[PATCH] livepatch: clean up klp_find_object_module() usage: was: Re: [PATCHv4 2/3] kernel: add support for live patching

[Petr Mladek]

On Fri 2014-11-28 18:07:37, Petr Mladek wrote:
> On Tue 2014-11-25 11:15:08, Seth Jennings wrote:
> > This commit introduces code for the live patching core.  It implements
> > an ftrace-based mechanism and kernel interface for doing live patching
> > of kernel and kernel module functions.

[...]

> > +/* sets obj->mod if object is not vmlinux and module is found */
> > +static bool klp_find_object_module(struct klp_object *obj)
> > +{
> > +	if (!obj->name)
> > +		return 1;
> > +
> > +	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.
> > +	 */
> > +	obj->mod = find_module(obj->name);
> > +	mutex_unlock(&module_mutex);
> > +
> > +	return !!obj->mod;
> 
> I know that this is effective to return boolean here because
> it handles also patch against the kernel core (vmlinux). But
> the logic looks tricky. I would prefer a cleaner design and
> use this function only to set obj->mod.
> 
> I wanted to see how it would look like, so I will send a patch for
> this in a separate mail.

The patch is below. Of course, merge it into the original
patch if you agree with the idea, please.