xref: /llvm-project/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunication.cpp (revision 1eb0d42a1b64ff7aa5d36af2df30fef929fead6f)
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/RegularExpression.h"
22 #include "lldb/Core/StreamFile.h"
23 #include "lldb/Core/StreamString.h"
24 #include "lldb/Host/ConnectionFileDescriptor.h"
25 #include "lldb/Host/FileSpec.h"
26 #include "lldb/Host/Host.h"
27 #include "lldb/Host/HostInfo.h"
28 #include "lldb/Host/Pipe.h"
29 #include "lldb/Host/Socket.h"
30 #include "lldb/Host/StringConvert.h"
31 #include "lldb/Host/ThreadLauncher.h"
32 #include "lldb/Host/TimeValue.h"
33 #include "lldb/Target/Platform.h"
34 #include "lldb/Target/Process.h"
35 #include "llvm/ADT/SmallString.h"
36 #include "llvm/Support/ScopedPrinter.h"
37 
38 // Project includes
39 #include "ProcessGDBRemoteLog.h"
40 
41 #if defined(__APPLE__)
42 # define DEBUGSERVER_BASENAME    "debugserver"
43 #else
44 # define DEBUGSERVER_BASENAME    "lldb-server"
45 #endif
46 
47 #if defined (HAVE_LIBCOMPRESSION)
48 #include <compression.h>
49 #endif
50 
51 #if defined (HAVE_LIBZ)
52 #include <zlib.h>
53 #endif
54 
55 using namespace lldb;
56 using namespace lldb_private;
57 using namespace lldb_private::process_gdb_remote;
58 
59 GDBRemoteCommunication::History::History (uint32_t size) :
60     m_packets(),
61     m_curr_idx (0),
62     m_total_packet_count (0),
63     m_dumped_to_log (false)
64 {
65     m_packets.resize(size);
66 }
67 
68 GDBRemoteCommunication::History::~History ()
69 {
70 }
71 
72 void
73 GDBRemoteCommunication::History::AddPacket (char packet_char,
74                                             PacketType type,
75                                             uint32_t bytes_transmitted)
76 {
77     const size_t size = m_packets.size();
78     if (size > 0)
79     {
80         const uint32_t idx = GetNextIndex();
81         m_packets[idx].packet.assign (1, packet_char);
82         m_packets[idx].type = type;
83         m_packets[idx].bytes_transmitted = bytes_transmitted;
84         m_packets[idx].packet_idx = m_total_packet_count;
85         m_packets[idx].tid = Host::GetCurrentThreadID();
86     }
87 }
88 
89 void
90 GDBRemoteCommunication::History::AddPacket (const std::string &src,
91                                             uint32_t src_len,
92                                             PacketType type,
93                                             uint32_t bytes_transmitted)
94 {
95     const size_t size = m_packets.size();
96     if (size > 0)
97     {
98         const uint32_t idx = GetNextIndex();
99         m_packets[idx].packet.assign (src, 0, src_len);
100         m_packets[idx].type = type;
101         m_packets[idx].bytes_transmitted = bytes_transmitted;
102         m_packets[idx].packet_idx = m_total_packet_count;
103         m_packets[idx].tid = Host::GetCurrentThreadID();
104     }
105 }
106 
107 void
108 GDBRemoteCommunication::History::Dump (Stream &strm) const
109 {
110     const uint32_t size = GetNumPacketsInHistory ();
111     const uint32_t first_idx = GetFirstSavedPacketIndex ();
112     const uint32_t stop_idx = m_curr_idx + size;
113     for (uint32_t i = first_idx;  i < stop_idx; ++i)
114     {
115         const uint32_t idx = NormalizeIndex (i);
116         const Entry &entry = m_packets[idx];
117         if (entry.type == ePacketTypeInvalid || entry.packet.empty())
118             break;
119         strm.Printf ("history[%u] tid=0x%4.4" PRIx64 " <%4u> %s packet: %s\n",
120                      entry.packet_idx,
121                      entry.tid,
122                      entry.bytes_transmitted,
123                      (entry.type == ePacketTypeSend) ? "send" : "read",
124                      entry.packet.c_str());
125     }
126 }
127 
128 void
129 GDBRemoteCommunication::History::Dump (Log *log) const
130 {
131     if (log && !m_dumped_to_log)
132     {
133         m_dumped_to_log = true;
134         const uint32_t size = GetNumPacketsInHistory ();
135         const uint32_t first_idx = GetFirstSavedPacketIndex ();
136         const uint32_t stop_idx = m_curr_idx + size;
137         for (uint32_t i = first_idx;  i < stop_idx; ++i)
138         {
139             const uint32_t idx = NormalizeIndex (i);
140             const Entry &entry = m_packets[idx];
141             if (entry.type == ePacketTypeInvalid || entry.packet.empty())
142                 break;
143             log->Printf ("history[%u] tid=0x%4.4" PRIx64 " <%4u> %s packet: %s",
144                          entry.packet_idx,
145                          entry.tid,
146                          entry.bytes_transmitted,
147                          (entry.type == ePacketTypeSend) ? "send" : "read",
148                          entry.packet.c_str());
149         }
150     }
151 }
152 
153 //----------------------------------------------------------------------
154 // GDBRemoteCommunication constructor
155 //----------------------------------------------------------------------
156 GDBRemoteCommunication::GDBRemoteCommunication(const char *comm_name, const char *listener_name)
157     : Communication(comm_name),
158 #ifdef LLDB_CONFIGURATION_DEBUG
159       m_packet_timeout(1000),
160 #else
161       m_packet_timeout(1),
162 #endif
163       m_echo_number(0),
164       m_supports_qEcho(eLazyBoolCalculate),
165       m_sequence_mutex(),
166       m_public_is_running(false),
167       m_private_is_running(false),
168       m_history(512),
169       m_send_acks(true),
170       m_compression_type(CompressionType::None),
171       m_listen_url()
172 {
173 }
174 
175 //----------------------------------------------------------------------
176 // Destructor
177 //----------------------------------------------------------------------
178 GDBRemoteCommunication::~GDBRemoteCommunication()
179 {
180     if (IsConnected())
181     {
182         Disconnect();
183     }
184 
185     // Stop the communications read thread which is used to parse all
186     // incoming packets.  This function will block until the read
187     // thread returns.
188     if (m_read_thread_enabled)
189         StopReadThread();
190 }
191 
192 char
193 GDBRemoteCommunication::CalculcateChecksum (const char *payload, size_t payload_length)
194 {
195     int checksum = 0;
196 
197     for (size_t i = 0; i < payload_length; ++i)
198         checksum += payload[i];
199 
200     return checksum & 255;
201 }
202 
203 size_t
204 GDBRemoteCommunication::SendAck ()
205 {
206     Log *log (ProcessGDBRemoteLog::GetLogIfAllCategoriesSet (GDBR_LOG_PACKETS));
207     ConnectionStatus status = eConnectionStatusSuccess;
208     char ch = '+';
209     const size_t bytes_written = Write (&ch, 1, status, NULL);
210     if (log)
211         log->Printf ("<%4" PRIu64 "> send packet: %c", (uint64_t)bytes_written, ch);
212     m_history.AddPacket (ch, History::ePacketTypeSend, bytes_written);
213     return bytes_written;
214 }
215 
216 size_t
217 GDBRemoteCommunication::SendNack ()
218 {
219     Log *log (ProcessGDBRemoteLog::GetLogIfAllCategoriesSet (GDBR_LOG_PACKETS));
220     ConnectionStatus status = eConnectionStatusSuccess;
221     char ch = '-';
222     const size_t bytes_written = Write (&ch, 1, status, NULL);
223     if (log)
224         log->Printf("<%4" PRIu64 "> send packet: %c", (uint64_t)bytes_written, ch);
225     m_history.AddPacket (ch, History::ePacketTypeSend, bytes_written);
226     return bytes_written;
227 }
228 
229 GDBRemoteCommunication::PacketResult
230 GDBRemoteCommunication::SendPacket (const char *payload, size_t payload_length)
231 {
232     std::lock_guard<std::recursive_mutex> guard(m_sequence_mutex);
233     return SendPacketNoLock (payload, payload_length);
234 }
235 
236 GDBRemoteCommunication::PacketResult
237 GDBRemoteCommunication::SendPacketNoLock (const char *payload, size_t payload_length)
238 {
239     if (IsConnected())
240     {
241         StreamString packet(0, 4, eByteOrderBig);
242 
243         packet.PutChar('$');
244         packet.Write (payload, payload_length);
245         packet.PutChar('#');
246         packet.PutHex8(CalculcateChecksum (payload, payload_length));
247 
248         Log *log (ProcessGDBRemoteLog::GetLogIfAllCategoriesSet (GDBR_LOG_PACKETS));
249         ConnectionStatus status = eConnectionStatusSuccess;
250         const char *packet_data = packet.GetData();
251         const size_t packet_length = packet.GetSize();
252         size_t bytes_written = Write (packet_data, packet_length, status, NULL);
253         if (log)
254         {
255             size_t binary_start_offset = 0;
256             if (strncmp(packet_data, "$vFile:pwrite:", strlen("$vFile:pwrite:")) == 0)
257             {
258                 const char *first_comma = strchr(packet_data, ',');
259                 if (first_comma)
260                 {
261                     const char *second_comma = strchr(first_comma + 1, ',');
262                     if (second_comma)
263                         binary_start_offset = second_comma - packet_data + 1;
264                 }
265             }
266 
267             // If logging was just enabled and we have history, then dump out what
268             // we have to the log so we get the historical context. The Dump() call that
269             // logs all of the packet will set a boolean so that we don't dump this more
270             // than once
271             if (!m_history.DidDumpToLog ())
272                 m_history.Dump (log);
273 
274             if (binary_start_offset)
275             {
276                 StreamString strm;
277                 // Print non binary data header
278                 strm.Printf("<%4" PRIu64 "> send packet: %.*s", (uint64_t)bytes_written, (int)binary_start_offset, packet_data);
279                 const uint8_t *p;
280                 // Print binary data exactly as sent
281                 for (p = (const uint8_t*)packet_data + binary_start_offset; *p != '#'; ++p)
282                     strm.Printf("\\x%2.2x", *p);
283                 // Print the checksum
284                 strm.Printf("%*s", (int)3, p);
285                 log->PutCString(strm.GetString().c_str());
286             }
287             else
288                 log->Printf("<%4" PRIu64 "> send packet: %.*s", (uint64_t)bytes_written, (int)packet_length, packet_data);
289         }
290 
291         m_history.AddPacket (packet.GetString(), packet_length, History::ePacketTypeSend, bytes_written);
292 
293 
294         if (bytes_written == packet_length)
295         {
296             if (GetSendAcks ())
297                 return GetAck ();
298             else
299                 return PacketResult::Success;
300         }
301         else
302         {
303             if (log)
304                 log->Printf ("error: failed to send packet: %.*s", (int)packet_length, packet_data);
305         }
306     }
307     return PacketResult::ErrorSendFailed;
308 }
309 
310 GDBRemoteCommunication::PacketResult
311 GDBRemoteCommunication::GetAck ()
312 {
313     StringExtractorGDBRemote packet;
314     PacketResult result = ReadPacket (packet, GetPacketTimeoutInMicroSeconds (), false);
315     if (result == PacketResult::Success)
316     {
317         if (packet.GetResponseType() == StringExtractorGDBRemote::ResponseType::eAck)
318             return PacketResult::Success;
319         else
320             return PacketResult::ErrorSendAck;
321     }
322     return result;
323 }
324 
325 bool
326 GDBRemoteCommunication::GetSequenceMutex(std::unique_lock<std::recursive_mutex> &lock, const char *failure_message)
327 {
328     if (IsRunning())
329         return (lock = std::unique_lock<std::recursive_mutex>(m_sequence_mutex, std::try_to_lock)).owns_lock();
330 
331     lock = std::unique_lock<std::recursive_mutex>(m_sequence_mutex);
332     return true;
333 }
334 
335 bool
336 GDBRemoteCommunication::WaitForNotRunningPrivate(const std::chrono::microseconds &timeout)
337 {
338     return m_private_is_running.WaitForValueEqualTo(false, timeout, NULL);
339 }
340 
341 GDBRemoteCommunication::PacketResult
342 GDBRemoteCommunication::ReadPacket (StringExtractorGDBRemote &response, uint32_t timeout_usec, bool sync_on_timeout)
343 {
344    if (m_read_thread_enabled)
345        return PopPacketFromQueue (response, timeout_usec);
346    else
347        return WaitForPacketWithTimeoutMicroSecondsNoLock (response, timeout_usec, sync_on_timeout);
348 }
349 
350 
351 // This function is called when a packet is requested.
352 // A whole packet is popped from the packet queue and returned to the caller.
353 // Packets are placed into this queue from the communication read thread.
354 // See GDBRemoteCommunication::AppendBytesToCache.
355 GDBRemoteCommunication::PacketResult
356 GDBRemoteCommunication::PopPacketFromQueue (StringExtractorGDBRemote &response, uint32_t timeout_usec)
357 {
358     auto until = std::chrono::system_clock::now() + std::chrono::microseconds(timeout_usec);
359 
360     while (true)
361     {
362         // scope for the mutex
363         {
364             // lock down the packet queue
365             std::unique_lock<std::mutex> lock(m_packet_queue_mutex);
366 
367             // Wait on condition variable.
368             if (m_packet_queue.size() == 0)
369             {
370                 std::cv_status result = m_condition_queue_not_empty.wait_until(lock, until);
371                 if (result == std::cv_status::timeout)
372                   break;
373             }
374 
375             if (m_packet_queue.size() > 0)
376             {
377                 // get the front element of the queue
378                 response = m_packet_queue.front();
379 
380                 // remove the front element
381                 m_packet_queue.pop();
382 
383                 // we got a packet
384                 return PacketResult::Success;
385             }
386          }
387 
388          // Disconnected
389          if (!IsConnected())
390              return PacketResult::ErrorDisconnected;
391 
392       // Loop while not timed out
393     }
394 
395     return PacketResult::ErrorReplyTimeout;
396 }
397 
398 
399 GDBRemoteCommunication::PacketResult
400 GDBRemoteCommunication::WaitForPacketWithTimeoutMicroSecondsNoLock (StringExtractorGDBRemote &packet, uint32_t timeout_usec, bool sync_on_timeout)
401 {
402     uint8_t buffer[8192];
403     Error error;
404 
405     Log *log (ProcessGDBRemoteLog::GetLogIfAllCategoriesSet (GDBR_LOG_PACKETS | GDBR_LOG_VERBOSE));
406 
407     // Check for a packet from our cache first without trying any reading...
408     if (CheckForPacket(NULL, 0, packet) != PacketType::Invalid)
409         return PacketResult::Success;
410 
411     bool timed_out = false;
412     bool disconnected = false;
413     while (IsConnected() && !timed_out)
414     {
415         lldb::ConnectionStatus status = eConnectionStatusNoConnection;
416         size_t bytes_read = Read (buffer, sizeof(buffer), timeout_usec, status, &error);
417 
418         if (log)
419             log->Printf ("%s: Read (buffer, (sizeof(buffer), timeout_usec = 0x%x, status = %s, error = %s) => bytes_read = %" PRIu64,
420                          __PRETTY_FUNCTION__,
421                          timeout_usec,
422                          Communication::ConnectionStatusAsCString (status),
423                          error.AsCString(),
424                          (uint64_t)bytes_read);
425 
426         if (bytes_read > 0)
427         {
428             if (CheckForPacket(buffer, bytes_read, packet) != PacketType::Invalid)
429                 return PacketResult::Success;
430         }
431         else
432         {
433             switch (status)
434             {
435             case eConnectionStatusTimedOut:
436             case eConnectionStatusInterrupted:
437                 if (sync_on_timeout)
438                 {
439                     //------------------------------------------------------------------
440                     /// Sync the remote GDB server and make sure we get a response that
441                     /// corresponds to what we send.
442                     ///
443                     /// Sends a "qEcho" packet and makes sure it gets the exact packet
444                     /// echoed back. If the qEcho packet isn't supported, we send a qC
445                     /// packet and make sure we get a valid thread ID back. We use the
446                     /// "qC" packet since its response if very unique: is responds with
447                     /// "QC%x" where %x is the thread ID of the current thread. This
448                     /// makes the response unique enough from other packet responses to
449                     /// ensure we are back on track.
450                     ///
451                     /// This packet is needed after we time out sending a packet so we
452                     /// can ensure that we are getting the response for the packet we
453                     /// are sending. There are no sequence IDs in the GDB remote
454                     /// protocol (there used to be, but they are not supported anymore)
455                     /// so if you timeout sending packet "abc", you might then send
456                     /// packet "cde" and get the response for the previous "abc" packet.
457                     /// Many responses are "OK" or "" (unsupported) or "EXX" (error) so
458                     /// many responses for packets can look like responses for other
459                     /// packets. So if we timeout, we need to ensure that we can get
460                     /// back on track. If we can't get back on track, we must
461                     /// disconnect.
462                     //------------------------------------------------------------------
463                     bool sync_success = false;
464                     bool got_actual_response = false;
465                     // We timed out, we need to sync back up with the
466                     char echo_packet[32];
467                     int echo_packet_len = 0;
468                     RegularExpression response_regex;
469 
470                     if (m_supports_qEcho == eLazyBoolYes)
471                     {
472                         echo_packet_len = ::snprintf (echo_packet, sizeof(echo_packet), "qEcho:%u", ++m_echo_number);
473                         std::string regex_str = "^";
474                         regex_str += echo_packet;
475                         regex_str += "$";
476                         response_regex.Compile(regex_str.c_str());
477                     }
478                     else
479                     {
480                         echo_packet_len = ::snprintf (echo_packet, sizeof(echo_packet), "qC");
481                         response_regex.Compile("^QC[0-9A-Fa-f]+$");
482                     }
483 
484                     PacketResult echo_packet_result = SendPacketNoLock (echo_packet, echo_packet_len);
485                     if (echo_packet_result == PacketResult::Success)
486                     {
487                         const uint32_t max_retries = 3;
488                         uint32_t successful_responses = 0;
489                         for (uint32_t i=0; i<max_retries; ++i)
490                         {
491                             StringExtractorGDBRemote echo_response;
492                             echo_packet_result = WaitForPacketWithTimeoutMicroSecondsNoLock (echo_response, timeout_usec, false);
493                             if (echo_packet_result == PacketResult::Success)
494                             {
495                                 ++successful_responses;
496                                 if (response_regex.Execute(echo_response.GetStringRef().c_str()))
497                                 {
498                                     sync_success = true;
499                                     break;
500                                 }
501                                 else if (successful_responses == 1)
502                                 {
503                                     // We got something else back as the first successful response, it probably is
504                                     // the  response to the packet we actually wanted, so copy it over if this
505                                     // is the first success and continue to try to get the qEcho response
506                                     packet = echo_response;
507                                     got_actual_response = true;
508                                 }
509                             }
510                             else if (echo_packet_result == PacketResult::ErrorReplyTimeout)
511                                 continue;   // Packet timed out, continue waiting for a response
512                             else
513                                 break;      // Something else went wrong getting the packet back, we failed and are done trying
514                         }
515                     }
516 
517                     // We weren't able to sync back up with the server, we must abort otherwise
518                     // all responses might not be from the right packets...
519                     if (sync_success)
520                     {
521                         // We timed out, but were able to recover
522                         if (got_actual_response)
523                         {
524                             // We initially timed out, but we did get a response that came in before the successful
525                             // reply to our qEcho packet, so lets say everything is fine...
526                             return PacketResult::Success;
527                         }
528                     }
529                     else
530                     {
531                         disconnected = true;
532                         Disconnect();
533                     }
534                 }
535                 timed_out = true;
536                 break;
537             case eConnectionStatusSuccess:
538                 //printf ("status = success but error = %s\n", error.AsCString("<invalid>"));
539                 break;
540 
541             case eConnectionStatusEndOfFile:
542             case eConnectionStatusNoConnection:
543             case eConnectionStatusLostConnection:
544             case eConnectionStatusError:
545                 disconnected = true;
546                 Disconnect();
547                 break;
548             }
549         }
550     }
551     packet.Clear ();
552     if (disconnected)
553         return PacketResult::ErrorDisconnected;
554     if (timed_out)
555         return PacketResult::ErrorReplyTimeout;
556     else
557         return PacketResult::ErrorReplyFailed;
558 }
559 
560 bool
561 GDBRemoteCommunication::DecompressPacket ()
562 {
563     Log *log (ProcessGDBRemoteLog::GetLogIfAllCategoriesSet (GDBR_LOG_PACKETS));
564 
565     if (!CompressionIsEnabled())
566         return true;
567 
568     size_t pkt_size = m_bytes.size();
569 
570     // Smallest possible compressed packet is $N#00 - an uncompressed empty reply, most commonly indicating
571     // an unsupported packet.  Anything less than 5 characters, it's definitely not a compressed packet.
572     if (pkt_size < 5)
573         return true;
574 
575     if (m_bytes[0] != '$' && m_bytes[0] != '%')
576         return true;
577     if (m_bytes[1] != 'C' && m_bytes[1] != 'N')
578         return true;
579 
580     size_t hash_mark_idx = m_bytes.find ('#');
581     if (hash_mark_idx == std::string::npos)
582         return true;
583     if (hash_mark_idx + 2 >= m_bytes.size())
584         return true;
585 
586     if (!::isxdigit (m_bytes[hash_mark_idx + 1]) || !::isxdigit (m_bytes[hash_mark_idx + 2]))
587         return true;
588 
589     size_t content_length = pkt_size - 5;    // not counting '$', 'C' | 'N', '#', & the two hex checksum chars
590     size_t content_start = 2;                // The first character of the compressed/not-compressed text of the packet
591     size_t checksum_idx = hash_mark_idx + 1; // The first character of the two hex checksum characters
592 
593     // Normally size_of_first_packet == m_bytes.size() but m_bytes may contain multiple packets.
594     // size_of_first_packet is the size of the initial packet which we'll replace with the decompressed
595     // version of, leaving the rest of m_bytes unmodified.
596     size_t size_of_first_packet = hash_mark_idx + 3;
597 
598     // Compressed packets ("$C") start with a base10 number which is the size of the uncompressed payload,
599     // then a : and then the compressed data.  e.g. $C1024:<binary>#00
600     // Update content_start and content_length to only include the <binary> part of the packet.
601 
602     uint64_t decompressed_bufsize = ULONG_MAX;
603     if (m_bytes[1] == 'C')
604     {
605         size_t i = content_start;
606         while (i < hash_mark_idx && isdigit(m_bytes[i]))
607             i++;
608         if (i < hash_mark_idx && m_bytes[i] == ':')
609         {
610             i++;
611             content_start = i;
612             content_length = hash_mark_idx - content_start;
613             std::string bufsize_str (m_bytes.data() + 2, i - 2 - 1);
614             errno = 0;
615             decompressed_bufsize = ::strtoul (bufsize_str.c_str(), NULL, 10);
616             if (errno != 0 || decompressed_bufsize == ULONG_MAX)
617             {
618                 m_bytes.erase (0, size_of_first_packet);
619                 return false;
620             }
621         }
622     }
623 
624     if (GetSendAcks ())
625     {
626         char packet_checksum_cstr[3];
627         packet_checksum_cstr[0] = m_bytes[checksum_idx];
628         packet_checksum_cstr[1] = m_bytes[checksum_idx + 1];
629         packet_checksum_cstr[2] = '\0';
630         long packet_checksum = strtol (packet_checksum_cstr, NULL, 16);
631 
632         long actual_checksum = CalculcateChecksum (m_bytes.data() + 1, hash_mark_idx - 1);
633         bool success = packet_checksum == actual_checksum;
634         if (!success)
635         {
636             if (log)
637                 log->Printf ("error: checksum mismatch: %.*s expected 0x%2.2x, got 0x%2.2x",
638                              (int)(pkt_size),
639                              m_bytes.c_str(),
640                              (uint8_t)packet_checksum,
641                              (uint8_t)actual_checksum);
642         }
643         // Send the ack or nack if needed
644         if (!success)
645         {
646             SendNack();
647             m_bytes.erase (0, size_of_first_packet);
648             return false;
649         }
650         else
651         {
652             SendAck();
653         }
654     }
655 
656     if (m_bytes[1] == 'N')
657     {
658         // This packet was not compressed -- delete the 'N' character at the
659         // start and the packet may be processed as-is.
660         m_bytes.erase(1, 1);
661         return true;
662     }
663 
664     // Reverse the gdb-remote binary escaping that was done to the compressed text to
665     // guard characters like '$', '#', '}', etc.
666     std::vector<uint8_t> unescaped_content;
667     unescaped_content.reserve (content_length);
668     size_t i = content_start;
669     while (i < hash_mark_idx)
670     {
671         if (m_bytes[i] == '}')
672         {
673             i++;
674             unescaped_content.push_back (m_bytes[i] ^ 0x20);
675         }
676         else
677         {
678             unescaped_content.push_back (m_bytes[i]);
679         }
680         i++;
681     }
682 
683     uint8_t *decompressed_buffer = nullptr;
684     size_t decompressed_bytes = 0;
685 
686     if (decompressed_bufsize != ULONG_MAX)
687     {
688         decompressed_buffer = (uint8_t *) malloc (decompressed_bufsize + 1);
689         if (decompressed_buffer == nullptr)
690         {
691             m_bytes.erase (0, size_of_first_packet);
692             return false;
693         }
694 
695     }
696 
697 #if defined (HAVE_LIBCOMPRESSION)
698     // libcompression is weak linked so check that compression_decode_buffer() is available
699     if (compression_decode_buffer != NULL &&
700         (m_compression_type == CompressionType::ZlibDeflate
701          || m_compression_type == CompressionType::LZFSE
702          || m_compression_type == CompressionType::LZ4))
703     {
704         compression_algorithm compression_type;
705         if (m_compression_type == CompressionType::ZlibDeflate)
706             compression_type = COMPRESSION_ZLIB;
707         else if (m_compression_type == CompressionType::LZFSE)
708             compression_type = COMPRESSION_LZFSE;
709         else if (m_compression_type == CompressionType::LZ4)
710             compression_type = COMPRESSION_LZ4_RAW;
711         else if (m_compression_type == CompressionType::LZMA)
712             compression_type = COMPRESSION_LZMA;
713 
714 
715         // If we have the expected size of the decompressed payload, we can allocate
716         // the right-sized buffer and do it.  If we don't have that information, we'll
717         // need to try decoding into a big buffer and if the buffer wasn't big enough,
718         // increase it and try again.
719 
720         if (decompressed_bufsize != ULONG_MAX && decompressed_buffer != nullptr)
721         {
722             decompressed_bytes = compression_decode_buffer (decompressed_buffer, decompressed_bufsize + 10 ,
723                                                         (uint8_t*) unescaped_content.data(),
724                                                         unescaped_content.size(),
725                                                         NULL,
726                                                         compression_type);
727         }
728     }
729 #endif
730 
731 #if defined (HAVE_LIBZ)
732     if (decompressed_bytes == 0
733         && decompressed_bufsize != ULONG_MAX
734         && decompressed_buffer != nullptr
735         && m_compression_type == CompressionType::ZlibDeflate)
736     {
737         z_stream stream;
738         memset (&stream, 0, sizeof (z_stream));
739         stream.next_in = (Bytef *) unescaped_content.data();
740         stream.avail_in = (uInt) unescaped_content.size();
741         stream.total_in = 0;
742         stream.next_out = (Bytef *) decompressed_buffer;
743         stream.avail_out = decompressed_bufsize;
744         stream.total_out = 0;
745         stream.zalloc = Z_NULL;
746         stream.zfree = Z_NULL;
747         stream.opaque = Z_NULL;
748 
749         if (inflateInit2 (&stream, -15) == Z_OK)
750         {
751             int status = inflate (&stream, Z_NO_FLUSH);
752             inflateEnd (&stream);
753             if (status == Z_STREAM_END)
754             {
755                 decompressed_bytes = stream.total_out;
756             }
757         }
758     }
759 #endif
760 
761     if (decompressed_bytes == 0 || decompressed_buffer == nullptr)
762     {
763         if (decompressed_buffer)
764             free (decompressed_buffer);
765         m_bytes.erase (0, size_of_first_packet);
766         return false;
767     }
768 
769     std::string new_packet;
770     new_packet.reserve (decompressed_bytes + 6);
771     new_packet.push_back (m_bytes[0]);
772     new_packet.append ((const char *) decompressed_buffer, decompressed_bytes);
773     new_packet.push_back ('#');
774     if (GetSendAcks ())
775     {
776         uint8_t decompressed_checksum = CalculcateChecksum ((const char *) decompressed_buffer, decompressed_bytes);
777         char decompressed_checksum_str[3];
778         snprintf (decompressed_checksum_str, 3, "%02x", decompressed_checksum);
779         new_packet.append (decompressed_checksum_str);
780     }
781     else
782     {
783         new_packet.push_back ('0');
784         new_packet.push_back ('0');
785     }
786 
787     m_bytes.replace (0, size_of_first_packet, new_packet.data(), new_packet.size());
788 
789     free (decompressed_buffer);
790     return true;
791 }
792 
793 GDBRemoteCommunication::PacketType
794 GDBRemoteCommunication::CheckForPacket (const uint8_t *src, size_t src_len, StringExtractorGDBRemote &packet)
795 {
796     // Put the packet data into the buffer in a thread safe fashion
797     std::lock_guard<std::recursive_mutex> guard(m_bytes_mutex);
798 
799     Log *log (ProcessGDBRemoteLog::GetLogIfAllCategoriesSet (GDBR_LOG_PACKETS));
800 
801     if (src && src_len > 0)
802     {
803         if (log && log->GetVerbose())
804         {
805             StreamString s;
806             log->Printf ("GDBRemoteCommunication::%s adding %u bytes: %.*s",
807                          __FUNCTION__,
808                          (uint32_t)src_len,
809                          (uint32_t)src_len,
810                          src);
811         }
812         m_bytes.append ((const char *)src, src_len);
813     }
814 
815     bool isNotifyPacket = false;
816 
817     // Parse up the packets into gdb remote packets
818     if (!m_bytes.empty())
819     {
820         // end_idx must be one past the last valid packet byte. Start
821         // it off with an invalid value that is the same as the current
822         // index.
823         size_t content_start = 0;
824         size_t content_length = 0;
825         size_t total_length = 0;
826         size_t checksum_idx = std::string::npos;
827 
828         // Size of packet before it is decompressed, for logging purposes
829         size_t original_packet_size = m_bytes.size();
830         if (CompressionIsEnabled())
831         {
832             if (DecompressPacket() == false)
833             {
834                 packet.Clear();
835                 return GDBRemoteCommunication::PacketType::Standard;
836             }
837         }
838 
839         switch (m_bytes[0])
840         {
841             case '+':       // Look for ack
842             case '-':       // Look for cancel
843             case '\x03':    // ^C to halt target
844                 content_length = total_length = 1;  // The command is one byte long...
845                 break;
846 
847             case '%': // Async notify packet
848                 isNotifyPacket = true;
849                 LLVM_FALLTHROUGH;
850 
851             case '$':
852                 // Look for a standard gdb packet?
853                 {
854                     size_t hash_pos = m_bytes.find('#');
855                     if (hash_pos != std::string::npos)
856                     {
857                         if (hash_pos + 2 < m_bytes.size())
858                         {
859                             checksum_idx = hash_pos + 1;
860                             // Skip the dollar sign
861                             content_start = 1;
862                             // Don't include the # in the content or the $ in the content length
863                             content_length = hash_pos - 1;
864 
865                             total_length = hash_pos + 3; // Skip the # and the two hex checksum bytes
866                         }
867                         else
868                         {
869                             // Checksum bytes aren't all here yet
870                             content_length = std::string::npos;
871                         }
872                     }
873                 }
874                 break;
875 
876             default:
877                 {
878                     // We have an unexpected byte and we need to flush all bad
879                     // data that is in m_bytes, so we need to find the first
880                     // byte that is a '+' (ACK), '-' (NACK), \x03 (CTRL+C interrupt),
881                     // or '$' character (start of packet header) or of course,
882                     // the end of the data in m_bytes...
883                     const size_t bytes_len = m_bytes.size();
884                     bool done = false;
885                     uint32_t idx;
886                     for (idx = 1; !done && idx < bytes_len; ++idx)
887                     {
888                         switch (m_bytes[idx])
889                         {
890                         case '+':
891                         case '-':
892                         case '\x03':
893                         case '%':
894                         case '$':
895                             done = true;
896                             break;
897 
898                         default:
899                             break;
900                         }
901                     }
902                     if (log)
903                         log->Printf ("GDBRemoteCommunication::%s tossing %u junk bytes: '%.*s'",
904                                      __FUNCTION__, idx - 1, idx - 1, m_bytes.c_str());
905                     m_bytes.erase(0, idx - 1);
906                 }
907                 break;
908         }
909 
910         if (content_length == std::string::npos)
911         {
912             packet.Clear();
913             return GDBRemoteCommunication::PacketType::Invalid;
914         }
915         else if (total_length > 0)
916         {
917 
918             // We have a valid packet...
919             assert (content_length <= m_bytes.size());
920             assert (total_length <= m_bytes.size());
921             assert (content_length <= total_length);
922             size_t content_end = content_start + content_length;
923 
924             bool success = true;
925             std::string &packet_str = packet.GetStringRef();
926             if (log)
927             {
928                 // If logging was just enabled and we have history, then dump out what
929                 // we have to the log so we get the historical context. The Dump() call that
930                 // logs all of the packet will set a boolean so that we don't dump this more
931                 // than once
932                 if (!m_history.DidDumpToLog ())
933                     m_history.Dump (log);
934 
935                 bool binary = false;
936                 // Only detect binary for packets that start with a '$' and have a '#CC' checksum
937                 if (m_bytes[0] == '$' && total_length > 4)
938                 {
939                     for (size_t i=0; !binary && i<total_length; ++i)
940                     {
941                         if (isprint (m_bytes[i]) == 0 && isspace (m_bytes[i]) == 0)
942                         {
943                             binary = true;
944                         }
945                     }
946                 }
947                 if (binary)
948                 {
949                     StreamString strm;
950                     // Packet header...
951                     if (CompressionIsEnabled())
952                         strm.Printf("<%4" PRIu64 ":%" PRIu64 "> read packet: %c", (uint64_t) original_packet_size, (uint64_t)total_length, m_bytes[0]);
953                     else
954                         strm.Printf("<%4" PRIu64 "> read packet: %c", (uint64_t)total_length, m_bytes[0]);
955                     for (size_t i=content_start; i<content_end; ++i)
956                     {
957                         // Remove binary escaped bytes when displaying the packet...
958                         const char ch = m_bytes[i];
959                         if (ch == 0x7d)
960                         {
961                             // 0x7d is the escape character.  The next character is to
962                             // be XOR'd with 0x20.
963                             const char escapee = m_bytes[++i] ^ 0x20;
964                             strm.Printf("%2.2x", escapee);
965                         }
966                         else
967                         {
968                             strm.Printf("%2.2x", (uint8_t)ch);
969                         }
970                     }
971                     // Packet footer...
972                     strm.Printf("%c%c%c", m_bytes[total_length-3], m_bytes[total_length-2], m_bytes[total_length-1]);
973                     log->PutCString(strm.GetString().c_str());
974                 }
975                 else
976                 {
977                     if (CompressionIsEnabled())
978                         log->Printf("<%4" PRIu64 ":%" PRIu64 "> read packet: %.*s", (uint64_t) original_packet_size, (uint64_t)total_length, (int)(total_length), m_bytes.c_str());
979                     else
980                         log->Printf("<%4" PRIu64 "> read packet: %.*s", (uint64_t)total_length, (int)(total_length), m_bytes.c_str());
981                 }
982             }
983 
984             m_history.AddPacket (m_bytes.c_str(), total_length, History::ePacketTypeRecv, total_length);
985 
986             // Clear packet_str in case there is some existing data in it.
987             packet_str.clear();
988             // Copy the packet from m_bytes to packet_str expanding the
989             // run-length encoding in the process.
990             // Reserve enough byte for the most common case (no RLE used)
991             packet_str.reserve(m_bytes.length());
992             for (std::string::const_iterator c = m_bytes.begin() + content_start; c != m_bytes.begin() + content_end; ++c)
993             {
994                 if (*c == '*')
995                 {
996                     // '*' indicates RLE. Next character will give us the
997                     // repeat count and previous character is what is to be
998                     // repeated.
999                     char char_to_repeat = packet_str.back();
1000                     // Number of time the previous character is repeated
1001                     int repeat_count = *++c + 3 - ' ';
1002                     // We have the char_to_repeat and repeat_count. Now push
1003                     // it in the packet.
1004                     for (int i = 0; i < repeat_count; ++i)
1005                         packet_str.push_back(char_to_repeat);
1006                 }
1007                 else if (*c == 0x7d)
1008                 {
1009                     // 0x7d is the escape character.  The next character is to
1010                     // be XOR'd with 0x20.
1011                     char escapee = *++c ^ 0x20;
1012                     packet_str.push_back(escapee);
1013                 }
1014                 else
1015                 {
1016                     packet_str.push_back(*c);
1017                 }
1018             }
1019 
1020             if (m_bytes[0] == '$' || m_bytes[0] == '%')
1021             {
1022                 assert (checksum_idx < m_bytes.size());
1023                 if (::isxdigit (m_bytes[checksum_idx+0]) ||
1024                     ::isxdigit (m_bytes[checksum_idx+1]))
1025                 {
1026                     if (GetSendAcks ())
1027                     {
1028                         const char *packet_checksum_cstr = &m_bytes[checksum_idx];
1029                         char packet_checksum = strtol (packet_checksum_cstr, NULL, 16);
1030                         char actual_checksum = CalculcateChecksum (packet_str.c_str(), packet_str.size());
1031                         success = packet_checksum == actual_checksum;
1032                         if (!success)
1033                         {
1034                             if (log)
1035                                 log->Printf ("error: checksum mismatch: %.*s expected 0x%2.2x, got 0x%2.2x",
1036                                              (int)(total_length),
1037                                              m_bytes.c_str(),
1038                                              (uint8_t)packet_checksum,
1039                                              (uint8_t)actual_checksum);
1040                         }
1041                         // Send the ack or nack if needed
1042                         if (!success)
1043                             SendNack();
1044                         else
1045                             SendAck();
1046                     }
1047                 }
1048                 else
1049                 {
1050                     success = false;
1051                     if (log)
1052                         log->Printf ("error: invalid checksum in packet: '%s'\n", m_bytes.c_str());
1053                 }
1054             }
1055 
1056             m_bytes.erase(0, total_length);
1057             packet.SetFilePos(0);
1058 
1059             if (isNotifyPacket)
1060                 return GDBRemoteCommunication::PacketType::Notify;
1061             else
1062                 return GDBRemoteCommunication::PacketType::Standard;
1063         }
1064     }
1065     packet.Clear();
1066     return GDBRemoteCommunication::PacketType::Invalid;
1067 }
1068 
1069 Error
1070 GDBRemoteCommunication::StartListenThread (const char *hostname, uint16_t port)
1071 {
1072     Error error;
1073     if (m_listen_thread.IsJoinable())
1074     {
1075         error.SetErrorString("listen thread already running");
1076     }
1077     else
1078     {
1079         char listen_url[512];
1080         if (hostname && hostname[0])
1081             snprintf(listen_url, sizeof(listen_url), "listen://%s:%i", hostname, port);
1082         else
1083             snprintf(listen_url, sizeof(listen_url), "listen://%i", port);
1084         m_listen_url = listen_url;
1085         SetConnection(new ConnectionFileDescriptor());
1086         m_listen_thread = ThreadLauncher::LaunchThread(listen_url, GDBRemoteCommunication::ListenThread, this, &error);
1087     }
1088     return error;
1089 }
1090 
1091 bool
1092 GDBRemoteCommunication::JoinListenThread ()
1093 {
1094     if (m_listen_thread.IsJoinable())
1095         m_listen_thread.Join(nullptr);
1096     return true;
1097 }
1098 
1099 lldb::thread_result_t
1100 GDBRemoteCommunication::ListenThread (lldb::thread_arg_t arg)
1101 {
1102     GDBRemoteCommunication *comm = (GDBRemoteCommunication *)arg;
1103     Error error;
1104     ConnectionFileDescriptor *connection = (ConnectionFileDescriptor *)comm->GetConnection ();
1105 
1106     if (connection)
1107     {
1108         // Do the listen on another thread so we can continue on...
1109         if (connection->Connect(comm->m_listen_url.c_str(), &error) != eConnectionStatusSuccess)
1110             comm->SetConnection(NULL);
1111     }
1112     return NULL;
1113 }
1114 
1115 Error
1116 GDBRemoteCommunication::StartDebugserverProcess (const char *url,
1117                                                  Platform *platform,
1118                                                  ProcessLaunchInfo &launch_info,
1119                                                  uint16_t *port,
1120                                                  const Args& inferior_args)
1121 {
1122     Log *log (ProcessGDBRemoteLog::GetLogIfAllCategoriesSet (GDBR_LOG_PROCESS));
1123     if (log)
1124         log->Printf ("GDBRemoteCommunication::%s(url=%s, port=%" PRIu16 ")", __FUNCTION__, url ? url : "<empty>", port ? *port : uint16_t(0));
1125 
1126     Error error;
1127     // If we locate debugserver, keep that located version around
1128     static FileSpec g_debugserver_file_spec;
1129 
1130     char debugserver_path[PATH_MAX];
1131     FileSpec &debugserver_file_spec = launch_info.GetExecutableFile();
1132 
1133     // Always check to see if we have an environment override for the path
1134     // to the debugserver to use and use it if we do.
1135     const char *env_debugserver_path = getenv("LLDB_DEBUGSERVER_PATH");
1136     if (env_debugserver_path)
1137     {
1138         debugserver_file_spec.SetFile (env_debugserver_path, false);
1139         if (log)
1140             log->Printf ("GDBRemoteCommunication::%s() gdb-remote stub exe path set from environment variable: %s", __FUNCTION__, env_debugserver_path);
1141     }
1142     else
1143         debugserver_file_spec = g_debugserver_file_spec;
1144     bool debugserver_exists = debugserver_file_spec.Exists();
1145     if (!debugserver_exists)
1146     {
1147         // The debugserver binary is in the LLDB.framework/Resources
1148         // directory.
1149         if (HostInfo::GetLLDBPath(ePathTypeSupportExecutableDir, debugserver_file_spec))
1150         {
1151             debugserver_file_spec.AppendPathComponent (DEBUGSERVER_BASENAME);
1152             debugserver_exists = debugserver_file_spec.Exists();
1153             if (debugserver_exists)
1154             {
1155                 if (log)
1156                     log->Printf ("GDBRemoteCommunication::%s() found gdb-remote stub exe '%s'", __FUNCTION__, debugserver_file_spec.GetPath ().c_str ());
1157 
1158                 g_debugserver_file_spec = debugserver_file_spec;
1159             }
1160             else
1161             {
1162                 debugserver_file_spec = platform->LocateExecutable(DEBUGSERVER_BASENAME);
1163                 if (debugserver_file_spec)
1164                 {
1165                     // Platform::LocateExecutable() wouldn't return a path if it doesn't exist
1166                     debugserver_exists = true;
1167                 }
1168                 else
1169                 {
1170                     if (log)
1171                         log->Printf ("GDBRemoteCommunication::%s() could not find gdb-remote stub exe '%s'", __FUNCTION__, debugserver_file_spec.GetPath ().c_str ());
1172                 }
1173                 // Don't cache the platform specific GDB server binary as it could change
1174                 // from platform to platform
1175                 g_debugserver_file_spec.Clear();
1176             }
1177         }
1178     }
1179 
1180     if (debugserver_exists)
1181     {
1182         debugserver_file_spec.GetPath (debugserver_path, sizeof(debugserver_path));
1183 
1184         Args &debugserver_args = launch_info.GetArguments();
1185         debugserver_args.Clear();
1186         char arg_cstr[PATH_MAX];
1187 
1188         // Start args with "debugserver /file/path -r --"
1189         debugserver_args.AppendArgument(debugserver_path);
1190 
1191 #if !defined(__APPLE__)
1192         // First argument to lldb-server must be mode in which to run.
1193         debugserver_args.AppendArgument("gdbserver");
1194 #endif
1195 
1196         // If a url is supplied then use it
1197         if (url)
1198             debugserver_args.AppendArgument(url);
1199 
1200         // use native registers, not the GDB registers
1201         debugserver_args.AppendArgument("--native-regs");
1202 
1203         if (launch_info.GetLaunchInSeparateProcessGroup())
1204         {
1205             debugserver_args.AppendArgument("--setsid");
1206         }
1207 
1208         llvm::SmallString<PATH_MAX> named_pipe_path;
1209         // socket_pipe is used by debug server to communicate back either
1210         // TCP port or domain socket name which it listens on.
1211         // The second purpose of the pipe to serve as a synchronization point -
1212         // once data is written to the pipe, debug server is up and running.
1213         Pipe socket_pipe;
1214 
1215         // port is null when debug server should listen on domain socket -
1216         // we're not interested in port value but rather waiting for debug server
1217         // to become available.
1218         if ((port != nullptr && *port == 0) || port == nullptr)
1219         {
1220             if (url)
1221             {
1222                 // Create a temporary file to get the stdout/stderr and redirect the
1223                 // output of the command into this file. We will later read this file
1224                 // if all goes well and fill the data into "command_output_ptr"
1225 
1226 #if defined(__APPLE__)
1227                 // Binding to port zero, we need to figure out what port it ends up
1228                 // using using a named pipe...
1229                 error = socket_pipe.CreateWithUniqueName("debugserver-named-pipe", false, named_pipe_path);
1230                 if (error.Fail())
1231                 {
1232                     if (log)
1233                         log->Printf("GDBRemoteCommunication::%s() "
1234                                 "named pipe creation failed: %s",
1235                                 __FUNCTION__, error.AsCString());
1236                     return error;
1237                 }
1238                 debugserver_args.AppendArgument("--named-pipe");
1239                 debugserver_args.AppendArgument(named_pipe_path.c_str());
1240 #else
1241                 // Binding to port zero, we need to figure out what port it ends up
1242                 // using using an unnamed pipe...
1243                 error = socket_pipe.CreateNew(true);
1244                 if (error.Fail())
1245                 {
1246                     if (log)
1247                         log->Printf("GDBRemoteCommunication::%s() "
1248                                 "unnamed pipe creation failed: %s",
1249                                 __FUNCTION__, error.AsCString());
1250                     return error;
1251                 }
1252                 int write_fd = socket_pipe.GetWriteFileDescriptor();
1253                 debugserver_args.AppendArgument("--pipe");
1254                 debugserver_args.AppendArgument(llvm::to_string(write_fd).c_str());
1255                 launch_info.AppendCloseFileAction(socket_pipe.GetReadFileDescriptor());
1256 #endif
1257             }
1258             else
1259             {
1260                 // No host and port given, so lets listen on our end and make the debugserver
1261                 // connect to us..
1262                 error = StartListenThread ("127.0.0.1", 0);
1263                 if (error.Fail())
1264                 {
1265                     if (log)
1266                         log->Printf ("GDBRemoteCommunication::%s() unable to start listen thread: %s", __FUNCTION__, error.AsCString());
1267                     return error;
1268                 }
1269 
1270                 ConnectionFileDescriptor *connection = (ConnectionFileDescriptor *)GetConnection ();
1271                 // Wait for 10 seconds to resolve the bound port
1272                 *port = connection->GetListeningPort(10);
1273                 if (*port > 0)
1274                 {
1275                     char port_cstr[32];
1276                     snprintf(port_cstr, sizeof(port_cstr), "127.0.0.1:%i", *port);
1277                     // Send the host and port down that debugserver and specify an option
1278                     // so that it connects back to the port we are listening to in this process
1279                     debugserver_args.AppendArgument("--reverse-connect");
1280                     debugserver_args.AppendArgument(port_cstr);
1281                 }
1282                 else
1283                 {
1284                     error.SetErrorString ("failed to bind to port 0 on 127.0.0.1");
1285                     if (log)
1286                         log->Printf ("GDBRemoteCommunication::%s() failed: %s", __FUNCTION__, error.AsCString());
1287                     return error;
1288                 }
1289             }
1290         }
1291 
1292         const char *env_debugserver_log_file = getenv("LLDB_DEBUGSERVER_LOG_FILE");
1293         if (env_debugserver_log_file)
1294         {
1295             ::snprintf (arg_cstr, sizeof(arg_cstr), "--log-file=%s", env_debugserver_log_file);
1296             debugserver_args.AppendArgument(arg_cstr);
1297         }
1298 
1299 #if defined(__APPLE__)
1300         const char *env_debugserver_log_flags = getenv("LLDB_DEBUGSERVER_LOG_FLAGS");
1301         if (env_debugserver_log_flags)
1302         {
1303             ::snprintf (arg_cstr, sizeof(arg_cstr), "--log-flags=%s", env_debugserver_log_flags);
1304             debugserver_args.AppendArgument(arg_cstr);
1305         }
1306 #else
1307         const char *env_debugserver_log_channels = getenv("LLDB_SERVER_LOG_CHANNELS");
1308         if (env_debugserver_log_channels)
1309         {
1310             ::snprintf (arg_cstr, sizeof(arg_cstr), "--log-channels=%s", env_debugserver_log_channels);
1311             debugserver_args.AppendArgument(arg_cstr);
1312         }
1313 #endif
1314 
1315         // Add additional args, starting with LLDB_DEBUGSERVER_EXTRA_ARG_1 until an env var doesn't come back.
1316         uint32_t env_var_index = 1;
1317         bool has_env_var;
1318         do
1319         {
1320             char env_var_name[64];
1321             snprintf (env_var_name, sizeof (env_var_name), "LLDB_DEBUGSERVER_EXTRA_ARG_%" PRIu32, env_var_index++);
1322             const char *extra_arg = getenv(env_var_name);
1323             has_env_var = extra_arg != nullptr;
1324 
1325             if (has_env_var)
1326             {
1327                 debugserver_args.AppendArgument (extra_arg);
1328                 if (log)
1329                     log->Printf ("GDBRemoteCommunication::%s adding env var %s contents to stub command line (%s)", __FUNCTION__, env_var_name, extra_arg);
1330             }
1331         } while (has_env_var);
1332 
1333         if (inferior_args.GetArgumentCount() > 0)
1334         {
1335             debugserver_args.AppendArgument ("--");
1336             debugserver_args.AppendArguments (inferior_args);
1337         }
1338 
1339         // Copy the current environment to the gdbserver/debugserver instance
1340         StringList env;
1341         if (Host::GetEnvironment(env))
1342         {
1343             for (size_t i = 0; i < env.GetSize(); ++i)
1344                 launch_info.GetEnvironmentEntries().AppendArgument(env[i].c_str());
1345         }
1346 
1347         // Close STDIN, STDOUT and STDERR.
1348         launch_info.AppendCloseFileAction (STDIN_FILENO);
1349         launch_info.AppendCloseFileAction (STDOUT_FILENO);
1350         launch_info.AppendCloseFileAction (STDERR_FILENO);
1351 
1352         // Redirect STDIN, STDOUT and STDERR to "/dev/null".
1353         launch_info.AppendSuppressFileAction (STDIN_FILENO, true, false);
1354         launch_info.AppendSuppressFileAction (STDOUT_FILENO, false, true);
1355         launch_info.AppendSuppressFileAction (STDERR_FILENO, false, true);
1356 
1357         if (log)
1358         {
1359             StreamString string_stream;
1360             Platform *const platform = nullptr;
1361             launch_info.Dump(string_stream, platform);
1362             log->Printf("launch info for gdb-remote stub:\n%s", string_stream.GetString().c_str());
1363         }
1364         error = Host::LaunchProcess(launch_info);
1365 
1366         if (error.Success() &&
1367             launch_info.GetProcessID() != LLDB_INVALID_PROCESS_ID)
1368         {
1369             if (named_pipe_path.size() > 0)
1370             {
1371                 error = socket_pipe.OpenAsReader(named_pipe_path, false);
1372                 if (error.Fail())
1373                     if (log)
1374                         log->Printf("GDBRemoteCommunication::%s() "
1375                                 "failed to open named pipe %s for reading: %s",
1376                                 __FUNCTION__, named_pipe_path.c_str(), error.AsCString());
1377             }
1378 
1379             if (socket_pipe.CanWrite())
1380                 socket_pipe.CloseWriteFileDescriptor();
1381             if (socket_pipe.CanRead())
1382             {
1383                 char port_cstr[PATH_MAX] = {0};
1384                 port_cstr[0] = '\0';
1385                 size_t num_bytes = sizeof(port_cstr);
1386                 // Read port from pipe with 10 second timeout.
1387                 error = socket_pipe.ReadWithTimeout(port_cstr, num_bytes,
1388                         std::chrono::seconds{10}, num_bytes);
1389                 if (error.Success() && (port != nullptr))
1390                 {
1391                     assert(num_bytes > 0 && port_cstr[num_bytes-1] == '\0');
1392                     *port = StringConvert::ToUInt32(port_cstr, 0);
1393                     if (log)
1394                         log->Printf("GDBRemoteCommunication::%s() "
1395                                     "debugserver listens %u port",
1396                                     __FUNCTION__, *port);
1397                 }
1398                 else
1399                 {
1400                     if (log)
1401                         log->Printf("GDBRemoteCommunication::%s() "
1402                                 "failed to read a port value from pipe %s: %s",
1403                                 __FUNCTION__, named_pipe_path.c_str(), error.AsCString());
1404 
1405                 }
1406                 socket_pipe.Close();
1407             }
1408 
1409             if (named_pipe_path.size() > 0)
1410             {
1411                 const auto err = socket_pipe.Delete(named_pipe_path);
1412                 if (err.Fail())
1413                 {
1414                     if (log)
1415                         log->Printf ("GDBRemoteCommunication::%s failed to delete pipe %s: %s",
1416                                 __FUNCTION__, named_pipe_path.c_str(), err.AsCString());
1417                 }
1418             }
1419 
1420             // Make sure we actually connect with the debugserver...
1421             JoinListenThread();
1422         }
1423     }
1424     else
1425     {
1426         error.SetErrorStringWithFormat ("unable to locate " DEBUGSERVER_BASENAME );
1427     }
1428 
1429     if (error.Fail())
1430     {
1431         if (log)
1432             log->Printf ("GDBRemoteCommunication::%s() failed: %s", __FUNCTION__, error.AsCString());
1433     }
1434 
1435     return error;
1436 }
1437 
1438 void
1439 GDBRemoteCommunication::DumpHistory(Stream &strm)
1440 {
1441     m_history.Dump (strm);
1442 }
1443 
1444 GDBRemoteCommunication::ScopedTimeout::ScopedTimeout (GDBRemoteCommunication& gdb_comm,
1445                                                       uint32_t timeout) :
1446     m_gdb_comm (gdb_comm)
1447 {
1448     m_saved_timeout = m_gdb_comm.SetPacketTimeout (timeout);
1449 }
1450 
1451 GDBRemoteCommunication::ScopedTimeout::~ScopedTimeout ()
1452 {
1453     m_gdb_comm.SetPacketTimeout (m_saved_timeout);
1454 }
1455 
1456 // This function is called via the Communications class read thread when bytes become available
1457 // for this connection. This function will consume all incoming bytes and try to parse whole
1458 // packets as they become available. Full packets are placed in a queue, so that all packet
1459 // requests can simply pop from this queue. Async notification packets will be dispatched
1460 // immediately to the ProcessGDBRemote Async thread via an event.
1461 void GDBRemoteCommunication::AppendBytesToCache (const uint8_t * bytes, size_t len, bool broadcast, lldb::ConnectionStatus status)
1462 {
1463     StringExtractorGDBRemote packet;
1464 
1465     while (true)
1466     {
1467         PacketType type = CheckForPacket(bytes, len, packet);
1468 
1469         // scrub the data so we do not pass it back to CheckForPacket
1470         // on future passes of the loop
1471         bytes = nullptr;
1472         len = 0;
1473 
1474         // we may have received no packet so lets bail out
1475         if (type == PacketType::Invalid)
1476             break;
1477 
1478         if (type == PacketType::Standard)
1479         {
1480             // scope for the mutex
1481             {
1482                 // lock down the packet queue
1483                 std::lock_guard<std::mutex> guard(m_packet_queue_mutex);
1484                 // push a new packet into the queue
1485                 m_packet_queue.push(packet);
1486                 // Signal condition variable that we have a packet
1487                 m_condition_queue_not_empty.notify_one();
1488             }
1489         }
1490 
1491         if (type == PacketType::Notify)
1492         {
1493             // put this packet into an event
1494             const char *pdata = packet.GetStringRef().c_str();
1495 
1496             // as the communication class, we are a broadcaster and the
1497             // async thread is tuned to listen to us
1498             BroadcastEvent(
1499                 eBroadcastBitGdbReadThreadGotNotify,
1500                 new EventDataBytes(pdata));
1501         }
1502     }
1503 }
1504