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