livepatch/core: supprt load and unload hooks

euler inclusion
category: feature
Bugzilla: 5507
CVE: N/A

----------------------------------------

front-tools kpatch-build support load and unload hooks, but the
kernel does not fit this feature. just implement it.
Signed-off-by: NCheng Jian <cj.chengjian@huawei.com>
Reviewed-by: NLi Bin <huawei.libin@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

include/linux/livepatch.h

@@ -90,6 +90,12 @@ struct klp_func {
 
 struct klp_object;
 
+#ifdef CONFIG_LIVEPATCH_WO_FTRACE
+struct klp_hook {
+	void (*hook)(void);
+};
+#endif
+
 /**
  * struct klp_callbacks - pre/post live-(un)patch callback structure
  * @pre_patch:		executed before code patching
@@ -126,6 +132,10 @@ struct klp_object {
 	/* external */
 	const char *name;
 	struct klp_func *funcs;
+#ifdef CONFIG_LIVEPATCH_WO_FTRACE
+	struct klp_hook *hooks_load;
+	struct klp_hook *hooks_unload;
+#endif
 	struct klp_callbacks callbacks;
 
 	/* internal */

kernel/livepatch/core.c

@@ -1056,6 +1056,34 @@ static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
 	return ret;
 }
 
+#ifdef CONFIG_LIVEPATCH_WO_FTRACE
+static inline int klp_load_hook(struct klp_object *obj)
+{
+	struct klp_hook *hook;
+
+	if (!obj->hooks_load)
+		return 0;
+
+	for (hook = obj->hooks_load; hook->hook; hook++)
+		(*hook->hook)();
+
+	return 0;
+}
+
+static inline int klp_unload_hook(struct klp_object *obj)
+{
+	struct klp_hook *hook;
+
+	if (!obj->hooks_unload)
+		return 0;
+
+	for (hook = obj->hooks_unload; hook->hook; hook++)
+		(*hook->hook)();
+
+	return 0;
+}
+#endif
+
 static int klp_init_patch(struct klp_patch *patch)
 {
 	struct klp_object *obj;
@@ -1087,6 +1115,11 @@ static int klp_init_patch(struct klp_patch *patch)
 			goto free;
 	}
 
+#ifdef CONFIG_LIVEPATCH_WO_FTRACE
+	klp_for_each_object(patch, obj)
+		klp_load_hook(obj);
+#endif
+
 	list_add_tail(&patch->list, &klp_patches);
 
 	mutex_unlock(&klp_mutex);
@@ -1115,6 +1148,9 @@ static int klp_init_patch(struct klp_patch *patch)
 int klp_unregister_patch(struct klp_patch *patch)
 {
 	int ret;
+#ifdef CONFIG_LIVEPATCH_WO_FTRACE
+	struct klp_object *obj;
+#endif
 
 	mutex_lock(&klp_mutex);
 
@@ -1130,6 +1166,11 @@ int klp_unregister_patch(struct klp_patch *patch)
 
 	klp_free_patch(patch);
 
+#ifdef CONFIG_LIVEPATCH_WO_FTRACE
+	klp_for_each_object(patch, obj)
+		klp_unload_hook(obj);
+#endif
+
 	mutex_unlock(&klp_mutex);
 
 	kobject_put(&patch->kobj);