#!/usr/bin/perl -w
  #
  use strict;
  use Math::BigInt;
  use Fcntl "SEEK_SET";
  
  die "Format: $0 [-s <systemmap-file>] <vmlinux-file> <keyring-file>
  "
      if ($#ARGV != 1 && $#ARGV != 3 ||
  	$#ARGV == 3 && $ARGV[0] ne "-s");
  
  my $sysmap = "";
  if ($#ARGV == 3) {
      shift;
      $sysmap = $ARGV[0];
      shift;
  }
  
  my $vmlinux = $ARGV[0];
  my $keyring = $ARGV[1];
  
  #
  # Parse the vmlinux section table
  #
  open FD, "objdump -h $vmlinux |" || die $vmlinux;
  my @lines = <FD>;
  close(FD) || die $vmlinux;
  
  my @sections = ();
  
  foreach my $line (@lines) {
      chomp($line);
      if ($line =~ /\s*([0-9]+)\s+(\S+)\s+([0-9a-f]+)\s+([0-9a-f]+)\s+([0-9a-f]+)\s+([0-9a-f]+)\s+2[*][*]([0-9]+)/
  	) {
  	my $seg  = $1;
  	my $name = $2;
  	my $len  = Math::BigInt->new("0x" . $3);
  	my $vma  = Math::BigInt->new("0x" . $4);
  	my $lma  = Math::BigInt->new("0x" . $5);
  	my $foff = Math::BigInt->new("0x" . $6);
  	my $align = 2 ** $7;
  
  	push @sections, { name => $name,
  			  vma => $vma,
  			  len => $len,
  			  foff => $foff };
      }
  }
  
  print "Have $#sections sections
  ";
  
  #
  # Try and parse the vmlinux symbol table.  If the vmlinux file has been created
  # from a vmlinuz file with extract-vmlinux then the symbol table will be empty.
  #
  open FD, "nm $vmlinux 2>/dev/null |" || die $vmlinux;
  @lines = <FD>;
  close(FD) || die $vmlinux;
  
  my %symbols = ();
  my $nr_symbols = 0;
  
  sub parse_symbols(@) {
      foreach my $line (@_) {
  	chomp($line);
  	if ($line =~ /([0-9a-f]+)\s([a-zA-Z])\s(\S+)/
  	    ) {
  	    my $addr = "0x" . $1;
  	    my $type = $2;
  	    my $name = $3;
  
  	    $symbols{$name} = $addr;
  	    $nr_symbols++;
  	}
      }
  }
  parse_symbols(@lines);
  
  if ($nr_symbols == 0 && $sysmap ne "") {
      print "No symbols in vmlinux, trying $sysmap
  ";
  
      open FD, "<$sysmap" || die $sysmap;
      @lines = <FD>;
      close(FD) || die $sysmap;
      parse_symbols(@lines);
  }
  
  die "No symbols available
  "
      if ($nr_symbols == 0);
  
  print "Have $nr_symbols symbols
  ";
  
  die "Can't find system certificate list"
      unless (exists($symbols{"__cert_list_start"}) &&

  	    exists($symbols{"system_certificate_list_size"}));

  
  my $start = Math::BigInt->new($symbols{"__cert_list_start"});

  my $end;
  my $size;
  my $size_sym = Math::BigInt->new($symbols{"system_certificate_list_size"});

  open FD, "<$vmlinux" || die $vmlinux;
  binmode(FD);

  
  my $s = undef;
  foreach my $sec (@sections) {
      my $s_name = $sec->{name};
      my $s_vma = $sec->{vma};
      my $s_len = $sec->{len};
      my $s_foff = $sec->{foff};
      my $s_vend = $s_vma + $s_len;
  
      next unless ($start >= $s_vma);
      next if ($start >= $s_vend);

      die "Certificate list size was not found on the same section
  "
  	if ($size_sym < $s_vma || $size_sym > $s_vend);

  
      die "Cert object in multiple sections: ", $s_name, " and ", $s->{name}, "
  "
  	if ($s);

  
      my $size_off = $size_sym -$s_vma + $s_foff;
      my $packed;
      die $vmlinux if (!defined(sysseek(FD, $size_off, SEEK_SET)));
      sysread(FD, $packed, 8);
      $size = unpack 'L!', $packed;
      $end = $start + $size;
  
      printf "Have %u bytes of certs at VMA 0x%x
  ", $size, $start;
  
      die "Cert object partially overflows section $s_name
  "
  	if ($end > $s_vend);

      $s = $sec;
  }
  
  die "Cert object not inside a section
  "
      unless ($s);
  
  print "Certificate list in section ", $s->{name}, "
  ";
  
  my $foff = $start - $s->{vma} + $s->{foff};
  
  printf "Certificate list at file offset 0x%x
  ", $foff;

  die $vmlinux if (!defined(sysseek(FD, $foff, SEEK_SET)));
  my $buf = "";
  my $len = sysread(FD, $buf, $size);
  die "$vmlinux" if (!defined($len));
  die "Short read on $vmlinux
  " if ($len != $size);
  close(FD) || die $vmlinux;
  
  open FD, ">$keyring" || die $keyring;
  binmode(FD);
  $len = syswrite(FD, $buf, $size);
  die "$keyring" if (!defined($len));
  die "Short write on $keyring
  " if ($len != $size);
  close(FD) || die $keyring;