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