Super User's BSD Cross Reference: /FreeBSD/usr.sbin/bhyve/mevent.c

 /*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 2011 NetApp, Inc.
 * 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 NETAPP, INC ``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 NETAPP, INC 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.
 *
 * $FreeBSD$
 */

 /*
 * Micro event library for FreeBSD, designed for a single i/o thread
 * using kqueue, and having events be persistent by default.
 */

#include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");

#include <assert.h>
#ifndef WITHOUT_CAPSICUM
#include <capsicum_helpers.h>
#endif
#include <err.h>
#include <errno.h>
#include <stdbool.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sysexits.h>
#include <unistd.h>

#include <sys/types.h>
#ifndef WITHOUT_CAPSICUM
#include <sys/capsicum.h>
#endif
#include <sys/event.h>
#include <sys/time.h>

#include <pthread.h>
#include <pthread_np.h>

#include "mevent.h"

#define MEVENT_MAX 64

 extern const char *vmname;

 static pthread_t mevent_tid;
 static int mevent_timid = 43;
 static int mevent_pipefd[2];
 static pthread_mutex_t mevent_lmutex = PTHREAD_MUTEX_INITIALIZER;

 struct mevent {
 void (*me_func)(int, enum ev_type, void *);
#define me_msecs me_fd
 int me_fd;
 int me_timid;
 enum ev_type me_type;
 void *me_param;
 int me_cq;
 int me_state; /* Desired kevent flags. */
 int me_closefd;
 LIST_ENTRY(mevent) me_list;
};

 static LIST_HEAD(listhead, mevent) global_head, change_head;

 static void
 mevent_qlock(void)
{
 pthread_mutex_lock(&mevent_lmutex);
}

 static void
 mevent_qunlock(void)
{
 pthread_mutex_unlock(&mevent_lmutex);
}

 static void
 mevent_pipe_read(int fd, enum ev_type type, void *param)
{
 char buf[MEVENT_MAX];
 int status;

 /*
 * Drain the pipe read side. The fd is non-blocking so this is
 * safe to do.
 */
 do {
 status = read(fd, buf, sizeof(buf));
 } while (status == MEVENT_MAX);
}

 static void
 mevent_notify(void)
{
 char c = '0円';

 /*
 * If calling from outside the i/o thread, write a byte on the
 * pipe to force the i/o thread to exit the blocking kevent call.
 */
 if (mevent_pipefd[1] != 0 && pthread_self() != mevent_tid) {
 write(mevent_pipefd[1], &c, 1);
 }
}

 static int
 mevent_kq_filter(struct mevent *mevp)
{
 int retval;

 retval = 0;

 if (mevp->me_type == EVF_READ)
 retval = EVFILT_READ;

 if (mevp->me_type == EVF_WRITE)
 retval = EVFILT_WRITE;

 if (mevp->me_type == EVF_TIMER)
 retval = EVFILT_TIMER;

 if (mevp->me_type == EVF_SIGNAL)
 retval = EVFILT_SIGNAL;

 return (retval);
}

 static int
 mevent_kq_flags(struct mevent *mevp)
{
 return (mevp->me_state);
}

 static int
 mevent_kq_fflags(struct mevent *mevp)
{
 /* XXX nothing yet, perhaps EV_EOF for reads ? */
 return (0);
}

 static int
 mevent_build(int mfd, struct kevent *kev)
{
 struct mevent *mevp, *tmpp;
 int i;

 i = 0;

 mevent_qlock();

 LIST_FOREACH_SAFE(mevp, &change_head, me_list, tmpp) {
 if (mevp->me_closefd) {
 /*
 * A close of the file descriptor will remove the
 * event
 */
 close(mevp->me_fd);
 } else {
 if (mevp->me_type == EVF_TIMER) {
 kev[i].ident = mevp->me_timid;
 kev[i].data = mevp->me_msecs;
 } else {
 kev[i].ident = mevp->me_fd;
 kev[i].data = 0;
 }
 kev[i].filter = mevent_kq_filter(mevp);
 kev[i].flags = mevent_kq_flags(mevp);
 kev[i].fflags = mevent_kq_fflags(mevp);
 kev[i].udata = mevp;
 i++;
 }

 mevp->me_cq = 0;
 LIST_REMOVE(mevp, me_list);

 if (mevp->me_state & EV_DELETE) {
 free(mevp);
 } else {
 /*
 * We need to add the event only once, so we can
 * reset the EV_ADD bit after it has been propagated
 * to the kevent() arguments the first time.
 */
 mevp->me_state &= ~EV_ADD;
 LIST_INSERT_HEAD(&global_head, mevp, me_list);
 }

 assert(i < MEVENT_MAX);
 }

 mevent_qunlock();

 return (i);
}

 static void
 mevent_handle(struct kevent *kev, int numev)
{
 struct mevent *mevp;
 int i;

 for (i = 0; i < numev; i++) {
 mevp = kev[i].udata;

 /* XXX check for EV_ERROR ? */

 (*mevp->me_func)(mevp->me_fd, mevp->me_type, mevp->me_param);
 }
}

 static struct mevent *
 mevent_add_state(int tfd, enum ev_type type,
 void (*func)(int, enum ev_type, void *), void *param,
 int state)
{
 struct mevent *lp, *mevp;

 if (tfd < 0 || func == NULL) {
 return (NULL);
 }

 mevp = NULL;

 mevent_qlock();

 /*
 * Verify that the fd/type tuple is not present in any list
 */
 LIST_FOREACH(lp, &global_head, me_list) {
 if (type != EVF_TIMER && lp->me_fd == tfd &&
 lp->me_type == type) {
 goto exit;
 }
 }

 LIST_FOREACH(lp, &change_head, me_list) {
 if (type != EVF_TIMER && lp->me_fd == tfd &&
 lp->me_type == type) {
 goto exit;
 }
 }

 /*
 * Allocate an entry, populate it, and add it to the change list.
 */
 mevp = calloc(1, sizeof(struct mevent));
 if (mevp == NULL) {
 goto exit;
 }

 if (type == EVF_TIMER) {
 mevp->me_msecs = tfd;
 mevp->me_timid = mevent_timid++;
 } else
 mevp->me_fd = tfd;
 mevp->me_type = type;
 mevp->me_func = func;
 mevp->me_param = param;

 LIST_INSERT_HEAD(&change_head, mevp, me_list);
 mevp->me_cq = 1;
 mevp->me_state = state;
 mevent_notify();

 exit:
 mevent_qunlock();

 return (mevp);
}

 struct mevent *
 mevent_add(int tfd, enum ev_type type,
 void (*func)(int, enum ev_type, void *), void *param)
{

 return (mevent_add_state(tfd, type, func, param, EV_ADD));
}

 struct mevent *
 mevent_add_disabled(int tfd, enum ev_type type,
 void (*func)(int, enum ev_type, void *), void *param)
{

 return (mevent_add_state(tfd, type, func, param, EV_ADD | EV_DISABLE));
}

 static int
 mevent_update(struct mevent *evp, bool enable)
{
 int newstate;

 mevent_qlock();

 /*
 * It's not possible to enable/disable a deleted event
 */
 assert((evp->me_state & EV_DELETE) == 0);

 newstate = evp->me_state;
 if (enable) {
 newstate |= EV_ENABLE;
 newstate &= ~EV_DISABLE;
 } else {
 newstate |= EV_DISABLE;
 newstate &= ~EV_ENABLE;
 }

 /*
 * No update needed if state isn't changing
 */
 if (evp->me_state != newstate) {
 evp->me_state = newstate;

 /*
 * Place the entry onto the changed list if not
 * already there.
 */
 if (evp->me_cq == 0) {
 evp->me_cq = 1;
 LIST_REMOVE(evp, me_list);
 LIST_INSERT_HEAD(&change_head, evp, me_list);
 mevent_notify();
 }
 }

 mevent_qunlock();

 return (0);
}

 int
 mevent_enable(struct mevent *evp)
{

 return (mevent_update(evp, true));
}

 int
 mevent_disable(struct mevent *evp)
{

 return (mevent_update(evp, false));
}

 static int
 mevent_delete_event(struct mevent *evp, int closefd)
{
 mevent_qlock();

 /*
 * Place the entry onto the changed list if not already there, and
 * mark as to be deleted.
 */
 if (evp->me_cq == 0) {
 evp->me_cq = 1;
 LIST_REMOVE(evp, me_list);
 LIST_INSERT_HEAD(&change_head, evp, me_list);
 mevent_notify();
 }
 evp->me_state = EV_DELETE;

 if (closefd)
 evp->me_closefd = 1;

 mevent_qunlock();

 return (0);
}

 int
 mevent_delete(struct mevent *evp)
{

 return (mevent_delete_event(evp, 0));
}

 int
 mevent_delete_close(struct mevent *evp)
{

 return (mevent_delete_event(evp, 1));
}

 static void
 mevent_set_name(void)
{

 pthread_set_name_np(mevent_tid, "mevent");
}

 void
 mevent_dispatch(void)
{
 struct kevent changelist[MEVENT_MAX];
 struct kevent eventlist[MEVENT_MAX];
 struct mevent *pipev;
 int mfd;
 int numev;
 int ret;
#ifndef WITHOUT_CAPSICUM
 cap_rights_t rights;
#endif

 mevent_tid = pthread_self();
 mevent_set_name();

 mfd = kqueue();
 assert(mfd > 0);

#ifndef WITHOUT_CAPSICUM
 cap_rights_init(&rights, CAP_KQUEUE);
 if (caph_rights_limit(mfd, &rights) == -1)
 errx(EX_OSERR, "Unable to apply rights for sandbox");
#endif

 /*
 * Open the pipe that will be used for other threads to force
 * the blocking kqueue call to exit by writing to it. Set the
 * descriptor to non-blocking.
 */
 ret = pipe(mevent_pipefd);
 if (ret < 0) {
 perror("pipe");
 exit(0);
 }

#ifndef WITHOUT_CAPSICUM
 cap_rights_init(&rights, CAP_EVENT, CAP_READ, CAP_WRITE);
 if (caph_rights_limit(mevent_pipefd[0], &rights) == -1)
 errx(EX_OSERR, "Unable to apply rights for sandbox");
 if (caph_rights_limit(mevent_pipefd[1], &rights) == -1)
 errx(EX_OSERR, "Unable to apply rights for sandbox");
#endif

 /*
 * Add internal event handler for the pipe write fd
 */
 pipev = mevent_add(mevent_pipefd[0], EVF_READ, mevent_pipe_read, NULL);
 assert(pipev != NULL);

 for (;;) {
 /*
 * Build changelist if required.
 * XXX the changelist can be put into the blocking call
 * to eliminate the extra syscall. Currently better for
 * debug.
 */
 numev = mevent_build(mfd, changelist);
 if (numev) {
 ret = kevent(mfd, changelist, numev, NULL, 0, NULL);
 if (ret == -1) {
 perror("Error return from kevent change");
 }
 }

 /*
 * Block awaiting events
 */
 ret = kevent(mfd, NULL, 0, eventlist, MEVENT_MAX, NULL);
 if (ret == -1 && errno != EINTR) {
 perror("Error return from kevent monitor");
 }

 /*
 * Handle reported events
 */
 mevent_handle(eventlist, ret);
 }
}
 

Indexes created Fri Nov 14 03:53:34 PST 2025