#!/usr/bin/perl -w
  #

  # Copyright 2005-2009 - Steven Rostedt

  # Licensed under the terms of the GNU GPL License version 2
  #
  #  It's simple enough to figure out how this works.
  #  If not, then you can ask me at stripconfig@goodmis.org
  #
  # What it does?
  #
  #   If you have installed a Linux kernel from a distribution
  #   that turns on way too many modules than you need, and
  #   you only want the modules you use, then this program
  #   is perfect for you.
  #
  #   It gives you the ability to turn off all the modules that are
  #   not loaded on your system.
  #
  # Howto:
  #
  #  1. Boot up the kernel that you want to stream line the config on.
  #  2. Change directory to the directory holding the source of the
  #       kernel that you just booted.
  #  3. Copy the configuraton file to this directory as .config
  #  4. Have all your devices that you need modules for connected and
  #      operational (make sure that their corresponding modules are loaded)
  #  5. Run this script redirecting the output to some other file
  #       like config_strip.
  #  6. Back up your old config (if you want too).
  #  7. copy the config_strip file to .config
  #  8. Run "make oldconfig"
  #
  #  Now your kernel is ready to be built with only the modules that
  #  are loaded.
  #
  # Here's what I did with my Debian distribution.
  #
  #    cd /usr/src/linux-2.6.10
  #    cp /boot/config-2.6.10-1-686-smp .config
  #    ~/bin/streamline_config > config_strip
  #    mv .config config_sav
  #    mv config_strip .config
  #    make oldconfig
  #

  use strict;

  use Getopt::Long;

  my $config = ".config";

  my $uname = `uname -r`;
  chomp $uname;
  
  my @searchconfigs = (
  	{

  	    "file" => ".config",
  	    "exec" => "cat",
  	},
  	{

  	    "file" => "/proc/config.gz",
  	    "exec" => "zcat",
  	},
  	{

  	    "file" => "/boot/config-$uname",
  	    "exec" => "cat",
  	},
  	{

  	    "file" => "/boot/vmlinuz-$uname",
  	    "exec" => "scripts/extract-ikconfig",
  	    "test" => "scripts/extract-ikconfig",
  	},
  	{
  	    "file" => "vmlinux",
  	    "exec" => "scripts/extract-ikconfig",
  	    "test" => "scripts/extract-ikconfig",
  	},
  	{
  	    "file" => "/lib/modules/$uname/kernel/kernel/configs.ko",
  	    "exec" => "scripts/extract-ikconfig",
  	    "test" => "scripts/extract-ikconfig",
  	},
  	{
  	    "file" => "kernel/configs.ko",
  	    "exec" => "scripts/extract-ikconfig",
  	    "test" => "scripts/extract-ikconfig",
  	},
  	{
  	    "file" => "kernel/configs.o",
  	    "exec" => "scripts/extract-ikconfig",
  	    "test" => "scripts/extract-ikconfig",
  	},

  );
  
  sub find_config {
      foreach my $conf (@searchconfigs) {
  	my $file = $conf->{"file"};
  
  	next if ( ! -f "$file");
  
  	if (defined($conf->{"test"})) {
  	    `$conf->{"test"} $conf->{"file"} 2>/dev/null`;
  	    next if ($?);
  	}
  
  	my $exec = $conf->{"exec"};
  
  	print STDERR "using config: '$file'
  ";
  
  	open(CIN, "$exec $file |") || die "Failed to run $exec $file";
  	return;
      }
      die "No config file found";
  }
  
  find_config;

  # Parse options
  my $localmodconfig = 0;
  my $localyesconfig = 0;
  
  GetOptions("localmodconfig" => \$localmodconfig,
  	   "localyesconfig" => \$localyesconfig);

  # Get the build source and top level Kconfig file (passed in)
  my $ksource = $ARGV[0];
  my $kconfig = $ARGV[1];

  my $lsmod_file = $ENV{'LSMOD'};

  my @makefiles = `find $ksource -name Makefile 2>/dev/null`;
  chomp @makefiles;

  my %depends;
  my %selects;
  my %prompts;
  my %objects;
  my $var;

  my $iflevel = 0;
  my @ifdeps;

  # prevent recursion
  my %read_kconfigs;
  
  sub read_kconfig {
      my ($kconfig) = @_;
  
      my $state = "NONE";
      my $config;
      my @kconfigs;

      my $cont = 0;
      my $line;

      my $source = "$ksource/$kconfig";
      my $last_source = "";
  
      # Check for any environment variables used
      while ($source =~ /\$(\w+)/ && $last_source ne $source) {
  	my $env = $1;
  	$last_source = $source;
  	$source =~ s/\$$env/$ENV{$env}/;
      }
  
      open(KIN, "$source") || die "Can't open $kconfig";

      while (<KIN>) {
  	chomp;

  	# Make sure that lines ending with \ continue
  	if ($cont) {
  	    $_ = $line . " " . $_;
  	}
  
  	if (s/\\$//) {
  	    $cont = 1;
  	    $line = $_;
  	    next;
  	}
  
  	$cont = 0;

  	# collect any Kconfig sources
  	if (/^source\s*"(.*)"/) {
  	    $kconfigs[$#kconfigs+1] = $1;
  	}
  
  	# configs found

  	if (/^\s*(menu)?config\s+(\S+)\s*$/) {

  	    $state = "NEW";

  	    $config = $2;

  	    for (my $i = 0; $i < $iflevel; $i++) {
  		if ($i) {
  		    $depends{$config} .= " " . $ifdeps[$i];
  		} else {
  		    $depends{$config} = $ifdeps[$i];
  		}
  		$state = "DEP";
  	    }

  	# collect the depends for the config
  	} elsif ($state eq "NEW" && /^\s*depends\s+on\s+(.*)$/) {
  	    $state = "DEP";
  	    $depends{$config} = $1;
  	} elsif ($state eq "DEP" && /^\s*depends\s+on\s+(.*)$/) {
  	    $depends{$config} .= " " . $1;
  
  	# Get the configs that select this config
  	} elsif ($state ne "NONE" && /^\s*select\s+(\S+)/) {
  	    if (defined($selects{$1})) {
  		$selects{$1} .= " " . $config;
  	    } else {
  		$selects{$1} = $config;
  	    }
  
  	# configs without prompts must be selected
  	} elsif ($state ne "NONE" && /^\s*tristate\s\S/) {
  	    # note if the config has a prompt

  	    $prompts{$config} = 1;

  	# Check for if statements
  	} elsif (/^if\s+(.*\S)\s*$/) {
  	    my $deps = $1;
  	    # remove beginning and ending non text
  	    $deps =~ s/^[^a-zA-Z0-9_]*//;
  	    $deps =~ s/[^a-zA-Z0-9_]*$//;
  
  	    my @deps = split /[^a-zA-Z0-9_]+/, $deps;
  
  	    $ifdeps[$iflevel++] = join ':', @deps;
  
  	} elsif (/^endif/) {
  
  	    $iflevel-- if ($iflevel);

  	# stop on "help"
  	} elsif (/^\s*help\s*$/) {
  	    $state = "NONE";
  	}
      }
      close(KIN);
  
      # read in any configs that were found.
      foreach $kconfig (@kconfigs) {
  	if (!defined($read_kconfigs{$kconfig})) {
  	    $read_kconfigs{$kconfig} = 1;
  	    read_kconfig($kconfig);
  	}
      }
  }
  
  if ($kconfig) {
      read_kconfig($kconfig);
  }
  
  # Read all Makefiles to map the configs to the objects
  foreach my $makefile (@makefiles) {

      my $cont = 0;

      open(MIN,$makefile) || die "Can't open $makefile";
      while (<MIN>) {
  	my $objs;
  
  	# is this a line after a line with a backslash?
  	if ($cont && /(\S.*)$/) {
  	    $objs = $1;
  	}
  	$cont = 0;
  
  	# collect objects after obj-$(CONFIG_FOO_BAR)
  	if (/obj-\$\((CONFIG_[^\)]*)\)\s*[+:]?=\s*(.*)/) {
  	    $var = $1;
  	    $objs = $2;
  	}
  	if (defined($objs)) {
  	    # test if the line ends with a backslash
  	    if ($objs =~ m,(.*)\\$,) {
  		$objs = $1;
  		$cont = 1;
  	    }
  
  	    foreach my $obj (split /\s+/,$objs) {
  		$obj =~ s/-/_/g;
  		if ($obj =~ /(.*)\.o$/) {

  		    # Objects may be enabled by more than one config.

  		    # Store configs in an array.
  		    my @arr;
  
  		    if (defined($objects{$1})) {
  			@arr = @{$objects{$1}};
  		    }
  
  		    $arr[$#arr+1] = $var;
  
  		    # The objects have a hash mapping to a reference
  		    # of an array of configs.
  		    $objects{$1} = \@arr;
  		}
  	    }
  	}
      }
      close(MIN);
  }
  
  my %modules;

  if (defined($lsmod_file)) {
      if ( ! -f $lsmod_file) {

  	if ( -f $ENV{'objtree'}."/".$lsmod_file) {
  	    $lsmod_file = $ENV{'objtree'}."/".$lsmod_file;
  	} else {
  		die "$lsmod_file not found";
  	}

      }
      if ( -x $lsmod_file) {
  	# the file is executable, run it
  	open(LIN, "$lsmod_file|");
      } else {
  	# Just read the contents
  	open(LIN, "$lsmod_file");

      }

  } else {
  
      # see what modules are loaded on this system
      my $lsmod;

      foreach my $dir ( ("/sbin", "/bin", "/usr/sbin", "/usr/bin") ) {

  	if ( -x "$dir/lsmod" ) {
  	    $lsmod = "$dir/lsmod";
  	    last;
  	}

  }

      if (!defined($lsmod)) {
  	# try just the path
  	$lsmod = "lsmod";
      }
  
      open(LIN,"$lsmod|") || die "Can not call lsmod with $lsmod";

  }

  while (<LIN>) {
  	next if (/^Module/);  # Skip the first line.
  	if (/^(\S+)/) {
  		$modules{$1} = 1;
  	}
  }
  close (LIN);
  
  # add to the configs hash all configs that are needed to enable
  # a loaded module.
  my %configs;
  foreach my $module (keys(%modules)) {
      if (defined($objects{$module})) {

  	my @arr = @{$objects{$module}};

  	foreach my $conf (@arr) {
  	    $configs{$conf} = $module;
  	}
      } else {
  	# Most likely, someone has a custom (binary?) module loaded.
  	print STDERR "$module config not found!!
  ";
      }
  }
  
  my $valid = "A-Za-z_0-9";
  my $repeat = 1;
  
  #
  # Note, we do not care about operands (like: &&, ||, !) we want to add any
  # config that is in the depend list of another config. This script does
  # not enable configs that are not already enabled. If we come across a
  # config A that depends on !B, we can still add B to the list of depends
  # to keep on. If A was on in the original config, B would not have been
  # and B would not be turned on by this script.
  #
  sub parse_config_dep_select
  {
      my ($p) = @_;
  
      while ($p =~ /[$valid]/) {
  
  	if ($p =~ /^[^$valid]*([$valid]+)/) {
  	    my $conf = "CONFIG_" . $1;
  
  	    $p =~ s/^[^$valid]*[$valid]+//;
  
  	    if (!defined($configs{$conf})) {
  		# We must make sure that this config has its
  		# dependencies met.
  		$repeat = 1; # do again
  		$configs{$conf} = 1;
  	    }
  	} else {
  	    die "this should never happen";
  	}
      }
  }
  
  while ($repeat) {
      $repeat = 0;
  
      foreach my $config (keys %configs) {
  	$config =~ s/^CONFIG_//;

  	if (defined($depends{$config})) {
  	    # This config has dependencies. Make sure they are also included
  	    parse_config_dep_select $depends{$config};

  	}

  	if (defined($prompts{$config}) || !defined($selects{$config})) {

  	    next;
  	}
  
  	# config has no prompt and must be selected.
  	parse_config_dep_select $selects{$config};
      }
  }
  
  my %setconfigs;
  
  # Finally, read the .config file and turn off any module enabled that
  # we could not find a reason to keep enabled.
  while(<CIN>) {

  
      if (/CONFIG_IKCONFIG/) {
  	if (/# CONFIG_IKCONFIG is not set/) {
  	    # enable IKCONFIG at least as a module
  	    print "CONFIG_IKCONFIG=m
  ";
  	    # don't ask about PROC

  	    print "# CONFIG_IKCONFIG_PROC is not set
  ";

  	} else {
  	    print;
  	}
  	next;
      }
  
      if (/^(CONFIG.*)=(m|y)/) {
  	if (defined($configs{$1})) {

  	    if ($localyesconfig) {
  	        $setconfigs{$1} = 'y';
  	    } else {
  	        $setconfigs{$1} = $2;
  	    }

  	} elsif ($2 eq "m") {
  	    print "# $1 is not set
  ";

  	    next;

  	}

      }

      print;

  }
  close(CIN);
  
  # Integrity check, make sure all modules that we want enabled do
  # indeed have their configs set.
  loop:
  foreach my $module (keys(%modules)) {
      if (defined($objects{$module})) {
  	my @arr = @{$objects{$module}};
  	foreach my $conf (@arr) {
  	    if (defined($setconfigs{$conf})) {
  		next loop;
  	    }
  	}
  	print STDERR "module $module did not have configs";
  	foreach my $conf (@arr) {
  	    print STDERR " " , $conf;
  	}
  	print STDERR "
  ";
      }
  }