linux-kernel - Re: [PATCH 05/19] perf ftrace: add option '-l/--list-functions' to list available functions

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Date:   Sat, 6 Jun 2020 22:42:53 +0800
From:   Changbin Du <changbin.du@...il.com>
To:     Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
Cc:     Changbin Du <changbin.du@...il.com>, Jiri Olsa <jolsa@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 05/19] perf ftrace: add option '-l/--list-functions' to
 list available functions

On Wed, May 20, 2020 at 05:59:40PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Sun, May 10, 2020 at 11:06:14PM +0800, Changbin Du escreveu:
> > This adds an option '-l/--list-functions' to list all available functions
> > which is read from tracing file 'available_filter_functions'.
> 
> Here, in 'perf probe' we have:
> 
> [acme@...e perf]$ perf probe -F tcp_* | head
> tcp_abort
> tcp_ack
> tcp_ack_update_rtt.isra.0
> tcp_add_backlog
> tcp_add_reno_sack
> tcp_adjust_pcount
> tcp_alloc_md5sig_pool
> tcp_any_retrans_done.part.0
> tcp_assign_congestion_control
> tcp_bpf_clone
> [acme@...e perf]$ perf probe -h -F
> 
>  Usage: perf probe [<options>] 'PROBEDEF' ['PROBEDEF' ...]
>     or: perf probe [<options>] --add 'PROBEDEF' [--add 'PROBEDEF' ...]
>     or: perf probe [<options>] --del '[GROUP:]EVENT' ...
>     or: perf probe --list [GROUP:]EVENT ...
>     or: perf probe [<options>] --line 'LINEDESC'
>     or: perf probe [<options>] --vars 'PROBEPOINT'
>     or: perf probe [<options>] --funcs
> 
>     -F, --funcs <[FILTER]>
>                           Show potential probe-able functions.
> 
> [acme@...e perf]$
> 
> So I think we should align with this.
> 
> - Arnaldo
>
Agreed. Will do that in next revision.

> > Signed-off-by: Changbin Du <changbin.du@...il.com>
> > ---
> >  tools/perf/builtin-ftrace.c | 43 +++++++++++++++++++++++++++++++++++++
> >  1 file changed, 43 insertions(+)
> > 
> > diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> > index 1d30c2d5f88b..8133d910d5d8 100644
> > --- a/tools/perf/builtin-ftrace.c
> > +++ b/tools/perf/builtin-ftrace.c
> > @@ -33,6 +33,7 @@ struct perf_ftrace {
> >  	struct evlist		*evlist;
> >  	struct target		target;
> >  	const char		*tracer;
> > +	bool			list_avail_functions;
> >  	struct list_head	filters;
> >  	struct list_head	notrace;
> >  	struct list_head	graph_funcs;
> > @@ -142,6 +143,43 @@ static int write_tracing_option_file(const char *name, const char *val)
> >  	return ret;
> >  }
> >  
> > +static int read_tracing_file_to_stdout(const char *name)
> > +{
> > +	char buf[4096];
> > +	char *file;
> > +	int fd;
> > +	int ret = -1;
> > +
> > +	file = get_tracing_file(name);
> > +	if (!file) {
> > +		pr_debug("cannot get tracing file: %s\n", name);
> > +		return -1;
> > +	}
> > +
> > +	fd = open(file, O_RDONLY);
> > +	if (fd < 0) {
> > +		pr_debug("cannot open tracing file: %s: %s\n",
> > +			 name, str_error_r(errno, buf, sizeof(buf)));
> > +		goto out;
> > +	}
> > +
> > +	/* read contents to stdout */
> > +	while (true) {
> > +		int n = read(fd, buf, sizeof(buf));
> > +		if (n <= 0)
> > +			goto out_close;
> > +		if (fwrite(buf, n, 1, stdout) != 1)
> > +			goto out_close;
> > +	}
> > +	ret = 0;
> > +
> > +out_close:
> > +	close(fd);
> > +out:
> > +	put_tracing_file(file);
> > +	return ret;
> > +}
> > +
> >  static int reset_tracing_cpu(void);
> >  static void reset_tracing_filters(void);
> >  
> > @@ -332,6 +370,9 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
> >  	signal(SIGCHLD, sig_handler);
> >  	signal(SIGPIPE, sig_handler);
> >  
> > +	if (ftrace->list_avail_functions)
> > +		return read_tracing_file_to_stdout("available_filter_functions");
> > +
> >  	if (reset_tracing_files(ftrace) < 0) {
> >  		pr_err("failed to reset ftrace\n");
> >  		goto out;
> > @@ -483,6 +524,8 @@ int cmd_ftrace(int argc, const char **argv)
> >  		NULL
> >  	};
> >  	const struct option ftrace_options[] = {
> > +	OPT_BOOLEAN('L', "list-functions", &ftrace.list_avail_functions,
> > +		    "List available functions to filter"),
> >  	OPT_STRING('p', "pid", &ftrace.target.pid, "pid",
> >  		   "trace on existing process id"),
> >  	OPT_INCR('v', "verbose", &verbose,
> > -- 
> > 2.25.1
> > 
> 
> -- 
> 
> - Arnaldo

-- 
Cheers,
Changbin Du