linux-kernel - Re: [PATCH perf/core v2 4/4] perf-probe: Find probe events without target module

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Message-ID: <20170116184455.GA14872@kernel.org>
Date:   Mon, 16 Jan 2017 15:44:55 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Jiri Olsa <jolsa@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>
Subject: Re: [PATCH perf/core v2 4/4] perf-probe: Find probe events without
 target module

Em Wed, Jan 11, 2017 at 03:03:06PM +0900, Masami Hiramatsu escreveu:
> Find probe events without -m "module" option. If perf-probe
> failed to find given function in kernel image, it tries to
> find same symbol and module in kallsyms, and retry search
> in the found module. E.g.
> 
>   # perf probe -D i915_capabilities
>   p:probe/i915_capabilities i915:i915_capabilities+0
> 
> Note: without -m option, perf probe can not find inlined
> function since there is no symbol information in kallsyms.

As this is a new feature, I'll postpone merging it till we get
perf/urgent, with the first three patches in this series, merged into
perf/core, ok?

- Arnaldo
 
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> Suggested-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> ---
>   Changes in v2:
>    - Fix to remove unneeded zero-return.
>    - Remove unneeded debug message.
> ---
>  tools/perf/util/probe-event.c |   69 ++++++++++++++++++++++++++++++-----------
>  1 file changed, 51 insertions(+), 18 deletions(-)
> 
> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> index 6a6f44d..715f330 100644
> --- a/tools/perf/util/probe-event.c
> +++ b/tools/perf/util/probe-event.c
> @@ -858,11 +858,7 @@ static int try_to_find_probe_trace_events(struct perf_probe_event *pev,
>  
>  	debuginfo__delete(dinfo);
>  
> -	if (ntevs == 0)	{	/* No error but failed to find probe point. */
> -		pr_warning("Probe point '%s' not found.\n",
> -			   synthesize_perf_probe_point(&pev->point));
> -		return -ENOENT;
> -	} else if (ntevs < 0) {
> +	if (ntevs < 0) {
>  		/* Error path : ntevs < 0 */
>  		pr_debug("An error occurred in debuginfo analysis (%d).\n", ntevs);
>  		if (ntevs == -EBADF)
> @@ -2829,9 +2825,7 @@ static int find_probe_trace_events_from_map(struct perf_probe_event *pev,
>  	 */
>  	num_matched_functions = find_probe_functions(map, pp->function, syms);
>  	if (num_matched_functions == 0) {
> -		pr_err("Failed to find symbol %s in %s\n", pp->function,
> -			pev->target ? : "kernel");
> -		ret = -ENOENT;
> +		ret = 0;
>  		goto out;
>  	} else if (num_matched_functions > probe_conf.max_probes) {
>  		pr_err("Too many functions matched in %s\n",
> @@ -3233,6 +3227,42 @@ static int find_probe_trace_events_from_cache(struct perf_probe_event *pev,
>  	return ret;
>  }
>  
> +static int __convert_to_probe_trace_events(struct perf_probe_event *pev,
> +					   struct probe_trace_event **tevs)
> +{
> +	int ret;
> +
> +	/* At first, we need to lookup cache entry */
> +	ret = find_probe_trace_events_from_cache(pev, tevs);
> +	if (ret > 0 || pev->sdt)	/* SDT can be found only in the cache */
> +		return ret == 0 ? -ENOENT : ret; /* Found in probe cache */
> +
> +	/* Convert perf_probe_event with debuginfo */
> +	ret = try_to_find_probe_trace_events(pev, tevs);
> +	if (ret != 0)
> +		return ret;	/* Found in debuginfo or got an error */
> +
> +	return find_probe_trace_events_from_map(pev, tevs);
> +}
> +
> +static char *find_module_from_kallsyms(const char *symbol_name)
> +{
> +	struct machine *machine = machine__new_kallsyms();
> +	struct symbol *sym;
> +	struct map *map;
> +	char *module;
> +
> +	sym = machine__find_kernel_function_by_name(machine, symbol_name, &map);
> +	if (!sym || map->dso->short_name[0] != '[')
> +		return NULL;
> +	pr_debug("Found %s in %s\n", sym->name, map->dso->short_name);
> +	module = strdup(map->dso->short_name + 1);
> +	if (module)
> +		module[strlen(module) - 1] = '\0';
> +
> +	return module;
> +}
> +
>  static int convert_to_probe_trace_events(struct perf_probe_event *pev,
>  					 struct probe_trace_event **tevs)
>  {
> @@ -3255,17 +3285,20 @@ static int convert_to_probe_trace_events(struct perf_probe_event *pev,
>  	if (ret > 0)
>  		return ret;
>  
> -	/* At first, we need to lookup cache entry */
> -	ret = find_probe_trace_events_from_cache(pev, tevs);
> -	if (ret > 0 || pev->sdt)	/* SDT can be found only in the cache */
> -		return ret == 0 ? -ENOENT : ret; /* Found in probe cache */
> -
> -	/* Convert perf_probe_event with debuginfo */
> -	ret = try_to_find_probe_trace_events(pev, tevs);
> -	if (ret != 0)
> -		return ret;	/* Found in debuginfo or got an error */
> +	ret = __convert_to_probe_trace_events(pev, tevs);
> +	/* Not found. will retry to check kmodule if possible */
> +	if (ret == 0 && !pev->uprobes && !pev->target) {
> +		pev->target = find_module_from_kallsyms(pev->point.function);
> +		if (pev->target)
> +			ret = __convert_to_probe_trace_events(pev, tevs);
> +	}
>  
> -	return find_probe_trace_events_from_map(pev, tevs);
> +	if (ret == 0) {
> +		pr_warning("Probe point '%s' not found.\n",
> +			   synthesize_perf_probe_point(&pev->point));
> +		ret = -ENOENT;
> +	}
> +	return ret;
>  }
>  
>  int convert_perf_probe_events(struct perf_probe_event *pevs, int npevs)