Remote Non-Stop Support

Summary:
 
This patch is the beginnings of support for Non-stop mode in the remote protocol. Letting a user examine stopped threads, while other threads execute freely.

Non-stop mode is enabled using the setting target.non-stop-mode, which sends a QNonStop packet when establishing the remote connection.
Changes are also made to treat the '?' stop reply packet differently in non-stop mode, according to spec https://sourceware.org/gdb/current/onlinedocs/gdb/Remote-Non_002dStop.html#Remote-Non_002dStop.
A setting for querying the remote for default thread on setup is also included.

Handling of '%' async notification packets will be added next.

Reviewers: clayborg

Subscribers: lldb-commits, ADodds, ted, deepak2427

Differential Revision: http://reviews.llvm.org/D9656

llvm-svn: 237239

lldb/include/lldb/Target/Target.h

@@ -189,6 +189,9 @@ public:
 
     void
     SetUserSpecifiedTrapHandlerNames (const Args &args);
+
+    bool
+    GetNonStopModeEnabled () const;
     
     bool
     GetDisplayRuntimeSupportValues () const;

lldb/source/Commands/CommandObjectThread.cpp

@@ -433,6 +433,12 @@ public:
             m_step_in_avoid_no_debug = eLazyBoolCalculate;
             m_step_out_avoid_no_debug = eLazyBoolCalculate;
             m_run_mode = eOnlyDuringStepping;
+
+            // Check if we are in Non-Stop mode
+            lldb::TargetSP target_sp = m_interpreter.GetDebugger().GetSelectedTarget();
+            if (target_sp.get() != nullptr && target_sp->GetNonStopModeEnabled())
+                m_run_mode = eOnlyThisThread;
+
             m_avoid_regexp.clear();
             m_step_in_target.clear();
             m_class_name.clear();

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

@@ -424,6 +424,7 @@ GDBRemoteCommunication::CheckForPacket (const uint8_t *src, size_t src_len, Stri
                 content_length = total_length = 1;  // The command is one byte long...
                 break;
 
+            case '%': // Async notify packet
             case '$':
                 // Look for a standard gdb packet?
                 {
@@ -466,6 +467,7 @@ GDBRemoteCommunication::CheckForPacket (const uint8_t *src, size_t src_len, Stri
                         case '+':
                         case '-':
                         case '\x03':
+                        case '%':
                         case '$':
                             done = true;
                             break;
@@ -586,7 +588,7 @@ GDBRemoteCommunication::CheckForPacket (const uint8_t *src, size_t src_len, Stri
                 }
             }
 
-            if (m_bytes[0] == '$')
+            if (m_bytes[0] == '$' || m_bytes[0] == '%')
             {
                 assert (checksum_idx < m_bytes.size());
                 if (::isxdigit (m_bytes[checksum_idx+0]) || 

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

@@ -1620,6 +1620,22 @@ GDBRemoteCommunicationClient::GetGDBServerProgramVersion()
     return 0;
 }
 
+bool
+GDBRemoteCommunicationClient::GetDefaultThreadId (lldb::tid_t &tid)
+{
+    StringExtractorGDBRemote response;
+    if (SendPacketAndWaitForResponse("qC",response,false) !=  PacketResult::Success)
+        return false;
+
+    if (!response.IsNormalResponse())
+        return false;
+
+    if (response.GetChar() == 'Q' && response.GetChar() == 'C')
+        tid = response.GetHexMaxU32(true, -1);
+
+    return true;
+}
+
 bool
 GDBRemoteCommunicationClient::GetHostInfo (bool force)
 {
@@ -2759,6 +2775,25 @@ GDBRemoteCommunicationClient::GetGroupName (uint32_t gid, std::string &name)
     return false;
 }
 
+bool
+GDBRemoteCommunicationClient::SetNonStopMode (const bool enable)
+{
+    // Form non-stop packet request
+    char packet[32];
+    const int packet_len = ::snprintf(packet, sizeof(packet), "QNonStop:%1d", (int)enable);
+    assert(packet_len < (int)sizeof(packet));
+
+    StringExtractorGDBRemote response;
+    // Send to target
+    if (SendPacketAndWaitForResponse(packet, packet_len, response, false) == PacketResult::Success)
+        if (response.IsOKResponse())
+            return true;
+
+    // Failed or not supported
+    return false;
+
+}
+
 void
 GDBRemoteCommunicationClient::TestPacketSpeed (const uint32_t num_packets)
 {

lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.h

@@ -318,6 +318,9 @@ public:
 
     bool
     GetHostInfo (bool force = false);
+
+    bool
+    GetDefaultThreadId (lldb::tid_t &tid);
     
     bool
     GetOSVersion (uint32_t &major, 
@@ -393,6 +396,9 @@ public:
                                 lldb::addr_t addr,        // Address of breakpoint or watchpoint
                                 uint32_t length);         // Byte Size of breakpoint or watchpoint
 
+    bool
+    SetNonStopMode (const bool enable);
+
     void
     TestPacketSpeed (const uint32_t num_packets);
 

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

@@ -391,7 +391,8 @@ ProcessGDBRemote::ProcessGDBRemote(Target& target, Listener &listener) :
     m_waiting_for_attach (false),
     m_destroy_tried_resuming (false),
     m_command_sp (),
-    m_breakpoint_pc_offset (0)
+    m_breakpoint_pc_offset (0),
+    m_initial_tid (LLDB_INVALID_THREAD_ID)
 {
     m_async_broadcaster.SetEventName (eBroadcastBitAsyncThreadShouldExit,   "async thread should exit");
     m_async_broadcaster.SetEventName (eBroadcastBitAsyncContinue,           "async thread continue");
@@ -769,8 +770,13 @@ ProcessGDBRemote::DoConnectRemote (Stream *strm, const char *remote_url)
         // We have a valid process
         SetID (pid);
         GetThreadList();
-        if (m_gdb_comm.SendPacketAndWaitForResponse("?", 1, m_last_stop_packet, false) == GDBRemoteCommunication::PacketResult::Success)
+        if (m_gdb_comm.GetStopReply(m_last_stop_packet))
         {
+
+            // '?' Packets must be handled differently in non-stop mode
+            if (GetTarget().GetNonStopModeEnabled())
+                HandleStopReplySequence();
+
             if (!m_target.GetArchitecture().IsValid()) 
             {
                 if (m_gdb_comm.GetProcessArchitecture().IsValid())
@@ -1052,8 +1058,13 @@ ProcessGDBRemote::DoLaunch (Module *exe_module, ProcessLaunchInfo &launch_info)
                 return error;
             }
 
-            if (m_gdb_comm.SendPacketAndWaitForResponse("?", 1, m_last_stop_packet, false) == GDBRemoteCommunication::PacketResult::Success)
+            if (m_gdb_comm.GetStopReply(m_last_stop_packet))
             {
+
+                // '?' Packets must be handled differently in non-stop mode
+                if (GetTarget().GetNonStopModeEnabled())
+                    HandleStopReplySequence();
+
                 const ArchSpec &process_arch = m_gdb_comm.GetProcessArchitecture();
 
                 if (process_arch.IsValid())
@@ -1153,12 +1164,22 @@ ProcessGDBRemote::ConnectToDebugserver (const char *connect_url)
             error.SetErrorString("not connected to remote gdb server");
         return error;
     }
+
+    // Send $QNonStop:1 packet on startup if required
+    if (GetTarget().GetNonStopModeEnabled())
+        m_gdb_comm.SetNonStopMode(true);
+
     m_gdb_comm.GetThreadSuffixSupported ();
     m_gdb_comm.GetListThreadsInStopReplySupported ();
     m_gdb_comm.GetHostInfo ();
     m_gdb_comm.GetVContSupported ('c');
     m_gdb_comm.GetVAttachOrWaitSupported();
-    
+
+    // Ask the remote server for the default thread id
+    if (GetTarget().GetNonStopModeEnabled())
+        m_gdb_comm.GetDefaultThreadId(m_initial_tid);
+
+
     size_t num_cmds = GetExtraStartupCommands().GetArgumentCount();
     for (size_t idx = 0; idx < num_cmds; idx++)
     {
@@ -1430,11 +1451,12 @@ ProcessGDBRemote::DoResume ()
         bool continue_packet_error = false;
         if (m_gdb_comm.HasAnyVContSupport ())
         {
-            if (m_continue_c_tids.size() == num_threads ||
+            if (!GetTarget().GetNonStopModeEnabled() &&
+                (m_continue_c_tids.size() == num_threads ||
                 (m_continue_c_tids.empty() &&
                  m_continue_C_tids.empty() &&
                  m_continue_s_tids.empty() &&
-                 m_continue_S_tids.empty()))
+                 m_continue_S_tids.empty())))
             {
                 // All threads are continuing, just send a "c" packet
                 continue_packet.PutCString ("c");
@@ -1661,6 +1683,27 @@ ProcessGDBRemote::DoResume ()
     return error;
 }
 
+void
+ProcessGDBRemote::HandleStopReplySequence ()
+{
+    while(true)
+    {
+        // Send vStopped
+        StringExtractorGDBRemote response;
+        m_gdb_comm.SendPacketAndWaitForResponse("vStopped", response, false);
+
+        // OK represents end of signal list
+        if (response.IsOKResponse())
+            break;
+
+        // If not OK or a normal packet we have a problem
+        if (!response.IsNormalResponse())
+            break;
+
+        SetLastStopPacket(response);
+    }
+}
+
 void
 ProcessGDBRemote::ClearThreadIDList ()
 {
@@ -2095,6 +2138,13 @@ ProcessGDBRemote::RefreshStateAfterStop ()
         UpdateThreadIDList();
     }
 
+    // If we have queried for a default thread id
+    if (m_initial_tid != LLDB_INVALID_THREAD_ID)
+    {
+        m_thread_list.SetSelectedThreadByID(m_initial_tid);
+        m_initial_tid = LLDB_INVALID_THREAD_ID;
+    }
+
     // Let all threads recover from stopping and do any clean up based
     // on the previous thread state (if any).
     m_thread_list_real.RefreshStateAfterStop();

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

@@ -358,6 +358,7 @@ protected:
     bool m_destroy_tried_resuming;
     lldb::CommandObjectSP m_command_sp;
     int64_t m_breakpoint_pc_offset;
+    lldb::tid_t m_initial_tid; // The inital thread ID, given by stub on attach
 
     bool
     StartAsyncThread ();
@@ -378,6 +379,9 @@ protected:
     lldb::StateType
     SetThreadStopInfo (StringExtractor& stop_packet);
 
+    void
+    HandleStopReplySequence ();
+
     void
     ClearThreadIDList ();
 

lldb/source/Target/Target.cpp

@@ -2978,6 +2978,7 @@ g_properties[] =
     { "display-expression-in-crashlogs"    , OptionValue::eTypeBoolean   , false, false,                      NULL, NULL, "Expressions that crash will show up in crash logs if the host system supports executable specific crash log strings and this setting is set to true." },
     { "trap-handler-names"                 , OptionValue::eTypeArray     , true,  OptionValue::eTypeString,   NULL, NULL, "A list of trap handler function names, e.g. a common Unix user process one is _sigtramp." },
     { "display-runtime-support-values"     , OptionValue::eTypeBoolean   , false, false,                      NULL, NULL, "If true, LLDB will show variables that are meant to support the operation of a language's runtime support." },
+    { "non-stop-mode"                      , OptionValue::eTypeBoolean   , false, 0,                          NULL, NULL, "Disable lock-step debugging, instead control threads independently." },
     { NULL                                 , OptionValue::eTypeInvalid   , false, 0                         , NULL, NULL, NULL }
 };
 
@@ -3016,7 +3017,8 @@ enum
     ePropertyMemoryModuleLoadLevel,
     ePropertyDisplayExpressionsInCrashlogs,
     ePropertyTrapHandlerNames,
-    ePropertyDisplayRuntimeSupportValues
+    ePropertyDisplayRuntimeSupportValues,
+    ePropertyNonStopModeEnabled
 };
 
 
@@ -3515,6 +3517,13 @@ TargetProperties::SetDisplayRuntimeSupportValues (bool b)
     m_collection_sp->SetPropertyAtIndexAsBoolean (NULL, idx, b);
 }
 
+bool
+TargetProperties::GetNonStopModeEnabled () const
+{
+    const uint32_t idx = ePropertyNonStopModeEnabled;
+    return m_collection_sp->GetPropertyAtIndexAsBoolean (NULL, idx, false);
+}
+
 const ProcessLaunchInfo &
 TargetProperties::GetProcessLaunchInfo ()
 {

lldb/source/Utility/StringExtractorGDBRemote.cpp

@@ -64,6 +64,10 @@ StringExtractorGDBRemote::GetServerPacketType () const
     const char *packet_cstr = m_packet.c_str();
     switch (m_packet[0])
     {
+
+    case '%':
+        return eServerPacketType_notify;
+
     case '\x03':
         if (packet_size == 1) return eServerPacketType_interrupt;
         break;

lldb/source/Utility/StringExtractorGDBRemote.h

@@ -145,6 +145,7 @@ public:
 
         eServerPacketType__M,
         eServerPacketType__m,
+        eServerPacketType_notify, // '%' notification
     };
     
     ServerPacketType