3) Check for leaked CONFIG_ symbols
 
 use strict;
 
@@ -36,6 +36,7 @@ foreach my $file (@files) {
 		$lineno++;
 		check_include();
 		check_prototypes();
+		check_config();
 	}
 	close FH;
 }
@@ -64,3 +65,11 @@ sub check_prototypes
 		printf STDERR "$filename:$lineno: extern's make no sense in userspace\n";
 	}
 }
+
+sub check_config
+{
+	if ($line =~ m/[^a-zA-Z0-9_]+CONFIG_([a-zA-Z0-9]+)[^a-zA-Z0-9]/) {
+		printf STDERR "$filename:$lineno: leaks CONFIG_$1 to userspace where it is not valid\n";
+	}
+}
+