bootm: provide handlers the start of the OS image

The bootm code needs to read the beginning of the OS image in order to
determine the filetype. If it does so already, then we can provide the
handlers the buffer. This can help the handlers to find some image
metadata before loading the full image.

Signed-off-by: Sascha Hauer <[email protected]>

common/bootm.c

@@ -529,6 +529,7 @@ int bootm_boot(struct bootm_data *bootm_data)
 	struct image_handler *handler;
 	int ret;
 	enum filetype os_type;
+	size_t size;
 
 	if (!bootm_data->os_file) {
 		printf("no image given\n");
@@ -548,7 +549,13 @@ int bootm_boot(struct bootm_data *bootm_data)
 	data->os_address = bootm_data->os_address;
 	data->os_entry = bootm_data->os_entry;
 
-	os_type = file_name_detect_type(data->os_file);
+	ret = read_file_2(data->os_file, &size, &data->os_header, PAGE_SIZE);
+	if (ret < 0 && ret != -EFBIG)
+		goto err_out;
+	if (size < PAGE_SIZE)
+		goto err_out;
+
+	os_type = file_detect_type(data->os_header, PAGE_SIZE);
 	if ((int)os_type < 0) {
 		printf("could not open %s: %s\n", data->os_file,
 				strerror(-os_type));
@@ -674,6 +681,7 @@ int bootm_boot(struct bootm_data *bootm_data)
 		of_delete_node(data->of_root_node);
 
 	globalvar_remove("linux.bootargs.bootm.appendroot");
+	free(data->os_header);
 	free(data->os_file);
 	free(data->oftree_file);
 	free(data->initrd_file);

include/bootm.h

@@ -81,6 +81,13 @@ struct image_data {
 	struct fdt_header *oftree;
 	struct resource *oftree_res;
 
+	/*
+	 * The first PAGE_SIZE bytes of the OS image. Can be used by the image
+	 * handlers to analyze the OS image before actually loading the bulk of
+	 * it.
+	 */
+	void *os_header;
+
 	enum bootm_verify verify;
 	int verbose;
 	int force;