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Date: Wed, 27 May 2026 10:16:25 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: Jiri Olsa <olsajiri@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>, Linux trace kernel
 <linux-trace-kernel@vger.kernel.org>, Masami Hiramatsu
 <mhiramat@kernel.org>, Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
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 <zanussi@kernel.org>, Andrew Morton <akpm@linux-foundation.org>, Thomas
 Gleixner <tglx@linutronix.de>, Ian Rogers <irogers@google.com>
Subject: Re: [PATCH v6] tracing/eprobes: Allow use of BTF names to
 dereference pointers
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On Wed, 27 May 2026 10:08:15 -0400
Steven Rostedt <rostedt@kernel.org> wrote:

> > this seems to be supported only for argument (pointer) stored in the trace record,
> > not the actual arguments to the tracepoint, is that right?
> > 
> > so I can deref worker from sched.sched_kthread_work_queue_work, like:
> > 
> >   echo 'e:myprobe sched.sched_kthread_work_queue_work (kthread_worker)worker->flags (kthread_work)work->canceling' > dynamic_events  
> 
> Correct, that is because eprobes "e:" works on the output of a trace event.
> 
> 
> > 
> > but I can't deref sched.sched_process_exec p->pid, like:
> > 
> >   # echo 'e:myprobe sched.sched_process_exec (task_struct)p->pid' > dynamic_events
> >   bash: echo: write error: Invalid argument  
> 
> For function prototypes of a tracepoint, you would use a tprobe "t:"
> 
>  # echo 't:exec sched_process_exec pid=p->pid' > dynamic_events


Hmm, this is why I need to write a book ;-)

Thanks for helping with what content I need to add!

-- Steve