livepatch/module: remove livepatch module notifier

Remove the livepatch module notifier in favor of directly enabling and disabling patches to modules in the module loader. Hard-coding the function calls ensures that ftrace_module_enable() is run before klp_module_coming() during module load, and that klp_module_going() is run before ftrace_release_mod() during module unload. This way, ftrace and livepatch code is run in the correct order during the module load/unload sequence without dependence on the module notifier call chain.

Jessica Yu committed 10 years ago

Commit 7e545d61 parent 4c973d13 files · +94 −76Browse files

Showing the changes to kernel/livepatch (1 of 3 files). Show all

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kernel/livepatch/core.c+71−76

 	/*
 	 * We do not want to block removal of patched modules and therefore
 	 * we do not take a reference here. The patches are removed by
-	 * a going module handler instead.
+	 * klp_module_going() instead.
 	 */
 	mod = find_module(obj->name);
 	/*
-	 * Do not mess work of the module coming and going notifiers.
+	 * Do not mess work of klp_module_coming() and klp_module_going().
-	 * Note that the patch might still be needed before the going handler
+	 * Note that the patch might still be needed before klp_module_going()
 	 * is called. Module functions can be called even in the GOING state
 	 * until mod->exit() finishes. This is especially important for
 	 * patches that modify semantic of the functions.
 }
 EXPORT_SYMBOL_GPL(klp_register_patch);
-static int klp_module_notify_coming(struct klp_patch *patch,
+int klp_module_coming(struct module *mod)
-				     struct klp_object *obj)
 {
-	struct module *pmod = patch->mod;
-	struct module *mod = obj->mod;
 	int ret;
+	struct klp_patch *patch;
+	struct klp_object *obj;
-	ret = klp_init_object_loaded(patch, obj);
+	if (WARN_ON(mod->state != MODULE_STATE_COMING))
-	if (ret) {
+		return -EINVAL;
-		pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
-			pmod->name, mod->name, ret);
-		return ret;
-	}
-	if (patch->state == KLP_DISABLED)
+	mutex_lock(&klp_mutex);
-		return 0;
+	/*
+	 * Each module has to know that klp_module_coming()
+	 * has been called. We never know what module will
+	 * get patched by a new patch.
+	 */
+	mod->klp_alive = true;
-	pr_notice("applying patch '%s' to loading module '%s'\n",
+	list_for_each_entry(patch, &klp_patches, list) {
-		  pmod->name, mod->name);
+		klp_for_each_object(patch, obj) {
+			if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
+				continue;
-	ret = klp_enable_object(obj);
+			obj->mod = mod;
-	if (ret)
-		pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
-			pmod->name, mod->name, ret);
-	return ret;
-}
-static void klp_module_notify_going(struct klp_patch *patch,
+			ret = klp_init_object_loaded(patch, obj);
-				    struct klp_object *obj)
+			if (ret) {
-{
+				pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
-	struct module *pmod = patch->mod;
+					patch->mod->name, obj->mod->name, ret);
-	struct module *mod = obj->mod;
+				goto err;
+			}
-	if (patch->state == KLP_DISABLED)
+			if (patch->state == KLP_DISABLED)
-		goto disabled;
+				break;
+			pr_notice("applying patch '%s' to loading module '%s'\n",
+				  patch->mod->name, obj->mod->name);
+			ret = klp_enable_object(obj);
+			if (ret) {
+				pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
+					patch->mod->name, obj->mod->name, ret);
+				goto err;
+			}
+			break;
+		}
+	}
-	pr_notice("reverting patch '%s' on unloading module '%s'\n",
+	mutex_unlock(&klp_mutex);
-		  pmod->name, mod->name);
-	klp_disable_object(obj);
+	return 0;
-disabled:
+err:
+	/*
+	 * If a patch is unsuccessfully applied, return
+	 * error to the module loader.
+	 */
+	pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
+		patch->mod->name, obj->mod->name, obj->mod->name);
+	mod->klp_alive = false;
 	klp_free_object_loaded(obj);
+	mutex_unlock(&klp_mutex);
+	return ret;
 }
-static int klp_module_notify(struct notifier_block *nb, unsigned long action,
+void klp_module_going(struct module *mod)
-			     void *data)
 {
-	int ret;
-	struct module *mod = data;
 	struct klp_patch *patch;
 	struct klp_object *obj;
-	if (action != MODULE_STATE_COMING && action != MODULE_STATE_GOING)
+	if (WARN_ON(mod->state != MODULE_STATE_GOING &&
-		return 0;
+		    mod->state != MODULE_STATE_COMING))
+		return;
 	mutex_lock(&klp_mutex);
 	/*
-	 * Each module has to know that the notifier has been called.
+	 * Each module has to know that klp_module_going()
-	 * We never know what module will get patched by a new patch.
+	 * has been called. We never know what module will
+	 * get patched by a new patch.
 	 */
-	if (action == MODULE_STATE_COMING)
+	mod->klp_alive = false;
-		mod->klp_alive = true;
-	else /* MODULE_STATE_GOING */
-		mod->klp_alive = false;
 	list_for_each_entry(patch, &klp_patches, list) {
 		klp_for_each_object(patch, obj) {
 			if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
 				continue;
-			if (action == MODULE_STATE_COMING) {
+			if (patch->state != KLP_DISABLED) {
-				obj->mod = mod;
+				pr_notice("reverting patch '%s' on unloading module '%s'\n",
-				ret = klp_module_notify_coming(patch, obj);
+					  patch->mod->name, obj->mod->name);
-				if (ret) {
+				klp_disable_object(obj);
-					obj->mod = NULL;
+			}
-					pr_warn("patch '%s' is in an inconsistent state!\n",
-						patch->mod->name);
-				}
-			} else /* MODULE_STATE_GOING */
-				klp_module_notify_going(patch, obj);
+			klp_free_object_loaded(obj);
 			break;
 		}
 	}
 	mutex_unlock(&klp_mutex);
-	return 0;
 }
-static struct notifier_block klp_module_nb = {
-	.notifier_call = klp_module_notify,
-	.priority = INT_MIN+1, /* called late but before ftrace notifier */
-};
 static int __init klp_init(void)
 {
 	int ret;
 		return -EINVAL;
 	}
-	ret = register_module_notifier(&klp_module_nb);
-	if (ret)
-		return ret;
 	klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
-	if (!klp_root_kobj) {
+	if (!klp_root_kobj)
-		ret = -ENOMEM;
+		return -ENOMEM;
-		goto unregister;
-	}
 	return 0;
-unregister:
-	unregister_module_notifier(&klp_module_nb);
-	return ret;
 }
 module_init(klp_init);

livepatch/module: remove livepatch module notifier

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