adds support for frame-local (cpu) modes (#17)

* adds support for frame-local (cpu) modes

This adds a new field `mode` to std frames, which corresponds to
Bap_trace_event_types.Mode, expressing for example whether the frame's
instruction was run in thumb mode or not.

While protobuf does maintain compatibility after adding fields, piqi
does not seem to explicitly make such an assertion. Thus, the format
version has been bumped to 3, to at least indicate the change. Broken
support for writing v1 traces has also been removed from C++ libtrace.

* catches unknown mode values

Author: thestr4ng3r

lib/frame_events.ml

@@ -48,6 +48,8 @@ module EF : sig
   val modload : arch option ->
     string -> Frame.address -> Frame.address -> Trace.event
 
+  val mode : string -> Trace.event
+
   (* val call : ??? *)
   (* val return : ??? *)
 end = struct
@@ -114,6 +116,9 @@ end = struct
       ~low:(addr_of_address arch low)
       ~high:(addr_of_address arch high) |>
     Value.create modload
+
+  let mode (fe : string) =
+    Value.create mode (try Mode.read fe with _exn -> Mode.unknown)
 end
 
 let of_new_frame context arch address thread_id =
@@ -152,9 +157,12 @@ let of_operand_info arch oi =
 let of_operand_value_list arch ovl =
   List.concat @@ List.map ~f:(of_operand_info arch) ovl
 
+let of_mode mode = [EF.mode mode]
+
 let of_std_frame context arch frm =
   let open Frame.Std_frame in
   List.concat [of_new_frame context arch frm.address frm.thread_id;
+               Option.value_map frm.mode ~default:[] ~f:(of_mode);
                [EF.code_exec arch frm.address frm.rawbytes];
                of_operand_value_list arch frm.operand_pre_list;
                Option.value_map frm.operand_post_list ~default:[]

libtrace/src/copytrace.cpp

@@ -25,7 +25,7 @@ int main(int argc, char **argv) {
   std::string dstfile(argv[2]);
 
   TraceContainerReader r(srcfile);
-  TraceContainerWriter w(dstfile, r.get_arch(), r.get_machine(), r.get_frames_per_toc_entry());
+  TraceContainerWriter w(dstfile, *r.get_meta(), r.get_arch(), r.get_machine(), r.get_frames_per_toc_entry());
 
   copy_all(r, w);
   w.finish();

libtrace/src/frame_arch.h

@@ -387,4 +387,11 @@ enum frame_architecture
   frame_arch_last
   };
 
+/**
+ * Optional per-frame information indicating execution in a specific (CPU) mode.
+ * These are the string representations of possible Bap_traces.Mode.t values.
+ */
+#define FRAME_MODE_ARM_A32 "arm:a32"
+#define FRAME_MODE_ARM_T32 "arm:t32"
+
 #endif

libtrace/src/trace.container.cpp

@@ -41,23 +41,14 @@ namespace SerializedTrace {
     return ofs;
   }
 
-
-  TraceContainerWriter::TraceContainerWriter(const std::string& filename,
-                                             frame_architecture arch,
-                                             uint64_t machine,
-                                             uint64_t frames_per_toc_entry_in)
-    : num_frames (0)
-    , frames_per_toc_entry (frames_per_toc_entry_in)
-    , ofs(open_trace(filename,arch,machine,1LL)) {}
-
   TraceContainerWriter::TraceContainerWriter(const std::string& filename,
                                              const meta_frame& meta,
                                              frame_architecture arch,
                                              uint64_t machine,
                                              uint64_t frames_per_toc_entry_in)
     : num_frames (0)
     , frames_per_toc_entry (frames_per_toc_entry_in)
-    , ofs(open_trace(filename,arch,machine,2LL)) {
+    , ofs(open_trace(filename,arch,machine,3LL)) {
     std::string meta_data;
     if (!(meta.SerializeToString(&meta_data))) {
       throw TraceException("Unable to serialize meta frame to ostream");

libtrace/src/trace.container.hpp

@@ -67,7 +67,7 @@ namespace SerializedTrace {
   const uint64_t meta_offset = 56LL;
 
   const uint64_t lowest_supported_version = 2LL;
-  const uint64_t highest_supported_version = 2LL;
+  const uint64_t highest_supported_version = 3LL;
 
 
     class TraceException: public std::exception
@@ -97,12 +97,6 @@ namespace SerializedTrace {
     /** Creates a trace container writer that will output to
         [filename]. An entry will be added to the table of contents
         every [frames_per_toc_entry] entries.*/
-    TraceContainerWriter(const std::string& filename,
-                         frame_architecture arch = default_arch,
-                         uint64_t machine = default_machine,
-                         uint64_t frames_per_toc_entry = default_frames_per_toc_entry);
-
-    // creates a container for the second version of a protocol.
     TraceContainerWriter(const std::string& filename,
                          const meta_frame& meta,
                          frame_architecture arch = default_arch,

piqi/stdframe.piqi

@@ -39,4 +39,12 @@
                .code 5
                .optional
         ]
+
+        % Per-frame (CPU) mode, for example for indicating thumb mode in Arm
+        .field [
+               .name mode
+               .type string
+               .code 6
+               .optional
+        ]
 ]