Add script finding recursive functions

scripts/recursion.pl

@@ -0,0 +1,43 @@
+#!/usr/bin/perl
+
+# Find functions making recursive calls to themselves.
+# (Multiple recursion where a() calls b() which calls a() not covered.)
+#
+# When the recursion depth might depend on data controlled by the attacker in
+# an unbounded way, those functions should use interation instead.
+#
+# Typical usage: scripts/recursion.pl library/*.c
+
+use warnings;
+use strict;
+
+use utf8;
+use open qw(:std utf8);
+
+# exclude functions that are ok:
+# - mpi_write_hlp: bounded by size of mpi, a compile-time constant
+my $known_ok = qr/mpi_write_hlp/;
+
+my $cur_name;
+my $inside;
+my @funcs;
+
+die "Usage: $0 file.c [...]\n" unless @ARGV;
+
+while (<>)
+{
+    if( /^[^\/#{}\s]/ && ! /\[.*]/ ) {
+        chomp( $cur_name = $_ ) unless $inside;
+    } elsif( /^{/ && $cur_name ) {
+        $inside = 1;
+        $cur_name =~ s/.* ([^ ]*)\(.*/$1/;
+    } elsif( /^}/ && $inside ) {
+        undef $inside;
+        undef $cur_name;
+    } elsif( $inside && /\b\Q$cur_name\E\([^)]/ ) {
+        push @funcs, $cur_name unless /$known_ok/;
+    }
+}
+
+print "$_\n" for @funcs;
+exit @funcs;