--- /dev/null
+// Copyright 2008 Google Inc. All Rights Reserved.
+// 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
+#include <algorithm>
+
+_START_GOOGLE_NAMESPACE_
+
+// There is a better way, but this is good enough in this file.
+#define NAIVE_ARRAYSIZE(a) (sizeof(a) / sizeof(*(a)))
+
+namespace {
+
+// Wrapper of __sync_val_compare_and_swap. If the GCC extension isn't
+// defined, we try the CPU specific logics (we only support x86 and
+// x86_64 for now) first, then use a naive implementation, which has a
+// race condition.
+template<typename T>
+inline T* sync_val_compare_and_swap(T** ptr, T* oldval, T* newval) {
+#if defined(HAVE___SYNC_VAL_COMPARE_AND_SWAP)
+ return __sync_val_compare_and_swap(ptr, oldval, newval);
+#elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
+ T* ret;
+ __asm__ __volatile__("lock; cmpxchg %1, (%2);"
+ :"=a"(ret)
+ :"r"(newval), "r"(ptr), "a"(oldval)
+ :"memory", "cc");
+ return ret;
+#else
+ T* ret = *ptr;
+ if (ret == oldval) {
+ *ptr = newval;
+ }
+ return ret;
+#endif
+}
+
+// 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" },
+ { SIGBUS, "SIGBUS" },
+ { SIGTERM, "SIGTERM" },
+};
+
+// Returns the program counter from signal context, NULL if unknown.
+void* GetPC(void* ucontext_in_void) {
+#if defined(HAVE_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 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) {
+ write(STDERR_FILENO, data, size);
+}
+
+// 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());
+}
+
+// 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 (int i = 0; i < NAIVE_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 int64 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((int)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());
+}
+
+// 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) {
+ struct sigaction sig_action = {}; // Zero-clear.
+ sigemptyset(&sig_action.sa_mask);
+ sig_action.sa_handler = SIG_DFL;
+ sigaction(signal_number, &sig_action, NULL);
+ kill(getpid(), signal_number);
+}
+
+// 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 to 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.
+void FailureSignalHandler(int signal_number,
+ siginfo_t *signal_info,
+ void *ucontext) {
+ // 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 =
+ 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();
+
+ // Get the program counter from ucontext.
+ void *pc = GetPC(ucontext);
+ DumpStackFrameInfo("PC: ", pc);
+
+#ifdef HAVE_STACKTRACE
+ // Get the stack traces.
+ void *stack[32];
+ // +1 to exclude this function.
+ const int depth = GetStackTrace(stack, NAIVE_ARRAYSIZE(stack), 1);
+ DumpSignalInfo(signal_number, signal_info);
+ // Dump the stack traces.
+ for (int i = 0; i < depth; ++i) {
+ DumpStackFrameInfo(" ", stack[i]);
+ }
+#endif
+ // Kill ourself by the default signal handler.
+ InvokeDefaultSignalHandler(signal_number);
+}
+
+} // namespace
+
+void InstallFailureSignalHandler() {
+ // Build the sigaction struct.
+ struct sigaction sig_action = {}; // Zero-clear.
+ sigemptyset(&sig_action.sa_mask);
+ sig_action.sa_flags |= SA_SIGINFO;
+ sig_action.sa_sigaction = &FailureSignalHandler;
+
+ for (int i = 0; i < NAIVE_ARRAYSIZE(kFailureSignals); ++i) {
+ CHECK_ERR(sigaction(kFailureSignals[i].number, &sig_action, NULL));
+ }
+}
+
+void InstallFailureWriter(void (*writer)(const char* data, int size)) {
+ g_failure_writer = writer;
+}
+
+_END_GOOGLE_NAMESPACE_
--- /dev/null
+#! /bin/sh
+# Copyright 2008 Google, Inc. All Rights Reserved.
+# Author: Satoru Takabayashi
+#
+# Unit tests for signalhandler.cc.
+
+die () {
+ echo $1
+ exit 1
+}
+
+BINDIR=".libs"
+LIBGLOG="$BINDIR/libglog.so"
+
+BINARY="$BINDIR/signalhandler_unittest"
+
+# Remove temporary files.
+rm -f signalhandler.out*
+
+if test -e "$BINARY"; then
+ # We need shared object.
+ export LD_LIBRARY_PATH=$BINDIR
+ export DYLD_LIBRARY_PATH=$BINDIR
+else
+ # For windows
+ BINARY="./signalhandler_unittest.exe"
+ if ! test -e "$BINARY"; then
+ echo "We coundn't find demangle_unittest binary."
+ exit 1
+ fi
+fi
+
+if [ x`$BINARY` != 'xOK' ]; then
+ echo "PASS (No stacktrace support. We don't run this test.)"
+ exit 0
+fi
+
+# Test for a case the program kills itself by SIGSEGV.
+$BINARY segv 2> signalhandler.out1
+for pattern in SIGSEGV 0xdead main "Aborted at [0-9]"; do
+ if ! grep --quiet "$pattern" signalhandler.out1; then
+ die "'$pattern' should appear in the output"
+ fi
+done
+
+# Test for a case the program is killed by this shell script.
+# $! = the process id of the last command run in the background.
+# $$ = the process id of this shell.
+$BINARY loop 2> signalhandler.out2 &
+# Wait until "looping" is written in the file. This indicates the program
+# is ready to accept signals.
+while true; do
+ if grep --quiet looping signalhandler.out2; then
+ break
+ fi
+done
+kill -TERM $!
+wait $!
+
+from_pid=''
+# Only linux has the process ID of the signal sender.
+if [ x`uname` = "xLinux" ]; then
+ from_pid="from PID $$"
+fi
+for pattern in SIGTERM "by PID $!" "$from_pid" main "Aborted at [0-9]"; do
+ if ! grep --quiet "$pattern" signalhandler.out2; then
+ die "'$pattern' should appear in the output"
+ fi
+done
+
+# Test for a case the program dies in a non-main thread.
+$BINARY die_in_thread 2> signalhandler.out3
+EXPECTED_TID="`sed 's/ .*//' signalhandler.out3`"
+
+for pattern in SIGFPE DieInThread "TID $EXPECTED_TID" "Aborted at [0-9]"; do
+ if ! grep --quiet "$pattern" signalhandler.out3; then
+ die "'$pattern' should appear in the output"
+ fi
+done
+
+# Test for a case the program installs a custom failure writer that writes
+# stuff to stdout instead of stderr.
+$BINARY dump_to_stdout 1> signalhandler.out4
+for pattern in SIGABRT main "Aborted at [0-9]"; do
+ if ! grep --quiet "$pattern" signalhandler.out4; then
+ die "'$pattern' should appear in the output"
+ fi
+done
+
+echo PASS