[image] Allow for images to be hidden from lists of all images

When invoking a kernel via the UEFI shim, the kernel (and potentially
also a helper binary such as GRUB) must be accessible via the virtual
filesystem exposed via EFI_SIMPLE_FILE_SYSTEM_PROTOCOL but must not be
present in the magic initrd constructed from all registered images.

Allow for images to be flagged as hidden, which will cause them to be
excluded from API-level lists of all images such as the virtual
filesystem directory contents, the magic initrd, or the Multiboot
module list.  Hidden images remain visible to iPXE commands including
"imgstat", which will show a "[HIDDEN]" flag for such images.

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

5 files changed, 39 insertions, 19 deletions

diff --git a/src/arch/x86/image/bzimage.c b/src/arch/x86/image/bzimage.c
index b15bd5563..2c776147d 100644
--- a/src/arch/x86/image/bzimage.c
+++ b/src/arch/x86/image/bzimage.c
@@ -355,6 +355,10 @@ static size_t bzimage_load_initrd ( struct image *image,
 	size_t offset;
 	size_t pad_len;
 
+	/* Skip hidden images */
+	if ( initrd->flags & IMAGE_HIDDEN )
+		return 0;
+
 	/* Create cpio header for non-prebuilt images */
 	offset = cpio_header ( initrd, &cpio );
 
diff --git a/src/arch/x86/image/multiboot.c b/src/arch/x86/image/multiboot.c
index c1c63bc97..cada021ab 100644
--- a/src/arch/x86/image/multiboot.c
+++ b/src/arch/x86/image/multiboot.c
@@ -204,6 +204,10 @@ static int multiboot_add_modules ( struct image *image, physaddr_t start,
 			break;
 		}
 
+		/* Skip hidden images */
+		if ( module_image->flags & IMAGE_HIDDEN )
+			continue;
+
 		/* Page-align the module */
 		start = ( ( start + 0xfff ) & ~0xfff );
 
diff --git a/src/include/ipxe/image.h b/src/include/ipxe/image.h
index 9e0c0f22a..e00af82ef 100644
--- a/src/include/ipxe/image.h
+++ b/src/include/ipxe/image.h
@@ -72,6 +72,9 @@ struct image {
 /** Image will be automatically unregistered after execution */
 #define IMAGE_AUTO_UNREGISTER 0x0008
 
+/** Image will be hidden from enumeration */
+#define IMAGE_HIDDEN 0x0010
+
 /** An executable image type */
 struct image_type {
 	/** Name of this image type */
@@ -162,15 +165,6 @@ extern struct image *current_image;
 	list_for_each_entry_safe ( (image), (tmp), &images, list )
 
 /**
- * Test for existence of images
- *
- * @ret existence	Some images exist
- */
-static inline int have_images ( void ) {
-	return ( ! list_empty ( &images ) );
-}
-
-/**
  * Retrieve first image
  *
  * @ret image		Image, or NULL
diff --git a/src/interface/efi/efi_file.c b/src/interface/efi/efi_file.c
index fd0bcc6ce..673f902d5 100644
--- a/src/interface/efi/efi_file.c
+++ b/src/interface/efi/efi_file.c
@@ -250,6 +250,10 @@ static size_t efi_file_read_initrd ( struct efi_file_reader *reader ) {
 	len = 0;
 	for_each_image ( image ) {
 
+		/* Skip hidden images */
+		if ( image->flags & IMAGE_HIDDEN )
+			continue;
+
 		/* Pad to alignment boundary */
 		pad_len = ( ( -reader->pos ) & ( INITRD_ALIGN - 1 ) );
 		if ( pad_len ) {
@@ -524,13 +528,21 @@ static EFI_STATUS efi_file_read_dir ( struct efi_file *file, UINTN *len,
 	/* Construct directory entries for image-backed files */
 	index = file->pos;
 	for_each_image ( image ) {
-		if ( index-- == 0 ) {
-			efi_file_image ( &entry, image );
-			efirc = efi_file_info ( &entry, len, data );
-			if ( efirc == 0 )
-				file->pos++;
-			return efirc;
-		}
+
+		/* Skip hidden images */
+		if ( image->flags & IMAGE_HIDDEN )
+			continue;
+
+		/* Skip preceding images */
+		if ( index-- )
+			continue;
+
+		/* Construct directory entry */
+		efi_file_image ( &entry, image );
+		efirc = efi_file_info ( &entry, len, data );
+		if ( efirc == 0 )
+			file->pos++;
+		return efirc;
 	}
 
 	/* No more entries */
@@ -1093,6 +1105,7 @@ int efi_file_install ( EFI_HANDLE handle ) {
 		EFI_DISK_IO_PROTOCOL *diskio;
 		void *interface;
 	} diskio;
+	struct image *image;
 	EFI_STATUS efirc;
 	int rc;
 
@@ -1156,9 +1169,12 @@ int efi_file_install ( EFI_HANDLE handle ) {
 		goto err_initrd_claim;
 
 	/* Install Linux initrd fixed device path file if non-empty */
-	if ( have_images() &&
-	     ( ( rc = efi_file_path_install ( &efi_file_initrd ) ) != 0 ) ) {
-		goto err_initrd_install;
+	for_each_image ( image ) {
+		if ( image->flags & IMAGE_HIDDEN )
+			continue;
+		if ( ( rc = efi_file_path_install ( &efi_file_initrd ) ) != 0 )
+			goto err_initrd_install;
+		break;
 	}
 
 	return 0;
diff --git a/src/usr/imgmgmt.c b/src/usr/imgmgmt.c
index b7fc8293d..94f3d2ce0 100644
--- a/src/usr/imgmgmt.c
+++ b/src/usr/imgmgmt.c
@@ -165,6 +165,8 @@ void imgstat ( struct image *image ) {
 		printf ( " [SELECTED]" );
 	if ( image->flags & IMAGE_AUTO_UNREGISTER )
 		printf ( " [AUTOFREE]" );
+	if ( image->flags & IMAGE_HIDDEN )
+		printf ( " [HIDDEN]" );
 	if ( image->cmdline )
 		printf ( " \"%s\"", image->cmdline );
 	printf ( "\n" );