[image] Always unregister currently executing image

We unregister script images during their execution, to prevent a
"boot" command from re-executing the containing script.  This also has
the side effect of preventing executing scripts from showing up within
the Linux magic initrd image (or the Multiboot module list).

Additional logic in bzimage.c and efi_file.c prevents a currently
executing kernel from showing up within the magic initrd image.
Similar logic in multiboot.c prevents the Multiboot kernel from
showing up as a Multiboot module.

This still leaves some corner cases that are not covered correctly.
For example: when using a gzip-compressed kernel image, nothing will
currently hide the original compressed image from the magic initrd.

Fix by moving the logic that temporarily unregisters the current image
from script_exec() to image_exec(), so that it applies to all image
types, and simplify the magic initrd and Multiboot module list
construction logic on the basis that no further filtering of the
registered image list is necessary.

This change has the side effect of hiding currently executing EFI
images from the virtual filesystem exposed by iPXE.  For example, when
using iPXE to boot wimboot, the wimboot binary itself will no longer
be visible within the virtual filesystem.

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

5 files changed, 10 insertions, 29 deletions

diff --git a/src/arch/x86/image/bzimage.c b/src/arch/x86/image/bzimage.c
index b40bb2d0..b15bd556 100644
--- a/src/arch/x86/image/bzimage.c
+++ b/src/arch/x86/image/bzimage.c
@@ -355,10 +355,6 @@ static size_t bzimage_load_initrd ( struct image *image,
 	size_t offset;
 	size_t pad_len;
 
-	/* Do not include kernel image itself as an initrd */
-	if ( initrd == image )
-		return 0;
-
 	/* Create cpio header for non-prebuilt images */
 	offset = cpio_header ( initrd, &cpio );
 
@@ -406,10 +402,6 @@ static int bzimage_check_initrds ( struct image *image,
 	/* Calculate total loaded length of initrds */
 	for_each_image ( initrd ) {
 
-		/* Skip kernel */
-		if ( initrd == image )
-			continue;
-
 		/* Calculate length */
 		len += bzimage_load_initrd ( image, initrd, UNULL );
 		len = bzimage_align ( len );
diff --git a/src/arch/x86/image/multiboot.c b/src/arch/x86/image/multiboot.c
index 0c85df70..c1c63bc9 100644
--- a/src/arch/x86/image/multiboot.c
+++ b/src/arch/x86/image/multiboot.c
@@ -204,10 +204,6 @@ static int multiboot_add_modules ( struct image *image, physaddr_t start,
 			break;
 		}
 
-		/* Do not include kernel image itself as a module */
-		if ( module_image == image )
-			continue;
-
 		/* Page-align the module */
 		start = ( ( start + 0xfff ) & ~0xfff );
 
diff --git a/src/core/image.c b/src/core/image.c
index 5a9aebc7..b280eb4d 100644
--- a/src/core/image.c
+++ b/src/core/image.c
@@ -349,9 +349,8 @@ int image_exec ( struct image *image ) {
 	/* Preserve record of any currently-running image */
 	saved_current_image = current_image;
 
-	/* Take out a temporary reference to the image.  This allows
-	 * the image to unregister itself if necessary, without
-	 * automatically freeing itself.
+	/* Take out a temporary reference to the image, so that it
+	 * does not get freed when temporarily unregistered.
 	 */
 	current_image = image_get ( image );
 
@@ -371,6 +370,9 @@ int image_exec ( struct image *image ) {
 	/* Record boot attempt */
 	syslog ( LOG_NOTICE, "Executing \"%s\"\n", image->name );
 
+	/* Temporarily unregister the image during its execution */
+	unregister_image ( image );
+
 	/* Try executing the image */
 	if ( ( rc = image->type->exec ( image ) ) != 0 ) {
 		DBGC ( image, "IMAGE %s could not execute: %s\n",
@@ -387,6 +389,10 @@ int image_exec ( struct image *image ) {
 			 image->name, strerror ( rc ) );
 	}
 
+	/* Re-register image (unless due to be replaced) */
+	if ( ! image->replacement )
+		register_image ( image );
+
 	/* Pick up replacement image before we drop the original
 	 * image's temporary reference.  The replacement image must
 	 * already be registered, so we don't need to hold a temporary
diff --git a/src/image/script.c b/src/image/script.c
index 28050868..b34df1e2 100644
--- a/src/image/script.c
+++ b/src/image/script.c
@@ -197,11 +197,6 @@ static int script_exec ( struct image *image ) {
 	size_t saved_offset;
 	int rc;
 
-	/* Temporarily de-register image, so that a "boot" command
-	 * doesn't throw us into an execution loop.
-	 */
-	unregister_image ( image );
-
 	/* Preserve state of any currently-running script */
 	saved_offset = script_offset;
 
@@ -212,10 +207,6 @@ static int script_exec ( struct image *image ) {
 	/* Restore saved state */
 	script_offset = saved_offset;
 
-	/* Re-register image (unless we have been replaced) */
-	if ( ! image->replacement )
-		register_image ( image );
-
 	return rc;
 }
 
diff --git a/src/interface/efi/efi_file.c b/src/interface/efi/efi_file.c
index f2b44fa7..a0bba160 100644
--- a/src/interface/efi/efi_file.c
+++ b/src/interface/efi/efi_file.c
@@ -240,10 +240,6 @@ static size_t efi_file_read_initrd ( struct efi_file_reader *reader ) {
 	len = 0;
 	for_each_image ( image ) {
 
-		/* Ignore currently executing image */
-		if ( image == current_image )
-			continue;
-
 		/* Pad to alignment boundary */
 		pad_len = ( ( -reader->pos ) & ( INITRD_ALIGN - 1 ) );
 		if ( pad_len ) {
@@ -1091,7 +1087,7 @@ int efi_file_install ( EFI_HANDLE handle ) {
 	 * instance only if the initrd is non-empty, since Linux does
 	 * not gracefully handle a zero-length initrd.
 	 */
-	load = ( list_is_singular ( &images ) ? NULL : &efi_file_initrd.load );
+	load = ( have_images() ? &efi_file_initrd.load : NULL );
 	if ( ( rc = efi_file_path_install ( &efi_file_initrd_path.vendor.Header,
 					    load ) ) != 0 ) {
 		goto err_initrd;