[lldb] Implement basic support for reverse-continue (#112079)

This commit adds support for a
`SBProcess::ContinueInDirection()` API. A user-accessible command for
this will follow in a later commit.

This feature depends on a gdbserver implementation (e.g. `rr`) providing
support for the `bc` and `bs` packets. `lldb-server` does not support
those packets, and there is no plan to change that. For testing
purposes, this commit adds a Python implementation of *very limited*
record-and-reverse-execute functionality, implemented as a proxy between
lldb and lldb-server in `lldbreverse.py`. This should not (and in
practice cannot) be used for anything except testing.

The tests here are quite minimal but we test that simple breakpoints and
watchpoints work as expected during reverse execution, and that
conditional breakpoints and watchpoints work when the condition calls a
function that must be executed in the forward direction.

1 files changed, 7 insertions, 2 deletions

diff --git a/lldb/source/Plugins/Process/scripted/ScriptedProcess.cpp b/lldb/source/Plugins/Process/scripted/ScriptedProcess.cpp
index d2111ce..3360bd9 100644
--- a/lldb/source/Plugins/Process/scripted/ScriptedProcess.cpp
+++ b/lldb/source/Plugins/Process/scripted/ScriptedProcess.cpp
@@ -182,10 +182,15 @@ void ScriptedProcess::DidResume() {
   m_pid = GetInterface().GetProcessID();
 }
 
-Status ScriptedProcess::DoResume() {
+Status ScriptedProcess::DoResume(RunDirection direction) {
   LLDB_LOGF(GetLog(LLDBLog::Process), "ScriptedProcess::%s resuming process", __FUNCTION__);
 
-  return GetInterface().Resume();
+  if (direction == RunDirection::eRunForward)
+    return GetInterface().Resume();
+  // FIXME: Pipe reverse continue through Scripted Processes
+  return Status::FromErrorStringWithFormatv(
+      "error: {0} does not support reverse execution of processes",
+      GetPluginName());
 }
 
 Status ScriptedProcess::DoAttach(const ProcessAttachInfo &attach_info) {