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