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1 /*
2  * Copyright (C) 2008 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #include "signal_catcher.h"
18 
19 #include <fcntl.h>
20 #include <pthread.h>
21 #include <signal.h>
22 #include <stdlib.h>
23 #include <sys/stat.h>
24 #include <sys/time.h>
25 #include <sys/types.h>
26 #include <unistd.h>
27 
28 #include <sstream>
29 
30 #include <android-base/stringprintf.h>
31 
32 #if defined(ART_TARGET_ANDROID)
33 #include <tombstoned/tombstoned.h>
34 #endif
35 
36 #include "arch/instruction_set.h"
37 #include "base/file_utils.h"
38 #include "base/logging.h"  // For GetCmdLine.
39 #include "base/os.h"
40 #include "base/time_utils.h"
41 #include "base/unix_file/fd_file.h"
42 #include "base/utils.h"
43 #include "class_linker.h"
44 #include "gc/heap.h"
45 #include "jit/profile_saver.h"
46 #include "runtime.h"
47 #include "scoped_thread_state_change-inl.h"
48 #include "signal_set.h"
49 #include "thread.h"
50 #include "thread_list.h"
51 
52 namespace art {
53 
DumpCmdLine(std::ostream & os)54 static void DumpCmdLine(std::ostream& os) {
55 #if defined(__linux__)
56   // Show the original command line, and the current command line too if it's changed.
57   // On Android, /proc/self/cmdline will have been rewritten to something like "system_server".
58   // Note: The string "Cmd line:" is chosen to match the format used by debuggerd.
59   std::string current_cmd_line;
60   if (ReadFileToString("/proc/self/cmdline", &current_cmd_line)) {
61     current_cmd_line.resize(current_cmd_line.find_last_not_of('\0') + 1);  // trim trailing '\0's
62     std::replace(current_cmd_line.begin(), current_cmd_line.end(), '\0', ' ');
63 
64     os << "Cmd line: " << current_cmd_line << "\n";
65     const char* stashed_cmd_line = GetCmdLine();
66     if (stashed_cmd_line != nullptr && current_cmd_line != stashed_cmd_line
67             && strcmp(stashed_cmd_line, "<unset>") != 0) {
68       os << "Original command line: " << stashed_cmd_line << "\n";
69     }
70   }
71 #else
72   os << "Cmd line: " << GetCmdLine() << "\n";
73 #endif
74 }
75 
SignalCatcher(const std::string & stack_trace_file,bool use_tombstoned_stack_trace_fd)76 SignalCatcher::SignalCatcher(const std::string& stack_trace_file,
77                              bool use_tombstoned_stack_trace_fd)
78     : stack_trace_file_(stack_trace_file),
79       use_tombstoned_stack_trace_fd_(use_tombstoned_stack_trace_fd),
80       lock_("SignalCatcher lock"),
81       cond_("SignalCatcher::cond_", lock_),
82       thread_(nullptr) {
83 #if !defined(ART_TARGET_ANDROID)
84   // We're not running on Android, so we can't communicate with tombstoned
85   // to ask for an open file.
86   CHECK(!use_tombstoned_stack_trace_fd_);
87 #endif
88 
89   SetHaltFlag(false);
90 
91   // Create a raw pthread; its start routine will attach to the runtime.
92   CHECK_PTHREAD_CALL(pthread_create, (&pthread_, nullptr, &Run, this), "signal catcher thread");
93 
94   Thread* self = Thread::Current();
95   MutexLock mu(self, lock_);
96   while (thread_ == nullptr) {
97     cond_.Wait(self);
98   }
99 }
100 
~SignalCatcher()101 SignalCatcher::~SignalCatcher() {
102   // Since we know the thread is just sitting around waiting for signals
103   // to arrive, send it one.
104   SetHaltFlag(true);
105   CHECK_PTHREAD_CALL(pthread_kill, (pthread_, SIGQUIT), "signal catcher shutdown");
106   CHECK_PTHREAD_CALL(pthread_join, (pthread_, nullptr), "signal catcher shutdown");
107 }
108 
SetHaltFlag(bool new_value)109 void SignalCatcher::SetHaltFlag(bool new_value) {
110   MutexLock mu(Thread::Current(), lock_);
111   halt_ = new_value;
112 }
113 
ShouldHalt()114 bool SignalCatcher::ShouldHalt() {
115   MutexLock mu(Thread::Current(), lock_);
116   return halt_;
117 }
118 
OpenStackTraceFile(android::base::unique_fd * tombstone_fd,android::base::unique_fd * output_fd)119 bool SignalCatcher::OpenStackTraceFile(android::base::unique_fd* tombstone_fd,
120                                        android::base::unique_fd* output_fd) {
121   if (use_tombstoned_stack_trace_fd_) {
122 #if defined(ART_TARGET_ANDROID)
123     return tombstoned_connect(getpid(), tombstone_fd, output_fd, kDebuggerdJavaBacktrace);
124 #else
125     UNUSED(tombstone_fd);
126     UNUSED(output_fd);
127 #endif
128   }
129 
130   // The runtime is not configured to dump traces to a file, will LOG(INFO)
131   // instead.
132   if (stack_trace_file_.empty()) {
133     return false;
134   }
135 
136   int fd = open(stack_trace_file_.c_str(), O_APPEND | O_CREAT | O_WRONLY, 0666);
137   if (fd == -1) {
138       PLOG(ERROR) << "Unable to open stack trace file '" << stack_trace_file_ << "'";
139       return false;
140   }
141 
142   output_fd->reset(fd);
143   return true;
144 }
145 
Output(const std::string & s)146 void SignalCatcher::Output(const std::string& s) {
147   android::base::unique_fd tombstone_fd;
148   android::base::unique_fd output_fd;
149   if (!OpenStackTraceFile(&tombstone_fd, &output_fd)) {
150     LOG(INFO) << s;
151     return;
152   }
153 
154   ScopedThreadStateChange tsc(Thread::Current(), kWaitingForSignalCatcherOutput);
155 
156   std::unique_ptr<File> file(new File(output_fd.release(), true /* check_usage */));
157   bool success = file->WriteFully(s.data(), s.size());
158   if (success) {
159     success = file->FlushCloseOrErase() == 0;
160   } else {
161     file->Erase();
162   }
163 
164   const std::string output_path_msg = (use_tombstoned_stack_trace_fd_) ?
165       "[tombstoned]" : stack_trace_file_;
166 
167   if (success) {
168     LOG(INFO) << "Wrote stack traces to '" << output_path_msg << "'";
169   } else {
170     PLOG(ERROR) << "Failed to write stack traces to '" << output_path_msg << "'";
171   }
172 
173 #if defined(ART_TARGET_ANDROID)
174   if (use_tombstoned_stack_trace_fd_ && !tombstoned_notify_completion(tombstone_fd)) {
175     PLOG(WARNING) << "Unable to notify tombstoned of dump completion";
176   }
177 #endif
178 }
179 
HandleSigQuit()180 void SignalCatcher::HandleSigQuit() {
181   Runtime* runtime = Runtime::Current();
182   std::ostringstream os;
183   os << "\n"
184       << "----- pid " << getpid() << " at " << GetIsoDate() << " -----\n";
185 
186   DumpCmdLine(os);
187 
188   // Note: The strings "Build fingerprint:" and "ABI:" are chosen to match the format used by
189   // debuggerd. This allows, for example, the stack tool to work.
190   std::string fingerprint = runtime->GetFingerprint();
191   os << "Build fingerprint: '" << (fingerprint.empty() ? "unknown" : fingerprint) << "'\n";
192   os << "ABI: '" << GetInstructionSetString(runtime->GetInstructionSet()) << "'\n";
193 
194   os << "Build type: " << (kIsDebugBuild ? "debug" : "optimized") << "\n";
195 
196   runtime->DumpForSigQuit(os);
197 
198   if ((false)) {
199     std::string maps;
200     if (ReadFileToString("/proc/self/maps", &maps)) {
201       os << "/proc/self/maps:\n" << maps;
202     }
203   }
204   os << "----- end " << getpid() << " -----\n";
205   Output(os.str());
206 }
207 
HandleSigUsr1()208 void SignalCatcher::HandleSigUsr1() {
209   LOG(INFO) << "SIGUSR1 forcing GC (no HPROF) and profile save";
210   Runtime::Current()->GetHeap()->CollectGarbage(/* clear_soft_references */ false);
211   ProfileSaver::ForceProcessProfiles();
212 }
213 
WaitForSignal(Thread * self,SignalSet & signals)214 int SignalCatcher::WaitForSignal(Thread* self, SignalSet& signals) {
215   ScopedThreadStateChange tsc(self, kWaitingInMainSignalCatcherLoop);
216 
217   // Signals for sigwait() must be blocked but not ignored.  We
218   // block signals like SIGQUIT for all threads, so the condition
219   // is met.  When the signal hits, we wake up, without any signal
220   // handlers being invoked.
221   int signal_number = signals.Wait();
222   if (!ShouldHalt()) {
223     // Let the user know we got the signal, just in case the system's too screwed for us to
224     // actually do what they want us to do...
225     LOG(INFO) << *self << ": reacting to signal " << signal_number;
226 
227     // If anyone's holding locks (which might prevent us from getting back into state Runnable), say so...
228     Runtime::Current()->DumpLockHolders(LOG_STREAM(INFO));
229   }
230 
231   return signal_number;
232 }
233 
Run(void * arg)234 void* SignalCatcher::Run(void* arg) {
235   SignalCatcher* signal_catcher = reinterpret_cast<SignalCatcher*>(arg);
236   CHECK(signal_catcher != nullptr);
237 
238   Runtime* runtime = Runtime::Current();
239   CHECK(runtime->AttachCurrentThread("Signal Catcher", true, runtime->GetSystemThreadGroup(),
240                                      !runtime->IsAotCompiler()));
241 
242   Thread* self = Thread::Current();
243   DCHECK_NE(self->GetState(), kRunnable);
244   {
245     MutexLock mu(self, signal_catcher->lock_);
246     signal_catcher->thread_ = self;
247     signal_catcher->cond_.Broadcast(self);
248   }
249 
250   // Set up mask with signals we want to handle.
251   SignalSet signals;
252   signals.Add(SIGQUIT);
253   signals.Add(SIGUSR1);
254 
255   while (true) {
256     int signal_number = signal_catcher->WaitForSignal(self, signals);
257     if (signal_catcher->ShouldHalt()) {
258       runtime->DetachCurrentThread();
259       return nullptr;
260     }
261 
262     switch (signal_number) {
263     case SIGQUIT:
264       signal_catcher->HandleSigQuit();
265       break;
266     case SIGUSR1:
267       signal_catcher->HandleSigUsr1();
268       break;
269     default:
270       LOG(ERROR) << "Unexpected signal %d" << signal_number;
271       break;
272     }
273   }
274 }
275 
276 }  // namespace art
277