lib/libsysevent/libevchannel.c

	libevchannel.c revision f6e214c7418f43af38bd8c3a557e3d0a1d311cfa
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
 */

#include <stdio.h>
#include <ctype.h>
#include <fcntl.h>
#include <errno.h>
#include <door.h>
#include <unistd.h>
#include <stddef.h>
#include <stdlib.h>
#include <strings.h>
#include <pthread.h>
#include <atomic.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/varargs.h>
#include <sys/sysevent.h>
#include <sys/sysevent_impl.h>

#include "libsysevent.h"
#include "libsysevent_impl.h"

/*
 * The functions below deal with the General Purpose Event Handling framework
 *
 * sysevent_evc_bind        - create/bind application to named channel
 * sysevent_evc_unbind      - unbind from previously bound/created channel
 * sysevent_evc_subscribe   - subscribe to existing event channel
 * sysevent_evc_unsubscribe - unsubscribe from existing event channel
 * sysevent_evc_publish     - generate a system event via an event channel
 * sysevent_evc_control     - various channel based control operation
 */

static void kill_door_servers(evchan_subscr_t *);

#define misaligned(p)   ((uintptr_t)(p) & 3)    /* 4-byte alignment required */

static pthread_key_t nrkey = PTHREAD_ONCE_KEY_NP;

/*
 * If the current thread is a door server thread servicing a door created
 * for us in sysevent_evc_xsubscribe, then an attempt to unsubscribe from
 * within door invocation context on the same channel will deadlock in the
 * kernel waiting for our own invocation to complete.  Such calls are
 * forbidden, and we abort if they are encountered (better than hanging
 * unkillably).
 *
 * We'd like to offer this detection to subscriptions established with
 * sysevent_evc_subscribe, but we don't have control over the door service
 * threads in that case.  Perhaps the fix is to always use door_xcreate
 * even for sysevent_evc_subscribe?
 */
static boolean_t
will_deadlock(evchan_t *scp)
{
    evchan_subscr_t *subp = pthread_getspecific(nrkey);
    evchan_impl_hdl_t *hdl = EVCHAN_IMPL_HNDL(scp);

    return (subp != NULL && subp->ev_subhead == hdl ? B_TRUE : B_FALSE);
}

/*
 * Check syntax of a channel name
 */
static int
sysevent_is_chan_name(const char *str)
{
    for (; *str != '\0'; str++) {
        if (!EVCH_ISCHANCHAR(*str))
            return (0);
    }

    return (1);
}

/*
 * Check for printable characters
 */
static int
strisprint(const char *s)
{
    for (; *s != '\0'; s++) {
        if (*s < ' ' || *s > '~')
            return (0);
    }

    return (1);
}

/*
 * sysevent_evc_bind - Create/bind application to named channel
 */
int
sysevent_evc_bind(const char *channel, evchan_t **scpp, uint32_t flags)
{
    int chanlen;
    evchan_t *scp;
    sev_bind_args_t uargs;
    int ec;

    if (scpp == NULL || misaligned(scpp)) {
        return (errno = EINVAL);
    }

    /* Provide useful value in error case */
    *scpp = NULL;

    if (channel == NULL ||
        (chanlen = strlen(channel) + 1) > MAX_CHNAME_LEN) {
        return (errno = EINVAL);
    }

    /* Check channel syntax */
    if (!sysevent_is_chan_name(channel)) {
        return (errno = EINVAL);
    }

    if (flags & ~EVCH_B_FLAGS) {
        return (errno = EINVAL);
    }

    scp = calloc(1, sizeof (evchan_impl_hdl_t));
    if (scp == NULL) {
        return (errno = ENOMEM);
    }

    /*
     * Enable sysevent driver.  Fallback if the device link doesn't exist;
     * this situation can arise if a channel is bound early in system
     * startup, prior to devfsadm(1M) being invoked.
     */
    EV_FD(scp) = open(DEVSYSEVENT, O_RDWR);
    if (EV_FD(scp) == -1) {
        if (errno != ENOENT) {
            ec = errno == EACCES ? EPERM : errno;
            free(scp);
            return (errno = ec);
        }

        EV_FD(scp) = open(DEVICESYSEVENT, O_RDWR);
        if (EV_FD(scp) == -1) {
            ec = errno == EACCES ? EPERM : errno;
            free(scp);
            return (errno = ec);
        }
    }

    /*
     * Force to close the fd's when process is doing exec.
     * The driver will then release stale binding handles.
     * The driver will release also the associated subscriptions
     * if EVCH_SUB_KEEP flag was not set.
     */
    (void) fcntl(EV_FD(scp), F_SETFD, FD_CLOEXEC);

    uargs.chan_name.name = (uintptr_t)channel;
    uargs.chan_name.len = chanlen;
    uargs.flags = flags;

    if (ioctl(EV_FD(scp), SEV_CHAN_OPEN, &uargs) != 0) {
        ec = errno;
        (void) close(EV_FD(scp));
        free(scp);
        return (errno = ec);
    }

    /* Needed to detect a fork() */
    EV_PID(scp) = getpid();
    (void) mutex_init(EV_LOCK(scp), USYNC_THREAD, NULL);

    *scpp = scp;

    return (0);
}

/*
 * sysevent_evc_unbind - Unbind from previously bound/created channel
 */
int
sysevent_evc_unbind(evchan_t *scp)
{
    sev_unsubscribe_args_t uargs;
    evchan_subscr_t *subp;
    int errcp;

    if (scp == NULL || misaligned(scp))
        return (errno = EINVAL);

    if (will_deadlock(scp))
        return (errno = EDEADLK);

    (void) mutex_lock(EV_LOCK(scp));

    /*
     * Unsubscribe, if we are in the process which did the bind.
     */
    if (EV_PID(scp) == getpid()) {
        uargs.sid.name = NULL;
        uargs.sid.len = 0;
        /*
         * The unsubscribe ioctl will block until all door upcalls have
         * drained.
         */
        if (ioctl(EV_FD(scp), SEV_UNSUBSCRIBE, (intptr_t)&uargs) != 0) {
            errcp = errno;
            (void) mutex_unlock(EV_LOCK(scp));
            return (errno = errcp);
        }
    }

    while ((subp =  EV_SUB_NEXT(scp)) != NULL) {
        EV_SUB_NEXT(scp) = subp->evsub_next;

        /* If door_xcreate was applied we can clean up */
        if (subp->evsub_attr)
            kill_door_servers(subp);

        if (door_revoke(subp->evsub_door_desc) != 0 && errno == EPERM)
            (void) close(subp->evsub_door_desc);

        free(subp->evsub_sid);
        free(subp);
    }

    (void) mutex_unlock(EV_LOCK(scp));

    /*
     * The close of the driver will do the unsubscribe if a) it is the last
     * close and b) we are in a child which inherited subscriptions.
     */
    (void) close(EV_FD(scp));
    (void) mutex_destroy(EV_LOCK(scp));
    free(scp);

    return (0);
}

/*
 * sysevent_evc_publish - Generate a system event via an event channel
 */
int
sysevent_evc_publish(evchan_t *scp, const char *class,
    const char *subclass, const char *vendor,
    const char *pub_name, nvlist_t *attr_list,
    uint32_t flags)
{
    sysevent_t *ev;
    sev_publish_args_t uargs;
    int rc;
    int ec;

    if (scp == NULL || misaligned(scp)) {
        return (errno = EINVAL);
    }

    /* No inheritance of binding handles via fork() */
    if (EV_PID(scp) != getpid()) {
        return (errno = EINVAL);
    }

    ev = sysevent_alloc_event((char *)class, (char *)subclass,
        (char *)vendor, (char *)pub_name, attr_list);
    if (ev == NULL) {
        return (errno);
    }

    uargs.ev.name = (uintptr_t)ev;
    uargs.ev.len = SE_SIZE(ev);
    uargs.flags = flags;

    (void) mutex_lock(EV_LOCK(scp));

    rc = ioctl(EV_FD(scp), SEV_PUBLISH, (intptr_t)&uargs);
    ec = errno;

    (void) mutex_unlock(EV_LOCK(scp));

    sysevent_free(ev);

    if (rc != 0) {
        return (ec);
    }
    return (0);
}

/*
 * Generic callback which catches events from the kernel and calls
 * subscribers call back routine.
 *
 * Kernel guarantees that door_upcalls are disabled when unsubscription
 * was issued that's why cookie points always to a valid evchan_subscr_t *.
 *
 * Furthermore it's not necessary to lock subp because the sysevent
 * framework guarantees no unsubscription until door_return.
 */
/*ARGSUSED3*/
static void
door_upcall(void *cookie, char *args, size_t alen,
    door_desc_t *ddp, uint_t ndid)
{
    evchan_subscr_t *subp = EVCHAN_SUBSCR(cookie);
    int rval = 0;

    /*
     * If we've been invoked simply to kill the thread then
     * exit now.
     */
    if (subp->evsub_state == EVCHAN_SUB_STATE_CLOSING)
        pthread_exit(NULL);

    if (args == NULL || alen <= (size_t)0) {
        /* Skip callback execution */
        rval = EINVAL;
    } else {
        rval = subp->evsub_func((sysevent_t *)(void *)args,
            subp->evsub_cookie);
    }

    /*
     * Fill in return values for door_return
     */
    alen = sizeof (rval);
    bcopy(&rval, args, alen);

    (void) door_return(args, alen, NULL, 0);
}

static pthread_once_t xsub_thrattr_once = PTHREAD_ONCE_INIT;
static pthread_attr_t xsub_thrattr;

static void
xsub_thrattr_init(void)
{
    (void) pthread_attr_init(&xsub_thrattr);
    (void) pthread_attr_setdetachstate(&xsub_thrattr,
        PTHREAD_CREATE_DETACHED);
    (void) pthread_attr_setscope(&xsub_thrattr, PTHREAD_SCOPE_SYSTEM);
}

/*
 * Our door server create function is only called during initial
 * door_xcreate since we specify DOOR_NO_DEPLETION_CB.
 */
int
xsub_door_server_create(door_info_t *dip, void *(*startf)(void *),
    void *startfarg, void *cookie)
{
    evchan_subscr_t *subp = EVCHAN_SUBSCR(cookie);
    struct sysevent_subattr_impl *xsa = subp->evsub_attr;
    pthread_attr_t *thrattr;
    sigset_t oset;
    int err;

    if (subp->evsub_state == EVCHAN_SUB_STATE_CLOSING)
        return (0); /* shouldn't happen, but just in case */

    /*
     * If sysevent_evc_xsubscribe was called electing to use a
     * different door server create function then let it take it
     * from here.
     */
    if (xsa->xs_thrcreate) {
        return (xsa->xs_thrcreate(dip, startf, startfarg,
            xsa->xs_thrcreate_cookie));
    }

    if (xsa->xs_thrattr == NULL) {
        (void) pthread_once(&xsub_thrattr_once, xsub_thrattr_init);
        thrattr = &xsub_thrattr;
    } else {
        thrattr = xsa->xs_thrattr;
    }

    (void) pthread_sigmask(SIG_SETMASK, &xsa->xs_sigmask, &oset);
    err = pthread_create(NULL, thrattr, startf, startfarg);
    (void) pthread_sigmask(SIG_SETMASK, &oset, NULL);

    return (err == 0 ? 1 : -1);
}

void
xsub_door_server_setup(void *cookie)
{
    evchan_subscr_t *subp = EVCHAN_SUBSCR(cookie);
    struct sysevent_subattr_impl *xsa = subp->evsub_attr;

    if (xsa->xs_thrsetup == NULL) {
        (void) pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, NULL);
        (void) pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, NULL);
    }

    (void) pthread_setspecific(nrkey, (void *)subp);

    if (xsa->xs_thrsetup)
        xsa->xs_thrsetup(xsa->xs_thrsetup_cookie);
}

/*
 * Cause private door server threads to exit.  We have already performed the
 * unsubscribe ioctl which stops new invocations and waits until all
 * existing invocations are complete.  So all server threads should be
 * blocked in door_return.  The door has not yet been revoked.  We will
 * invoke repeatedly after setting the evsub_state to be noticed on
 * wakeup; each invocation will result in the death of one server thread.
 *
 * You'd think it would be easier to kill these threads, such as through
 * pthread_cancel.  Unfortunately door_return is not a cancellation point,
 * and if you do cancel a thread blocked in door_return the EINTR check in
 * the door_return assembly logic causes us to loop with EINTR forever!
 */
static void
kill_door_servers(evchan_subscr_t *subp)
{
    door_arg_t da;

    bzero(&da, sizeof (da));
    subp->evsub_state = EVCHAN_SUB_STATE_CLOSING;
    membar_producer();

    (void) door_call(subp->evsub_door_desc, &da);
}

static int
sysevent_evc_subscribe_cmn(evchan_t *scp, const char *sid, const char *class,
    int (*event_handler)(sysevent_t *ev, void *cookie),
    void *cookie, uint32_t flags, struct sysevent_subattr_impl *xsa)
{
    evchan_subscr_t *subp;
    int upcall_door;
    sev_subscribe_args_t uargs;
    uint32_t sid_len;
    uint32_t class_len;
    int ec;

    if (scp == NULL || misaligned(scp) || sid == NULL || class == NULL) {
        return (errno = EINVAL);
    }

    /* No inheritance of binding handles via fork() */
    if (EV_PID(scp) != getpid()) {
        return (errno = EINVAL);
    }

    if ((sid_len = strlen(sid) + 1) > MAX_SUBID_LEN || sid_len == 1 ||
        (class_len = strlen(class) + 1) > MAX_CLASS_LEN) {
        return (errno = EINVAL);
    }

    /* Check for printable characters */
    if (!strisprint(sid)) {
        return (errno = EINVAL);
    }

    if (event_handler == NULL) {
        return (errno = EINVAL);
    }

    if (pthread_key_create_once_np(&nrkey, NULL) != 0)
        return (errno); /* ENOMEM or EAGAIN */

    /* Create subscriber data */
    if ((subp = calloc(1, sizeof (evchan_subscr_t))) == NULL) {
        return (errno);
    }

    if ((subp->evsub_sid = strdup(sid)) == NULL) {
        ec = errno;
        free(subp);
        return (ec);
    }

    /*
     * EC_ALL string will not be copied to kernel - NULL is assumed
     */
    if (strcmp(class, EC_ALL) == 0) {
        class = NULL;
        class_len = 0;
    }

    /*
     * Fill this in now for the xsub_door_server_setup dance
     */
    subp->ev_subhead = EVCHAN_IMPL_HNDL(scp);
    subp->evsub_state = EVCHAN_SUB_STATE_ACTIVE;

    if (xsa == NULL) {
        upcall_door = door_create(door_upcall, (void *)subp,
            DOOR_REFUSE_DESC | DOOR_NO_CANCEL);
    } else {
        subp->evsub_attr = xsa;

        /*
         * Create a private door with exactly one thread to
         * service the callbacks (the GPEC kernel implementation
         * serializes deliveries for each subscriber id).
         */
        upcall_door = door_xcreate(door_upcall, (void *)subp,
            DOOR_REFUSE_DESC | DOOR_NO_CANCEL | DOOR_NO_DEPLETION_CB,
            xsub_door_server_create, xsub_door_server_setup,
            (void *)subp, 1);
    }

    if (upcall_door == -1) {
        ec = errno;
        free(subp->evsub_sid);
        free(subp);
        return (ec);
    }

    /* Complete subscriber information */
    subp->evsub_door_desc = upcall_door;
    subp->evsub_func = event_handler;
    subp->evsub_cookie = cookie;

    (void) mutex_lock(EV_LOCK(scp));

    uargs.sid.name = (uintptr_t)sid;
    uargs.sid.len = sid_len;
    uargs.class_info.name = (uintptr_t)class;
    uargs.class_info.len = class_len;
    uargs.door_desc = subp->evsub_door_desc;
    uargs.flags = flags;
    if (ioctl(EV_FD(scp), SEV_SUBSCRIBE, (intptr_t)&uargs) != 0) {
        ec = errno;
        (void) mutex_unlock(EV_LOCK(scp));
        if (xsa)
            kill_door_servers(subp);
        (void) door_revoke(upcall_door);
        free(subp->evsub_sid);
        free(subp);
        return (ec);
    }

    /* Attach to subscriber list */
    subp->evsub_next = EV_SUB_NEXT(scp);
    EV_SUB_NEXT(scp) = subp;

    (void) mutex_unlock(EV_LOCK(scp));

    return (0);
}

/*
 * sysevent_evc_subscribe - subscribe to an existing event channel
 * using a non-private door (which will create as many server threads
 * as the apparent maximum concurrency requirements suggest).
 */
int
sysevent_evc_subscribe(evchan_t *scp, const char *sid, const char *class,
    int (*event_handler)(sysevent_t *ev, void *cookie),
    void *cookie, uint32_t flags)
{
    return (sysevent_evc_subscribe_cmn(scp, sid, class, event_handler,
        cookie, flags, NULL));
}

static void
subattr_dfltinit(struct sysevent_subattr_impl *xsa)
{
    (void) sigfillset(&xsa->xs_sigmask);
    (void) sigdelset(&xsa->xs_sigmask, SIGABRT);
}

static struct sysevent_subattr_impl dfltsa;
pthread_once_t dfltsa_inited = PTHREAD_ONCE_INIT;

static void
init_dfltsa(void)
{
    subattr_dfltinit(&dfltsa);
}

/*
 * sysevent_evc_subscribe - subscribe to an existing event channel
 * using a private door with control over thread creation.
 */
int
sysevent_evc_xsubscribe(evchan_t *scp, const char *sid, const char *class,
    int (*event_handler)(sysevent_t *ev, void *cookie),
    void *cookie, uint32_t flags, sysevent_subattr_t *attr)
{
    struct sysevent_subattr_impl *xsa;

    if (attr != NULL) {
        xsa = (struct sysevent_subattr_impl *)attr;
    } else {
        xsa = &dfltsa;
        (void) pthread_once(&dfltsa_inited, init_dfltsa);
    }

    return (sysevent_evc_subscribe_cmn(scp, sid, class, event_handler,
        cookie, flags, xsa));
}

sysevent_subattr_t *
sysevent_subattr_alloc(void)
{
    struct sysevent_subattr_impl *xsa = calloc(1, sizeof (*xsa));

    if (xsa != NULL)
        subattr_dfltinit(xsa);

    return (xsa != NULL ? (sysevent_subattr_t *)xsa : NULL);
}

void
sysevent_subattr_free(sysevent_subattr_t *attr)
{
    struct sysevent_subattr_impl *xsa =
        (struct sysevent_subattr_impl *)attr;

    free(xsa);
}

void
sysevent_subattr_thrcreate(sysevent_subattr_t *attr,
    door_xcreate_server_func_t *thrcreate, void *cookie)
{
    struct sysevent_subattr_impl *xsa =
        (struct sysevent_subattr_impl *)attr;

    xsa->xs_thrcreate = thrcreate;
    xsa->xs_thrcreate_cookie = cookie;
}

void
sysevent_subattr_thrsetup(sysevent_subattr_t *attr,
    door_xcreate_thrsetup_func_t *thrsetup, void *cookie)
{
    struct sysevent_subattr_impl *xsa =
        (struct sysevent_subattr_impl *)attr;

    xsa->xs_thrsetup = thrsetup;
    xsa->xs_thrsetup_cookie = cookie;
}

void
sysevent_subattr_sigmask(sysevent_subattr_t *attr, sigset_t *set)
{
    struct sysevent_subattr_impl *xsa =
        (struct sysevent_subattr_impl *)attr;

    if (set) {
        xsa->xs_sigmask = *set;
    } else {
        (void) sigfillset(&xsa->xs_sigmask);
        (void) sigdelset(&xsa->xs_sigmask, SIGABRT);
    }
}

void
sysevent_subattr_thrattr(sysevent_subattr_t *attr, pthread_attr_t *thrattr)
{
    struct sysevent_subattr_impl *xsa =
        (struct sysevent_subattr_impl *)attr;

    xsa->xs_thrattr = thrattr;
}

/*
 * sysevent_evc_unsubscribe - Unsubscribe from an existing event channel
 */
int
sysevent_evc_unsubscribe(evchan_t *scp, const char *sid)
{
    int all_subscribers = 0;
    sev_unsubscribe_args_t uargs;
    evchan_subscr_t *subp, *prevsubp, *tofree;
    int errcp;
    int rc;

    if (scp == NULL || misaligned(scp))
        return (errno = EINVAL);

    if (sid == NULL || strlen(sid) == 0 ||
        (strlen(sid) >= MAX_SUBID_LEN))
        return (errno = EINVAL);

    /* No inheritance of binding handles via fork() */
    if (EV_PID(scp) != getpid())
        return (errno = EINVAL);

    if (strcmp(sid, EVCH_ALLSUB) == 0) {
        all_subscribers++;
        /* Indicates all subscriber id's for this channel */
        uargs.sid.name = NULL;
        uargs.sid.len = 0;
    } else {
        uargs.sid.name = (uintptr_t)sid;
        uargs.sid.len = strlen(sid) + 1;
    }

    if (will_deadlock(scp))
        return (errno = EDEADLK);

    (void) mutex_lock(EV_LOCK(scp));

    /*
     * The unsubscribe ioctl will block until all door upcalls have drained.
     */
    rc = ioctl(EV_FD(scp), SEV_UNSUBSCRIBE, (intptr_t)&uargs);

    if (rc != 0) {
        errcp = errno;
        (void) mutex_unlock(EV_LOCK(scp));
        return (errno = errcp); /* EFAULT, ENXIO, EINVAL possible */
    }


    /*
     * Search for the matching subscriber.  If EVCH_ALLSUB was specified
     * then the ioctl above will have returned 0 even if there are
     * no subscriptions, so the initial EV_SUB_NEXT can be NULL.
     */
    prevsubp = NULL;
    subp =  EV_SUB_NEXT(scp);
    while (subp != NULL) {
        if (all_subscribers || strcmp(subp->evsub_sid, sid) == 0) {
            if (prevsubp == NULL) {
                EV_SUB_NEXT(scp) = subp->evsub_next;
            } else {
                prevsubp->evsub_next = subp->evsub_next;
            }

            tofree = subp;
            subp = subp->evsub_next;

            /* If door_xcreate was applied we can clean up */
            if (tofree->evsub_attr)
                kill_door_servers(tofree);

            (void) door_revoke(tofree->evsub_door_desc);
            free(tofree->evsub_sid);
            free(tofree);

            /* Freed single subscriber already? */
            if (all_subscribers == 0)
                break;
        } else {
            prevsubp = subp;
            subp = subp->evsub_next;
        }
    }

    (void) mutex_unlock(EV_LOCK(scp));

    return (0);
}

/*
 * sysevent_evc_control - Various channel based control operation
 */
int
sysevent_evc_control(evchan_t *scp, int cmd, /* arg */ ...)
{
    va_list ap;
    uint32_t *chlenp;
    sev_control_args_t uargs;
    int rc = 0;

    if (scp == NULL || misaligned(scp)) {
        return (errno = EINVAL);
    }

    /* No inheritance of binding handles via fork() */
    if (EV_PID(scp) != getpid()) {
        return (errno = EINVAL);
    }

    va_start(ap, cmd);

    uargs.cmd = cmd;

    (void) mutex_lock(EV_LOCK(scp));

    switch (cmd) {
    case EVCH_GET_CHAN_LEN:
    case EVCH_GET_CHAN_LEN_MAX:
        chlenp = va_arg(ap, uint32_t *);
        if (chlenp == NULL || misaligned(chlenp)) {
            rc = EINVAL;
            break;
        }
        rc = ioctl(EV_FD(scp), SEV_CHAN_CONTROL, (intptr_t)&uargs);
        *chlenp = uargs.value;
        break;

    case EVCH_SET_CHAN_LEN:
        /* Range change will be handled in framework */
        uargs.value = va_arg(ap, uint32_t);
        rc = ioctl(EV_FD(scp), SEV_CHAN_CONTROL, (intptr_t)&uargs);
        break;

    default:
        rc = EINVAL;
    }

    (void) mutex_unlock(EV_LOCK(scp));

    if (rc == -1) {
        rc = errno;
    }

    va_end(ap);

    return (errno = rc);
}

int
sysevent_evc_setpropnvl(evchan_t *scp, nvlist_t *nvl)
{
    sev_propnvl_args_t uargs;
    char *buf = NULL;
    size_t nvlsz = 0;
    int rc;

    if (scp == NULL || misaligned(scp))
        return (errno = EINVAL);

    if (nvl != NULL &&
        nvlist_pack(nvl, &buf, &nvlsz, NV_ENCODE_NATIVE, 0) != 0)
        return (errno);

    uargs.packednvl.name = (uint64_t)(uintptr_t)buf;
    uargs.packednvl.len = (uint32_t)nvlsz;

    rc = ioctl(EV_FD(scp), SEV_SETPROPNVL, (intptr_t)&uargs);

    if (buf)
        free(buf);

    return (rc);
}

int
sysevent_evc_getpropnvl(evchan_t *scp, nvlist_t **nvlp)
{
    sev_propnvl_args_t uargs;
    char buf[1024], *bufp = buf;    /* stack buffer */
    size_t sz = sizeof (buf);
    char *buf2 = NULL;      /* allocated if stack buf too small */
    int64_t expgen = -1;
    int rc;

    if (scp == NULL || misaligned(scp) || nvlp == NULL)
        return (errno = EINVAL);

    *nvlp = NULL;

again:
    uargs.packednvl.name = (uint64_t)(uintptr_t)bufp;
    uargs.packednvl.len = (uint32_t)sz;

    rc = ioctl(EV_FD(scp), SEV_GETPROPNVL, (intptr_t)&uargs);

    if (rc == E2BIG)
        return (errno = E2BIG); /* driver refuses to copyout */

    /*
     * If the packed nvlist is too big for the buffer size we offered
     * then the ioctl returns EOVERFLOW and indicates in the 'len'
     * the size required for the current property nvlist generation
     * (itself returned in the generation member).
     */
    if (rc == EOVERFLOW &&
        (buf2 == NULL || uargs.generation != expgen)) {
        if (buf2 != NULL)
            free(buf2);

        if ((sz = uargs.packednvl.len) > 1024 * 1024)
            return (E2BIG);

        bufp = buf2 = malloc(sz);

        if (buf2 == NULL)
            return (errno = ENOMEM);

        expgen = uargs.generation;
        goto again;
    }

    /*
     * The chan prop nvlist can be absent, in which case the ioctl
     * returns success and uargs.packednvl.len of 0;  we have already
     * set *nvlp to NULL.  Otherwise we must unpack the nvl.
     */
    if (rc == 0 && uargs.packednvl.len != 0 &&
        nvlist_unpack(bufp, uargs.packednvl.len, nvlp, 0) != 0)
        rc = EINVAL;

    if (buf2 != NULL)
        free(buf2);

    return (rc ? errno = rc : 0);
}