#!/usr/bin/perl -w

##########################################################################
# RecoverDiskLabel.pl                                                    #
#                                                                        #
# Simple Script which will try and recover disk layout information       #
# in the event of the disk label being lost or accidentally deleted.     #
#                                                                        #
# This will only work for FreeBSD systems, it assumes that the install   #
# is in a single slice rather than indivdual slices per mount point.     #
# and make sure the disk is unmounted while in use (which should already #
# be the case if you are needing this script in the first place)         #
#                                                                        #
# The script will return what it expects the disklabel to look like if   #
# the orginal system was a standard FreeBSD system disk, otherwise use   #
# the information as a starting point                                    #
#                                                    ego@neilstyles.com  #
##########################################################################

# Disk Device you must use the Raw Device e.g. if the the disk 
# shows up up in dmesg as ad0, you would add /dev/rad0s1 below
$disk = "/dev/rad2s1";

# Lets open the Disk up
open DISK,"<$disk"
	or die "Open!";

$bufsize = 65536;

# Keep a 64K rolling window
read (DISK, $data, $bufsize) == $bufsize
	or die "Read!";
$bufptr = 0;
$block = 0;
$partition = 0;

print "#        size   offset    fstype   [fsize bsize bps/cpg]\n";

while (1) {
	if (substr($data,($bufptr+0x215c)%$bufsize, 4) eq "\x54\x19\x01\x00" &&
	    substr($data,($bufptr+0x415c)%$bufsize, 4) eq "\x54\x19\x01\x00") {
		$size = &getint32(substr($data,($bufptr+0x1c24)%$bufsize,4)) * 2;
		$bsize = &getint32(substr($data,($bufptr+0x1c30)%$bufsize,4));
		$fsize = &getint32(substr($data,($bufptr+0x1c34)%$bufsize,4));
		$cpg = &getint32(substr($data,($bufptr+0x1cb4)%$bufsize,4));
		$offset = $block - 2;
		if ($partition == 1) {
			printf "  b: %8d %8d      swap\n", $offset-$watermark, $watermark;
			printf "  c: %8d %8d    unused %8d %5d\n", -1, 0, 0, 0;
			$partition = 4;
		}
		printf "  %c: %8d %8d    4.2BSD %8d %5d %5d\n", $partition+ord('a'), $size, $offset, $fsize, $bsize, $cpg;
		$watermark = $offset+$size;
		$partition++;
	}
	read (DISK, substr($data, $bufptr, 512), 512) == 512
		or last;
	$bufptr = ($bufptr+512) % $bufsize;
	$block++;
}
$totsize = $block+($bufsize/512);
printf "# Replace -1 with %d in partition c\n", $totsize;
if ($totsize & 1) {
	printf "# Add 1 to size of last partition\n";
}

sub getint32() {
	my $val;
	$val = ord(substr($_[0],0,1));
	$val += ord(substr($_[0],1,1)) << 8;
	$val += ord(substr($_[0],2,1)) << 16;
	$val += ord(substr($_[0],3,1)) << 24;
	return $val;
}

print "\nCompleted.. Good Luck!\n";