#!/usr/bin/env perl
# ----------------------------------------------------------------------
# mkknlimg by Phil Elwell for Raspberry Pi
# based on extract-ikconfig by Dick Streefland
#
# (c) 2009,2010 Dick Streefland <dick@streefland.net>
# (c) 2014,2015 Raspberry Pi (Trading) Limited <info@raspberrypi.org>
#
# Licensed under the terms of the GNU General Public License.
# ----------------------------------------------------------------------

use strict;
use warnings;
use integer;

use constant FLAG_PI   => 0x01;
use constant FLAG_DTOK => 0x02;
use constant FLAG_DDTK => 0x04;
use constant FLAG_270X => 0x08;
use constant FLAG_283X => 0x10;

my $trailer_magic = 'RPTL';

my $tmpfile1 = "/tmp/mkknlimg_$$.1";
my $tmpfile2 = "/tmp/mkknlimg_$$.2";

my $dtok = 0;
my $ddtk = 0;
my $is_270x = 0;
my $is_283x = 0;

while (@ARGV && ($ARGV[0] =~ /^-/))
{
    my $arg = shift(@ARGV);
    if ($arg eq '--dtok')
    {
	$dtok = 1;
    }
    elsif ($arg eq '--ddtk')
    {
	$ddtk = 1;
    }
    elsif ($arg eq '--270x')
    {
	$is_270x = 1;
    }
    elsif ($arg eq '--283x')
    {
	$is_283x = 1;
    }
    else
    {
	print ("* Unknown option '$arg'\n");
	usage();
    }
}

usage() if (@ARGV != 2);

my $kernel_file = $ARGV[0];
my $out_file = $ARGV[1];

if (! -r $kernel_file)
{
    print ("* File '$kernel_file' not found\n");
    usage();
}

my $wanted_strings =
{
	'brcm,bcm2835-mmc' => FLAG_PI,
	'brcm,bcm2835-sdhost' => FLAG_PI,
	'brcm,bcm2835-gpio' => FLAG_PI | FLAG_DTOK,
	'brcm,bcm2708-fb'   => FLAG_PI | FLAG_DTOK | FLAG_270X,
	'brcm,bcm2708-usb'  => FLAG_PI | FLAG_DTOK | FLAG_270X,
	'brcm,bcm2835' => FLAG_PI | FLAG_DTOK | FLAG_283X,
	'brcm,bcm2836' => FLAG_PI | FLAG_DTOK | FLAG_283X,
	'brcm,bcm2837' => FLAG_PI | FLAG_DTOK | FLAG_283X,
	'of_cfs_init' => FLAG_DTOK | FLAG_DDTK,
};

my $res = try_extract($kernel_file, $tmpfile1);
$res ||= try_decompress('\037\213\010', 'xy',    'gunzip', 0,
			$kernel_file, $tmpfile1, $tmpfile2);
$res ||= try_decompress('\3757zXZ\000', 'abcde', 'unxz --single-stream', -1,
			$kernel_file, $tmpfile1, $tmpfile2);
$res ||= try_decompress('BZh',          'xy',    'bunzip2', 0,
			$kernel_file, $tmpfile1, $tmpfile2);
$res ||= try_decompress('\135\0\0\0',   'xxx',   'unlzma', 0,
			$kernel_file, $tmpfile1, $tmpfile2);
$res ||= try_decompress('\211\114\132', 'xy',    'lzop -d', 0,
			$kernel_file, $tmpfile1, $tmpfile2);
$res ||= try_decompress('\002\041\114\030', 'xy',    'lz4 -d', 1,
			$kernel_file, $tmpfile1, $tmpfile2);

my $append_trailer;
my $trailer;
my $kver = '?';

$append_trailer = 1;

if ($res)
{
    $kver = $res->{'kver'} || '?';
    my $flags = $res->{'flags'};
    print("Version: $kver\n");

    if ($flags & FLAG_PI)
    {
	$dtok ||= ($flags & FLAG_DTOK) != 0;
	$is_270x ||= ($flags & FLAG_270X) != 0;
	$is_283x ||= ($flags & FLAG_283X) != 0;
	$ddtk ||= ($flags & FLAG_DDTK) != 0;
    }
    else
    {
	print ("* This doesn't look like a Raspberry Pi kernel.\n");
    }
}
elsif (!$dtok)
{
    print ("* Is this a valid kernel?\n");
}

if ($append_trailer)
{
    printf("DT: %s\n", $dtok ? "y" : "n");
    printf("DDT: %s\n", $ddtk ? "y" : "n");
    printf("270x: %s\n", $is_270x ? "y" : "n");
    printf("283x: %s\n", $is_283x ? "y" : "n");

    my @atoms;

    push @atoms, [ $trailer_magic, pack('V', 0) ];
    push @atoms, [ 'KVer', $kver ];
    push @atoms, [ 'DTOK', pack('V', $dtok) ];
    push @atoms, [ 'DDTK', pack('V', $ddtk) ];
    push @atoms, [ '270X', pack('V', $is_270x) ];
    push @atoms, [ '283X', pack('V', $is_283x) ];
    push @atoms, [ '283x', pack('V', $is_283x && !$is_270x) ];

    $trailer = pack_trailer(\@atoms);
    $atoms[0]->[1] = pack('V', length($trailer));

    $trailer = pack_trailer(\@atoms);
}

my $ofh;
my $total_len = 0;

if ($out_file eq $kernel_file)
{
    die "* Failed to open '$out_file' for append\n"
	if (!open($ofh, '>>', $out_file));
    $total_len = tell($ofh);
}
else
{
    die "* Failed to open '$kernel_file'\n"
	if (!open(my $ifh, '<', $kernel_file));
    die "* Failed to create '$out_file'\n"
	if (!open($ofh, '>', $out_file));

    my $copybuf;
    while (1)
    {
	my $bytes = sysread($ifh, $copybuf, 64*1024);
	last if (!$bytes);
	syswrite($ofh, $copybuf, $bytes);
	$total_len += $bytes;
    }
    close($ifh);
}

if ($trailer)
{
    # Pad to word-alignment
    syswrite($ofh, "\x000\x000\x000", (-$total_len & 0x3));
    syswrite($ofh, $trailer);
}

close($ofh);

exit($trailer ? 0 : 1);

END {
	unlink($tmpfile1) if ($tmpfile1);
	unlink($tmpfile2) if ($tmpfile2);
}


sub usage
{
	print ("Usage: mkknlimg [--dtok] [--270x] [--283x] <vmlinux|zImage|bzImage> <outfile>\n");
	exit(1);
}

sub try_extract
{
	my ($knl, $tmp) = @_;

	my $ver = `strings "$knl" | grep -a -E "^Linux version [1-9]"`;

	return undef if (!$ver);

	chomp($ver);

	my $res = { 'kver'=>$ver };
	$res->{'flags'} = strings_to_flags($knl, $wanted_strings);

	return $res;
}


sub try_decompress
{
	my ($magic, $subst, $zcat, $idx, $knl, $tmp1, $tmp2) = @_;

	my $pos = `tr "$magic\n$subst" "\n$subst=" < "$knl" | grep -abo "^$subst"`;
	if ($pos)
	{
		chomp($pos);
		$pos = (split(/[\r\n]+/, $pos))[$idx];
		return undef if (!defined($pos));
		$pos =~ s/:.*[\r\n]*$//s;
		my $cmd = "tail -c+$pos \"$knl\" | $zcat > $tmp2 2> /dev/null";
		my $err = (system($cmd) >> 8);
		return undef if (($err != 0) && ($err != 2));

		return try_extract($tmp2, $tmp1);
	}

	return undef;
}

sub strings_to_flags
{
	my ($knl, $strings) = @_;
	my $string_pattern = '^('.join('|', keys(%$strings)).')$';
	my $flags = 0;

	my @matches = `strings \"$knl\" | grep -E \"$string_pattern\"`;
	foreach my $match (@matches)
	{
	    chomp($match);
	    $flags |= $strings->{$match};
	}

	return $flags;
}

sub pack_trailer
{
	my ($atoms) = @_;
	my $trailer = pack('VV', 0, 0);
	for (my $i = $#$atoms; $i>=0; $i--)
	{
		my $atom = $atoms->[$i];
		$trailer .= pack('a*x!4Va4', $atom->[1], length($atom->[1]), $atom->[0]);
	}
	return $trailer;
}