[image] Allow for zero embedded images

Having a default script containing

  #!gpxe
  autoboot

can cause problems when entering commands to load and start a kernel
manually; the default script image will still be present when the
kernel is started and so will be treated as an initrd.  It is possible
to work around this by typing "imgfree" before any other commands, but
this is counter-intuitive.

Fix by allowing the embedded image list to be empty (in which case we
just call autoboot()), and making this the default.

Reported by alkisg@gmail.com.

src/Makefile.housekeeping

 ASFLAGS		+= $(EXTRA_ASFLAGS)
 LDFLAGS		+= $(EXTRA_LDFLAGS)
 
-# Embedded image(s), or default if not set
-#
-EMBEDDED_IMAGE	= image/default.gpxe
-
 # Inhibit -Werror if NO_WERROR is specified on make command line
 #
 ifneq ($(NO_WERROR),1)

src/core/main.c

 		shell();
 	} else {
 		/* User doesn't want shell; load and execute the first
-		 * image.  If booting fails (i.e. if the image
-		 * returns, or fails to execute), offer a second
-		 * chance to enter the shell for diagnostics.
+		 * image, or autoboot() if we have no images.  If
+		 * booting fails for any reason, offer a second chance
+		 * to enter the shell for diagnostics.
 		 */
-		for_each_image ( image ) {
-			image_exec ( image );
-			break;
+		if ( have_images() ) {
+			for_each_image ( image ) {
+				image_exec ( image );
+				break;
+			}
+		} else {
+			autoboot();
 		}
 
 		if ( shell_banner() )

src/hci/commands/image_cmd.c

 }
 
 /**
- * The "imgauto" command
+ * The "chain" command
  *
  * @v argc		Argument count
  * @v argv		Argument list
  * @ret rc		Exit code
  */
-static int imgauto_exec ( int argc, char **argv) {
+static int chain_exec ( int argc, char **argv) {
 	int rc;
 
 	if ( ( rc = imgfetch_core_exec ( NULL, IMG_EXEC, argc, argv ) ) != 0 )
 		.exec = kernel_exec,
 	},
 	{
-		.name = "imgauto",
-		.exec = imgauto_exec,
+		.name = "chain",
+		.exec = chain_exec,
 	},
 	{
 		.name = "imgload",

src/image/default.gpxe

-#!gpxe
-autoboot

src/image/embedded.c

  *
  * @v refcnt		Reference counter
  */
-static void embedded_image_free ( struct refcnt *refcnt __unused ) {
+static void __attribute__ (( unused ))
+embedded_image_free ( struct refcnt *refcnt __unused ) {
 	/* Do nothing */
 }
 
  * Register all embedded images
  */
 static void embedded_init ( void ) {
-	unsigned int i;
+	int i;
 	struct image *image;
 	void *data;
 	int rc;
 
+	/* Skip if we have no embedded images */
+	if ( ! sizeof ( embedded_images ) )
+		return;
+
 	/* Fix up data pointers and register images */
-	for ( i = 0 ; i < ( sizeof ( embedded_images ) /
-			    sizeof ( embedded_images[0] ) ) ; i++ ) {
+	for ( i = 0 ; i < ( int ) ( sizeof ( embedded_images ) /
+				    sizeof ( embedded_images[0] ) ) ; i++ ) {
 		image = &embedded_images[i];
 
 		/* virt_to_user() cannot be used in a static

src/include/gpxe/image.h

 #define for_each_image( image ) \
 	list_for_each_entry ( (image), &images, list )
 
+/**
+ * Test for existence of images
+ *
+ * @ret existence	Some images exist
+ */
+static inline int have_images ( void ) {
+	return ( ! list_empty ( &images ) );
+}
+
 extern struct image * alloc_image ( void );
 extern int image_set_uri ( struct image *image, struct uri *uri );
 extern int image_set_cmdline ( struct image *image, const char *cmdline );