#!/usr/bin/perl -w
#
# Copywrite 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
#
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'\n";

        open(CIN, "$exec $file |") || die "Failed to run $exec $file";
        return;
    }
    die "No config file found";
}

find_config;

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

my @makefiles = `find $ksource -name Makefile`;
my %depends;
my %selects;
my %prompts;
my %objects;
my $var;
my $cont = 0;

# prevent recursion
my %read_kconfigs;

sub read_kconfig {
    my ($kconfig) = @_;

    my $state = "NONE";
    my $config;
    my @kconfigs;

    open(KIN, "$ksource/$kconfig") || die "Can't open $kconfig";
    while (<KIN>) {
        chomp;

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

        # configs found
        if (/^\s*config\s+(\S+)\s*$/) {
            $state = "NEW";
            $config = $1;

        # 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
            $prompt{$config} = 1;

        # 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) {
    chomp $makefile;

    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 bes 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;

# see what modules are loaded on this system
open(LIN,"/sbin/lsmod|") || die "Cant 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{$module})) {
        @arr = @{$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!!\n";
    }
}

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($prompt{$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\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})) {
            $setconfigs{$1} = $2;
        } elsif ($2 eq "m") {
            print "# $1 is not set\n";
            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 "\n";
    }
}