linux-kernel - Re: Question about 'for_each_kernel

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Message-ID: <CAJNi4rPPDp0xeEmqMBqX-pBqgAX7Biivyd+P_zhC7Y0-K3W0VQ@mail.gmail.com>
Date:   Fri, 21 Oct 2022 11:51:20 +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 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?

>
> 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?

> -- Steve