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

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Date:   Tue, 22 Aug 2023 15:13:32 +0200
From:   Jiri Olsa <olsajiri@...il.com>
To:     Francis Laniel <flaniel@...ux.microsoft.com>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Jiri Olsa <olsajiri@...il.com>, 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

On Mon, Aug 21, 2023 at 02:24:06PM +0200, Francis Laniel wrote:
> 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?

hum, I don't see the release code going through the list of appended probes,
so I wonder you need to somehow do that in destroy_local_trace_kprobe

jirka