lib/libsysevent/libevchannel.c

	libevchannel.c revision 7c478bd95313f5f23a4c958a745db2134aa03244
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (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 2005 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#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 <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
 */

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

/*
 * 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
 */
void
sysevent_evc_unbind(evchan_t *scp)
{
    sev_unsubscribe_args_t uargs;
    evchan_subscr_t *subp, *tofree;

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

    (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) {
            (void) mutex_unlock(EV_LOCK(scp));
            return;
        }
    }

    subp =  (evchan_subscr_t *)(void*)EV_SUB(scp);
    while (subp->evsub_next != NULL) {
        tofree = subp->evsub_next;
        subp->evsub_next = tofree->evsub_next;
        if (door_revoke(tofree->evsub_door_desc) != 0 && errno == EPERM)
            (void) close(tofree->evsub_door_desc);
        free(tofree->evsub_sid);
        free(tofree);
    }

    (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);
}

/*
 * 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 (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);
}

/*
 * sysevent_evc_subscribe - Subscribe to an existing event channel
 */
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)
{
    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);
    }

    /* 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;
    }

    upcall_door = door_create(door_upcall, (void *)subp,
        DOOR_REFUSE_DESC | DOOR_NO_CANCEL);
    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));

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

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

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

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

    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;
    }

    (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) {
        (void) mutex_unlock(EV_LOCK(scp));
        return;
    }

    /* Search for the matching subscriber */
    subp =  (evchan_subscr_t *)(void*)EV_SUB(scp);
    while (subp->evsub_next != NULL) {

        if (all_subscribers ||
            (strcmp(subp->evsub_next->evsub_sid, sid) == 0)) {

            tofree = subp->evsub_next;
            subp->evsub_next = tofree->evsub_next;
            (void) door_revoke(tofree->evsub_door_desc);
            free(tofree->evsub_sid);
            free(tofree);
            /* Freed single subscriber already */
            if (all_subscribers == 0) {
                break;
            }
        } else
            subp = subp->evsub_next;
    }

    (void) mutex_unlock(EV_LOCK(scp));
}

/*
 * 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);
}