1 //===-- Communication.cpp -------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "lldb/Core/Communication.h"
10 
11 #include "lldb/Host/HostThread.h"
12 #include "lldb/Host/ThreadLauncher.h"
13 #include "lldb/Utility/Connection.h"
14 #include "lldb/Utility/ConstString.h"
15 #include "lldb/Utility/Event.h"
16 #include "lldb/Utility/Listener.h"
17 #include "lldb/Utility/Log.h"
18 #include "lldb/Utility/Logging.h"
19 #include "lldb/Utility/Status.h"
20 
21 #include "llvm/ADT/None.h"
22 #include "llvm/ADT/Optional.h"
23 #include "llvm/Support/Compiler.h"
24 
25 #include <algorithm>
26 #include <chrono>
27 #include <cstring>
28 #include <memory>
29 
30 #include <errno.h>
31 #include <inttypes.h>
32 #include <stdio.h>
33 
34 using namespace lldb;
35 using namespace lldb_private;
36 
37 ConstString &Communication::GetStaticBroadcasterClass() {
38   static ConstString class_name("lldb.communication");
39   return class_name;
40 }
41 
42 Communication::Communication(const char *name)
43     : Broadcaster(nullptr, name), m_connection_sp(),
44       m_read_thread_enabled(false), m_read_thread_did_exit(false), m_bytes(),
45       m_bytes_mutex(), m_write_mutex(), m_synchronize_mutex(),
46       m_callback(nullptr), m_callback_baton(nullptr), m_close_on_eof(true)
47 
48 {
49 
50   LLDB_LOG(lldb_private::GetLogIfAnyCategoriesSet(LIBLLDB_LOG_OBJECT |
51                                                   LIBLLDB_LOG_COMMUNICATION),
52            "{0} Communication::Communication (name = {1})", this, name);
53 
54   SetEventName(eBroadcastBitDisconnected, "disconnected");
55   SetEventName(eBroadcastBitReadThreadGotBytes, "got bytes");
56   SetEventName(eBroadcastBitReadThreadDidExit, "read thread did exit");
57   SetEventName(eBroadcastBitReadThreadShouldExit, "read thread should exit");
58   SetEventName(eBroadcastBitPacketAvailable, "packet available");
59   SetEventName(eBroadcastBitNoMorePendingInput, "no more pending input");
60 
61   CheckInWithManager();
62 }
63 
64 Communication::~Communication() {
65   LLDB_LOG(lldb_private::GetLogIfAnyCategoriesSet(LIBLLDB_LOG_OBJECT |
66                                                   LIBLLDB_LOG_COMMUNICATION),
67            "{0} Communication::~Communication (name = {1})", this,
68            GetBroadcasterName().AsCString());
69   Clear();
70 }
71 
72 void Communication::Clear() {
73   SetReadThreadBytesReceivedCallback(nullptr, nullptr);
74   Disconnect(nullptr);
75   StopReadThread(nullptr);
76 }
77 
78 ConnectionStatus Communication::Connect(const char *url, Status *error_ptr) {
79   Clear();
80 
81   LLDB_LOG(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_COMMUNICATION),
82            "{0} Communication::Connect (url = {1})", this, url);
83 
84   lldb::ConnectionSP connection_sp(m_connection_sp);
85   if (connection_sp)
86     return connection_sp->Connect(url, error_ptr);
87   if (error_ptr)
88     error_ptr->SetErrorString("Invalid connection.");
89   return eConnectionStatusNoConnection;
90 }
91 
92 ConnectionStatus Communication::Disconnect(Status *error_ptr) {
93   LLDB_LOG(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_COMMUNICATION),
94            "{0} Communication::Disconnect ()", this);
95 
96   lldb::ConnectionSP connection_sp(m_connection_sp);
97   if (connection_sp) {
98     ConnectionStatus status = connection_sp->Disconnect(error_ptr);
99     // We currently don't protect connection_sp with any mutex for multi-
100     // threaded environments. So lets not nuke our connection class without
101     // putting some multi-threaded protections in. We also probably don't want
102     // to pay for the overhead it might cause if every time we access the
103     // connection we have to take a lock.
104     //
105     // This unique pointer will cleanup after itself when this object goes
106     // away, so there is no need to currently have it destroy itself
107     // immediately upon disconnect.
108     // connection_sp.reset();
109     return status;
110   }
111   return eConnectionStatusNoConnection;
112 }
113 
114 bool Communication::IsConnected() const {
115   lldb::ConnectionSP connection_sp(m_connection_sp);
116   return (connection_sp ? connection_sp->IsConnected() : false);
117 }
118 
119 bool Communication::HasConnection() const {
120   return m_connection_sp.get() != nullptr;
121 }
122 
123 size_t Communication::Read(void *dst, size_t dst_len,
124                            const Timeout<std::micro> &timeout,
125                            ConnectionStatus &status, Status *error_ptr) {
126   Log *log = GetLogIfAllCategoriesSet(LIBLLDB_LOG_COMMUNICATION);
127   LLDB_LOG(
128       log,
129       "this = {0}, dst = {1}, dst_len = {2}, timeout = {3}, connection = {4}",
130       this, dst, dst_len, timeout, m_connection_sp.get());
131 
132   if (m_read_thread_enabled) {
133     // We have a dedicated read thread that is getting data for us
134     size_t cached_bytes = GetCachedBytes(dst, dst_len);
135     if (cached_bytes > 0 || (timeout && timeout->count() == 0)) {
136       status = eConnectionStatusSuccess;
137       return cached_bytes;
138     }
139 
140     if (!m_connection_sp) {
141       if (error_ptr)
142         error_ptr->SetErrorString("Invalid connection.");
143       status = eConnectionStatusNoConnection;
144       return 0;
145     }
146 
147     ListenerSP listener_sp(Listener::MakeListener("Communication::Read"));
148     listener_sp->StartListeningForEvents(
149         this, eBroadcastBitReadThreadGotBytes | eBroadcastBitReadThreadDidExit);
150     EventSP event_sp;
151     while (listener_sp->GetEvent(event_sp, timeout)) {
152       const uint32_t event_type = event_sp->GetType();
153       if (event_type & eBroadcastBitReadThreadGotBytes) {
154         return GetCachedBytes(dst, dst_len);
155       }
156 
157       if (event_type & eBroadcastBitReadThreadDidExit) {
158         if (GetCloseOnEOF())
159           Disconnect(nullptr);
160         break;
161       }
162     }
163     return 0;
164   }
165 
166   // We aren't using a read thread, just read the data synchronously in this
167   // thread.
168   return ReadFromConnection(dst, dst_len, timeout, status, error_ptr);
169 }
170 
171 size_t Communication::Write(const void *src, size_t src_len,
172                             ConnectionStatus &status, Status *error_ptr) {
173   lldb::ConnectionSP connection_sp(m_connection_sp);
174 
175   std::lock_guard<std::mutex> guard(m_write_mutex);
176   LLDB_LOG(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_COMMUNICATION),
177            "{0} Communication::Write (src = {1}, src_len = %" PRIu64
178            ") connection = {2}",
179            this, src, (uint64_t)src_len, connection_sp.get());
180 
181   if (connection_sp)
182     return connection_sp->Write(src, src_len, status, error_ptr);
183 
184   if (error_ptr)
185     error_ptr->SetErrorString("Invalid connection.");
186   status = eConnectionStatusNoConnection;
187   return 0;
188 }
189 
190 bool Communication::StartReadThread(Status *error_ptr) {
191   if (error_ptr)
192     error_ptr->Clear();
193 
194   if (m_read_thread.IsJoinable())
195     return true;
196 
197   LLDB_LOG(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_COMMUNICATION),
198            "{0} Communication::StartReadThread ()", this);
199 
200   char thread_name[1024];
201   snprintf(thread_name, sizeof(thread_name), "<lldb.comm.%s>",
202            GetBroadcasterName().AsCString());
203 
204   m_read_thread_enabled = true;
205   m_read_thread_did_exit = false;
206   auto maybe_thread = ThreadLauncher::LaunchThread(
207       thread_name, Communication::ReadThread, this);
208   if (maybe_thread) {
209     m_read_thread = *maybe_thread;
210   } else {
211     if (error_ptr)
212       *error_ptr = Status(maybe_thread.takeError());
213     else {
214       LLDB_LOG(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_HOST),
215                "failed to launch host thread: {}",
216                llvm::toString(maybe_thread.takeError()));
217     }
218   }
219 
220   if (!m_read_thread.IsJoinable())
221     m_read_thread_enabled = false;
222 
223   return m_read_thread_enabled;
224 }
225 
226 bool Communication::StopReadThread(Status *error_ptr) {
227   if (!m_read_thread.IsJoinable())
228     return true;
229 
230   LLDB_LOG(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_COMMUNICATION),
231            "{0} Communication::StopReadThread ()", this);
232 
233   m_read_thread_enabled = false;
234 
235   BroadcastEvent(eBroadcastBitReadThreadShouldExit, nullptr);
236 
237   // error = m_read_thread.Cancel();
238 
239   Status error = m_read_thread.Join(nullptr);
240   return error.Success();
241 }
242 
243 bool Communication::JoinReadThread(Status *error_ptr) {
244   if (!m_read_thread.IsJoinable())
245     return true;
246 
247   Status error = m_read_thread.Join(nullptr);
248   return error.Success();
249 }
250 
251 size_t Communication::GetCachedBytes(void *dst, size_t dst_len) {
252   std::lock_guard<std::recursive_mutex> guard(m_bytes_mutex);
253   if (!m_bytes.empty()) {
254     // If DST is nullptr and we have a thread, then return the number of bytes
255     // that are available so the caller can call again
256     if (dst == nullptr)
257       return m_bytes.size();
258 
259     const size_t len = std::min<size_t>(dst_len, m_bytes.size());
260 
261     ::memcpy(dst, m_bytes.c_str(), len);
262     m_bytes.erase(m_bytes.begin(), m_bytes.begin() + len);
263 
264     return len;
265   }
266   return 0;
267 }
268 
269 void Communication::AppendBytesToCache(const uint8_t *bytes, size_t len,
270                                        bool broadcast,
271                                        ConnectionStatus status) {
272   LLDB_LOG(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_COMMUNICATION),
273            "{0} Communication::AppendBytesToCache (src = {1}, src_len = {2}, "
274            "broadcast = {3})",
275            this, bytes, (uint64_t)len, broadcast);
276   if ((bytes == nullptr || len == 0) &&
277       (status != lldb::eConnectionStatusEndOfFile))
278     return;
279   if (m_callback) {
280     // If the user registered a callback, then call it and do not broadcast
281     m_callback(m_callback_baton, bytes, len);
282   } else if (bytes != nullptr && len > 0) {
283     std::lock_guard<std::recursive_mutex> guard(m_bytes_mutex);
284     m_bytes.append((const char *)bytes, len);
285     if (broadcast)
286       BroadcastEventIfUnique(eBroadcastBitReadThreadGotBytes);
287   }
288 }
289 
290 size_t Communication::ReadFromConnection(void *dst, size_t dst_len,
291                                          const Timeout<std::micro> &timeout,
292                                          ConnectionStatus &status,
293                                          Status *error_ptr) {
294   lldb::ConnectionSP connection_sp(m_connection_sp);
295   if (connection_sp)
296     return connection_sp->Read(dst, dst_len, timeout, status, error_ptr);
297 
298   if (error_ptr)
299     error_ptr->SetErrorString("Invalid connection.");
300   status = eConnectionStatusNoConnection;
301   return 0;
302 }
303 
304 bool Communication::ReadThreadIsRunning() { return m_read_thread_enabled; }
305 
306 lldb::thread_result_t Communication::ReadThread(lldb::thread_arg_t p) {
307   Communication *comm = (Communication *)p;
308 
309   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_COMMUNICATION));
310 
311   LLDB_LOGF(log, "%p Communication::ReadThread () thread starting...", p);
312 
313   uint8_t buf[1024];
314 
315   Status error;
316   ConnectionStatus status = eConnectionStatusSuccess;
317   bool done = false;
318   bool disconnect = false;
319   while (!done && comm->m_read_thread_enabled) {
320     size_t bytes_read = comm->ReadFromConnection(
321         buf, sizeof(buf), std::chrono::seconds(5), status, &error);
322     if (bytes_read > 0 || status == eConnectionStatusEndOfFile)
323       comm->AppendBytesToCache(buf, bytes_read, true, status);
324 
325     switch (status) {
326     case eConnectionStatusSuccess:
327       break;
328 
329     case eConnectionStatusEndOfFile:
330       done = true;
331       disconnect = comm->GetCloseOnEOF();
332       break;
333     case eConnectionStatusError: // Check GetError() for details
334       if (error.GetType() == eErrorTypePOSIX && error.GetError() == EIO) {
335         // EIO on a pipe is usually caused by remote shutdown
336         disconnect = comm->GetCloseOnEOF();
337         done = true;
338       }
339       if (error.Fail())
340         LLDB_LOG(log, "error: {0}, status = {1}", error,
341                  Communication::ConnectionStatusAsCString(status));
342       break;
343     case eConnectionStatusInterrupted: // Synchronization signal from
344                                        // SynchronizeWithReadThread()
345       // The connection returns eConnectionStatusInterrupted only when there is
346       // no input pending to be read, so we can signal that.
347       comm->BroadcastEvent(eBroadcastBitNoMorePendingInput);
348       break;
349     case eConnectionStatusNoConnection:   // No connection
350     case eConnectionStatusLostConnection: // Lost connection while connected to
351                                           // a valid connection
352       done = true;
353       LLVM_FALLTHROUGH;
354     case eConnectionStatusTimedOut: // Request timed out
355       if (error.Fail())
356         LLDB_LOG(log, "error: {0}, status = {1}", error,
357                  Communication::ConnectionStatusAsCString(status));
358       break;
359     }
360   }
361   log = lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_COMMUNICATION);
362   if (log)
363     LLDB_LOGF(log, "%p Communication::ReadThread () thread exiting...", p);
364 
365   // Handle threads wishing to synchronize with us.
366   {
367     // Prevent new ones from showing up.
368     comm->m_read_thread_did_exit = true;
369 
370     // Unblock any existing thread waiting for the synchronization signal.
371     comm->BroadcastEvent(eBroadcastBitNoMorePendingInput);
372 
373     // Wait for the thread to finish...
374     std::lock_guard<std::mutex> guard(comm->m_synchronize_mutex);
375     // ... and disconnect.
376     if (disconnect)
377       comm->Disconnect();
378   }
379 
380   // Let clients know that this thread is exiting
381   comm->BroadcastEvent(eBroadcastBitReadThreadDidExit);
382   return {};
383 }
384 
385 void Communication::SetReadThreadBytesReceivedCallback(
386     ReadThreadBytesReceived callback, void *callback_baton) {
387   m_callback = callback;
388   m_callback_baton = callback_baton;
389 }
390 
391 void Communication::SynchronizeWithReadThread() {
392   // Only one thread can do the synchronization dance at a time.
393   std::lock_guard<std::mutex> guard(m_synchronize_mutex);
394 
395   // First start listening for the synchronization event.
396   ListenerSP listener_sp(
397       Listener::MakeListener("Communication::SyncronizeWithReadThread"));
398   listener_sp->StartListeningForEvents(this, eBroadcastBitNoMorePendingInput);
399 
400   // If the thread is not running, there is no point in synchronizing.
401   if (!m_read_thread_enabled || m_read_thread_did_exit)
402     return;
403 
404   // Notify the read thread.
405   m_connection_sp->InterruptRead();
406 
407   // Wait for the synchronization event.
408   EventSP event_sp;
409   listener_sp->GetEvent(event_sp, llvm::None);
410 }
411 
412 void Communication::SetConnection(std::unique_ptr<Connection> connection) {
413   Disconnect(nullptr);
414   StopReadThread(nullptr);
415   m_connection_sp = std::move(connection);
416 }
417 
418 const char *
419 Communication::ConnectionStatusAsCString(lldb::ConnectionStatus status) {
420   switch (status) {
421   case eConnectionStatusSuccess:
422     return "success";
423   case eConnectionStatusError:
424     return "error";
425   case eConnectionStatusTimedOut:
426     return "timed out";
427   case eConnectionStatusNoConnection:
428     return "no connection";
429   case eConnectionStatusLostConnection:
430     return "lost connection";
431   case eConnectionStatusEndOfFile:
432     return "end of file";
433   case eConnectionStatusInterrupted:
434     return "interrupted";
435   }
436 
437   static char unknown_state_string[64];
438   snprintf(unknown_state_string, sizeof(unknown_state_string),
439            "ConnectionStatus = %i", status);
440   return unknown_state_string;
441 }
442