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// Copyright 2020 The Crashpad Authors
//
// 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 <signal.h>
#include <unistd.h>
#include <atomic>
#include <ios>
#include <iterator>
#include "base/apple/mach_logging.h"
#include "base/apple/scoped_mach_port.h"
#include "base/logging.h"
#include "client/ios_handler/exception_processor.h"
#include "client/ios_handler/in_process_handler.h"
#include "util/ios/raw_logging.h"
#include "util/mach/exc_server_variants.h"
#include "util/mach/exception_ports.h"
#include "util/mach/mach_extensions.h"
#include "util/mach/mach_message.h"
#include "util/mach/mach_message_server.h"
#include "util/misc/initialization_state_dcheck.h"
#include "util/posix/signals.h"
#include "util/thread/thread.h"
namespace {
bool IsBeingDebugged() {
kinfo_proc kern_proc_info;
int mib[] = {CTL_KERN, KERN_PROC, KERN_PROC_PID, getpid()};
size_t len = sizeof(kern_proc_info);
if (sysctl(mib, std::size(mib), &kern_proc_info, &len, nullptr, 0) == 0)
return kern_proc_info.kp_proc.p_flag & P_TRACED;
return false;
}
} // namespace
namespace crashpad {
namespace {
// A base class for signal handler and Mach exception server.
class CrashHandler : public Thread,
public UniversalMachExcServer::Interface,
public ObjcExceptionDelegate {
public:
CrashHandler(const CrashHandler&) = delete;
CrashHandler& operator=(const CrashHandler&) = delete;
static CrashHandler* Get() {
if (!instance_)
instance_ = new CrashHandler();
return instance_;
}
static void ResetForTesting() {
delete instance_;
instance_ = nullptr;
}
bool Initialize(
const base::FilePath& database,
const std::string& url,
const std::map<std::string, std::string>& annotations,
internal::InProcessHandler::ProcessPendingReportsObservationCallback
callback) {
INITIALIZATION_STATE_SET_INITIALIZING(initialized_);
if (!in_process_handler_.Initialize(database, url, annotations, callback) ||
!InstallMachExceptionHandler() ||
// xnu turns hardware faults into Mach exceptions, so the only signal
// left to register is SIGABRT, which never starts off as a hardware
// fault. Installing a handler for other signals would lead to
// recording exceptions twice. As a consequence, Crashpad will not
// generate intermediate dumps for anything manually calling
// raise(SIG*). In practice, this doesn’t actually happen for crash
// signals that originate as hardware faults.
!Signals::InstallHandler(
SIGABRT, CatchAndReraiseSignal, 0, &old_action_)) {
LOG(ERROR) << "Unable to initialize Crashpad.";
return false;
}
// For applications that haven't ignored or set a handler for SIGPIPE:
// It’s OK for an application to set its own SIGPIPE handler (including
// SIG_IGN) before initializing Crashpad, because Crashpad will discover the
// existing handler and not install its own.
// It’s OK for Crashpad to install its own SIGPIPE handler and for the
// application to subsequently install its own (including SIG_IGN)
// afterwards, because its handler will replace Crashpad’s.
// This is useful to cover the default situation where nobody installs a
// SIGPIPE handler and the disposition is at SIG_DFL, because SIGPIPE is a
// “kill” signal (bsd/sys/signalvar.h sigprop). In that case, without
// Crashpad, SIGPIPE results in a silent and unreported kill (and not even
// ReportCrash will record it), but developers probably want to be alerted
// to the conditon.
struct sigaction sa;
if (sigaction(SIGPIPE, nullptr, &sa) == 0 && sa.sa_handler == SIG_DFL) {
Signals::InstallHandler(
SIGPIPE, CatchAndReraiseSignalDefaultAction, 0, nullptr);
}
InstallObjcExceptionPreprocessor(this);
INITIALIZATION_STATE_SET_VALID(initialized_);
return true;
}
void ProcessIntermediateDumps(
const std::map<std::string, std::string>& annotations) {
in_process_handler_.ProcessIntermediateDumps(annotations);
}
void ProcessIntermediateDump(
const base::FilePath& file,
const std::map<std::string, std::string>& annotations) {
in_process_handler_.ProcessIntermediateDump(file, annotations);
}
void DumpWithoutCrash(NativeCPUContext* context, bool process_dump) {
INITIALIZATION_STATE_DCHECK_VALID(initialized_);
base::FilePath path;
if (!in_process_handler_.DumpExceptionFromSimulatedMachException(
context, kMachExceptionSimulated, &path)) {
return;
}
if (process_dump) {
in_process_handler_.ProcessIntermediateDump(path);
}
}
void DumpWithoutCrashAtPath(NativeCPUContext* context,
const base::FilePath& path) {
in_process_handler_.DumpExceptionFromSimulatedMachExceptionAtPath(
context, kMachExceptionSimulated, path);
}
void StartProcessingPendingReports(UploadBehavior upload_behavior) {
INITIALIZATION_STATE_DCHECK_VALID(initialized_);
in_process_handler_.StartProcessingPendingReports(upload_behavior);
}
void SetMachExceptionCallbackForTesting(void (*callback)()) {
in_process_handler_.SetMachExceptionCallbackForTesting(callback);
}
uint64_t GetThreadIdForTesting() { return Thread::GetThreadIdForTesting(); }
private:
CrashHandler() = default;
~CrashHandler() {
UninstallObjcExceptionPreprocessor();
Signals::InstallDefaultHandler(SIGABRT);
UninstallMachExceptionHandler();
}
bool InstallMachExceptionHandler() {
exception_port_.reset(NewMachPort(MACH_PORT_RIGHT_RECEIVE));
if (!exception_port_.is_valid()) {
return false;
}
kern_return_t kr = mach_port_insert_right(mach_task_self(),
exception_port_.get(),
exception_port_.get(),
MACH_MSG_TYPE_MAKE_SEND);
if (kr != KERN_SUCCESS) {
MACH_LOG(ERROR, kr) << "mach_port_insert_right";
return false;
}
// TODO: Use SwapExceptionPort instead and put back EXC_MASK_BREAKPOINT.
// Until then, remove |EXC_MASK_BREAKPOINT| while attached to a debugger.
exception_mask_t mask =
ExcMaskAll() &
~(EXC_MASK_EMULATION | EXC_MASK_SOFTWARE | EXC_MASK_RPC_ALERT |
EXC_MASK_GUARD | (IsBeingDebugged() ? EXC_MASK_BREAKPOINT : 0));
ExceptionPorts exception_ports(ExceptionPorts::kTargetTypeTask, TASK_NULL);
if (!exception_ports.GetExceptionPorts(mask, &original_handlers_) ||
!exception_ports.SetExceptionPort(
mask,
exception_port_.get(),
EXCEPTION_STATE_IDENTITY | MACH_EXCEPTION_CODES,
MACHINE_THREAD_STATE)) {
return false;
}
mach_handler_running_ = true;
Start();
return true;
}
void UninstallMachExceptionHandler() {
mach_handler_running_ = false;
exception_port_.reset();
Join();
}
// Thread:
void ThreadMain() override {
UniversalMachExcServer universal_mach_exc_server(this);
while (mach_handler_running_) {
mach_msg_return_t mr =
MachMessageServer::Run(&universal_mach_exc_server,
exception_port_.get(),
MACH_MSG_OPTION_NONE,
MachMessageServer::kPersistent,
MachMessageServer::kReceiveLargeIgnore,
kMachMessageTimeoutWaitIndefinitely);
MACH_CHECK(
mach_handler_running_
? mr == MACH_SEND_INVALID_DEST // This shouldn't happen for
// exception messages that come
// from the kernel itself, but if
// something else in-process sends
// exception messages and breaks,
// handle that case.
: (mr == MACH_RCV_PORT_CHANGED || // Port was closed while the
// thread was listening.
mr == MACH_RCV_INVALID_NAME), // Port was closed before the
// thread started listening.
mr)
<< "MachMessageServer::Run";
}
}
// UniversalMachExcServer::Interface:
kern_return_t CatchMachException(exception_behavior_t behavior,
exception_handler_t exception_port,
thread_t thread,
task_t task,
exception_type_t exception,
const mach_exception_data_type_t* code,
mach_msg_type_number_t code_count,
thread_state_flavor_t* flavor,
ConstThreadState old_state,
mach_msg_type_number_t old_state_count,
thread_state_t new_state,
mach_msg_type_number_t* new_state_count,
const mach_msg_trailer_t* trailer,
bool* destroy_complex_request) override {
*destroy_complex_request = true;
// TODO(justincohen): Forward exceptions to original_handlers_ with
// UniversalExceptionRaise.
// iOS shouldn't have any child processes, but just in case, those will
// inherit the task exception ports, and this process isn’t prepared to
// handle them
if (task != mach_task_self()) {
CRASHPAD_RAW_LOG("MachException task != mach_task_self()");
return KERN_FAILURE;
}
HandleMachException(behavior,
thread,
exception,
code,
code_count,
*flavor,
old_state,
old_state_count);
// Respond with KERN_FAILURE so the system will continue to handle this
// exception. xnu will turn this Mach exception into a signal and take the
// default action to terminate the process. However, if sigprocmask is
// called before this Mach exception returns (such as by another thread
// calling abort, see: Libc-1506.40.4/stdlib/FreeBSD/abort.c), the Mach
// exception will be converted into a signal but delivery will be blocked.
// Since concurrent exceptions lead to the losing thread sleeping
// indefinitely, if the abort thread never returns, the thread that
// triggered this Mach exception will repeatedly trap and the process will
// never terminate. If the abort thread didn’t have a user-space signal
// handler that slept forever, the abort would terminate the process even if
// all other signals had been blocked. Instead, unblock all signals
// corresponding to all Mach exceptions Crashpad is registered for before
// returning KERN_FAILURE. There is still racy behavior possible with this
// call to sigprocmask, but the repeated calls to CatchMachException here
// will eventually lead to termination.
sigset_t unblock_set;
sigemptyset(&unblock_set);
sigaddset(&unblock_set, SIGILL); // EXC_BAD_INSTRUCTION
sigaddset(&unblock_set, SIGTRAP); // EXC_BREAKPOINT
sigaddset(&unblock_set, SIGFPE); // EXC_ARITHMETIC
sigaddset(&unblock_set, SIGBUS); // EXC_BAD_ACCESS
sigaddset(&unblock_set, SIGSEGV); // EXC_BAD_ACCESS
if (sigprocmask(SIG_UNBLOCK, &unblock_set, nullptr) != 0) {
CRASHPAD_RAW_LOG("sigprocmask");
}
return KERN_FAILURE;
}
void HandleMachException(exception_behavior_t behavior,
thread_t thread,
exception_type_t exception,
const mach_exception_data_type_t* code,
mach_msg_type_number_t code_count,
thread_state_flavor_t flavor,
ConstThreadState old_state,
mach_msg_type_number_t old_state_count) {
in_process_handler_.DumpExceptionFromMachException(behavior,
thread,
exception,
code,
code_count,
flavor,
old_state,
old_state_count);
}
void HandleUncaughtNSException(const uint64_t* frames,
const size_t num_frames) override {
in_process_handler_.DumpExceptionFromNSExceptionWithFrames(frames,
num_frames);
// After uncaught exceptions are reported, the system immediately triggers a
// call to std::terminate()/abort(). Remove the abort handler so a second
// dump isn't generated.
CHECK(Signals::InstallDefaultHandler(SIGABRT));
}
void HandleUncaughtNSExceptionWithContext(
NativeCPUContext* context) override {
base::FilePath path;
in_process_handler_.DumpExceptionFromSimulatedMachException(
context, kMachExceptionFromNSException, &path);
// After uncaught exceptions are reported, the system immediately triggers a
// call to std::terminate()/abort(). Remove the abort handler so a second
// dump isn't generated.
CHECK(Signals::InstallDefaultHandler(SIGABRT));
}
void HandleUncaughtNSExceptionWithContextAtPath(
NativeCPUContext* context,
const base::FilePath& path) override {
in_process_handler_.DumpExceptionFromSimulatedMachExceptionAtPath(
context, kMachExceptionFromNSException, path);
}
bool MoveIntermediateDumpAtPathToPending(
const base::FilePath& path) override {
if (in_process_handler_.MoveIntermediateDumpAtPathToPending(path)) {
// After uncaught exceptions are reported, the system immediately triggers
// a call to std::terminate()/abort(). Remove the abort handler so a
// second dump isn't generated.
CHECK(Signals::InstallDefaultHandler(SIGABRT));
return true;
}
return false;
}
// The signal handler installed at OS-level.
static void CatchAndReraiseSignal(int signo,
siginfo_t* siginfo,
void* context) {
Get()->HandleAndReraiseSignal(signo,
siginfo,
reinterpret_cast<ucontext_t*>(context),
&(Get()->old_action_));
}
static void CatchAndReraiseSignalDefaultAction(int signo,
siginfo_t* siginfo,
void* context) {
Get()->HandleAndReraiseSignal(
signo, siginfo, reinterpret_cast<ucontext_t*>(context), nullptr);
}
void HandleAndReraiseSignal(int signo,
siginfo_t* siginfo,
ucontext_t* context,
struct sigaction* old_action) {
in_process_handler_.DumpExceptionFromSignal(siginfo, context);
// Always call system handler.
Signals::RestoreHandlerAndReraiseSignalOnReturn(siginfo, old_action);
}
base::apple::ScopedMachReceiveRight exception_port_;
ExceptionPorts::ExceptionHandlerVector original_handlers_;
struct sigaction old_action_ = {};
internal::InProcessHandler in_process_handler_;
static CrashHandler* instance_;
std::atomic<bool> mach_handler_running_ = false;
InitializationStateDcheck initialized_;
};
CrashHandler* CrashHandler::instance_ = nullptr;
} // namespace
CrashpadClient::CrashpadClient() {}
CrashpadClient::~CrashpadClient() {}
// static
bool CrashpadClient::StartCrashpadInProcessHandler(
const base::FilePath& database,
const std::string& url,
const std::map<std::string, std::string>& annotations,
ProcessPendingReportsObservationCallback callback) {
CrashHandler* crash_handler = CrashHandler::Get();
DCHECK(crash_handler);
return crash_handler->Initialize(database, url, annotations, callback);
}
// static
void CrashpadClient::ProcessIntermediateDumps(
const std::map<std::string, std::string>& annotations) {
CrashHandler* crash_handler = CrashHandler::Get();
DCHECK(crash_handler);
crash_handler->ProcessIntermediateDumps(annotations);
}
// static
void CrashpadClient::ProcessIntermediateDump(
const base::FilePath& file,
const std::map<std::string, std::string>& annotations) {
CrashHandler* crash_handler = CrashHandler::Get();
DCHECK(crash_handler);
crash_handler->ProcessIntermediateDump(file, annotations);
}
// static
void CrashpadClient::StartProcessingPendingReports(
UploadBehavior upload_behavior) {
CrashHandler* crash_handler = CrashHandler::Get();
DCHECK(crash_handler);
crash_handler->StartProcessingPendingReports(upload_behavior);
}
// static
void CrashpadClient::DumpWithoutCrash(NativeCPUContext* context) {
CrashHandler* crash_handler = CrashHandler::Get();
DCHECK(crash_handler);
crash_handler->DumpWithoutCrash(context, /*process_dump=*/true);
}
// static
void CrashpadClient::DumpWithoutCrashAndDeferProcessing(
NativeCPUContext* context) {
CrashHandler* crash_handler = CrashHandler::Get();
DCHECK(crash_handler);
crash_handler->DumpWithoutCrash(context, /*process_dump=*/false);
}
// static
void CrashpadClient::DumpWithoutCrashAndDeferProcessingAtPath(
NativeCPUContext* context,
const base::FilePath path) {
CrashHandler* crash_handler = CrashHandler::Get();
DCHECK(crash_handler);
crash_handler->DumpWithoutCrashAtPath(context, path);
}
void CrashpadClient::ResetForTesting() {
CrashHandler* crash_handler = CrashHandler::Get();
DCHECK(crash_handler);
crash_handler->ResetForTesting();
}
void CrashpadClient::SetMachExceptionCallbackForTesting(void (*callback)()) {
CrashHandler* crash_handler = CrashHandler::Get();
DCHECK(crash_handler);
crash_handler->SetMachExceptionCallbackForTesting(callback);
}
uint64_t CrashpadClient::GetThreadIdForTesting() {
CrashHandler* crash_handler = CrashHandler::Get();
DCHECK(crash_handler);
return crash_handler->GetThreadIdForTesting();
}
} // namespace crashpad