livepatch: Change unsigned long old_addr -> void *old_func in struct klp_func

The address of the to be patched function and new function is stored
in struct klp_func as:

	void *new_func;
	unsigned long old_addr;

The different naming scheme and type are derived from the way
the addresses are set. @old_addr is assigned at runtime using
kallsyms-based search. @new_func is statically initialized,
for example:

  static struct klp_func funcs[] = {
	{
		.old_name = "cmdline_proc_show",
		.new_func = livepatch_cmdline_proc_show,
	}, { }
  };

This patch changes unsigned long old_addr -> void *old_func. It removes
some confusion when these address are later used in the code. It is
motivated by a followup patch that adds special NOP struct klp_func
where we want to assign func->new_func = func->old_addr respectively
func->new_func = func->old_func.

This patch does not modify the existing behavior.
Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Acked-by: Alice Ferrazzi <alice.ferrazzi@gmail.com>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

include/linux/livepatch.h

@@ -40,7 +40,7 @@
  * @new_func:	pointer to the patched function code
  * @old_sympos: a hint indicating which symbol position the old function
  *		can be found (optional)
- * @old_addr:	the address of the function being patched
+ * @old_func:	pointer to the function being patched
  * @kobj:	kobject for sysfs resources
  * @stack_node:	list node for klp_ops func_stack list
  * @old_size:	size of the old function
@@ -77,7 +77,7 @@ struct klp_func {
 	unsigned long old_sympos;
 
 	/* internal */
-	unsigned long old_addr;
+	void *old_func;
 	struct kobject kobj;
 	struct list_head stack_node;
 	unsigned long old_size, new_size;

kernel/livepatch/core.c

@@ -648,7 +648,7 @@ static void klp_free_object_loaded(struct klp_object *obj)
 	obj->mod = NULL;
 
 	klp_for_each_func(obj, func)
-		func->old_addr = 0;
+		func->old_func = NULL;
 }
 
 /*
@@ -721,11 +721,11 @@ static int klp_init_object_loaded(struct klp_patch *patch,
 	klp_for_each_func(obj, func) {
 		ret = klp_find_object_symbol(obj->name, func->old_name,
 					     func->old_sympos,
-					     &func->old_addr);
+					     (unsigned long *)&func->old_func);
 		if (ret)
 			return ret;
 
-		ret = kallsyms_lookup_size_offset(func->old_addr,
+		ret = kallsyms_lookup_size_offset((unsigned long)func->old_func,
 						  &func->old_size, NULL);
 		if (!ret) {
 			pr_err("kallsyms size lookup failed for '%s'\n",

kernel/livepatch/patch.c

@@ -34,7 +34,7 @@
 
 static LIST_HEAD(klp_ops);
 
-struct klp_ops *klp_find_ops(unsigned long old_addr)
+struct klp_ops *klp_find_ops(void *old_func)
 {
 	struct klp_ops *ops;
 	struct klp_func *func;
@@ -42,7 +42,7 @@ struct klp_ops *klp_find_ops(unsigned long old_addr)
 	list_for_each_entry(ops, &klp_ops, node) {
 		func = list_first_entry(&ops->func_stack, struct klp_func,
 					stack_node);
-		if (func->old_addr == old_addr)
+		if (func->old_func == old_func)
 			return ops;
 	}
 
@@ -142,17 +142,18 @@ static void klp_unpatch_func(struct klp_func *func)
 
 	if (WARN_ON(!func->patched))
 		return;
-	if (WARN_ON(!func->old_addr))
+	if (WARN_ON(!func->old_func))
 		return;
 
-	ops = klp_find_ops(func->old_addr);
+	ops = klp_find_ops(func->old_func);
 	if (WARN_ON(!ops))
 		return;
 
 	if (list_is_singular(&ops->func_stack)) {
 		unsigned long ftrace_loc;
 
-		ftrace_loc = klp_get_ftrace_location(func->old_addr);
+		ftrace_loc =
+			klp_get_ftrace_location((unsigned long)func->old_func);
 		if (WARN_ON(!ftrace_loc))
 			return;
 
@@ -174,17 +175,18 @@ static int klp_patch_func(struct klp_func *func)
 	struct klp_ops *ops;
 	int ret;
 
-	if (WARN_ON(!func->old_addr))
+	if (WARN_ON(!func->old_func))
 		return -EINVAL;
 
 	if (WARN_ON(func->patched))
 		return -EINVAL;
 
-	ops = klp_find_ops(func->old_addr);
+	ops = klp_find_ops(func->old_func);
 	if (!ops) {
 		unsigned long ftrace_loc;
 
-		ftrace_loc = klp_get_ftrace_location(func->old_addr);
+		ftrace_loc =
+			klp_get_ftrace_location((unsigned long)func->old_func);
 		if (!ftrace_loc) {
 			pr_err("failed to find location for function '%s'\n",
 				func->old_name);

kernel/livepatch/patch.h

@@ -10,7 +10,7 @@
  * struct klp_ops - structure for tracking registered ftrace ops structs
  *
  * A single ftrace_ops is shared between all enabled replacement functions
- * (klp_func structs) which have the same old_addr.  This allows the switch
+ * (klp_func structs) which have the same old_func.  This allows the switch
  * between function versions to happen instantaneously by updating the klp_ops
  * struct's func_stack list.  The winner is the klp_func at the top of the
  * func_stack (front of the list).
@@ -25,7 +25,7 @@ struct klp_ops {
 	struct ftrace_ops fops;
 };
 
-struct klp_ops *klp_find_ops(unsigned long old_addr);
+struct klp_ops *klp_find_ops(void *old_func);
 
 int klp_patch_object(struct klp_object *obj);
 void klp_unpatch_object(struct klp_object *obj);

kernel/livepatch/transition.c

@@ -224,11 +224,11 @@ static int klp_check_stack_func(struct klp_func *func,
 			 * Check for the to-be-patched function
 			 * (the previous func).
 			 */
-			ops = klp_find_ops(func->old_addr);
+			ops = klp_find_ops(func->old_func);
 
 			if (list_is_singular(&ops->func_stack)) {
 				/* original function */
-				func_addr = func->old_addr;
+				func_addr = (unsigned long)func->old_func;
 				func_size = func->old_size;
 			} else {
 				/* previously patched function */