Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/livepatching/livepatching

Pull livepatching updates from Jiri Kosina:

 - support for something we call 'atomic replace', and allows for much
   better handling of cumulative patches (which is something very useful
   for distros), from Jason Baron with help of Petr Mladek and Joe
   Lawrence

 - improvement of handling of tasks blocking finalization, from Miroslav
   Benes

 - update of MAINTAINERS file to reflect move towards group
   maintainership

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/livepatching/livepatching: (22 commits)
  livepatch/selftests: use "$@" to preserve argument list
  livepatch: Module coming and going callbacks can proceed with all listed patches
  livepatch: Proper error handling in the shadow variables selftest
  livepatch: return -ENOMEM on ptr_id() allocation failure
  livepatch: Introduce klp_for_each_patch macro
  livepatch: core: Return EOPNOTSUPP instead of ENOSYS
  selftests/livepatch: add DYNAMIC_DEBUG config dependency
  livepatch: samples: non static warnings fix
  livepatch: update MAINTAINERS
  livepatch: Remove signal sysfs attribute
  livepatch: Send a fake signal periodically
  selftests/livepatch: introduce tests
  livepatch: Remove ordering (stacking) of the livepatches
  livepatch: Atomic replace and cumulative patches documentation
  livepatch: Remove Nop structures when unused
  livepatch: Add atomic replace
  livepatch: Use lists to manage patches, objects and functions
  livepatch: Simplify API by removing registration step
  livepatch: Don't block the removal of patches loaded after a forced transition
  livepatch: Consolidate klp_free functions
  ...

6 files changed, 643 insertions, 409 deletions

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 5b77a7314e01..eb0ee10a1981 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -45,7 +45,12 @@
  */
 DEFINE_MUTEX(klp_mutex);
 
-static LIST_HEAD(klp_patches);
+/*
+ * Actively used patches: enabled or in transition. Note that replaced
+ * or disabled patches are not listed even though the related kernel
+ * module still can be loaded.
+ */
+LIST_HEAD(klp_patches);
 
 static struct kobject *klp_root_kobj;
 
@@ -82,20 +87,43 @@ static void klp_find_object_module(struct klp_object *obj)
 	mutex_unlock(&module_mutex);
 }
 
-static bool klp_is_patch_registered(struct klp_patch *patch)
+static bool klp_initialized(void)
+{
+	return !!klp_root_kobj;
+}
+
+static struct klp_func *klp_find_func(struct klp_object *obj,
+				      struct klp_func *old_func)
 {
-	struct klp_patch *mypatch;
+	struct klp_func *func;
 
-	list_for_each_entry(mypatch, &klp_patches, list)
-		if (mypatch == patch)
-			return true;
+	klp_for_each_func(obj, func) {
+		if ((strcmp(old_func->old_name, func->old_name) == 0) &&
+		    (old_func->old_sympos == func->old_sympos)) {
+			return func;
+		}
+	}
 
-	return false;
+	return NULL;
 }
 
-static bool klp_initialized(void)
+static struct klp_object *klp_find_object(struct klp_patch *patch,
+					  struct klp_object *old_obj)
 {
-	return !!klp_root_kobj;
+	struct klp_object *obj;
+
+	klp_for_each_object(patch, obj) {
+		if (klp_is_module(old_obj)) {
+			if (klp_is_module(obj) &&
+			    strcmp(old_obj->name, obj->name) == 0) {
+				return obj;
+			}
+		} else if (!klp_is_module(obj)) {
+			return obj;
+		}
+	}
+
+	return NULL;
 }
 
 struct klp_find_arg {
@@ -278,170 +306,6 @@ static int klp_write_object_relocations(struct module *pmod,
 	return ret;
 }
 
-static int __klp_disable_patch(struct klp_patch *patch)
-{
-	struct klp_object *obj;
-
-	if (WARN_ON(!patch->enabled))
-		return -EINVAL;
-
-	if (klp_transition_patch)
-		return -EBUSY;
-
-	/* enforce stacking: only the last enabled patch can be disabled */
-	if (!list_is_last(&patch->list, &klp_patches) &&
-	    list_next_entry(patch, list)->enabled)
-		return -EBUSY;
-
-	klp_init_transition(patch, KLP_UNPATCHED);
-
-	klp_for_each_object(patch, obj)
-		if (obj->patched)
-			klp_pre_unpatch_callback(obj);
-
-	/*
-	 * Enforce the order of the func->transition writes in
-	 * klp_init_transition() and the TIF_PATCH_PENDING writes in
-	 * klp_start_transition().  In the rare case where klp_ftrace_handler()
-	 * is called shortly after klp_update_patch_state() switches the task,
-	 * this ensures the handler sees that func->transition is set.
-	 */
-	smp_wmb();
-
-	klp_start_transition();
-	klp_try_complete_transition();
-	patch->enabled = false;
-
-	return 0;
-}
-
-/**
- * klp_disable_patch() - disables a registered patch
- * @patch:	The registered, enabled patch to be disabled
- *
- * Unregisters the patched functions from ftrace.
- *
- * Return: 0 on success, otherwise error
- */
-int klp_disable_patch(struct klp_patch *patch)
-{
-	int ret;
-
-	mutex_lock(&klp_mutex);
-
-	if (!klp_is_patch_registered(patch)) {
-		ret = -EINVAL;
-		goto err;
-	}
-
-	if (!patch->enabled) {
-		ret = -EINVAL;
-		goto err;
-	}
-
-	ret = __klp_disable_patch(patch);
-
-err:
-	mutex_unlock(&klp_mutex);
-	return ret;
-}
-EXPORT_SYMBOL_GPL(klp_disable_patch);
-
-static int __klp_enable_patch(struct klp_patch *patch)
-{
-	struct klp_object *obj;
-	int ret;
-
-	if (klp_transition_patch)
-		return -EBUSY;
-
-	if (WARN_ON(patch->enabled))
-		return -EINVAL;
-
-	/* enforce stacking: only the first disabled patch can be enabled */
-	if (patch->list.prev != &klp_patches &&
-	    !list_prev_entry(patch, list)->enabled)
-		return -EBUSY;
-
-	/*
-	 * A reference is taken on the patch module to prevent it from being
-	 * unloaded.
-	 */
-	if (!try_module_get(patch->mod))
-		return -ENODEV;
-
-	pr_notice("enabling patch '%s'\n", patch->mod->name);
-
-	klp_init_transition(patch, KLP_PATCHED);
-
-	/*
-	 * Enforce the order of the func->transition writes in
-	 * klp_init_transition() and the ops->func_stack writes in
-	 * klp_patch_object(), so that klp_ftrace_handler() will see the
-	 * func->transition updates before the handler is registered and the
-	 * new funcs become visible to the handler.
-	 */
-	smp_wmb();
-
-	klp_for_each_object(patch, obj) {
-		if (!klp_is_object_loaded(obj))
-			continue;
-
-		ret = klp_pre_patch_callback(obj);
-		if (ret) {
-			pr_warn("pre-patch callback failed for object '%s'\n",
-				klp_is_module(obj) ? obj->name : "vmlinux");
-			goto err;
-		}
-
-		ret = klp_patch_object(obj);
-		if (ret) {
-			pr_warn("failed to patch object '%s'\n",
-				klp_is_module(obj) ? obj->name : "vmlinux");
-			goto err;
-		}
-	}
-
-	klp_start_transition();
-	klp_try_complete_transition();
-	patch->enabled = true;
-
-	return 0;
-err:
-	pr_warn("failed to enable patch '%s'\n", patch->mod->name);
-
-	klp_cancel_transition();
-	return ret;
-}
-
-/**
- * klp_enable_patch() - enables a registered patch
- * @patch:	The registered, disabled patch to be enabled
- *
- * Performs the needed symbol lookups and code relocations,
- * then registers the patched functions with ftrace.
- *
- * Return: 0 on success, otherwise error
- */
-int klp_enable_patch(struct klp_patch *patch)
-{
-	int ret;
-
-	mutex_lock(&klp_mutex);
-
-	if (!klp_is_patch_registered(patch)) {
-		ret = -EINVAL;
-		goto err;
-	}
-
-	ret = __klp_enable_patch(patch);
-
-err:
-	mutex_unlock(&klp_mutex);
-	return ret;
-}
-EXPORT_SYMBOL_GPL(klp_enable_patch);
-
 /*
  * Sysfs Interface
  *
@@ -449,11 +313,11 @@ EXPORT_SYMBOL_GPL(klp_enable_patch);
  * /sys/kernel/livepatch/<patch>
  * /sys/kernel/livepatch/<patch>/enabled
  * /sys/kernel/livepatch/<patch>/transition
- * /sys/kernel/livepatch/<patch>/signal
  * /sys/kernel/livepatch/<patch>/force
  * /sys/kernel/livepatch/<patch>/<object>
  * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
  */
+static int __klp_disable_patch(struct klp_patch *patch);
 
 static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
 			     const char *buf, size_t count)
@@ -470,40 +334,32 @@ static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
 
 	mutex_lock(&klp_mutex);
 
-	if (!klp_is_patch_registered(patch)) {
-		/*
-		 * Module with the patch could either disappear meanwhile or is
-		 * not properly initialized yet.
-		 */
-		ret = -EINVAL;
-		goto err;
-	}
-
 	if (patch->enabled == enabled) {
 		/* already in requested state */
 		ret = -EINVAL;
-		goto err;
+		goto out;
 	}
 
-	if (patch == klp_transition_patch) {
+	/*
+	 * Allow to reverse a pending transition in both ways. It might be
+	 * necessary to complete the transition without forcing and breaking
+	 * the system integrity.
+	 *
+	 * Do not allow to re-enable a disabled patch.
+	 */
+	if (patch == klp_transition_patch)
 		klp_reverse_transition();
-	} else if (enabled) {
-		ret = __klp_enable_patch(patch);
-		if (ret)
-			goto err;
-	} else {
+	else if (!enabled)
 		ret = __klp_disable_patch(patch);
-		if (ret)
-			goto err;
-	}
+	else
+		ret = -EINVAL;
 
+out:
 	mutex_unlock(&klp_mutex);
 
+	if (ret)
+		return ret;
 	return count;
-
-err:
-	mutex_unlock(&klp_mutex);
-	return ret;
 }
 
 static ssize_t enabled_show(struct kobject *kobj,
@@ -525,35 +381,6 @@ static ssize_t transition_show(struct kobject *kobj,
 			patch == klp_transition_patch);
 }
 
-static ssize_t signal_store(struct kobject *kobj, struct kobj_attribute *attr,
-			    const char *buf, size_t count)
-{
-	struct klp_patch *patch;
-	int ret;
-	bool val;
-
-	ret = kstrtobool(buf, &val);
-	if (ret)
-		return ret;
-
-	if (!val)
-		return count;
-
-	mutex_lock(&klp_mutex);
-
-	patch = container_of(kobj, struct klp_patch, kobj);
-	if (patch != klp_transition_patch) {
-		mutex_unlock(&klp_mutex);
-		return -EINVAL;
-	}
-
-	klp_send_signals();
-
-	mutex_unlock(&klp_mutex);
-
-	return count;
-}
-
 static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
 			   const char *buf, size_t count)
 {
@@ -585,16 +412,129 @@ static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
 
 static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
 static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);
-static struct kobj_attribute signal_kobj_attr = __ATTR_WO(signal);
 static struct kobj_attribute force_kobj_attr = __ATTR_WO(force);
 static struct attribute *klp_patch_attrs[] = {
 	&enabled_kobj_attr.attr,
 	&transition_kobj_attr.attr,
-	&signal_kobj_attr.attr,
 	&force_kobj_attr.attr,
 	NULL
 };
 
+static void klp_free_object_dynamic(struct klp_object *obj)
+{
+	kfree(obj->name);
+	kfree(obj);
+}
+
+static struct klp_object *klp_alloc_object_dynamic(const char *name)
+{
+	struct klp_object *obj;
+
+	obj = kzalloc(sizeof(*obj), GFP_KERNEL);
+	if (!obj)
+		return NULL;
+
+	if (name) {
+		obj->name = kstrdup(name, GFP_KERNEL);
+		if (!obj->name) {
+			kfree(obj);
+			return NULL;
+		}
+	}
+
+	INIT_LIST_HEAD(&obj->func_list);
+	obj->dynamic = true;
+
+	return obj;
+}
+
+static void klp_free_func_nop(struct klp_func *func)
+{
+	kfree(func->old_name);
+	kfree(func);
+}
+
+static struct klp_func *klp_alloc_func_nop(struct klp_func *old_func,
+					   struct klp_object *obj)
+{
+	struct klp_func *func;
+
+	func = kzalloc(sizeof(*func), GFP_KERNEL);
+	if (!func)
+		return NULL;
+
+	if (old_func->old_name) {
+		func->old_name = kstrdup(old_func->old_name, GFP_KERNEL);
+		if (!func->old_name) {
+			kfree(func);
+			return NULL;
+		}
+	}
+
+	/*
+	 * func->new_func is same as func->old_func. These addresses are
+	 * set when the object is loaded, see klp_init_object_loaded().
+	 */
+	func->old_sympos = old_func->old_sympos;
+	func->nop = true;
+
+	return func;
+}
+
+static int klp_add_object_nops(struct klp_patch *patch,
+			       struct klp_object *old_obj)
+{
+	struct klp_object *obj;
+	struct klp_func *func, *old_func;
+
+	obj = klp_find_object(patch, old_obj);
+
+	if (!obj) {
+		obj = klp_alloc_object_dynamic(old_obj->name);
+		if (!obj)
+			return -ENOMEM;
+
+		list_add_tail(&obj->node, &patch->obj_list);
+	}
+
+	klp_for_each_func(old_obj, old_func) {
+		func = klp_find_func(obj, old_func);
+		if (func)
+			continue;
+
+		func = klp_alloc_func_nop(old_func, obj);
+		if (!func)
+			return -ENOMEM;
+
+		list_add_tail(&func->node, &obj->func_list);
+	}
+
+	return 0;
+}
+
+/*
+ * Add 'nop' functions which simply return to the caller to run
+ * the original function. The 'nop' functions are added to a
+ * patch to facilitate a 'replace' mode.
+ */
+static int klp_add_nops(struct klp_patch *patch)
+{
+	struct klp_patch *old_patch;
+	struct klp_object *old_obj;
+
+	klp_for_each_patch(old_patch) {
+		klp_for_each_object(old_patch, old_obj) {
+			int err;
+
+			err = klp_add_object_nops(patch, old_obj);
+			if (err)
+				return err;
+		}
+	}
+
+	return 0;
+}
+
 static void klp_kobj_release_patch(struct kobject *kobj)
 {
 	struct klp_patch *patch;
@@ -611,6 +551,12 @@ static struct kobj_type klp_ktype_patch = {
 
 static void klp_kobj_release_object(struct kobject *kobj)
 {
+	struct klp_object *obj;
+
+	obj = container_of(kobj, struct klp_object, kobj);
+
+	if (obj->dynamic)
+		klp_free_object_dynamic(obj);
 }
 
 static struct kobj_type klp_ktype_object = {
@@ -620,6 +566,12 @@ static struct kobj_type klp_ktype_object = {
 
 static void klp_kobj_release_func(struct kobject *kobj)
 {
+	struct klp_func *func;
+
+	func = container_of(kobj, struct klp_func, kobj);
+
+	if (func->nop)
+		klp_free_func_nop(func);
 }
 
 static struct kobj_type klp_ktype_func = {
@@ -627,17 +579,23 @@ static struct kobj_type klp_ktype_func = {
 	.sysfs_ops = &kobj_sysfs_ops,
 };
 
-/*
- * Free all functions' kobjects in the array up to some limit. When limit is
- * NULL, all kobjects are freed.
- */
-static void klp_free_funcs_limited(struct klp_object *obj,
-				   struct klp_func *limit)
+static void __klp_free_funcs(struct klp_object *obj, bool nops_only)
 {
-	struct klp_func *func;
+	struct klp_func *func, *tmp_func;
+
+	klp_for_each_func_safe(obj, func, tmp_func) {
+		if (nops_only && !func->nop)
+			continue;
+
+		list_del(&func->node);
 
-	for (func = obj->funcs; func->old_name && func != limit; func++)
-		kobject_put(&func->kobj);
+		/* Might be called from klp_init_patch() error path. */
+		if (func->kobj_added) {
+			kobject_put(&func->kobj);
+		} else if (func->nop) {
+			klp_free_func_nop(func);
+		}
+	}
 }
 
 /* Clean up when a patched object is unloaded */
@@ -647,35 +605,111 @@ static void klp_free_object_loaded(struct klp_object *obj)
 
 	obj->mod = NULL;
 
-	klp_for_each_func(obj, func)
-		func->old_addr = 0;
+	klp_for_each_func(obj, func) {
+		func->old_func = NULL;
+
+		if (func->nop)
+			func->new_func = NULL;
+	}
 }
 
-/*
- * Free all objects' kobjects in the array up to some limit. When limit is
- * NULL, all kobjects are freed.
- */
-static void klp_free_objects_limited(struct klp_patch *patch,
-				     struct klp_object *limit)
+static void __klp_free_objects(struct klp_patch *patch, bool nops_only)
 {
-	struct klp_object *obj;
+	struct klp_object *obj, *tmp_obj;
+
+	klp_for_each_object_safe(patch, obj, tmp_obj) {
+		__klp_free_funcs(obj, nops_only);
+
+		if (nops_only && !obj->dynamic)
+			continue;
+
+		list_del(&obj->node);
 
-	for (obj = patch->objs; obj->funcs && obj != limit; obj++) {
-		klp_free_funcs_limited(obj, NULL);
-		kobject_put(&obj->kobj);
+		/* Might be called from klp_init_patch() error path. */
+		if (obj->kobj_added) {
+			kobject_put(&obj->kobj);
+		} else if (obj->dynamic) {
+			klp_free_object_dynamic(obj);
+		}
 	}
 }
 
-static void klp_free_patch(struct klp_patch *patch)
+static void klp_free_objects(struct klp_patch *patch)
+{
+	__klp_free_objects(patch, false);
+}
+
+static void klp_free_objects_dynamic(struct klp_patch *patch)
+{
+	__klp_free_objects(patch, true);
+}
+
+/*
+ * This function implements the free operations that can be called safely
+ * under klp_mutex.
+ *
+ * The operation must be completed by calling klp_free_patch_finish()
+ * outside klp_mutex.
+ */
+void klp_free_patch_start(struct klp_patch *patch)
 {
-	klp_free_objects_limited(patch, NULL);
 	if (!list_empty(&patch->list))
 		list_del(&patch->list);
+
+	klp_free_objects(patch);
+}
+
+/*
+ * This function implements the free part that must be called outside
+ * klp_mutex.
+ *
+ * It must be called after klp_free_patch_start(). And it has to be
+ * the last function accessing the livepatch structures when the patch
+ * gets disabled.
+ */
+static void klp_free_patch_finish(struct klp_patch *patch)
+{
+	/*
+	 * Avoid deadlock with enabled_store() sysfs callback by
+	 * calling this outside klp_mutex. It is safe because
+	 * this is called when the patch gets disabled and it
+	 * cannot get enabled again.
+	 */
+	if (patch->kobj_added) {
+		kobject_put(&patch->kobj);
+		wait_for_completion(&patch->finish);
+	}
+
+	/* Put the module after the last access to struct klp_patch. */
+	if (!patch->forced)
+		module_put(patch->mod);
+}
+
+/*
+ * The livepatch might be freed from sysfs interface created by the patch.
+ * This work allows to wait until the interface is destroyed in a separate
+ * context.
+ */
+static void klp_free_patch_work_fn(struct work_struct *work)
+{
+	struct klp_patch *patch =
+		container_of(work, struct klp_patch, free_work);
+
+	klp_free_patch_finish(patch);
 }
 
 static int klp_init_func(struct klp_object *obj, struct klp_func *func)
 {
-	if (!func->old_name || !func->new_func)
+	int ret;
+
+	if (!func->old_name)
+		return -EINVAL;
+
+	/*
+	 * NOPs get the address later. The patched module must be loaded,
+	 * see klp_init_object_loaded().
+	 */
+	if (!func->new_func && !func->nop)
 		return -EINVAL;
 
 	if (strlen(func->old_name) >= KSYM_NAME_LEN)
@@ -690,9 +724,13 @@ static int klp_init_func(struct klp_object *obj, struct klp_func *func)
 	 * object. If the user selects 0 for old_sympos, then 1 will be used
 	 * since a unique symbol will be the first occurrence.
 	 */
-	return kobject_init_and_add(&func->kobj, &klp_ktype_func,
-				    &obj->kobj, "%s,%lu", func->old_name,
-				    func->old_sympos ? func->old_sympos : 1);
+	ret = kobject_init_and_add(&func->kobj, &klp_ktype_func,
+				   &obj->kobj, "%s,%lu", func->old_name,
+				   func->old_sympos ? func->old_sympos : 1);
+	if (!ret)
+		func->kobj_added = true;
+
+	return ret;
 }
 
 /* Arches may override this to finish any remaining arch-specific tasks */
@@ -721,11 +759,11 @@ 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",
@@ -733,6 +771,9 @@ static int klp_init_object_loaded(struct klp_patch *patch,
 			return -ENOENT;
 		}
 
+		if (func->nop)
+			func->new_func = func->old_func;
+
 		ret = kallsyms_lookup_size_offset((unsigned long)func->new_func,
 						  &func->new_size, NULL);
 		if (!ret) {
@@ -751,9 +792,6 @@ static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
 	int ret;
 	const char *name;
 
-	if (!obj->funcs)
-		return -EINVAL;
-
 	if (klp_is_module(obj) && strlen(obj->name) >= MODULE_NAME_LEN)
 		return -EINVAL;
 
@@ -767,122 +805,191 @@ static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
 				   &patch->kobj, "%s", name);
 	if (ret)
 		return ret;
+	obj->kobj_added = true;
 
 	klp_for_each_func(obj, func) {
 		ret = klp_init_func(obj, func);
 		if (ret)
-			goto free;
+			return ret;
 	}
 
-	if (klp_is_object_loaded(obj)) {
+	if (klp_is_object_loaded(obj))
 		ret = klp_init_object_loaded(patch, obj);
-		if (ret)
-			goto free;
-	}
 
-	return 0;
-
-free:
-	klp_free_funcs_limited(obj, func);
-	kobject_put(&obj->kobj);
 	return ret;
 }
 
-static int klp_init_patch(struct klp_patch *patch)
+static int klp_init_patch_early(struct klp_patch *patch)
 {
 	struct klp_object *obj;
-	int ret;
+	struct klp_func *func;
 
 	if (!patch->objs)
 		return -EINVAL;
 
-	mutex_lock(&klp_mutex);
-
+	INIT_LIST_HEAD(&patch->list);
+	INIT_LIST_HEAD(&patch->obj_list);
+	patch->kobj_added = false;
 	patch->enabled = false;
+	patch->forced = false;
+	INIT_WORK(&patch->free_work, klp_free_patch_work_fn);
 	init_completion(&patch->finish);
 
+	klp_for_each_object_static(patch, obj) {
+		if (!obj->funcs)
+			return -EINVAL;
+
+		INIT_LIST_HEAD(&obj->func_list);
+		obj->kobj_added = false;
+		list_add_tail(&obj->node, &patch->obj_list);
+
+		klp_for_each_func_static(obj, func) {
+			func->kobj_added = false;
+			list_add_tail(&func->node, &obj->func_list);
+		}
+	}
+
+	if (!try_module_get(patch->mod))
+		return -ENODEV;
+
+	return 0;
+}
+
+static int klp_init_patch(struct klp_patch *patch)
+{
+	struct klp_object *obj;
+	int ret;
+
 	ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch,
 				   klp_root_kobj, "%s", patch->mod->name);
-	if (ret) {
-		mutex_unlock(&klp_mutex);
+	if (ret)
 		return ret;
+	patch->kobj_added = true;
+
+	if (patch->replace) {
+		ret = klp_add_nops(patch);
+		if (ret)
+			return ret;
 	}
 
 	klp_for_each_object(patch, obj) {
 		ret = klp_init_object(patch, obj);
 		if (ret)
-			goto free;
+			return ret;
 	}
 
 	list_add_tail(&patch->list, &klp_patches);
 
-	mutex_unlock(&klp_mutex);
-
 	return 0;
+}
 
-free:
-	klp_free_objects_limited(patch, obj);
+static int __klp_disable_patch(struct klp_patch *patch)
+{
+	struct klp_object *obj;
 
-	mutex_unlock(&klp_mutex);
+	if (WARN_ON(!patch->enabled))
+		return -EINVAL;
 
-	kobject_put(&patch->kobj);
-	wait_for_completion(&patch->finish);
+	if (klp_transition_patch)
+		return -EBUSY;
 
-	return ret;
+	klp_init_transition(patch, KLP_UNPATCHED);
+
+	klp_for_each_object(patch, obj)
+		if (obj->patched)
+			klp_pre_unpatch_callback(obj);
+
+	/*
+	 * Enforce the order of the func->transition writes in
+	 * klp_init_transition() and the TIF_PATCH_PENDING writes in
+	 * klp_start_transition().  In the rare case where klp_ftrace_handler()
+	 * is called shortly after klp_update_patch_state() switches the task,
+	 * this ensures the handler sees that func->transition is set.
+	 */
+	smp_wmb();
+
+	klp_start_transition();
+	patch->enabled = false;
+	klp_try_complete_transition();
+
+	return 0;
 }
 
-/**
- * klp_unregister_patch() - unregisters a patch
- * @patch:	Disabled patch to be unregistered
- *
- * Frees the data structures and removes the sysfs interface.
- *
- * Return: 0 on success, otherwise error
- */
-int klp_unregister_patch(struct klp_patch *patch)
+static int __klp_enable_patch(struct klp_patch *patch)
 {
+	struct klp_object *obj;
 	int ret;
 
-	mutex_lock(&klp_mutex);
+	if (klp_transition_patch)
+		return -EBUSY;
 
-	if (!klp_is_patch_registered(patch)) {
-		ret = -EINVAL;
-		goto err;
-	}
+	if (WARN_ON(patch->enabled))
+		return -EINVAL;
 
-	if (patch->enabled) {
-		ret = -EBUSY;
-		goto err;
-	}
+	if (!patch->kobj_added)
+		return -EINVAL;
 
-	klp_free_patch(patch);
+	pr_notice("enabling patch '%s'\n", patch->mod->name);
 
-	mutex_unlock(&klp_mutex);
+	klp_init_transition(patch, KLP_PATCHED);
+
+	/*
+	 * Enforce the order of the func->transition writes in
+	 * klp_init_transition() and the ops->func_stack writes in
+	 * klp_patch_object(), so that klp_ftrace_handler() will see the
+	 * func->transition updates before the handler is registered and the
+	 * new funcs become visible to the handler.
+	 */
+	smp_wmb();
+
+	klp_for_each_object(patch, obj) {
+		if (!klp_is_object_loaded(obj))
+			continue;
+
+		ret = klp_pre_patch_callback(obj);
+		if (ret) {
+			pr_warn("pre-patch callback failed for object '%s'\n",
+				klp_is_module(obj) ? obj->name : "vmlinux");
+			goto err;
+		}
+
+		ret = klp_patch_object(obj);
+		if (ret) {
+			pr_warn("failed to patch object '%s'\n",
+				klp_is_module(obj) ? obj->name : "vmlinux");
+			goto err;
+		}
+	}
 
-	kobject_put(&patch->kobj);
-	wait_for_completion(&patch->finish);
+	klp_start_transition();
+	patch->enabled = true;
+	klp_try_complete_transition();
 
 	return 0;
 err:
-	mutex_unlock(&klp_mutex);
+	pr_warn("failed to enable patch '%s'\n", patch->mod->name);
+
+	klp_cancel_transition();
 	return ret;
 }
-EXPORT_SYMBOL_GPL(klp_unregister_patch);
 
 /**
- * klp_register_patch() - registers a patch
- * @patch:	Patch to be registered
+ * klp_enable_patch() - enable the livepatch
+ * @patch:	patch to be enabled
  *
- * Initializes the data structure associated with the patch and
- * creates the sysfs interface.
+ * Initializes the data structure associated with the patch, creates the sysfs
+ * interface, performs the needed symbol lookups and code relocations,
+ * registers the patched functions with ftrace.
  *
- * There is no need to take the reference on the patch module here. It is done
- * later when the patch is enabled.
+ * This function is supposed to be called from the livepatch module_init()
+ * callback.
  *
  * Return: 0 on success, otherwise error
  */
-int klp_register_patch(struct klp_patch *patch)
+int klp_enable_patch(struct klp_patch *patch)
 {
+	int ret;
+
 	if (!patch || !patch->mod)
 		return -EINVAL;
 
@@ -897,12 +1004,91 @@ int klp_register_patch(struct klp_patch *patch)
 
 	if (!klp_have_reliable_stack()) {
 		pr_err("This architecture doesn't have support for the livepatch consistency model.\n");
-		return -ENOSYS;
+		return -EOPNOTSUPP;
+	}
+
+
+	mutex_lock(&klp_mutex);
+
+	ret = klp_init_patch_early(patch);
+	if (ret) {
+		mutex_unlock(&klp_mutex);
+		return ret;
 	}
 
-	return klp_init_patch(patch);
+	ret = klp_init_patch(patch);
+	if (ret)
+		goto err;
+
+	ret = __klp_enable_patch(patch);
+	if (ret)
+		goto err;
+
+	mutex_unlock(&klp_mutex);
+
+	return 0;
+
+err:
+	klp_free_patch_start(patch);
+
+	mutex_unlock(&klp_mutex);
+
+	klp_free_patch_finish(patch);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(klp_enable_patch);
+
+/*
+ * This function removes replaced patches.
+ *
+ * We could be pretty aggressive here. It is called in the situation where
+ * these structures are no longer accessible. All functions are redirected
+ * by the klp_transition_patch. They use either a new code or they are in
+ * the original code because of the special nop function patches.
+ *
+ * The only exception is when the transition was forced. In this case,
+ * klp_ftrace_handler() might still see the replaced patch on the stack.
+ * Fortunately, it is carefully designed to work with removed functions
+ * thanks to RCU. We only have to keep the patches on the system. Also
+ * this is handled transparently by patch->module_put.
+ */
+void klp_discard_replaced_patches(struct klp_patch *new_patch)
+{
+	struct klp_patch *old_patch, *tmp_patch;
+
+	klp_for_each_patch_safe(old_patch, tmp_patch) {
+		if (old_patch == new_patch)
+			return;
+
+		old_patch->enabled = false;
+		klp_unpatch_objects(old_patch);
+		klp_free_patch_start(old_patch);
+		schedule_work(&old_patch->free_work);
+	}
+}
+
+/*
+ * This function removes the dynamically allocated 'nop' functions.
+ *
+ * We could be pretty aggressive. NOPs do not change the existing
+ * behavior except for adding unnecessary delay by the ftrace handler.
+ *
+ * It is safe even when the transition was forced. The ftrace handler
+ * will see a valid ops->func_stack entry thanks to RCU.
+ *
+ * We could even free the NOPs structures. They must be the last entry
+ * in ops->func_stack. Therefore unregister_ftrace_function() is called.
+ * It does the same as klp_synchronize_transition() to make sure that
+ * nobody is inside the ftrace handler once the operation finishes.
+ *
+ * IMPORTANT: It must be called right after removing the replaced patches!
+ */
+void klp_discard_nops(struct klp_patch *new_patch)
+{
+	klp_unpatch_objects_dynamic(klp_transition_patch);
+	klp_free_objects_dynamic(klp_transition_patch);
 }
-EXPORT_SYMBOL_GPL(klp_register_patch);
 
 /*
  * Remove parts of patches that touch a given kernel module. The list of
@@ -915,7 +1101,7 @@ static void klp_cleanup_module_patches_limited(struct module *mod,
 	struct klp_patch *patch;
 	struct klp_object *obj;
 
-	list_for_each_entry(patch, &klp_patches, list) {
+	klp_for_each_patch(patch) {
 		if (patch == limit)
 			break;
 
@@ -923,21 +1109,14 @@ static void klp_cleanup_module_patches_limited(struct module *mod,
 			if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
 				continue;
 
-			/*
-			 * Only unpatch the module if the patch is enabled or
-			 * is in transition.
-			 */
-			if (patch->enabled || patch == klp_transition_patch) {
+			if (patch != klp_transition_patch)
+				klp_pre_unpatch_callback(obj);
 
-				if (patch != klp_transition_patch)
-					klp_pre_unpatch_callback(obj);
+			pr_notice("reverting patch '%s' on unloading module '%s'\n",
+				  patch->mod->name, obj->mod->name);
+			klp_unpatch_object(obj);
 
-				pr_notice("reverting patch '%s' on unloading module '%s'\n",
-					  patch->mod->name, obj->mod->name);
-				klp_unpatch_object(obj);
-
-				klp_post_unpatch_callback(obj);
-			}
+			klp_post_unpatch_callback(obj);
 
 			klp_free_object_loaded(obj);
 			break;
@@ -962,7 +1141,7 @@ int klp_module_coming(struct module *mod)
 	 */
 	mod->klp_alive = true;
 
-	list_for_each_entry(patch, &klp_patches, list) {
+	klp_for_each_patch(patch) {
 		klp_for_each_object(patch, obj) {
 			if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
 				continue;
@@ -976,13 +1155,6 @@ int klp_module_coming(struct module *mod)
 				goto err;
 			}
 
-			/*
-			 * Only patch the module if the patch is enabled or is
-			 * in transition.
-			 */
-			if (!patch->enabled && patch != klp_transition_patch)
-				break;
-
 			pr_notice("applying patch '%s' to loading module '%s'\n",
 				  patch->mod->name, obj->mod->name);
 
diff --git a/kernel/livepatch/core.h b/kernel/livepatch/core.h
index 48a83d4364cf..ec43a40b853f 100644
--- a/kernel/livepatch/core.h
+++ b/kernel/livepatch/core.h
@@ -5,6 +5,17 @@
 #include <linux/livepatch.h>
 
 extern struct mutex klp_mutex;
+extern struct list_head klp_patches;
+
+#define klp_for_each_patch_safe(patch, tmp_patch)		\
+	list_for_each_entry_safe(patch, tmp_patch, &klp_patches, list)
+
+#define klp_for_each_patch(patch)	\
+	list_for_each_entry(patch, &klp_patches, list)
+
+void klp_free_patch_start(struct klp_patch *patch);
+void klp_discard_replaced_patches(struct klp_patch *new_patch);
+void klp_discard_nops(struct klp_patch *new_patch);
 
 static inline bool klp_is_object_loaded(struct klp_object *obj)
 {
diff --git a/kernel/livepatch/patch.c b/kernel/livepatch/patch.c
index 7702cb4064fc..99cb3ad05eb4 100644
--- a/kernel/livepatch/patch.c
+++ b/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;
 	}
 
@@ -118,7 +118,15 @@ static void notrace klp_ftrace_handler(unsigned long ip,
 		}
 	}
 
+	/*
+	 * NOPs are used to replace existing patches with original code.
+	 * Do nothing! Setting pc would cause an infinite loop.
+	 */
+	if (func->nop)
+		goto unlock;
+
 	klp_arch_set_pc(regs, (unsigned long)func->new_func);
+
 unlock:
 	preempt_enable_notrace();
 }
@@ -142,17 +150,18 @@ 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 +183,18 @@ 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);
@@ -236,15 +246,26 @@ err:
 	return ret;
 }
 
-void klp_unpatch_object(struct klp_object *obj)
+static void __klp_unpatch_object(struct klp_object *obj, bool nops_only)
 {
 	struct klp_func *func;
 
-	klp_for_each_func(obj, func)
+	klp_for_each_func(obj, func) {
+		if (nops_only && !func->nop)
+			continue;
+
 		if (func->patched)
 			klp_unpatch_func(func);
+	}
 
-	obj->patched = false;
+	if (obj->dynamic || !nops_only)
+		obj->patched = false;
+}
+
+
+void klp_unpatch_object(struct klp_object *obj)
+{
+	__klp_unpatch_object(obj, false);
 }
 
 int klp_patch_object(struct klp_object *obj)
@@ -267,11 +288,21 @@ int klp_patch_object(struct klp_object *obj)
 	return 0;
 }
 
-void klp_unpatch_objects(struct klp_patch *patch)
+static void __klp_unpatch_objects(struct klp_patch *patch, bool nops_only)
 {
 	struct klp_object *obj;
 
 	klp_for_each_object(patch, obj)
 		if (obj->patched)
-			klp_unpatch_object(obj);
+			__klp_unpatch_object(obj, nops_only);
+}
+
+void klp_unpatch_objects(struct klp_patch *patch)
+{
+	__klp_unpatch_objects(patch, false);
+}
+
+void klp_unpatch_objects_dynamic(struct klp_patch *patch)
+{
+	__klp_unpatch_objects(patch, true);
 }
diff --git a/kernel/livepatch/patch.h b/kernel/livepatch/patch.h
index e72d8250d04b..d5f2fbe373e0 100644
--- a/kernel/livepatch/patch.h
+++ b/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).
@@ -25,10 +25,11 @@ 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);
 void klp_unpatch_objects(struct klp_patch *patch);
+void klp_unpatch_objects_dynamic(struct klp_patch *patch);
 
 #endif /* _LIVEPATCH_PATCH_H */
diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
index 304d5eb8a98c..9c89ae8b337a 100644
--- a/kernel/livepatch/transition.c
+++ b/kernel/livepatch/transition.c
@@ -29,11 +29,13 @@
 #define MAX_STACK_ENTRIES  100
 #define STACK_ERR_BUF_SIZE 128
 
+#define SIGNALS_TIMEOUT 15
+
 struct klp_patch *klp_transition_patch;
 
 static int klp_target_state = KLP_UNDEFINED;
 
-static bool klp_forced = false;
+static unsigned int klp_signals_cnt;
 
 /*
  * This work can be performed periodically to finish patching or unpatching any
@@ -87,6 +89,11 @@ static void klp_complete_transition(void)
 		 klp_transition_patch->mod->name,
 		 klp_target_state == KLP_PATCHED ? "patching" : "unpatching");
 
+	if (klp_transition_patch->replace && klp_target_state == KLP_PATCHED) {
+		klp_discard_replaced_patches(klp_transition_patch);
+		klp_discard_nops(klp_transition_patch);
+	}
+
 	if (klp_target_state == KLP_UNPATCHED) {
 		/*
 		 * All tasks have transitioned to KLP_UNPATCHED so we can now
@@ -136,13 +143,6 @@ static void klp_complete_transition(void)
 	pr_notice("'%s': %s complete\n", klp_transition_patch->mod->name,
 		  klp_target_state == KLP_PATCHED ? "patching" : "unpatching");
 
-	/*
-	 * klp_forced set implies unbounded increase of module's ref count if
-	 * the module is disabled/enabled in a loop.
-	 */
-	if (!klp_forced && klp_target_state == KLP_UNPATCHED)
-		module_put(klp_transition_patch->mod);
-
 	klp_target_state = KLP_UNDEFINED;
 	klp_transition_patch = NULL;
 }
@@ -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 */
@@ -348,6 +348,47 @@ done:
 }
 
 /*
+ * Sends a fake signal to all non-kthread tasks with TIF_PATCH_PENDING set.
+ * Kthreads with TIF_PATCH_PENDING set are woken up.
+ */
+static void klp_send_signals(void)
+{
+	struct task_struct *g, *task;
+
+	if (klp_signals_cnt == SIGNALS_TIMEOUT)
+		pr_notice("signaling remaining tasks\n");
+
+	read_lock(&tasklist_lock);
+	for_each_process_thread(g, task) {
+		if (!klp_patch_pending(task))
+			continue;
+
+		/*
+		 * There is a small race here. We could see TIF_PATCH_PENDING
+		 * set and decide to wake up a kthread or send a fake signal.
+		 * Meanwhile the task could migrate itself and the action
+		 * would be meaningless. It is not serious though.
+		 */
+		if (task->flags & PF_KTHREAD) {
+			/*
+			 * Wake up a kthread which sleeps interruptedly and
+			 * still has not been migrated.
+			 */
+			wake_up_state(task, TASK_INTERRUPTIBLE);
+		} else {
+			/*
+			 * Send fake signal to all non-kthread tasks which are
+			 * still not migrated.
+			 */
+			spin_lock_irq(&task->sighand->siglock);
+			signal_wake_up(task, 0);
+			spin_unlock_irq(&task->sighand->siglock);
+		}
+	}
+	read_unlock(&tasklist_lock);
+}
+
+/*
  * Try to switch all remaining tasks to the target patch state by walking the
  * stacks of sleeping tasks and looking for any to-be-patched or
  * to-be-unpatched functions.  If such functions are found, the task can't be
@@ -359,6 +400,7 @@ void klp_try_complete_transition(void)
 {
 	unsigned int cpu;
 	struct task_struct *g, *task;
+	struct klp_patch *patch;
 	bool complete = true;
 
 	WARN_ON_ONCE(klp_target_state == KLP_UNDEFINED);
@@ -396,6 +438,10 @@ void klp_try_complete_transition(void)
 	put_online_cpus();
 
 	if (!complete) {
+		if (klp_signals_cnt && !(klp_signals_cnt % SIGNALS_TIMEOUT))
+			klp_send_signals();
+		klp_signals_cnt++;
+
 		/*
 		 * Some tasks weren't able to be switched over.  Try again
 		 * later and/or wait for other methods like kernel exit
@@ -407,7 +453,18 @@ void klp_try_complete_transition(void)
 	}
 
 	/* we're done, now cleanup the data structures */
+	patch = klp_transition_patch;
 	klp_complete_transition();
+
+	/*
+	 * It would make more sense to free the patch in
+	 * klp_complete_transition() but it is called also
+	 * from klp_cancel_transition().
+	 */
+	if (!patch->enabled) {
+		klp_free_patch_start(patch);
+		schedule_work(&patch->free_work);
+	}
 }
 
 /*
@@ -446,6 +503,8 @@ void klp_start_transition(void)
 		if (task->patch_state != klp_target_state)
 			set_tsk_thread_flag(task, TIF_PATCH_PENDING);
 	}
+
+	klp_signals_cnt = 0;
 }
 
 /*
@@ -569,47 +628,6 @@ void klp_copy_process(struct task_struct *child)
 }
 
 /*
- * Sends a fake signal to all non-kthread tasks with TIF_PATCH_PENDING set.
- * Kthreads with TIF_PATCH_PENDING set are woken up. Only admin can request this
- * action currently.
- */
-void klp_send_signals(void)
-{
-	struct task_struct *g, *task;
-
-	pr_notice("signaling remaining tasks\n");
-
-	read_lock(&tasklist_lock);
-	for_each_process_thread(g, task) {
-		if (!klp_patch_pending(task))
-			continue;
-
-		/*
-		 * There is a small race here. We could see TIF_PATCH_PENDING
-		 * set and decide to wake up a kthread or send a fake signal.
-		 * Meanwhile the task could migrate itself and the action
-		 * would be meaningless. It is not serious though.
-		 */
-		if (task->flags & PF_KTHREAD) {
-			/*
-			 * Wake up a kthread which sleeps interruptedly and
-			 * still has not been migrated.
-			 */
-			wake_up_state(task, TASK_INTERRUPTIBLE);
-		} else {
-			/*
-			 * Send fake signal to all non-kthread tasks which are
-			 * still not migrated.
-			 */
-			spin_lock_irq(&task->sighand->siglock);
-			signal_wake_up(task, 0);
-			spin_unlock_irq(&task->sighand->siglock);
-		}
-	}
-	read_unlock(&tasklist_lock);
-}
-
-/*
  * Drop TIF_PATCH_PENDING of all tasks on admin's request. This forces an
  * existing transition to finish.
  *
@@ -620,6 +638,7 @@ void klp_send_signals(void)
  */
 void klp_force_transition(void)
 {
+	struct klp_patch *patch;
 	struct task_struct *g, *task;
 	unsigned int cpu;
 
@@ -633,5 +652,6 @@ void klp_force_transition(void)
 	for_each_possible_cpu(cpu)
 		klp_update_patch_state(idle_task(cpu));
 
-	klp_forced = true;
+	klp_for_each_patch(patch)
+		patch->forced = true;
 }
diff --git a/kernel/livepatch/transition.h b/kernel/livepatch/transition.h
index f9d0bc016067..322db16233de 100644
--- a/kernel/livepatch/transition.h
+++ b/kernel/livepatch/transition.h
@@ -11,7 +11,6 @@ void klp_cancel_transition(void);
 void klp_start_transition(void);
 void klp_try_complete_transition(void);
 void klp_reverse_transition(void);
-void klp_send_signals(void);
 void klp_force_transition(void);
 
 #endif /* _LIVEPATCH_TRANSITION_H */