Document tracing

Author: Rot127

README.md

@@ -22,6 +22,18 @@ cd build
 make
 ```
 
+## Tracing a binary
+
+The plugin takes two required arguments:
+
+`bin_path`: The path to the binary emulated. Due to a [QEMU bug](https://gitlab.com/qemu-project/qemu/-/issues/3014) this cannot be inferred.
+`out`: The output file to save the trace into.
+
+```bash
+./qemu-sparc64 -plugin file=./contrib/plugins/bap-tracing/libbap_tracing.so,bin_path=<bin_path>,out=<output-file> -d plugin <bin_path>
+ls <output-file>
+```
+
 ## Trace format
 
 The generated trace consists of three parts: the header,

contrib/plugins/bap-tracing/frame_buffer.c

@@ -271,6 +271,7 @@ static size_t mval_type_to_int(enum qemu_plugin_mem_value_type type) {
   default:
     g_assert(false);
   }
+  return 0;
 }
 
 static void mval_to_buf(qemu_plugin_mem_value *val, uint8_t *buf) {