This is xnu-8019. See this file in:
/*
 * Copyright (c) 2021 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
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#ifndef _IOKIT_UIOEVENTLINK_H
#define _IOKIT_UIOEVENTLINK_H

#include <DriverKit/IODispatchQueue.iig>
#include <DriverKit/IODispatchSource.iig>
#include <DriverKit/IOUserClient.iig>

enum {
	kIOEventLinkMaxNameLength = 64,
};

// IOEventLink::Associate() options
enum {
	kIOEventLinkAssociateCurrentThread   = 0x00000000,
    kIOEventLinkAssociateOnWait          = 0x00000001,
};

// Clock options
enum {
    kIOEventLinkClockMachAbsoluteTime = 0x0,
};

/*!
 * @class IOEventLink
 *
 * @abstract
 * IOEventLink allows for fast IPC, suitable for
 * realtime applications.
 *
 * @discussion
 *
 * Applications that open user clients to a DriverKit driver can set up an eventlink
 * for fast signaling.
 *
 * To configure an eventlink, the application will have to first create an eventlink object
 * with os_eventlink_create() (see <os/eventlink_private.h>). The application then has to extract
 * the remote eventlink port with os_eventlink_extract_remote_port(). To send the remote eventlink port
 * to the driver, use:
 *
 * const char * name = "Event Link Name"; // This must match the name the driver used in IOEventLink::Create().
 * kern_return_t ret = IOConnectTrap3(connect, // user client connection (io_connect_t)
 *                                    0, // specifies event link configuration trap
 *                                    (uintptr_t)name,
 *                                    (uintptr_t)strlen(name),
 *                                    (uintptr_t)remotePort // port from os_eventlink_extract_remote_port
 *                                    );
 *
 * Once the remote eventlink port has been sent to the driver, the driver should be notified with a user-defined external method
 * or other existing signaling mechanism. The driver should handle this by activating the IOEventLink with Activate().
 */
class NATIVE KERNEL IOEventLink : public OSObject
{
public:

    virtual bool
    init() override;

    virtual void
    free() override;

    /*!
     * @brief       Create an IOEventLink.
     * @param       name       User-specified name. If an IOEventLink with the same name already exists in the specified
     *                         user client, the old IOEventLink will be replaced.
     * @param       userClient  Userclient to create the eventlink in. The DriverKit runtime will retain the userclient, and will
     *                          release it in Invalidate() or when the IOEventLink is freed.
     * @param       eventLink  Created IOEventLink with +1 retain count to be released by the caller.
     * @return      kIOReturnSuccess on success. See IOReturn.h for error codes.
     */
    static kern_return_t
    Create(OSString * name, IOUserClient * userClient, IOEventLink ** eventLink) LOCAL;

#if DRIVERKIT_PRIVATE

    /*!
     * @brief       Set the port for this eventlink.
     * @discussion  This is not meant to be used directly.
     * @param       port Eventlink port
     * @return      kIOReturnSuccess on success. See IOReturn.h for error codes.
     */
    virtual kern_return_t
    SetEventlinkPort(mach_port_t port PORTCOPYSEND) LOCAL;

#endif /* DRIVERKIT_PRIVATE */

    /*
     * @brief       Signal the eventlink. If a thread is waiting on the eventlink, this will wake up that thread.
     * @discussion  This API call is real time safe.
     * @return      kIOReturnSuccess on success. See IOReturn.h for error codes.
     */
    kern_return_t
    Signal() LOCALONLY;

    /*
     * @brief       Wait on the eventlink.
     * @discussion  This API call is real time safe.
     * @return      kIOReturnSuccess on success. See IOReturn.h for error codes.
     */
    kern_return_t
    Wait(uint64_t * signalsConsumed) LOCALONLY;

    /*
     * @brief       Signal the eventlink and wait. If a thread is waiting on the eventlink, this will wake up that thread.
     * @discussion  This API call is real time safe.
     * @param       signalsConsumed   When the calling thread wakes up, the amount of signals consumed by the wait will be written here.
     * @return      kIOReturnSuccess on success. See IOReturn.h for error codes.
     */
    kern_return_t
    SignalAndWait(uint64_t * signalsConsumed) LOCALONLY;

    /*
     * @brief       Signal the eventlink and wait with a timeout. If a thread is waiting on the eventlink, this will wake up that thread.
     * @discussion  This API call is real time safe.
     * @param       signalsConsumed   When the calling thread wakes up, the amount of signals consumed by the wait will be written here.
     * @param       clockOptions      Options for which clock to use. The only currently supported option is kIOEventLinkClockMachAbsoluteTime.
     * @param       timeout           Timeout
     * @return      kIOReturnSuccess on success. See IOReturn.h for error codes.
     */
    kern_return_t
    SignalAndWaitUntil(uint64_t clockOptions, uint64_t timeout, uint64_t * signalsConsumed) LOCALONLY;

    /*
     * @brief       Wait with a timeout. If a thread is waiting on the eventlink, this will wake up that thread.
     * @discussion  This API call is real time safe.
     * @param       signalsConsumed   When the calling thread wakes up, the amount of signals consumed by the wait will be written here.
     * @param       clockOptions      Options for which clock to use. The only currently supported option is kIOEventLinkClockMachAbsoluteTime.
     * @param       timeout           Timeout
     * @return      kIOReturnSuccess on success. See IOReturn.h for error codes.
     */
    kern_return_t
    WaitUntil(uint64_t clockOptions, uint64_t timeout, uint64_t * signalsConsumed) LOCALONLY;

    /*!
     * @brief       Cancel the event link.
     * @discussion  If a thread is waiting on the eventlink, cancellation will wake up that thread.
     * @return      kIOReturnSuccess on success. See IOReturn.h for error codes.
     */
    kern_return_t
    Cancel() LOCALONLY;

    /*!
     * @brief       Activate the event link.
     * @discussion  The event link must be activated before it can be signaled or waited on. This is not real-time safe.
     * @return      kIOReturnSuccess on success. See IOReturn.h for error codes.
     */
    kern_return_t
    Activate() LOCALONLY;

    /*!
     * @brief       Associate a thread with the eventlink. 
     * @discussion  The eventlink should be activated before this call. This is not real-time safe.
     * @param       options  Options for Associate(). Use kIOEventLinkAssociateCurrentThread or kIOEventLinkAssociateOnWait.
     * @return      kIOReturnSuccess on success. See IOReturn.h for error codes.
     */
    kern_return_t
    Associate(uint64_t options) LOCALONLY;

    /*!
     * @brief       Disassociate the current thread from the eventlink. This is not real-time safe.
     * @return      kIOReturnSuccess on success. See IOReturn.h for error codes.
     */
    kern_return_t
    Disassociate() LOCALONLY;

    /*!
     * @brief       Invalidate the IOEventLink.
     * @discussion  This releases the kernel reference to the IOEventLink, allowing the name to be used for a different
     *              IOEventLink. This method should be called after the client has configured the eventlink with the IOConnectTrap
     *              call. After invalidation, the IOEventLink can no longer be configured through the IOConnectTrap call. No other
     *              functionality is affected.
     * @return      kIOReturnSuccess on success. See IOReturn.h for error codes.
     */
    kern_return_t
    Invalidate() LOCALONLY;

#if DRIVERKIT_PRIVATE

    virtual kern_return_t
    InvalidateKernel(IOUserClient * client);

#endif /* DRIVERKIT_PRIVATE */
};

#endif /* ! _IOKIT_UIOEVENTLINK_H */