// Copyright 2014 The Crashpad Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "client/crashpad_client.h"
#include <errno.h>
#include <mach/mach.h>
#include <pthread.h>
#include <stdint.h>
#include <sys/wait.h>
#include <unistd.h>
#include <memory>
#include <utility>
#include "base/logging.h"
#include "base/mac/mach_logging.h"
#include "base/posix/eintr_wrapper.h"
#include "base/strings/stringprintf.h"
#include "util/mac/mac_util.h"
#include "util/mach/child_port_handshake.h"
#include "util/mach/exception_ports.h"
#include "util/mach/mach_extensions.h"
#include "util/mach/mach_message.h"
#include "util/mach/notify_server.h"
#include "util/misc/clock.h"
#include "util/misc/implicit_cast.h"
#include "util/posix/close_multiple.h"
namespace crashpad {
namespace {
std::string FormatArgumentString(const std::string& name,
const std::string& value) {
return base::StringPrintf("--%s=%s", name.c_str(), value.c_str());
}
std::string FormatArgumentInt(const std::string& name, int value) {
return base::StringPrintf("--%s=%d", name.c_str(), value);
}
// Set the exception handler for EXC_CRASH, EXC_RESOURCE, and EXC_GUARD.
//
// EXC_CRASH is how most crashes are received. Most other exception types such
// as EXC_BAD_ACCESS are delivered to a host-level exception handler in the
// kernel where they are converted to POSIX signals. See 10.9.5
// xnu-2422.115.4/bsd/uxkern/ux_exception.c catch_mach_exception_raise(). If a
// core-generating signal (triggered through this hardware mechanism or a
// software mechanism such as abort() sending SIGABRT) is unhandled and the
// process exits, or if the process is killed with SIGKILL for code-signing
// reasons, an EXC_CRASH exception will be sent. See 10.9.5
// xnu-2422.115.4/bsd/kern/kern_exit.c proc_prepareexit().
//
// EXC_RESOURCE and EXC_GUARD do not become signals or EXC_CRASH exceptions. The
// host-level exception handler in the kernel does not receive these exception
// types, and even if it did, it would not map them to signals. Instead, the
// first Mach service loaded by the root (process ID 1) launchd with a boolean
// “ExceptionServer” property in its job dictionary (regardless of its value) or
// with any subdictionary property will become the host-level exception handler
// for EXC_CRASH, EXC_RESOURCE, and EXC_GUARD. See 10.9.5
// launchd-842.92.1/src/core.c job_setup_exception_port(). Normally, this job is
// com.apple.ReportCrash.Root, the systemwide Apple Crash Reporter. Since it is
// impossible to receive EXC_RESOURCE and EXC_GUARD exceptions through the
// EXC_CRASH mechanism, an exception handler must be registered for them by name
// if it is to receive these exception types. The default task-level handler for
// these exception types is set by launchd in a similar manner.
//
// EXC_MASK_RESOURCE and EXC_MASK_GUARD are not available on all systems, and
// the kernel will reject attempts to use them if it does not understand them,
// so AND them with ExcMaskValid(). EXC_MASK_CRASH is always supported.
bool SetCrashExceptionPorts(exception_handler_t exception_handler) {
ExceptionPorts exception_ports(ExceptionPorts::kTargetTypeTask, TASK_NULL);
return exception_ports.SetExceptionPort(
(EXC_MASK_CRASH | EXC_MASK_RESOURCE | EXC_MASK_GUARD) & ExcMaskValid(),
exception_handler,
EXCEPTION_STATE_IDENTITY | MACH_EXCEPTION_CODES,
MACHINE_THREAD_STATE);
}
class ScopedPthreadAttrDestroy {
public:
explicit ScopedPthreadAttrDestroy(pthread_attr_t* pthread_attr)
: pthread_attr_(pthread_attr) {
}
~ScopedPthreadAttrDestroy() {
errno = pthread_attr_destroy(pthread_attr_);
PLOG_IF(WARNING, errno != 0) << "pthread_attr_destroy";
}
private:
pthread_attr_t* pthread_attr_;
DISALLOW_COPY_AND_ASSIGN(ScopedPthreadAttrDestroy);
};
//! \brief Starts a Crashpad handler, possibly restarting it if it dies.
class HandlerStarter final : public NotifyServer::DefaultInterface {
public:
~HandlerStarter() {}
//! \brief Starts a Crashpad handler initially, as opposed to starting it for
//! subsequent restarts.
//!
//! All parameters are as in CrashpadClient::StartHandler().
//!
//! \return On success, a send right to the Crashpad handler that has been
//! started. On failure, `MACH_PORT_NULL` with a message logged.
static base::mac::ScopedMachSendRight InitialStart(
const base::FilePath& handler,
const base::FilePath& database,
const base::FilePath& metrics_dir,
const std::string& url,
const std::map<std::string, std::string>& annotations,
const std::vector<std::string>& arguments,
bool restartable) {
base::mac::ScopedMachReceiveRight receive_right(
NewMachPort(MACH_PORT_RIGHT_RECEIVE));
if (!receive_right.is_valid()) {
return base::mac::ScopedMachSendRight();
}
mach_port_t port;
mach_msg_type_name_t right_type;
kern_return_t kr = mach_port_extract_right(mach_task_self(),
receive_right.get(),
MACH_MSG_TYPE_MAKE_SEND,
&port,
&right_type);
if (kr != KERN_SUCCESS) {
MACH_LOG(ERROR, kr) << "mach_port_extract_right";
return base::mac::ScopedMachSendRight();
}
base::mac::ScopedMachSendRight send_right(port);
DCHECK_EQ(port, receive_right.get());
DCHECK_EQ(right_type,
implicit_cast<mach_msg_type_name_t>(MACH_MSG_TYPE_PORT_SEND));
std::unique_ptr<HandlerStarter> handler_restarter;
if (restartable) {
handler_restarter.reset(new HandlerStarter());
if (!handler_restarter->notify_port_.is_valid()) {
// This is an error that NewMachPort() would have logged. Proceed anyway
// without the ability to restart.
handler_restarter.reset();
}
}
if (!CommonStart(handler,
database,
metrics_dir,
url,
annotations,
arguments,
std::move(receive_right),
handler_restarter.get(),
false)) {
return base::mac::ScopedMachSendRight();
}
if (handler_restarter &&
handler_restarter->StartRestartThread(
handler, database, metrics_dir, url, annotations, arguments)) {
// The thread owns the object now.
ignore_result(handler_restarter.release());
}
// If StartRestartThread() failed, proceed without the ability to restart.
// handler_restarter will be released when this function returns.
return send_right;
}
// NotifyServer::DefaultInterface:
kern_return_t DoMachNotifyPortDestroyed(notify_port_t notify,
mach_port_t rights,
const mach_msg_trailer_t* trailer,
bool* destroy_request) override {
// The receive right corresponding to this process’ crash exception port is
// now owned by this process. Any crashes that occur before the receive
// right is moved to a new handler process will cause the process to hang in
// an unkillable state prior to OS X 10.10.
if (notify != notify_port_) {
LOG(WARNING) << "notify port mismatch";
return KERN_FAILURE;
}
// If CommonStart() fails, the receive right will die, and this will just
// be called again for another try.
CommonStart(handler_,
database_,
metrics_dir_,
url_,
annotations_,
arguments_,
base::mac::ScopedMachReceiveRight(rights),
this,
true);
return KERN_SUCCESS;
}
private:
HandlerStarter()
: NotifyServer::DefaultInterface(),
handler_(),
database_(),
metrics_dir_(),
url_(),
annotations_(),
arguments_(),
notify_port_(NewMachPort(MACH_PORT_RIGHT_RECEIVE)),
last_start_time_(0) {
}
//! \brief Starts a Crashpad handler.
//!
//! All parameters are as in CrashpadClient::StartHandler(), with these
//! additions:
//!
//! \param[in] receive_right The receive right to move to the Crashpad
//! handler. The handler will use this receive right to run its exception
//! server.
//! \param[in] handler_restarter If CrashpadClient::StartHandler() was invoked
//! with \a restartable set to `true`, this is the restart state object.
//! Otherwise, this is `nullptr`.
//! \param[in] restart If CrashpadClient::StartHandler() was invoked with \a
//! restartable set to `true` and CommonStart() is being called to restart
//! a previously-started handler, this is `true`. Otherwise, this is
//! `false`.
//!
//! \return `true` on success, `false` on failure, with a message logged.
//! Failures include failure to start the handler process and failure to
//! rendezvous with it via ChildPortHandshake.
static bool CommonStart(const base::FilePath& handler,
const base::FilePath& database,
const base::FilePath& metrics_dir,
const std::string& url,
const std::map<std::string, std::string>& annotations,
const std::vector<std::string>& arguments,
base::mac::ScopedMachReceiveRight receive_right,
HandlerStarter* handler_restarter,
bool restart) {
DCHECK(!restart || handler_restarter);
if (handler_restarter) {
// The port-destroyed notification must be requested each time. It uses
// a send-once right, so once the notification is received, it won’t be
// sent again unless re-requested.
mach_port_t previous;
kern_return_t kr =
mach_port_request_notification(mach_task_self(),
receive_right.get(),
MACH_NOTIFY_PORT_DESTROYED,
0,
handler_restarter->notify_port_.get(),
MACH_MSG_TYPE_MAKE_SEND_ONCE,
&previous);
if (kr != KERN_SUCCESS) {
MACH_LOG(WARNING, kr) << "mach_port_request_notification";
// This will cause the restart thread to terminate after this restart
// attempt. There’s no longer any need for it, because no more
// port-destroyed notifications can be delivered.
handler_restarter->notify_port_.reset();
} else {
base::mac::ScopedMachSendRight previous_owner(previous);
DCHECK(restart || !previous_owner.is_valid());
}
if (restart) {
// If the handler was ever started before, don’t restart it too quickly.
const uint64_t kNanosecondsPerSecond = 1E9;
const uint64_t kMinimumStartInterval = 1 * kNanosecondsPerSecond;
const uint64_t earliest_next_start_time =
handler_restarter->last_start_time_ + kMinimumStartInterval;
const uint64_t now_time = ClockMonotonicNanoseconds();
if (earliest_next_start_time > now_time) {
const uint64_t sleep_time = earliest_next_start_time - now_time;
LOG(INFO) << "restarting handler"
<< base::StringPrintf(" in %.3fs",
static_cast<double>(sleep_time) /
kNanosecondsPerSecond);
SleepNanoseconds(earliest_next_start_time - now_time);
} else {
LOG(INFO) << "restarting handler";
}
}
handler_restarter->last_start_time_ = ClockMonotonicNanoseconds();
}
// Set up the arguments for execve() first. These aren’t needed until
// execve() is called, but it’s dangerous to do this in a child process
// after fork().
ChildPortHandshake child_port_handshake;
base::ScopedFD server_write_fd = child_port_handshake.ServerWriteFD();
// Use handler as argv[0], followed by arguments directed by this method’s
// parameters and a --handshake-fd argument. |arguments| are added first so
// that if it erroneously contains an argument such as --url, the actual
// |url| argument passed to this method will supersede it. In normal
// command-line processing, the last parameter wins in the case of a
// conflict.
std::vector<std::string> argv(1, handler.value());
argv.reserve(1 + arguments.size() + 2 + annotations.size() + 1);
for (const std::string& argument : arguments) {
argv.push_back(argument);
}
if (!database.value().empty()) {
argv.push_back(FormatArgumentString("database", database.value()));
}
if (!metrics_dir.value().empty()) {
argv.push_back(FormatArgumentString("metrics-dir", metrics_dir.value()));
}
if (!url.empty()) {
argv.push_back(FormatArgumentString("url", url));
}
for (const auto& kv : annotations) {
argv.push_back(
FormatArgumentString("annotation", kv.first + '=' + kv.second));
}
argv.push_back(FormatArgumentInt("handshake-fd", server_write_fd.get()));
const char* handler_c = handler.value().c_str();
// argv_c contains const char* pointers and is terminated by nullptr. argv
// is required because the pointers in argv_c need to point somewhere, and
// they can’t point to temporaries such as those returned by
// FormatArgumentString().
std::vector<const char*> argv_c;
argv_c.reserve(argv.size() + 1);
for (const std::string& argument : argv) {
argv_c.push_back(argument.c_str());
}
argv_c.push_back(nullptr);
// Double-fork(). The three processes involved are parent, child, and
// grandchild. The grandchild will become the handler process. The child
// exits immediately after spawning the grandchild, so the grandchild
// becomes an orphan and its parent process ID becomes 1. This relieves the
// parent and child of the responsibility for reaping the grandchild with
// waitpid() or similar. The handler process is expected to outlive the
// parent process, so the parent shouldn’t be concerned with reaping it.
// This approach means that accidental early termination of the handler
// process will not result in a zombie process.
pid_t pid = fork();
if (pid < 0) {
PLOG(ERROR) << "fork";
return false;
}
if (pid == 0) {
// Child process.
if (restart) {
// When restarting, reset the system default crash handler first.
// Otherwise, the crash exception port here will have been inherited
// from the parent process, which was probably using the exception
// server now being restarted. The handler can’t monitor itself for its
// own crashes via this interface.
CrashpadClient::UseSystemDefaultHandler();
}
// Call setsid(), creating a new process group and a new session, both led
// by this process. The new process group has no controlling terminal.
// This disconnects it from signals generated by the parent process’
// terminal.
//
// setsid() is done in the child instead of the grandchild so that the
// grandchild will not be a session leader. If it were a session leader,
// an accidental open() of a terminal device without O_NOCTTY would make
// that terminal the controlling terminal.
//
// It’s not desirable for the handler to have a controlling terminal. The
// handler monitors clients on its own and manages its own lifetime,
// exiting when it loses all clients and when it deems it appropraite to
// do so. It may serve clients in different process groups or sessions
// than its original client, and receiving signals intended for its
// original client’s process group could be harmful in that case.
PCHECK(setsid() != -1) << "setsid";
pid = fork();
if (pid < 0) {
PLOG(FATAL) << "fork";
}
if (pid > 0) {
// Child process.
// _exit() instead of exit(), because fork() was called.
_exit(EXIT_SUCCESS);
}
// Grandchild process.
CloseMultipleNowOrOnExec(STDERR_FILENO + 1, server_write_fd.get());
// &argv_c[0] is a pointer to a pointer to const char data, but because of
// how C (not C++) works, execvp() wants a pointer to a const pointer to
// char data. It modifies neither the data nor the pointers, so the
// const_cast is safe.
execvp(handler_c, const_cast<char* const*>(&argv_c[0]));
PLOG(FATAL) << "execvp " << handler_c;
}
// Parent process.
// Close the write side of the pipe, so that the handler process is the only
// process that can write to it.
server_write_fd.reset();
// waitpid() for the child, so that it does not become a zombie process. The
// child normally exits quickly.
int status;
pid_t wait_pid = HANDLE_EINTR(waitpid(pid, &status, 0));
PCHECK(wait_pid != -1) << "waitpid";
DCHECK_EQ(wait_pid, pid);
if (WIFSIGNALED(status)) {
LOG(WARNING) << "intermediate process: signal " << WTERMSIG(status);
} else if (!WIFEXITED(status)) {
DLOG(WARNING) << "intermediate process: unknown termination " << status;
} else if (WEXITSTATUS(status) != EXIT_SUCCESS) {
LOG(WARNING) << "intermediate process: exit status "
<< WEXITSTATUS(status);
}
// Rendezvous with the handler running in the grandchild process.
if (!child_port_handshake.RunClient(receive_right.get(),
MACH_MSG_TYPE_MOVE_RECEIVE)) {
return false;
}
ignore_result(receive_right.release());
return true;
}
bool StartRestartThread(const base::FilePath& handler,
const base::FilePath& database,
const base::FilePath& metrics_dir,
const std::string& url,
const std::map<std::string, std::string>& annotations,
const std::vector<std::string>& arguments) {
handler_ = handler;
database_ = database;
metrics_dir_ = metrics_dir;
url_ = url;
annotations_ = annotations;
arguments_ = arguments;
pthread_attr_t pthread_attr;
errno = pthread_attr_init(&pthread_attr);
if (errno != 0) {
PLOG(WARNING) << "pthread_attr_init";
return false;
}
ScopedPthreadAttrDestroy pthread_attr_owner(&pthread_attr);
errno = pthread_attr_setdetachstate(&pthread_attr, PTHREAD_CREATE_DETACHED);
if (errno != 0) {
PLOG(WARNING) << "pthread_attr_setdetachstate";
return false;
}
pthread_t pthread;
errno = pthread_create(&pthread, &pthread_attr, RestartThreadMain, this);
if (errno != 0) {
PLOG(WARNING) << "pthread_create";
return false;
}
return true;
}
static void* RestartThreadMain(void* argument) {
HandlerStarter* self = reinterpret_cast<HandlerStarter*>(argument);
NotifyServer notify_server(self);
mach_msg_return_t mr;
do {
mr = MachMessageServer::Run(¬ify_server,
self->notify_port_.get(),
0,
MachMessageServer::kPersistent,
MachMessageServer::kReceiveLargeError,
kMachMessageTimeoutWaitIndefinitely);
MACH_LOG_IF(ERROR, mr != MACH_MSG_SUCCESS, mr)
<< "MachMessageServer::Run";
} while (self->notify_port_.is_valid() && mr == MACH_MSG_SUCCESS);
delete self;
return nullptr;
}
base::FilePath handler_;
base::FilePath database_;
base::FilePath metrics_dir_;
std::string url_;
std::map<std::string, std::string> annotations_;
std::vector<std::string> arguments_;
base::mac::ScopedMachReceiveRight notify_port_;
uint64_t last_start_time_;
DISALLOW_COPY_AND_ASSIGN(HandlerStarter);
};
} // namespace
CrashpadClient::CrashpadClient() : exception_port_(MACH_PORT_NULL) {
}
CrashpadClient::~CrashpadClient() {
}
bool CrashpadClient::StartHandler(
const base::FilePath& handler,
const base::FilePath& database,
const base::FilePath& metrics_dir,
const std::string& url,
const std::map<std::string, std::string>& annotations,
const std::vector<std::string>& arguments,
bool restartable,
bool asynchronous_start) {
// The “restartable” behavior can only be selected on OS X 10.10 and later. In
// previous OS versions, if the initial client were to crash while attempting
// to restart the handler, it would become an unkillable process.
base::mac::ScopedMachSendRight exception_port(
HandlerStarter::InitialStart(handler,
database,
metrics_dir,
url,
annotations,
arguments,
restartable && MacOSXMinorVersion() >= 10));
if (!exception_port.is_valid()) {
return false;
}
SetHandlerMachPort(std::move(exception_port));
return true;
}
bool CrashpadClient::SetHandlerMachService(const std::string& service_name) {
base::mac::ScopedMachSendRight exception_port(BootstrapLookUp(service_name));
if (!exception_port.is_valid()) {
return false;
}
SetHandlerMachPort(std::move(exception_port));
return true;
}
bool CrashpadClient::SetHandlerMachPort(
base::mac::ScopedMachSendRight exception_port) {
DCHECK(!exception_port_.is_valid());
DCHECK(exception_port.is_valid());
if (!SetCrashExceptionPorts(exception_port.get())) {
return false;
}
exception_port_.swap(exception_port);
return true;
}
base::mac::ScopedMachSendRight CrashpadClient::GetHandlerMachPort() const {
DCHECK(exception_port_.is_valid());
// For the purposes of this method, only return a port set by
// SetHandlerMachPort().
//
// It would be possible to use task_get_exception_ports() to look up the
// EXC_CRASH task exception port, but that’s probably not what users of this
// interface really want. If CrashpadClient is asked for the handler Mach
// port, it should only return a port that it knows about by virtue of having
// set it. It shouldn’t return any EXC_CRASH task exception port in effect if
// SetHandlerMachPort() was never called, and it shouldn’t return any
// EXC_CRASH task exception port that might be set by other code after
// SetHandlerMachPort() is called.
//
// The caller is accepting its own new ScopedMachSendRight, so increment the
// reference count of the underlying right.
kern_return_t kr = mach_port_mod_refs(
mach_task_self(), exception_port_.get(), MACH_PORT_RIGHT_SEND, 1);
if (kr != KERN_SUCCESS) {
MACH_LOG(ERROR, kr) << "mach_port_mod_refs";
return base::mac::ScopedMachSendRight(MACH_PORT_NULL);
}
return base::mac::ScopedMachSendRight(exception_port_.get());
}
// static
void CrashpadClient::UseSystemDefaultHandler() {
base::mac::ScopedMachSendRight
system_crash_reporter_handler(SystemCrashReporterHandler());
// Proceed even if SystemCrashReporterHandler() failed, setting MACH_PORT_NULL
// to clear the current exception ports.
if (!SetCrashExceptionPorts(system_crash_reporter_handler.get())) {
SetCrashExceptionPorts(MACH_PORT_NULL);
}
}
} // namespace crashpad