> Date: Thu, 2 Nov 2017 14:29:30 +0200
> From: Paul Irofti <p...@irofti.net>
>
> Hi,
>
> Here is a backport from FreeBSD to support EVFILT_USER events.
>
> %-------------------------------------------------------------------------------
> EVFILT_USER Establishes a user event identified by ident which is
> not associated with any kernel mechanism but is trig-
> gered by user level code. The lower 24 bits of the
> fflags may be used for user defined flags and manipu-
> lated using the following:
>
> NOTE_FFNOP Ignore the input fflags.
>
> NOTE_FFAND Bitwise AND fflags.
>
> NOTE_FFOR Bitwise OR fflags.
>
> NOTE_FFCOPY Copy fflags.
>
> NOTE_FFCTRLMASK Control mask for fflags.
>
> NOTE_FFLAGSMASK User defined flag mask for
> fflags.
>
> A user event is triggered for output with the follow-
> ing:
>
> NOTE_TRIGGER Cause the event to be triggered.
>
> On return, fflags contains the users defined flags in
> the lower 24 bits.
> %-------------------------------------------------------------------------------
>
> I can split the diff in two if needed: first add the touch
> functionality and then the EVFILT_USER support on top.
>
> Thoughts?
I think you need a very good motivation for introducing such
functionality in OpenBSD.
> Index: sys/event.h
> ===================================================================
> RCS file: /cvs/src/sys/sys/event.h,v
> retrieving revision 1.26
> diff -u -p -u -p -r1.26 event.h
> --- sys/event.h 26 Jun 2017 09:32:32 -0000 1.26
> +++ sys/event.h 2 Nov 2017 11:58:11 -0000
> @@ -38,8 +38,9 @@
> #define EVFILT_PROC (-5) /* attached to struct process */
> #define EVFILT_SIGNAL (-6) /* attached to struct process */
> #define EVFILT_TIMER (-7) /* timers */
> +#define EVFILT_USER (-8) /* User events */
>
> -#define EVFILT_SYSCOUNT 7
> +#define EVFILT_SYSCOUNT 8
>
> #define EV_SET(kevp_, a, b, c, d, e, f) do { \
> struct kevent *kevp = (kevp_); \
> @@ -80,6 +81,25 @@ struct kevent {
> #define EV_ERROR 0x4000 /* error, data contains errno */
>
> /*
> + * data/hint flags/masks for EVFILT_USER, shared with userspace
> + *
> + * 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 /* masks for operations
> */
> +#define NOTE_FFLAGSMASK 0x00ffffff
> +
> +#define NOTE_TRIGGER 0x01000000 /* Cause the event to be
> + triggered for output. */
> +
> +/*
> * hint flag for in-kernel use - must not equal any existing note
> */
> #ifdef _KERNEL
> @@ -142,11 +162,22 @@ SLIST_HEAD(klist, knote);
> */
> #define NOTE_SIGNAL 0x08000000
>
> +/*
> + * Hint values for the optional f_touch event filter. If f_touch is not set
> + * to NULL and f_isfd is zero the f_touch filter will be called with the type
> + * argument set to EVENT_REGISTER during a kevent() system call. It is also
> + * called under the same conditions with the type argument set to
> EVENT_PROCESS
> + * when the event has been triggered.
> + */
> +#define EVENT_REGISTER 1
> +#define EVENT_PROCESS 2
> +
> struct filterops {
> int f_isfd; /* true if ident == filedescriptor */
> int (*f_attach)(struct knote *kn);
> void (*f_detach)(struct knote *kn);
> int (*f_event)(struct knote *kn, long hint);
> + void (*f_touch)(struct knote *kn, struct kevent *kev, long type);
> };
>
> struct knote {
> @@ -164,6 +195,7 @@ struct knote {
> } kn_ptr;
> const struct filterops *kn_fop;
> void *kn_hook;
> + int kn_hookid;
> #define KN_ACTIVE 0x01 /* event has been triggered */
> #define KN_QUEUED 0x02 /* event is on queue */
> #define KN_DISABLED 0x04 /* event is disabled */
> Index: kern/kern_event.c
> ===================================================================
> RCS file: /cvs/src/sys/kern/kern_event.c,v
> retrieving revision 1.81
> diff -u -p -u -p -r1.81 kern_event.c
> --- kern/kern_event.c 11 Oct 2017 08:06:56 -0000 1.81
> +++ kern/kern_event.c 2 Nov 2017 11:58:11 -0000
> @@ -2,6 +2,7 @@
>
> /*-
> * Copyright (c) 1999,2000,2001 Jonathan Lemon <jle...@freebsd.org>
> + * Copyright (c) 2009 Apple, Inc.
> * All rights reserved.
> *
> * Redistribution and use in source and binary forms, with or without
> @@ -98,6 +99,11 @@ int filt_timerattach(struct knote *kn);
> void filt_timerdetach(struct knote *kn);
> int filt_timer(struct knote *kn, long hint);
> void filt_seltruedetach(struct knote *kn);
> +int filt_userattach(struct knote *kn);
> +void filt_userdetach(struct knote *kn);
> +int filt_user(struct knote *kn, long hint);
> +void filt_usertouch(struct knote *kn, struct kevent *kev, long type);
> +
>
> struct filterops kqread_filtops =
> { 1, NULL, filt_kqdetach, filt_kqueue };
> @@ -107,6 +113,9 @@ struct filterops file_filtops =
> { 1, filt_fileattach, NULL, NULL };
> struct filterops timer_filtops =
> { 0, filt_timerattach, filt_timerdetach, filt_timer };
> +struct filterops user_filtops =
> + { 0, filt_userattach, filt_userdetach, filt_user, filt_usertouch };
> +
>
> struct pool knote_pool;
> struct pool kqueue_pool;
> @@ -137,6 +146,7 @@ struct filterops *sysfilt_ops[] = {
> &proc_filtops, /* EVFILT_PROC */
> &sig_filtops, /* EVFILT_SIGNAL */
> &timer_filtops, /* EVFILT_TIMER */
> + &user_filtops, /* EVFILT_USER */
> };
>
> void KQREF(struct kqueue *);
> @@ -383,6 +393,93 @@ filt_timer(struct knote *kn, long hint)
> return (kn->kn_data != 0);
> }
>
> +int
> +filt_userattach(struct knote *kn)
> +{
> +
> + /*
> + * EVFILT_USER knotes are not attached to anything in the kernel.
> + */
> + kn->kn_hook = NULL;
> + if (kn->kn_fflags & NOTE_TRIGGER)
> + kn->kn_hookid = 1;
> + else
> + kn->kn_hookid = 0;
> + return (0);
> +}
> +
> +void
> +filt_userdetach(__unused struct knote *kn)
> +{
> +
> + /*
> + * EVFILT_USER knotes are not attached to anything in the kernel.
> + */
> +}
> +
> +int
> +filt_user(struct knote *kn, __unused long hint)
> +{
> +
> + return (kn->kn_hookid);
> +}
> +
> +void
> +filt_usertouch(struct knote *kn, struct kevent *kev, long type)
> +{
> + int ffctrl;
> +
> + switch (type) {
> + case EVENT_REGISTER:
> + if (kev->fflags & NOTE_TRIGGER)
> + kn->kn_hookid = 1;
> +
> + ffctrl = kev->fflags & NOTE_FFCTRLMASK;
> + kev->fflags &= NOTE_FFLAGSMASK;
> + switch (ffctrl) {
> + case NOTE_FFNOP:
> + break;
> +
> + case NOTE_FFAND:
> + kn->kn_sfflags &= kev->fflags;
> + break;
> +
> + case NOTE_FFOR:
> + kn->kn_sfflags |= kev->fflags;
> + break;
> +
> + case NOTE_FFCOPY:
> + kn->kn_sfflags = kev->fflags;
> + break;
> +
> + default:
> + /* XXX Return error? */
> + break;
> + }
> + kn->kn_sdata = kev->data;
> + if (kev->flags & EV_CLEAR) {
> + kn->kn_hookid = 0;
> + kn->kn_data = 0;
> + kn->kn_fflags = 0;
> + }
> + break;
> +
> + case EVENT_PROCESS:
> + *kev = kn->kn_kevent;
> + kev->fflags = kn->kn_sfflags;
> + kev->data = kn->kn_sdata;
> + if (kn->kn_flags & EV_CLEAR) {
> + kn->kn_hookid = 0;
> + kn->kn_data = 0;
> + kn->kn_fflags = 0;
> + }
> + break;
> +
> + default:
> + panic("filt_usertouch() - invalid type (%ld)", type);
> + break;
> + }
> +}
>
> /*
> * filt_seltrue:
> @@ -556,7 +653,7 @@ kqueue_register(struct kqueue *kq, struc
> struct filterops *fops = NULL;
> struct file *fp = NULL;
> struct knote *kn = NULL;
> - int s, error = 0;
> + int s, error = 0, event;
>
> if (kev->filter < 0) {
> if (kev->filter + EVFILT_SYSCOUNT < 0)
> @@ -603,17 +700,11 @@ kqueue_register(struct kqueue *kq, struc
> }
> }
>
> - if (kn == NULL && ((kev->flags & EV_ADD) == 0)) {
> - error = ENOENT;
> - goto done;
> - }
> -
> /*
> * kn now contains the matching knote, or NULL if no match
> */
> - if (kev->flags & EV_ADD) {
> -
> - if (kn == NULL) {
> + if (kn == NULL) {
> + if (kev->flags & EV_ADD) {
> kn = knote_alloc();
> if (kn == NULL) {
> error = ENOMEM;
> @@ -640,28 +731,46 @@ kqueue_register(struct kqueue *kq, struc
> knote_drop(kn, p, fdp);
> goto done;
> }
> + goto done_ev_add;
> } else {
> - /*
> - * The user may change some filter values after the
> - * initial EV_ADD, but doing so will not reset any
> - * filters which have already been triggered.
> - */
> - kn->kn_sfflags = kev->fflags;
> - kn->kn_sdata = kev->data;
> - kn->kn_kevent.udata = kev->udata;
> + /* No matching knote and the EV_ADD flag is not set. */
> + error = ENOENT;
> + goto done;
> }
> -
> - s = splhigh();
> - if (kn->kn_fop->f_event(kn, 0))
> - KNOTE_ACTIVATE(kn);
> - splx(s);
> -
> - } else if (kev->flags & EV_DELETE) {
> + }
> + if (kev->flags & EV_DELETE) {
> kn->kn_fop->f_detach(kn);
> knote_drop(kn, p, p->p_fd);
> goto done;
> }
>
> + /*
> + * The user may change some filter values after the
> + * initial EV_ADD, but doing so will not reset any
> + * filters which have already been triggered.
> + */
> + kn->kn_kevent.udata = kev->udata;
> + if (!fops->f_isfd && fops->f_touch != NULL) {
> + fops->f_touch(kn, kev, EVENT_REGISTER);
> + } else {
> + kn->kn_sfflags = kev->fflags;
> + kn->kn_sdata = kev->data;
> + }
> +
> + /*
> + * We can get here with kn->kn_knlist == NULL. This can happen when
> + * the initial attach event decides that the event is "completed"
> + * already. i.e. filt_procattach is called on a zombie process. It
> + * will call filt_proc which will remove it from the list, and NULL
> + * kn_knlist.
> + */
> +done_ev_add:
> + event = kn->kn_fop->f_event(kn, 0);
> + s = splhigh();
> + if (event)
> + KNOTE_ACTIVATE(kn);
> + splx(s);
> +
> if ((kev->flags & EV_DISABLE) &&
> ((kn->kn_status & KN_DISABLED) == 0)) {
> s = splhigh();
> @@ -691,7 +800,7 @@ kqueue_scan(struct kqueue *kq, int maxev
> struct kevent *kevp;
> struct timeval atv, rtv, ttv;
> struct knote *kn, marker;
> - int s, count, timeout, nkev = 0, error = 0;
> + int s, count, timeout, nkev = 0, error = 0, touch;
> struct kevent kev[KQ_NEVENTS];
>
> count = maxevents;
> @@ -782,7 +891,12 @@ start:
> kn->kn_status &= ~(KN_QUEUED | KN_ACTIVE);
> continue;
> }
> - *kevp = kn->kn_kevent;
> + touch = (!kn->kn_fop->f_isfd &&
> + kn->kn_fop->f_touch != NULL);
> + if (touch)
> + kn->kn_fop->f_touch(kn, kevp, EVENT_PROCESS);
> + else
> + *kevp = kn->kn_kevent;
> kevp++;
> nkev++;
> if (kn->kn_flags & EV_ONESHOT) {
> @@ -793,8 +907,14 @@ start:
> s = splhigh();
> } else if (kn->kn_flags & (EV_CLEAR | EV_DISPATCH)) {
> if (kn->kn_flags & EV_CLEAR) {
> - kn->kn_data = 0;
> - kn->kn_fflags = 0;
> + /*
> + * Manually clear knotes who weren't
> + * 'touch'ed.
> + */
> + if (touch == 0) {
> + kn->kn_data = 0;
> + kn->kn_fflags = 0;
> + }
> }
> if (kn->kn_flags & EV_DISPATCH)
> kn->kn_status |= KN_DISABLED;
>
>
