[romprefix] Report a pessimistic runtime size estimate

PCI3.0 allows us to report a "runtime size" which can be smaller than
the actual ROM size.  On systems that support PMM our runtime size
will be small (~2.5kB), which helps to conserve the limited option ROM
space.  However, there is no guarantee that the PMM allocation will
succeed, and so we need to report the worst-case runtime size in the
PCI header.

Move the "shrunk ROM size" field from the PCI header to a new "iPXE
ROM header", allowing it to be accessed by ROM-manipulation utilities
such as disrom.pl.

Reported-by: Anton D. Kachalov <mouse@yandex-team.ru>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/i386/prefix/romprefix.S

 	jmp	init			/* Initialisation vector */
 checksum:
 	.byte	0
+	.org	0x10
+	.word	ipxeheader
 	.org	0x16
 	.word	undiheader
 	.org	0x18
 	.long	0
 	.previous
 
-build_id:
-	.long	_build_id		/* Randomly-generated build ID */
-
 pciheader:
 	.ascii	"PCIR"			/* Signature */
 	.word	pci_vendor_id		/* Vendor identification */ 
 	.long	pciheader_image_length
 	.long	512
 	.long	0
-	.ascii	"ADHW"
+	.ascii	ZINFO_TYPE_ADxW
 	.long	pciheader_runtime_length
 	.long	512
 	.long	0
 	.equ undiheader_len, . - undiheader
 	.size undiheader, . - undiheader
 
+ipxeheader:
+	.ascii	"iPXE"			/* Signature */
+	.byte	ipxeheader_len		/* Length of structure */
+	.byte	0			/* Checksum */
+shrunk_rom_size:
+	.byte	0			/* Shrunk size (in 512-byte blocks) */
+	.byte	0			/* Reserved */
+build_id:
+	.long	_build_id		/* Randomly-generated build ID */
+	.equ ipxeheader_len, . - ipxeheader
+	.size ipxeheader, . - ipxeheader
+
+	.section ".zinfo.fixup", "a", @progbits	/* Compressor fixups */
+	.ascii	"ADHB"
+	.long	shrunk_rom_size
+	.long	512
+	.long	0
+	.previous
+
 /* Initialisation (called once during POST)
  *
  * Determine whether or not this is a PnP system via a signature
 	addr32 rep movsl	/* PMM presence implies flat real mode */
 	popw	%es
 	/* Shrink ROM */
-	movw	pciheader_runtime_length, %ax
+	movb	shrunk_rom_size, %al
 	movb	%al, romheader_size
 1:	/* Allocate decompression PMM block.  Round up the size to the
 	 * nearest 128kB and use the size within the PMM handle; this

src/util/Option/ROM.pm

 use constant PCI_SIGNATURE => 'PCIR';
 use constant PCI_LAST_IMAGE => 0x80;
 use constant PNP_SIGNATURE => '$PnP';
+use constant IPXE_SIGNATURE => 'iPXE';
 
 our @EXPORT_OK = qw ( ROM_SIGNATURE PCI_SIGNATURE PCI_LAST_IMAGE
-		      PNP_SIGNATURE );
+		      PNP_SIGNATURE IPXE_SIGNATURE );
 our %EXPORT_TAGS = ( all => [ @EXPORT_OK ] );
 
 use constant JMP_SHORT => 0xeb;
       init =>		{ offset => 0x03, length => 0x03,
 			  pack => \&pack_init, unpack => \&unpack_init },
       checksum =>	{ offset => 0x06, length => 0x01, pack => "C" },
+      ipxe_header =>	{ offset => 0x10, length => 0x02, pack => "S" },
       bofm_header =>	{ offset => 0x14, length => 0x02, pack => "S" },
       undi_header =>	{ offset => 0x16, length => 0x02, pack => "S" },
       pci_header =>	{ offset => 0x18, length => 0x02, pack => "S" },
 
 =pod
 
+=item C<< ipxe_header () >>
+
+Return a C<Option::ROM::iPXE> object representing the ROM's iPXE
+header, if present.
+
+=cut
+
+sub ipxe_header {
+  my $hash = shift;
+  my $self = tied(%$hash);
+
+  my $offset = $hash->{ipxe_header};
+  return undef unless $offset != 0;
+
+  return Option::ROM::iPXE->new ( $self->{data}, $offset );
+}
+
+=pod
+
 =item C<< next_image () >>
 
 Return a C<Option::ROM> object representing the next image within the
   return unpack ( "Z*", $raw );
 }
 
+##############################################################################
+#
+# Option::ROM::iPXE
+#
+##############################################################################
+
+package Option::ROM::iPXE;
+
+use strict;
+use warnings;
+use Carp;
+use bytes;
+
+sub new {
+  my $class = shift;
+  my $data = shift;
+  my $offset = shift;
+
+  my $hash = {};
+  tie %$hash, "Option::ROM::Fields", {
+    data => $data,
+    offset => $offset,
+    length => 0x06,
+    fields => {
+      signature =>	{ offset => 0x00, length => 0x04, pack => "a4" },
+      struct_length =>	{ offset => 0x04, length => 0x01, pack => "C" },
+      checksum =>	{ offset => 0x05, length => 0x01, pack => "C" },
+      shrunk_length =>	{ offset => 0x06, length => 0x01, pack => "C" },
+      build_id =>	{ offset => 0x08, length => 0x04, pack => "L" },
+    },
+  };
+  bless $hash, $class;
+
+  # Retrieve true length of structure
+  my $self = tied ( %$hash );
+  $self->{length} = $hash->{struct_length};
+
+  return $hash;
+}
+
+sub checksum {
+  my $hash = shift;
+  my $self = tied(%$hash);
+
+  return $self->checksum();
+}
+
+sub fix_checksum {
+  my $hash = shift;
+  my $self = tied(%$hash);
+
+  $hash->{checksum} = ( ( $hash->{checksum} - $hash->checksum() ) & 0xff );
+}
+
 1;

src/util/disrom.pl

     printf "\n";
   }
 
+  my $ipxe = $rom->ipxe_header();
+  if ( $ipxe ) {
+    printf "iPXE header:\n\n";
+    printf "  %-16s 0x%02x (%s0x%02x)\n", "Checksum:", $ipxe->{checksum},
+	   ( ( $ipxe->checksum == 0 ) ? "" : "INCORRECT: " ), $ipxe->checksum;
+    printf "  %-16s 0x%02x (%d)\n", "Shrunk length:",
+	   $ipxe->{shrunk_length}, ( $ipxe->{shrunk_length} * 512 );
+    printf "  %-16s 0x%08x\n", "Build ID:", $ipxe->{build_id};
+    printf "\n";
+  }
+
 } while ( $rom = $rom->next_image );

src/util/fixrom.pl

   my $image = $rom;
   while ( $image ) {
     $image->pnp_header->fix_checksum() if $image->pnp_header;
+    $image->ipxe_header->fix_checksum() if $image->ipxe_header;
     $image->fix_checksum();
     $image = $image->next_image();
   }