[efi] Allow for .efidrv images as well as .efi images

Merge in the changes that allow for building EFI driver images (that
can be loaded using the EFI shell's "load" command) as well as EFI
applications.

src/arch/x86/Makefile.efi

@@ -0,0 +1,24 @@
+# -*- makefile -*- : Force emacs to use Makefile mode
+
+# The EFI linker script
+#
+LDSCRIPT	= arch/x86/scripts/efi.lds
+
+# Retain relocation information for elf2efi
+#
+LDFLAGS		+= -q -S
+
+# Media types.
+#
+NON_AUTO_MEDIA	+= efi
+NON_AUTO_MEDIA	+= efidrv
+
+# Rules for building EFI files
+#
+$(BIN)/%.efi : $(BIN)/%.efi.tmp $(ELF2EFI)
+	$(QM)$(ECHO) "  [FINISH] $@"
+	$(Q)$(ELF2EFI) --subsystem=10 $< $@
+
+$(BIN)/%.efidrv : $(BIN)/%.efidrv.tmp $(ELF2EFI)
+	$(QM)$(ECHO) "  [FINISH] $@"
+	$(Q)$(ELF2EFI) --subsystem=11 $< $@

src/arch/x86/prefix/efidrvprefix.c

@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2009 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <stdlib.h>
+#include <gpxe/init.h>
+#include <gpxe/efi/efi.h>
+
+/**
+ * EFI entry point
+ *
+ * @v image_handle	Image handle
+ * @v systab		System table
+ * @ret efirc		EFI return status code
+ */
+EFI_STATUS EFIAPI _start ( EFI_HANDLE image_handle,
+			   EFI_SYSTEM_TABLE *systab ) {
+	EFI_STATUS efirc;
+
+	/* Initialise EFI environment */
+	if ( ( efirc = efi_init ( image_handle, systab ) ) != 0 )
+		return efirc;
+
+	/* Initialise gPXE environment */
+	initialise();
+	startup();
+
+	/* Install SNP driver and return */
+	return RC_TO_EFIRC ( efi_snp_install () );
+}

src/arch/x86/scripts/efi.lds

@@ -5,7 +5,6 @@
  *
  */
 
-EXTERN ( _start )
 ENTRY ( _start )
 
 SECTIONS {