[intel-pt][trace] Implement a "get supported trace type" packet

Depends on D89283.

The goal of this packet (jTraceGetSupportedType) is to be able to query the gdb-server for the tracing technology that can work for the current debuggeer, which can make the user experience simpler but allowing the user to simply type

  thread trace start

to start tracing the current thread without even telling the debugger to use "intel-pt", for example. Similarly, `thread trace start [args...]` would accept args beloging to the working trace type.

Also, if the user typed

  help thread trace start

We could directly show the help information of the trace type that is supported for the target, or mention instead that no tracing is supported, if that's the case.

I added some simple tests, besides, when I ran this on my machine with intel-pt support, I got

  $ process plugin packet send "jTraceSupportedType"
    packet: jTraceSupportedType
  response: {"description":"Intel Processor Trace","pluginName":"intel-pt"}

On a machine without intel-pt support, I got

  $ process plugin packet send "jTraceSupportedType"
    packet: jTraceSupportedType
  response: E00;

Reviewed By: clayborg, labath

Differential Revision: https://reviews.llvm.org/D90490

1 files changed, 2 insertions, 0 deletions

diff --git a/lldb/source/Utility/StringExtractorGDBRemote.cpp b/lldb/source/Utility/StringExtractorGDBRemote.cpp
index 2901500..def0968 100644
--- a/lldb/source/Utility/StringExtractorGDBRemote.cpp
+++ b/lldb/source/Utility/StringExtractorGDBRemote.cpp
@@ -310,6 +310,8 @@ StringExtractorGDBRemote::GetServerPacketType() const {
       return eServerPacketType_jTraceStart;
     if (PACKET_STARTS_WITH("jTraceStop:"))
       return eServerPacketType_jTraceStop;
+    if (PACKET_MATCHES("jLLDBTraceSupportedType"))
+      return eServerPacketType_jLLDBTraceSupportedType;
     break;
 
   case 'v':