linux-kernel - Re: Question about 'for_each_kernel

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Date:   Sat, 22 Oct 2022 10:55:12 +0800
From:   richard clark <richard.xnu.clark@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     bristot@...nel.org, linux-trace-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: Question about 'for_each_kernel_tracepoint(...)' function

On Fri, Oct 21, 2022 at 8:32 PM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Fri, 21 Oct 2022 11:51:20 +0800
> richard clark <richard.xnu.clark@...il.com> wrote:
>
> > On Fri, Oct 21, 2022 at 10:12 AM Steven Rostedt <rostedt@...dmis.org> wrote:
> > >
> > > On Fri, 21 Oct 2022 09:43:14 +0800
> > > richard clark <richard.xnu.clark@...il.com> wrote:
> > >
> > >
> > > > Ah, as you can see that I did it, but the result is not what I
> > > > expected :-). Help?
> > >
> > > Looking at the code, I see it does indeed only look at builtin tracepoints.
> >
> > What the logic behind is not to implement a function like
> > 'for_each_tracepoints' instead of 'for_each_kernel_tracepoint' to find
> > all the TPs defined by both builtin kernel and external kernel
> > modules, just like we can find all the kernel symbols and exported
> > symbols from external module?
>
> Why? It's not needed upstream. If you push your code upstream and it's
> something to get accepted, then we can think about adding that.
>
> >
> > >
> > > But if you want one module to have access to the tracepoints of another,
> > > then you can have the first one export it.
> > >
> > > EXPORT_SYMBOL_TRACEPOINT_GPL(function_event_a);
> > >
> > > And then module b should have access to it.
> > >
> > Yes, but module b needs to register a new probe call back function for
> > the new TPs defined by module a in my case, so first it needs to find
> > the TPs defined by module a. Any comments?
>
> No, because I have no idea what you are doing or why you need this.

I've noticed that we have a Runtime Verification module merged into
the mainline and very interesting, so I am trying to provide a monitor
for my events in module A,  which means we need to register some new
probe call back functions for the TPs defined in the external kernel
modules. OK, I am writing this email just to confirm, maybe I need to
think about if I can add the external TPs into the
'for_each_kernel_tracepoint(...)' function...

Thanks!

>
> -- Steve