#!/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;

# set the environment variable LOCALMODCONFIG_DEBUG to get
# debug output.
my $debugprint = 0;
$debugprint = 1 if (defined($ENV{LOCALMODCONFIG_DEBUG}));

sub dprint {
    return if (!$debugprint);
    print STDERR @_;
}

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 read_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'\n";

        open(my $infile, '-|', "$exec $file") || die "Failed to run $exec $file";
        my @x = <$infile>;
        close $infile;
        return @x;
    }
    die "No config file found";
}

my @config_file = read_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] ? $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 $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(my $kinfile, '<', $source) || die "Can't open $kconfig";
    while (<$kinfile>) {
        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*"(.*)"/) {
            my $kconfig = $1;
            # prevent reading twice.
            if (!defined($read_kconfigs{$kconfig})) {
                $read_kconfigs{$kconfig} = 1;
                read_kconfig($kconfig);
            }
            next;
        }

        # configs found
        if (/^\s*(menu)?config\s+(\S+)\s*$/) {
            $state = "NEW";
            $config = $2;

            # Add depends for 'if' nesting
            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+)/) {
            my $conf = $1;
            if (defined($selects{$conf})) {
                $selects{$conf} .= " " . $config;
            } else {
                $selects{$conf} = $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*$/) {
            $state = "NONE";
        }
    }
    close($kinfile);
}

if ($kconfig) {
    read_kconfig($kconfig);
}

# Makefiles can use variables to define their dependencies
sub convert_vars {
    my ($line, %vars) = @_;

    my $process = "";

    while ($line =~ s/^(.*?)(\$\((.*?)\))//) {
        my $start = $1;
        my $variable = $2;
        my $var = $3;

        if (defined($vars{$var})) {
            $process .= $start . $vars{$var};
        } else {
            $process .= $start . $variable;
        }
    }

    $process .= $line;

    return $process;
}

# Read all Makefiles to map the configs to the objects
foreach my $makefile (@makefiles) {

    my $line = "";
    my %make_vars;

    open(my $infile, '<', $makefile) || die "Can't open $makefile";
    while (<$infile>) {
        # if this line ends with a backslash, continue
        chomp;
        if (/^(.*)\\$/) {
            $line .= $1;
            next;
        }

        $line .= $_;
        $_ = $line;
        $line = "";

        my $objs;

        # Convert variables in a line (could define configs)
        $_ = convert_vars($_, %make_vars);

        # collect objects after obj-$(CONFIG_FOO_BAR)
        if (/obj-\$\((CONFIG_[^\)]*)\)\s*[+:]?=\s*(.*)/) {
            $var = $1;
            $objs = $2;

        # check if variables are set
        } elsif (/^\s*(\S+)\s*[:]?=\s*(.*\S)/) {
            $make_vars{$1} = $2;
        }
        if (defined($objs)) {
            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{$1} = \@arr;
                }
            }
        }
    }
    close($infile);
}

my %modules;
my $linfile;

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";
        }
    }

    my $otype = ( -x $lsmod_file) ? '-|' : '<';
    open($linfile, $otype, $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($linfile, '-|', $lsmod) || die "Can not call lsmod with $lsmod";
}

while (<$linfile>) {
        next if (/^Module/);  # Skip the first line.
        if (/^(\S+)/) {
                $modules{$1} = 1;
        }
}
close ($linfile);

# add to the configs hash all configs that are needed to enable
# a loaded module. This is a direct obj-${CONFIG_FOO} += bar.o
# where we know we need bar.o so we add FOO to the list.
my %configs;
foreach my $module (keys(%modules)) {
    if (defined($objects{$module})) {
        my @arr = @{$objects{$module}};
        foreach my $conf (@arr) {
            $configs{$conf} = $module;
            dprint "$conf added by direct ($module)\n";
            if ($debugprint) {
                my $c=$conf;
                $c =~ s/^CONFIG_//;
                if (defined($depends{$c})) {
                    dprint " deps = $depends{$c}\n";
                } else {
                    dprint " no deps\n";
                }
            }
        }
    } else {
        # Most likely, someone has a custom (binary?) module loaded.
        print STDERR "$module config not found!!\n";
    }
}

# Read the current config, and see what is enabled. We want to
# ignore configs that we would not enable anyway.

my %orig_configs;
my $valid = "A-Za-z_0-9";

foreach my $line (@config_file) {
    $_ = $line;

    if (/(CONFIG_[$valid]*)=(m|y)/) {
        $orig_configs{$1} = $2;
    }
}

my $repeat = 1;

my $depconfig;

#
# 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_depends
{
    my ($p) = @_;

    while ($p =~ /[$valid]/) {

        if ($p =~ /^[^$valid]*([$valid]+)/) {
            my $conf = "CONFIG_" . $1;

            $p =~ s/^[^$valid]*[$valid]+//;

            # We only need to process if the depend config is a module
            if (!defined($orig_configs{$conf}) || !$orig_configs{conf} eq "m") {
                next;
            }

            if (!defined($configs{$conf})) {
                # We must make sure that this config has its
                # dependencies met.
                $repeat = 1; # do again
                dprint "$conf selected by depend $depconfig\n";
                $configs{$conf} = 1;
            }
        } else {
            die "this should never happen";
        }
    }
}

# Select is treated a bit differently than depends. We call this
# when a config has no prompt and requires another config to be
# selected. We use to just select all configs that selected this
# config, but found that that can balloon into enabling hundreds
# of configs that we do not care about.
#
# The idea is we look at all the configs that select it. If one
# is already in our list of configs to enable, then there's nothing
# else to do. If there isn't, we pick the first config that was
# enabled in the orignal config and use that.
sub parse_config_selects
{
    my ($config, $p) = @_;

    my $next_config;

    while ($p =~ /[$valid]/) {

        if ($p =~ /^[^$valid]*([$valid]+)/) {
            my $conf = "CONFIG_" . $1;

            $p =~ s/^[^$valid]*[$valid]+//;

            # Make sure that this config exists in the current .config file
            if (!defined($orig_configs{$conf})) {
                dprint "$conf not set for $config select\n";
                next;
            }

            # Check if something other than a module selects this config
            if (defined($orig_configs{$conf}) && $orig_configs{$conf} ne "m") {
                dprint "$conf (non module) selects config, we are good\n";
                # we are good with this
                return;
            }
            if (defined($configs{$conf})) {
                dprint "$conf selects $config so we are good\n";
                # A set config selects this config, we are good
                return;
            }
            # Set this config to be selected
            if (!defined($next_config)) {
                $next_config = $conf;
            }
        } else {
            die "this should never happen";
        }
    }

    # If no possible config selected this, then something happened.
    if (!defined($next_config)) {
        print STDERR "WARNING: $config is required, but nothing in the\n";
        print STDERR "  current config selects it.\n";
        return;
    }

    # If we are here, then we found no config that is set and
    # selects this config. Repeat.
    $repeat = 1;
    # Make this config need to be selected
    $configs{$next_config} = 1;
    dprint "$next_config selected by select $config\n";
}

my %process_selects;

# loop through all configs, select their dependencies.
sub loop_depend {
    $repeat = 1;

    while ($repeat) {
        $repeat = 0;

      forloop:
        foreach my $config (keys %configs) {

            # If this config is not a module, we do not need to process it
            if (defined($orig_configs{$config}) && $orig_configs{$config} ne "m") {
                next forloop;
            }

            $config =~ s/^CONFIG_//;
            $depconfig = $config;

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

            # If the config has no prompt, then we need to check if a config
            # that is enabled selected it. Or if we need to enable one.
            if (!defined($prompts{$config}) && defined($selects{$config})) {
                $process_selects{$config} = 1;
            }
        }
    }
}

sub loop_select {

    foreach my $config (keys %process_selects) {
        $config =~ s/^CONFIG_//;

        dprint "Process select $config\n";

        # config has no prompt and must be selected.
        parse_config_selects $config, $selects{$config};
    }
}

while ($repeat) {
    # Get the first set of configs and their dependencies.
    loop_depend;

    $repeat = 0;

    # Now we need to see if we have to check selects;
    loop_select;
}           

my %setconfigs;

# Finally, read the .config file and turn off any module enabled that
# we could not find a reason to keep enabled.
foreach my $line (@config_file) {
    $_ = $line;

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

    if (/^(CONFIG.*)=(m|y)/) {
        if (defined($configs{$1})) {
            if ($localyesconfig) {
                $setconfigs{$1} = 'y';
                print "$1=y\n";
                next;
            } else {
                $setconfigs{$1} = $2;
            }
        } elsif ($2 eq "m") {
            print "# $1 is not set\n";
            next;
        }
    }
    print;
}

# 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 "\n";
    }
}