[lldb] Use Socket::CreatePair for launching debugserver

This lets get rid of platform-specific code in ProcessGDBRemote and use the
same code path (module differences in socket types) everywhere. It also unlocks
further cleanups in the debugserver launching code.

Author: labath

lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp

@@ -3447,115 +3447,80 @@ ProcessGDBRemote::EstablishConnectionIfNeeded(const ProcessInfo &process_info) {
   }
   return error;
 }
-#if !defined(_WIN32)
-#define USE_SOCKETPAIR_FOR_LOCAL_CONNECTION 1
-#endif
-
-#ifdef USE_SOCKETPAIR_FOR_LOCAL_CONNECTION
-static bool SetCloexecFlag(int fd) {
-#if defined(FD_CLOEXEC)
-  int flags = ::fcntl(fd, F_GETFD);
-  if (flags == -1)
-    return false;
-  return (::fcntl(fd, F_SETFD, flags | FD_CLOEXEC) == 0);
-#else
-  return false;
-#endif
-}
-#endif
 
 Status ProcessGDBRemote::LaunchAndConnectToDebugserver(
     const ProcessInfo &process_info) {
   using namespace std::placeholders; // For _1, _2, etc.
 
-  Status error;
-  if (m_debugserver_pid == LLDB_INVALID_PROCESS_ID) {
-    // If we locate debugserver, keep that located version around
-    static FileSpec g_debugserver_file_spec;
+  if (m_debugserver_pid != LLDB_INVALID_PROCESS_ID)
+    return Status();
 
-    ProcessLaunchInfo debugserver_launch_info;
-    // Make debugserver run in its own session so signals generated by special
-    // terminal key sequences (^C) don't affect debugserver.
-    debugserver_launch_info.SetLaunchInSeparateProcessGroup(true);
+  ProcessLaunchInfo debugserver_launch_info;
+  // Make debugserver run in its own session so signals generated by special
+  // terminal key sequences (^C) don't affect debugserver.
+  debugserver_launch_info.SetLaunchInSeparateProcessGroup(true);
 
-    const std::weak_ptr<ProcessGDBRemote> this_wp =
-        std::static_pointer_cast<ProcessGDBRemote>(shared_from_this());
-    debugserver_launch_info.SetMonitorProcessCallback(
-        std::bind(MonitorDebugserverProcess, this_wp, _1, _2, _3));
-    debugserver_launch_info.SetUserID(process_info.GetUserID());
+  const std::weak_ptr<ProcessGDBRemote> this_wp =
+      std::static_pointer_cast<ProcessGDBRemote>(shared_from_this());
+  debugserver_launch_info.SetMonitorProcessCallback(
+      std::bind(MonitorDebugserverProcess, this_wp, _1, _2, _3));
+  debugserver_launch_info.SetUserID(process_info.GetUserID());
 
 #if defined(__APPLE__)
-    // On macOS 11, we need to support x86_64 applications translated to
-    // arm64. We check whether a binary is translated and spawn the correct
-    // debugserver accordingly.
-    int mib[] = { CTL_KERN, KERN_PROC, KERN_PROC_PID,
-                  static_cast<int>(process_info.GetProcessID()) };
-    struct kinfo_proc processInfo;
-    size_t bufsize = sizeof(processInfo);
-    if (sysctl(mib, (unsigned)(sizeof(mib)/sizeof(int)), &processInfo,
-               &bufsize, NULL, 0) == 0 && bufsize > 0) {
-      if (processInfo.kp_proc.p_flag & P_TRANSLATED) {
-        FileSpec rosetta_debugserver("/Library/Apple/usr/libexec/oah/debugserver");
-        debugserver_launch_info.SetExecutableFile(rosetta_debugserver, false);
-      }
+  // On macOS 11, we need to support x86_64 applications translated to
+  // arm64. We check whether a binary is translated and spawn the correct
+  // debugserver accordingly.
+  int mib[] = {CTL_KERN, KERN_PROC, KERN_PROC_PID,
+               static_cast<int>(process_info.GetProcessID())};
+  struct kinfo_proc processInfo;
+  size_t bufsize = sizeof(processInfo);
+  if (sysctl(mib, (unsigned)(sizeof(mib) / sizeof(int)), &processInfo, &bufsize,
+             NULL, 0) == 0 &&
+      bufsize > 0) {
+    if (processInfo.kp_proc.p_flag & P_TRANSLATED) {
+      FileSpec rosetta_debugserver(
+          "/Library/Apple/usr/libexec/oah/debugserver");
+      debugserver_launch_info.SetExecutableFile(rosetta_debugserver, false);
     }
+  }
 #endif
 
-    shared_fd_t communication_fd = SharedSocket::kInvalidFD;
-#ifdef USE_SOCKETPAIR_FOR_LOCAL_CONNECTION
-    // Use a socketpair on non-Windows systems for security and performance
-    // reasons.
-    int sockets[2]; /* the pair of socket descriptors */
-    if (socketpair(AF_UNIX, SOCK_STREAM, 0, sockets) == -1) {
-      error = Status::FromErrno();
-      return error;
-    }
+  llvm::Expected<Socket::Pair> socket_pair = Socket::CreatePair();
+  if (!socket_pair)
+    return Status::FromError(socket_pair.takeError());
 
-    int our_socket = sockets[0];
-    int gdb_socket = sockets[1];
-    auto cleanup_our = llvm::make_scope_exit([&]() { close(our_socket); });
-    auto cleanup_gdb = llvm::make_scope_exit([&]() { close(gdb_socket); });
+  Status error;
+  SharedSocket shared_socket(socket_pair->first.get(), error);
+  if (error.Fail())
+    return error;
 
-    // Don't let any child processes inherit our communication socket
-    SetCloexecFlag(our_socket);
-    communication_fd = gdb_socket;
-#endif
+  error = m_gdb_comm.StartDebugserverProcess(
+      nullptr, GetTarget().GetPlatform().get(), debugserver_launch_info,
+      nullptr, nullptr, shared_socket.GetSendableFD());
 
-    error = m_gdb_comm.StartDebugserverProcess(
-        nullptr, GetTarget().GetPlatform().get(), debugserver_launch_info,
-        nullptr, nullptr, communication_fd);
+  if (error.Fail()) {
+    Log *log = GetLog(GDBRLog::Process);
 
-    if (error.Success())
-      m_debugserver_pid = debugserver_launch_info.GetProcessID();
-    else
-      m_debugserver_pid = LLDB_INVALID_PROCESS_ID;
-
-    if (m_debugserver_pid != LLDB_INVALID_PROCESS_ID) {
-#ifdef USE_SOCKETPAIR_FOR_LOCAL_CONNECTION
-      // Our process spawned correctly, we can now set our connection to use
-      // our end of the socket pair
-      cleanup_our.release();
-      m_gdb_comm.SetConnection(
-          std::make_unique<ConnectionFileDescriptor>(our_socket, true));
-#endif
-      StartAsyncThread();
-    }
+    LLDB_LOGF(log, "failed to start debugserver process: %s",
+              error.AsCString());
+    return error;
+  }
 
-    if (error.Fail()) {
-      Log *log = GetLog(GDBRLog::Process);
+  m_debugserver_pid = debugserver_launch_info.GetProcessID();
+  shared_socket.CompleteSending(m_debugserver_pid);
 
-      LLDB_LOGF(log, "failed to start debugserver process: %s",
-                error.AsCString());
-      return error;
-    }
+  // Our process spawned correctly, we can now set our connection to use
+  // our end of the socket pair
+  m_gdb_comm.SetConnection(std::make_unique<ConnectionFileDescriptor>(
+      socket_pair->second.release()));
+  StartAsyncThread();
 
-    if (m_gdb_comm.IsConnected()) {
-      // Finish the connection process by doing the handshake without
-      // connecting (send NULL URL)
-      error = ConnectToDebugserver("");
-    } else {
-      error = Status::FromErrorString("connection failed");
-    }
+  if (m_gdb_comm.IsConnected()) {
+    // Finish the connection process by doing the handshake without
+    // connecting (send NULL URL)
+    error = ConnectToDebugserver("");
+  } else {
+    error = Status::FromErrorString("connection failed");
   }
   return error;
 }