[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, 12 insertions, 0 deletions

diff --git a/lldb/source/Plugins/Process/Linux/NativeThreadLinux.cpp b/lldb/source/Plugins/Process/Linux/NativeThreadLinux.cpp
index 5aec98b..fcc96e2 100644
--- a/lldb/source/Plugins/Process/Linux/NativeThreadLinux.cpp
+++ b/lldb/source/Plugins/Process/Linux/NativeThreadLinux.cpp
@@ -77,6 +77,9 @@ void LogThreadStopInfo(Log &log, const ThreadStopInfo &stop_info,
   case eStopReasonInstrumentation:
     log.Printf("%s: %s instrumentation", __FUNCTION__, header);
     return;
+  case eStopReasonProcessorTrace:
+    log.Printf("%s: %s processor trace", __FUNCTION__, header);
+    return;
   default:
     log.Printf("%s: %s invalid stop reason %" PRIu32, __FUNCTION__, header,
                static_cast<uint32_t>(stop_info.reason));
@@ -398,6 +401,15 @@ void NativeThreadLinux::SetStoppedWithNoReason() {
   m_stop_info.details.signal.signo = 0;
 }
 
+void NativeThreadLinux::SetStoppedByProcessorTrace(
+    llvm::StringRef description) {
+  SetStopped();
+
+  m_stop_info.reason = StopReason::eStopReasonProcessorTrace;
+  m_stop_info.details.signal.signo = 0;
+  m_stop_description = description.str();
+}
+
 void NativeThreadLinux::SetExited() {
   const StateType new_state = StateType::eStateExited;
   MaybeLogStateChange(new_state);