[v2] ftrace: Show subops in enabled_functions

Commit Message

Steven Rostedt April 10, 2025, 7:38 p.m. UTC

From: Steven Rostedt <[e-mail]>

The function graph infrastructure uses subops of the function tracer.
These are not shown in enabled_functions. Add a "subops:" section to the
enabled_functions line to show what functions are attached via subops. If
the subops is from the function_graph infrastructure, then show the entry
and return callbacks that are attached.

Here's an example of the output:

schedule_on_each_cpu (1)                tramp: 0xffffffffc03ef000 (ftrace_graph_func+0x0/0x60) ->ftrace_graph_func+0x0/0x60     subops: {ent:trace_graph_entry+0x0/0x20 ret:trace_graph_return+0x0/0x150}

Signed-off-by: Steven Rostedt (Google) <[e-mail]>
---
Changes since v1: https://lore.kernel.org/[e-mail]

- Add #ifdef CONFIG_FUNCTION_GRAPH_TRACER around the graph ops.
  The graph_ops isn't defined without that config and it fails
  the build. (Reported-by: kernel test robot <[e-mail]>)

 include/linux/ftrace.h |  2 ++
 kernel/trace/fgraph.c  |  2 ++
 kernel/trace/ftrace.c  | 38 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 42 insertions(+)

Patch

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index fbabc3d848b3..fc939ca2ff66 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -328,6 +328,7 @@  ftrace_func_t ftrace_ops_get_func(struct ftrace_ops *ops);
  * DIRECT - Used by the direct ftrace_ops helper for direct functions
  *            (internal ftrace only, should not be used by others)
  * SUBOP  - Is controlled by another op in field managed.
+ * GRAPH  - Is a component of the fgraph_ops structure
  */
 enum {
 	FTRACE_OPS_FL_ENABLED			= BIT(0),
@@ -349,6 +350,7 @@  enum {
 	FTRACE_OPS_FL_PERMANENT                 = BIT(16),
 	FTRACE_OPS_FL_DIRECT			= BIT(17),
 	FTRACE_OPS_FL_SUBOP			= BIT(18),
+	FTRACE_OPS_FL_GRAPH			= BIT(19),
 };
 
 #ifndef CONFIG_DYNAMIC_FTRACE_WITH_ARGS
diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
index 8d925cbdce3a..c5b207992fb4 100644
--- a/kernel/trace/fgraph.c
+++ b/kernel/trace/fgraph.c
@@ -1382,6 +1382,8 @@  int register_ftrace_graph(struct fgraph_ops *gops)
 	/* Always save the function, and reset at unregistering */
 	gops->saved_func = gops->entryfunc;
 
+	gops->ops.flags |= FTRACE_OPS_FL_GRAPH;
+
 	ret = ftrace_startup_subops(&graph_ops, &gops->ops, command);
 	if (!ret)
 		fgraph_array[i] = gops;
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 1a48aedb5255..b0e8d95312e4 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -4323,6 +4323,42 @@  static inline int print_rec(struct seq_file *m, unsigned long ip)
 }
 #endif
 
+static void print_subops(struct seq_file *m, struct ftrace_ops *ops, struct dyn_ftrace *rec)
+{
+	struct ftrace_ops *subops;
+	bool first = true;
+
+	list_for_each_entry(subops, &ops->subop_list, list) {
+		if (!((subops->flags & FTRACE_OPS_FL_ENABLED) &&
+		      hash_contains_ip(rec->ip, subops->func_hash)))
+			continue;
+		if (first) {
+			seq_printf(m, "\tsubops:");
+			first = false;
+		}
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+		if (subops->flags & FTRACE_OPS_FL_GRAPH) {
+			struct fgraph_ops *gops;
+
+			gops = container_of(subops, struct fgraph_ops, ops);
+			seq_printf(m, " {ent:%pS ret:%pS}",
+				   (void *)gops->entryfunc,
+				   (void *)gops->retfunc);
+			continue;
+		}
+#endif
+		if (subops->trampoline) {
+			seq_printf(m, " {%pS (%pS)}",
+				   (void *)subops->trampoline,
+				   (void *)subops->func);
+			add_trampoline_func(m, subops, rec);
+		} else {
+			seq_printf(m, " {%pS}",
+				   (void *)subops->func);
+		}
+	}
+}
+
 static int t_show(struct seq_file *m, void *v)
 {
 	struct ftrace_iterator *iter = m->private;
@@ -4375,6 +4411,7 @@  static int t_show(struct seq_file *m, void *v)
 						   (void *)ops->trampoline,
 						   (void *)ops->func);
 					add_trampoline_func(m, ops, rec);
+					print_subops(m, ops, rec);
 					ops = ftrace_find_tramp_ops_next(rec, ops);
 				} while (ops);
 			} else
@@ -4387,6 +4424,7 @@  static int t_show(struct seq_file *m, void *v)
 			if (ops) {
 				seq_printf(m, "\tops: %pS (%pS)",
 					   ops, ops->func);
+				print_subops(m, ops, rec);
 			} else {
 				seq_puts(m, "\tops: ERROR!");
 			}