netdev - Re: [RFC][PATCH 1/2] ftrace: Add modify_ftrace

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Date:   Tue, 19 Nov 2019 07:37:23 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     bpf <bpf@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [RFC][PATCH 1/2] ftrace: Add modify_ftrace_direct()

On Tue, Nov 19, 2019 at 6:13 AM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Mon, 18 Nov 2019 22:04:28 -0800
> Alexei Starovoitov <alexei.starovoitov@...il.com> wrote:
>
> > I took your for-next without the extra patch and used it from bpf trampoline.
> > It's looking good so far. Passed basic testing. Will add more stress tests.
> >
> > Do you mind doing:
> > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> > index 73eb2e93593f..6ddb203ca550 100644
> > --- a/include/linux/ftrace.h
> > +++ b/include/linux/ftrace.h
> > @@ -256,16 +256,16 @@ struct ftrace_direct_func
> > *ftrace_find_direct_func(unsigned long addr);
> >  # define ftrace_direct_func_count 0
> >  static inline int register_ftrace_direct(unsigned long ip, unsigned long addr)
> >  {
> > -       return -ENODEV;
> > +       return -ENOTSUPP;
> >  }
> >  static inline int unregister_ftrace_direct(unsigned long ip, unsigned
> > long addr)
> >  {
> > -       return -ENODEV;
> > +       return -ENOTSUPP;
> >  }
> >  static inline int modify_ftrace_direct(unsigned long ip,
> >                                        unsigned long old_addr,
> > unsigned long new_addr)
> >  {
> > -       return -ENODEV;
> > +       return -ENOTSUPP;
> >  }
> >
> > otherwise ENODEV is a valid error when ip is incorrect which is
> > indistinguishable from ftrace not compiled in.
>
> Sure I can add this. Want to add a Signed-off-by to it, and I'll just
> pull it in directly? I can write up the change log.

Whichever way is easier for you.
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
Thanks!

> -- Steve