[for-next][PATCH 02/31] tracing: Show function names when possible when listing fields

[Steven Rostedt]

From: Steven Rostedt <rostedt@xxxxxxxxxxx>

When the "fields" option is enabled, the "print fmt" of the trace event is
ignored and only the fields are printed. But some fields contain function
pointers. Instead of just showing the hex value in this case, show the
function name when possible:

Instead of having:

 # echo 1 > options/fields
 # cat trace
 [..]
  kmem_cache_free: call_site=0xffffffffa9afcf31 (-1448095951) ptr=0xffff888124452910 (-131386736039664) name=kmemleak_object

Have it output:

  kmem_cache_free: call_site=rcu_do_batch+0x3d1/0x14a0 (-1768960207) ptr=0xffff888132ea5ed0 (854220496) name=kmemleak_object

Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/20250325213919.624181915@xxxxxxxxxxx
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
---
 kernel/trace/trace_output.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index aab6816f0249..73037efdb45f 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -1015,14 +1015,24 @@ static void print_fields(struct trace_iterator *iter, struct trace_event_call *c
 					break;
 				}
 
-				trace_seq_printf(&iter->seq, "0x%x (%d)",
-						 *(unsigned int *)pos,
-						 *(unsigned int *)pos);
+				if (sizeof(long) == 4)
+					trace_seq_printf(&iter->seq, "%pS (%d)",
+							 *(void **)pos,
+							 *(unsigned int *)pos);
+				else
+					trace_seq_printf(&iter->seq, "0x%x (%d)",
+							 *(unsigned int *)pos,
+							 *(unsigned int *)pos);
 				break;
 			case 8:
-				trace_seq_printf(&iter->seq, "0x%llx (%lld)",
-						 *(unsigned long long *)pos,
-						 *(unsigned long long *)pos);
+				if (sizeof(long) == 8)
+					trace_seq_printf(&iter->seq, "%pS (%lld)",
+							 *(void **)pos,
+							 *(unsigned long long *)pos);
+				else
+					trace_seq_printf(&iter->seq, "0x%llx (%lld)",
+							 *(unsigned long long *)pos,
+							 *(unsigned long long *)pos);
 				break;
 			default:
 				trace_seq_puts(&iter->seq, "<INVALID-SIZE>");
-- 
2.47.2