exception_handler.cc | Explore in Territory

// Copyright 2010 Google LLC
//
// 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 LLC 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.

#ifdef HAVE_CONFIG_H
#include <config.h>  // Must come first
#endif

#include "client/linux/handler/exception_handler.h"

#include <errno.h>
#include <fcntl.h>
#include <linux/limits.h>
#include <pthread.h>
#include <sched.h>
#include <signal.h>
#include <stdio.h>
#include <sys/mman.h>
#include <sys/prctl.h>
#include <sys/syscall.h>
#include <sys/wait.h>
#include <unistd.h>

#include <sys/ucontext.h>
#include <sys/user.h>
#include <ucontext.h>

#include <algorithm>
#include <utility>
#include <vector>

#include "common/basictypes.h"
#include "common/linux/breakpad_getcontext.h"
#include "common/linux/linux_libc_support.h"
#include "common/memory_allocator.h"
#include "client/linux/log/log.h"
#include "client/linux/microdump_writer/microdump_writer.h"
#include "client/linux/minidump_writer/linux_dumper.h"
#include "client/linux/minidump_writer/minidump_writer.h"
#include "common/linux/eintr_wrapper.h"
#include "third_party/lss/linux_syscall_support.h"

#if defined(__ANDROID__)
#include "linux/sched.h"
#endif

#ifndef PR_SET_PTRACER
#define PR_SET_PTRACER …
#endif

namespace google_breakpad {

namespace {
// 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.
const int kExceptionSignals[] = …;
const int kNumHandledSignals = …;
struct sigaction old_handlers[kNumHandledSignals];
bool handlers_installed = …;

// InstallAlternateStackLocked will store the newly installed stack in new_stack
// and (if it exists) the previously installed stack in old_stack.
stack_t old_stack;
stack_t new_stack;
bool stack_installed = …;

// Create an alternative stack to run the signal handlers on. This is done since
// the signal might have been caused by a stack overflow.
// Runs before crashing: normal context.
void InstallAlternateStackLocked() { … }

// Runs before crashing: normal context.
void RestoreAlternateStackLocked() { … }

void InstallDefaultHandler(int sig) { … }

// The global exception handler stack. This is needed because there may exist
// multiple ExceptionHandler instances in a process. Each will have itself
// registered in this stack.
std::vector<ExceptionHandler*>* g_handler_stack_ = …;
pthread_mutex_t g_handler_stack_mutex_ = …;

// sizeof(CrashContext) can be too big w.r.t the size of alternatate stack
// for SignalHandler(). Keep the crash context as a .bss field. Exception
// handlers are serialized by the |g_handler_stack_mutex_| and at most one at a
// time can use |g_crash_context_|.
ExceptionHandler::CrashContext g_crash_context_;

FirstChanceHandler g_first_chance_handler_ = …;
}  // namespace

// Runs before crashing: normal context.
ExceptionHandler::ExceptionHandler(const MinidumpDescriptor& descriptor,
                                   FilterCallback filter,
                                   MinidumpCallback callback,
                                   void* callback_context,
                                   bool install_handler,
                                   const int server_fd)
    : … { … }

// Runs before crashing: normal context.
ExceptionHandler::~ExceptionHandler() { … }

// Runs before crashing: normal context.
// static
bool ExceptionHandler::InstallHandlersLocked() { … }

// This function runs in a compromised context: see the top of the file.
// Runs on the crashing thread.
// static
void ExceptionHandler::RestoreHandlersLocked() { … }

// 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) { … }

struct ThreadArgument { … };

// 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) { … }

// 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) { … }

// This is a public interface to HandleSignal that allows the client to
// generate a crash dump. This function may run in a compromised context.
bool ExceptionHandler::SimulateSignalDelivery(int sig) { … }

// This function may run in a compromised context: see the top of the file.
bool ExceptionHandler::GenerateDump(CrashContext* context) { … }

// This function runs in a compromised context: see the top of the file.
void ExceptionHandler::SendContinueSignalToChild() { … }

// This function runs in a compromised context: see the top of the file.
// Runs on the cloned process.
void ExceptionHandler::WaitForContinueSignal() { … }

// 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) { … }

// static
bool ExceptionHandler::WriteMinidump(const string& dump_path,
                                     MinidumpCallback callback,
                                     void* callback_context) { … }

// In order to making using EBP to calculate the desired value for ESP
// a valid operation, ensure that this function is compiled with a
// frame pointer using the following attribute. This attribute
// is supported on GCC but not on clang.
#if defined(__i386__) && defined(__GNUC__) && !defined(__clang__)
__attribute__((optimize("no-omit-frame-pointer")))
#endif
bool ExceptionHandler::WriteMinidump() { … }

void ExceptionHandler::AddMappingInfo(const string& name,
                                      const uint8_t identifier[sizeof(MDGUID)],
                                      uintptr_t start_address,
                                      size_t mapping_size,
                                      size_t file_offset) { … }

void ExceptionHandler::RegisterAppMemory(void* ptr, size_t length) { … }

void ExceptionHandler::UnregisterAppMemory(void* ptr) { … }

// static
bool ExceptionHandler::WriteMinidumpForChild(pid_t child,
                                             pid_t child_blamed_thread,
                                             const string& dump_path,
                                             MinidumpCallback callback,
                                             void* callback_context) { … }

void SetFirstChanceExceptionHandler(FirstChanceHandler callback) { … }

}  // namespace google_breakpad
chromium/third_party/breakpad/breakpad/src/client/linux/handler/exception_handler.cc
