perf ftrace: Add support for tracing option 'func_stack_trace'

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

Example:

  $ sudo perf ftrace -T vfs_read --func-opts 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>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Link: http://lore.kernel.org/lkml/20200808023141.14227-9-changbin.du@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf-ftrace.txt

@@ -76,6 +76,10 @@ OPTIONS
 	specify multiple functions (or glob patterns).  It will be
 	passed to 'set_ftrace_notrace' in tracefs.
 
+--func-opts::
+	List of options allowed to set:
+	  call-graph - Display kernel stack trace for function tracer.
+
 -G::
 --graph-funcs=::
 	Select function_graph tracer and set graph filter on the given

tools/perf/builtin-ftrace.c

@@ -27,6 +27,7 @@
 #include "util/cap.h"
 #include "util/config.h"
 #include "util/units.h"
+#include "util/parse-sublevel-options.h"
 
 #define DEFAULT_TRACER  "function_graph"
 
@@ -42,6 +43,7 @@ struct perf_ftrace {
 	int			graph_depth;
 	unsigned long		percpu_buffer_size;
 	bool			inherit;
+	int			func_stack_trace;
 };
 
 struct filter_entry {
@@ -202,6 +204,7 @@ 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)
@@ -278,6 +281,17 @@ 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);
@@ -426,6 +440,11 @@ 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;
@@ -598,6 +617,26 @@ static int parse_buffer_size(const struct option *opt,
 	return -1;
 }
 
+static int parse_func_tracer_opts(const struct option *opt,
+				  const char *str, int unset)
+{
+	int ret;
+	struct perf_ftrace *ftrace = (struct perf_ftrace *) opt->value;
+	struct sublevel_option func_tracer_opts[] = {
+		{ .name = "call-graph",	.value_ptr = &ftrace->func_stack_trace },
+		{ .name = NULL, }
+	};
+
+	if (unset)
+		return 0;
+
+	ret = perf_parse_sublevel_options(str, func_tracer_opts);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
 static void select_tracer(struct perf_ftrace *ftrace)
 {
 	bool graph = !list_empty(&ftrace->graph_funcs) ||
@@ -645,6 +684,9 @@ 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_CALLBACK(0, "func-opts", &ftrace, "options",
+		     "function tracer options, available options: call-graph",
+		     parse_func_tracer_opts),
 	OPT_CALLBACK('G', "graph-funcs", &ftrace.graph_funcs, "func",
 		     "trace given functions using function_graph tracer",
 		     parse_filter_func),