//===- 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/Demangle/Demangle.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/FileUtilities.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Mutex.h"
#include "llvm/Support/Program.h"
#include "llvm/Support/UniqueLock.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <string>
#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
#include <dlfcn.h>
#endif
#if HAVE_MACH_MACH_H
#include <mach/mach.h>
#endif
#if HAVE_LINK_H
#include <link.h>
#endif
#ifdef HAVE__UNWIND_BACKTRACE
// FIXME: We should be able to use <unwind.h> for any target that has an
// _Unwind_Backtrace function, but on FreeBSD the configure test passes
// despite the function not existing, and on Android, <unwind.h> conflicts
// with <link.h>.
#if defined(__GLIBC__) || defined(__APPLE__)
#include <unwind.h>
#else
#undef HAVE__UNWIND_BACKTRACE
#endif
#endif
using namespace llvm;
static RETSIGTYPE SignalHandler(int Sig); // defined below.
static ManagedStatic<SmartMutex<true> > SignalsMutex;
/// InterruptFunction - The function to call if ctrl-c is pressed.
static void (*InterruptFunction)() = nullptr;
static ManagedStatic<std::vector<std::string>> FilesToRemove;
static StringRef Argv0;
// 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
};
// 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 unsigned NumRegisteredSignals = 0;
static struct {
struct sigaction SA;
int SigNo;
} RegisteredSignalInfo[array_lengthof(IntSigs) + array_lengthof(KillSigs)];
static void RegisterHandler(int Signal) {
assert(NumRegisteredSignals < array_lengthof(RegisteredSignalInfo) &&
"Out of space for signal handlers!");
struct sigaction NewHandler;
NewHandler.sa_handler = SignalHandler;
NewHandler.sa_flags = SA_NODEFER | SA_RESETHAND | SA_ONSTACK;
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;
}
#if defined(HAVE_SIGALTSTACK)
// Hold onto both the old and new alternate signal stack so that it's not
// reported as a leak. We don't make any attempt to remove our alt signal
// stack if we remove our signal handlers; that can't be done reliably if
// someone else is also trying to do the same thing.
static stack_t OldAltStack;
static void* NewAltStackPointer;
static void CreateSigAltStack() {
const size_t AltStackSize = MINSIGSTKSZ + 64 * 1024;
// If we're executing on the alternate stack, or we already have an alternate
// signal stack that we're happy with, there's nothing for us to do. Don't
// reduce the size, some other part of the process might need a larger stack
// than we do.
if (sigaltstack(nullptr, &OldAltStack) != 0 ||
OldAltStack.ss_flags & SS_ONSTACK ||
(OldAltStack.ss_sp && OldAltStack.ss_size >= AltStackSize))
return;
stack_t AltStack = {};
AltStack.ss_sp = reinterpret_cast<char *>(malloc(AltStackSize));
NewAltStackPointer = AltStack.ss_sp; // Save to avoid reporting a leak.
AltStack.ss_size = AltStackSize;
if (sigaltstack(&AltStack, &OldAltStack) != 0)
free(AltStack.ss_sp);
}
#else
static void CreateSigAltStack() {}
#endif
static void RegisterHandlers() {
// We need to dereference the signals mutex during handler registration so
// that we force its construction. This is to prevent the first use being
// during handling an actual signal because you can't safely call new in a
// signal handler.
*SignalsMutex;
// If the handlers are already registered, we're done.
if (NumRegisteredSignals != 0) return;
// Create an alternate stack for signal handling. This is necessary for us to
// be able to reliably handle signals due to stack overflow.
CreateSigAltStack();
for (auto S : IntSigs) RegisterHandler(S);
for (auto S : KillSigs) RegisterHandler(S);
}
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, nullptr);
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() {
// Avoid constructing ManagedStatic in the signal handler.
// If FilesToRemove is not constructed, there are no files to remove.
if (!FilesToRemove.isConstructed())
return;
// We avoid iterators in case of debug iterators that allocate or release
// memory.
std::vector<std::string>& FilesToRemoveRef = *FilesToRemove;
for (unsigned i = 0, e = FilesToRemoveRef.size(); i != e; ++i) {
const char *path = FilesToRemoveRef[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, nullptr);
{
unique_lock<SmartMutex<true>> Guard(*SignalsMutex);
RemoveFilesToRemove();
if (std::find(std::begin(IntSigs), std::end(IntSigs), Sig)
!= std::end(IntSigs)) {
if (InterruptFunction) {
void (*IF)() = InterruptFunction;
Guard.unlock();
InterruptFunction = nullptr;
IF(); // run the interrupt function.
return;
}
Guard.unlock();
raise(Sig); // Execute the default handler.
return;
}
}
// Otherwise if it is a fault (like SEGV) run any handler.
llvm::sys::RunSignalHandlers();
#ifdef __s390__
// On S/390, certain signals are delivered with PSW Address pointing to
// *after* the faulting instruction. Simply returning from the signal
// handler would continue execution after that point, instead of
// re-raising the signal. Raise the signal manually in those cases.
if (Sig == SIGILL || Sig == SIGFPE || Sig == SIGTRAP)
raise(Sig);
#endif
}
void llvm::sys::RunInterruptHandlers() {
sys::SmartScopedLock<true> Guard(*SignalsMutex);
RemoveFilesToRemove();
}
void llvm::sys::SetInterruptFunction(void (*IF)()) {
{
sys::SmartScopedLock<true> Guard(*SignalsMutex);
InterruptFunction = IF;
}
RegisterHandlers();
}
// RemoveFileOnSignal - The public API
bool llvm::sys::RemoveFileOnSignal(StringRef Filename,
std::string* ErrMsg) {
{
sys::SmartScopedLock<true> Guard(*SignalsMutex);
FilesToRemove->push_back(Filename);
}
RegisterHandlers();
return false;
}
// DontRemoveFileOnSignal - The public API
void llvm::sys::DontRemoveFileOnSignal(StringRef Filename) {
sys::SmartScopedLock<true> Guard(*SignalsMutex);
std::vector<std::string>::reverse_iterator RI =
find(reverse(*FilesToRemove), Filename);
std::vector<std::string>::iterator I = FilesToRemove->end();
if (RI != FilesToRemove->rend())
I = FilesToRemove->erase(RI.base()-1);
}
/// 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();
}
#if defined(HAVE_BACKTRACE) && ENABLE_BACKTRACES && HAVE_LINK_H && \
(defined(__linux__) || defined(__FreeBSD__) || \
defined(__FreeBSD_kernel__) || defined(__NetBSD__))
struct DlIteratePhdrData {
void **StackTrace;
int depth;
bool first;
const char **modules;
intptr_t *offsets;
const char *main_exec_name;
};
static int dl_iterate_phdr_cb(dl_phdr_info *info, size_t size, void *arg) {
DlIteratePhdrData *data = (DlIteratePhdrData*)arg;
const char *name = data->first ? data->main_exec_name : info->dlpi_name;
data->first = false;
for (int i = 0; i < info->dlpi_phnum; i++) {
const auto *phdr = &info->dlpi_phdr[i];
if (phdr->p_type != PT_LOAD)
continue;
intptr_t beg = info->dlpi_addr + phdr->p_vaddr;
intptr_t end = beg + phdr->p_memsz;
for (int j = 0; j < data->depth; j++) {
if (data->modules[j])
continue;
intptr_t addr = (intptr_t)data->StackTrace[j];
if (beg <= addr && addr < end) {
data->modules[j] = name;
data->offsets[j] = addr - info->dlpi_addr;
}
}
}
return 0;
}
/// If this is an ELF platform, we can find all loaded modules and their virtual
/// addresses with dl_iterate_phdr.
static bool findModulesAndOffsets(void **StackTrace, int Depth,
const char **Modules, intptr_t *Offsets,
const char *MainExecutableName,
StringSaver &StrPool) {
DlIteratePhdrData data = {StackTrace, Depth, true,
Modules, Offsets, MainExecutableName};
dl_iterate_phdr(dl_iterate_phdr_cb, &data);
return true;
}
#else
/// This platform does not have dl_iterate_phdr, so we do not yet know how to
/// find all loaded DSOs.
static bool findModulesAndOffsets(void **StackTrace, int Depth,
const char **Modules, intptr_t *Offsets,
const char *MainExecutableName,
StringSaver &StrPool) {
return false;
}
#endif // defined(HAVE_BACKTRACE) && ENABLE_BACKTRACES && ...
#if ENABLE_BACKTRACES && defined(HAVE__UNWIND_BACKTRACE)
static int unwindBacktrace(void **StackTrace, int MaxEntries) {
if (MaxEntries < 0)
return 0;
// Skip the first frame ('unwindBacktrace' itself).
int Entries = -1;
auto HandleFrame = [&](_Unwind_Context *Context) -> _Unwind_Reason_Code {
// Apparently we need to detect reaching the end of the stack ourselves.
void *IP = (void *)_Unwind_GetIP(Context);
if (!IP)
return _URC_END_OF_STACK;
assert(Entries < MaxEntries && "recursively called after END_OF_STACK?");
if (Entries >= 0)
StackTrace[Entries] = IP;
if (++Entries == MaxEntries)
return _URC_END_OF_STACK;
return _URC_NO_REASON;
};
_Unwind_Backtrace(
[](_Unwind_Context *Context, void *Handler) {
return (*static_cast<decltype(HandleFrame) *>(Handler))(Context);
},
static_cast<void *>(&HandleFrame));
return std::max(Entries, 0);
}
#endif
// 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(raw_ostream &OS) {
#if ENABLE_BACKTRACES
static void *StackTrace[256];
int depth = 0;
#if defined(HAVE_BACKTRACE)
// Use backtrace() to output a backtrace on Linux systems with glibc.
if (!depth)
depth = backtrace(StackTrace, static_cast<int>(array_lengthof(StackTrace)));
#endif
#if defined(HAVE__UNWIND_BACKTRACE)
// Try _Unwind_Backtrace() if backtrace() failed.
if (!depth)
depth = unwindBacktrace(StackTrace,
static_cast<int>(array_lengthof(StackTrace)));
#endif
if (!depth)
return;
if (printSymbolizedStackTrace(Argv0, StackTrace, depth, OS))
return;
#if HAVE_DLFCN_H && __GNUG__ && !defined(__CYGWIN__)
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) 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);
OS << format("%-2d", i);
const char* name = strrchr(dlinfo.dli_fname, '/');
if (!name) OS << format(" %-*s", width, dlinfo.dli_fname);
else OS << format(" %-*s", width, name+1);
OS << format(" %#0*lx", (int)(sizeof(void*) * 2) + 2,
(unsigned long)StackTrace[i]);
if (dlinfo.dli_sname != nullptr) {
OS << ' ';
int res;
char* d = itaniumDemangle(dlinfo.dli_sname, nullptr, nullptr, &res);
if (!d) OS << dlinfo.dli_sname;
else OS << d;
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.
OS << format(" + %u",(unsigned)((char*)StackTrace[i]-
(char*)dlinfo.dli_saddr));
}
OS << '\n';
}
#elif defined(HAVE_BACKTRACE)
backtrace_symbols_fd(StackTrace, depth, STDERR_FILENO);
#endif
#endif
}
static void PrintStackTraceSignalHandler(void *) {
PrintStackTrace(llvm::errs());
}
void llvm::sys::DisableSystemDialogsOnCrash() {}
/// 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(StringRef Argv0,
bool DisableCrashReporting) {
::Argv0 = Argv0;
AddSignalHandler(PrintStackTraceSignalHandler, nullptr);
#if defined(__APPLE__) && ENABLE_CRASH_OVERRIDES
// Environment variable to disable any kind of crash dialog.
if (DisableCrashReporting || 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
}