tracing: Fix endianness bug in histogram trigger

At least on PA-RISC and s390 synthetic histogram triggers are failing selftests because trace_event_raw_event_synth() always writes a 64 bit values, but the reader expects a field->size sized value. On little endian machines this doesn't hurt, but on big endian this makes the reader always read zero values. Link: http://lore.kernel.org/linux-trace-devel/[email protected] Cc: [email protected] Fixes: 4b14793 ("tracing: Add support for 'synthetic' events") Acked-by: Tom Zanussi <[email protected]> Signed-off-by: Sven Schnelle <[email protected]> Signed-off-by: Steven Rostedt (VMware) <[email protected]>
IreneKnapp · Dec 21, 2019 · fe6e096 · fe6e096
1 parent 01f36a5
commit fe6e096
Showing 1 changed file with 20 additions and 1 deletion.
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
@@ -911,7 +911,26 @@ static notrace void trace_event_raw_event_synth(void *__data,
 			strscpy(str_field, str_val, STR_VAR_LEN_MAX);
 			n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
 		} else {
-			entry->fields[n_u64] = var_ref_vals[var_ref_idx + i];
+			struct synth_field *field = event->fields[i];
+			u64 val = var_ref_vals[var_ref_idx + i];
+
+			switch (field->size) {
+			case 1:
+				*(u8 *)&entry->fields[n_u64] = (u8)val;
+				break;
+
+			case 2:
+				*(u16 *)&entry->fields[n_u64] = (u16)val;
+				break;
+
+			case 4:
+				*(u32 *)&entry->fields[n_u64] = (u32)val;
+				break;
+
+			default:
+				entry->fields[n_u64] = val;
+				break;
+			}
 			n_u64++;
 		}
 	}