1 files changed, 176 insertions, 0 deletions
diff --git a/lldb/tools/lldb-mcp/lldb-mcp.cpp b/lldb/tools/lldb-mcp/lldb-mcp.cpp
new file mode 100644
index 000000000000..12545dcf3a3c
--- /dev/null
+++ b/lldb/tools/lldb-mcp/lldb-mcp.cpp
@@ -0,0 +1,176 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "lldb/Host/Config.h"
+#include "lldb/Host/File.h"
+#include "lldb/Host/MainLoop.h"
+#include "lldb/Host/MainLoopBase.h"
+#include "lldb/Host/Socket.h"
+#include "lldb/Initialization/SystemInitializerCommon.h"
+#include "lldb/Initialization/SystemLifetimeManager.h"
+#include "lldb/Protocol/MCP/Server.h"
+#include "lldb/Utility/Status.h"
+#include "lldb/Utility/UriParser.h"
+#include "lldb/lldb-forward.h"
+#include "llvm/ADT/ScopeExit.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/Error.h"
+#include "llvm/Support/InitLLVM.h"
+#include "llvm/Support/ManagedStatic.h"
+#include "llvm/Support/Signals.h"
+#include "llvm/Support/WithColor.h"
+#include <cstdlib>
+#include <memory>
+
+#if defined(_WIN32)
+#include <fcntl.h>
+#endif
+
+using namespace llvm;
+using namespace lldb;
+using namespace lldb_protocol::mcp;
+
+using lldb_private::File;
+using lldb_private::MainLoop;
+using lldb_private::MainLoopBase;
+using lldb_private::NativeFile;
+
+namespace {
+
+inline void exitWithError(llvm::Error Err, StringRef Prefix = "") {
+  handleAllErrors(std::move(Err), [&](ErrorInfoBase &Info) {
+    WithColor::error(errs(), Prefix) << Info.message() << '\n';
+  });
+  std::exit(EXIT_FAILURE);
+}
+
+constexpr size_t kForwardIOBufferSize = 1024;
+
+void forwardIO(lldb_private::MainLoopBase &loop, lldb::IOObjectSP &from,
+               lldb::IOObjectSP &to) {
+  char buf[kForwardIOBufferSize];
+  size_t num_bytes = sizeof(buf);
+
+  if (llvm::Error err = from->Read(buf, num_bytes).takeError())
+    exitWithError(std::move(err));
+
+  // EOF reached.
+  if (num_bytes == 0)
+    return loop.RequestTermination();
+
+  if (llvm::Error err = to->Write(buf, num_bytes).takeError())
+    exitWithError(std::move(err));
+}
+
+void connectAndForwardIO(lldb_private::MainLoop &loop, ServerInfo &info,
+                         IOObjectSP &input_sp, IOObjectSP &output_sp) {
+  auto uri = lldb_private::URI::Parse(info.connection_uri);
+  if (!uri)
+    exitWithError(createStringError("invalid connection_uri"));
+
+  std::optional<lldb_private::Socket::ProtocolModePair> protocol_and_mode =
+      lldb_private::Socket::GetProtocolAndMode(uri->scheme);
+
+  lldb_private::Status status;
+  std::unique_ptr<lldb_private::Socket> sock =
+      lldb_private::Socket::Create(protocol_and_mode->first, status);
+
+  if (status.Fail())
+    exitWithError(status.takeError());
+
+  if (uri->port && !uri->hostname.empty())
+    status = sock->Connect(
+        llvm::formatv("[{0}]:{1}", uri->hostname, *uri->port).str());
+  else
+    status = sock->Connect(uri->path);
+  if (status.Fail())
+    exitWithError(status.takeError());
+
+  IOObjectSP sock_sp = std::move(sock);
+  auto input_handle = loop.RegisterReadObject(
+      input_sp, std::bind(forwardIO, std::placeholders::_1, input_sp, sock_sp),
+      status);
+  if (status.Fail())
+    exitWithError(status.takeError());
+
+  auto socket_handle = loop.RegisterReadObject(
+      sock_sp, std::bind(forwardIO, std::placeholders::_1, sock_sp, output_sp),
+      status);
+  if (status.Fail())
+    exitWithError(status.takeError());
+
+  status = loop.Run();
+  if (status.Fail())
+    exitWithError(status.takeError());
+}
+
+llvm::ManagedStatic<lldb_private::SystemLifetimeManager> g_debugger_lifetime;
+
+} // namespace
+
+int main(int argc, char *argv[]) {
+  llvm::InitLLVM IL(argc, argv, /*InstallPipeSignalExitHandler=*/false);
+#if !defined(__APPLE__)
+  llvm::setBugReportMsg("PLEASE submit a bug report to " LLDB_BUG_REPORT_URL
+                        " and include the crash backtrace.\n");
+#else
+  llvm::setBugReportMsg("PLEASE submit a bug report to " LLDB_BUG_REPORT_URL
+                        " and include the crash report from "
+                        "~/Library/Logs/DiagnosticReports/.\n");
+#endif
+
+#if defined(_WIN32)
+  // Windows opens stdout and stdin in text mode which converts \n to 13,10
+  // while the value is just 10 on Darwin/Linux. Setting the file mode to
+  // binary fixes this.
+  int result = _setmode(fileno(stdout), _O_BINARY);
+  assert(result);
+  result = _setmode(fileno(stdin), _O_BINARY);
+  UNUSED_IF_ASSERT_DISABLED(result);
+  assert(result);
+#endif
+
+  if (llvm::Error err = g_debugger_lifetime->Initialize(
+          std::make_unique<lldb_private::SystemInitializerCommon>(nullptr)))
+    exitWithError(std::move(err));
+
+  auto cleanup = make_scope_exit([] { g_debugger_lifetime->Terminate(); });
+
+  IOObjectSP input_sp = std::make_shared<NativeFile>(
+      fileno(stdin), File::eOpenOptionReadOnly, NativeFile::Unowned);
+
+  IOObjectSP output_sp = std::make_shared<NativeFile>(
+      fileno(stdout), File::eOpenOptionWriteOnly, NativeFile::Unowned);
+
+  static MainLoop loop;
+
+  sys::SetInterruptFunction([]() {
+    loop.AddPendingCallback(
+        [](MainLoopBase &loop) { loop.RequestTermination(); });
+  });
+
+  auto existing_servers = ServerInfo::Load();
+
+  if (!existing_servers)
+    exitWithError(existing_servers.takeError());
+
+  // FIXME: Launch `lldb -o 'protocol start MCP'`.
+  if (existing_servers->empty())
+    exitWithError(createStringError("No MCP servers running"));
+
+  // FIXME: Support selecting a specific server.
+  if (existing_servers->size() != 1)
+    exitWithError(
+        createStringError("To many MCP servers running, picking a specific "
+                          "one is not yet implemented."));
+
+  ServerInfo &info = existing_servers->front();
+  connectAndForwardIO(loop, info, input_sp, output_sp);
+
+  return EXIT_SUCCESS;
+}