[util] Add support for EFI ROM images

The Option::ROM module recognizes and checks EFI header of image.  The
disrom.pl utility dumps this header if is present.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/util/Option/ROM.pm

 use constant PNP_SIGNATURE => '$PnP';
 use constant UNDI_SIGNATURE => 'UNDI';
 use constant IPXE_SIGNATURE => 'iPXE';
+use constant EFI_SIGNATURE => 0x00000ef1;
 
 our @EXPORT_OK = qw ( ROM_SIGNATURE PCI_SIGNATURE PCI_LAST_IMAGE
-		      PNP_SIGNATURE UNDI_SIGNATURE IPXE_SIGNATURE );
+		      PNP_SIGNATURE UNDI_SIGNATURE IPXE_SIGNATURE EFI_SIGNATURE );
 our %EXPORT_TAGS = ( all => [ @EXPORT_OK ] );
 
 use constant JMP_SHORT => 0xeb;
 
 =pod
 
+=item C<< efi_header () >>
+
+Return a C<Option::ROM::EFI> object representing the ROM's EFI header,
+if present.
+
+=cut
+
+sub efi_header {
+  my $hash = shift;
+  my $self = tied(%$hash);
+
+  my $pci = $hash->pci_header ();
+  return undef unless defined $pci;
+
+  return Option::ROM::EFI->new ( $self, $pci );
+}
+
+=pod
+
 =item C<< next_image () >>
 
 Return a C<Option::ROM> object representing the next image within the
   $hash->{checksum} = ( ( $hash->{checksum} - $hash->checksum() ) & 0xff );
 }
 
+##############################################################################
+#
+# Option::ROM::EFI
+#
+##############################################################################
+
+package Option::ROM::EFI;
+
+use strict;
+use warnings;
+use Carp;
+use bytes;
+
+sub new {
+  my $class = shift;
+  my $rom = shift;
+  my $pci = shift;
+
+  my $hash = {};
+  tie %$hash, "Option::ROM::Fields", {
+    rom => $rom,
+    data => $rom->{data},
+    offset => 0x00,
+    length => 0x18,
+    fields => {
+      signature =>		{ offset => 0x00, length => 0x02, pack => "S" },
+      init_size =>		{ offset => 0x02, length => 0x02, pack => "S" },
+      efi_signature =>		{ offset => 0x04, length => 0x04, pack => "L" },
+      efi_subsystem =>		{ offset => 0x08, length => 0x02, pack => "S" },
+      efi_machine_type =>	{ offset => 0x0a, length => 0x02, pack => "S" },
+      compression_type =>	{ offset => 0x0c, length => 0x02, pack => "S" },
+      efi_image_offset =>	{ offset => 0x16, length => 0x02, pack => "S" },
+    },
+  };
+  bless $hash, $class;
+
+  my $self = tied ( %$hash );
+
+  return undef unless ( $hash->{efi_signature} == Option::ROM::EFI_SIGNATURE &&
+			$pci->{code_type} == 0x03 );
+
+  return $hash;
+}
+
 1;

src/util/disrom.pl

   printf "  %-16s 0x%04x\n", "PnP header:", $rom->{pnp_header} if ( exists $rom->{pnp_header} );
   printf "\n";
 
+  my $efi = $rom->efi_header();
+  if ( $efi ) {
+    printf "EFI header:\n\n";
+    printf "  %-16s 0x%04x (%d)\n", "Init size:",
+	   $efi->{init_size}, ( $efi->{init_size} * 512 );
+    printf "  %-16s 0x%08x\n", "EFI Signature:", $efi->{efi_signature};
+    printf "  %-16s 0x%04x\n", "EFI Subsystem:", $efi->{efi_subsystem};
+    printf "  %-16s 0x%04x\n", "EFI Machine type:", $efi->{efi_machine_type};
+    printf "  %-16s 0x%04x\n", "Compression type:", $efi->{compression_type};
+    printf "  %-16s 0x%04x\n", "EFI Image offset:", $efi->{efi_image_offset};
+    printf "\n";
+  }
+
   my $pci = $rom->pci_header();
   if ( $pci ) {
     printf "PCI header:\n\n";