#!/usr/bin/perl
#
# Copyright (c) 2009, 2011 Slade Maurer, Alexander Sviridenko. All rights reserved.
# (see the pod text in Binutils::Objdump module for use and distribution rights)
#

our $VERSION = '0.1.2';

use Getopt::Long;
use Binutils::Objdump qw(:ALL);

GetOptions(
    'h|help' => \&print_usage,
    'V|version' => \&print_version,
);

$input = shift @ARGV || 'a.out';

if (!-e $input || !-f $input) {
    die "$input cannot be found. Exit.\n";
}

objdumpopt("-dTx --prefix-addresses");
objdump($input);

# Reading strings ...

foreach (objdump_section_headers()) {
    if (/.rodata/) {
        ($rubbish, $rest) = split /.rodata/, $_, 2;
        ($rubbish, $rest) = split /0/, $rest, 2;
        @numbers = split /  /, $rest, 5;
        $size = hex($numbers[0]);
        $starting_address = hex($numbers[1]);
        $end_address = $starting_address + $size;
        $offset = hex($numbers[3]);
        open  INPUT, '<', $input;
        seek  INPUT, $offset, 0;
        read  INPUT, $cadena, $size;
        close INPUT;
    }
}

# Processing symbol table ...

foreach (objdump_symtab()) {
    last if /^\n/;
    @st_element = split(/ /, $_);
    $_ = $st_element[$#st_element];
#    chop;
    $st_element[0] =~ s/^[0]+([1-9])/$1/;
    $symbol_table{$st_element[0]} = $_;
}

# Analysis ...

foreach (objdump_sec_disasm('.text')) {
    s/0x//g;
    s/<.*?>//g;
    s/  / /g;

    if (/j/) {
        ($direccion,$inst,$destino) = split / /, $_, 3;
        $destino = ~s/ //g;
        chomp $destino;
        $salto{$destino} .= ($direccion." \; ");
    }
    elsif (/call/) {
        ($direccion, $inst, $destino) = split / /, $_, 3;
        $destino =~ s/ //g;
        chomp $destino;
        $call{$destino} .= ($direccion." \; ");
    }
}

# Writting references ...

$char=".";
$counter=0;
$i=0;
foreach (objdump_sec_disasm('.text')) {
    $counter++;
    $copia = $_;

    s/0x//g;
    s/\<.*?\>//ge;
    s/  / /g;

    ($direccion, $inst, $destino) = split / /, $_, 3;
    $destino =~ s/^[0]+([1-9])/$1/;
    $direccion =~ s/^[0]+([1-9])/$1/;

    if (defined $symbol_table{$direccion}) {
        print "\nFunction : ".$symbol_table{$direccion};
        print "\n\n";
    }

    if (/call/) {
        $destino =~ s/ //g;
        chomp $destino;

        if (defined $symbol_table{$destino}) {
            print "\n  Reference to function : ".$symbol_table{$destino}."\n\n";
        }
    }

    if (defined $salto{$direccion}) {
        print "\n  Referenced from jump at ".$salto{$direccion}."\n\n";
    }

    if (defined($call{$direccion})) {
        print "\n  Referenced from call at ".$call{$direccion}."\n\n";
    }

    if (/\$/){
        ($instruccion, $operand) = split /\$/, $_, 2;

        if (!/push/) {
            ($operand, undef) = split /\,/, $operand, 2;
        }
        chomp $operand;
        $offset = hex $operand;
        if (($offset <= $end_address)
             && ($offset >= $starting_address))
        {
            $auxiliar = substr($cadena, $offset-$starting_address);
            $length = index($auxiliar, pack("x"));
            $auxiliar=substr($auxiliar, 0, $length);       
            $auxiliar =~ s/\n//g;
            print "\n  Possible reference to string :\n";
            print "\"$auxiliar\"\n\n"
        }       

        if ($symbol_table{$operand}) {
            print "\n  Appeared : ". $symbol_table{$operand} ."\n\n";
        }
    }

    print "$copia\n";
}

exit(0);

sub print_usage
{
    print "odasm $VERSION\n";
    print "Usage: odasm [OPTION]... exe_file\n\n";
    print "  -V, --version    display the version of odasm and exit.\n";
    print "  -h, --help       print this help.\n";
    exit(0);
}

sub print_version
{
    print "odasm $VERSION\n";
    print "Binutils::Objdump $Binutils::Objdump::VERSION\n\n";
    print "Copyright (c) 2009, 2011 Slade Maurer, Alexander Sviridenko. All rights reserved.\n";
    print "(see the pod text in Binutils::Objdump module for use and distribution rights)\n";
    exit(0);
}

__END__

=head1 NAME

odasm - A disassembler written on Perl and based on Bintuils::Objdump module

=head1 SYNOPSIS

    odasm [OPTIONS] exe_file

    odasm -V

    odasm -h

=head1 DESCRIPTION

This disassembler based on linux disassembler 2.0799 by SiuL+Hacky, and 
written with help of L<Binutils::Objdump> module.

This script allows to show you: appeared functions and symbols, possible 
references to strings, references from C<jump>s and C<call>s.

=head1 AUTHORS

Alexander Sviridenko <oleks.sviridenko@gmail.com>

Slade Maurer <slade@computer.org>

=head1 COPYRIGHT

Copyright (c) 2009, 2011 Slade Maurer, Alexander Sviridenko. All rights reserved.
(see the pod text in L<Binutils::Objdump> module for use and distribution rights)

=head1 SEE ALSO

Binutils::Objdump(1)

=cut