linux-kernel - Re: livepatch: Implement separate coming and going module notifiers

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Date:	Fri, 29 Jan 2016 19:02:47 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Jessica Yu <jeyu@...hat.com>
Cc:	Josh Poimboeuf <jpoimboe@...hat.com>,
	Miroslav Benes <mbenes@...e.cz>,
	Seth Jennings <sjenning@...hat.com>,
	Jiri Kosina <jikos@...nel.org>,
	Vojtech Pavlik <vojtech@...e.com>,
	Ingo Molnar <mingo@...hat.com>, live-patching@...r.kernel.org,
	linux-kernel@...r.kernel.org, Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: livepatch: Implement separate coming and going module notifiers

On Fri, 29 Jan 2016 17:58:29 -0500
Jessica Yu <jeyu@...hat.com> wrote:

> diff --git a/kernel/module.c b/kernel/module.c
> index 8358f46..eccd289 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -979,8 +979,12 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user,
>  	/* Final destruction now no one is using it. */
>  	if (mod->exit != NULL)
>  		mod->exit();
>  	blocking_notifier_call_chain(&module_notify_list,
>  				     MODULE_STATE_GOING, mod);
> +	klp_module_disable(mod);
> +	ftrace_release_mod(mod);
> +
>  	async_synchronize_full();
>  
>  	/* Store the name of the last unloaded module for diagnostic purposes */
> @@ -3371,6 +3375,13 @@ static int complete_formation(struct module *mod, struct load_info *info)
>  	mod->state = MODULE_STATE_COMING;
>  	mutex_unlock(&module_mutex);
>  
> +	ftrace_module_enable(mod);
> +	err = klp_module_enable(mod); // write all relocations before calling coming notifiers
> +	if (err) {
> +		ftrace_release_mod(mod);

This isn't needed. If complete_formation() fails with an error, then
its caller (load_module) will do the clean up and call
ftrace_release_mod().

-- Steve

> +		goto out;
> +	}
> +
>  	blocking_notifier_call_chain(&module_notify_list,
>  				     MODULE_STATE_COMING, mod);
>  	return 0;
>