Re: [PATCH v2 02/15] perf ftrace: add option '-F/--funcs' to list available functions

From: Changbin Du
Date: Tue Jul 07 2020 - 11:16:04 EST


On Fri, Jul 03, 2020 at 02:58:19PM +0900, Namhyung Kim wrote:
> On Sat, Jun 27, 2020 at 10:37 PM Changbin Du <changbin.du@xxxxxxxxx> wrote:
> >
> > 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.du@xxxxxxxxx>
> >
> > ---
> > 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 c5718503eded..e793118e83a9 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;
>
> It seems the return value cannot be 0?
>
If all above success, the return value is 0.

> Thanks
> Namhyung
>
> > +
> > +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
> >

--
Cheers,
Changbin Du