1//===- Signals.cpp - Generic Unix Signals Implementation -----*- 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// This file defines some helpful functions for dealing with the possibility of
11// Unix signals occurring while your program is running.
12//
13//===----------------------------------------------------------------------===//
14
15#include "Unix.h"
16#include "llvm/ADT/STLExtras.h"
17#include "llvm/Support/Format.h"
18#include "llvm/Support/FileSystem.h"
19#include "llvm/Support/FileUtilities.h"
20#include "llvm/Support/ManagedStatic.h"
21#include "llvm/Support/MemoryBuffer.h"
22#include "llvm/Support/Mutex.h"
23#include "llvm/Support/Program.h"
24#include "llvm/Support/UniqueLock.h"
25#include "llvm/Support/raw_ostream.h"
26#include <algorithm>
27#include <string>
28#include <vector>
29#if HAVE_EXECINFO_H
30# include <execinfo.h>         // For backtrace().
31#endif
32#if HAVE_SIGNAL_H
33#include <signal.h>
34#endif
35#if HAVE_SYS_STAT_H
36#include <sys/stat.h>
37#endif
38#if HAVE_CXXABI_H
39#include <cxxabi.h>
40#endif
41#if HAVE_DLFCN_H
42#include <dlfcn.h>
43#endif
44#if HAVE_MACH_MACH_H
45#include <mach/mach.h>
46#endif
47#if HAVE_LINK_H
48#include <link.h>
49#endif
50
51using namespace llvm;
52
53static RETSIGTYPE SignalHandler(int Sig);  // defined below.
54
55static ManagedStatic<SmartMutex<true> > SignalsMutex;
56
57/// InterruptFunction - The function to call if ctrl-c is pressed.
58static void (*InterruptFunction)() = nullptr;
59
60static ManagedStatic<std::vector<std::string>> FilesToRemove;
61static ManagedStatic<std::vector<std::pair<void (*)(void *), void *>>>
62    CallBacksToRun;
63
64// IntSigs - Signals that represent requested termination. There's no bug
65// or failure, or if there is, it's not our direct responsibility. For whatever
66// reason, our continued execution is no longer desirable.
67static const int IntSigs[] = {
68  SIGHUP, SIGINT, SIGPIPE, SIGTERM, SIGUSR1, SIGUSR2
69};
70
71// KillSigs - Signals that represent that we have a bug, and our prompt
72// termination has been ordered.
73static const int KillSigs[] = {
74  SIGILL, SIGTRAP, SIGABRT, SIGFPE, SIGBUS, SIGSEGV, SIGQUIT
75#ifdef SIGSYS
76  , SIGSYS
77#endif
78#ifdef SIGXCPU
79  , SIGXCPU
80#endif
81#ifdef SIGXFSZ
82  , SIGXFSZ
83#endif
84#ifdef SIGEMT
85  , SIGEMT
86#endif
87};
88
89static unsigned NumRegisteredSignals = 0;
90static struct {
91  struct sigaction SA;
92  int SigNo;
93} RegisteredSignalInfo[(sizeof(IntSigs)+sizeof(KillSigs))/sizeof(KillSigs[0])];
94
95
96static void RegisterHandler(int Signal) {
97  assert(NumRegisteredSignals <
98         sizeof(RegisteredSignalInfo)/sizeof(RegisteredSignalInfo[0]) &&
99         "Out of space for signal handlers!");
100
101  struct sigaction NewHandler;
102
103  NewHandler.sa_handler = SignalHandler;
104  NewHandler.sa_flags = SA_NODEFER|SA_RESETHAND;
105  sigemptyset(&NewHandler.sa_mask);
106
107  // Install the new handler, save the old one in RegisteredSignalInfo.
108  sigaction(Signal, &NewHandler,
109            &RegisteredSignalInfo[NumRegisteredSignals].SA);
110  RegisteredSignalInfo[NumRegisteredSignals].SigNo = Signal;
111  ++NumRegisteredSignals;
112}
113
114static void RegisterHandlers() {
115  // We need to dereference the signals mutex during handler registration so
116  // that we force its construction. This is to prevent the first use being
117  // during handling an actual signal because you can't safely call new in a
118  // signal handler.
119  *SignalsMutex;
120
121  // If the handlers are already registered, we're done.
122  if (NumRegisteredSignals != 0) return;
123
124  for (auto S : IntSigs) RegisterHandler(S);
125  for (auto S : KillSigs) RegisterHandler(S);
126}
127
128static void UnregisterHandlers() {
129  // Restore all of the signal handlers to how they were before we showed up.
130  for (unsigned i = 0, e = NumRegisteredSignals; i != e; ++i)
131    sigaction(RegisteredSignalInfo[i].SigNo,
132              &RegisteredSignalInfo[i].SA, nullptr);
133  NumRegisteredSignals = 0;
134}
135
136
137/// RemoveFilesToRemove - Process the FilesToRemove list. This function
138/// should be called with the SignalsMutex lock held.
139/// NB: This must be an async signal safe function. It cannot allocate or free
140/// memory, even in debug builds.
141static void RemoveFilesToRemove() {
142  // Avoid constructing ManagedStatic in the signal handler.
143  // If FilesToRemove is not constructed, there are no files to remove.
144  if (!FilesToRemove.isConstructed())
145    return;
146
147  // We avoid iterators in case of debug iterators that allocate or release
148  // memory.
149  std::vector<std::string>& FilesToRemoveRef = *FilesToRemove;
150  for (unsigned i = 0, e = FilesToRemoveRef.size(); i != e; ++i) {
151    // We rely on a std::string implementation for which repeated calls to
152    // 'c_str()' don't allocate memory. We pre-call 'c_str()' on all of these
153    // strings to try to ensure this is safe.
154    const char *path = FilesToRemoveRef[i].c_str();
155
156    // Get the status so we can determine if it's a file or directory. If we
157    // can't stat the file, ignore it.
158    struct stat buf;
159    if (stat(path, &buf) != 0)
160      continue;
161
162    // If this is not a regular file, ignore it. We want to prevent removal of
163    // special files like /dev/null, even if the compiler is being run with the
164    // super-user permissions.
165    if (!S_ISREG(buf.st_mode))
166      continue;
167
168    // Otherwise, remove the file. We ignore any errors here as there is nothing
169    // else we can do.
170    unlink(path);
171  }
172}
173
174// SignalHandler - The signal handler that runs.
175static RETSIGTYPE SignalHandler(int Sig) {
176  // Restore the signal behavior to default, so that the program actually
177  // crashes when we return and the signal reissues.  This also ensures that if
178  // we crash in our signal handler that the program will terminate immediately
179  // instead of recursing in the signal handler.
180  UnregisterHandlers();
181
182  // Unmask all potentially blocked kill signals.
183  sigset_t SigMask;
184  sigfillset(&SigMask);
185  sigprocmask(SIG_UNBLOCK, &SigMask, nullptr);
186
187  {
188    unique_lock<SmartMutex<true>> Guard(*SignalsMutex);
189    RemoveFilesToRemove();
190
191    if (std::find(std::begin(IntSigs), std::end(IntSigs), Sig)
192        != std::end(IntSigs)) {
193      if (InterruptFunction) {
194        void (*IF)() = InterruptFunction;
195        Guard.unlock();
196        InterruptFunction = nullptr;
197        IF();        // run the interrupt function.
198        return;
199      }
200
201      Guard.unlock();
202      raise(Sig);   // Execute the default handler.
203      return;
204   }
205  }
206
207  // Otherwise if it is a fault (like SEGV) run any handler.
208  if (CallBacksToRun.isConstructed()) {
209    auto &CallBacksToRunRef = *CallBacksToRun;
210    for (unsigned i = 0, e = CallBacksToRun->size(); i != e; ++i)
211      CallBacksToRunRef[i].first(CallBacksToRunRef[i].second);
212  }
213
214#ifdef __s390__
215  // On S/390, certain signals are delivered with PSW Address pointing to
216  // *after* the faulting instruction.  Simply returning from the signal
217  // handler would continue execution after that point, instead of
218  // re-raising the signal.  Raise the signal manually in those cases.
219  if (Sig == SIGILL || Sig == SIGFPE || Sig == SIGTRAP)
220    raise(Sig);
221#endif
222}
223
224void llvm::sys::RunInterruptHandlers() {
225  sys::SmartScopedLock<true> Guard(*SignalsMutex);
226  RemoveFilesToRemove();
227}
228
229void llvm::sys::SetInterruptFunction(void (*IF)()) {
230  {
231    sys::SmartScopedLock<true> Guard(*SignalsMutex);
232    InterruptFunction = IF;
233  }
234  RegisterHandlers();
235}
236
237// RemoveFileOnSignal - The public API
238bool llvm::sys::RemoveFileOnSignal(StringRef Filename,
239                                   std::string* ErrMsg) {
240  {
241    sys::SmartScopedLock<true> Guard(*SignalsMutex);
242    std::vector<std::string>& FilesToRemoveRef = *FilesToRemove;
243    std::string *OldPtr =
244        FilesToRemoveRef.empty() ? nullptr : &FilesToRemoveRef[0];
245    FilesToRemoveRef.push_back(Filename);
246
247    // We want to call 'c_str()' on every std::string in this vector so that if
248    // the underlying implementation requires a re-allocation, it happens here
249    // rather than inside of the signal handler. If we see the vector grow, we
250    // have to call it on every entry. If it remains in place, we only need to
251    // call it on the latest one.
252    if (OldPtr == &FilesToRemoveRef[0])
253      FilesToRemoveRef.back().c_str();
254    else
255      for (unsigned i = 0, e = FilesToRemoveRef.size(); i != e; ++i)
256        FilesToRemoveRef[i].c_str();
257  }
258
259  RegisterHandlers();
260  return false;
261}
262
263// DontRemoveFileOnSignal - The public API
264void llvm::sys::DontRemoveFileOnSignal(StringRef Filename) {
265  sys::SmartScopedLock<true> Guard(*SignalsMutex);
266  std::vector<std::string>::reverse_iterator RI =
267    std::find(FilesToRemove->rbegin(), FilesToRemove->rend(), Filename);
268  std::vector<std::string>::iterator I = FilesToRemove->end();
269  if (RI != FilesToRemove->rend())
270    I = FilesToRemove->erase(RI.base()-1);
271
272  // We need to call c_str() on every element which would have been moved by
273  // the erase. These elements, in a C++98 implementation where c_str()
274  // requires a reallocation on the first call may have had the call to c_str()
275  // made on insertion become invalid by being copied down an element.
276  for (std::vector<std::string>::iterator E = FilesToRemove->end(); I != E; ++I)
277    I->c_str();
278}
279
280/// AddSignalHandler - Add a function to be called when a signal is delivered
281/// to the process.  The handler can have a cookie passed to it to identify
282/// what instance of the handler it is.
283void llvm::sys::AddSignalHandler(void (*FnPtr)(void *), void *Cookie) {
284  CallBacksToRun->push_back(std::make_pair(FnPtr, Cookie));
285  RegisterHandlers();
286}
287
288#if defined(HAVE_BACKTRACE) && defined(ENABLE_BACKTRACES)
289
290#if HAVE_LINK_H && (defined(__linux__) || defined(__FreeBSD__) ||              \
291                    defined(__FreeBSD_kernel__) || defined(__NetBSD__))
292struct DlIteratePhdrData {
293  void **StackTrace;
294  int depth;
295  bool first;
296  const char **modules;
297  intptr_t *offsets;
298  const char *main_exec_name;
299};
300
301static int dl_iterate_phdr_cb(dl_phdr_info *info, size_t size, void *arg) {
302  DlIteratePhdrData *data = (DlIteratePhdrData*)arg;
303  const char *name = data->first ? data->main_exec_name : info->dlpi_name;
304  data->first = false;
305  for (int i = 0; i < info->dlpi_phnum; i++) {
306    const auto *phdr = &info->dlpi_phdr[i];
307    if (phdr->p_type != PT_LOAD)
308      continue;
309    intptr_t beg = info->dlpi_addr + phdr->p_vaddr;
310    intptr_t end = beg + phdr->p_memsz;
311    for (int j = 0; j < data->depth; j++) {
312      if (data->modules[j])
313        continue;
314      intptr_t addr = (intptr_t)data->StackTrace[j];
315      if (beg <= addr && addr < end) {
316        data->modules[j] = name;
317        data->offsets[j] = addr - info->dlpi_addr;
318      }
319    }
320  }
321  return 0;
322}
323
324static bool findModulesAndOffsets(void **StackTrace, int Depth,
325                                  const char **Modules, intptr_t *Offsets,
326                                  const char *MainExecutableName) {
327  DlIteratePhdrData data = {StackTrace, Depth,   true,
328                            Modules,    Offsets, MainExecutableName};
329  dl_iterate_phdr(dl_iterate_phdr_cb, &data);
330  return true;
331}
332#else
333static bool findModulesAndOffsets(void **StackTrace, int Depth,
334                                  const char **Modules, intptr_t *Offsets,
335                                  const char *MainExecutableName) {
336  return false;
337}
338#endif
339
340static bool printSymbolizedStackTrace(void **StackTrace, int Depth,
341                                      llvm::raw_ostream &OS) {
342  // FIXME: Subtract necessary number from StackTrace entries to turn return addresses
343  // into actual instruction addresses.
344  // Use llvm-symbolizer tool to symbolize the stack traces.
345  ErrorOr<std::string> LLVMSymbolizerPathOrErr =
346      sys::findProgramByName("llvm-symbolizer");
347  if (!LLVMSymbolizerPathOrErr)
348    return false;
349  const std::string &LLVMSymbolizerPath = *LLVMSymbolizerPathOrErr;
350  // We don't know argv0 or the address of main() at this point, but try
351  // to guess it anyway (it's possible on some platforms).
352  std::string MainExecutableName = sys::fs::getMainExecutable(nullptr, nullptr);
353  if (MainExecutableName.empty() ||
354      MainExecutableName.find("llvm-symbolizer") != std::string::npos)
355    return false;
356
357  std::vector<const char *> Modules(Depth, nullptr);
358  std::vector<intptr_t> Offsets(Depth, 0);
359  if (!findModulesAndOffsets(StackTrace, Depth, Modules.data(), Offsets.data(),
360                             MainExecutableName.c_str()))
361    return false;
362  int InputFD;
363  SmallString<32> InputFile, OutputFile;
364  sys::fs::createTemporaryFile("symbolizer-input", "", InputFD, InputFile);
365  sys::fs::createTemporaryFile("symbolizer-output", "", OutputFile);
366  FileRemover InputRemover(InputFile.c_str());
367  FileRemover OutputRemover(OutputFile.c_str());
368
369  {
370    raw_fd_ostream Input(InputFD, true);
371    for (int i = 0; i < Depth; i++) {
372      if (Modules[i])
373        Input << Modules[i] << " " << (void*)Offsets[i] << "\n";
374    }
375  }
376
377  StringRef InputFileStr(InputFile);
378  StringRef OutputFileStr(OutputFile);
379  StringRef StderrFileStr;
380  const StringRef *Redirects[] = {&InputFileStr, &OutputFileStr,
381                                  &StderrFileStr};
382  const char *Args[] = {"llvm-symbolizer", "--functions=linkage", "--inlining",
383                        "--demangle", nullptr};
384  int RunResult =
385      sys::ExecuteAndWait(LLVMSymbolizerPath, Args, nullptr, Redirects);
386  if (RunResult != 0)
387    return false;
388
389  auto OutputBuf = MemoryBuffer::getFile(OutputFile.c_str());
390  if (!OutputBuf)
391    return false;
392  StringRef Output = OutputBuf.get()->getBuffer();
393  SmallVector<StringRef, 32> Lines;
394  Output.split(Lines, "\n");
395  auto CurLine = Lines.begin();
396  int frame_no = 0;
397  for (int i = 0; i < Depth; i++) {
398    if (!Modules[i]) {
399      OS << format("#%d %p\n", frame_no++, StackTrace[i]);
400      continue;
401    }
402    // Read pairs of lines (function name and file/line info) until we
403    // encounter empty line.
404    for (;;) {
405      if (CurLine == Lines.end())
406        return false;
407      StringRef FunctionName = *CurLine++;
408      if (FunctionName.empty())
409        break;
410      OS << format("#%d %p ", frame_no++, StackTrace[i]);
411      if (!FunctionName.startswith("??"))
412        OS << format("%s ", FunctionName.str().c_str());
413      if (CurLine == Lines.end())
414        return false;
415      StringRef FileLineInfo = *CurLine++;
416      if (!FileLineInfo.startswith("??"))
417        OS << format("%s", FileLineInfo.str().c_str());
418      else
419        OS << format("(%s+%p)", Modules[i], (void *)Offsets[i]);
420      OS << "\n";
421    }
422  }
423  return true;
424}
425#endif // defined(HAVE_BACKTRACE) && defined(ENABLE_BACKTRACES)
426
427// PrintStackTrace - In the case of a program crash or fault, print out a stack
428// trace so that the user has an indication of why and where we died.
429//
430// On glibc systems we have the 'backtrace' function, which works nicely, but
431// doesn't demangle symbols.
432void llvm::sys::PrintStackTrace(raw_ostream &OS) {
433#if defined(HAVE_BACKTRACE) && defined(ENABLE_BACKTRACES)
434  static void* StackTrace[256];
435  // Use backtrace() to output a backtrace on Linux systems with glibc.
436  int depth = backtrace(StackTrace,
437                        static_cast<int>(array_lengthof(StackTrace)));
438  if (printSymbolizedStackTrace(StackTrace, depth, OS))
439    return;
440#if HAVE_DLFCN_H && __GNUG__
441  int width = 0;
442  for (int i = 0; i < depth; ++i) {
443    Dl_info dlinfo;
444    dladdr(StackTrace[i], &dlinfo);
445    const char* name = strrchr(dlinfo.dli_fname, '/');
446
447    int nwidth;
448    if (!name) nwidth = strlen(dlinfo.dli_fname);
449    else       nwidth = strlen(name) - 1;
450
451    if (nwidth > width) width = nwidth;
452  }
453
454  for (int i = 0; i < depth; ++i) {
455    Dl_info dlinfo;
456    dladdr(StackTrace[i], &dlinfo);
457
458    OS << format("%-2d", i);
459
460    const char* name = strrchr(dlinfo.dli_fname, '/');
461    if (!name) OS << format(" %-*s", width, dlinfo.dli_fname);
462    else       OS << format(" %-*s", width, name+1);
463
464    OS << format(" %#0*lx", (int)(sizeof(void*) * 2) + 2,
465                 (unsigned long)StackTrace[i]);
466
467    if (dlinfo.dli_sname != nullptr) {
468      OS << ' ';
469#  if HAVE_CXXABI_H
470      int res;
471      char* d = abi::__cxa_demangle(dlinfo.dli_sname, nullptr, nullptr, &res);
472#  else
473      char* d = NULL;
474#  endif
475      if (!d) OS << dlinfo.dli_sname;
476      else    OS << d;
477      free(d);
478
479      // FIXME: When we move to C++11, use %t length modifier. It's not in
480      // C++03 and causes gcc to issue warnings. Losing the upper 32 bits of
481      // the stack offset for a stack dump isn't likely to cause any problems.
482      OS << format(" + %u",(unsigned)((char*)StackTrace[i]-
483                                      (char*)dlinfo.dli_saddr));
484    }
485    OS << '\n';
486  }
487#else
488  backtrace_symbols_fd(StackTrace, depth, STDERR_FILENO);
489#endif
490#endif
491}
492
493static void PrintStackTraceSignalHandler(void *) {
494  PrintStackTrace(llvm::errs());
495}
496
497void llvm::sys::DisableSystemDialogsOnCrash() {}
498
499/// PrintStackTraceOnErrorSignal - When an error signal (such as SIGABRT or
500/// SIGSEGV) is delivered to the process, print a stack trace and then exit.
501void llvm::sys::PrintStackTraceOnErrorSignal(bool DisableCrashReporting) {
502  AddSignalHandler(PrintStackTraceSignalHandler, nullptr);
503
504#if defined(__APPLE__) && defined(ENABLE_CRASH_OVERRIDES)
505  // Environment variable to disable any kind of crash dialog.
506  if (DisableCrashReporting || getenv("LLVM_DISABLE_CRASH_REPORT")) {
507    mach_port_t self = mach_task_self();
508
509    exception_mask_t mask = EXC_MASK_CRASH;
510
511    kern_return_t ret = task_set_exception_ports(self,
512                             mask,
513                             MACH_PORT_NULL,
514                             EXCEPTION_STATE_IDENTITY | MACH_EXCEPTION_CODES,
515                             THREAD_STATE_NONE);
516    (void)ret;
517  }
518#endif
519}
520
521
522/***/
523
524// On Darwin, raise sends a signal to the main thread instead of the current
525// thread. This has the unfortunate effect that assert() and abort() will end up
526// bypassing our crash recovery attempts. We work around this for anything in
527// the same linkage unit by just defining our own versions of the assert handler
528// and abort.
529
530#if defined(__APPLE__) && defined(ENABLE_CRASH_OVERRIDES)
531
532#include <signal.h>
533#include <pthread.h>
534
535int raise(int sig) {
536  return pthread_kill(pthread_self(), sig);
537}
538
539void __assert_rtn(const char *func,
540                  const char *file,
541                  int line,
542                  const char *expr) {
543  if (func)
544    fprintf(stderr, "Assertion failed: (%s), function %s, file %s, line %d.\n",
545            expr, func, file, line);
546  else
547    fprintf(stderr, "Assertion failed: (%s), file %s, line %d.\n",
548            expr, file, line);
549  abort();
550}
551
552void abort() {
553  raise(SIGABRT);
554  usleep(1000);
555  __builtin_trap();
556}
557
558#endif
559