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//===- Signals.cpp - Generic Unix Signals Implementation -----*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines some helpful functions for dealing with the possibility of
// Unix signals occurring while your program is running.
//
//===----------------------------------------------------------------------===//
#include "Unix.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/Mutex.h"
#include <algorithm>
#include <string>
#include <vector>
#if HAVE_EXECINFO_H
# include <execinfo.h> // For backtrace().
#endif
#if HAVE_SIGNAL_H
#include <signal.h>
#endif
#if HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif
#if HAVE_DLFCN_H && __GNUG__
#include <dlfcn.h>
#include <cxxabi.h>
#endif
#if HAVE_MACH_MACH_H
#include <mach/mach.h>
#endif
using namespace llvm;
static RETSIGTYPE SignalHandler(int Sig); // defined below.
static SmartMutex<true> SignalsMutex;
/// InterruptFunction - The function to call if ctrl-c is pressed.
static void (*InterruptFunction)() = 0;
static std::vector<std::string> FilesToRemove;
static std::vector<std::pair<void(*)(void*), void*> > CallBacksToRun;
// IntSigs - Signals that represent requested termination. There's no bug
// or failure, or if there is, it's not our direct responsibility. For whatever
// reason, our continued execution is no longer desirable.
static const int IntSigs[] = {
SIGHUP, SIGINT, SIGPIPE, SIGTERM, SIGUSR1, SIGUSR2
};
static const int *const IntSigsEnd =
IntSigs + sizeof(IntSigs) / sizeof(IntSigs[0]);
// KillSigs - Signals that represent that we have a bug, and our prompt
// termination has been ordered.
static const int KillSigs[] = {
SIGILL, SIGTRAP, SIGABRT, SIGFPE, SIGBUS, SIGSEGV, SIGQUIT
#ifdef SIGSYS
, SIGSYS
#endif
#ifdef SIGXCPU
, SIGXCPU
#endif
#ifdef SIGXFSZ
, SIGXFSZ
#endif
#ifdef SIGEMT
, SIGEMT
#endif
};
static const int *const KillSigsEnd =
KillSigs + sizeof(KillSigs) / sizeof(KillSigs[0]);
static unsigned NumRegisteredSignals = 0;
static struct {
struct sigaction SA;
int SigNo;
} RegisteredSignalInfo[(sizeof(IntSigs)+sizeof(KillSigs))/sizeof(KillSigs[0])];
static void RegisterHandler(int Signal) {
assert(NumRegisteredSignals <
sizeof(RegisteredSignalInfo)/sizeof(RegisteredSignalInfo[0]) &&
"Out of space for signal handlers!");
struct sigaction NewHandler;
NewHandler.sa_handler = SignalHandler;
NewHandler.sa_flags = SA_NODEFER|SA_RESETHAND;
sigemptyset(&NewHandler.sa_mask);
// Install the new handler, save the old one in RegisteredSignalInfo.
sigaction(Signal, &NewHandler,
&RegisteredSignalInfo[NumRegisteredSignals].SA);
RegisteredSignalInfo[NumRegisteredSignals].SigNo = Signal;
++NumRegisteredSignals;
}
static void RegisterHandlers() {
// If the handlers are already registered, we're done.
if (NumRegisteredSignals != 0) return;
std::for_each(IntSigs, IntSigsEnd, RegisterHandler);
std::for_each(KillSigs, KillSigsEnd, RegisterHandler);
}
static void UnregisterHandlers() {
// Restore all of the signal handlers to how they were before we showed up.
for (unsigned i = 0, e = NumRegisteredSignals; i != e; ++i)
sigaction(RegisteredSignalInfo[i].SigNo,
&RegisteredSignalInfo[i].SA, 0);
NumRegisteredSignals = 0;
}
/// RemoveFilesToRemove - Process the FilesToRemove list. This function
/// should be called with the SignalsMutex lock held.
/// NB: This must be an async signal safe function. It cannot allocate or free
/// memory, even in debug builds.
static void RemoveFilesToRemove() {
// We avoid iterators in case of debug iterators that allocate or release
// memory.
for (unsigned i = 0, e = FilesToRemove.size(); i != e; ++i) {
// We rely on a std::string implementation for which repeated calls to
// 'c_str()' don't allocate memory. We pre-call 'c_str()' on all of these
// strings to try to ensure this is safe.
const char *path = FilesToRemove[i].c_str();
// Get the status so we can determine if it's a file or directory. If we
// can't stat the file, ignore it.
struct stat buf;
if (stat(path, &buf) != 0)
continue;
// If this is not a regular file, ignore it. We want to prevent removal of
// special files like /dev/null, even if the compiler is being run with the
// super-user permissions.
if (!S_ISREG(buf.st_mode))
continue;
// Otherwise, remove the file. We ignore any errors here as there is nothing
// else we can do.
unlink(path);
}
}
// SignalHandler - The signal handler that runs.
static RETSIGTYPE SignalHandler(int Sig) {
// Restore the signal behavior to default, so that the program actually
// crashes when we return and the signal reissues. This also ensures that if
// we crash in our signal handler that the program will terminate immediately
// instead of recursing in the signal handler.
UnregisterHandlers();
// Unmask all potentially blocked kill signals.
sigset_t SigMask;
sigfillset(&SigMask);
sigprocmask(SIG_UNBLOCK, &SigMask, 0);
SignalsMutex.acquire();
RemoveFilesToRemove();
if (std::find(IntSigs, IntSigsEnd, Sig) != IntSigsEnd) {
if (InterruptFunction) {
void (*IF)() = InterruptFunction;
SignalsMutex.release();
InterruptFunction = 0;
IF(); // run the interrupt function.
return;
}
SignalsMutex.release();
raise(Sig); // Execute the default handler.
return;
}
SignalsMutex.release();
// Otherwise if it is a fault (like SEGV) run any handler.
for (unsigned i = 0, e = CallBacksToRun.size(); i != e; ++i)
CallBacksToRun[i].first(CallBacksToRun[i].second);
}
void llvm::sys::RunInterruptHandlers() {
SignalsMutex.acquire();
RemoveFilesToRemove();
SignalsMutex.release();
}
void llvm::sys::SetInterruptFunction(void (*IF)()) {
SignalsMutex.acquire();
InterruptFunction = IF;
SignalsMutex.release();
RegisterHandlers();
}
// RemoveFileOnSignal - The public API
bool llvm::sys::RemoveFileOnSignal(const sys::Path &Filename,
std::string* ErrMsg) {
SignalsMutex.acquire();
std::string *OldPtr = FilesToRemove.empty() ? 0 : &FilesToRemove[0];
FilesToRemove.push_back(Filename.str());
// We want to call 'c_str()' on every std::string in this vector so that if
// the underlying implementation requires a re-allocation, it happens here
// rather than inside of the signal handler. If we see the vector grow, we
// have to call it on every entry. If it remains in place, we only need to
// call it on the latest one.
if (OldPtr == &FilesToRemove[0])
FilesToRemove.back().c_str();
else
for (unsigned i = 0, e = FilesToRemove.size(); i != e; ++i)
FilesToRemove[i].c_str();
SignalsMutex.release();
RegisterHandlers();
return false;
}
// DontRemoveFileOnSignal - The public API
void llvm::sys::DontRemoveFileOnSignal(const sys::Path &Filename) {
SignalsMutex.acquire();
std::vector<std::string>::reverse_iterator RI =
std::find(FilesToRemove.rbegin(), FilesToRemove.rend(), Filename.str());
std::vector<std::string>::iterator I = FilesToRemove.end();
if (RI != FilesToRemove.rend())
I = FilesToRemove.erase(RI.base()-1);
// We need to call c_str() on every element which would have been moved by
// the erase. These elements, in a C++98 implementation where c_str()
// requires a reallocation on the first call may have had the call to c_str()
// made on insertion become invalid by being copied down an element.
for (std::vector<std::string>::iterator E = FilesToRemove.end(); I != E; ++I)
I->c_str();
SignalsMutex.release();
}
/// AddSignalHandler - Add a function to be called when a signal is delivered
/// to the process. The handler can have a cookie passed to it to identify
/// what instance of the handler it is.
void llvm::sys::AddSignalHandler(void (*FnPtr)(void *), void *Cookie) {
CallBacksToRun.push_back(std::make_pair(FnPtr, Cookie));
RegisterHandlers();
}
// PrintStackTrace - In the case of a program crash or fault, print out a stack
// trace so that the user has an indication of why and where we died.
//
// On glibc systems we have the 'backtrace' function, which works nicely, but
// doesn't demangle symbols.
void llvm::sys::PrintStackTrace(FILE *FD) {
#if defined(HAVE_BACKTRACE) && defined(ENABLE_BACKTRACES)
static void* StackTrace[256];
// Use backtrace() to output a backtrace on Linux systems with glibc.
int depth = backtrace(StackTrace,
static_cast<int>(array_lengthof(StackTrace)));
#if HAVE_DLFCN_H && __GNUG__
int width = 0;
for (int i = 0; i < depth; ++i) {
Dl_info dlinfo;
dladdr(StackTrace[i], &dlinfo);
const char* name = strrchr(dlinfo.dli_fname, '/');
int nwidth;
if (name == NULL) nwidth = strlen(dlinfo.dli_fname);
else nwidth = strlen(name) - 1;
if (nwidth > width) width = nwidth;
}
for (int i = 0; i < depth; ++i) {
Dl_info dlinfo;
dladdr(StackTrace[i], &dlinfo);
fprintf(FD, "%-2d", i);
const char* name = strrchr(dlinfo.dli_fname, '/');
if (name == NULL) fprintf(FD, " %-*s", width, dlinfo.dli_fname);
else fprintf(FD, " %-*s", width, name+1);
fprintf(FD, " %#0*lx",
(int)(sizeof(void*) * 2) + 2, (unsigned long)StackTrace[i]);
if (dlinfo.dli_sname != NULL) {
int res;
fputc(' ', FD);
char* d = abi::__cxa_demangle(dlinfo.dli_sname, NULL, NULL, &res);
if (d == NULL) fputs(dlinfo.dli_sname, FD);
else fputs(d, FD);
free(d);
// FIXME: When we move to C++11, use %t length modifier. It's not in
// C++03 and causes gcc to issue warnings. Losing the upper 32 bits of
// the stack offset for a stack dump isn't likely to cause any problems.
fprintf(FD, " + %u",(unsigned)((char*)StackTrace[i]-
(char*)dlinfo.dli_saddr));
}
fputc('\n', FD);
}
#else
backtrace_symbols_fd(StackTrace, depth, STDERR_FILENO);
#endif
#endif
}
static void PrintStackTraceSignalHandler(void *) {
PrintStackTrace(stderr);
}
/// PrintStackTraceOnErrorSignal - When an error signal (such as SIGABRT or
/// SIGSEGV) is delivered to the process, print a stack trace and then exit.
void llvm::sys::PrintStackTraceOnErrorSignal() {
AddSignalHandler(PrintStackTraceSignalHandler, 0);
#if defined(__APPLE__)
// Environment variable to disable any kind of crash dialog.
if (getenv("LLVM_DISABLE_CRASH_REPORT")) {
mach_port_t self = mach_task_self();
exception_mask_t mask = EXC_MASK_CRASH;
kern_return_t ret = task_set_exception_ports(self,
mask,
MACH_PORT_NULL,
EXCEPTION_STATE_IDENTITY | MACH_EXCEPTION_CODES,
THREAD_STATE_NONE);
(void)ret;
}
#endif
}
/***/
// On Darwin, raise sends a signal to the main thread instead of the current
// thread. This has the unfortunate effect that assert() and abort() will end up
// bypassing our crash recovery attempts. We work around this for anything in
// the same linkage unit by just defining our own versions of the assert handler
// and abort.
#ifdef __APPLE__
#include <signal.h>
#include <pthread.h>
int raise(int sig) {
return pthread_kill(pthread_self(), sig);
}
void __assert_rtn(const char *func,
const char *file,
int line,
const char *expr) {
if (func)
fprintf(stderr, "Assertion failed: (%s), function %s, file %s, line %d.\n",
expr, func, file, line);
else
fprintf(stderr, "Assertion failed: (%s), file %s, line %d.\n",
expr, file, line);
abort();
}
void abort() {
raise(SIGABRT);
usleep(1000);
__builtin_trap();
}
#endif