[efi] Fetch device path for loaded image during initialisation

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

src/include/ipxe/efi/efi.h

 
 extern EFI_HANDLE efi_image_handle;
 extern EFI_LOADED_IMAGE_PROTOCOL *efi_loaded_image;
+extern EFI_DEVICE_PATH_PROTOCOL *efi_loaded_image_path;
 extern EFI_SYSTEM_TABLE *efi_systab;
 
 extern const char * efi_strerror ( EFI_STATUS efirc );

src/interface/efi/efi_init.c

 #include <string.h>
 #include <ipxe/efi/efi.h>
 #include <ipxe/efi/Protocol/LoadedImage.h>
+#include <ipxe/efi/Protocol/DevicePath.h>
 #include <ipxe/uuid.h>
 #include <ipxe/init.h>
 
 /** Loaded image protocol for this image */
 EFI_LOADED_IMAGE_PROTOCOL *efi_loaded_image;
 
+/** Loaded image protocol device path for this image */
+EFI_DEVICE_PATH_PROTOCOL *efi_loaded_image_path;
+
 /** System table passed to entry point */
 EFI_SYSTEM_TABLE *efi_systab;
 
 static EFI_GUID efi_loaded_image_protocol_guid
 	= EFI_LOADED_IMAGE_PROTOCOL_GUID;
 
+/** EFI loaded image device path protocol GUID */
+static EFI_GUID efi_loaded_image_device_path_protocol_guid
+	= EFI_LOADED_IMAGE_DEVICE_PATH_PROTOCOL_GUID;
+
 /** Event used to signal shutdown */
 static EFI_EVENT efi_shutdown_event;
 
 	EFI_BOOT_SERVICES *bs;
 	struct efi_protocol *prot;
 	struct efi_config_table *tab;
-	EFI_STATUS efirc;
 	void *loaded_image;
+	void *loaded_image_path;
+	EFI_STATUS efirc;
 
 	/* Store image handle and system table pointer for future use */
 	efi_image_handle = image_handle;
 		return EFI_NOT_AVAILABLE_YET;
 	}
 	DBGC ( systab, "EFI handle %p systab %p\n", image_handle, systab );
-
 	bs = systab->BootServices;
-	efirc = bs->OpenProtocol ( image_handle,
-				   &efi_loaded_image_protocol_guid,
-				   &loaded_image, image_handle, NULL,
-				   EFI_OPEN_PROTOCOL_GET_PROTOCOL );
-	if ( efirc ) {
-	   DBGC ( systab, "Could not get loaded image protocol" );
-	   return efirc;
-	}
-
-	efi_loaded_image = loaded_image;
-	DBG ( "Image base address = %p\n", efi_loaded_image->ImageBase );
 
 	/* Look up used protocols */
 	for_each_table_entry ( prot, EFI_PROTOCOLS ) {
 		}
 	}
 
+	/* Get loaded image protocol */
+	if ( ( efirc = bs->OpenProtocol ( image_handle,
+				&efi_loaded_image_protocol_guid,
+				&loaded_image, image_handle, NULL,
+				EFI_OPEN_PROTOCOL_GET_PROTOCOL ) ) != 0 ) {
+		DBGC ( systab, "EFI could not get loaded image protocol: %s",
+		       efi_strerror ( efirc ) );
+		return efirc;
+	}
+	efi_loaded_image = loaded_image;
+	DBGC ( systab, "EFI image base address %p\n",
+	       efi_loaded_image->ImageBase );
+
+	/* Get loaded image device path protocol */
+	if ( ( efirc = bs->OpenProtocol ( image_handle,
+				&efi_loaded_image_device_path_protocol_guid,
+				&loaded_image_path, image_handle, NULL,
+				EFI_OPEN_PROTOCOL_GET_PROTOCOL ) ) != 0 ) {
+		DBGC ( systab, "EFI could not get loaded image device path "
+		       "protocol: %s", efi_strerror ( efirc ) );
+		return efirc;
+	}
+	efi_loaded_image_path = loaded_image_path;
+	DBGC ( systab, "EFI image device path " );
+	DBGC_EFI_DEVPATH ( systab, efi_loaded_image_path );
+	DBGC ( systab, "\n" );
+
 	/* EFI is perfectly capable of gracefully shutting down any
 	 * loaded devices if it decides to fall back to a legacy boot.
 	 * For no particularly comprehensible reason, it doesn't