// Copyright 2014 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/simulate_crash_mac.h"
#include <string.h>
#include <sys/types.h>
#include <iterator>
#include "base/apple/mach_logging.h"
#include "base/apple/scoped_mach_port.h"
#include "base/check_op.h"
#include "base/logging.h"
#include "build/build_config.h"
#include "util/mach/exc_client_variants.h"
#include "util/mach/exception_behaviors.h"
#include "util/mach/exception_ports.h"
#include "util/mach/mach_extensions.h"
#include "util/misc/implicit_cast.h"
namespace crashpad {
namespace {
//! \brief Sends an exception message to an exception port in accordance with
//! the behavior and thread state flavor it’s registered to receive.
//!
//! \param[in] thread, task, exception, code, code_count These parameters will
//! be passed to the exception handler as appropriate.
//! \param[in] cpu_context The value to use for the thread state, if \a behavior
//! indicates that the handler should receive a thread state and if the
//! supplied thread state matches or can be converted to \a flavor. If \a
//! behavior requires a thread state but this argument cannot be converted
//! to match \a flavor, `thread_get_state()` will be called to obtain a
//! suitable thread state value.
//! \param[in] handler The Mach exception handler to deliver the exception to.
//! \param[in] set_state If `true` and \a behavior indicates that the handler
//! should receive and return a thread state, a new thread state will be set
//! by `thread_set_state()` upon successful completion of the exception
//! handler. If `false`, this will be suppressed, even when \a behavior
//! indicates that the handler receives and returns a thread state.
//!
//! \return `true` if the exception was delivered to the handler and the handler
//! indicated success. `false` otherwise, with a warning message logged.
bool DeliverException(thread_t thread,
task_t task,
exception_type_t exception,
const mach_exception_data_t code,
mach_msg_type_number_t code_count,
const NativeCPUContext& cpu_context,
const ExceptionPorts::ExceptionHandler& handler,
bool set_state) {
kern_return_t kr;
bool handler_wants_state = ExceptionBehaviorHasState(handler.behavior);
if (!handler_wants_state) {
// Regardless of the passed-in value of |set_state|, if the handler won’t be
// dealing with any state at all, no state should be set.
set_state = false;
}
// old_state is only used if the context already captured doesn’t match (or
// can’t be converted to) what’s registered for the handler.
thread_state_data_t old_state;
thread_state_flavor_t flavor = handler.flavor;
ConstThreadState state;
mach_msg_type_number_t state_count;
switch (flavor) {
#if defined(ARCH_CPU_X86_FAMILY)
case x86_THREAD_STATE:
state = reinterpret_cast<ConstThreadState>(&cpu_context);
state_count = x86_THREAD_STATE_COUNT;
break;
#if defined(ARCH_CPU_X86)
case x86_THREAD_STATE32:
state = reinterpret_cast<ConstThreadState>(&cpu_context.uts.ts32);
state_count = cpu_context.tsh.count;
break;
#elif defined(ARCH_CPU_X86_64)
case x86_THREAD_STATE64:
state = reinterpret_cast<ConstThreadState>(&cpu_context.uts.ts64);
state_count = cpu_context.tsh.count;
break;
#endif
#elif defined(ARCH_CPU_ARM64)
case ARM_UNIFIED_THREAD_STATE:
state = reinterpret_cast<ConstThreadState>(&cpu_context);
state_count = ARM_UNIFIED_THREAD_STATE_COUNT;
break;
case ARM_THREAD_STATE64:
state = reinterpret_cast<ConstThreadState>(&cpu_context.ts_64);
state_count = cpu_context.ash.count;
break;
#else
#error Port to your CPU architecture
#endif
case THREAD_STATE_NONE:
// This is only acceptable if the handler doesn’t have one of the “state”
// behaviors. Otherwise, if the kernel were attempting to send an
// exception message to this port, it would call thread_getstatus() (known
// outside the kernel as thread_get_state()) which would fail because
// THREAD_STATE_NONE is not a valid state to get. See 10.9.5
// xnu-2422.115.4/osfmk/kern/exception.c exception_deliver() and
// xnu-2422.115.4/osfmk/i386/pcb.c machine_thread_get_state().
if (!handler_wants_state) {
state = nullptr;
state_count = 0;
break;
}
LOG(WARNING) << "exception handler has unexpected state flavor" << flavor;
return false;
default:
if (!handler_wants_state) {
// Don’t bother getting any thread state if the handler’s not actually
// going to use it.
state = nullptr;
state_count = 0;
} else {
state = old_state;
state_count = THREAD_STATE_MAX;
kr = thread_get_state(thread, flavor, old_state, &state_count);
if (kr != KERN_SUCCESS) {
MACH_LOG(WARNING, kr) << "thread_get_state";
return false;
}
}
break;
}
// new_state is supposed to be an out parameter only, but in case the handler
// doesn't touch it, make sure it's initialized to a valid thread state.
// Otherwise, the thread_set_state() call below would set a garbage thread
// state.
thread_state_data_t new_state;
size_t state_size =
sizeof(natural_t) *
std::min(state_count, implicit_cast<unsigned int>(THREAD_STATE_MAX));
memcpy(new_state, state, state_size);
mach_msg_type_number_t new_state_count = THREAD_STATE_MAX;
kr = UniversalExceptionRaise(handler.behavior,
handler.port,
thread,
task,
exception,
code,
code_count,
&flavor,
state,
state_count,
new_state,
&new_state_count);
// The kernel treats a return value of MACH_RCV_PORT_DIED as successful,
// although it will not set a new thread state in that case. See 10.9.5
// xnu-2422.115.4/osfmk/kern/exception.c exception_deliver(), and the more
// elaborate comment at util/mach/exc_server_variants.h
// ExcServerSuccessfulReturnValue(). Duplicate that behavior.
bool success = kr == KERN_SUCCESS || kr == MACH_RCV_PORT_DIED;
MACH_LOG_IF(WARNING, !success, kr) << "UniversalExceptionRaise";
if (kr == KERN_SUCCESS && set_state) {
kr = thread_set_state(thread, flavor, new_state, new_state_count);
MACH_LOG_IF(WARNING, kr != KERN_SUCCESS, kr) << "thread_set_state";
}
return success;
}
} // namespace
void SimulateCrash(const NativeCPUContext& cpu_context) {
#if defined(ARCH_CPU_X86)
DCHECK_EQ(implicit_cast<thread_state_flavor_t>(cpu_context.tsh.flavor),
implicit_cast<thread_state_flavor_t>(x86_THREAD_STATE32));
DCHECK_EQ(implicit_cast<mach_msg_type_number_t>(cpu_context.tsh.count),
x86_THREAD_STATE32_COUNT);
#elif defined(ARCH_CPU_X86_64)
DCHECK_EQ(implicit_cast<thread_state_flavor_t>(cpu_context.tsh.flavor),
implicit_cast<thread_state_flavor_t>(x86_THREAD_STATE64));
DCHECK_EQ(implicit_cast<mach_msg_type_number_t>(cpu_context.tsh.count),
x86_THREAD_STATE64_COUNT);
#elif defined(ARCH_CPU_ARM64)
DCHECK_EQ(implicit_cast<thread_state_flavor_t>(cpu_context.ash.flavor),
implicit_cast<thread_state_flavor_t>(ARM_THREAD_STATE64));
DCHECK_EQ(implicit_cast<mach_msg_type_number_t>(cpu_context.ash.count),
ARM_THREAD_STATE64_COUNT);
#else
#error Port to your CPU architecture
#endif
base::apple::ScopedMachSendRight thread(mach_thread_self());
exception_type_t exception = kMachExceptionSimulated;
mach_exception_data_type_t codes[] = {0, 0};
mach_msg_type_number_t code_count = std::size(codes);
// Look up the handler for EXC_CRASH exceptions in the same way that the
// kernel would: try a thread handler, then a task handler, and finally a host
// handler. 10.9.5 xnu-2422.115.4/osfmk/kern/exception.c exception_triage().
static constexpr ExceptionPorts::TargetType kTargetTypes[] = {
ExceptionPorts::kTargetTypeThread,
ExceptionPorts::kTargetTypeTask,
// This is not expected to succeed, because mach_host_self() doesn’t
// return the host_priv port to non-root users, and this is the port
// that’s required for host_get_exception_ports().
//
// See 10.9.5 xnu-2422.115.4/bsd/kern/kern_prot.c set_security_token(),
// xnu-2422.115.4/osfmk/kern/task.c host_security_set_task_token(), and
// xnu-2422.115.4/osfmk/kern/ipc_host.c host_get_exception_ports().
ExceptionPorts::kTargetTypeHost,
};
bool success = false;
for (size_t target_type_index = 0;
!success && target_type_index < std::size(kTargetTypes);
++target_type_index) {
ExceptionPorts::ExceptionHandlerVector handlers;
ExceptionPorts exception_ports(kTargetTypes[target_type_index],
MACH_PORT_NULL);
if (exception_ports.GetExceptionPorts(EXC_MASK_CRASH, &handlers)) {
DCHECK_LE(handlers.size(), 1u);
if (handlers.size() == 1) {
DCHECK(handlers[0].mask & EXC_MASK_CRASH);
success = DeliverException(thread.get(),
mach_task_self(),
exception,
codes,
code_count,
cpu_context,
handlers[0],
false);
}
}
}
LOG_IF(WARNING, !success)
<< "SimulateCrash did not find an appropriate exception handler";
}
} // namespace crashpad
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