text: /*
   * Copyright (c) 2003-2019 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
   * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
   * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
   * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
   * Please see the License for the specific language governing rights and
   * limitations under the License.
   *
   * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
   */
  /*-
   * Copyright (c) 1999,2000,2001 Jonathan Lemon <jlemon@FreeBSD.org>
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   *
   *	$FreeBSD: src/sys/sys/event.h,v 1.5.2.5 2001/12/14 19:21:22 jlemon Exp $
   */
  
  #ifndef _SYS_EVENT_H_
  #define _SYS_EVENT_H_
  
  #include <machine/types.h>
  #include <sys/cdefs.h>
  #include <stdint.h>
  
  /*
   * Filter types
   */
  #define EVFILT_READ             (-1)
  #define EVFILT_WRITE            (-2)
  #define EVFILT_AIO              (-3)    /* attached to aio requests */
  #define EVFILT_VNODE            (-4)    /* attached to vnodes */
  #define EVFILT_PROC             (-5)    /* attached to struct proc */
  #define EVFILT_SIGNAL           (-6)    /* attached to struct proc */
  #define EVFILT_TIMER            (-7)    /* timers */
  #define EVFILT_MACHPORT         (-8)    /* Mach portsets */
  #define EVFILT_FS               (-9)    /* Filesystem events */
  #define EVFILT_USER             (-10)   /* User events */
  #ifdef PRIVATE
  #define EVFILT_UNUSED_11        (-11)   /* (-11) unused */
  #endif
  #define EVFILT_VM               (-12)   /* Virtual memory events */
  #ifdef PRIVATE
  #define EVFILT_SOCK             (-13)   /* Socket events */
  #define EVFILT_MEMORYSTATUS     (-14)   /* Memorystatus events */
  #endif /* PRIVATE */
  #define EVFILT_EXCEPT           (-15)   /* Exception events */
  #ifdef PRIVATE
  #define EVFILT_WORKLOOP         (-17)   /* Workloop events */
  #endif /* PRIVATE */
  
  #define EVFILT_SYSCOUNT         17
  #define EVFILT_THREADMARKER     EVFILT_SYSCOUNT /* Internal use only */
  
  #pragma pack(4)
  
  struct kevent {
  	uintptr_t       ident;  /* identifier for this event */
  	int16_t         filter; /* filter for event */
  	uint16_t        flags;  /* general flags */
  	uint32_t        fflags; /* filter-specific flags */
  	intptr_t        data;   /* filter-specific data */
  	void            *udata; /* opaque user data identifier */
  };
  
  #ifdef KERNEL_PRIVATE
  
  struct user64_kevent {
  	uint64_t        ident;  /* identifier for this event */
  	int16_t         filter; /* filter for event */
  	uint16_t        flags;  /* general flags */
  	uint32_t        fflags; /* filter-specific flags */
  	int64_t         data;   /* filter-specific data */
  	user_addr_t     udata;  /* opaque user data identifier */
  };
  
  struct user32_kevent {
  	uint32_t        ident;  /* identifier for this event */
  	int16_t         filter; /* filter for event */
  	uint16_t        flags;  /* general flags */
  	uint32_t        fflags; /* filter-specific flags */
  	int32_t         data;   /* filter-specific data */
  	user32_addr_t   udata;  /* opaque user data identifier */
  };
  
  #endif /* KERNEL_PRIVATE */
  
  #pragma pack()
  
  struct kevent64_s {
  	uint64_t        ident;          /* identifier for this event */
  	int16_t         filter;         /* filter for event */
  	uint16_t        flags;          /* general flags */
  	uint32_t        fflags;         /* filter-specific flags */
  	int64_t         data;           /* filter-specific data */
  	uint64_t        udata;          /* opaque user data identifier */
  	uint64_t        ext[2];         /* filter-specific extensions */
  };
  
  #ifdef PRIVATE
  struct kevent_qos_s {
  	uint64_t        ident;          /* identifier for this event */
  	int16_t         filter;         /* filter for event */
  	uint16_t        flags;          /* general flags */
  	int32_t         qos;            /* quality of service */
  	uint64_t        udata;          /* opaque user data identifier */
  	uint32_t        fflags;         /* filter-specific flags */
  	uint32_t        xflags;         /* extra filter-specific flags */
  	int64_t         data;           /* filter-specific data */
  	uint64_t        ext[4];         /* filter-specific extensions */
  };
  
  /*
   * Type definition for names/ids of dynamically allocated kqueues.
   */
  typedef uint64_t kqueue_id_t;
  #endif /* PRIVATE */
  
  #define EV_SET(kevp, a, b, c, d, e, f) do {     \
  	struct kevent *__kevp__ = (kevp);       \
  	__kevp__->ident = (a);                  \
  	__kevp__->filter = (b);                 \
  	__kevp__->flags = (c);                  \
  	__kevp__->fflags = (d);                 \
  	__kevp__->data = (e);                   \
  	__kevp__->udata = (f);                  \
  } while(0)
  
  #define EV_SET64(kevp, a, b, c, d, e, f, g, h) do {     \
  	struct kevent64_s *__kevp__ = (kevp);           \
  	__kevp__->ident = (a);                          \
  	__kevp__->filter = (b);                         \
  	__kevp__->flags = (c);                          \
  	__kevp__->fflags = (d);                         \
  	__kevp__->data = (e);                           \
  	__kevp__->udata = (f);                          \
  	__kevp__->ext[0] = (g);                         \
  	__kevp__->ext[1] = (h);                         \
  } while(0)
  
  
  /* kevent system call flags */
  #define KEVENT_FLAG_NONE                         0x000000       /* no flag value */
  #define KEVENT_FLAG_IMMEDIATE                    0x000001       /* immediate timeout */
  #define KEVENT_FLAG_ERROR_EVENTS                 0x000002       /* output events only include change errors */
  
  #ifdef PRIVATE
  
  /*
   * Rather than provide an EV_SET_QOS macro for kevent_qos_t structure
   * initialization, we encourage use of named field initialization support
   * instead.
   */
  
  // was  KEVENT_FLAG_STACK_EVENTS                 0x000004
  #define KEVENT_FLAG_STACK_DATA                   0x000008   /* output data allocated as stack (grows down) */
  //      KEVENT_FLAG_POLL                         0x000010
  #define KEVENT_FLAG_WORKQ                        0x000020   /* interact with the default workq kq */
  //      KEVENT_FLAG_LEGACY32                     0x000040
  //      KEVENT_FLAG_LEGACY64                     0x000080
  //      KEVENT_FLAG_PROC64                       0x000100
  #define KEVENT_FLAG_WORKQ_MANAGER                0x000200   /* obsolete */
  #define KEVENT_FLAG_WORKLOOP                     0x000400   /* interact with the specified workloop kq */
  #define KEVENT_FLAG_PARKING                      0x000800   /* workq thread is parking */
  //      KEVENT_FLAG_KERNEL                       0x001000
  //      KEVENT_FLAG_DYNAMIC_KQUEUE               0x002000
  //      KEVENT_FLAG_NEEDS_END_PROCESSING         0x004000
  #define KEVENT_FLAG_WORKLOOP_SERVICER_ATTACH     0x008000   /* obsolete */
  #define KEVENT_FLAG_WORKLOOP_SERVICER_DETACH     0x010000   /* obsolete */
  #define KEVENT_FLAG_DYNAMIC_KQ_MUST_EXIST        0x020000   /* kq lookup by id must exist */
  #define KEVENT_FLAG_DYNAMIC_KQ_MUST_NOT_EXIST    0x040000   /* kq lookup by id must not exist */
  #define KEVENT_FLAG_WORKLOOP_NO_WQ_THREAD        0x080000   /* obsolete */
  
  #ifdef XNU_KERNEL_PRIVATE
  
  #define KEVENT_FLAG_POLL                         0x0010  /* Call is for poll() */
  #define KEVENT_FLAG_LEGACY32                     0x0040  /* event data in legacy 32-bit format */
  #define KEVENT_FLAG_LEGACY64                     0x0080  /* event data in legacy 64-bit format */
  #define KEVENT_FLAG_PROC64                       0x0100  /* proc is 64bits */
  #define KEVENT_FLAG_KERNEL                       0x1000  /* caller is in-kernel */
  #define KEVENT_FLAG_DYNAMIC_KQUEUE               0x2000  /* kqueue is dynamically allocated */
  #define KEVENT_FLAG_NEEDS_END_PROCESSING         0x4000  /* end processing required before returning */
  
  #define KEVENT_ID_FLAG_USER (KEVENT_FLAG_WORKLOOP | \
  	        KEVENT_FLAG_DYNAMIC_KQ_MUST_EXIST | KEVENT_FLAG_DYNAMIC_KQ_MUST_NOT_EXIST)
  
  #define KEVENT_FLAG_USER (KEVENT_FLAG_IMMEDIATE | KEVENT_FLAG_ERROR_EVENTS | \
  	        KEVENT_FLAG_STACK_DATA | KEVENT_FLAG_WORKQ | KEVENT_FLAG_WORKLOOP | \
  	        KEVENT_FLAG_DYNAMIC_KQ_MUST_EXIST | KEVENT_FLAG_DYNAMIC_KQ_MUST_NOT_EXIST)
  
  /*
   * Since some filter ops are not part of the standard sysfilt_ops, we use
   * kn_filtid starting from EVFILT_SYSCOUNT to identify these cases.  This is to
   * let kn_fops() get the correct fops for all cases.
   */
  #define EVFILTID_KQREAD            (EVFILT_SYSCOUNT)
  #define EVFILTID_PIPE_N            (EVFILT_SYSCOUNT + 1)
  #define EVFILTID_PIPE_R            (EVFILT_SYSCOUNT + 2)
  #define EVFILTID_PIPE_W            (EVFILT_SYSCOUNT + 3)
  #define EVFILTID_PTSD              (EVFILT_SYSCOUNT + 4)
  #define EVFILTID_SOREAD            (EVFILT_SYSCOUNT + 5)
  #define EVFILTID_SOWRITE           (EVFILT_SYSCOUNT + 6)
  #define EVFILTID_SCK               (EVFILT_SYSCOUNT + 7)
  #define EVFILTID_SOEXCEPT          (EVFILT_SYSCOUNT + 8)
  #define EVFILTID_SPEC              (EVFILT_SYSCOUNT + 9)
  #define EVFILTID_BPFREAD           (EVFILT_SYSCOUNT + 10)
  #define EVFILTID_NECP_FD           (EVFILT_SYSCOUNT + 11)
  #define EVFILTID_FSEVENT           (EVFILT_SYSCOUNT + 15)
  #define EVFILTID_VN                (EVFILT_SYSCOUNT + 16)
  #define EVFILTID_TTY               (EVFILT_SYSCOUNT + 17)
  #define EVFILTID_PTMX              (EVFILT_SYSCOUNT + 18)
  
  #define EVFILTID_DETACHED          (EVFILT_SYSCOUNT + 19)
  #define EVFILTID_MAX               (EVFILT_SYSCOUNT + 20)
  
  #endif /* defined(XNU_KERNEL_PRIVATE) */
  
  #define EV_SET_QOS 0
  
  #endif /* PRIVATE */
  
  /* actions */
  #define EV_ADD              0x0001      /* add event to kq (implies enable) */
  #define EV_DELETE           0x0002      /* delete event from kq */
  #define EV_ENABLE           0x0004      /* enable event */
  #define EV_DISABLE          0x0008      /* disable event (not reported) */
  
  /* flags */
  #define EV_ONESHOT          0x0010      /* only report one occurrence */
  #define EV_CLEAR            0x0020      /* clear event state after reporting */
  #define EV_RECEIPT          0x0040      /* force immediate event output */
                                          /* ... with or without EV_ERROR */
                                          /* ... use KEVENT_FLAG_ERROR_EVENTS */
                                          /*     on syscalls supporting flags */
  
  #define EV_DISPATCH         0x0080      /* disable event after reporting */
  #define EV_UDATA_SPECIFIC   0x0100      /* unique kevent per udata value */
  
  #define EV_DISPATCH2        (EV_DISPATCH | EV_UDATA_SPECIFIC)
  /* ... in combination with EV_DELETE */
  /* will defer delete until udata-specific */
  /* event enabled. EINPROGRESS will be */
  /* returned to indicate the deferral */
  
  #define EV_VANISHED         0x0200      /* report that source has vanished  */
                                          /* ... only valid with EV_DISPATCH2 */
  
  #define EV_SYSFLAGS         0xF000      /* reserved by system */
  #define EV_FLAG0            0x1000      /* filter-specific flag */
  #define EV_FLAG1            0x2000      /* filter-specific flag */
  
  /* returned values */
  #define EV_EOF              0x8000      /* EOF detected */
  #define EV_ERROR            0x4000      /* error, data contains errno */
  
  /*
   * Filter specific flags for EVFILT_READ
   *
   * The default behavior for EVFILT_READ is to make the "read" determination
   * relative to the current file descriptor read pointer.
   *
   * The EV_POLL flag indicates the determination should be made via poll(2)
   * semantics. These semantics dictate always returning true for regular files,
   * regardless of the amount of unread data in the file.
   *
   * On input, EV_OOBAND specifies that filter should actively return in the
   * presence of OOB on the descriptor. It implies that filter will return
   * if there is OOB data available to read OR when any other condition
   * for the read are met (for example number of bytes regular data becomes >=
   * low-watermark).
   * If EV_OOBAND is not set on input, it implies that the filter should not actively
   * return for out of band data on the descriptor. The filter will then only return
   * when some other condition for read is met (ex: when number of regular data bytes
   * >=low-watermark OR when socket can't receive more data (SS_CANTRCVMORE)).
   *
   * On output, EV_OOBAND indicates the presence of OOB data on the descriptor.
   * If it was not specified as an input parameter, then the data count is the
   * number of bytes before the current OOB marker, else data count is the number
   * of bytes beyond OOB marker.
   */
  #define EV_POLL         EV_FLAG0
  #define EV_OOBAND       EV_FLAG1
  
  /*
   * data/hint fflags for EVFILT_USER, shared with userspace
   */
  
  /*
   * On input, NOTE_TRIGGER causes the event to be triggered for output.
   */
  #define NOTE_TRIGGER    0x01000000
  
  /*
   * On input, the top two bits of fflags specifies how the lower twenty four
   * bits should be applied to the stored value of fflags.
   *
   * On output, the top two bits will always be set to NOTE_FFNOP and the
   * remaining twenty four bits will contain the stored fflags value.
   */
  #define NOTE_FFNOP      0x00000000              /* ignore input fflags */
  #define NOTE_FFAND      0x40000000              /* and fflags */
  #define NOTE_FFOR       0x80000000              /* or fflags */
  #define NOTE_FFCOPY     0xc0000000              /* copy fflags */
  #define NOTE_FFCTRLMASK 0xc0000000              /* mask for operations */
  #define NOTE_FFLAGSMASK 0x00ffffff
  
  #ifdef PRIVATE
  /*
   * data/hint fflags for EVFILT_WORKLOOP, shared with userspace
   *
   * The ident for thread requests should be the dynamic ID of the workloop
   * The ident for each sync waiter must be unique to that waiter [for this workloop]
   *
   *
   * Commands:
   *
   * @const NOTE_WL_THREAD_REQUEST [in/out]
   * The kevent represents asynchronous userspace work and its associated QoS.
   * There can only be a single knote with this flag set per workloop.
   *
   * @const NOTE_WL_SYNC_WAIT [in/out]
   * This bit is set when the caller is waiting to become the owner of a workloop.
   * If the NOTE_WL_SYNC_WAKE bit is already set then the caller is not blocked,
   * else it blocks until it is set.
   *
   * The QoS field of the knote is used to push on other owners or servicers.
   *
   * @const NOTE_WL_SYNC_WAKE [in/out]
   * Marks the waiter knote as being eligible to become an owner
   * This bit can only be set once, trying it again will fail with EALREADY.
   *
   * @const NOTE_WL_SYNC_IPC [in/out]
   * The knote is a sync IPC redirected turnstile push.
   *
   * Flags/Modifiers:
   *
   * @const NOTE_WL_UPDATE_QOS [in] (only NOTE_WL_THREAD_REQUEST)
   * For successful updates (EV_ADD only), learn the new userspace async QoS from
   * the kevent qos field.
   *
   * @const NOTE_WL_END_OWNERSHIP [in]
   * If the update is successful (including deletions) or returns ESTALE, and
   * the caller thread or the "suspended" thread is currently owning the workloop,
   * then ownership is forgotten.
   *
   * @const NOTE_WL_DISCOVER_OWNER [in]
   * If the update is successful (including deletions), learn the owner identity
   * from the loaded value during debounce. This requires an address to have been
   * filled in the EV_EXTIDX_WL_ADDR ext field, but doesn't require a mask to have
   * been set in the EV_EXTIDX_WL_MASK.
   *
   * @const NOTE_WL_IGNORE_ESTALE [in]
   * If the operation would fail with ESTALE, mask the error and pretend the
   * update was successful. However the operation itself didn't happen, meaning
   * that:
   * - attaching a new knote will not happen
   * - dropping an existing knote will not happen
   * - NOTE_WL_UPDATE_QOS or NOTE_WL_DISCOVER_OWNER will have no effect
   *
   * This modifier doesn't affect NOTE_WL_END_OWNERSHIP.
   */
  #define NOTE_WL_THREAD_REQUEST   0x00000001
  #define NOTE_WL_SYNC_WAIT        0x00000004
  #define NOTE_WL_SYNC_WAKE        0x00000008
  #define NOTE_WL_SYNC_IPC         0x80000000
  #define NOTE_WL_COMMANDS_MASK    0x8000000f /* Mask of all the [in] commands above */
  
  #define NOTE_WL_UPDATE_QOS       0x00000010
  #define NOTE_WL_END_OWNERSHIP    0x00000020
  #define NOTE_WL_DISCOVER_OWNER   0x00000080
  #define NOTE_WL_IGNORE_ESTALE    0x00000100
  #define NOTE_WL_UPDATES_MASK     0x000001f0 /* Mask of all the [in] updates above */
  
  #define NOTE_WL_UPDATE_OWNER     0 /* ... compatibility define ... */
  
  /*
   * EVFILT_WORKLOOP ext[] array indexes/meanings.
   */
  #define EV_EXTIDX_WL_LANE        0         /* lane identifier  [in: sync waiter]
  	                                    *                  [out: thread request]     */
  #define EV_EXTIDX_WL_ADDR        1         /* debounce address [in: NULL==no debounce]   */
  #define EV_EXTIDX_WL_MASK        2         /* debounce mask    [in]                      */
  #define EV_EXTIDX_WL_VALUE       3         /* debounce value   [in: not current->ESTALE]
  	                                    *                  [out: new/debounce value] */
  
  #endif /* PRIVATE */
  
  /*
   * data/hint fflags for EVFILT_{READ|WRITE}, shared with userspace
   *
   * The default behavior for EVFILT_READ is to make the determination
   * realtive to the current file descriptor read pointer.
   */
  #define NOTE_LOWAT      0x00000001              /* low water mark */
  
  /* data/hint flags for EVFILT_EXCEPT, shared with userspace */
  #define NOTE_OOB        0x00000002              /* OOB data */
  
  /*
   * data/hint fflags for EVFILT_VNODE, shared with userspace
   */
  #define NOTE_DELETE     0x00000001              /* vnode was removed */
  #define NOTE_WRITE      0x00000002              /* data contents changed */
  #define NOTE_EXTEND     0x00000004              /* size increased */
  #define NOTE_ATTRIB     0x00000008              /* attributes changed */
  #define NOTE_LINK       0x00000010              /* link count changed */
  #define NOTE_RENAME     0x00000020              /* vnode was renamed */
  #define NOTE_REVOKE     0x00000040              /* vnode access was revoked */
  #define NOTE_NONE       0x00000080              /* No specific vnode event: to test for EVFILT_READ activation*/
  #define NOTE_FUNLOCK    0x00000100              /* vnode was unlocked by flock(2) */
  
  /*
   * data/hint fflags for EVFILT_PROC, shared with userspace
   *
   * Please note that EVFILT_PROC and EVFILT_SIGNAL share the same knote list
   * that hangs off the proc structure. They also both play games with the hint
   * passed to KNOTE(). If NOTE_SIGNAL is passed as a hint, then the lower bits
   * of the hint contain the signal. IF NOTE_FORK is passed, then the lower bits
   * contain the PID of the child (but the pid does not get passed through in
   * the actual kevent).
   */
  enum {
  	eNoteReapDeprecated __deprecated_enum_msg("This kqueue(2) EVFILT_PROC flag is deprecated") = 0x10000000
  };
  
  #define NOTE_EXIT               0x80000000      /* process exited */
  #define NOTE_FORK               0x40000000      /* process forked */
  #define NOTE_EXEC               0x20000000      /* process exec'd */
  #define NOTE_REAP               ((unsigned int)eNoteReapDeprecated /* 0x10000000 */ )   /* process reaped */
  #define NOTE_SIGNAL             0x08000000      /* shared with EVFILT_SIGNAL */
  #define NOTE_EXITSTATUS         0x04000000      /* exit status to be returned, valid for child process or when allowed to signal target pid */
  #define NOTE_EXIT_DETAIL        0x02000000      /* provide details on reasons for exit */
  
  #define NOTE_PDATAMASK  0x000fffff              /* mask for signal & exit status */
  #define NOTE_PCTRLMASK  (~NOTE_PDATAMASK)
  
  /*
   * If NOTE_EXITSTATUS is present, provide additional info about exiting process.
   */
  enum {
  	eNoteExitReparentedDeprecated __deprecated_enum_msg("This kqueue(2) EVFILT_PROC flag is no longer sent") = 0x00080000
  };
  #define NOTE_EXIT_REPARENTED    ((unsigned int)eNoteExitReparentedDeprecated)   /* exited while reparented */
  
  /*
   * If NOTE_EXIT_DETAIL is present, these bits indicate specific reasons for exiting.
   */
  #define NOTE_EXIT_DETAIL_MASK           0x00070000
  #define NOTE_EXIT_DECRYPTFAIL           0x00010000
  #define NOTE_EXIT_MEMORY                0x00020000
  #define NOTE_EXIT_CSERROR               0x00040000
  
  #ifdef PRIVATE
  
  /*
   * If NOTE_EXIT_MEMORY is present, these bits indicate specific jetsam condition.
   */
  #define NOTE_EXIT_MEMORY_DETAIL_MASK    0xfe000000
  #define NOTE_EXIT_MEMORY_VMPAGESHORTAGE 0x80000000      /* jetsam condition: lowest jetsam priority proc killed due to vm page shortage */
  #define NOTE_EXIT_MEMORY_VMTHRASHING    0x40000000      /* jetsam condition: lowest jetsam priority proc killed due to vm thrashing */
  #define NOTE_EXIT_MEMORY_HIWAT          0x20000000      /* jetsam condition: process reached its high water mark */
  #define NOTE_EXIT_MEMORY_PID            0x10000000      /* jetsam condition: special pid kill requested */
  #define NOTE_EXIT_MEMORY_IDLE           0x08000000      /* jetsam condition: idle process cleaned up */
  #define NOTE_EXIT_MEMORY_VNODE          0X04000000      /* jetsam condition: virtual node kill */
  #define NOTE_EXIT_MEMORY_FCTHRASHING    0x02000000      /* jetsam condition: lowest jetsam priority proc killed due to filecache thrashing */
  
  #endif
  
  /*
   * data/hint fflags for EVFILT_VM, shared with userspace.
   */
  #define NOTE_VM_PRESSURE                        0x80000000              /* will react on memory pressure */
  #define NOTE_VM_PRESSURE_TERMINATE              0x40000000              /* will quit on memory pressure, possibly after cleaning up dirty state */
  #define NOTE_VM_PRESSURE_SUDDEN_TERMINATE       0x20000000              /* will quit immediately on memory pressure */
  #define NOTE_VM_ERROR                           0x10000000              /* there was an error */
  
  #ifdef PRIVATE
  
  /*
   * data/hint fflags for EVFILT_MEMORYSTATUS, shared with userspace.
   */
  #define NOTE_MEMORYSTATUS_PRESSURE_NORMAL       0x00000001      /* system memory pressure has returned to normal */
  #define NOTE_MEMORYSTATUS_PRESSURE_WARN         0x00000002      /* system memory pressure has changed to the warning state */
  #define NOTE_MEMORYSTATUS_PRESSURE_CRITICAL     0x00000004      /* system memory pressure has changed to the critical state */
  #define NOTE_MEMORYSTATUS_LOW_SWAP              0x00000008      /* system is in a low-swap state */
  #define NOTE_MEMORYSTATUS_PROC_LIMIT_WARN       0x00000010      /* process memory limit has hit a warning state */
  #define NOTE_MEMORYSTATUS_PROC_LIMIT_CRITICAL   0x00000020      /* process memory limit has hit a critical state - soft limit */
  #define NOTE_MEMORYSTATUS_MSL_STATUS   0xf0000000      /* bits used to request change to process MSL status */
  
  #ifdef KERNEL_PRIVATE
  /*
   * data/hint fflags for EVFILT_MEMORYSTATUS, but not shared with userspace.
   */
  #define NOTE_MEMORYSTATUS_PROC_LIMIT_WARN_ACTIVE        0x00000040      /* Used to restrict sending a warn event only once, per active limit, soft limits only */
  #define NOTE_MEMORYSTATUS_PROC_LIMIT_WARN_INACTIVE      0x00000080      /* Used to restrict sending a warn event only once, per inactive limit, soft limit only */
  #define NOTE_MEMORYSTATUS_PROC_LIMIT_CRITICAL_ACTIVE    0x00000100      /* Used to restrict sending a critical event only once per active limit, soft limit only */
  #define NOTE_MEMORYSTATUS_PROC_LIMIT_CRITICAL_INACTIVE  0x00000200      /* Used to restrict sending a critical event only once per inactive limit, soft limit only */
  #define NOTE_MEMORYSTATUS_JETSAM_FG_BAND                0x00000400      /* jetsam is approaching foreground band */
  
  /*
   * Use this mask to protect the kernel private flags.
   */
  #define EVFILT_MEMORYSTATUS_ALL_MASK \
  	(NOTE_MEMORYSTATUS_PRESSURE_NORMAL | NOTE_MEMORYSTATUS_PRESSURE_WARN | NOTE_MEMORYSTATUS_PRESSURE_CRITICAL | NOTE_MEMORYSTATUS_LOW_SWAP | \
  	 NOTE_MEMORYSTATUS_PROC_LIMIT_WARN | NOTE_MEMORYSTATUS_PROC_LIMIT_CRITICAL | NOTE_MEMORYSTATUS_MSL_STATUS)
  
  #endif /* KERNEL_PRIVATE */
  
  typedef enum vm_pressure_level {
  	kVMPressureNormal   = 0,
  	kVMPressureWarning  = 1,
  	kVMPressureUrgent   = 2,
  	kVMPressureCritical = 3,
  	kVMPressureJetsam   = 4,  /* jetsam approaching FG bands */
  } vm_pressure_level_t;
  
  #endif /* PRIVATE */
  
  /*
   * data/hint fflags for EVFILT_TIMER, shared with userspace.
   * The default is a (repeating) interval timer with the data
   * specifying the timeout interval in milliseconds.
   *
   * All timeouts are implicitly EV_CLEAR events.
   */
  #define NOTE_SECONDS    0x00000001              /* data is seconds         */
  #define NOTE_USECONDS   0x00000002              /* data is microseconds    */
  #define NOTE_NSECONDS   0x00000004              /* data is nanoseconds     */
  #define NOTE_ABSOLUTE   0x00000008              /* absolute timeout        */
  /* ... implicit EV_ONESHOT, timeout uses the gettimeofday epoch */
  #define NOTE_LEEWAY             0x00000010              /* ext[1] holds leeway for power aware timers */
  #define NOTE_CRITICAL   0x00000020              /* system does minimal timer coalescing */
  #define NOTE_BACKGROUND 0x00000040              /* system does maximum timer coalescing */
  #define NOTE_MACH_CONTINUOUS_TIME       0x00000080
  /*
   * NOTE_MACH_CONTINUOUS_TIME:
   * with NOTE_ABSOLUTE: causes the timer to continue to tick across sleep,
   *      still uses gettimeofday epoch
   * with NOTE_MACHTIME and NOTE_ABSOLUTE: uses mach continuous time epoch
   * without NOTE_ABSOLUTE (interval timer mode): continues to tick across sleep
   */
  #define NOTE_MACHTIME   0x00000100              /* data is mach absolute time units */
  /* timeout uses the mach absolute time epoch */
  
  #ifdef PRIVATE
  /*
   * data/hint fflags for EVFILT_SOCK, shared with userspace.
   *
   */
  #define NOTE_CONNRESET          0x00000001 /* Received RST */
  #define NOTE_READCLOSED         0x00000002 /* Read side is shutdown */
  #define NOTE_WRITECLOSED        0x00000004 /* Write side is shutdown */
  #define NOTE_TIMEOUT            0x00000008 /* timeout: rexmt, keep-alive or persist */
  #define NOTE_NOSRCADDR          0x00000010 /* source address not available */
  #define NOTE_IFDENIED           0x00000020 /* interface denied connection */
  #define NOTE_SUSPEND            0x00000040 /* output queue suspended */
  #define NOTE_RESUME             0x00000080 /* output queue resumed */
  #define NOTE_KEEPALIVE          0x00000100 /* TCP Keepalive received */
  #define NOTE_ADAPTIVE_WTIMO     0x00000200 /* TCP adaptive write timeout */
  #define NOTE_ADAPTIVE_RTIMO     0x00000400 /* TCP adaptive read timeout */
  #define NOTE_CONNECTED          0x00000800 /* socket is connected */
  #define NOTE_DISCONNECTED       0x00001000 /* socket is disconnected */
  #define NOTE_CONNINFO_UPDATED   0x00002000 /* connection info was updated */
  #define NOTE_NOTIFY_ACK         0x00004000 /* notify acknowledgement */
  
  #define EVFILT_SOCK_LEVEL_TRIGGER_MASK \
  	        (NOTE_READCLOSED | NOTE_WRITECLOSED | NOTE_SUSPEND | NOTE_RESUME | \
  	         NOTE_CONNECTED | NOTE_DISCONNECTED)
  
  #define EVFILT_SOCK_ALL_MASK \
  	        (NOTE_CONNRESET | NOTE_READCLOSED | NOTE_WRITECLOSED | NOTE_TIMEOUT | \
  	        NOTE_NOSRCADDR | NOTE_IFDENIED | NOTE_SUSPEND | NOTE_RESUME | \
  	        NOTE_KEEPALIVE | NOTE_ADAPTIVE_WTIMO | NOTE_ADAPTIVE_RTIMO | \
  	        NOTE_CONNECTED | NOTE_DISCONNECTED | NOTE_CONNINFO_UPDATED | \
  	        NOTE_NOTIFY_ACK)
  
  #endif /* PRIVATE */
  
  /*
   * data/hint fflags for EVFILT_MACHPORT, shared with userspace.
   *
   * Only portsets are supported at this time.
   *
   * The fflags field can optionally contain the MACH_RCV_MSG, MACH_RCV_LARGE,
   * and related trailer receive options as defined in <mach/message.h>.
   * The presence of these flags directs the kevent64() call to attempt to receive
   * the message during kevent delivery, rather than just indicate that a message exists.
   * On setup, The ext[0] field contains the receive buffer pointer and ext[1] contains
   * the receive buffer length.  Upon event delivery, the actual received message size
   * is returned in ext[1].  As with mach_msg(), the buffer must be large enough to
   * receive the message and the requested (or default) message trailers.  In addition,
   * the fflags field contains the return code normally returned by mach_msg().
   *
   * If MACH_RCV_MSG is specified, and the ext[1] field specifies a zero length, the
   * system call argument specifying an ouput area (kevent_qos) will be consulted. If
   * the system call specified an output data area, the user-space address
   * of the received message is carved from that provided output data area (if enough
   * space remains there). The address and length of each received message is
   * returned in the ext[0] and ext[1] fields (respectively) of the corresponding kevent.
   *
   * IF_MACH_RCV_VOUCHER_CONTENT is specified, the contents of the message voucher is
   * extracted (as specified in the xflags field) and stored in ext[2] up to ext[3]
   * length.  If the input length is zero, and the system call provided a data area,
   * the space for the voucher content is carved from the provided space and its
   * address and length is returned in ext[2] and ext[3] respectively.
   *
   * If no message receipt options were provided in the fflags field on setup, no
   * message is received by this call. Instead, on output, the data field simply
   * contains the name of the actual port detected with a message waiting.
   */
  
  /*
   * DEPRECATED!!!!!!!!!
   * NOTE_TRACK, NOTE_TRACKERR, and NOTE_CHILD are no longer supported as of 10.5
   */
  /* additional flags for EVFILT_PROC */
  #define NOTE_TRACK      0x00000001              /* follow across forks */
  #define NOTE_TRACKERR   0x00000002              /* could not track child */
  #define NOTE_CHILD      0x00000004              /* am a child process */
  
  
  #ifdef PRIVATE
  #endif /* PRIVATE */
  
  #ifndef KERNEL
  /* Temporay solution for BootX to use inode.h till kqueue moves to vfs layer */
  #include <sys/queue.h>
  struct knote;
  SLIST_HEAD(klist, knote);
  #endif
  
  #ifdef KERNEL
  
  #ifdef XNU_KERNEL_PRIVATE
  #include <sys/queue.h>
  #include <mach/vm_param.h>
  #include <kern/kern_types.h>
  #include <sys/fcntl.h> /* FREAD, FWRITE */
  #include <kern/debug.h> /* panic */
  #include <pthread/priority_private.h>
  
  #ifdef MALLOC_DECLARE
  MALLOC_DECLARE(M_KQUEUE);
  #endif
  
  LIST_HEAD(knote_list, knote);
  TAILQ_HEAD(kqtailq, knote);     /* a list of "queued" events */
  
  /* index into various kq queues */
  typedef uint8_t kq_index_t;
  
  /* lskq(1) knows about this type */
  __options_decl(kn_status_t, uint16_t /* 12 bits really */, {
  	KN_ACTIVE         = 0x001,  /* event has been triggered */
  	KN_QUEUED         = 0x002,  /* event is on queue */
  	KN_DISABLED       = 0x004,  /* event is disabled */
  	KN_DROPPING       = 0x008,  /* knote is being dropped */
  	KN_LOCKED         = 0x010,  /* knote is locked (kq_knlocks) */
  	KN_POSTING        = 0x020,  /* f_event() in flight */
  	KN_STAYACTIVE     = 0x040,  /* force event to stay active */
  	KN_DEFERDELETE    = 0x080,  /* defer delete until re-enabled */
  	KN_MERGE_QOS      = 0x100,  /* f_event() / f_* ran concurrently and overrides must merge */
  	KN_REQVANISH      = 0x200,  /* requested EV_VANISH */
  	KN_VANISHED       = 0x400,  /* has vanished */
  	KN_SUPPRESSED     = 0x800,  /* event is suppressed during delivery */
  });
  
  #if __LP64__
  #define KNOTE_KQ_PACKED_BITS   42
  #define KNOTE_KQ_PACKED_SHIFT   0
  #define KNOTE_KQ_PACKED_BASE    0
  #else
  #define KNOTE_KQ_PACKED_BITS   32
  #define KNOTE_KQ_PACKED_SHIFT   0
  #define KNOTE_KQ_PACKED_BASE    0
  #endif
  
  _Static_assert(!VM_PACKING_IS_BASE_RELATIVE(KNOTE_KQ_PACKED),
      "Make sure the knote pointer packing is based on arithmetic shifts");
  
  struct kqueue;
  struct knote {
  	TAILQ_ENTRY(knote)       kn_tqe;            /* linkage for tail queue */
  	SLIST_ENTRY(knote)       kn_link;           /* linkage for search list */
  	SLIST_ENTRY(knote)       kn_selnext;        /* klist element chain */
  
  	kn_status_t              kn_status : 12;
  	uintptr_t
  	    kn_qos_index:4,                         /* in-use qos index */
  	    kn_qos_override:3,                      /* qos override index */
  	    kn_is_fd:1,                             /* knote is an fd */
  	    kn_vnode_kqok:1,
  	    kn_vnode_use_ofst:1;
  #if __LP64__
  	uintptr_t                   kn_kq_packed : KNOTE_KQ_PACKED_BITS;
  #else
  	uintptr_t                   kn_kq_packed;
  #endif
  
  	/* per filter stash of data (pointer, uint32_t or uint64_t) */
  	union {
  		void               *kn_hook;
  		uint32_t            kn_hook32;
  #if __LP64__
  		uint64_t            kn_hook_waitqid;
  #else
  		uint32_t            kn_hook_waitqid;
  #endif
  	};
  
  	/* per filter pointer to the resource being watched */
  	union {
  		struct fileproc    *kn_fp;          /* file data pointer */
  		struct proc        *kn_proc;        /* proc pointer */
  		struct ipc_mqueue  *kn_mqueue;      /* pset pointer */
  		struct thread_call *kn_thcall;
  		struct thread      *kn_thread;
  	};
  
  	/*
  	 * Mimic kevent_qos so that knote_fill_kevent code is not horrid,
  	 * but with subtleties:
  	 *
  	 * - kevent_qos_s::filter is 16bits where ours is 8, and we use the top
  	 *   bits to store the real specialized filter.
  	 *   knote_fill_kevent* will always force the top bits to 0xff.
  	 *
  	 * - kevent_qos_s::xflags is not kept, kn_sfflags takes its place,
  	 *   knote_fill_kevent* will set xflags to 0.
  	 *
  	 * - kevent_qos_s::data is saved as kn_sdata and filters are encouraged
  	 *   to use knote_fill_kevent, knote_fill_kevent_with_sdata will copy
  	 *   kn_sdata as the output value.
  	 *
  	 * knote_fill_kevent_with_sdata() programatically asserts
  	 * these aliasings are respected.
  	 */
  	struct kevent_internal_s {
  		uint64_t    kei_ident;      /* identifier for this event */
  #ifdef __LITTLE_ENDIAN__
  		int8_t      kei_filter;     /* filter for event */
  		uint8_t     kei_filtid;     /* actual filter for event */
  #else
  		uint8_t     kei_filtid;     /* actual filter for event */
  		int8_t      kei_filter;     /* filter for event */
  #endif
  		uint16_t    kei_flags;      /* general flags */
  		int32_t     kei_qos;        /* quality of service */
  		uint64_t    kei_udata;      /* opaque user data identifier */
  		uint32_t    kei_fflags;     /* filter-specific flags */
  		uint32_t    kei_sfflags;    /* knote: saved fflags */
  		int64_t     kei_sdata;      /* knote: filter-specific saved data */
  		uint64_t    kei_ext[4];     /* filter-specific extensions */
  	} kn_kevent;
  
  #define kn_id           kn_kevent.kei_ident
  #define kn_filtid       kn_kevent.kei_filtid
  #define kn_filter       kn_kevent.kei_filter
  #define kn_flags        kn_kevent.kei_flags
  #define kn_qos          kn_kevent.kei_qos
  #define kn_udata        kn_kevent.kei_udata
  #define kn_fflags       kn_kevent.kei_fflags
  #define kn_sfflags      kn_kevent.kei_sfflags
  #define kn_sdata        kn_kevent.kei_sdata
  #define kn_ext          kn_kevent.kei_ext
  };
  
  static inline struct kqueue *
  knote_get_kq(struct knote *kn)
  {
  	return (struct kqueue *)VM_UNPACK_POINTER(kn->kn_kq_packed, KNOTE_KQ_PACKED);
  }
  
  static inline int
  knote_get_seltype(struct knote *kn)
  {
  	switch (kn->kn_filter) {
  	case EVFILT_READ:
  		return FREAD;
  	case EVFILT_WRITE:
  		return FWRITE;
  	default:
  		panic("%s(%p): invalid filter %d\n",
  		    __func__, kn, kn->kn_filter);
  		return 0;
  	}
  }
  
  struct kevent_ctx_s {
  	uint64_t         kec_data_avail;    /* address of remaining data size */
  	user_addr_t      kec_data_out;      /* extra data pointer */
  	user_size_t      kec_data_size;     /* total extra data size */
  	user_size_t      kec_data_resid;    /* residual extra data size */
  	uint64_t         kec_deadline;      /* wait deadline unless KEVENT_FLAG_IMMEDIATE */
  	struct fileproc *kec_fp;            /* fileproc to pass to fp_drop or NULL */
  	int              kec_fd;            /* fd to pass to fp_drop or -1 */
  
  	/* the fields below are only set during process / scan */
  	int              kec_process_nevents;       /* user-level event count */
  	int              kec_process_noutputs;      /* number of events output */
  	unsigned int     kec_process_flags;         /* kevent flags, only set for process  */
  	user_addr_t      kec_process_eventlist;     /* user-level event list address */
  };
  typedef struct kevent_ctx_s *kevent_ctx_t;
  
  kevent_ctx_t
  kevent_get_context(thread_t thread);
  
  /*
   * Filter operators
   *
   * These routines, provided by each filter, are called to attach, detach, deliver events,
   * change/update filter registration and process/deliver events:
   *
   * - the f_attach, f_touch, f_process, f_peek and f_detach callbacks are always
   *   serialized with respect to each other for the same knote.
   *
   * - the f_event routine is called with a use-count taken on the knote to
   *   prolongate its lifetime and protect against drop, but is not otherwise
   *   serialized with other routine calls.
   *
   * - the f_detach routine is always called last, and is serialized with all
   *   other callbacks, including f_event calls.
   *
   *
   * Here are more details:
   *
   * f_isfd -
   *        identifies if the "ident" field in the kevent structure is a file-descriptor.
   *
   *        If so, the knote is associated with the file descriptor prior to attach and
   *        auto-removed when the file descriptor is closed (this latter behavior may change
   *        for EV_DISPATCH2 kevent types to allow delivery of events identifying unintended
   *        closes).
   *
   *        Otherwise the knote is hashed by the ident and has no auto-close behavior.
   *
   * f_adjusts_qos -
   *        identifies if the filter can adjust its QoS during its lifetime.
   *
   *        Filters using this facility should request the new overrides they want
   *        using the appropriate FILTER_{RESET,ADJUST}_EVENT_QOS extended codes.
   *
   *        Currently, EVFILT_MACHPORT is the only filter using this facility.
   *
   * f_extended_codes -
   *        identifies if the filter returns extended codes from its routines
   *        (see FILTER_ACTIVE, ...) or 0 / 1 values.
   *
   * f_attach -
   *        called to attach the knote to the underlying object that will be delivering events
   *        through it when EV_ADD is supplied and no existing matching event is found
   *
   *        provided a knote that is pre-attached to the fd or hashed (see above) but is
   *        specially marked to avoid concurrent access until the attach is complete. The
   *        kevent structure embedded in this knote has been filled in with a sanitized
   *        version of the user-supplied kevent data.  However, the user-supplied filter-specific
   *        flags (fflags) and data fields have been moved into the knote's kn_sfflags and kn_sdata
   *        fields respectively.  These are usually interpretted as a set of "interest" flags and
   *        data by each filter - to be matched against delivered events.
   *
   *        The attach operator indicated errors by setting the EV_ERROR flog in the flags field
   *        embedded in the knote's kevent structure - with the specific error indicated in the
   *        corresponding data field.
   *
   *        The return value indicates if the knote should already be considered "activated" at
   *        the time of attach (one or more of the interest events has already occured).
   *
   * f_detach -
   *        called to disassociate the knote from the underlying object delivering events
   *        the filter should not attempt to deliver events through this knote after this
   *        operation returns control to the kq system.
   *
   * f_event -
   *        if the knote() function (or KNOTE() macro) is called against a list of knotes,
   *        this operator will be called on each knote in the list.
   *
   *        The "hint" parameter is completely filter-specific, but usually indicates an
   *        event or set of events that have occured against the source object associated
   *        with the list.
   *
   *        The return value indicates if the knote should already be considered "activated" at
   *        the time of attach (one or more of the interest events has already occured).
   *
   * f_process -
   *        called when attempting to deliver triggered events to user-space.
   *
   *        If the knote was previously activated, this operator will be called when a
   *        thread is trying to deliver events to user-space.  The filter gets one last
   *        chance to determine if the event/events are still interesting for this knote
   *        (are the conditions still right to deliver an event).  If so, the filter
   *        fills in the output kevent structure with the information to be delivered.
   *
   *        The input context/data parameter is used during event delivery.  Some
   *        filters allow additional data delivery as part of event delivery.  This
   *        context field indicates if space was made available for these additional
   *        items and how that space is to be allocated/carved-out.
   *
   *        The filter may set EV_CLEAR or EV_ONESHOT in the output flags field to indicate
   *        special post-delivery dispositions for the knote.
   *
   *        EV_CLEAR - indicates that all matching events have been delivered. Even
   *                   though there were events to deliver now, there will not be any
   *                   more until some additional events are delivered to the knote
   *                   via the f_event operator, or the interest set is changed via
   *                   the f_touch operator.  The knote can remain deactivated after
   *                   processing this event delivery.
   *
   *        EV_ONESHOT - indicates that this is the last event to be delivered via
   *                   this knote.  It will automatically be deleted upon delivery
   *                   (or if in dispatch-mode, upon re-enablement after this delivery).
   *
   *        The return value indicates if the knote has delivered an output event.
   *        Unless one of the special output flags was set in the output kevent, a non-
   *        zero return value ALSO indicates that the knote should be re-activated
   *        for future event processing (in case it delivers level-based or a multi-edge
   *        type events like message queues that already exist).
   *
   *        NOTE: In the future, the boolean may change to an enum that allows more
   *              explicit indication of just delivering a current event vs delivering
   *              an event with more events still pending.
   *
   * f_touch -
   *        called to update the knote with new state from the user during
   *        EVFILT_ADD/ENABLE/DISABLE on an already-attached knote.
   *
   *        f_touch should copy relevant new data from the kevent into the knote.
   *
   *        operator must lock against concurrent f_event operations.
   *
   *        A return value of 1 indicates that the knote should now be considered
   *        'activated'.
   *
   *        f_touch can set EV_ERROR with specific error in the data field to
   *        return an error to the client. You should return 1 to indicate that
   *        the kevent needs to be activated and processed.
   *
   * f_peek -
   *        For knotes marked KN_STAYACTIVE, indicate if the knote is truly active
   *        at the moment (not used for event delivery, but for status checks).
   *
   * f_allow_drop -
   *
   *        [OPTIONAL] If this function is non-null, then it indicates that the
   *        filter wants to validate EV_DELETE events. This is necessary if
   *        a particular filter needs to synchronize knote deletion with its own
   *        filter lock.
   *
   *        When true is returned, the the EV_DELETE is allowed and can proceed.
   *
   *        If false is returned, the EV_DELETE doesn't proceed, and the passed in
   *        kevent is used for the copyout to userspace.
   *
   *        Currently, EVFILT_WORKLOOP is the only filter using this facility.
   *
   * f_post_register_wait -
   *        [OPTIONAL] called when attach or touch return the FILTER_REGISTER_WAIT
   *        extended code bit. It is possible to use this facility when the last
   *        register command wants to wait.
   *
   *        Currently, EVFILT_WORKLOOP is the only filter using this facility.
   */
  
  struct _kevent_register;
  struct knote_lock_ctx;
  struct proc;
  struct uthread;
  struct waitq;
  
  struct filterops {
  	bool    f_isfd;               /* true if ident == filedescriptor */
  	bool    f_adjusts_qos;    /* true if the filter can override the knote */
  	bool    f_extended_codes; /* hooks return extended codes */
  
  	int     (*f_attach)(struct knote *kn, struct kevent_qos_s *kev);
  	void    (*f_detach)(struct knote *kn);
  	int     (*f_event)(struct knote *kn, long hint);
  	int     (*f_touch)(struct knote *kn, struct kevent_qos_s *kev);
  	int     (*f_process)(struct knote *kn, struct kevent_qos_s *kev);
  	int     (*f_peek)(struct knote *kn);
  
  	/* optional & advanced */
  	bool    (*f_allow_drop)(struct knote *kn, struct kevent_qos_s *kev);
  	void    (*f_post_register_wait)(struct uthread *uth, struct knote *kn,
  	    struct _kevent_register *ss_kr);
  };
  
  /*
   * Extended codes returned by filter routines when f_extended_codes is set.
   *
   * FILTER_ACTIVE
   *     The filter is active and a call to f_process() may return an event.
   *
   *     For f_process() the meaning is slightly different: the knote will be
   *     activated again as long as f_process returns FILTER_ACTIVE, unless
   *     EV_CLEAR is set, which require a new f_event to reactivate the knote.
   *
   *     Valid:    f_attach, f_event, f_touch, f_process, f_peek
   *     Implicit: -
   *     Ignored:  -
   *
   * FILTER_REGISTER_WAIT
   *     The filter wants its f_post_register_wait() to be called.
   *
   *     Note: It is only valid to ask for this behavior for a workloop kqueue,
   *     and is really only meant to be used by EVFILT_WORKLOOP.
   *
   *     Valid:    f_attach, f_touch
   *     Implicit: -
   *     Ignored:  f_event, f_process, f_peek
   *
   * FILTER_UPDATE_REQ_QOS
   *     The filter wants the passed in QoS to be updated as the new intrinsic qos
   *     for this knote. If the kevent `qos` field is 0, no update is performed.
   *
   *     This also will reset the event QoS, so FILTER_ADJUST_EVENT_QOS() must
   *     also be used if an override should be maintained.
   *
   *     Valid:    f_touch
   *     Implicit: f_attach
   *     Ignored:  f_event, f_process, f_peek
   *
   * FILTER_RESET_EVENT_QOS
   * FILTER_ADJUST_EVENT_QOS(qos)
   *     The filter wants the QoS of the next event delivery to be overridden
   *     at the specified QoS.  This allows for the next event QoS to be elevated
   *     from the knote requested qos (See FILTER_UPDATE_REQ_QOS).
   *
   *     Event QoS Overrides are reset when a particular knote is no longer
   *     active. Hence this is ignored if FILTER_ACTIVE isn't also returned.
   *
   *     Races between an f_event() and any other f_* routine asking for
   *     a specific QoS override are handled generically and the filters do not
   *     have to worry about them.
   *
   *     To use this facility, filters MUST set their f_adjusts_qos bit to true.
   *
   *     It is expected that filters will return the new QoS they expect to be
   *     applied from any f_* callback except for f_process() where no specific
   *     information should be provided. Filters should not try to hide no-ops,
   *     kevent will already optimize these away.
   *
   *     Valid:    f_touch, f_attach, f_event, f_process
   *     Implicit: -
   *     Ignored:  f_peek
   *
   * FILTER_THREADREQ_NODEFEER
   *     The filter has moved a turnstile priority push away from the current
   *     thread, preemption has been disabled, and thread requests need to be
   *     commited before preemption is re-enabled.
   *
   *
   *     Valid:    f_attach, f_touch
   *     Implicit: -
   *     Invalid:  f_event, f_process, f_peek
   */
  #define FILTER_ACTIVE                       0x00000001
  #define FILTER_REGISTER_WAIT                0x00000002
  #define FILTER_UPDATE_REQ_QOS               0x00000004
  #define FILTER_ADJUST_EVENT_QOS_BIT         0x00000008
  #define FILTER_ADJUST_EVENT_QOS_MASK        0x00000070
  #define FILTER_ADJUST_EVENT_QOS_SHIFT 4
  #define FILTER_ADJUST_EVENT_QOS(qos) \
  	        (((qos) << FILTER_ADJUST_EVENT_QOS_SHIFT) | FILTER_ADJUST_EVENT_QOS_BIT)
  #define FILTER_RESET_EVENT_QOS              FILTER_ADJUST_EVENT_QOS_BIT
  #define FILTER_THREADREQ_NODEFEER           0x00000080
  
  #define filter_call(_ops, call)  \
  	        ((_ops)->f_extended_codes ? (_ops)->call : !!((_ops)->call))
  
  SLIST_HEAD(klist, knote);
  extern void     knote_init(void);
  extern void     klist_init(struct klist *list);
  
  #define KNOTE(list, hint)       knote(list, hint)
  #define KNOTE_ATTACH(list, kn)  knote_attach(list, kn)
  #define KNOTE_DETACH(list, kn)  knote_detach(list, kn)
  
  extern void knote(struct klist *list, long hint);
  extern int knote_attach(struct klist *list, struct knote *kn);
  extern int knote_detach(struct klist *list, struct knote *kn);
  extern void knote_vanish(struct klist *list, bool make_active);
  
  extern void knote_set_error(struct knote *kn, int error);
  extern int64_t knote_low_watermark(const struct knote *kn) __pure2;
  extern void knote_fill_kevent_with_sdata(struct knote *kn, struct kevent_qos_s *kev);
  extern void knote_fill_kevent(struct knote *kn, struct kevent_qos_s *kev, int64_t data);
  
  extern void knote_link_waitqset_lazy_alloc(struct knote *kn);
  extern boolean_t knote_link_waitqset_should_lazy_alloc(struct knote *kn);
  extern int knote_link_waitq(struct knote *kn, struct waitq *wq, uint64_t *reserved_link);
  extern int knote_unlink_waitq(struct knote *kn, struct waitq *wq);
  extern void knote_fdclose(struct proc *p, int fd);
  extern void knote_markstayactive(struct knote *kn);
  extern void knote_clearstayactive(struct knote *kn);
  extern const struct filterops *knote_fops(struct knote *kn);
  
  extern struct turnstile *kqueue_turnstile(struct kqueue *);
  extern struct turnstile *kqueue_alloc_turnstile(struct kqueue *);
  
  int kevent_proc_copy_uptrs(void *proc, uint64_t *buf, uint32_t bufsize);
  int kevent_copyout_proc_dynkqids(void *proc, user_addr_t ubuf,
      uint32_t ubufsize, int32_t *nkqueues_out);
  int kevent_copyout_dynkqinfo(void *proc, kqueue_id_t kq_id, user_addr_t ubuf,
      uint32_t ubufsize, int32_t *size_out);
  int kevent_copyout_dynkqextinfo(void *proc, kqueue_id_t kq_id, user_addr_t ubuf,
      uint32_t ubufsize, int32_t *nknotes_out);
  
  extern int filt_wlattach_sync_ipc(struct knote *kn);
  extern void filt_wldetach_sync_ipc(struct knote *kn);
  
  extern int kevent_workq_internal(struct proc *p,
      user_addr_t changelist, int nchanges,
      user_addr_t eventlist, int nevents,
      user_addr_t data_out, user_size_t *data_available,
      unsigned int flags, int32_t *retval);
  
  #elif defined(KERNEL_PRIVATE) /* !XNU_KERNEL_PRIVATE: kexts still need a klist structure definition */
  
  #include <sys/queue.h>
  struct proc;
  struct knote;
  SLIST_HEAD(klist, knote);
  
  #endif /* !XNU_KERNEL_PRIVATE && KERNEL_PRIVATE */
  
  #else   /* KERNEL */
  
  #include <sys/types.h>
  
  struct timespec;
  
  __BEGIN_DECLS
  int     kqueue(void);
  int     kevent(int kq,
      const struct kevent *changelist, int nchanges,
      struct kevent *eventlist, int nevents,
      const struct timespec *timeout);
  int     kevent64(int kq,
      const struct kevent64_s *changelist, int nchanges,
      struct kevent64_s *eventlist, int nevents,
      unsigned int flags,
      const struct timespec *timeout);
  
  #ifdef PRIVATE
  int     kevent_qos(int kq,
      const struct kevent_qos_s *changelist, int nchanges,
      struct kevent_qos_s *eventlist, int nevents,
      void *data_out, size_t *data_available,
      unsigned int flags);
  
  int     kevent_id(kqueue_id_t id,
      const struct kevent_qos_s *changelist, int nchanges,
      struct kevent_qos_s *eventlist, int nevents,
      void *data_out, size_t *data_available,
      unsigned int flags);
  #endif /* PRIVATE */
  
  __END_DECLS
  
  
  #endif /* KERNEL */
  
  #ifdef PRIVATE
  
  /* Flags for pending events notified by kernel via return-to-kernel ast */
  #define R2K_WORKLOOP_PENDING_EVENTS             0x1
  #define R2K_WORKQ_PENDING_EVENTS                0x2
  
  #endif /* PRIVATE */
  
  #endif /* !_SYS_EVENT_H_ */
  