[efi] Allow currently executing image to be opened via virtual filesystem

When invoking a kernel via the UEFI shim, the kernel image must be
accessible via EFI_SIMPLE_FILE_SYSTEM_PROTOCOL but must not be present
in the magic initrd constructed from all registered images.

Re-register a currently executing EFI image and mark it as hidden,
thereby allowing it to be accessed via the virtual filesystem exposed
via EFI_SIMPLE_FILE_SYSTEM_PROTOCOL without appearing in the magic
initrd contents.

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

1 files changed, 10 insertions, 0 deletions

diff --git a/src/image/efi_image.c b/src/image/efi_image.c
index 467fb05a..0be48564 100644
--- a/src/image/efi_image.c
+++ b/src/image/efi_image.c
@@ -141,6 +141,7 @@ static int efi_image_exec ( struct image *image ) {
 	EFI_HANDLE handle;
 	EFI_MEMORY_TYPE type;
 	wchar_t *cmdline;
+	unsigned int toggle;
 	EFI_STATUS efirc;
 	int rc;
 
@@ -153,6 +154,12 @@ static int efi_image_exec ( struct image *image ) {
 		goto err_no_snpdev;
 	}
 
+	/* Re-register as a hidden image to allow for access via file I/O */
+	toggle = ( ~image->flags & IMAGE_HIDDEN );
+	image->flags |= IMAGE_HIDDEN;
+	if ( ( rc = register_image ( image ) ) != 0 )
+		goto err_register_image;
+
 	/* Install file I/O protocols */
 	if ( ( rc = efi_file_install ( snpdev->handle ) ) != 0 ) {
 		DBGC ( image, "EFIIMAGE %s could not install file protocol: "
@@ -296,6 +303,9 @@ static int efi_image_exec ( struct image *image ) {
  err_pxe_install:
 	efi_file_uninstall ( snpdev->handle );
  err_file_install:
+	unregister_image ( image );
+ err_register_image:
+	image->flags ^= toggle;
  err_no_snpdev:
 	return rc;
 }