Merge tag 'backlight-for-linus-4.1' of git://git.kernel.org/pub/scm/linux/kernel...

[firefly-linux-kernel-4.4.55.git] / kernel / livepatch / core.c

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 01ca08804f5115a298cb89940e9da6ac804d00c3..284e2691e38073d52b00d46010e654e6ff7de9bf 100644 (file)
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -89,16 +89,28 @@ static bool klp_is_object_loaded(struct klp_object *obj)
 /* sets obj->mod if object is not vmlinux and module is found */
 static void klp_find_object_module(struct klp_object *obj)
 {
+       struct module *mod;
+
        if (!klp_is_module(obj))
                return;
 
        mutex_lock(&module_mutex);
        /*
-        * We don't need to take a reference on the module here because we have
-        * the klp_mutex, which is also taken by the module notifier.  This
-        * prevents any module from unloading until we release the klp_mutex.
+        * 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.
+        */
+       mod = find_module(obj->name);
+       /*
+        * Do not mess work of the module coming and going notifiers.
+        * Note that the patch might still be needed before the going handler
+        * 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.
         */
-       obj->mod = find_module(obj->name);
+       if (mod && mod->klp_alive)
+               obj->mod = mod;
+
        mutex_unlock(&module_mutex);
 }
 
@@ -323,32 +335,20 @@ unlock:
        rcu_read_unlock();
 }
 
-static int klp_disable_func(struct klp_func *func)
+static void klp_disable_func(struct klp_func *func)
 {
        struct klp_ops *ops;
-       int ret;
 
-       if (WARN_ON(func->state != KLP_ENABLED))
-               return -EINVAL;
-
-       if (WARN_ON(!func->old_addr))
-               return -EINVAL;
+       WARN_ON(func->state != KLP_ENABLED);
+       WARN_ON(!func->old_addr);
 
        ops = klp_find_ops(func->old_addr);
        if (WARN_ON(!ops))
-               return -EINVAL;
+               return;
 
        if (list_is_singular(&ops->func_stack)) {
-               ret = unregister_ftrace_function(&ops->fops);
-               if (ret) {
-                       pr_err("failed to unregister ftrace handler for function '%s' (%d)\n",
-                              func->old_name, ret);
-                       return ret;
-               }
-
-               ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0);
-               if (ret)
-                       pr_warn("function unregister succeeded but failed to clear the filter\n");
+               WARN_ON(unregister_ftrace_function(&ops->fops));
+               WARN_ON(ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0));
 
                list_del_rcu(&func->stack_node);
                list_del(&ops->node);
@@ -358,8 +358,6 @@ static int klp_disable_func(struct klp_func *func)
        }
 
        func->state = KLP_DISABLED;
-
-       return 0;
 }
 
 static int klp_enable_func(struct klp_func *func)
@@ -420,23 +418,15 @@ err:
        return ret;
 }
 
-static int klp_disable_object(struct klp_object *obj)
+static void klp_disable_object(struct klp_object *obj)
 {
        struct klp_func *func;
-       int ret;
-
-       for (func = obj->funcs; func->old_name; func++) {
-               if (func->state != KLP_ENABLED)
-                       continue;
 
-               ret = klp_disable_func(func);
-               if (ret)
-                       return ret;
-       }
+       for (func = obj->funcs; func->old_name; func++)
+               if (func->state == KLP_ENABLED)
+                       klp_disable_func(func);
 
        obj->state = KLP_DISABLED;
-
-       return 0;
 }
 
 static int klp_enable_object(struct klp_object *obj)
@@ -452,22 +442,19 @@ static int klp_enable_object(struct klp_object *obj)
 
        for (func = obj->funcs; func->old_name; func++) {
                ret = klp_enable_func(func);
-               if (ret)
-                       goto unregister;
+               if (ret) {
+                       klp_disable_object(obj);
+                       return ret;
+               }
        }
        obj->state = KLP_ENABLED;
 
        return 0;
-
-unregister:
-       WARN_ON(klp_disable_object(obj));
-       return ret;
 }
 
 static int __klp_disable_patch(struct klp_patch *patch)
 {
        struct klp_object *obj;
-       int ret;
 
        /* enforce stacking: only the last enabled patch can be disabled */
        if (!list_is_last(&patch->list, &klp_patches) &&
@@ -477,12 +464,8 @@ static int __klp_disable_patch(struct klp_patch *patch)
        pr_notice("disabling patch '%s'\n", patch->mod->name);
 
        for (obj = patch->objs; obj->funcs; obj++) {
-               if (obj->state != KLP_ENABLED)
-                       continue;
-
-               ret = klp_disable_object(obj);
-               if (ret)
-                       return ret;
+               if (obj->state == KLP_ENABLED)
+                       klp_disable_object(obj);
        }
 
        patch->state = KLP_DISABLED;
@@ -541,8 +524,6 @@ static int __klp_enable_patch(struct klp_patch *patch)
        pr_notice("enabling patch '%s'\n", patch->mod->name);
 
        for (obj = patch->objs; obj->funcs; obj++) {
-               klp_find_object_module(obj);
-
                if (!klp_is_object_loaded(obj))
                        continue;
 
@@ -767,6 +748,7 @@ static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
                return -EINVAL;
 
        obj->state = KLP_DISABLED;
+       obj->mod = NULL;
 
        klp_find_object_module(obj);
 
@@ -932,7 +914,6 @@ static void klp_module_notify_going(struct klp_patch *patch,
 {
        struct module *pmod = patch->mod;
        struct module *mod = obj->mod;
-       int ret;
 
        if (patch->state == KLP_DISABLED)
                goto disabled;
@@ -940,10 +921,7 @@ static void klp_module_notify_going(struct klp_patch *patch,
        pr_notice("reverting patch '%s' on unloading module '%s'\n",
                  pmod->name, mod->name);
 
-       ret = klp_disable_object(obj);
-       if (ret)
-               pr_warn("failed to revert patch '%s' on module '%s' (%d)\n",
-                       pmod->name, mod->name, ret);
+       klp_disable_object(obj);
 
 disabled:
        klp_free_object_loaded(obj);
@@ -961,6 +939,15 @@ static int klp_module_notify(struct notifier_block *nb, unsigned long action,
 
        mutex_lock(&klp_mutex);
 
+       /*
+        * Each module has to know that the notifier has been called.
+        * We never know what module will get patched by a new patch.
+        */
+       if (action == MODULE_STATE_COMING)
+               mod->klp_alive = true;
+       else /* MODULE_STATE_GOING */
+               mod->klp_alive = false;
+
        list_for_each_entry(patch, &klp_patches, list) {
                for (obj = patch->objs; obj->funcs; obj++) {
                        if (!klp_is_module(obj) || strcmp(obj->name, mod->name))