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

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Date:   Sun, 10 May 2020 23:06:14 +0800
From:   Changbin Du <changbin.du@...il.com>
To:     Jiri Olsa <jolsa@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     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, Changbin Du <changbin.du@...il.com>
Subject: [PATCH 05/19] perf ftrace: add option '-l/--list-functions' to list available functions

This adds an option '-l/--list-functions' to list all available functions
which is read from tracing file 'available_filter_functions'.

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