[PATCH 1/2] tracing: Store trace_marker_raw payload length in events

[Cao Ruichuang]

trace_marker_raw currently records its bytes in TRACE_RAW_DATA events,
but the event output path derives the byte count from the padded record
size in the ring buffer. As a result, the printed raw-data payload is
rounded up and small writes do not preserve their true length.

Keep the true payload length in the TRACE_RAW_DATA event itself and use
that field when printing the bytes. This leaves the ring buffer record
size semantics unchanged while letting trace_marker_raw report the exact
payload that was written.

Signed-off-by: Cao Ruichuang <create0818@xxxxxxx>
---
 kernel/trace/trace.c         | 11 ++++++-----
 kernel/trace/trace_entries.h |  1 +
 kernel/trace/trace_output.c  |  4 ++--
 3 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a626211ce..d9cb643b8 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6906,11 +6906,13 @@ static ssize_t write_raw_marker_to_buffer(struct trace_array *tr,
 	struct ring_buffer_event *event;
 	struct trace_buffer *buffer;
 	struct raw_data_entry *entry;
+	size_t payload_len;
 	ssize_t written;
 	size_t size;
 
 	/* cnt includes both the entry->id and the data behind it. */
-	size = struct_offset(entry, id) + cnt;
+	payload_len = cnt - sizeof(entry->id);
+	size = struct_offset(entry, buf) + payload_len;
 
 	buffer = tr->array_buffer.buffer;
 
@@ -6924,10 +6926,9 @@ static ssize_t write_raw_marker_to_buffer(struct trace_array *tr,
 		return -EBADF;
 
 	entry = ring_buffer_event_data(event);
-	unsafe_memcpy(&entry->id, buf, cnt,
-		      "id and content already reserved on ring buffer"
-		      "'buf' includes the 'id' and the data."
-		      "'entry' was allocated with cnt from 'id'.");
+	memcpy(&entry->id, buf, sizeof(entry->id));
+	entry->len = payload_len;
+	memcpy(entry->buf, buf + sizeof(entry->id), payload_len);
 	written = cnt;
 
 	__buffer_unlock_commit(buffer, event);
diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
index 54417468f..5f867a144 100644
--- a/kernel/trace/trace_entries.h
+++ b/kernel/trace/trace_entries.h
@@ -288,6 +288,7 @@ FTRACE_ENTRY(raw_data, raw_data_entry,
 
 	F_STRUCT(
 		__field(	unsigned int,	id	)
+		__field(unsigned int, len)
 		__dynamic_array(	char,	buf	)
 	),
 
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 1996d7aba..4e1edfa05 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -1817,13 +1817,13 @@ static enum print_line_t trace_raw_data(struct trace_iterator *iter, int flags,
 					 struct trace_event *event)
 {
 	struct raw_data_entry *field;
-	int i;
+	unsigned int i;
 
 	trace_assign_type(field, iter->ent);
 
 	trace_seq_printf(&iter->seq, "# %x buf:", field->id);
 
-	for (i = 0; i < iter->ent_size - offsetof(struct raw_data_entry, buf); i++)
+	for (i = 0; i < field->len; i++)
 		trace_seq_printf(&iter->seq, " %02x",
 				 (unsigned char)field->buf[i]);
 
-- 
2.39.5 (Apple Git-154)