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  // We avoid iterators in case of debug iterators that allocate or release
143  // memory.
144  std::vector<std::string>& FilesToRemoveRef = *FilesToRemove;
145  for (unsigned i = 0, e = FilesToRemoveRef.size(); i != e; ++i) {
146    // We rely on a std::string implementation for which repeated calls to
147    // 'c_str()' don't allocate memory. We pre-call 'c_str()' on all of these
148    // strings to try to ensure this is safe.
149    const char *path = FilesToRemoveRef[i].c_str();
150
151    // Get the status so we can determine if it's a file or directory. If we
152    // can't stat the file, ignore it.
153    struct stat buf;
154    if (stat(path, &buf) != 0)
155      continue;
156
157    // If this is not a regular file, ignore it. We want to prevent removal of
158    // special files like /dev/null, even if the compiler is being run with the
159    // super-user permissions.
160    if (!S_ISREG(buf.st_mode))
161      continue;
162
163    // Otherwise, remove the file. We ignore any errors here as there is nothing
164    // else we can do.
165    unlink(path);
166  }
167}
168
169// SignalHandler - The signal handler that runs.
170static RETSIGTYPE SignalHandler(int Sig) {
171  // Restore the signal behavior to default, so that the program actually
172  // crashes when we return and the signal reissues.  This also ensures that if
173  // we crash in our signal handler that the program will terminate immediately
174  // instead of recursing in the signal handler.
175  UnregisterHandlers();
176
177  // Unmask all potentially blocked kill signals.
178  sigset_t SigMask;
179  sigfillset(&SigMask);
180  sigprocmask(SIG_UNBLOCK, &SigMask, nullptr);
181
182  {
183    unique_lock<SmartMutex<true>> Guard(*SignalsMutex);
184    RemoveFilesToRemove();
185
186    if (std::find(std::begin(IntSigs), std::end(IntSigs), Sig)
187        != std::end(IntSigs)) {
188      if (InterruptFunction) {
189        void (*IF)() = InterruptFunction;
190        Guard.unlock();
191        InterruptFunction = nullptr;
192        IF();        // run the interrupt function.
193        return;
194      }
195
196      Guard.unlock();
197      raise(Sig);   // Execute the default handler.
198      return;
199   }
200  }
201
202  // Otherwise if it is a fault (like SEGV) run any handler.
203  std::vector<std::pair<void (*)(void *), void *>>& CallBacksToRunRef =
204      *CallBacksToRun;
205  for (unsigned i = 0, e = CallBacksToRun->size(); i != e; ++i)
206    CallBacksToRunRef[i].first(CallBacksToRunRef[i].second);
207
208#ifdef __s390__
209  // On S/390, certain signals are delivered with PSW Address pointing to
210  // *after* the faulting instruction.  Simply returning from the signal
211  // handler would continue execution after that point, instead of
212  // re-raising the signal.  Raise the signal manually in those cases.
213  if (Sig == SIGILL || Sig == SIGFPE || Sig == SIGTRAP)
214    raise(Sig);
215#endif
216}
217
218void llvm::sys::RunInterruptHandlers() {
219  sys::SmartScopedLock<true> Guard(*SignalsMutex);
220  RemoveFilesToRemove();
221}
222
223void llvm::sys::SetInterruptFunction(void (*IF)()) {
224  {
225    sys::SmartScopedLock<true> Guard(*SignalsMutex);
226    InterruptFunction = IF;
227  }
228  RegisterHandlers();
229}
230
231// RemoveFileOnSignal - The public API
232bool llvm::sys::RemoveFileOnSignal(StringRef Filename,
233                                   std::string* ErrMsg) {
234  {
235    sys::SmartScopedLock<true> Guard(*SignalsMutex);
236    std::vector<std::string>& FilesToRemoveRef = *FilesToRemove;
237    std::string *OldPtr =
238        FilesToRemoveRef.empty() ? nullptr : &FilesToRemoveRef[0];
239    FilesToRemoveRef.push_back(Filename);
240
241    // We want to call 'c_str()' on every std::string in this vector so that if
242    // the underlying implementation requires a re-allocation, it happens here
243    // rather than inside of the signal handler. If we see the vector grow, we
244    // have to call it on every entry. If it remains in place, we only need to
245    // call it on the latest one.
246    if (OldPtr == &FilesToRemoveRef[0])
247      FilesToRemoveRef.back().c_str();
248    else
249      for (unsigned i = 0, e = FilesToRemoveRef.size(); i != e; ++i)
250        FilesToRemoveRef[i].c_str();
251  }
252
253  RegisterHandlers();
254  return false;
255}
256
257// DontRemoveFileOnSignal - The public API
258void llvm::sys::DontRemoveFileOnSignal(StringRef Filename) {
259  sys::SmartScopedLock<true> Guard(*SignalsMutex);
260  std::vector<std::string>::reverse_iterator RI =
261    std::find(FilesToRemove->rbegin(), FilesToRemove->rend(), Filename);
262  std::vector<std::string>::iterator I = FilesToRemove->end();
263  if (RI != FilesToRemove->rend())
264    I = FilesToRemove->erase(RI.base()-1);
265
266  // We need to call c_str() on every element which would have been moved by
267  // the erase. These elements, in a C++98 implementation where c_str()
268  // requires a reallocation on the first call may have had the call to c_str()
269  // made on insertion become invalid by being copied down an element.
270  for (std::vector<std::string>::iterator E = FilesToRemove->end(); I != E; ++I)
271    I->c_str();
272}
273
274/// AddSignalHandler - Add a function to be called when a signal is delivered
275/// to the process.  The handler can have a cookie passed to it to identify
276/// what instance of the handler it is.
277void llvm::sys::AddSignalHandler(void (*FnPtr)(void *), void *Cookie) {
278  CallBacksToRun->push_back(std::make_pair(FnPtr, Cookie));
279  RegisterHandlers();
280}
281
282#if defined(HAVE_BACKTRACE) && defined(ENABLE_BACKTRACES)
283
284#if HAVE_LINK_H && (defined(__linux__) || defined(__FreeBSD__) ||              \
285                    defined(__FreeBSD_kernel__) || defined(__NetBSD__))
286struct DlIteratePhdrData {
287  void **StackTrace;
288  int depth;
289  bool first;
290  const char **modules;
291  intptr_t *offsets;
292  const char *main_exec_name;
293};
294
295static int dl_iterate_phdr_cb(dl_phdr_info *info, size_t size, void *arg) {
296  DlIteratePhdrData *data = (DlIteratePhdrData*)arg;
297  const char *name = data->first ? data->main_exec_name : info->dlpi_name;
298  data->first = false;
299  for (int i = 0; i < info->dlpi_phnum; i++) {
300    const auto *phdr = &info->dlpi_phdr[i];
301    if (phdr->p_type != PT_LOAD)
302      continue;
303    intptr_t beg = info->dlpi_addr + phdr->p_vaddr;
304    intptr_t end = beg + phdr->p_memsz;
305    for (int j = 0; j < data->depth; j++) {
306      if (data->modules[j])
307        continue;
308      intptr_t addr = (intptr_t)data->StackTrace[j];
309      if (beg <= addr && addr < end) {
310        data->modules[j] = name;
311        data->offsets[j] = addr - info->dlpi_addr;
312      }
313    }
314  }
315  return 0;
316}
317
318static bool findModulesAndOffsets(void **StackTrace, int Depth,
319                                  const char **Modules, intptr_t *Offsets,
320                                  const char *MainExecutableName) {
321  DlIteratePhdrData data = {StackTrace, Depth,   true,
322                            Modules,    Offsets, MainExecutableName};
323  dl_iterate_phdr(dl_iterate_phdr_cb, &data);
324  return true;
325}
326#else
327static bool findModulesAndOffsets(void **StackTrace, int Depth,
328                                  const char **Modules, intptr_t *Offsets,
329                                  const char *MainExecutableName) {
330  return false;
331}
332#endif
333
334static bool printSymbolizedStackTrace(void **StackTrace, int Depth,
335                                      llvm::raw_ostream &OS) {
336  // FIXME: Subtract necessary number from StackTrace entries to turn return addresses
337  // into actual instruction addresses.
338  // Use llvm-symbolizer tool to symbolize the stack traces.
339  ErrorOr<std::string> LLVMSymbolizerPathOrErr =
340      sys::findProgramByName("llvm-symbolizer");
341  if (!LLVMSymbolizerPathOrErr)
342    return false;
343  const std::string &LLVMSymbolizerPath = *LLVMSymbolizerPathOrErr;
344  // We don't know argv0 or the address of main() at this point, but try
345  // to guess it anyway (it's possible on some platforms).
346  std::string MainExecutableName = sys::fs::getMainExecutable(nullptr, nullptr);
347  if (MainExecutableName.empty() ||
348      MainExecutableName.find("llvm-symbolizer") != std::string::npos)
349    return false;
350
351  std::vector<const char *> Modules(Depth, nullptr);
352  std::vector<intptr_t> Offsets(Depth, 0);
353  if (!findModulesAndOffsets(StackTrace, Depth, Modules.data(), Offsets.data(),
354                             MainExecutableName.c_str()))
355    return false;
356  int InputFD;
357  SmallString<32> InputFile, OutputFile;
358  sys::fs::createTemporaryFile("symbolizer-input", "", InputFD, InputFile);
359  sys::fs::createTemporaryFile("symbolizer-output", "", OutputFile);
360  FileRemover InputRemover(InputFile.c_str());
361  FileRemover OutputRemover(OutputFile.c_str());
362
363  {
364    raw_fd_ostream Input(InputFD, true);
365    for (int i = 0; i < Depth; i++) {
366      if (Modules[i])
367        Input << Modules[i] << " " << (void*)Offsets[i] << "\n";
368    }
369  }
370
371  StringRef InputFileStr(InputFile);
372  StringRef OutputFileStr(OutputFile);
373  StringRef StderrFileStr;
374  const StringRef *Redirects[] = {&InputFileStr, &OutputFileStr,
375                                  &StderrFileStr};
376  const char *Args[] = {"llvm-symbolizer", "--functions=linkage", "--inlining",
377                        "--demangle", nullptr};
378  int RunResult =
379      sys::ExecuteAndWait(LLVMSymbolizerPath, Args, nullptr, Redirects);
380  if (RunResult != 0)
381    return false;
382
383  auto OutputBuf = MemoryBuffer::getFile(OutputFile.c_str());
384  if (!OutputBuf)
385    return false;
386  StringRef Output = OutputBuf.get()->getBuffer();
387  SmallVector<StringRef, 32> Lines;
388  Output.split(Lines, "\n");
389  auto CurLine = Lines.begin();
390  int frame_no = 0;
391  for (int i = 0; i < Depth; i++) {
392    if (!Modules[i]) {
393      OS << format("#%d %p\n", frame_no++, StackTrace[i]);
394      continue;
395    }
396    // Read pairs of lines (function name and file/line info) until we
397    // encounter empty line.
398    for (;;) {
399      if (CurLine == Lines.end())
400        return false;
401      StringRef FunctionName = *CurLine++;
402      if (FunctionName.empty())
403        break;
404      OS << format("#%d %p ", frame_no++, StackTrace[i]);
405      if (!FunctionName.startswith("??"))
406        OS << format("%s ", FunctionName.str().c_str());
407      if (CurLine == Lines.end())
408        return false;
409      StringRef FileLineInfo = *CurLine++;
410      if (!FileLineInfo.startswith("??"))
411        OS << format("%s", FileLineInfo.str().c_str());
412      else
413        OS << format("(%s+%p)", Modules[i], (void *)Offsets[i]);
414      OS << "\n";
415    }
416  }
417  return true;
418}
419#endif // defined(HAVE_BACKTRACE) && defined(ENABLE_BACKTRACES)
420
421// PrintStackTrace - In the case of a program crash or fault, print out a stack
422// trace so that the user has an indication of why and where we died.
423//
424// On glibc systems we have the 'backtrace' function, which works nicely, but
425// doesn't demangle symbols.
426void llvm::sys::PrintStackTrace(raw_ostream &OS) {
427#if defined(HAVE_BACKTRACE) && defined(ENABLE_BACKTRACES)
428  static void* StackTrace[256];
429  // Use backtrace() to output a backtrace on Linux systems with glibc.
430  int depth = backtrace(StackTrace,
431                        static_cast<int>(array_lengthof(StackTrace)));
432  if (printSymbolizedStackTrace(StackTrace, depth, OS))
433    return;
434#if HAVE_DLFCN_H && __GNUG__
435  int width = 0;
436  for (int i = 0; i < depth; ++i) {
437    Dl_info dlinfo;
438    dladdr(StackTrace[i], &dlinfo);
439    const char* name = strrchr(dlinfo.dli_fname, '/');
440
441    int nwidth;
442    if (!name) nwidth = strlen(dlinfo.dli_fname);
443    else       nwidth = strlen(name) - 1;
444
445    if (nwidth > width) width = nwidth;
446  }
447
448  for (int i = 0; i < depth; ++i) {
449    Dl_info dlinfo;
450    dladdr(StackTrace[i], &dlinfo);
451
452    OS << format("%-2d", i);
453
454    const char* name = strrchr(dlinfo.dli_fname, '/');
455    if (!name) OS << format(" %-*s", width, dlinfo.dli_fname);
456    else       OS << format(" %-*s", width, name+1);
457
458    OS << format(" %#0*lx", (int)(sizeof(void*) * 2) + 2,
459                 (unsigned long)StackTrace[i]);
460
461    if (dlinfo.dli_sname != nullptr) {
462      OS << ' ';
463#  if HAVE_CXXABI_H
464      int res;
465      char* d = abi::__cxa_demangle(dlinfo.dli_sname, nullptr, nullptr, &res);
466#  else
467      char* d = NULL;
468#  endif
469      if (!d) OS << dlinfo.dli_sname;
470      else    OS << d;
471      free(d);
472
473      // FIXME: When we move to C++11, use %t length modifier. It's not in
474      // C++03 and causes gcc to issue warnings. Losing the upper 32 bits of
475      // the stack offset for a stack dump isn't likely to cause any problems.
476      OS << format(" + %u",(unsigned)((char*)StackTrace[i]-
477                                      (char*)dlinfo.dli_saddr));
478    }
479    OS << '\n';
480  }
481#else
482  backtrace_symbols_fd(StackTrace, depth, STDERR_FILENO);
483#endif
484#endif
485}
486
487static void PrintStackTraceSignalHandler(void *) {
488  PrintStackTrace(llvm::errs());
489}
490
491void llvm::sys::DisableSystemDialogsOnCrash() {}
492
493/// PrintStackTraceOnErrorSignal - When an error signal (such as SIGABRT or
494/// SIGSEGV) is delivered to the process, print a stack trace and then exit.
495void llvm::sys::PrintStackTraceOnErrorSignal(bool DisableCrashReporting) {
496  AddSignalHandler(PrintStackTraceSignalHandler, nullptr);
497
498#if defined(__APPLE__) && defined(ENABLE_CRASH_OVERRIDES)
499  // Environment variable to disable any kind of crash dialog.
500  if (DisableCrashReporting || getenv("LLVM_DISABLE_CRASH_REPORT")) {
501    mach_port_t self = mach_task_self();
502
503    exception_mask_t mask = EXC_MASK_CRASH;
504
505    kern_return_t ret = task_set_exception_ports(self,
506                             mask,
507                             MACH_PORT_NULL,
508                             EXCEPTION_STATE_IDENTITY | MACH_EXCEPTION_CODES,
509                             THREAD_STATE_NONE);
510    (void)ret;
511  }
512#endif
513}
514
515
516/***/
517
518// On Darwin, raise sends a signal to the main thread instead of the current
519// thread. This has the unfortunate effect that assert() and abort() will end up
520// bypassing our crash recovery attempts. We work around this for anything in
521// the same linkage unit by just defining our own versions of the assert handler
522// and abort.
523
524#if defined(__APPLE__) && defined(ENABLE_CRASH_OVERRIDES)
525
526#include <signal.h>
527#include <pthread.h>
528
529int raise(int sig) {
530  return pthread_kill(pthread_self(), sig);
531}
532
533void __assert_rtn(const char *func,
534                  const char *file,
535                  int line,
536                  const char *expr) {
537  if (func)
538    fprintf(stderr, "Assertion failed: (%s), function %s, file %s, line %d.\n",
539            expr, func, file, line);
540  else
541    fprintf(stderr, "Assertion failed: (%s), file %s, line %d.\n",
542            expr, file, line);
543  abort();
544}
545
546void abort() {
547  raise(SIGABRT);
548  usleep(1000);
549  __builtin_trap();
550}
551
552#endif
553