xref: /llvm-project/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunication.cpp (revision 396f80a1eac514b717a4a43a313ffaadde6f7cb0)
1 //===-- GDBRemoteCommunication.cpp ------------------------------*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 
11 #include "GDBRemoteCommunication.h"
12 
13 // C Includes
14 #include <limits.h>
15 #include <string.h>
16 #include <sys/stat.h>
17 
18 // C++ Includes
19 // Other libraries and framework includes
20 #include "lldb/Core/Log.h"
21 #include "lldb/Core/StreamFile.h"
22 #include "lldb/Core/StreamString.h"
23 #include "lldb/Host/ConnectionFileDescriptor.h"
24 #include "lldb/Host/FileSpec.h"
25 #include "lldb/Host/FileSystem.h"
26 #include "lldb/Host/Host.h"
27 #include "lldb/Host/HostInfo.h"
28 #include "lldb/Host/Socket.h"
29 #include "lldb/Host/ThreadLauncher.h"
30 #include "lldb/Host/TimeValue.h"
31 #include "lldb/Target/Process.h"
32 
33 // Project includes
34 #include "ProcessGDBRemoteLog.h"
35 
36 #if defined(__APPLE__)
37 # define DEBUGSERVER_BASENAME    "debugserver"
38 #else
39 # define DEBUGSERVER_BASENAME    "lldb-gdbserver"
40 #endif
41 
42 using namespace lldb;
43 using namespace lldb_private;
44 
45 GDBRemoteCommunication::History::History (uint32_t size) :
46     m_packets(),
47     m_curr_idx (0),
48     m_total_packet_count (0),
49     m_dumped_to_log (false)
50 {
51     m_packets.resize(size);
52 }
53 
54 GDBRemoteCommunication::History::~History ()
55 {
56 }
57 
58 void
59 GDBRemoteCommunication::History::AddPacket (char packet_char,
60                                             PacketType type,
61                                             uint32_t bytes_transmitted)
62 {
63     const size_t size = m_packets.size();
64     if (size > 0)
65     {
66         const uint32_t idx = GetNextIndex();
67         m_packets[idx].packet.assign (1, packet_char);
68         m_packets[idx].type = type;
69         m_packets[idx].bytes_transmitted = bytes_transmitted;
70         m_packets[idx].packet_idx = m_total_packet_count;
71         m_packets[idx].tid = Host::GetCurrentThreadID();
72     }
73 }
74 
75 void
76 GDBRemoteCommunication::History::AddPacket (const std::string &src,
77                                             uint32_t src_len,
78                                             PacketType type,
79                                             uint32_t bytes_transmitted)
80 {
81     const size_t size = m_packets.size();
82     if (size > 0)
83     {
84         const uint32_t idx = GetNextIndex();
85         m_packets[idx].packet.assign (src, 0, src_len);
86         m_packets[idx].type = type;
87         m_packets[idx].bytes_transmitted = bytes_transmitted;
88         m_packets[idx].packet_idx = m_total_packet_count;
89         m_packets[idx].tid = Host::GetCurrentThreadID();
90     }
91 }
92 
93 void
94 GDBRemoteCommunication::History::Dump (lldb_private::Stream &strm) const
95 {
96     const uint32_t size = GetNumPacketsInHistory ();
97     const uint32_t first_idx = GetFirstSavedPacketIndex ();
98     const uint32_t stop_idx = m_curr_idx + size;
99     for (uint32_t i = first_idx;  i < stop_idx; ++i)
100     {
101         const uint32_t idx = NormalizeIndex (i);
102         const Entry &entry = m_packets[idx];
103         if (entry.type == ePacketTypeInvalid || entry.packet.empty())
104             break;
105         strm.Printf ("history[%u] tid=0x%4.4" PRIx64 " <%4u> %s packet: %s\n",
106                      entry.packet_idx,
107                      entry.tid,
108                      entry.bytes_transmitted,
109                      (entry.type == ePacketTypeSend) ? "send" : "read",
110                      entry.packet.c_str());
111     }
112 }
113 
114 void
115 GDBRemoteCommunication::History::Dump (lldb_private::Log *log) const
116 {
117     if (log && !m_dumped_to_log)
118     {
119         m_dumped_to_log = true;
120         const uint32_t size = GetNumPacketsInHistory ();
121         const uint32_t first_idx = GetFirstSavedPacketIndex ();
122         const uint32_t stop_idx = m_curr_idx + size;
123         for (uint32_t i = first_idx;  i < stop_idx; ++i)
124         {
125             const uint32_t idx = NormalizeIndex (i);
126             const Entry &entry = m_packets[idx];
127             if (entry.type == ePacketTypeInvalid || entry.packet.empty())
128                 break;
129             log->Printf ("history[%u] tid=0x%4.4" PRIx64 " <%4u> %s packet: %s",
130                          entry.packet_idx,
131                          entry.tid,
132                          entry.bytes_transmitted,
133                          (entry.type == ePacketTypeSend) ? "send" : "read",
134                          entry.packet.c_str());
135         }
136     }
137 }
138 
139 //----------------------------------------------------------------------
140 // GDBRemoteCommunication constructor
141 //----------------------------------------------------------------------
142 GDBRemoteCommunication::GDBRemoteCommunication(const char *comm_name,
143                                                const char *listener_name,
144                                                bool is_platform) :
145     Communication(comm_name),
146 #ifdef LLDB_CONFIGURATION_DEBUG
147     m_packet_timeout (1000),
148 #else
149     m_packet_timeout (1),
150 #endif
151     m_sequence_mutex (Mutex::eMutexTypeRecursive),
152     m_public_is_running (false),
153     m_private_is_running (false),
154     m_history (512),
155     m_send_acks (true),
156     m_is_platform (is_platform),
157     m_listen_url ()
158 {
159 }
160 
161 //----------------------------------------------------------------------
162 // Destructor
163 //----------------------------------------------------------------------
164 GDBRemoteCommunication::~GDBRemoteCommunication()
165 {
166     if (IsConnected())
167     {
168         Disconnect();
169     }
170 }
171 
172 char
173 GDBRemoteCommunication::CalculcateChecksum (const char *payload, size_t payload_length)
174 {
175     int checksum = 0;
176 
177     for (size_t i = 0; i < payload_length; ++i)
178         checksum += payload[i];
179 
180     return checksum & 255;
181 }
182 
183 size_t
184 GDBRemoteCommunication::SendAck ()
185 {
186     Log *log (ProcessGDBRemoteLog::GetLogIfAllCategoriesSet (GDBR_LOG_PACKETS));
187     ConnectionStatus status = eConnectionStatusSuccess;
188     char ch = '+';
189     const size_t bytes_written = Write (&ch, 1, status, NULL);
190     if (log)
191         log->Printf ("<%4" PRIu64 "> send packet: %c", (uint64_t)bytes_written, ch);
192     m_history.AddPacket (ch, History::ePacketTypeSend, bytes_written);
193     return bytes_written;
194 }
195 
196 size_t
197 GDBRemoteCommunication::SendNack ()
198 {
199     Log *log (ProcessGDBRemoteLog::GetLogIfAllCategoriesSet (GDBR_LOG_PACKETS));
200     ConnectionStatus status = eConnectionStatusSuccess;
201     char ch = '-';
202     const size_t bytes_written = Write (&ch, 1, status, NULL);
203     if (log)
204         log->Printf("<%4" PRIu64 "> send packet: %c", (uint64_t)bytes_written, ch);
205     m_history.AddPacket (ch, History::ePacketTypeSend, bytes_written);
206     return bytes_written;
207 }
208 
209 GDBRemoteCommunication::PacketResult
210 GDBRemoteCommunication::SendPacket (const char *payload, size_t payload_length)
211 {
212     Mutex::Locker locker(m_sequence_mutex);
213     return SendPacketNoLock (payload, payload_length);
214 }
215 
216 GDBRemoteCommunication::PacketResult
217 GDBRemoteCommunication::SendPacketNoLock (const char *payload, size_t payload_length)
218 {
219     if (IsConnected())
220     {
221         StreamString packet(0, 4, eByteOrderBig);
222 
223         packet.PutChar('$');
224         packet.Write (payload, payload_length);
225         packet.PutChar('#');
226         packet.PutHex8(CalculcateChecksum (payload, payload_length));
227 
228         Log *log (ProcessGDBRemoteLog::GetLogIfAllCategoriesSet (GDBR_LOG_PACKETS));
229         ConnectionStatus status = eConnectionStatusSuccess;
230         const char *packet_data = packet.GetData();
231         const size_t packet_length = packet.GetSize();
232         size_t bytes_written = Write (packet_data, packet_length, status, NULL);
233         if (log)
234         {
235             size_t binary_start_offset = 0;
236             if (strncmp(packet_data, "$vFile:pwrite:", strlen("$vFile:pwrite:")) == 0)
237             {
238                 const char *first_comma = strchr(packet_data, ',');
239                 if (first_comma)
240                 {
241                     const char *second_comma = strchr(first_comma + 1, ',');
242                     if (second_comma)
243                         binary_start_offset = second_comma - packet_data + 1;
244                 }
245             }
246 
247             // If logging was just enabled and we have history, then dump out what
248             // we have to the log so we get the historical context. The Dump() call that
249             // logs all of the packet will set a boolean so that we don't dump this more
250             // than once
251             if (!m_history.DidDumpToLog ())
252                 m_history.Dump (log);
253 
254             if (binary_start_offset)
255             {
256                 StreamString strm;
257                 // Print non binary data header
258                 strm.Printf("<%4" PRIu64 "> send packet: %.*s", (uint64_t)bytes_written, (int)binary_start_offset, packet_data);
259                 const uint8_t *p;
260                 // Print binary data exactly as sent
261                 for (p = (uint8_t*)packet_data + binary_start_offset; *p != '#'; ++p)
262                     strm.Printf("\\x%2.2x", *p);
263                 // Print the checksum
264                 strm.Printf("%*s", (int)3, p);
265                 log->PutCString(strm.GetString().c_str());
266             }
267             else
268                 log->Printf("<%4" PRIu64 "> send packet: %.*s", (uint64_t)bytes_written, (int)packet_length, packet_data);
269         }
270 
271         m_history.AddPacket (packet.GetString(), packet_length, History::ePacketTypeSend, bytes_written);
272 
273 
274         if (bytes_written == packet_length)
275         {
276             if (GetSendAcks ())
277                 return GetAck ();
278             else
279                 return PacketResult::Success;
280         }
281         else
282         {
283             if (log)
284                 log->Printf ("error: failed to send packet: %.*s", (int)packet_length, packet_data);
285         }
286     }
287     return PacketResult::ErrorSendFailed;
288 }
289 
290 GDBRemoteCommunication::PacketResult
291 GDBRemoteCommunication::GetAck ()
292 {
293     StringExtractorGDBRemote packet;
294     PacketResult result = WaitForPacketWithTimeoutMicroSecondsNoLock (packet, GetPacketTimeoutInMicroSeconds ());
295     if (result == PacketResult::Success)
296     {
297         if (packet.GetResponseType() == StringExtractorGDBRemote::ResponseType::eAck)
298             return PacketResult::Success;
299         else
300             return PacketResult::ErrorSendAck;
301     }
302     return result;
303 }
304 
305 bool
306 GDBRemoteCommunication::GetSequenceMutex (Mutex::Locker& locker, const char *failure_message)
307 {
308     if (IsRunning())
309         return locker.TryLock (m_sequence_mutex, failure_message);
310 
311     locker.Lock (m_sequence_mutex);
312     return true;
313 }
314 
315 
316 bool
317 GDBRemoteCommunication::WaitForNotRunningPrivate (const TimeValue *timeout_ptr)
318 {
319     return m_private_is_running.WaitForValueEqualTo (false, timeout_ptr, NULL);
320 }
321 
322 GDBRemoteCommunication::PacketResult
323 GDBRemoteCommunication::WaitForPacketWithTimeoutMicroSecondsNoLock (StringExtractorGDBRemote &packet, uint32_t timeout_usec)
324 {
325     uint8_t buffer[8192];
326     Error error;
327 
328     Log *log (ProcessGDBRemoteLog::GetLogIfAllCategoriesSet (GDBR_LOG_PACKETS | GDBR_LOG_VERBOSE));
329 
330     // Check for a packet from our cache first without trying any reading...
331     if (CheckForPacket (NULL, 0, packet))
332         return PacketResult::Success;
333 
334     bool timed_out = false;
335     bool disconnected = false;
336     while (IsConnected() && !timed_out)
337     {
338         lldb::ConnectionStatus status = eConnectionStatusNoConnection;
339         size_t bytes_read = Read (buffer, sizeof(buffer), timeout_usec, status, &error);
340 
341         if (log)
342             log->Printf ("%s: Read (buffer, (sizeof(buffer), timeout_usec = 0x%x, status = %s, error = %s) => bytes_read = %" PRIu64,
343                          __PRETTY_FUNCTION__,
344                          timeout_usec,
345                          Communication::ConnectionStatusAsCString (status),
346                          error.AsCString(),
347                          (uint64_t)bytes_read);
348 
349         if (bytes_read > 0)
350         {
351             if (CheckForPacket (buffer, bytes_read, packet))
352                 return PacketResult::Success;
353         }
354         else
355         {
356             switch (status)
357             {
358             case eConnectionStatusTimedOut:
359             case eConnectionStatusInterrupted:
360                 timed_out = true;
361                 break;
362             case eConnectionStatusSuccess:
363                 //printf ("status = success but error = %s\n", error.AsCString("<invalid>"));
364                 break;
365 
366             case eConnectionStatusEndOfFile:
367             case eConnectionStatusNoConnection:
368             case eConnectionStatusLostConnection:
369             case eConnectionStatusError:
370                 disconnected = true;
371                 Disconnect();
372                 break;
373             }
374         }
375     }
376     packet.Clear ();
377     if (disconnected)
378         return PacketResult::ErrorDisconnected;
379     if (timed_out)
380         return PacketResult::ErrorReplyTimeout;
381     else
382         return PacketResult::ErrorReplyFailed;
383 }
384 
385 bool
386 GDBRemoteCommunication::CheckForPacket (const uint8_t *src, size_t src_len, StringExtractorGDBRemote &packet)
387 {
388     // Put the packet data into the buffer in a thread safe fashion
389     Mutex::Locker locker(m_bytes_mutex);
390 
391     Log *log (ProcessGDBRemoteLog::GetLogIfAllCategoriesSet (GDBR_LOG_PACKETS));
392 
393     if (src && src_len > 0)
394     {
395         if (log && log->GetVerbose())
396         {
397             StreamString s;
398             log->Printf ("GDBRemoteCommunication::%s adding %u bytes: %.*s",
399                          __FUNCTION__,
400                          (uint32_t)src_len,
401                          (uint32_t)src_len,
402                          src);
403         }
404         m_bytes.append ((const char *)src, src_len);
405     }
406 
407     // Parse up the packets into gdb remote packets
408     if (!m_bytes.empty())
409     {
410         // end_idx must be one past the last valid packet byte. Start
411         // it off with an invalid value that is the same as the current
412         // index.
413         size_t content_start = 0;
414         size_t content_length = std::string::npos;
415         size_t total_length = 0;
416         size_t checksum_idx = std::string::npos;
417 
418         while (!m_bytes.empty() && content_length == std::string::npos)
419         {
420             switch (m_bytes[0])
421             {
422                 case '+':       // Look for ack
423                 case '-':       // Look for cancel
424                 case '\x03':    // ^C to halt target
425                     content_length = total_length = 1;  // The command is one byte long...
426                     break;
427 
428                 case '$':
429                     // Look for a standard gdb packet?
430                     {
431                         size_t hash_pos = m_bytes.find('#');
432                         if (hash_pos != std::string::npos)
433                         {
434                             if (hash_pos + 2 < m_bytes.size())
435                             {
436                                 checksum_idx = hash_pos + 1;
437                                 // Skip the dollar sign
438                                 content_start = 1;
439                                 // Don't include the # in the content or the $ in the content length
440                                 content_length = hash_pos - 1;
441 
442                                 total_length = hash_pos + 3; // Skip the # and the two hex checksum bytes
443                             }
444                             else
445                             {
446                                 // Checksum bytes aren't all here yet
447                                 content_length = std::string::npos;
448                             }
449                         }
450                     }
451                     break;
452 
453                 default:
454                     {
455                         // We have an unexpected byte and we need to flush all bad
456                         // data that is in m_bytes, so we need to find the first
457                         // byte that is a '+' (ACK), '-' (NACK), \x03 (CTRL+C interrupt),
458                         // or '$' character (start of packet header) or of course,
459                         // the end of the data in m_bytes...
460                         const size_t bytes_len = m_bytes.size();
461                         bool done = false;
462                         uint32_t idx;
463                         for (idx = 1; !done && idx < bytes_len; ++idx)
464                         {
465                             switch (m_bytes[idx])
466                             {
467                             case '+':
468                             case '-':
469                             case '\x03':
470                             case '$':
471                                 done = true;
472                                 break;
473 
474                             default:
475                                 break;
476                             }
477                         }
478                         if (log)
479                             log->Printf ("GDBRemoteCommunication::%s tossing %u junk bytes: '%.*s'",
480                                          __FUNCTION__, idx - 1, idx - 1, m_bytes.c_str());
481                         m_bytes.erase(0, idx - 1);
482                     }
483                     break;
484             }
485         }
486 
487         if (content_length == std::string::npos)
488         {
489             packet.Clear();
490             return false;
491         }
492         else if (total_length > 0)
493         {
494 
495             // We have a valid packet...
496             assert (content_length <= m_bytes.size());
497             assert (total_length <= m_bytes.size());
498             assert (content_length <= total_length);
499             const size_t content_end = content_start + content_length;
500 
501             bool success = true;
502             std::string &packet_str = packet.GetStringRef();
503 
504 
505             if (log)
506             {
507                 // If logging was just enabled and we have history, then dump out what
508                 // we have to the log so we get the historical context. The Dump() call that
509                 // logs all of the packet will set a boolean so that we don't dump this more
510                 // than once
511                 if (!m_history.DidDumpToLog ())
512                     m_history.Dump (log);
513 
514                 bool binary = false;
515                 // Only detect binary for packets that start with a '$' and have a '#CC' checksum
516                 if (m_bytes[0] == '$' && total_length > 4)
517                 {
518                     for (size_t i=0; !binary && i<total_length; ++i)
519                     {
520                         if (isprint(m_bytes[i]) == 0)
521                             binary = true;
522                     }
523                 }
524                 if (binary)
525                 {
526                     StreamString strm;
527                     // Packet header...
528                     strm.Printf("<%4" PRIu64 "> read packet: %c", (uint64_t)total_length, m_bytes[0]);
529                     for (size_t i=content_start; i<content_end; ++i)
530                     {
531                         // Remove binary escaped bytes when displaying the packet...
532                         const char ch = m_bytes[i];
533                         if (ch == 0x7d)
534                         {
535                             // 0x7d is the escape character.  The next character is to
536                             // be XOR'd with 0x20.
537                             const char escapee = m_bytes[++i] ^ 0x20;
538                             strm.Printf("%2.2x", escapee);
539                         }
540                         else
541                         {
542                             strm.Printf("%2.2x", (uint8_t)ch);
543                         }
544                     }
545                     // Packet footer...
546                     strm.Printf("%c%c%c", m_bytes[total_length-3], m_bytes[total_length-2], m_bytes[total_length-1]);
547                     log->PutCString(strm.GetString().c_str());
548                 }
549                 else
550                 {
551                     log->Printf("<%4" PRIu64 "> read packet: %.*s", (uint64_t)total_length, (int)(total_length), m_bytes.c_str());
552                 }
553             }
554 
555             m_history.AddPacket (m_bytes.c_str(), total_length, History::ePacketTypeRecv, total_length);
556 
557             // Clear packet_str in case there is some existing data in it.
558             packet_str.clear();
559             // Copy the packet from m_bytes to packet_str expanding the
560             // run-length encoding in the process.
561             // Reserve enough byte for the most common case (no RLE used)
562             packet_str.reserve(m_bytes.length());
563             for (std::string::const_iterator c = m_bytes.begin() + content_start; c != m_bytes.begin() + content_end; ++c)
564             {
565                 if (*c == '*')
566                 {
567                     // '*' indicates RLE. Next character will give us the
568                     // repeat count and previous character is what is to be
569                     // repeated.
570                     char char_to_repeat = packet_str.back();
571                     // Number of time the previous character is repeated
572                     int repeat_count = *++c + 3 - ' ';
573                     // We have the char_to_repeat and repeat_count. Now push
574                     // it in the packet.
575                     for (int i = 0; i < repeat_count; ++i)
576                         packet_str.push_back(char_to_repeat);
577                 }
578                 else if (*c == 0x7d)
579                 {
580                     // 0x7d is the escape character.  The next character is to
581                     // be XOR'd with 0x20.
582                     char escapee = *++c ^ 0x20;
583                     packet_str.push_back(escapee);
584                 }
585                 else
586                 {
587                     packet_str.push_back(*c);
588                 }
589             }
590 
591             if (m_bytes[0] == '$')
592             {
593                 assert (checksum_idx < m_bytes.size());
594                 if (::isxdigit (m_bytes[checksum_idx+0]) ||
595                     ::isxdigit (m_bytes[checksum_idx+1]))
596                 {
597                     if (GetSendAcks ())
598                     {
599                         const char *packet_checksum_cstr = &m_bytes[checksum_idx];
600                         char packet_checksum = strtol (packet_checksum_cstr, NULL, 16);
601                         char actual_checksum = CalculcateChecksum (packet_str.c_str(), packet_str.size());
602                         success = packet_checksum == actual_checksum;
603                         if (!success)
604                         {
605                             if (log)
606                                 log->Printf ("error: checksum mismatch: %.*s expected 0x%2.2x, got 0x%2.2x",
607                                              (int)(total_length),
608                                              m_bytes.c_str(),
609                                              (uint8_t)packet_checksum,
610                                              (uint8_t)actual_checksum);
611                         }
612                         // Send the ack or nack if needed
613                         if (!success)
614                             SendNack();
615                         else
616                             SendAck();
617                     }
618                 }
619                 else
620                 {
621                     success = false;
622                     if (log)
623                         log->Printf ("error: invalid checksum in packet: '%s'\n", m_bytes.c_str());
624                 }
625             }
626 
627             m_bytes.erase(0, total_length);
628             packet.SetFilePos(0);
629             return success;
630         }
631     }
632     packet.Clear();
633     return false;
634 }
635 
636 Error
637 GDBRemoteCommunication::StartListenThread (const char *hostname, uint16_t port)
638 {
639     Error error;
640     if (m_listen_thread.IsJoinable())
641     {
642         error.SetErrorString("listen thread already running");
643     }
644     else
645     {
646         char listen_url[512];
647         if (hostname && hostname[0])
648             snprintf(listen_url, sizeof(listen_url), "listen://%s:%i", hostname, port);
649         else
650             snprintf(listen_url, sizeof(listen_url), "listen://%i", port);
651         m_listen_url = listen_url;
652         SetConnection(new ConnectionFileDescriptor());
653         m_listen_thread = ThreadLauncher::LaunchThread(listen_url, GDBRemoteCommunication::ListenThread, this, &error);
654     }
655     return error;
656 }
657 
658 bool
659 GDBRemoteCommunication::JoinListenThread ()
660 {
661     if (m_listen_thread.IsJoinable())
662         m_listen_thread.Join(nullptr);
663     return true;
664 }
665 
666 lldb::thread_result_t
667 GDBRemoteCommunication::ListenThread (lldb::thread_arg_t arg)
668 {
669     GDBRemoteCommunication *comm = (GDBRemoteCommunication *)arg;
670     Error error;
671     ConnectionFileDescriptor *connection = (ConnectionFileDescriptor *)comm->GetConnection ();
672 
673     if (connection)
674     {
675         // Do the listen on another thread so we can continue on...
676         if (connection->Connect(comm->m_listen_url.c_str(), &error) != eConnectionStatusSuccess)
677             comm->SetConnection(NULL);
678     }
679     return NULL;
680 }
681 
682 Error
683 GDBRemoteCommunication::StartDebugserverProcess (const char *hostname,
684                                                  uint16_t in_port,
685                                                  lldb_private::ProcessLaunchInfo &launch_info,
686                                                  uint16_t &out_port)
687 {
688     Log *log (ProcessGDBRemoteLog::GetLogIfAllCategoriesSet (GDBR_LOG_PROCESS));
689     if (log)
690         log->Printf ("GDBRemoteCommunication::%s(hostname=%s, in_port=%" PRIu16 ", out_port=%" PRIu16, __FUNCTION__, hostname ? hostname : "<empty>", in_port, out_port);
691 
692     out_port = in_port;
693     Error error;
694     // If we locate debugserver, keep that located version around
695     static FileSpec g_debugserver_file_spec;
696 
697     char debugserver_path[PATH_MAX];
698     FileSpec &debugserver_file_spec = launch_info.GetExecutableFile();
699 
700     // Always check to see if we have an environment override for the path
701     // to the debugserver to use and use it if we do.
702     const char *env_debugserver_path = getenv("LLDB_DEBUGSERVER_PATH");
703     if (env_debugserver_path)
704     {
705         debugserver_file_spec.SetFile (env_debugserver_path, false);
706         if (log)
707             log->Printf ("GDBRemoteCommunication::%s() gdb-remote stub exe path set from environment variable: %s", __FUNCTION__, env_debugserver_path);
708     }
709     else
710         debugserver_file_spec = g_debugserver_file_spec;
711     bool debugserver_exists = debugserver_file_spec.Exists();
712     if (!debugserver_exists)
713     {
714         // The debugserver binary is in the LLDB.framework/Resources
715         // directory.
716         if (HostInfo::GetLLDBPath(ePathTypeSupportExecutableDir, debugserver_file_spec))
717         {
718             debugserver_file_spec.AppendPathComponent (DEBUGSERVER_BASENAME);
719             debugserver_exists = debugserver_file_spec.Exists();
720             if (debugserver_exists)
721             {
722                 if (log)
723                     log->Printf ("GDBRemoteCommunication::%s() found gdb-remote stub exe '%s'", __FUNCTION__, debugserver_file_spec.GetPath ().c_str ());
724 
725                 g_debugserver_file_spec = debugserver_file_spec;
726             }
727             else
728             {
729                 if (log)
730                     log->Printf ("GDBRemoteCommunication::%s() could not find gdb-remote stub exe '%s'", __FUNCTION__, debugserver_file_spec.GetPath ().c_str ());
731 
732                 g_debugserver_file_spec.Clear();
733                 debugserver_file_spec.Clear();
734             }
735         }
736     }
737 
738     if (debugserver_exists)
739     {
740         debugserver_file_spec.GetPath (debugserver_path, sizeof(debugserver_path));
741 
742         Args &debugserver_args = launch_info.GetArguments();
743         debugserver_args.Clear();
744         char arg_cstr[PATH_MAX];
745 
746         // Start args with "debugserver /file/path -r --"
747         debugserver_args.AppendArgument(debugserver_path);
748 
749         // If a host and port is supplied then use it
750         char host_and_port[128];
751         if (hostname)
752         {
753             snprintf (host_and_port, sizeof(host_and_port), "%s:%u", hostname, in_port);
754             debugserver_args.AppendArgument(host_and_port);
755         }
756         else
757         {
758             host_and_port[0] = '\0';
759         }
760 
761         // use native registers, not the GDB registers
762         debugserver_args.AppendArgument("--native-regs");
763         // make debugserver run in its own session so signals generated by
764         // special terminal key sequences (^C) don't affect debugserver
765         debugserver_args.AppendArgument("--setsid");
766 
767         char named_pipe_path[PATH_MAX];
768         named_pipe_path[0] = '\0';
769 
770         bool listen = false;
771         if (host_and_port[0])
772         {
773             // Create a temporary file to get the stdout/stderr and redirect the
774             // output of the command into this file. We will later read this file
775             // if all goes well and fill the data into "command_output_ptr"
776 
777             if (in_port == 0)
778             {
779                 // Binding to port zero, we need to figure out what port it ends up
780                 // using using a named pipe...
781                 FileSpec tmpdir_file_spec;
782                 if (HostInfo::GetLLDBPath(ePathTypeLLDBTempSystemDir, tmpdir_file_spec))
783                 {
784                     tmpdir_file_spec.AppendPathComponent("debugserver-named-pipe.XXXXXX");
785                     strncpy(named_pipe_path, tmpdir_file_spec.GetPath().c_str(), sizeof(named_pipe_path));
786                 }
787                 else
788                 {
789                     strncpy(named_pipe_path, "/tmp/debugserver-named-pipe.XXXXXX", sizeof(named_pipe_path));
790                 }
791 
792                 if (::mktemp (named_pipe_path))
793                 {
794 #if defined(_WIN32)
795                     if ( false )
796 #else
797                     if (::mkfifo(named_pipe_path, 0600) == 0)
798 #endif
799                     {
800                         debugserver_args.AppendArgument("--named-pipe");
801                         debugserver_args.AppendArgument(named_pipe_path);
802                     }
803                 }
804             }
805             else
806             {
807                 listen = true;
808             }
809         }
810         else
811         {
812             // No host and port given, so lets listen on our end and make the debugserver
813             // connect to us..
814             error = StartListenThread ("127.0.0.1", 0);
815             if (error.Fail())
816                 return error;
817 
818             ConnectionFileDescriptor *connection = (ConnectionFileDescriptor *)GetConnection ();
819             // Wait for 10 seconds to resolve the bound port
820             out_port = connection->GetListeningPort(10);
821             if (out_port > 0)
822             {
823                 char port_cstr[32];
824                 snprintf(port_cstr, sizeof(port_cstr), "127.0.0.1:%i", out_port);
825                 // Send the host and port down that debugserver and specify an option
826                 // so that it connects back to the port we are listening to in this process
827                 debugserver_args.AppendArgument("--reverse-connect");
828                 debugserver_args.AppendArgument(port_cstr);
829             }
830             else
831             {
832                 error.SetErrorString ("failed to bind to port 0 on 127.0.0.1");
833                 return error;
834             }
835         }
836 
837         const char *env_debugserver_log_file = getenv("LLDB_DEBUGSERVER_LOG_FILE");
838         if (env_debugserver_log_file)
839         {
840             ::snprintf (arg_cstr, sizeof(arg_cstr), "--log-file=%s", env_debugserver_log_file);
841             debugserver_args.AppendArgument(arg_cstr);
842         }
843 
844         const char *env_debugserver_log_flags = getenv("LLDB_DEBUGSERVER_LOG_FLAGS");
845         if (env_debugserver_log_flags)
846         {
847             ::snprintf (arg_cstr, sizeof(arg_cstr), "--log-flags=%s", env_debugserver_log_flags);
848             debugserver_args.AppendArgument(arg_cstr);
849         }
850 
851         // Add additional args, starting with LLDB_DEBUGSERVER_EXTRA_ARG_1 until an env var doesn't come back.
852         uint32_t env_var_index = 1;
853         bool has_env_var;
854         do
855         {
856             char env_var_name[64];
857             snprintf (env_var_name, sizeof (env_var_name), "LLDB_DEBUGSERVER_EXTRA_ARG_%" PRIu32, env_var_index++);
858             const char *extra_arg = getenv(env_var_name);
859             has_env_var = extra_arg != nullptr;
860 
861             if (has_env_var)
862             {
863                 debugserver_args.AppendArgument (extra_arg);
864                 if (log)
865                     log->Printf ("GDBRemoteCommunication::%s adding env var %s contents to stub command line (%s)", __FUNCTION__, env_var_name, extra_arg);
866             }
867         } while (has_env_var);
868 
869         // Close STDIN, STDOUT and STDERR. We might need to redirect them
870         // to "/dev/null" if we run into any problems.
871         launch_info.AppendCloseFileAction (STDIN_FILENO);
872         launch_info.AppendCloseFileAction (STDOUT_FILENO);
873         launch_info.AppendCloseFileAction (STDERR_FILENO);
874 
875         error = Host::LaunchProcess(launch_info);
876 
877         if (error.Success() && launch_info.GetProcessID() != LLDB_INVALID_PROCESS_ID)
878         {
879             if (named_pipe_path[0])
880             {
881                 File name_pipe_file;
882                 error = name_pipe_file.Open(named_pipe_path, File::eOpenOptionRead);
883                 if (error.Success())
884                 {
885                     char port_cstr[256];
886                     port_cstr[0] = '\0';
887                     size_t num_bytes = sizeof(port_cstr);
888                     error = name_pipe_file.Read(port_cstr, num_bytes);
889                     assert (error.Success());
890                     assert (num_bytes > 0 && port_cstr[num_bytes-1] == '\0');
891                     out_port = Args::StringToUInt32(port_cstr, 0);
892                     name_pipe_file.Close();
893                 }
894                 FileSystem::Unlink(named_pipe_path);
895             }
896             else if (listen)
897             {
898 
899             }
900             else
901             {
902                 // Make sure we actually connect with the debugserver...
903                 JoinListenThread();
904             }
905         }
906     }
907     else
908     {
909         error.SetErrorStringWithFormat ("unable to locate " DEBUGSERVER_BASENAME );
910     }
911     return error;
912 }
913 
914 void
915 GDBRemoteCommunication::DumpHistory(Stream &strm)
916 {
917     m_history.Dump (strm);
918 }
919