efi/libstub/x86: Make loaded_image protocol handling mixed mode safe

Add the definitions and use the special wrapper so that the loaded_image
UEFI protocol can be safely used from mixed mode.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

drivers/firmware/efi/libstub/efi-stub-helper.c

@@ -171,8 +171,8 @@ char *efi_convert_cmdline(efi_loaded_image_t *image,
 	const u16 *s2;
 	u8 *s1 = NULL;
 	unsigned long cmdline_addr = 0;
-	int load_options_chars = image->load_options_size / 2; /* UTF-16 */
-	const u16 *options = image->load_options;
+	int load_options_chars = efi_table_attr(image, load_options_size) / 2;
+	const u16 *options = efi_table_attr(image, load_options);
 	int options_bytes = 0;  /* UTF-8 bytes */
 	int options_chars = 0;  /* UTF-16 chars */
 	efi_status_t status;

drivers/firmware/efi/libstub/efistub.h

@@ -308,7 +308,8 @@ union efi_graphics_output_protocol {
 	} mixed_mode;
 };
 
-typedef struct {
+typedef union {
+	struct {
 		u32			revision;
 		efi_handle_t		parent_handle;
 		efi_system_table_t	*system_table;
@@ -322,6 +323,22 @@ typedef struct {
 		unsigned int		image_code_type;
 		unsigned int		image_data_type;
 		efi_status_t		(__efiapi *unload)(efi_handle_t image_handle);
+	};
+	struct {
+		u32		revision;
+		u32		parent_handle;
+		u32		system_table;
+		u32		device_handle;
+		u32		file_path;
+		u32		reserved;
+		u32		load_options_size;
+		u32		load_options;
+		u32		image_base;
+		__aligned_u64	image_size;
+		u32		image_code_type;
+		u32		image_data_type;
+		u32		unload;
+	} mixed_mode;
 } efi_loaded_image_t;
 
 typedef struct {

drivers/firmware/efi/libstub/x86-stub.c

@@ -377,7 +377,7 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle,
 		return status;
 	}
 
-	hdr = &((struct boot_params *)image->image_base)->hdr;
+	hdr = &((struct boot_params *)efi_table_attr(image, image_base))->hdr;
 	above4g = hdr->xloadflags & XLF_CAN_BE_LOADED_ABOVE_4G;
 
 	status = efi_allocate_pages(0x4000, (unsigned long *)&boot_params,
@@ -392,7 +392,7 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle,
 	hdr = &boot_params->hdr;
 
 	/* Copy the second sector to boot_params */
-	memcpy(&hdr->jump, image->image_base + 512, 512);
+	memcpy(&hdr->jump, efi_table_attr(image, image_base) + 512, 512);
 
 	/*
 	 * Fill out some of the header fields ourselves because the