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Date: Thu, 10 Mar 2016 16:45:08 -0600
From: Josh Poimboeuf <jpoimboe@...hat.com>
To: Jessica Yu <jeyu@...hat.com>
Cc: Seth Jennings <sjenning@...hat.com>,
Jiri Kosina <jikos@...nel.org>,
Vojtech Pavlik <vojtech@...e.com>,
Miroslav Benes <mbenes@...e.cz>,
Petr Mladek <pmladek@...e.com>,
Rusty Russell <rusty@...tcorp.com.au>,
Steven Rostedt <rostedt@...dmis.org>,
live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] livepatch/module: remove livepatch module notifier
On Wed, Mar 09, 2016 at 05:13:57PM -0500, Jessica Yu wrote:
> 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.
>
> Signed-off-by: Jessica Yu <jeyu@...hat.com>
> ---
> include/linux/livepatch.h | 13 +++++
> kernel/livepatch/core.c | 145 ++++++++++++++++++++++------------------------
> kernel/module.c | 10 ++++
> 3 files changed, 92 insertions(+), 76 deletions(-)
>
> diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
> index c056797..bd830d5 100644
> --- a/include/linux/livepatch.h
> +++ b/include/linux/livepatch.h
> @@ -24,6 +24,8 @@
> #include <linux/module.h>
> #include <linux/ftrace.h>
>
> +#if IS_ENABLED(CONFIG_LIVEPATCH)
> +
> #include <asm/livepatch.h>
>
> enum klp_state {
> @@ -132,4 +134,15 @@ int klp_unregister_patch(struct klp_patch *);
> int klp_enable_patch(struct klp_patch *);
> int klp_disable_patch(struct klp_patch *);
>
> +/* Called from the module loader during module coming/going states */
> +int klp_module_coming(struct module *mod);
> +void klp_module_going(struct module *mod);
> +
> +#else /* !CONFIG_LIVEPATCH */
> +
> +static inline int klp_module_coming(struct module *mod) { return 0; }
> +static inline void klp_module_going(struct module *mod) { }
> +
> +#endif /* CONFIG_LIVEPATCH */
> +
> #endif /* _LINUX_LIVEPATCH_H_ */
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index bc2c85c..e902377 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -99,12 +99,12 @@ static void klp_find_object_module(struct klp_object *obj)
> /*
> * 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.
> - * Note that the patch might still be needed before the going handler
> + * Do not mess work of klp_module_coming() and klp_module_going().
> + * 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.
> @@ -866,103 +866,106 @@ int klp_register_patch(struct klp_patch *patch)
> }
> EXPORT_SYMBOL_GPL(klp_register_patch);
>
> -static int klp_module_notify_coming(struct klp_patch *patch,
> - struct klp_object *obj)
> +int klp_module_coming(struct module *mod)
> {
> - 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 (ret) {
> - pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
> - pmod->name, mod->name, ret);
> - return ret;
> - }
> + if (WARN_ON(mod->state != MODULE_STATE_COMING))
> + return -EINVAL;
>
> - if (patch->state == KLP_DISABLED)
> - return 0;
> + mutex_lock(&klp_mutex);
> + /*
> + * 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",
> - pmod->name, mod->name);
> + 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;
>
> - ret = klp_enable_object(obj);
> - if (ret)
> - pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
> - pmod->name, mod->name, ret);
> - return ret;
> -}
> + obj->mod = mod;
>
> -static void klp_module_notify_going(struct klp_patch *patch,
> - struct klp_object *obj)
> -{
> - struct module *pmod = patch->mod;
> - struct module *mod = obj->mod;
> + ret = klp_init_object_loaded(patch, obj);
> + if (ret) {
> + pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
> + patch->mod->name, obj->mod->name, ret);
> + goto err;
> + }
>
> - if (patch->state == KLP_DISABLED)
> - goto disabled;
> + if (patch->state == KLP_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",
> - pmod->name, mod->name);
> + mutex_unlock(&klp_mutex);
>
> - 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);
> klp_free_object_loaded(obj);
> + mutex_unlock(&klp_mutex);
> +
> + return ret;
> }
>
> -static int klp_module_notify(struct notifier_block *nb, unsigned long action,
> - void *data)
> +void klp_module_going(struct module *mod)
> {
> - int ret;
> - struct module *mod = data;
> struct klp_patch *patch;
> struct klp_object *obj;
>
> - if (action != MODULE_STATE_COMING && action != MODULE_STATE_GOING)
> - return 0;
> + if (WARN_ON(mod->state != MODULE_STATE_GOING))
> + return;
If we're removing patch 2/3, then mod->state isn't necessarily GOING. I
think the check can probably just be removed altogether.
With that fixed,
Acked-by: Josh Poimboeuf <jpoimboe@...hat.com>
--
Josh
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