tracing/synthetic: Fix trace_string() return value

commit 9b6326354cf9a41521b79287da3bfab022ae0b6d upstream.

Fix trace_string() by assigning the string length to the return variable
which got lost in commit ddeea494a16f ("tracing/synthetic: Use union
instead of casts") and caused trace_string() to always return 0.

Link: https://lore.kernel.org/linux-trace-kernel/20240214220555.711598-1-thorsten.blum@toblux.com
Cc: stable@vger.kernel.org
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes: ddeea494a16f ("tracing/synthetic: Use union instead of casts")
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
index e7af286af4f1ad9d3ac578cb3ce3c58ba3d5ce0b..c82b401a294d961ae75c48f3a164e92f3ad181b1 100644 (file)
--- a/kernel/trace/trace_events_synth.c
+++ b/kernel/trace/trace_events_synth.c
@@ -441,8 +441,9 @@ static unsigned int trace_string(struct synth_trace_event *entry,
        if (is_dynamic) {
                union trace_synth_field *data = &entry->fields[*n_u64];
 
+               len = fetch_store_strlen((unsigned long)str_val);
                data->as_dynamic.offset = struct_size(entry, fields, event->n_u64) + data_size;
-               data->as_dynamic.len = fetch_store_strlen((unsigned long)str_val);
+               data->as_dynamic.len = len;
 
                ret = fetch_store_string((unsigned long)str_val, &entry->fields[*n_u64], entry);