[trace][intel-pt] Implement trace start and trace stop

This implements the interactive trace start and stop methods.

This diff ended up being much larger than I anticipated because, by doing it, I found that I had implemented in the beginning many things in a non optimal way. In any case, the code is much better now.

There's a lot of boilerplate code due to the gdb-remote protocol, but the main changes are:

- New tracing packets: jLLDBTraceStop, jLLDBTraceStart, jLLDBTraceGetBinaryData. The gdb-remote packet definitions are quite comprehensive.
- Implementation of the "process trace start|stop" and "thread trace start|stop" commands.
- Implementaiton of an API in Trace.h to interact with live traces.
- Created an IntelPTDecoder for live threads, that use the debugger's stop id as checkpoint for its internal cache.
- Added a functionality to stop the process in case "process tracing" is enabled and a new thread can't traced.
- Added tests

I have some ideas to unify the code paths for post mortem and live threads, but I'll do that in another diff.

Differential Revision: https://reviews.llvm.org/D91679

1 files changed, 20 insertions, 0 deletions

diff --git a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServer.cpp b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServer.cpp
index 60548ef..2996717 100644
--- a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServer.cpp
+++ b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServer.cpp
@@ -16,11 +16,13 @@
 #include "lldb/Utility/StreamString.h"
 #include "lldb/Utility/StringExtractorGDBRemote.h"
 #include "lldb/Utility/UnimplementedError.h"
+#include "llvm/Support/JSON.h"
 #include <cstring>
 
 using namespace lldb;
 using namespace lldb_private;
 using namespace lldb_private::process_gdb_remote;
+using namespace llvm;
 
 GDBRemoteCommunicationServer::GDBRemoteCommunicationServer(
     const char *comm_name, const char *listener_name)
@@ -151,3 +153,21 @@ GDBRemoteCommunicationServer::SendOKResponse() {
 bool GDBRemoteCommunicationServer::HandshakeWithClient() {
   return GetAck() == PacketResult::Success;
 }
+
+GDBRemoteCommunication::PacketResult
+GDBRemoteCommunicationServer::SendJSONResponse(const json::Value &value) {
+  std::string json_string;
+  raw_string_ostream os(json_string);
+  os << value;
+  os.flush();
+  StreamGDBRemote escaped_response;
+  escaped_response.PutEscapedBytes(json_string.c_str(), json_string.size());
+  return SendPacketNoLock(escaped_response.GetString());
+}
+
+GDBRemoteCommunication::PacketResult
+GDBRemoteCommunicationServer::SendJSONResponse(Expected<json::Value> value) {
+  if (!value)
+    return SendErrorResponse(value.takeError());
+  return SendJSONResponse(*value);
+}