[ELF] Add ability to boot ELF images generated by wraplinux and mkelfImage

Delete ELF as a generic image type.  The method for invoking an
ELF-based image (as well as any tables that must be set up to allow it
to boot) will always depend on the specific architecture.  core/elf.c
now only provides the elf_load() function, to avoid duplicating
functionality between ELF-based image types.

Add arch/i386/image/elfboot.c, to handle the generic case of 32-bit
x86 ELF images.  We don't currently set up any multiboot tables, ELF
notes, etc.  This seems to be sufficient for loading kernels generated
using both wraplinux and coreboot's mkelfImage.

Note that while Etherboot 5.4 allowed ELF images to return, we don't.
There is no callback mechanism for the loaded image to shut down gPXE,
which means that we have to shut down before invoking the image.  This
means that we lose device state, protection against being trampled on,
etc.  It is not safe to continue afterwards.

1 files changed, 6 insertions, 23 deletions

diff --git a/src/image/elf.c b/src/image/elf.c
index 75c976ea..b932ff58 100644
--- a/src/image/elf.c
+++ b/src/image/elf.c
@@ -21,6 +21,9 @@
  *
  * ELF image format
  *
+ * A "pure" ELF image is not a bootable image.  There are various
+ * bootable formats based upon ELF (e.g. Multiboot), which share
+ * common ELF-related functionality.
  */
 
 #include <errno.h>
@@ -30,23 +33,11 @@
 #include <gpxe/image.h>
 #include <gpxe/elf.h>
 
-struct image_type elf_image_type __image_type ( PROBE_NORMAL );
-
 typedef Elf32_Ehdr	Elf_Ehdr;
 typedef Elf32_Phdr	Elf_Phdr;
 typedef Elf32_Off	Elf_Off;
 
 /**
- * Execute ELF image
- *
- * @v image		ELF file
- * @ret rc		Return status code
- */
-static int elf_exec ( struct image *image __unused ) {
-	return -ENOTSUP;
-}
-
-/**
  * Load ELF segment into memory
  *
  * @v image		ELF file
@@ -112,6 +103,9 @@ int elf_load ( struct image *image ) {
 	unsigned int phnum;
 	int rc;
 
+	/* Image type must already have been set by caller */
+	assert ( image->type != NULL );
+
 	/* Read ELF header */
 	copy_from_user ( &ehdr, image->data, 0, sizeof ( ehdr ) );
 	if ( memcmp ( &ehdr.e_ident[EI_MAG0], ELFMAG, SELFMAG ) != 0 ) {
@@ -119,10 +113,6 @@ int elf_load ( struct image *image ) {
 		return -ENOEXEC;
 	}
 
-	/* This is an ELF image, valid or otherwise */
-	if ( ! image->type )
-		image->type = &elf_image_type;
-
 	/* Read ELF program headers */
 	for ( phoff = ehdr.e_phoff , phnum = ehdr.e_phnum ; phnum ;
 	      phoff += ehdr.e_phentsize, phnum-- ) {
@@ -141,10 +131,3 @@ int elf_load ( struct image *image ) {
 
 	return 0;
 }
-
-/** ELF image type */
-struct image_type elf_image_type __image_type ( PROBE_NORMAL ) = {
-	.name = "ELF",
-	.load = elf_load,
-	.exec = elf_exec,
-};