[PATCH v5 02/17] perf ftrace: add option '-F/--funcs' to list available functions

[Changbin Du]

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

$ sudo ./perf ftrace -F | head
trace_initcall_finish_cb
initcall_blacklisted
do_one_initcall
do_one_initcall
trace_initcall_start_cb
run_init_process
try_to_run_init_process
match_dev_by_label
match_dev_by_uuid
rootfs_init_fs_context

Signed-off-by: Changbin Du <changbin...@gmail.com>

---
v2: option name '-l/--list-functions' -> '-F/--funcs'
---
 tools/perf/Documentation/perf-ftrace.txt |  4 +++
 tools/perf/builtin-ftrace.c              | 43 ++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/tools/perf/Documentation/perf-ftrace.txt 
b/tools/perf/Documentation/perf-ftrace.txt
index 952e46669168..d79560dea19f 100644
--- a/tools/perf/Documentation/perf-ftrace.txt
+++ b/tools/perf/Documentation/perf-ftrace.txt
@@ -30,6 +30,10 @@ OPTIONS
 --verbose=::
         Verbosity level.
 
+-F::
+--funcs::
+        List all available functions to trace.
+
 -p::
 --pid=::
        Trace on existing process id (comma separated list).
diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index 5f53da87040d..244cc8e6bd60 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -32,6 +32,7 @@ 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;
@@ -127,6 +128,43 @@ static int append_tracing_file(const char *name, const 
char *val)
        return __write_tracing_file(name, val, true);
 }
 
+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);
 
@@ -301,6 +339,9 @@ 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;
@@ -470,6 +511,8 @@ int cmd_ftrace(int argc, const char **argv)
        const struct option ftrace_options[] = {
        OPT_STRING('t', "tracer", &ftrace.tracer, "tracer",
                   "tracer to use: function or function_graph (This option is 
deprecated)"),
+       OPT_BOOLEAN('F', "funcs", &ftrace.list_avail_functions,
+                   "Show 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