// 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.
#ifndef CRASHPAD_UTIL_MACH_EXC_SERVER_VARIANTS_H_
#define CRASHPAD_UTIL_MACH_EXC_SERVER_VARIANTS_H_
#include <mach/mach.h>
#include <memory>
#include <set>
#include "util/mach/mach_extensions.h"
#include "util/mach/mach_message_server.h"
namespace crashpad {
namespace internal {
class UniversalMachExcServerImpl;
} // namespace internal
//! \brief A server interface for the `exc` and `mach_exc` Mach subsystems,
//! unified to handle exceptions delivered to either subsystem, and
//! simplified to have only a single interface method needing
//! implementation.
//!
//! The `<mach/exc.defs>` and `<mach/mach_exc.defs>` interfaces are identical,
//! except that the latter allows for 64-bit exception codes, and is requested
//! by setting the MACH_EXCEPTION_CODES behavior bit associated with an
//! exception port.
//!
//! UniversalMachExcServer operates by translating messages received in the
//! `exc` subsystem to a variant that is compatible with the `mach_exc`
//! subsystem. This involves changing the format of \a code, the exception code
//! field, from `exception_data_type_t` to `mach_exception_data_type_t`.
class UniversalMachExcServer final : public MachMessageServer::Interface {
public:
//! \brief An interface that the different request messages that are a part of
//! the `exc` and `mach_exc` Mach subsystems can be dispatched to.
class Interface {
public:
//! \brief Handles exceptions raised by `exception_raise()`,
//! `exception_raise_state()`, `exception_raise_state_identity()`,
//! `mach_exception_raise()`, `mach_exception_raise_state()`, and
//! `mach_exception_raise_state_identity()`.
//!
//! For convenience in implementation, these different “behaviors” of
//! exception messages are all mapped to a single interface method. The
//! exception’s original “behavior” is specified in the \a behavior
//! parameter. Only parameters that were supplied in the request message
//! are populated, other parameters are set to reasonable default values.
//!
//! This behaves equivalently to a `catch_exception_raise_state_identity()`
//! function used with `exc_server()`, or a
//! `catch_mach_exception_raise_state_identity()` function used with
//! `mach_exc_server()`. Except as noted, the parameters and return value
//! are equivalent to those of these other functions.
//!
//! \param[in] behavior `EXCEPTION_DEFAULT`, `EXCEPTION_STATE`,
//! or `EXCEPTION_STATE_IDENTITY`, possibly with `MACH_EXCEPTION_CODES`
//! ORed in. This identifies which exception request message was
//! processed and thus which other parameters are valid.
//! \param[in] exception_port
//! \param[in] thread
//! \param[in] task
//! \param[in] exception
//! \param[in] code
//! \param[in] code_count
//! \param[in,out] flavor
//! \param[in] old_state
//! \param[in] old_state_count
//! \param[out] new_state
//! \param[out] new_state_count
//! \param[in] trailer The trailer received with the request message.
//! \param[out] destroy_complex_request `true` if the request message is to
//! be destroyed even when this method returns success. See
//! MachMessageServer::Interface.
//!
//! \return A code indicating whether the exception was handled. See
//! ExcServerSuccessfulReturnValue() for success codes. On failure,
//! a code such as `KERN_FAILURE`.
virtual 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) = 0;
protected:
~Interface() {}
};
//! \brief Constructs an object of this class.
//!
//! \param[in] interface The interface to dispatch requests to. Weak.
explicit UniversalMachExcServer(Interface* interface);
UniversalMachExcServer(const UniversalMachExcServer&) = delete;
UniversalMachExcServer& operator=(const UniversalMachExcServer&) = delete;
~UniversalMachExcServer();
// MachMessageServer::Interface:
bool MachMessageServerFunction(const mach_msg_header_t* in_header,
mach_msg_header_t* out_header,
bool* destroy_complex_request) override;
std::set<mach_msg_id_t> MachMessageServerRequestIDs() override;
mach_msg_size_t MachMessageServerRequestSize() override;
mach_msg_size_t MachMessageServerReplySize() override;
private:
std::unique_ptr<internal::UniversalMachExcServerImpl> impl_;
};
//! \brief Computes an approriate successful return value for an exception
//! handler function.
//!
//! For exception handlers that respond to state-carrying behaviors, when the
//! handler is called by the kernel (as it is normally), the kernel will attempt
//! to set a new thread state when the exception handler returns successfully.
//! Other code that mimics the kernel’s exception-delivery semantics may
//! implement the same or similar behavior. In some situations, it is
//! undesirable to set a new thread state. If the exception handler were to
//! return unsuccessfully, however, the kernel would continue searching for an
//! exception handler at a wider (task or host) scope. This may also be
//! undesirable.
//!
//! If such exception handlers return `MACH_RCV_PORT_DIED`, the kernel will not
//! set a new thread state and will also not search for another exception
//! handler. See 10.9.4 `xnu-2422.110.17/osfmk/kern/exception.c`.
//! `exception_deliver()` will only set a new thread state if the handler’s
//! return code was `MACH_MSG_SUCCESS` (a synonym for `KERN_SUCCESS`), and
//! subsequently, `exception_triage()` will not search for a new handler if the
//! handler’s return code was `KERN_SUCCESS` or `MACH_RCV_PORT_DIED`.
//!
//! This function allows exception handlers to compute an appropriate return
//! code to influence their caller (the kernel) in the desired way with respect
//! to setting a new thread state while suppressing the caller’s subsequent
//! search for other exception handlers. An exception handler should return the
//! value returned by this function.
//!
//! This function is useful even for `EXC_CRASH` handlers, where returning
//! `KERN_SUCCESS` and allowing the kernel to set a new thread state has been
//! observed to cause a perceptible and unnecessary waste of time. The victim
//! task in an `EXC_CRASH` handler is already being terminated and is no longer
//! schedulable, so there is no point in setting the states of any of its
//! threads.
//!
//! On OS X 10.11, the `MACH_RCV_PORT_DIED` mechanism cannot be used with an
//! `EXC_CRASH` handler without triggering an undesirable `EXC_CORPSE_NOTIFY`
//! exception. In that case, `KERN_SUCCESS` is always returned. Because this
//! function may return `KERN_SUCCESS` for a state-carrying exception, it is
//! important to ensure that the state returned by a state-carrying exception
//! handler is valid, because it will be passed to `thread_set_status()`.
//! ExcServerCopyState() may be used to achieve this.
//!
//! \param[in] exception The exception type passed to the exception handler.
//! This may be taken directly from the \a exception parameter of
//! internal::SimplifiedExcServer::Interface::CatchException(), for example.
//! \param[in] behavior The behavior of the exception handler as invoked. This
//! may be taken directly from the \a behavior parameter of
//! internal::SimplifiedExcServer::Interface::CatchException(), for example.
//! \param[in] set_thread_state `true` if the handler would like its caller to
//! set the new thread state using the \a flavor, \a new_state, and \a
//! new_state_count out parameters. This can only happen when \a behavior is
//! a state-carrying behavior.
//!
//! \return `KERN_SUCCESS` or `MACH_RCV_PORT_DIED`. `KERN_SUCCESS` is used when
//! \a behavior is not a state-carrying behavior, or when it is a
//! state-carrying behavior and \a set_thread_state is `true`, or for
//! `EXC_CRASH` exceptions on OS X 10.11 and later. Otherwise,
//! `MACH_RCV_PORT_DIED` is used.
kern_return_t ExcServerSuccessfulReturnValue(exception_type_t exception,
exception_behavior_t behavior,
bool set_thread_state);
//! \brief Copies the old state to the new state for state-carrying exceptions.
//!
//! When the kernel sends a state-carrying exception request and the response is
//! successful (`MACH_MSG_SUCCESS`, a synonym for `KERN_SUCCESS`), it will set
//! a new thread state based on \a new_state and \a new_state_count. To ease
//! initialization of the new state, this function copies \a old_state and
//! \a old_state_count. This is only done if \a behavior indicates a
//! state-carrying exception.
//!
//! \param[in] behavior The behavior of the exception handler as invoked. This
//! may be taken directly from the \a behavior parameter of
//! internal::SimplifiedExcServer::Interface::CatchException(), for example.
//! \param[in] old_state The original state value. This may be taken directly
//! from the \a old_state parameter of
//! internal::SimplifiedExcServer::Interface::CatchException(), for example.
//! \param[in] old_state_count The number of significant `natural_t` words in \a
//! old_state. This may be taken directly from the \a old_state_count
//! parameter of internal::SimplifiedExcServer::Interface::CatchException(),
//! for example.
//! \param[out] new_state The state value to be set. This may be taken directly
//! from the \a new_state parameter of
//! internal::SimplifiedExcServer::Interface::CatchException(), for example.
//! This parameter is untouched if \a behavior is not state-carrying.
//! \param[in,out] new_state_count On entry, the number of `natural_t` words
//! available to be written to in \a new_state. On return, the number of
//! significant `natural_t` words in \a new_state. This may be taken
//! directly from the \a new_state_count parameter of
//! internal::SimplifiedExcServer::Interface::CatchException(), for example.
//! This parameter is untouched if \a behavior is not state-carrying. If \a
//! \a behavior is state-carrying, this parameter should be at least as
//! large as \a old_state_count.
void ExcServerCopyState(exception_behavior_t behavior,
ConstThreadState old_state,
mach_msg_type_number_t old_state_count,
thread_state_t new_state,
mach_msg_type_number_t* new_state_count);
} // namespace crashpad
#endif // CRASHPAD_UTIL_MACH_EXC_SERVER_VARIANTS_H_
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