[for-linus][PATCH 04/20] function_graph: Use the saved entrys size when reprinting it

[Steven Rostedt]

From: Donggeun Yoo <donggeunyoo.kernel@xxxxxxxxx>

When a graph entry does not fit in the trace_seq, print_graph_entry()
saves it in the iterator's fgraph_data and reprints it on the next read.
The entry has already been consumed from the ring buffer by then, so the
copy is all that is left of it.

The copy is sized with iter->ent_size, which no longer describes the
saved entry but whatever entry the iterator has moved on to. The
argument count is derived from the same field, so a 72 byte entry saved
and then reprinted ahead of a 48 byte return entry loses its arguments.

Record the size next to the failure flag, so that the two are always set
together, and restore it before reprinting.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: ff5c9c576e75 ("ftrace: Add support for function argument to graph tracer")
Link: https://patch.msgid.link/20260906034406.1335316-1-donggeunyoo.kernel@xxxxxxxxx
Signed-off-by: Donggeun Yoo <donggeunyoo.kernel@xxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 kernel/trace/trace_functions_graph.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index ff7cb1a76b95..c5befd0c5b9a 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -52,6 +52,7 @@ struct fgraph_data {
 	};
 	struct ftrace_graph_ret_entry	ret;
 	int				failed;
+	int				ent_size;
 	int				cpu;
 };
 
@@ -1274,6 +1275,7 @@ print_graph_entry(struct ftrace_graph_ent_entry *field, struct trace_seq *s,
 		if (s->full) {
 			data->failed = 1;
 			data->cpu = cpu;
+			data->ent_size = iter->ent_size;
 		} else
 			data->failed = 0;
 	}
@@ -1457,6 +1459,7 @@ print_graph_function_flags(struct trace_iterator *iter, u32 flags)
 	if (data && data->failed) {
 		field = &data->ent.ent;
 		iter->cpu = data->cpu;
+		iter->ent_size = data->ent_size;
 		ret = print_graph_entry(field, s, iter, flags);
 		if (ret == TRACE_TYPE_HANDLED && iter->cpu != cpu) {
 			per_cpu_ptr(data->cpu_data, iter->cpu)->ignore = 1;
-- 
2.53.0