Re: [BUGFIX PATCH] kprobes/x86: Remove IRQ disabling from jprobe handlers

From: Masami Hiramatsu
Date: Wed Oct 04 2017 - 10:08:14 EST

On Wed, 4 Oct 2017 12:41:01 +0200
Ingo Molnar <mingo@xxxxxxxxxx> wrote:

> * Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote:
> > Hmm, actually we can not disable jprobe, that has no separate Kconfig.
> > So we need to introduce new kconfig for that.
> >
> > And, there are several network protocols using jprobe to trace events.
> > I think they need to migrate to trace-event at first.
> >
> > So, how about below idea?
> >
> > 1. Introduce CONFIG_JPROBE_API which only separate jprobe general parts
> > (no arch dependent code involves) and make it default n.
> > 2. Mark break_handler and jprobe APIs deprecated so that no new user comes up.
> > 3. migrate in-kernel jprobe user to trace-event or ftrace.
> > (may take some time)
> So my suggestion would be to just return from register_jprobe() and don't register
> anything.

with CONFIG_JPROBE_API=n, is that right?

> Yes, there are usecases of jprobes in the kernel, but they all look
> pretty ancient and unused.

Hmm, in that case, should we also remove those users? If we disable such way
those features are just useless.

> So let's try this for -next and see whether anyone has a real usecase. And no
> Kconfig and deprecation messages - those don't really work in practice - just
> disable the functionality and force people to (trivially) modify the source if
> they want to re-enable it.

So you mean I don't have to change those usecases, just let them do.

> If this is fine for a single release then we can just remove it all:
> > 4. after that, we can completely remove jprobe which will be a series for
> > all archs. (or just one big patch?)
> we want a series of patches - but that's for later.

OK :)

Thank you,

> Thanks,
> Ingo

Masami Hiramatsu <mhiramat@xxxxxxxxxx>