1 files changed, 403 insertions, 0 deletions
diff --git a/src/signalhandler.cc b/src/signalhandler.cc
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+++ b/src/signalhandler.cc
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+// 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_