Re: livepatch: Implement separate coming and going module notifiers

[Jessica Yu]

+++ Steven Rostedt [29/01/16 14:29 -0500]:
> On Fri, 29 Jan 2016 20:25:15 +0100 (CET)
> Miroslav Benes <mbenes@xxxxxxx> wrote:
>
> > It is possible to achieve the same goal even with the notifiers. They are
> > processed synchronously in complete_formation(). So we can put our klp
> > hook after that, right? Or better, put it to load_module() after
> > complete_formation() call. There is an error handling code even today
> > (that is, parse_args() or mod_sysfs_setup() can fail). Moreover, we'll
> > have a hook there with Jessica's relocation rework patch set.
>
> The problem with notifiers is that you don't know what is being called.
> A function call directly in the code, where it will always be needed if
> configured in, is a reasonable need to not use a notifier.

That's a pretty good reason. This bug popped up in the first place
due to a lack of clarity on which notifier gets called when.

> Although, I have to admit, if live kernel patching is configured in,
> it's not always needed to be called here, does it? With ftrace, the
> call has to be done when ftrace is configured in regardless if tracing
> is used or not.

Livepatch has to check if any of its patches affect the coming module,
so hardcoded or not it will still need to loop through the klp_patches
list like it does in the current notifiers.

Jessica