2 files changed, 199 insertions, 1 deletions

diff --git a/Makefile b/Makefile
index 95160e5c70e8..e1c5ae8a8162 100644
--- a/Makefile
+++ b/Makefile
@@ -1026,6 +1026,10 @@ include/linux/version.h: $(srctree)/Makefile FORCE
 include/linux/utsrelease.h: include/config/kernel.release FORCE
         $(call filechk,utsrelease.h)
 
+PHONY += headerdep
+headerdep:
+        $(Q)find include/ -name '*.h' | xargs --max-args 1 scripts/headerdep.pl
+
 # ---------------------------------------------------------------------------
 
 PHONY += depend dep
@@ -1274,7 +1278,8 @@ help:
         @echo  '  versioncheck    - Sanity check on version.h usage'
         @echo  '  includecheck    - Check for duplicate included header files'
         @echo  '  export_report   - List the usages of all exported symbols'
-        @echo  '  headers_check   - Sanity check on exported headers'; \
+        @echo  '  headers_check   - Sanity check on exported headers'
+        @echo  '  headerdep       - Detect inclusion cycles in headers'; \
          echo  ''
         @echo  'Kernel packaging:'
         @$(MAKE) $(build)=$(package-dir) help
diff --git a/scripts/headerdep.pl b/scripts/headerdep.pl
new file mode 100755
index 000000000000..97399da89ef2
--- /dev/null
+++ b/scripts/headerdep.pl
@@ -0,0 +1,193 @@
+#! /usr/bin/perl
+#
+# Detect cycles in the header file dependency graph
+# Vegard Nossum <vegardno@ifi.uio.no>
+#
+
+use strict;
+use warnings;
+
+use Getopt::Long;
+
+my $opt_all;
+my @opt_include;
+my $opt_graph;
+
+&Getopt::Long::Configure(qw(bundling pass_through));
+&GetOptions(
+        help    => \&help,
+        version => \&version,
+
+        all     => \$opt_all,
+        I       => \@opt_include,
+        graph   => \$opt_graph,
+);
+
+push @opt_include, 'include';
+my %deps = ();
+my %linenos = ();
+
+my @headers = grep { strip($_) } @ARGV;
+
+parse_all(@headers);
+
+if($opt_graph) {
+        graph();
+} else {
+        detect_cycles(@headers);
+}
+
+
+sub help {
+        print "Usage: $0 [options] file...\n";
+        print "\n";
+        print "Options:\n";
+        print "  --all\n";
+        print "  --graph\n";
+        print "\n";
+        print "  -I includedir\n";
+        print "\n";
+        print "To make nice graphs, try:\n";
+        print "  $0 --graph include/linux/kernel.h | dot -Tpng -o graph.png\n";
+        exit;
+}
+
+sub version {
+        print "headerdep version 2\n";
+        exit;
+}
+
+# Get a file name that is relative to our include paths
+sub strip {
+        my $filename = shift;
+
+        for my $i (@opt_include) {
+                my $stripped = $filename;
+                $stripped =~ s/^$i\///;
+
+                return $stripped if $stripped ne $filename;
+        }
+
+        return $filename;
+}
+
+# Search for the file name in the list of include paths
+sub search {
+        my $filename = shift;
+        return $filename if -f $filename;
+
+        for my $i (@opt_include) {
+                my $path = "$i/$filename";
+                return $path if -f $path;
+        }
+
+        return undef;
+}
+
+sub parse_all {
+        # Parse all the headers.
+        my @queue = @_;
+        while(@queue) {
+                my $header = pop @queue;
+                next if exists $deps{$header};
+
+                $deps{$header} = [] unless exists $deps{$header};
+
+                my $path = search($header);
+                next unless $path;
+
+                open(my $file, '<', $path) or die($!);
+                chomp(my @lines = <$file>);
+                close($file);
+
+                for my $i (0 .. $#lines) {
+                        my $line = $lines[$i];
+                        if(my($dep) = ($line =~ m/^#\s*include\s*<(.*?)>/)) {
+                                push @queue, $dep;
+                                push @{$deps{$header}}, [$i + 1, $dep];
+                        }
+                }
+        }
+}
+
+sub print_cycle {
+        # $cycle[n] includes $cycle[n + 1];
+        # $cycle[-1] will be the culprit
+        my $cycle = shift;
+
+        # Adjust the line numbers
+        for my $i (0 .. $#$cycle - 1) {
+                $cycle->[$i]->[0] = $cycle->[$i + 1]->[0];
+        }
+        $cycle->[-1]->[0] = 0;
+
+        my $first = shift @$cycle;
+        my $last = pop @$cycle;
+
+        my $msg = "In file included";
+        printf "%s from %s,\n", $msg, $last->[1] if defined $last;
+
+        for my $header (reverse @$cycle) {
+                printf "%s from %s:%d%s\n",
+                        " " x length $msg,
+                        $header->[1], $header->[0],
+                        $header->[1] eq $last->[1] ? ' <-- here' : '';
+        }
+
+        printf "%s:%d: warning: recursive header inclusion\n",
+                $first->[1], $first->[0];
+}
+
+# Find and print the smallest cycle starting in the specified node.
+sub detect_cycles {
+        my @queue = map { [[0, $_]] } @_;
+        while(@queue) {
+                my $top = pop @queue;
+                my $name = $top->[-1]->[1];
+
+                for my $dep (@{$deps{$name}}) {
+                        my $chain = [@$top, [$dep->[0], $dep->[1]]];
+
+                        # If the dep already exists in the chain, we have a
+                        # cycle...
+                        if(grep { $_->[1] eq $dep->[1] } @$top) {
+                                print_cycle($chain);
+                                next if $opt_all;
+                                return;
+                        }
+
+                        push @queue, $chain;
+                }
+        }
+}
+
+sub mangle {
+        $_ = shift;
+        s/\//__/g;
+        s/\./_/g;
+        s/-/_/g;
+        $_;
+}
+
+# Output dependency graph in GraphViz language.
+sub graph {
+        print "digraph {\n";
+
+        print "\t/* vertices */\n";
+        for my $header (keys %deps) {
+                printf "\t%s [label=\"%s\"];\n",
+                        mangle($header), $header;
+        }
+
+        print "\n";
+
+        print "\t/* edges */\n";
+        for my $header (keys %deps) {
+                for my $dep (@{$deps{$header}}) {
+                        printf "\t%s -> %s;\n",
+                                mangle($header), mangle($dep->[1]);
+                }
+        }
+
+        print "}\n";
+}