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/Mutex.h"
18#include <algorithm>
19#include <string>
20#include <vector>
21#if HAVE_EXECINFO_H
22# include <execinfo.h>         // For backtrace().
23#endif
24#if HAVE_SIGNAL_H
25#include <signal.h>
26#endif
27#if HAVE_SYS_STAT_H
28#include <sys/stat.h>
29#endif
30#if HAVE_CXXABI_H
31#include <cxxabi.h>
32#endif
33#if HAVE_DLFCN_H
34#include <dlfcn.h>
35#endif
36#if HAVE_MACH_MACH_H
37#include <mach/mach.h>
38#endif
39
40using namespace llvm;
41
42static RETSIGTYPE SignalHandler(int Sig);  // defined below.
43
44static SmartMutex<true> SignalsMutex;
45
46/// InterruptFunction - The function to call if ctrl-c is pressed.
47static void (*InterruptFunction)() = 0;
48
49static std::vector<std::string> FilesToRemove;
50static std::vector<std::pair<void(*)(void*), void*> > CallBacksToRun;
51
52// IntSigs - Signals that represent requested termination. There's no bug
53// or failure, or if there is, it's not our direct responsibility. For whatever
54// reason, our continued execution is no longer desirable.
55static const int IntSigs[] = {
56  SIGHUP, SIGINT, SIGPIPE, SIGTERM, SIGUSR1, SIGUSR2
57};
58static const int *const IntSigsEnd =
59  IntSigs + sizeof(IntSigs) / sizeof(IntSigs[0]);
60
61// KillSigs - Signals that represent that we have a bug, and our prompt
62// termination has been ordered.
63static const int KillSigs[] = {
64  SIGILL, SIGTRAP, SIGABRT, SIGFPE, SIGBUS, SIGSEGV, SIGQUIT
65#ifdef SIGSYS
66  , SIGSYS
67#endif
68#ifdef SIGXCPU
69  , SIGXCPU
70#endif
71#ifdef SIGXFSZ
72  , SIGXFSZ
73#endif
74#ifdef SIGEMT
75  , SIGEMT
76#endif
77};
78static const int *const KillSigsEnd =
79  KillSigs + sizeof(KillSigs) / sizeof(KillSigs[0]);
80
81static unsigned NumRegisteredSignals = 0;
82static struct {
83  struct sigaction SA;
84  int SigNo;
85} RegisteredSignalInfo[(sizeof(IntSigs)+sizeof(KillSigs))/sizeof(KillSigs[0])];
86
87
88static void RegisterHandler(int Signal) {
89  assert(NumRegisteredSignals <
90         sizeof(RegisteredSignalInfo)/sizeof(RegisteredSignalInfo[0]) &&
91         "Out of space for signal handlers!");
92
93  struct sigaction NewHandler;
94
95  NewHandler.sa_handler = SignalHandler;
96  NewHandler.sa_flags = SA_NODEFER|SA_RESETHAND;
97  sigemptyset(&NewHandler.sa_mask);
98
99  // Install the new handler, save the old one in RegisteredSignalInfo.
100  sigaction(Signal, &NewHandler,
101            &RegisteredSignalInfo[NumRegisteredSignals].SA);
102  RegisteredSignalInfo[NumRegisteredSignals].SigNo = Signal;
103  ++NumRegisteredSignals;
104}
105
106static void RegisterHandlers() {
107  // If the handlers are already registered, we're done.
108  if (NumRegisteredSignals != 0) return;
109
110  std::for_each(IntSigs, IntSigsEnd, RegisterHandler);
111  std::for_each(KillSigs, KillSigsEnd, RegisterHandler);
112}
113
114static void UnregisterHandlers() {
115  // Restore all of the signal handlers to how they were before we showed up.
116  for (unsigned i = 0, e = NumRegisteredSignals; i != e; ++i)
117    sigaction(RegisteredSignalInfo[i].SigNo,
118              &RegisteredSignalInfo[i].SA, 0);
119  NumRegisteredSignals = 0;
120}
121
122
123/// RemoveFilesToRemove - Process the FilesToRemove list. This function
124/// should be called with the SignalsMutex lock held.
125/// NB: This must be an async signal safe function. It cannot allocate or free
126/// memory, even in debug builds.
127static void RemoveFilesToRemove() {
128  // We avoid iterators in case of debug iterators that allocate or release
129  // memory.
130  for (unsigned i = 0, e = FilesToRemove.size(); i != e; ++i) {
131    // We rely on a std::string implementation for which repeated calls to
132    // 'c_str()' don't allocate memory. We pre-call 'c_str()' on all of these
133    // strings to try to ensure this is safe.
134    const char *path = FilesToRemove[i].c_str();
135
136    // Get the status so we can determine if it's a file or directory. If we
137    // can't stat the file, ignore it.
138    struct stat buf;
139    if (stat(path, &buf) != 0)
140      continue;
141
142    // If this is not a regular file, ignore it. We want to prevent removal of
143    // special files like /dev/null, even if the compiler is being run with the
144    // super-user permissions.
145    if (!S_ISREG(buf.st_mode))
146      continue;
147
148    // Otherwise, remove the file. We ignore any errors here as there is nothing
149    // else we can do.
150    unlink(path);
151  }
152}
153
154// SignalHandler - The signal handler that runs.
155static RETSIGTYPE SignalHandler(int Sig) {
156  // Restore the signal behavior to default, so that the program actually
157  // crashes when we return and the signal reissues.  This also ensures that if
158  // we crash in our signal handler that the program will terminate immediately
159  // instead of recursing in the signal handler.
160  UnregisterHandlers();
161
162  // Unmask all potentially blocked kill signals.
163  sigset_t SigMask;
164  sigfillset(&SigMask);
165  sigprocmask(SIG_UNBLOCK, &SigMask, 0);
166
167  SignalsMutex.acquire();
168  RemoveFilesToRemove();
169
170  if (std::find(IntSigs, IntSigsEnd, Sig) != IntSigsEnd) {
171    if (InterruptFunction) {
172      void (*IF)() = InterruptFunction;
173      SignalsMutex.release();
174      InterruptFunction = 0;
175      IF();        // run the interrupt function.
176      return;
177    }
178
179    SignalsMutex.release();
180    raise(Sig);   // Execute the default handler.
181    return;
182  }
183
184  SignalsMutex.release();
185
186  // Otherwise if it is a fault (like SEGV) run any handler.
187  for (unsigned i = 0, e = CallBacksToRun.size(); i != e; ++i)
188    CallBacksToRun[i].first(CallBacksToRun[i].second);
189
190#ifdef __s390__
191  // On S/390, certain signals are delivered with PSW Address pointing to
192  // *after* the faulting instruction.  Simply returning from the signal
193  // handler would continue execution after that point, instead of
194  // re-raising the signal.  Raise the signal manually in those cases.
195  if (Sig == SIGILL || Sig == SIGFPE || Sig == SIGTRAP)
196    raise(Sig);
197#endif
198}
199
200void llvm::sys::RunInterruptHandlers() {
201  SignalsMutex.acquire();
202  RemoveFilesToRemove();
203  SignalsMutex.release();
204}
205
206void llvm::sys::SetInterruptFunction(void (*IF)()) {
207  SignalsMutex.acquire();
208  InterruptFunction = IF;
209  SignalsMutex.release();
210  RegisterHandlers();
211}
212
213// RemoveFileOnSignal - The public API
214bool llvm::sys::RemoveFileOnSignal(const sys::Path &Filename,
215                                   std::string* ErrMsg) {
216  SignalsMutex.acquire();
217  std::string *OldPtr = FilesToRemove.empty() ? 0 : &FilesToRemove[0];
218  FilesToRemove.push_back(Filename.str());
219
220  // We want to call 'c_str()' on every std::string in this vector so that if
221  // the underlying implementation requires a re-allocation, it happens here
222  // rather than inside of the signal handler. If we see the vector grow, we
223  // have to call it on every entry. If it remains in place, we only need to
224  // call it on the latest one.
225  if (OldPtr == &FilesToRemove[0])
226    FilesToRemove.back().c_str();
227  else
228    for (unsigned i = 0, e = FilesToRemove.size(); i != e; ++i)
229      FilesToRemove[i].c_str();
230
231  SignalsMutex.release();
232
233  RegisterHandlers();
234  return false;
235}
236
237// DontRemoveFileOnSignal - The public API
238void llvm::sys::DontRemoveFileOnSignal(const sys::Path &Filename) {
239  SignalsMutex.acquire();
240  std::vector<std::string>::reverse_iterator RI =
241    std::find(FilesToRemove.rbegin(), FilesToRemove.rend(), Filename.str());
242  std::vector<std::string>::iterator I = FilesToRemove.end();
243  if (RI != FilesToRemove.rend())
244    I = FilesToRemove.erase(RI.base()-1);
245
246  // We need to call c_str() on every element which would have been moved by
247  // the erase. These elements, in a C++98 implementation where c_str()
248  // requires a reallocation on the first call may have had the call to c_str()
249  // made on insertion become invalid by being copied down an element.
250  for (std::vector<std::string>::iterator E = FilesToRemove.end(); I != E; ++I)
251    I->c_str();
252
253  SignalsMutex.release();
254}
255
256/// AddSignalHandler - Add a function to be called when a signal is delivered
257/// to the process.  The handler can have a cookie passed to it to identify
258/// what instance of the handler it is.
259void llvm::sys::AddSignalHandler(void (*FnPtr)(void *), void *Cookie) {
260  CallBacksToRun.push_back(std::make_pair(FnPtr, Cookie));
261  RegisterHandlers();
262}
263
264
265// PrintStackTrace - In the case of a program crash or fault, print out a stack
266// trace so that the user has an indication of why and where we died.
267//
268// On glibc systems we have the 'backtrace' function, which works nicely, but
269// doesn't demangle symbols.
270void llvm::sys::PrintStackTrace(FILE *FD) {
271#if defined(HAVE_BACKTRACE) && defined(ENABLE_BACKTRACES)
272  static void* StackTrace[256];
273  // Use backtrace() to output a backtrace on Linux systems with glibc.
274  int depth = backtrace(StackTrace,
275                        static_cast<int>(array_lengthof(StackTrace)));
276#if HAVE_DLFCN_H && __GNUG__
277  int width = 0;
278  for (int i = 0; i < depth; ++i) {
279    Dl_info dlinfo;
280    dladdr(StackTrace[i], &dlinfo);
281    const char* name = strrchr(dlinfo.dli_fname, '/');
282
283    int nwidth;
284    if (name == NULL) nwidth = strlen(dlinfo.dli_fname);
285    else              nwidth = strlen(name) - 1;
286
287    if (nwidth > width) width = nwidth;
288  }
289
290  for (int i = 0; i < depth; ++i) {
291    Dl_info dlinfo;
292    dladdr(StackTrace[i], &dlinfo);
293
294    fprintf(FD, "%-2d", i);
295
296    const char* name = strrchr(dlinfo.dli_fname, '/');
297    if (name == NULL) fprintf(FD, " %-*s", width, dlinfo.dli_fname);
298    else              fprintf(FD, " %-*s", width, name+1);
299
300    fprintf(FD, " %#0*lx",
301            (int)(sizeof(void*) * 2) + 2, (unsigned long)StackTrace[i]);
302
303    if (dlinfo.dli_sname != NULL) {
304      fputc(' ', FD);
305#  if HAVE_CXXABI_H
306      int res;
307      char* d = abi::__cxa_demangle(dlinfo.dli_sname, NULL, NULL, &res);
308#  else
309      char* d = NULL;
310#  endif
311      if (d == NULL) fputs(dlinfo.dli_sname, FD);
312      else           fputs(d, FD);
313      free(d);
314
315      // FIXME: When we move to C++11, use %t length modifier. It's not in
316      // C++03 and causes gcc to issue warnings. Losing the upper 32 bits of
317      // the stack offset for a stack dump isn't likely to cause any problems.
318      fprintf(FD, " + %u",(unsigned)((char*)StackTrace[i]-
319                                     (char*)dlinfo.dli_saddr));
320    }
321    fputc('\n', FD);
322  }
323#else
324  backtrace_symbols_fd(StackTrace, depth, STDERR_FILENO);
325#endif
326#endif
327}
328
329static void PrintStackTraceSignalHandler(void *) {
330  PrintStackTrace(stderr);
331}
332
333/// PrintStackTraceOnErrorSignal - When an error signal (such as SIGABRT or
334/// SIGSEGV) is delivered to the process, print a stack trace and then exit.
335void llvm::sys::PrintStackTraceOnErrorSignal() {
336  AddSignalHandler(PrintStackTraceSignalHandler, 0);
337
338#if defined(__APPLE__)
339  // Environment variable to disable any kind of crash dialog.
340  if (getenv("LLVM_DISABLE_CRASH_REPORT")) {
341    mach_port_t self = mach_task_self();
342
343    exception_mask_t mask = EXC_MASK_CRASH;
344
345    kern_return_t ret = task_set_exception_ports(self,
346                             mask,
347                             MACH_PORT_NULL,
348                             EXCEPTION_STATE_IDENTITY | MACH_EXCEPTION_CODES,
349                             THREAD_STATE_NONE);
350    (void)ret;
351  }
352#endif
353}
354
355
356/***/
357
358// On Darwin, raise sends a signal to the main thread instead of the current
359// thread. This has the unfortunate effect that assert() and abort() will end up
360// bypassing our crash recovery attempts. We work around this for anything in
361// the same linkage unit by just defining our own versions of the assert handler
362// and abort.
363
364#ifdef __APPLE__
365
366#include <signal.h>
367#include <pthread.h>
368
369int raise(int sig) {
370  return pthread_kill(pthread_self(), sig);
371}
372
373void __assert_rtn(const char *func,
374                  const char *file,
375                  int line,
376                  const char *expr) {
377  if (func)
378    fprintf(stderr, "Assertion failed: (%s), function %s, file %s, line %d.\n",
379            expr, func, file, line);
380  else
381    fprintf(stderr, "Assertion failed: (%s), file %s, line %d.\n",
382            expr, file, line);
383  abort();
384}
385
386void abort() {
387  raise(SIGABRT);
388  usleep(1000);
389  __builtin_trap();
390}
391
392#endif
393