513 lines
18 KiB
C++
513 lines
18 KiB
C++
// Copyright (c) 2010 Google Inc.
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following disclaimer
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// in the documentation and/or other materials provided with the
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// distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived from
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// this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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// The ExceptionHandler object installs signal handlers for a number of
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// signals. We rely on the signal handler running on the thread which crashed
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// in order to identify it. This is true of the synchronous signals (SEGV etc),
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// but not true of ABRT. Thus, if you send ABRT to yourself in a program which
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// uses ExceptionHandler, you need to use tgkill to direct it to the current
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// thread.
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//
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// The signal flow looks like this:
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//
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// SignalHandler (uses a global stack of ExceptionHandler objects to find
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// | one to handle the signal. If the first rejects it, try
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// | the second etc...)
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// V
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// HandleSignal ----------------------------| (clones a new process which
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// | | shares an address space with
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// (wait for cloned | the crashed process. This
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// process) | allows us to ptrace the crashed
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// | | process)
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// V V
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// (set signal handler to ThreadEntry (static function to bounce
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// SIG_DFL and rethrow, | back into the object)
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// killing the crashed |
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// process) V
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// DoDump (writes minidump)
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// |
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// V
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// sys_exit
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//
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// This code is a little fragmented. Different functions of the ExceptionHandler
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// class run in a number of different contexts. Some of them run in a normal
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// context and are easy to code, others run in a compromised context and the
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// restrictions at the top of minidump_writer.cc apply: no libc and use the
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// alternative malloc. Each function should have comment above it detailing the
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// context which it runs in.
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#include "client/linux/handler/exception_handler.h"
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#include <errno.h>
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#include <fcntl.h>
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#include <linux/limits.h>
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#include <sched.h>
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#include <signal.h>
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#include <stdio.h>
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#include <sys/mman.h>
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#include <sys/prctl.h>
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#if !defined(__ANDROID__)
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#include <sys/signal.h>
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#endif
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#include <sys/syscall.h>
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#if !defined(__ANDROID__)
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#include <sys/ucontext.h>
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#include <sys/user.h>
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#endif
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#include <sys/wait.h>
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#if !defined(__ANDROID__)
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#include <ucontext.h>
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#endif
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#include <unistd.h>
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#include <algorithm>
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#include <utility>
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#include <vector>
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#include "common/linux/linux_libc_support.h"
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#include "common/memory.h"
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#include "client/linux/minidump_writer/linux_dumper.h"
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#include "client/linux/minidump_writer/minidump_writer.h"
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#include "common/linux/guid_creator.h"
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#include "common/linux/eintr_wrapper.h"
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#include "third_party/lss/linux_syscall_support.h"
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#ifndef PR_SET_PTRACER
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#define PR_SET_PTRACER 0x59616d61
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#endif
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// A wrapper for the tgkill syscall: send a signal to a specific thread.
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static int tgkill(pid_t tgid, pid_t tid, int sig) {
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return syscall(__NR_tgkill, tgid, tid, sig);
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return 0;
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}
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namespace google_breakpad {
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// The list of signals which we consider to be crashes. The default action for
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// all these signals must be Core (see man 7 signal) because we rethrow the
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// signal after handling it and expect that it'll be fatal.
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static const int kExceptionSignals[] = {
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SIGSEGV, SIGABRT, SIGFPE, SIGILL, SIGBUS, -1
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};
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// We can stack multiple exception handlers. In that case, this is the global
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// which holds the stack.
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std::vector<ExceptionHandler*>* ExceptionHandler::handler_stack_ = NULL;
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unsigned ExceptionHandler::handler_stack_index_ = 0;
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pthread_mutex_t ExceptionHandler::handler_stack_mutex_ =
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PTHREAD_MUTEX_INITIALIZER;
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// Runs before crashing: normal context.
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ExceptionHandler::ExceptionHandler(const std::string &dump_path,
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FilterCallback filter,
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MinidumpCallback callback,
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void *callback_context,
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bool install_handler)
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: filter_(filter),
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callback_(callback),
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callback_context_(callback_context),
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handler_installed_(install_handler)
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{
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Init(dump_path, -1);
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}
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ExceptionHandler::ExceptionHandler(const std::string &dump_path,
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FilterCallback filter,
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MinidumpCallback callback,
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void* callback_context,
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bool install_handler,
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const int server_fd)
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: filter_(filter),
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callback_(callback),
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callback_context_(callback_context),
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handler_installed_(install_handler)
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{
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Init(dump_path, server_fd);
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}
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// Runs before crashing: normal context.
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ExceptionHandler::~ExceptionHandler() {
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UninstallHandlers();
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}
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void ExceptionHandler::Init(const std::string &dump_path,
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const int server_fd)
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{
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crash_handler_ = NULL;
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if (0 <= server_fd)
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crash_generation_client_
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.reset(CrashGenerationClient::TryCreate(server_fd));
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if (handler_installed_)
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InstallHandlers();
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if (!IsOutOfProcess())
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set_dump_path(dump_path);
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pthread_mutex_lock(&handler_stack_mutex_);
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if (handler_stack_ == NULL)
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handler_stack_ = new std::vector<ExceptionHandler *>;
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handler_stack_->push_back(this);
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pthread_mutex_unlock(&handler_stack_mutex_);
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}
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// Runs before crashing: normal context.
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bool ExceptionHandler::InstallHandlers() {
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// We run the signal handlers on an alternative stack because we might have
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// crashed because of a stack overflow.
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// We use this value rather than SIGSTKSZ because we would end up overrunning
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// such a small stack.
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static const unsigned kSigStackSize = 8192;
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signal_stack = malloc(kSigStackSize);
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stack_t stack;
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memset(&stack, 0, sizeof(stack));
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stack.ss_sp = signal_stack;
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stack.ss_size = kSigStackSize;
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if (sys_sigaltstack(&stack, NULL) == -1)
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return false;
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struct sigaction sa;
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memset(&sa, 0, sizeof(sa));
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sigemptyset(&sa.sa_mask);
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// mask all exception signals when we're handling one of them.
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for (unsigned i = 0; kExceptionSignals[i] != -1; ++i)
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sigaddset(&sa.sa_mask, kExceptionSignals[i]);
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sa.sa_sigaction = SignalHandler;
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sa.sa_flags = SA_ONSTACK | SA_SIGINFO;
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for (unsigned i = 0; kExceptionSignals[i] != -1; ++i) {
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struct sigaction* old = new struct sigaction;
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if (sigaction(kExceptionSignals[i], &sa, old) == -1)
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return false;
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old_handlers_.push_back(std::make_pair(kExceptionSignals[i], old));
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}
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return true;
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}
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// Runs before crashing: normal context.
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void ExceptionHandler::UninstallHandlers() {
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for (unsigned i = 0; i < old_handlers_.size(); ++i) {
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struct sigaction *action =
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reinterpret_cast<struct sigaction*>(old_handlers_[i].second);
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sigaction(old_handlers_[i].first, action, NULL);
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delete action;
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}
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pthread_mutex_lock(&handler_stack_mutex_);
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std::vector<ExceptionHandler*>::iterator handler =
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std::find(handler_stack_->begin(), handler_stack_->end(), this);
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handler_stack_->erase(handler);
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pthread_mutex_unlock(&handler_stack_mutex_);
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old_handlers_.clear();
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}
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// Runs before crashing: normal context.
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void ExceptionHandler::UpdateNextID() {
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GUID guid;
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char guid_str[kGUIDStringLength + 1];
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if (CreateGUID(&guid) && GUIDToString(&guid, guid_str, sizeof(guid_str))) {
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next_minidump_id_ = guid_str;
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next_minidump_id_c_ = next_minidump_id_.c_str();
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char minidump_path[PATH_MAX];
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snprintf(minidump_path, sizeof(minidump_path), "%s/%s.dmp",
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dump_path_c_,
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guid_str);
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next_minidump_path_ = minidump_path;
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next_minidump_path_c_ = next_minidump_path_.c_str();
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}
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}
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// void ExceptionHandler::set_crash_handler(HandlerCallback callback) {
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// crash_handler_ = callback;
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// }
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// This function runs in a compromised context: see the top of the file.
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// Runs on the crashing thread.
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// static
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void ExceptionHandler::SignalHandler(int sig, siginfo_t* info, void* uc) {
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// All the exception signals are blocked at this point.
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pthread_mutex_lock(&handler_stack_mutex_);
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if (!handler_stack_->size()) {
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pthread_mutex_unlock(&handler_stack_mutex_);
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return;
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}
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for (int i = handler_stack_->size() - 1; i >= 0; --i) {
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if ((*handler_stack_)[i]->HandleSignal(sig, info, uc)) {
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// successfully handled: We are in an invalid state since an exception
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// signal has been delivered. We don't call the exit handlers because
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// they could end up corrupting on-disk state.
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break;
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}
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}
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pthread_mutex_unlock(&handler_stack_mutex_);
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if (info->si_pid) {
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// This signal was triggered by somebody sending us the signal with kill().
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// In order to retrigger it, we have to queue a new signal by calling
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// kill() ourselves.
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if (tgkill(getpid(), syscall(__NR_gettid), sig) < 0) {
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// If we failed to kill ourselves (e.g. because a sandbox disallows us
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// to do so), we instead resort to terminating our process. This will
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// result in an incorrect exit code.
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_exit(1);
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}
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} else {
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// This was a synchronous signal triggered by a hard fault (e.g. SIGSEGV).
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// No need to reissue the signal. It will automatically trigger again,
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// when we return from the signal handler.
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}
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// As soon as we return from the signal handler, our signal will become
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// unmasked. At that time, we will get terminated with the same signal that
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// was triggered originally. This allows our parent to know that we crashed.
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// The default action for all the signals which we catch is Core, so
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// this is the end of us.
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signal(sig, SIG_DFL);
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}
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struct ThreadArgument {
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pid_t pid; // the crashing process
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ExceptionHandler* handler;
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const void* context; // a CrashContext structure
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size_t context_size;
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};
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// This is the entry function for the cloned process. We are in a compromised
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// context here: see the top of the file.
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// static
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int ExceptionHandler::ThreadEntry(void *arg) {
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const ThreadArgument *thread_arg = reinterpret_cast<ThreadArgument*>(arg);
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// Block here until the crashing process unblocks us when
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// we're allowed to use ptrace
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thread_arg->handler->WaitForContinueSignal();
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return thread_arg->handler->DoDump(thread_arg->pid, thread_arg->context,
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thread_arg->context_size) == false;
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}
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// This function runs in a compromised context: see the top of the file.
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// Runs on the crashing thread.
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bool ExceptionHandler::HandleSignal(int sig, siginfo_t* info, void* uc) {
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if (filter_ && !filter_(callback_context_))
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return false;
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// Allow ourselves to be dumped if the signal is trusted.
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bool signal_trusted = info->si_code > 0;
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bool signal_pid_trusted = info->si_code == SI_USER ||
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info->si_code == SI_TKILL;
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if (signal_trusted || (signal_pid_trusted && info->si_pid == getpid())) {
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sys_prctl(PR_SET_DUMPABLE, 1);
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}
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CrashContext context;
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memcpy(&context.siginfo, info, sizeof(siginfo_t));
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memcpy(&context.context, uc, sizeof(struct ucontext));
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#if !defined(__ARM_EABI__)
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// FP state is not part of user ABI on ARM Linux.
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struct ucontext *uc_ptr = (struct ucontext*)uc;
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if (uc_ptr->uc_mcontext.fpregs) {
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memcpy(&context.float_state,
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uc_ptr->uc_mcontext.fpregs,
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sizeof(context.float_state));
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}
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#endif
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context.tid = syscall(__NR_gettid);
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if (crash_handler_ != NULL) {
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if (crash_handler_(&context, sizeof(context),
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callback_context_)) {
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return true;
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}
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}
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return GenerateDump(&context);
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}
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// This function may run in a compromised context: see the top of the file.
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bool ExceptionHandler::GenerateDump(CrashContext *context) {
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if (IsOutOfProcess())
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return crash_generation_client_->RequestDump(context, sizeof(*context));
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static const unsigned kChildStackSize = 8000;
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PageAllocator allocator;
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uint8_t* stack = (uint8_t*) allocator.Alloc(kChildStackSize);
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if (!stack)
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return false;
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// clone() needs the top-most address. (scrub just to be safe)
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stack += kChildStackSize;
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my_memset(stack - 16, 0, 16);
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ThreadArgument thread_arg;
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thread_arg.handler = this;
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thread_arg.pid = getpid();
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thread_arg.context = context;
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thread_arg.context_size = sizeof(*context);
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// We need to explicitly enable ptrace of parent processes on some
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// kernels, but we need to know the PID of the cloned process before we
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// can do this. Create a pipe here which we can use to block the
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// cloned process after creating it, until we have explicitly enabled ptrace
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if(sys_pipe(fdes) == -1) {
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// Creating the pipe failed. We'll log an error but carry on anyway,
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// as we'll probably still get a useful crash report. All that will happen
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// is the write() and read() calls will fail with EBADF
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static const char no_pipe_msg[] = "ExceptionHandler::GenerateDump \
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sys_pipe failed:";
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sys_write(2, no_pipe_msg, sizeof(no_pipe_msg) - 1);
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sys_write(2, strerror(errno), strlen(strerror(errno)));
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sys_write(2, "\n", 1);
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}
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const pid_t child = sys_clone(
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ThreadEntry, stack, CLONE_FILES | CLONE_FS | CLONE_UNTRACED,
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&thread_arg, NULL, NULL, NULL);
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int r, status;
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// Allow the child to ptrace us
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prctl(PR_SET_PTRACER, child, 0, 0, 0);
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SendContinueSignalToChild();
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do {
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r = sys_waitpid(child, &status, __WALL);
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} while (r == -1 && errno == EINTR);
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sys_close(fdes[0]);
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sys_close(fdes[1]);
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if (r == -1) {
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static const char msg[] = "ExceptionHandler::GenerateDump waitpid failed:";
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sys_write(2, msg, sizeof(msg) - 1);
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sys_write(2, strerror(errno), strlen(strerror(errno)));
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sys_write(2, "\n", 1);
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}
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bool success = r != -1 && WIFEXITED(status) && WEXITSTATUS(status) == 0;
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if (callback_)
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success = callback_(dump_path_c_, next_minidump_id_c_,
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callback_context_, success);
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return success;
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}
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// This function runs in a compromised context: see the top of the file.
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void ExceptionHandler::SendContinueSignalToChild() {
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static const char okToContinueMessage = 'a';
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int r;
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r = HANDLE_EINTR(sys_write(fdes[1], &okToContinueMessage, sizeof(char)));
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if(r == -1) {
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static const char msg[] = "ExceptionHandler::SendContinueSignalToChild \
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sys_write failed:";
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sys_write(2, msg, sizeof(msg) - 1);
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sys_write(2, strerror(errno), strlen(strerror(errno)));
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sys_write(2, "\n", 1);
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}
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}
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// This function runs in a compromised context: see the top of the file.
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// Runs on the cloned process.
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void ExceptionHandler::WaitForContinueSignal() {
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int r;
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char receivedMessage;
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r = HANDLE_EINTR(sys_read(fdes[0], &receivedMessage, sizeof(char)));
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if(r == -1) {
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static const char msg[] = "ExceptionHandler::WaitForContinueSignal \
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sys_read failed:";
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sys_write(2, msg, sizeof(msg) - 1);
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sys_write(2, strerror(errno), strlen(strerror(errno)));
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sys_write(2, "\n", 1);
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}
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}
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// This function runs in a compromised context: see the top of the file.
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// Runs on the cloned process.
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bool ExceptionHandler::DoDump(pid_t crashing_process, const void* context,
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size_t context_size) {
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return google_breakpad::WriteMinidump(next_minidump_path_c_,
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crashing_process,
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context,
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context_size,
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mapping_list_);
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}
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// static
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bool ExceptionHandler::WriteMinidump(const std::string &dump_path,
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MinidumpCallback callback,
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void* callback_context) {
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ExceptionHandler eh(dump_path, NULL, callback, callback_context, false);
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return eh.WriteMinidump();
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}
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bool ExceptionHandler::WriteMinidump() {
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#if !defined(__ARM_EABI__)
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// Allow ourselves to be dumped.
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sys_prctl(PR_SET_DUMPABLE, 1);
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CrashContext context;
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int getcontext_result = getcontext(&context.context);
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if (getcontext_result)
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return false;
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memcpy(&context.float_state, context.context.uc_mcontext.fpregs,
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sizeof(context.float_state));
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context.tid = sys_gettid();
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bool success = GenerateDump(&context);
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UpdateNextID();
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return success;
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#else
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return false;
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#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);
|
|
}
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|
|
|
} // namespace google_breakpad
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