Re: [PATCH v6] tracing/eprobes: Allow use of BTF names to dereference pointers

[Steven Rostedt]

On Wed, 27 May 2026 10:08:15 -0400
Steven Rostedt <rostedt@xxxxxxxxxx> 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