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 && __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  // We 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    // We rely on a std::string implementation for which repeated calls to
128    // 'c_str()' don't allocate memory. We pre-call 'c_str()' on all of these
129    // strings to try to ensure this is safe.
130    const char *path = FilesToRemove[i].c_str();
131
132    // Get the status so we can determine if it's a file or directory. If we
133    // can't stat the file, ignore it.
134    struct stat buf;
135    if (stat(path, &buf) != 0)
136      continue;
137
138    // If this is not a regular file, ignore it. We want to prevent removal of
139    // special files like /dev/null, even if the compiler is being run with the
140    // super-user permissions.
141    if (!S_ISREG(buf.st_mode))
142      continue;
143
144    // Otherwise, remove the file. We ignore any errors here as there is nothing
145    // else we can do.
146    unlink(path);
147  }
148}
149
150// SignalHandler - The signal handler that runs.
151static RETSIGTYPE SignalHandler(int Sig) {
152  // Restore the signal behavior to default, so that the program actually
153  // crashes when we return and the signal reissues.  This also ensures that if
154  // we crash in our signal handler that the program will terminate immediately
155  // instead of recursing in the signal handler.
156  UnregisterHandlers();
157
158  // Unmask all potentially blocked kill signals.
159  sigset_t SigMask;
160  sigfillset(&SigMask);
161  sigprocmask(SIG_UNBLOCK, &SigMask, 0);
162
163  SignalsMutex.acquire();
164  RemoveFilesToRemove();
165
166  if (std::find(IntSigs, IntSigsEnd, Sig) != IntSigsEnd) {
167    if (InterruptFunction) {
168      void (*IF)() = InterruptFunction;
169      SignalsMutex.release();
170      InterruptFunction = 0;
171      IF();        // run the interrupt function.
172      return;
173    }
174
175    SignalsMutex.release();
176    raise(Sig);   // Execute the default handler.
177    return;
178  }
179
180  SignalsMutex.release();
181
182  // Otherwise if it is a fault (like SEGV) run any handler.
183  for (unsigned i = 0, e = CallBacksToRun.size(); i != e; ++i)
184    CallBacksToRun[i].first(CallBacksToRun[i].second);
185}
186
187void llvm::sys::RunInterruptHandlers() {
188  SignalsMutex.acquire();
189  RemoveFilesToRemove();
190  SignalsMutex.release();
191}
192
193void llvm::sys::SetInterruptFunction(void (*IF)()) {
194  SignalsMutex.acquire();
195  InterruptFunction = IF;
196  SignalsMutex.release();
197  RegisterHandlers();
198}
199
200// RemoveFileOnSignal - The public API
201bool llvm::sys::RemoveFileOnSignal(const sys::Path &Filename,
202                                   std::string* ErrMsg) {
203  SignalsMutex.acquire();
204  std::string *OldPtr = FilesToRemove.empty() ? 0 : &FilesToRemove[0];
205  FilesToRemove.push_back(Filename.str());
206
207  // We want to call 'c_str()' on every std::string in this vector so that if
208  // the underlying implementation requires a re-allocation, it happens here
209  // rather than inside of the signal handler. If we see the vector grow, we
210  // have to call it on every entry. If it remains in place, we only need to
211  // call it on the latest one.
212  if (OldPtr == &FilesToRemove[0])
213    FilesToRemove.back().c_str();
214  else
215    for (unsigned i = 0, e = FilesToRemove.size(); i != e; ++i)
216      FilesToRemove[i].c_str();
217
218  SignalsMutex.release();
219
220  RegisterHandlers();
221  return false;
222}
223
224// DontRemoveFileOnSignal - The public API
225void llvm::sys::DontRemoveFileOnSignal(const sys::Path &Filename) {
226  SignalsMutex.acquire();
227  std::vector<std::string>::reverse_iterator RI =
228    std::find(FilesToRemove.rbegin(), FilesToRemove.rend(), Filename.str());
229  std::vector<std::string>::iterator I = FilesToRemove.end();
230  if (RI != FilesToRemove.rend())
231    I = FilesToRemove.erase(RI.base()-1);
232
233  // We need to call c_str() on every element which would have been moved by
234  // the erase. These elements, in a C++98 implementation where c_str()
235  // requires a reallocation on the first call may have had the call to c_str()
236  // made on insertion become invalid by being copied down an element.
237  for (std::vector<std::string>::iterator E = FilesToRemove.end(); I != E; ++I)
238    I->c_str();
239
240  SignalsMutex.release();
241}
242
243/// AddSignalHandler - Add a function to be called when a signal is delivered
244/// to the process.  The handler can have a cookie passed to it to identify
245/// what instance of the handler it is.
246void llvm::sys::AddSignalHandler(void (*FnPtr)(void *), void *Cookie) {
247  CallBacksToRun.push_back(std::make_pair(FnPtr, Cookie));
248  RegisterHandlers();
249}
250
251
252// PrintStackTrace - In the case of a program crash or fault, print out a stack
253// trace so that the user has an indication of why and where we died.
254//
255// On glibc systems we have the 'backtrace' function, which works nicely, but
256// doesn't demangle symbols.
257static void PrintStackTrace(void *) {
258#if defined(HAVE_BACKTRACE) && defined(ENABLE_BACKTRACES)
259  static void* StackTrace[256];
260  // Use backtrace() to output a backtrace on Linux systems with glibc.
261  int depth = backtrace(StackTrace,
262                        static_cast<int>(array_lengthof(StackTrace)));
263#if HAVE_DLFCN_H && __GNUG__
264  int width = 0;
265  for (int i = 0; i < depth; ++i) {
266    Dl_info dlinfo;
267    dladdr(StackTrace[i], &dlinfo);
268    const char* name = strrchr(dlinfo.dli_fname, '/');
269
270    int nwidth;
271    if (name == NULL) nwidth = strlen(dlinfo.dli_fname);
272    else              nwidth = strlen(name) - 1;
273
274    if (nwidth > width) width = nwidth;
275  }
276
277  for (int i = 0; i < depth; ++i) {
278    Dl_info dlinfo;
279    dladdr(StackTrace[i], &dlinfo);
280
281    fprintf(stderr, "%-2d", i);
282
283    const char* name = strrchr(dlinfo.dli_fname, '/');
284    if (name == NULL) fprintf(stderr, " %-*s", width, dlinfo.dli_fname);
285    else              fprintf(stderr, " %-*s", width, name+1);
286
287    fprintf(stderr, " %#0*lx",
288            (int)(sizeof(void*) * 2) + 2, (unsigned long)StackTrace[i]);
289
290    if (dlinfo.dli_sname != NULL) {
291      int res;
292      fputc(' ', stderr);
293      char* d = abi::__cxa_demangle(dlinfo.dli_sname, NULL, NULL, &res);
294      if (d == NULL) fputs(dlinfo.dli_sname, stderr);
295      else           fputs(d, stderr);
296      free(d);
297
298      fprintf(stderr, " + %tu",(char*)StackTrace[i]-(char*)dlinfo.dli_saddr);
299    }
300    fputc('\n', stderr);
301  }
302#else
303  backtrace_symbols_fd(StackTrace, depth, STDERR_FILENO);
304#endif
305#endif
306}
307
308/// PrintStackTraceOnErrorSignal - When an error signal (such as SIGABRT or
309/// SIGSEGV) is delivered to the process, print a stack trace and then exit.
310void llvm::sys::PrintStackTraceOnErrorSignal() {
311  AddSignalHandler(PrintStackTrace, 0);
312
313#if defined(__APPLE__)
314  // Environment variable to disable any kind of crash dialog.
315  if (getenv("LLVM_DISABLE_CRASH_REPORT")) {
316    mach_port_t self = mach_task_self();
317
318    exception_mask_t mask = EXC_MASK_CRASH;
319
320    kern_return_t ret = task_set_exception_ports(self,
321                             mask,
322                             MACH_PORT_NULL,
323                             EXCEPTION_STATE_IDENTITY | MACH_EXCEPTION_CODES,
324                             THREAD_STATE_NONE);
325    (void)ret;
326  }
327#endif
328}
329
330
331/***/
332
333// On Darwin, raise sends a signal to the main thread instead of the current
334// thread. This has the unfortunate effect that assert() and abort() will end up
335// bypassing our crash recovery attempts. We work around this for anything in
336// the same linkage unit by just defining our own versions of the assert handler
337// and abort.
338
339#ifdef __APPLE__
340
341#include <signal.h>
342#include <pthread.h>
343
344int raise(int sig) {
345  return pthread_kill(pthread_self(), sig);
346}
347
348void __assert_rtn(const char *func,
349                  const char *file,
350                  int line,
351                  const char *expr) {
352  if (func)
353    fprintf(stderr, "Assertion failed: (%s), function %s, file %s, line %d.\n",
354            expr, func, file, line);
355  else
356    fprintf(stderr, "Assertion failed: (%s), file %s, line %d.\n",
357            expr, file, line);
358  abort();
359}
360
361void abort() {
362  raise(SIGABRT);
363  usleep(1000);
364  __builtin_trap();
365}
366
367#endif
368