[PATCH v2 09/15] perf ftrace: add support for tracing option 'func_stack_trace'

[Changbin Du <changbin.du@gmail.com>]

This adds support to display call trace for function tracer. To do this,
just specify a '--func-call-graph' option.

$ sudo perf ftrace -T vfs_read --func-call-graph
 iio-sensor-prox-855   [003]   6168.369657: vfs_read <-ksys_read
 iio-sensor-prox-855   [003]   6168.369677: <stack trace>
 => vfs_read
 => ksys_read
 => __x64_sys_read
 => do_syscall_64
 => entry_SYSCALL_64_after_hwframe
 ...

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

---
v2: option name '-s' -> '--func-call-graph'
---
 tools/perf/Documentation/perf-ftrace.txt |  3 +++
 tools/perf/builtin-ftrace.c              | 20 ++++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/tools/perf/Documentation/perf-ftrace.txt b/tools/perf/Documentation/perf-ftrace.txt
index 66876e79cc24..94cdb2ebdf34 100644
--- a/tools/perf/Documentation/perf-ftrace.txt
+++ b/tools/perf/Documentation/perf-ftrace.txt
@@ -81,6 +81,9 @@ OPTIONS
 	(or glob patterns).  It will be passed to 'set_ftrace_notrace'
 	in tracefs.
 
+--func-call-graph::
+	Display kernel stack trace for function tracer.
+
 -G::
 --graph-funcs=::
 	Set graph filter on the given function (or a glob pattern).
diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index b2651b9bd6d0..bbfa7973b4fa 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -41,6 +41,7 @@ struct perf_ftrace {
 	unsigned		initial_delay;
 	unsigned		buffer_size_kb;
 	bool			inherit;
+	bool			func_stack_trace;
 };
 
 struct filter_entry {
@@ -198,6 +199,7 @@ static void reset_tracing_filters(void);
 static void reset_tracing_options(struct perf_ftrace *ftrace __maybe_unused)
 {
 	write_tracing_option_file("function-fork", "0");
+	write_tracing_option_file("func_stack_trace", "0");
 }
 
 static int reset_tracing_files(struct perf_ftrace *ftrace __maybe_unused)
@@ -274,6 +276,17 @@ static int set_tracing_cpu(struct perf_ftrace *ftrace)
 	return set_tracing_cpumask(cpumap);
 }
 
+static int set_tracing_func_stack_trace(struct perf_ftrace *ftrace)
+{
+	if (!ftrace->func_stack_trace)
+		return 0;
+
+	if (write_tracing_option_file("func_stack_trace", "1") < 0)
+		return -1;
+
+	return 0;
+}
+
 static int reset_tracing_cpu(void)
 {
 	struct perf_cpu_map *cpumap = perf_cpu_map__new(NULL);
@@ -421,6 +434,11 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
 		goto out_reset;
 	}
 
+	if (set_tracing_func_stack_trace(ftrace) < 0) {
+		pr_err("failed to set tracing option func_stack_trace\n");
+		goto out_reset;
+	}
+
 	if (set_tracing_filters(ftrace) < 0) {
 		pr_err("failed to set tracing filters\n");
 		goto out_reset;
@@ -605,6 +623,8 @@ int cmd_ftrace(int argc, const char **argv)
 			     parse_filter_func, "*"),
 	OPT_CALLBACK('N', "notrace-funcs", &ftrace.notrace, "func",
 		     "do not trace given functions", parse_filter_func),
+	OPT_BOOLEAN(0, "func-call-graph", &ftrace.func_stack_trace,
+		    "show kernel stack trace for function tracer"),
 	OPT_CALLBACK_DEFAULT('G', "graph-funcs", &ftrace.graph_funcs, "func",
 			     "trace given functions using function_graph tracer",
 			     parse_filter_func, "*"),
-- 
2.25.1