* Added breakpad support for Linux.

thirdparty/breakpad/client/linux/handler/exception_handler.cc

@@ -0,0 +1,514 @@
+// Copyright (c) 2010 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.
+
+// The ExceptionHandler object installs signal handlers for a number of
+// signals. We rely on the signal handler running on the thread which crashed
+// in order to identify it. This is true of the synchronous signals (SEGV etc),
+// but not true of ABRT. Thus, if you send ABRT to yourself in a program which
+// uses ExceptionHandler, you need to use tgkill to direct it to the current
+// thread.
+//
+// The signal flow looks like this:
+//
+//   SignalHandler (uses a global stack of ExceptionHandler objects to find
+//        |         one to handle the signal. If the first rejects it, try
+//        |         the second etc...)
+//        V
+//   HandleSignal ----------------------------| (clones a new process which
+//        |                                   |  shares an address space with
+//   (wait for cloned                         |  the crashed process. This
+//     process)                               |  allows us to ptrace the crashed
+//        |                                   |  process)
+//        V                                   V
+//   (set signal handler to             ThreadEntry (static function to bounce
+//    SIG_DFL and rethrow,                    |      back into the object)
+//    killing the crashed                     |
+//    process)                                V
+//                                          DoDump  (writes minidump)
+//                                            |
+//                                            V
+//                                         sys_exit
+//
+
+// This code is a little fragmented. Different functions of the ExceptionHandler
+// class run in a number of different contexts. Some of them run in a normal
+// context and are easy to code, others run in a compromised context and the
+// restrictions at the top of minidump_writer.cc apply: no libc and use the
+// alternative malloc. Each function should have comment above it detailing the
+// context which it runs in.
+
+#include "client/linux/handler/exception_handler.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/limits.h>
+#include <sched.h>
+#include <signal.h>
+#include <stdio.h>
+#include <sys/mman.h>
+#include <sys/prctl.h>
+#if !defined(__ANDROID__)
+#include <sys/signal.h>
+#endif
+#include <sys/syscall.h>
+#if !defined(__ANDROID__)
+#include <sys/ucontext.h>
+#include <sys/user.h>
+#endif
+#include <sys/wait.h>
+#if !defined(__ANDROID__)
+#include <ucontext.h>
+#endif
+#include <unistd.h>
+
+#include <algorithm>
+#include <utility>
+#include <vector>
+
+#include "common/linux/linux_libc_support.h"
+#include "common/memory.h"
+#include "client/linux/minidump_writer/linux_dumper.h"
+#include "client/linux/minidump_writer/minidump_writer.h"
+#include "common/linux/guid_creator.h"
+#include "common/linux/eintr_wrapper.h"
+#include "third_party/lss/linux_syscall_support.h"
+
+#include "linux/sched.h"
+
+#ifndef PR_SET_PTRACER
+#define PR_SET_PTRACER 0x59616d61
+#endif
+
+// A wrapper for the tgkill syscall: send a signal to a specific thread.
+static int tgkill(pid_t tgid, pid_t tid, int sig) {
+  return syscall(__NR_tgkill, tgid, tid, sig);
+  return 0;
+}
+
+namespace google_breakpad {
+
+// The list of signals which we consider to be crashes. The default action for
+// all these signals must be Core (see man 7 signal) because we rethrow the
+// signal after handling it and expect that it'll be fatal.
+static const int kExceptionSignals[] = {
+  SIGSEGV, SIGABRT, SIGFPE, SIGILL, SIGBUS, -1
+};
+
+// We can stack multiple exception handlers. In that case, this is the global
+// which holds the stack.
+std::vector<ExceptionHandler*>* ExceptionHandler::handler_stack_ = NULL;
+unsigned ExceptionHandler::handler_stack_index_ = 0;
+pthread_mutex_t ExceptionHandler::handler_stack_mutex_ =
+    PTHREAD_MUTEX_INITIALIZER;
+
+// Runs before crashing: normal context.
+ExceptionHandler::ExceptionHandler(const std::string &dump_path,
+                                   FilterCallback filter,
+                                   MinidumpCallback callback,
+                                   void *callback_context,
+                                   bool install_handler)
+  : filter_(filter),
+    callback_(callback),
+    callback_context_(callback_context),
+    handler_installed_(install_handler)
+{
+  Init(dump_path, -1);
+}
+
+ExceptionHandler::ExceptionHandler(const std::string &dump_path,
+                                   FilterCallback filter,
+                                   MinidumpCallback callback,
+                                   void* callback_context,
+                                   bool install_handler,
+                                   const int server_fd)
+  : filter_(filter),
+    callback_(callback),
+    callback_context_(callback_context),
+    handler_installed_(install_handler)
+{
+  Init(dump_path, server_fd);
+}
+
+// Runs before crashing: normal context.
+ExceptionHandler::~ExceptionHandler() {
+  UninstallHandlers();
+}
+
+void ExceptionHandler::Init(const std::string &dump_path,
+                            const int server_fd)
+{
+  crash_handler_ = NULL;
+  if (0 <= server_fd)
+    crash_generation_client_
+      .reset(CrashGenerationClient::TryCreate(server_fd));
+
+  if (handler_installed_)
+    InstallHandlers();
+
+  if (!IsOutOfProcess())
+    set_dump_path(dump_path);
+
+  pthread_mutex_lock(&handler_stack_mutex_);
+  if (handler_stack_ == NULL)
+    handler_stack_ = new std::vector<ExceptionHandler *>;
+  handler_stack_->push_back(this);
+  pthread_mutex_unlock(&handler_stack_mutex_);
+}
+
+// Runs before crashing: normal context.
+bool ExceptionHandler::InstallHandlers() {
+  // We run the signal handlers on an alternative stack because we might have
+  // crashed because of a stack overflow.
+
+  // We use this value rather than SIGSTKSZ because we would end up overrunning
+  // such a small stack.
+  static const unsigned kSigStackSize = 8192;
+
+  signal_stack = malloc(kSigStackSize);
+  stack_t stack;
+  memset(&stack, 0, sizeof(stack));
+  stack.ss_sp = signal_stack;
+  stack.ss_size = kSigStackSize;
+
+  if (sys_sigaltstack(&stack, NULL) == -1)
+    return false;
+
+  struct sigaction sa;
+  memset(&sa, 0, sizeof(sa));
+  sigemptyset(&sa.sa_mask);
+
+  // mask all exception signals when we're handling one of them.
+  for (unsigned i = 0; kExceptionSignals[i] != -1; ++i)
+    sigaddset(&sa.sa_mask, kExceptionSignals[i]);
+
+  sa.sa_sigaction = SignalHandler;
+  sa.sa_flags = SA_ONSTACK | SA_SIGINFO;
+
+  for (unsigned i = 0; kExceptionSignals[i] != -1; ++i) {
+    struct sigaction* old = new struct sigaction;
+    if (sigaction(kExceptionSignals[i], &sa, old) == -1)
+      return false;
+    old_handlers_.push_back(std::make_pair(kExceptionSignals[i], old));
+  }
+  return true;
+}
+
+// Runs before crashing: normal context.
+void ExceptionHandler::UninstallHandlers() {
+  for (unsigned i = 0; i < old_handlers_.size(); ++i) {
+    struct sigaction *action =
+        reinterpret_cast<struct sigaction*>(old_handlers_[i].second);
+    sigaction(old_handlers_[i].first, action, NULL);
+    delete action;
+  }
+  pthread_mutex_lock(&handler_stack_mutex_);
+  std::vector<ExceptionHandler*>::iterator handler =
+      std::find(handler_stack_->begin(), handler_stack_->end(), this);
+  handler_stack_->erase(handler);
+  pthread_mutex_unlock(&handler_stack_mutex_);
+  old_handlers_.clear();
+}
+
+// Runs before crashing: normal context.
+void ExceptionHandler::UpdateNextID() {
+  GUID guid;
+  char guid_str[kGUIDStringLength + 1];
+  if (CreateGUID(&guid) && GUIDToString(&guid, guid_str, sizeof(guid_str))) {
+    next_minidump_id_ = guid_str;
+    next_minidump_id_c_ = next_minidump_id_.c_str();
+
+    char minidump_path[PATH_MAX];
+    snprintf(minidump_path, sizeof(minidump_path), "%s/%s.dmp",
+             dump_path_c_,
+             guid_str);
+
+    next_minidump_path_ = minidump_path;
+    next_minidump_path_c_ = next_minidump_path_.c_str();
+  }
+}
+
+// void ExceptionHandler::set_crash_handler(HandlerCallback callback) {
+//   crash_handler_ = callback;
+// }
+
+// This function runs in a compromised context: see the top of the file.
+// Runs on the crashing thread.
+// static
+void ExceptionHandler::SignalHandler(int sig, siginfo_t* info, void* uc) {
+  // All the exception signals are blocked at this point.
+  pthread_mutex_lock(&handler_stack_mutex_);
+
+  if (!handler_stack_->size()) {
+    pthread_mutex_unlock(&handler_stack_mutex_);
+    return;
+  }
+
+  for (int i = handler_stack_->size() - 1; i >= 0; --i) {
+    if ((*handler_stack_)[i]->HandleSignal(sig, info, uc)) {
+      // successfully handled: We are in an invalid state since an exception
+      // signal has been delivered. We don't call the exit handlers because
+      // they could end up corrupting on-disk state.
+      break;
+    }
+  }
+
+  pthread_mutex_unlock(&handler_stack_mutex_);
+
+  if (info->si_pid) {
+    // This signal was triggered by somebody sending us the signal with kill().
+    // In order to retrigger it, we have to queue a new signal by calling
+    // kill() ourselves.
+    if (tgkill(getpid(), syscall(__NR_gettid), sig) < 0) {
+      // If we failed to kill ourselves (e.g. because a sandbox disallows us
+      // to do so), we instead resort to terminating our process. This will
+      // result in an incorrect exit code.
+      _exit(1);
+    }
+  } else {
+    // This was a synchronous signal triggered by a hard fault (e.g. SIGSEGV).
+    // No need to reissue the signal. It will automatically trigger again,
+    // when we return from the signal handler.
+  }
+
+  // As soon as we return from the signal handler, our signal will become
+  // unmasked. At that time, we will  get terminated with the same signal that
+  // was triggered originally. This allows our parent to know that we crashed.
+  // The default action for all the signals which we catch is Core, so
+  // this is the end of us.
+  signal(sig, SIG_DFL);
+}
+
+struct ThreadArgument {
+  pid_t pid;  // the crashing process
+  ExceptionHandler* handler;
+  const void* context;  // a CrashContext structure
+  size_t context_size;
+};
+
+// This is the entry function for the cloned process. We are in a compromised
+// context here: see the top of the file.
+// static
+int ExceptionHandler::ThreadEntry(void *arg) {
+  const ThreadArgument *thread_arg = reinterpret_cast<ThreadArgument*>(arg);
+
+  // Block here until the crashing process unblocks us when
+  // we're allowed to use ptrace
+  thread_arg->handler->WaitForContinueSignal();
+
+  return thread_arg->handler->DoDump(thread_arg->pid, thread_arg->context,
+                                     thread_arg->context_size) == false;
+}
+
+// This function runs in a compromised context: see the top of the file.
+// Runs on the crashing thread.
+bool ExceptionHandler::HandleSignal(int sig, siginfo_t* info, void* uc) {
+  if (filter_ && !filter_(callback_context_))
+    return false;
+
+  // Allow ourselves to be dumped if the signal is trusted.
+  bool signal_trusted = info->si_code > 0;
+  bool signal_pid_trusted = info->si_code == SI_USER ||
+      info->si_code == SI_TKILL;
+  if (signal_trusted || (signal_pid_trusted && info->si_pid == getpid())) {
+    sys_prctl(PR_SET_DUMPABLE, 1);
+  }
+  CrashContext context;
+  memcpy(&context.siginfo, info, sizeof(siginfo_t));
+  memcpy(&context.context, uc, sizeof(struct ucontext));
+#if !defined(__ARM_EABI__)
+  // FP state is not part of user ABI on ARM Linux.
+  struct ucontext *uc_ptr = (struct ucontext*)uc;
+  if (uc_ptr->uc_mcontext.fpregs) {
+    memcpy(&context.float_state,
+           uc_ptr->uc_mcontext.fpregs,
+           sizeof(context.float_state));
+  }
+#endif
+  context.tid = syscall(__NR_gettid);
+  if (crash_handler_ != NULL) {
+    if (crash_handler_(&context, sizeof(context),
+                       callback_context_)) {
+      return true;
+    }
+  }
+  return GenerateDump(&context);
+}
+
+// This function may run in a compromised context: see the top of the file.
+bool ExceptionHandler::GenerateDump(CrashContext *context) {
+  if (IsOutOfProcess())
+    return crash_generation_client_->RequestDump(context, sizeof(*context));
+
+  static const unsigned kChildStackSize = 8000;
+  PageAllocator allocator;
+  uint8_t* stack = (uint8_t*) allocator.Alloc(kChildStackSize);
+  if (!stack)
+    return false;
+  // clone() needs the top-most address. (scrub just to be safe)
+  stack += kChildStackSize;
+  my_memset(stack - 16, 0, 16);
+
+  ThreadArgument thread_arg;
+  thread_arg.handler = this;
+  thread_arg.pid = getpid();
+  thread_arg.context = context;
+  thread_arg.context_size = sizeof(*context);
+
+  // We need to explicitly enable ptrace of parent processes on some
+  // kernels, but we need to know the PID of the cloned process before we
+  // can do this. Create a pipe here which we can use to block the
+  // cloned process after creating it, until we have explicitly enabled ptrace
+  if(sys_pipe(fdes) == -1) {
+    // Creating the pipe failed. We'll log an error but carry on anyway,
+    // as we'll probably still get a useful crash report. All that will happen
+    // is the write() and read() calls will fail with EBADF
+    static const char no_pipe_msg[] = "ExceptionHandler::GenerateDump \
+                                       sys_pipe failed:";
+    sys_write(2, no_pipe_msg, sizeof(no_pipe_msg) - 1);
+    sys_write(2, strerror(errno), strlen(strerror(errno)));
+    sys_write(2, "\n", 1);
+  }
+
+  const pid_t child = sys_clone(
+      ThreadEntry, stack, CLONE_FILES | CLONE_FS | CLONE_UNTRACED,
+      &thread_arg, NULL, NULL, NULL);
+  int r, status;
+  // Allow the child to ptrace us
+  prctl(PR_SET_PTRACER, child, 0, 0, 0);
+  SendContinueSignalToChild();
+  do {
+    r = sys_waitpid(child, &status, __WALL);
+  } while (r == -1 && errno == EINTR);
+
+  sys_close(fdes[0]);
+  sys_close(fdes[1]);
+
+  if (r == -1) {
+    static const char msg[] = "ExceptionHandler::GenerateDump waitpid failed:";
+    sys_write(2, msg, sizeof(msg) - 1);
+    sys_write(2, strerror(errno), strlen(strerror(errno)));
+    sys_write(2, "\n", 1);
+  }
+
+  bool success = r != -1 && WIFEXITED(status) && WEXITSTATUS(status) == 0;
+
+  if (callback_)
+    success = callback_(dump_path_c_, next_minidump_id_c_,
+                        callback_context_, success);
+
+  return success;
+}
+
+// This function runs in a compromised context: see the top of the file.
+void ExceptionHandler::SendContinueSignalToChild() {
+  static const char okToContinueMessage = 'a';
+  int r;
+  r = HANDLE_EINTR(sys_write(fdes[1], &okToContinueMessage, sizeof(char)));
+  if(r == -1) {
+    static const char msg[] = "ExceptionHandler::SendContinueSignalToChild \
+                               sys_write failed:";
+    sys_write(2, msg, sizeof(msg) - 1);
+    sys_write(2, strerror(errno), strlen(strerror(errno)));
+    sys_write(2, "\n", 1);
+  }
+}
+
+// This function runs in a compromised context: see the top of the file.
+// Runs on the cloned process.
+void ExceptionHandler::WaitForContinueSignal() {
+  int r;
+  char receivedMessage;
+  r = HANDLE_EINTR(sys_read(fdes[0], &receivedMessage, sizeof(char)));
+  if(r == -1) {
+    static const char msg[] = "ExceptionHandler::WaitForContinueSignal \
+                               sys_read failed:";
+    sys_write(2, msg, sizeof(msg) - 1);
+    sys_write(2, strerror(errno), strlen(strerror(errno)));
+    sys_write(2, "\n", 1);
+  }
+}
+
+// This function runs in a compromised context: see the top of the file.
+// Runs on the cloned process.
+bool ExceptionHandler::DoDump(pid_t crashing_process, const void* context,
+                              size_t context_size) {
+  return google_breakpad::WriteMinidump(next_minidump_path_c_,
+                                        crashing_process,
+                                        context,
+                                        context_size,
+                                        mapping_list_);
+}
+
+// static
+bool ExceptionHandler::WriteMinidump(const std::string &dump_path,
+                                     MinidumpCallback callback,
+                                     void* callback_context) {
+  ExceptionHandler eh(dump_path, NULL, callback, callback_context, false);
+  return eh.WriteMinidump();
+}
+
+bool ExceptionHandler::WriteMinidump() {
+#if !defined(__ARM_EABI__)
+  // Allow ourselves to be dumped.
+  sys_prctl(PR_SET_DUMPABLE, 1);
+
+  CrashContext context;
+  int getcontext_result = getcontext(&context.context);
+  if (getcontext_result)
+    return false;
+  memcpy(&context.float_state, context.context.uc_mcontext.fpregs,
+         sizeof(context.float_state));
+  context.tid = sys_gettid();
+
+  bool success = GenerateDump(&context);
+  UpdateNextID();
+  return success;
+#else
+  return false;
+#endif  // !defined(__ARM_EABI__)
+}
+
+void ExceptionHandler::AddMappingInfo(const std::string& name,
+                                      const u_int8_t identifier[sizeof(MDGUID)],
+                                      uintptr_t start_address,
+                                      size_t mapping_size,
+                                      size_t file_offset) {
+  MappingInfo info;
+  info.start_addr = start_address;
+  info.size = mapping_size;
+  info.offset = file_offset;
+  strncpy(info.name, name.c_str(), std::min(name.size(), sizeof(info)));
+
+  MappingEntry mapping;
+  mapping.first = info;
+  memcpy(mapping.second, identifier, sizeof(MDGUID));
+  mapping_list_.push_back(mapping);
+}
+
+}  // namespace google_breakpad