linux-kernel - Re: [RFC PATCH v1 1/1] tracing/kprobe: Add multi-probe support for 'perf

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Date:   Mon, 21 Aug 2023 14:24:06 +0200
From:   Francis Laniel <flaniel@...ux.microsoft.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>,
        Jiri Olsa <olsajiri@...il.com>
Cc:     linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
        linux-trace-kernel@...r.kernel.org,
        Song Liu <songliubraving@...com>, bpf@...r.kernel.org
Subject: Re: [RFC PATCH v1 1/1] tracing/kprobe: Add multi-probe support for 'perf_kprobe' PMU

Hi.

Le dimanche 20 août 2023, 22:34:40 CEST Jiri Olsa a écrit :
> On Sat, Aug 19, 2023 at 10:11:05AM +0900, Masami Hiramatsu wrote:
> 
> SNIP
> 
> > > > > > > +	func_addr = kallsyms_lookup_name(func);
> > > > > > > +	for (i = 0; i < array.size; i++) {
> > > > > > > +		struct trace_kprobe *tk_same_name;
> > > > > > > +		unsigned long address;
> > > > > > > +
> > > > > > > +		address = array.addrs[i];
> > > > > > > +		/* Skip the function address as we already 
registered it. */
> > > > > > > +		if (address == func_addr)
> > > > > > > +			continue;
> > > > > > > +
> > > > > > > +		/*
> > > > > > > +		 * alloc_trace_kprobe() first considers symbol name, 
so we
> > > > > > > set
> > > > > > > +		 * this to NULL to allocate this kprobe on the given 
address.
> > > > > > > +		 */
> > > > > > > +		tk_same_name = 
alloc_trace_kprobe(KPROBE_EVENT_SYSTEM, event,
> > > > > > > +						  (void *)address, NULL, 
offs,
> > > > > > > +						  0 /* maxactive */,
> > > > > > > +						  0 /* nargs */, 
is_return);
> > > > > > > +
> > > > > > > +		if (IS_ERR(tk_same_name)) {
> > > > > > > +			ret = -ENOMEM;
> > > > > > > +			goto error_free;
> > > > > > > +		}
> > > > > > > +
> > > > > > > +		init_trace_event_call(tk_same_name);
> > > > > > > +
> > > > > > > +		if (traceprobe_set_print_fmt(&tk_same_name->tp, 
ptype) < 0) {
> > > > > > > +			ret = -ENOMEM;
> 
> also are we leaking tk_same_name in here?
> 
> > > > > > > +			goto error_free;
> > > > > > > +		}
> > > > > > > +
> > > > > > > +		ret = append_trace_kprobe(tk_same_name, tk);
> > > > > > > +		if (ret)
> 
> and here?

Good catch!
Do you know if the appended probes are automatically freed? If so, can you 
please indicate which function handles this?

> jirka
> 
> > > > > > > +			goto error_free;
> > > > > > > +	}
> > > > > > > +
> > > > > > > +end:
> > > > > > > +	kfree(array.addrs);
> > > > > > > 
> > > > > > >  	return trace_probe_event_call(&tk->tp);
> > > > > > > 
> > > > > > > +error_free:
> > > > > > > +	kfree(array.addrs);
> > > > > > > 
> > > > > > >  error:
> > > > > > >  	free_trace_kprobe(tk);
> > > > > > >  	return ERR_PTR(ret);
> > > > > 
> > > > > ---
> > > > > [1]: https://github.com/torvalds/linux/blob/
> > > > > 57012c57536f8814dec92e74197ee96c3498d24e/tools/perf/util/probe-event
> > > > > .c#L29
> > > > > 89- L2993

Best regards.