bootconfig: Add xbc_get_info() for the node information

Add xbc_get_info() API which allows user to get the
number of used xbc_nodes and the size of bootconfig
data. This is also useful for checking the bootconfig
is initialized or not.

Link: https://lkml.kernel.org/r/163177340877.682366.4360676589783197627.stgit@devnote2

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

include/linux/bootconfig.h

@@ -273,6 +273,8 @@ static inline int __init xbc_node_compose_key(struct xbc_node *node,
 /* XBC node initializer */
 int __init xbc_init(const char *buf, size_t size, const char **emsg, int *epos);
 
+/* XBC node and size information */
+int __init xbc_get_info(int *node_size, size_t *data_size);
 
 /* XBC cleanup data structures */
 void __init xbc_destroy_all(void);

init/main.c

@@ -450,6 +450,7 @@ static void __init setup_boot_config(void)
 			pr_err("Failed to parse bootconfig: %s at %d.\n",
 				msg, pos);
 	} else {
+		xbc_get_info(&ret, NULL);
 		pr_info("Load bootconfig: %d bytes %d nodes\n", size, ret);
 		/* keys starting with "kernel." are passed via cmdline */
 		extra_command_line = xbc_make_cmdline("kernel");

lib/bootconfig.c

@@ -34,6 +34,27 @@ static int xbc_err_pos __initdata;
 static int open_brace[XBC_DEPTH_MAX] __initdata;
 static int brace_index __initdata;
 
+/**
+ * xbc_get_info() - Get the information of loaded boot config
+ * node_size: A pointer to store the number of nodes.
+ * data_size: A pointer to store the size of bootconfig data.
+ *
+ * Get the number of used nodes in @node_size if it is not NULL,
+ * and the size of bootconfig data in @data_size if it is not NULL.
+ * Return 0 if the boot config is initialized, or return -ENODEV.
+ */
+int __init xbc_get_info(int *node_size, size_t *data_size)
+{
+	if (!xbc_data)
+		return -ENODEV;
+
+	if (node_size)
+		*node_size = xbc_node_num;
+	if (data_size)
+		*data_size = xbc_data_size;
+	return 0;
+}
+
 static int __init xbc_parse_error(const char *msg, const char *p)
 {
 	xbc_err_msg = msg;

tools/bootconfig/main.c

@@ -391,6 +391,7 @@ static int apply_xbc(const char *path, const char *xbc_path)
 		return ret;
 	}
 	printf("Apply %s to %s\n", xbc_path, path);
+	xbc_get_info(&ret, NULL);
 	printf("\tNumber of nodes: %d\n", ret);
 	printf("\tSize: %u bytes\n", (unsigned int)size);
 	printf("\tChecksum: %d\n", (unsigned int)csum);