scripts: Add mkknlimg and knlinfo scripts from tools repo

The Raspberry Pi firmware looks for a trailer on the kernel image to
determine whether it was compiled with Device Tree support enabled.
If the firmware finds a kernel without this trailer, or which has a
trailer indicating that it isn't DT-capable, it disables DT support
and reverts to using ATAGs.

The mkknlimg utility adds that trailer, having first analysed the
image to look for signs of DT support and the kernel version string.

knlinfo displays the contents of the trailer in the given kernel image.

Author: Phil Elwell

scripts/knlinfo

@@ -0,0 +1,167 @@
+#!/usr/bin/env perl
+# ----------------------------------------------------------------------
+# knlinfo by Phil Elwell for Raspberry Pi
+#
+# (c) 2014,2015 Raspberry Pi (Trading) Limited <[email protected]>
+#
+# Licensed under the terms of the GNU General Public License.
+# ----------------------------------------------------------------------
+
+use strict;
+use integer;
+
+use Fcntl ":seek";
+
+my $trailer_magic = 'RPTL';
+
+my %atom_formats =
+(
+    'DTOK' => \&format_bool,
+    'KVer' => \&format_string,
+);
+
+if (@ARGV != 1)
+{
+	print ("Usage: knlinfo <kernel image>\n");
+	exit(1);
+}
+
+my $kernel_file = $ARGV[0];
+
+
+my ($atoms, $pos) = read_trailer($kernel_file);
+
+exit(1) if (!$atoms);
+
+printf("Kernel trailer found at %d/0x%x:\n", $pos, $pos);
+
+foreach my $atom (@$atoms)
+{
+    printf("  %s: %s\n", $atom->[0], format_atom($atom));
+}
+
+exit(0);
+
+sub read_trailer
+{
+	my ($kernel_file) = @_;
+	my $fh;
+
+	if (!open($fh, '<', $kernel_file))
+	{
+		print ("* Failed to open '$kernel_file'\n");
+		return undef;
+	}
+
+	if (!seek($fh, -12, SEEK_END))
+	{
+		print ("* seek error in '$kernel_file'\n");
+		return undef;
+	}
+
+	my $last_bytes;
+	sysread($fh, $last_bytes, 12);
+
+	my ($trailer_len, $data_len, $magic) = unpack('VVa4', $last_bytes);
+
+	if (($magic ne $trailer_magic) || ($data_len != 4))
+	{
+		print ("* no trailer\n");
+		return undef;
+	}
+	if (!seek($fh, -12, SEEK_END))
+	{
+		print ("* seek error in '$kernel_file'\n");
+		return undef;
+	}
+
+	$trailer_len -= 12;
+
+	while ($trailer_len > 0)
+	{
+		if ($trailer_len < 8)
+		{
+			print ("* truncated atom header in trailer\n");
+			return undef;
+		}
+		if (!seek($fh, -8, SEEK_CUR))
+		{
+			print ("* seek error in '$kernel_file'\n");
+			return undef;
+		}
+		$trailer_len -= 8;
+
+		my $atom_hdr;
+		sysread($fh, $atom_hdr, 8);
+		my ($atom_len, $atom_type) = unpack('Va4', $atom_hdr);
+
+		if ($trailer_len < $atom_len)
+		{
+			print ("* truncated atom data in trailer\n");
+			return undef;
+		}
+
+		my $rounded_len = (($atom_len + 3) & ~3);
+		if (!seek($fh, -(8 + $rounded_len), SEEK_CUR))
+		{
+			print ("* seek error in '$kernel_file'\n");
+			return undef;
+		}
+		$trailer_len -= $rounded_len;
+
+		my $atom_data;
+		sysread($fh, $atom_data, $atom_len);
+
+		if (!seek($fh, -$atom_len, SEEK_CUR))
+		{
+			print ("* seek error in '$kernel_file'\n");
+			return undef;
+		}
+
+		push @$atoms, [ $atom_type, $atom_data ];
+	}
+
+ 	if (($$atoms[-1][0] eq "\x00\x00\x00\x00") &&
+	    ($$atoms[-1][1] eq ""))
+	{
+		pop @$atoms;
+	}
+	else
+	{
+		print ("* end marker missing from trailer\n");
+	}
+
+	return ($atoms, tell($fh));
+}
+
+sub format_atom
+{
+    my ($atom) = @_;
+
+    my $format_func = $atom_formats{$atom->[0]} || \&format_hex;
+    return $format_func->($atom->[1]);
+}
+
+sub format_bool
+{
+    my ($data) = @_;
+    return unpack('V', $data) ? 'true' : 'false';
+}
+
+sub format_int
+{
+    my ($data) = @_;
+    return unpack('V', $data);
+}
+
+sub format_string
+{
+    my ($data) = @_;
+    return '"'.$data.'"';
+}
+
+sub format_hex
+{
+    my ($data) = @_;
+    return unpack('H*', $data);
+}