// Copyright (c) 2008, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// Author: Satoru Takabayashi
//
// Implementation of InstallFailureSignalHandler().
#include "utilities.h"
#include "stacktrace.h"
#include "symbolize.h"
#include "glog/logging.h"
#include <signal.h>
#include <time.h>
#ifdef HAVE_UCONTEXT_H
# include <ucontext.h>
#endif
#ifdef HAVE_SYS_UCONTEXT_H
# include <sys/ucontext.h>
#endif
#include <algorithm>
_START_GOOGLE_NAMESPACE_
namespace {
// We'll install the failure signal handler for these signals. We could
// use strsignal() to get signal names, but we don't use it to avoid
// introducing yet another #ifdef complication.
//
// The list should be synced with the comment in signalhandler.h.
const struct {
int number;
const char *name;
} kFailureSignals[] = {
{ SIGSEGV, "SIGSEGV" },
{ SIGILL, "SIGILL" },
{ SIGFPE, "SIGFPE" },
{ SIGABRT, "SIGABRT" },
#if !defined(OS_WINDOWS)
{ SIGBUS, "SIGBUS" },
#endif
{ SIGTERM, "SIGTERM" },
};
static bool kFailureSignalHandlerInstalled = false;
// Returns the program counter from signal context, NULL if unknown.
void* GetPC(void* ucontext_in_void) {
#if (defined(HAVE_UCONTEXT_H) || defined(HAVE_SYS_UCONTEXT_H)) && defined(PC_FROM_UCONTEXT)
if (ucontext_in_void != NULL) {
ucontext_t *context = reinterpret_cast<ucontext_t *>(ucontext_in_void);
return (void*)context->PC_FROM_UCONTEXT;
}
#endif
return NULL;
}
// The class is used for formatting error messages. We don't use printf()
// as it's not async signal safe.
class MinimalFormatter {
public:
MinimalFormatter(char *buffer, int size)
: buffer_(buffer),
cursor_(buffer),
end_(buffer + size) {
}
// Returns the number of bytes written in the buffer.
int num_bytes_written() const { return (int) (cursor_ - buffer_); }
// Appends string from "str" and updates the internal cursor.
void AppendString(const char* str) {
int i = 0;
while (str[i] != '\0' && cursor_ + i < end_) {
cursor_[i] = str[i];
++i;
}
cursor_ += i;
}
// Formats "number" in "radix" and updates the internal cursor.
// Lowercase letters are used for 'a' - 'z'.
void AppendUint64(uint64 number, int radix) {
int i = 0;
while (cursor_ + i < end_) {
const int tmp = number % radix;
number /= radix;
cursor_[i] = (tmp < 10 ? '0' + tmp : 'a' + tmp - 10);
++i;
if (number == 0) {
break;
}
}
// Reverse the bytes written.
std::reverse(cursor_, cursor_ + i);
cursor_ += i;
}
// Formats "number" as hexadecimal number, and updates the internal
// cursor. Padding will be added in front if needed.
void AppendHexWithPadding(uint64 number, int width) {
char* start = cursor_;
AppendString("0x");
AppendUint64(number, 16);
// Move to right and add padding in front if needed.
if (cursor_ < start + width) {
const int64 delta = start + width - cursor_;
std::copy(start, cursor_, start + delta);
std::fill(start, start + delta, ' ');
cursor_ = start + width;
}
}
private:
char *buffer_;
char *cursor_;
const char * const end_;
};
// Writes the given data with the size to the standard error.
void WriteToStderr(const char* data, int size) {
if (write(STDERR_FILENO, data, size) < 0) {
// Ignore errors.
}
}
// The writer function can be changed by InstallFailureWriter().
void (*g_failure_writer)(const char* data, int size) = WriteToStderr;
// Dumps time information. We don't dump human-readable time information
// as localtime() is not guaranteed to be async signal safe.
void DumpTimeInfo() {
time_t time_in_sec = time(NULL);
char buf[256]; // Big enough for time info.
MinimalFormatter formatter(buf, sizeof(buf));
formatter.AppendString("*** Aborted at ");
formatter.AppendUint64(time_in_sec, 10);
formatter.AppendString(" (unix time)");
formatter.AppendString(" try \"date -d @");
formatter.AppendUint64(time_in_sec, 10);
formatter.AppendString("\" if you are using GNU date ***\n");
g_failure_writer(buf, formatter.num_bytes_written());
}
// TODO(hamaji): Use signal instead of sigaction?
#ifdef HAVE_SIGACTION
// Dumps information about the signal to STDERR.
void DumpSignalInfo(int signal_number, siginfo_t *siginfo) {
// Get the signal name.
const char* signal_name = NULL;
for (size_t i = 0; i < ARRAYSIZE(kFailureSignals); ++i) {
if (signal_number == kFailureSignals[i].number) {
signal_name = kFailureSignals[i].name;
}
}
char buf[256]; // Big enough for signal info.
MinimalFormatter formatter(buf, sizeof(buf));
formatter.AppendString("*** ");
if (signal_name) {
formatter.AppendString(signal_name);
} else {
// Use the signal number if the name is unknown. The signal name
// should be known, but just in case.
formatter.AppendString("Signal ");
formatter.AppendUint64(signal_number, 10);
}
formatter.AppendString(" (@0x");
formatter.AppendUint64(reinterpret_cast<uintptr_t>(siginfo->si_addr), 16);
formatter.AppendString(")");
formatter.AppendString(" received by PID ");
formatter.AppendUint64(getpid(), 10);
formatter.AppendString(" (TID 0x");
// We assume pthread_t is an integral number or a pointer, rather
// than a complex struct. In some environments, pthread_self()
// returns an uint64 but in some other environments pthread_self()
// returns a pointer. Hence we use C-style cast here, rather than
// reinterpret/static_cast, to support both types of environments.
formatter.AppendUint64((uintptr_t)pthread_self(), 16);
formatter.AppendString(") ");
// Only linux has the PID of the signal sender in si_pid.
#ifdef OS_LINUX
formatter.AppendString("from PID ");
formatter.AppendUint64(siginfo->si_pid, 10);
formatter.AppendString("; ");
#endif
formatter.AppendString("stack trace: ***\n");
g_failure_writer(buf, formatter.num_bytes_written());
}
#endif // HAVE_SIGACTION
// Dumps information about the stack frame to STDERR.
void DumpStackFrameInfo(const char* prefix, void* pc) {
// Get the symbol name.
const char *symbol = "(unknown)";
char symbolized[1024]; // Big enough for a sane symbol.
// Symbolizes the previous address of pc because pc may be in the
// next function.
if (Symbolize(reinterpret_cast<char *>(pc) - 1,
symbolized, sizeof(symbolized))) {
symbol = symbolized;
}
char buf[1024]; // Big enough for stack frame info.
MinimalFormatter formatter(buf, sizeof(buf));
formatter.AppendString(prefix);
formatter.AppendString("@ ");
const int width = 2 * sizeof(void*) + 2; // + 2 for "0x".
formatter.AppendHexWithPadding(reinterpret_cast<uintptr_t>(pc), width);
formatter.AppendString(" ");
formatter.AppendString(symbol);
formatter.AppendString("\n");
g_failure_writer(buf, formatter.num_bytes_written());
}
// Invoke the default signal handler.
void InvokeDefaultSignalHandler(int signal_number) {
#ifdef HAVE_SIGACTION
struct sigaction sig_action;
memset(&sig_action, 0, sizeof(sig_action));
sigemptyset(&sig_action.sa_mask);
sig_action.sa_handler = SIG_DFL;
sigaction(signal_number, &sig_action, NULL);
kill(getpid(), signal_number);
#elif defined(OS_WINDOWS)
signal(signal_number, SIG_DFL);
raise(signal_number);
#endif
}
// This variable is used for protecting FailureSignalHandler() from
// dumping stuff while another thread is doing it. Our policy is to let
// the first thread dump stuff and let other threads wait.
// See also comments in FailureSignalHandler().
static pthread_t* g_entered_thread_id_pointer = NULL;
// Dumps signal and stack frame information, and invokes the default
// signal handler once our job is done.
#if defined(OS_WINDOWS)
void FailureSignalHandler(int signal_number)
#else
void FailureSignalHandler(int signal_number,
siginfo_t *signal_info,
void *ucontext)
#endif
{
// First check if we've already entered the function. We use an atomic
// compare and swap operation for platforms that support it. For other
// platforms, we use a naive method that could lead to a subtle race.
// We assume pthread_self() is async signal safe, though it's not
// officially guaranteed.
pthread_t my_thread_id = pthread_self();
// NOTE: We could simply use pthread_t rather than pthread_t* for this,
// if pthread_self() is guaranteed to return non-zero value for thread
// ids, but there is no such guarantee. We need to distinguish if the
// old value (value returned from __sync_val_compare_and_swap) is
// different from the original value (in this case NULL).
pthread_t* old_thread_id_pointer =
glog_internal_namespace_::sync_val_compare_and_swap(
&g_entered_thread_id_pointer,
static_cast<pthread_t*>(NULL),
&my_thread_id);
if (old_thread_id_pointer != NULL) {
// We've already entered the signal handler. What should we do?
if (pthread_equal(my_thread_id, *g_entered_thread_id_pointer)) {
// It looks the current thread is reentering the signal handler.
// Something must be going wrong (maybe we are reentering by another
// type of signal?). Kill ourself by the default signal handler.
InvokeDefaultSignalHandler(signal_number);
}
// Another thread is dumping stuff. Let's wait until that thread
// finishes the job and kills the process.
while (true) {
sleep(1);
}
}
// This is the first time we enter the signal handler. We are going to
// do some interesting stuff from here.
// TODO(satorux): We might want to set timeout here using alarm(), but
// mixing alarm() and sleep() can be a bad idea.
// First dump time info.
DumpTimeInfo();
#if !defined(OS_WINDOWS)
// Get the program counter from ucontext.
void *pc = GetPC(ucontext);
DumpStackFrameInfo("PC: ", pc);
#endif
#ifdef HAVE_STACKTRACE
// Get the stack traces.
void *stack[32];
// +1 to exclude this function.
const int depth = GetStackTrace(stack, ARRAYSIZE(stack), 1);
# ifdef HAVE_SIGACTION
DumpSignalInfo(signal_number, signal_info);
# endif
// Dump the stack traces.
for (int i = 0; i < depth; ++i) {
DumpStackFrameInfo(" ", stack[i]);
}
#endif
// *** TRANSITION ***
//
// BEFORE this point, all code must be async-termination-safe!
// (See WARNING above.)
//
// AFTER this point, we do unsafe things, like using LOG()!
// The process could be terminated or hung at any time. We try to
// do more useful things first and riskier things later.
// Flush the logs before we do anything in case 'anything'
// causes problems.
FlushLogFilesUnsafe(0);
// Kill ourself by the default signal handler.
InvokeDefaultSignalHandler(signal_number);
}
} // namespace
namespace glog_internal_namespace_ {
bool IsFailureSignalHandlerInstalled() {
#ifdef HAVE_SIGACTION
// TODO(andschwa): Return kFailureSignalHandlerInstalled?
struct sigaction sig_action;
memset(&sig_action, 0, sizeof(sig_action));
sigemptyset(&sig_action.sa_mask);
sigaction(SIGABRT, NULL, &sig_action);
if (sig_action.sa_sigaction == &FailureSignalHandler)
return true;
#elif defined(OS_WINDOWS)
return kFailureSignalHandlerInstalled;
#endif // HAVE_SIGACTION
return false;
}
} // namespace glog_internal_namespace_
void InstallFailureSignalHandler() {
#ifdef HAVE_SIGACTION
// Build the sigaction struct.
struct sigaction sig_action;
memset(&sig_action, 0, sizeof(sig_action));
sigemptyset(&sig_action.sa_mask);
sig_action.sa_flags |= SA_SIGINFO;
sig_action.sa_sigaction = &FailureSignalHandler;
for (size_t i = 0; i < ARRAYSIZE(kFailureSignals); ++i) {
CHECK_ERR(sigaction(kFailureSignals[i].number, &sig_action, NULL));
}
kFailureSignalHandlerInstalled = true;
#elif defined(OS_WINDOWS)
for (size_t i = 0; i < ARRAYSIZE(kFailureSignals); ++i) {
CHECK_NE(signal(kFailureSignals[i].number, &FailureSignalHandler),
SIG_ERR);
}
kFailureSignalHandlerInstalled = true;
#endif // HAVE_SIGACTION
}
void InstallFailureWriter(void (*writer)(const char* data, int size)) {
#if defined(HAVE_SIGACTION) || defined(OS_WINDOWS)
g_failure_writer = writer;
#endif // HAVE_SIGACTION
}
_END_GOOGLE_NAMESPACE_
