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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 <vector>
19#include <algorithm>
20#if HAVE_EXECINFO_H
21# include <execinfo.h>         // For backtrace().
22#endif
23#if HAVE_SIGNAL_H
24#include <signal.h>
25#endif
26#if HAVE_SYS_STAT_H
27#include <sys/stat.h>
28#endif
29#if HAVE_DLFCN_H && __GNUG__
30#include <dlfcn.h>
31#include <cxxabi.h>
32#endif
33#if HAVE_MACH_MACH_H
34#include <mach/mach.h>
35#endif
36
37using namespace llvm;
38
39static RETSIGTYPE SignalHandler(int Sig);  // defined below.
40
41static SmartMutex<true> SignalsMutex;
42
43/// InterruptFunction - The function to call if ctrl-c is pressed.
44static void (*InterruptFunction)() = 0;
45
46static std::vector<sys::Path> FilesToRemove;
47static std::vector<std::pair<void(*)(void*), void*> > CallBacksToRun;
48
49// IntSigs - Signals that may interrupt the program at any time.
50static const int IntSigs[] = {
51  SIGHUP, SIGINT, SIGQUIT, SIGPIPE, SIGTERM, SIGUSR1, SIGUSR2
52};
53static const int *const IntSigsEnd =
54  IntSigs + sizeof(IntSigs) / sizeof(IntSigs[0]);
55
56// KillSigs - Signals that are synchronous with the program that will cause it
57// to die.
58static const int KillSigs[] = {
59  SIGILL, SIGTRAP, SIGABRT, SIGFPE, SIGBUS, SIGSEGV
60#ifdef SIGSYS
61  , SIGSYS
62#endif
63#ifdef SIGXCPU
64  , SIGXCPU
65#endif
66#ifdef SIGXFSZ
67  , SIGXFSZ
68#endif
69#ifdef SIGEMT
70  , SIGEMT
71#endif
72};
73static const int *const KillSigsEnd =
74  KillSigs + sizeof(KillSigs) / sizeof(KillSigs[0]);
75
76static unsigned NumRegisteredSignals = 0;
77static struct {
78  struct sigaction SA;
79  int SigNo;
80} RegisteredSignalInfo[(sizeof(IntSigs)+sizeof(KillSigs))/sizeof(KillSigs[0])];
81
82
83static void RegisterHandler(int Signal) {
84  assert(NumRegisteredSignals <
85         sizeof(RegisteredSignalInfo)/sizeof(RegisteredSignalInfo[0]) &&
86         "Out of space for signal handlers!");
87
88  struct sigaction NewHandler;
89
90  NewHandler.sa_handler = SignalHandler;
91  NewHandler.sa_flags = SA_NODEFER|SA_RESETHAND;
92  sigemptyset(&NewHandler.sa_mask);
93
94  // Install the new handler, save the old one in RegisteredSignalInfo.
95  sigaction(Signal, &NewHandler,
96            &RegisteredSignalInfo[NumRegisteredSignals].SA);
97  RegisteredSignalInfo[NumRegisteredSignals].SigNo = Signal;
98  ++NumRegisteredSignals;
99}
100
101static void RegisterHandlers() {
102  // If the handlers are already registered, we're done.
103  if (NumRegisteredSignals != 0) return;
104
105  std::for_each(IntSigs, IntSigsEnd, RegisterHandler);
106  std::for_each(KillSigs, KillSigsEnd, RegisterHandler);
107}
108
109static void UnregisterHandlers() {
110  // Restore all of the signal handlers to how they were before we showed up.
111  for (unsigned i = 0, e = NumRegisteredSignals; i != e; ++i)
112    sigaction(RegisteredSignalInfo[i].SigNo,
113              &RegisteredSignalInfo[i].SA, 0);
114  NumRegisteredSignals = 0;
115}
116
117
118/// RemoveFilesToRemove - Process the FilesToRemove list. This function
119/// should be called with the SignalsMutex lock held.
120static void RemoveFilesToRemove() {
121  while (!FilesToRemove.empty()) {
122    FilesToRemove.back().eraseFromDisk(true);
123    FilesToRemove.pop_back();
124  }
125}
126
127// SignalHandler - The signal handler that runs.
128static RETSIGTYPE SignalHandler(int Sig) {
129  // Restore the signal behavior to default, so that the program actually
130  // crashes when we return and the signal reissues.  This also ensures that if
131  // we crash in our signal handler that the program will terminate immediately
132  // instead of recursing in the signal handler.
133  UnregisterHandlers();
134
135  // Unmask all potentially blocked kill signals.
136  sigset_t SigMask;
137  sigfillset(&SigMask);
138  sigprocmask(SIG_UNBLOCK, &SigMask, 0);
139
140  SignalsMutex.acquire();
141  RemoveFilesToRemove();
142
143  if (std::find(IntSigs, IntSigsEnd, Sig) != IntSigsEnd) {
144    if (InterruptFunction) {
145      void (*IF)() = InterruptFunction;
146      SignalsMutex.release();
147      InterruptFunction = 0;
148      IF();        // run the interrupt function.
149      return;
150    }
151
152    SignalsMutex.release();
153    raise(Sig);   // Execute the default handler.
154    return;
155  }
156
157  SignalsMutex.release();
158
159  // Otherwise if it is a fault (like SEGV) run any handler.
160  for (unsigned i = 0, e = CallBacksToRun.size(); i != e; ++i)
161    CallBacksToRun[i].first(CallBacksToRun[i].second);
162}
163
164void llvm::sys::RunInterruptHandlers() {
165  SignalsMutex.acquire();
166  RemoveFilesToRemove();
167  SignalsMutex.release();
168}
169
170void llvm::sys::SetInterruptFunction(void (*IF)()) {
171  SignalsMutex.acquire();
172  InterruptFunction = IF;
173  SignalsMutex.release();
174  RegisterHandlers();
175}
176
177// RemoveFileOnSignal - The public API
178bool llvm::sys::RemoveFileOnSignal(const sys::Path &Filename,
179                                   std::string* ErrMsg) {
180  SignalsMutex.acquire();
181  FilesToRemove.push_back(Filename);
182
183  SignalsMutex.release();
184
185  RegisterHandlers();
186  return false;
187}
188
189// DontRemoveFileOnSignal - The public API
190void llvm::sys::DontRemoveFileOnSignal(const sys::Path &Filename) {
191  SignalsMutex.acquire();
192  std::vector<sys::Path>::reverse_iterator I =
193    std::find(FilesToRemove.rbegin(), FilesToRemove.rend(), Filename);
194  if (I != FilesToRemove.rend())
195    FilesToRemove.erase(I.base()-1);
196  SignalsMutex.release();
197}
198
199/// AddSignalHandler - Add a function to be called when a signal is delivered
200/// to the process.  The handler can have a cookie passed to it to identify
201/// what instance of the handler it is.
202void llvm::sys::AddSignalHandler(void (*FnPtr)(void *), void *Cookie) {
203  CallBacksToRun.push_back(std::make_pair(FnPtr, Cookie));
204  RegisterHandlers();
205}
206
207
208// PrintStackTrace - In the case of a program crash or fault, print out a stack
209// trace so that the user has an indication of why and where we died.
210//
211// On glibc systems we have the 'backtrace' function, which works nicely, but
212// doesn't demangle symbols.
213static void PrintStackTrace(void *) {
214#ifdef HAVE_BACKTRACE
215  static void* StackTrace[256];
216  // Use backtrace() to output a backtrace on Linux systems with glibc.
217  int depth = backtrace(StackTrace,
218                        static_cast<int>(array_lengthof(StackTrace)));
219#if HAVE_DLFCN_H && __GNUG__
220  int width = 0;
221  for (int i = 0; i < depth; ++i) {
222    Dl_info dlinfo;
223    dladdr(StackTrace[i], &dlinfo);
224    const char* name = strrchr(dlinfo.dli_fname, '/');
225
226    int nwidth;
227    if (name == NULL) nwidth = strlen(dlinfo.dli_fname);
228    else              nwidth = strlen(name) - 1;
229
230    if (nwidth > width) width = nwidth;
231  }
232
233  for (int i = 0; i < depth; ++i) {
234    Dl_info dlinfo;
235    dladdr(StackTrace[i], &dlinfo);
236
237    fprintf(stderr, "%-2d", i);
238
239    const char* name = strrchr(dlinfo.dli_fname, '/');
240    if (name == NULL) fprintf(stderr, " %-*s", width, dlinfo.dli_fname);
241    else              fprintf(stderr, " %-*s", width, name+1);
242
243    fprintf(stderr, " %#0*lx",
244            (int)(sizeof(void*) * 2) + 2, (unsigned long)StackTrace[i]);
245
246    if (dlinfo.dli_sname != NULL) {
247      int res;
248      fputc(' ', stderr);
249      char* d = abi::__cxa_demangle(dlinfo.dli_sname, NULL, NULL, &res);
250      if (d == NULL) fputs(dlinfo.dli_sname, stderr);
251      else           fputs(d, stderr);
252      free(d);
253
254      fprintf(stderr, " + %tu",(char*)StackTrace[i]-(char*)dlinfo.dli_saddr);
255    }
256    fputc('\n', stderr);
257  }
258#else
259  backtrace_symbols_fd(StackTrace, depth, STDERR_FILENO);
260#endif
261#endif
262}
263
264/// PrintStackTraceOnErrorSignal - When an error signal (such as SIBABRT or
265/// SIGSEGV) is delivered to the process, print a stack trace and then exit.
266void llvm::sys::PrintStackTraceOnErrorSignal() {
267  AddSignalHandler(PrintStackTrace, 0);
268
269#if defined(__APPLE__) && !defined(ANDROID)
270  // Environment variable to disable any kind of crash dialog.
271  if (getenv("LLVM_DISABLE_CRASH_REPORT")) {
272    mach_port_t self = mach_task_self();
273
274    exception_mask_t mask = EXC_MASK_CRASH;
275
276    kern_return_t ret = task_set_exception_ports(self,
277                             mask,
278                             MACH_PORT_NULL,
279                             EXCEPTION_STATE_IDENTITY | MACH_EXCEPTION_CODES,
280                             THREAD_STATE_NONE);
281    (void)ret;
282  }
283#endif
284}
285
286
287/***/
288
289// On Darwin, raise sends a signal to the main thread instead of the current
290// thread. This has the unfortunate effect that assert() and abort() will end up
291// bypassing our crash recovery attempts. We work around this for anything in
292// the same linkage unit by just defining our own versions of the assert handler
293// and abort.
294
295#if defined(__APPLE__) && !defined(ANDROID)
296
297#include <signal.h>
298#include <pthread.h>
299
300int raise(int sig) {
301  return pthread_kill(pthread_self(), sig);
302}
303
304void __assert_rtn(const char *func,
305                  const char *file,
306                  int line,
307                  const char *expr) {
308  if (func)
309    fprintf(stderr, "Assertion failed: (%s), function %s, file %s, line %d.\n",
310            expr, func, file, line);
311  else
312    fprintf(stderr, "Assertion failed: (%s), file %s, line %d.\n",
313            expr, file, line);
314  abort();
315}
316
317void abort() {
318  raise(SIGABRT);
319  usleep(1000);
320  __builtin_trap();
321}
322
323#endif
324