From f3472ad5c5f88c3425fc54f40d3d5280258d8be5 Mon Sep 17 00:00:00 2001
From: Jason Molenda <jason@molenda.com>
Date: Thu, 9 Sep 2021 17:02:42 -0700
Subject: [PATCH] Add specific error messages around gdb RSP handshake failures

Report timeout exceeded and connection lost error messages
when sending the initial handshake packet in a gdb remote
serial protocol connection, an especially fragile time.

Differential Revision: https://reviews.llvm.org/D108888
---
 .../GDBRemoteCommunicationClient.cpp          | 22 +++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp
index 6dcc73c3e43d..16a27af700c6 100644
--- a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp
+++ b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp
@@ -82,6 +82,8 @@ bool GDBRemoteCommunicationClient::HandshakeWithServer(Status *error_ptr) {
 
   // Start the read thread after we send the handshake ack since if we fail to
   // send the handshake ack, there is no reason to continue...
+  std::chrono::steady_clock::time_point start_of_handshake =
+      std::chrono::steady_clock::now();
   if (SendAck()) {
     // Wait for any responses that might have been queued up in the remote
     // GDB server and flush them all
@@ -97,8 +99,24 @@ bool GDBRemoteCommunicationClient::HandshakeWithServer(Status *error_ptr) {
     if (QueryNoAckModeSupported()) {
       return true;
     } else {
-      if (error_ptr)
-        error_ptr->SetErrorString("failed to get reply to handshake packet");
+      std::chrono::steady_clock::time_point end_of_handshake =
+          std::chrono::steady_clock::now();
+      auto handshake_timeout =
+          std::chrono::duration<double>(end_of_handshake - start_of_handshake)
+              .count();
+      if (error_ptr) {
+        if (packet_result == PacketResult::ErrorDisconnected)
+          error_ptr->SetErrorString("Connection shut down by remote side "
+                                    "while waiting for reply to initial "
+                                    "handshake packet");
+        else if (packet_result == PacketResult::ErrorReplyTimeout)
+          error_ptr->SetErrorStringWithFormat(
+              "failed to get reply to handshake packet within timeout of "
+              "%.1f seconds",
+              handshake_timeout);
+        else
+          error_ptr->SetErrorString("failed to get reply to handshake packet");
+      }
     }
   } else {
     if (error_ptr)