/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2007 Pawel Jakub Dawidek <pjd@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 AUTHORS 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 AUTHORS 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.
 */

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/systm.h>
#include <sys/sysctl.h>
#include <sys/errno.h>
#include <sys/jail.h>
#include <sys/malloc.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/rmlock.h>
#include <sys/sx.h>
#include <sys/queue.h>
#include <sys/proc.h>
#include <sys/osd.h>

/* OSD (Object Specific Data) */

/*
 * Lock key:
 *  (m) osd_module_lock
 *  (o) osd_object_lock
 *  (l) osd_list_lock
 */
struct osd_master {
        struct sx                osd_module_lock;
        struct rmlock            osd_object_lock;
        struct mtx               osd_list_lock;
        LIST_HEAD(, osd)         osd_list;              /* (l) */
        osd_destructor_t        *osd_destructors;       /* (o) */
        osd_method_t            *osd_methods;           /* (m) */
        u_int                    osd_ntslots;           /* (m) */
        const u_int              osd_nmethods;
};

static MALLOC_DEFINE(M_OSD, "osd", "Object Specific Data");

static int osd_debug = 0;
SYSCTL_INT(_debug, OID_AUTO, osd, CTLFLAG_RWTUN, &osd_debug, 0, "OSD debug level");

#define OSD_DEBUG(...)  do {                                            \
        if (osd_debug) {                                                \
                printf("OSD (%s:%u): ", __func__, __LINE__);            \
                printf(__VA_ARGS__);                                    \
                printf("\n");                                           \
        }                                                               \
} while (0)

static void do_osd_del(u_int type, struct osd *osd, u_int slot,
    int list_locked);

/*
 * List of objects with OSD.
 */
struct osd_master osdm[OSD_LAST + 1] = {
        [OSD_JAIL] = { .osd_nmethods = PR_MAXMETHOD },
};

static void
osd_default_destructor(void *value __unused)
{
        /* Do nothing. */
}

int
osd_register(u_int type, osd_destructor_t destructor, const osd_method_t *methods)
{
        void *newptr;
        u_int i, m;

        KASSERT(type >= OSD_FIRST && type <= OSD_LAST, ("Invalid type."));

        /*
         * If no destructor is given, use default one. We need to use some
         * destructor, because NULL destructor means unused slot.
         */
        if (destructor == NULL)
                destructor = osd_default_destructor;

        sx_xlock(&osdm[type].osd_module_lock);
        /*
         * First, we try to find unused slot.
         */
        for (i = 0; i < osdm[type].osd_ntslots; i++) {
                if (osdm[type].osd_destructors[i] == NULL) {
                        OSD_DEBUG("Unused slot found (type=%u, slot=%u).",
                            type, i + 1);
                        break;
                }
        }
        /*
         * If no unused slot was found, allocate one.
         */
        if (i == osdm[type].osd_ntslots) {
                osdm[type].osd_ntslots++;
                if (osdm[type].osd_nmethods != 0)
                        osdm[type].osd_methods = realloc(osdm[type].osd_methods,
                            sizeof(osd_method_t) * osdm[type].osd_ntslots *
                            osdm[type].osd_nmethods, M_OSD, M_WAITOK);
                newptr = malloc(sizeof(osd_destructor_t) *
                    osdm[type].osd_ntslots, M_OSD, M_WAITOK);
                rm_wlock(&osdm[type].osd_object_lock);
                bcopy(osdm[type].osd_destructors, newptr,
                    sizeof(osd_destructor_t) * i);
                free(osdm[type].osd_destructors, M_OSD);
                osdm[type].osd_destructors = newptr;
                rm_wunlock(&osdm[type].osd_object_lock);
                OSD_DEBUG("New slot allocated (type=%u, slot=%u).",
                    type, i + 1);
        }

        osdm[type].osd_destructors[i] = destructor;
        if (osdm[type].osd_nmethods != 0) {
                for (m = 0; m < osdm[type].osd_nmethods; m++)
                        osdm[type].osd_methods[i * osdm[type].osd_nmethods + m]
                            = methods != NULL ? methods[m] : NULL;
        }
        sx_xunlock(&osdm[type].osd_module_lock);
        return (i + 1);
}

void
osd_deregister(u_int type, u_int slot)
{
        struct osd *osd, *tosd;

        KASSERT(type >= OSD_FIRST && type <= OSD_LAST, ("Invalid type."));
        KASSERT(slot > 0, ("Invalid slot."));

        sx_xlock(&osdm[type].osd_module_lock);
        rm_wlock(&osdm[type].osd_object_lock);
        KASSERT(osdm[type].osd_destructors[slot - 1] != NULL, ("Unused slot."));

        /*
         * Free all OSD for the given slot.
         */
        mtx_lock(&osdm[type].osd_list_lock);
        LIST_FOREACH_SAFE(osd, &osdm[type].osd_list, osd_next, tosd)
                do_osd_del(type, osd, slot, 1);
        mtx_unlock(&osdm[type].osd_list_lock);

        /*
         * Set destructor to NULL to free the slot.  We don't bother actually
         * freeing any memory here because we'll gracefully reuse any freed
         * slots, and reallocating the arrays as a smaller chunk of memory isn't
         * actually guaranteed to succeed.  As such, we'll err on the side of
         * caution and just leave it be since these are generally modestly sized
         * allocations.
         */
        osdm[type].osd_destructors[slot - 1] = NULL;
        OSD_DEBUG("Slot deregistration (type=%u, slot=%u).", type, slot);

        rm_wunlock(&osdm[type].osd_object_lock);
        sx_xunlock(&osdm[type].osd_module_lock);
}

int
osd_set(u_int type, struct osd *osd, u_int slot, void *value)
{

        return (osd_set_reserved(type, osd, slot, NULL, value));
}

void **
osd_reserve(u_int slot)
{

        KASSERT(slot > 0, ("Invalid slot."));

        OSD_DEBUG("Reserving slot array (slot=%u).", slot);
        return (malloc(sizeof(void *) * slot, M_OSD, M_WAITOK | M_ZERO));
}

int
osd_set_reserved(u_int type, struct osd *osd, u_int slot, void **rsv,
    void *value)
{
        struct rm_priotracker tracker;

        KASSERT(type >= OSD_FIRST && type <= OSD_LAST, ("Invalid type."));
        KASSERT(slot > 0, ("Invalid slot."));

        rm_rlock(&osdm[type].osd_object_lock, &tracker);
        KASSERT(osdm[type].osd_destructors[slot - 1] != NULL, ("Unused slot."));

        if (slot > osd->osd_nslots) {
                void **newptr;

                if (value == NULL) {
                        OSD_DEBUG(
                            "Not allocating null slot (type=%u, slot=%u).",
                            type, slot);
                        rm_runlock(&osdm[type].osd_object_lock, &tracker);
                        if (rsv)
                                osd_free_reserved(rsv);
                        return (0);
                }

                /*
                 * Too few slots allocated here, so we need to extend or create
                 * the array.
                 */
                if (rsv) {
                        /*
                         * Use the reserve passed in (assumed to be
                         * the right size).
                         */
                        newptr = rsv;
                        if (osd->osd_nslots != 0) {
                                memcpy(newptr, osd->osd_slots,
                                    sizeof(void *) * osd->osd_nslots);
                                free(osd->osd_slots, M_OSD);
                        }
                } else {
                        newptr = realloc(osd->osd_slots, sizeof(void *) * slot,
                            M_OSD, M_NOWAIT | M_ZERO);
                        if (newptr == NULL) {
                                rm_runlock(&osdm[type].osd_object_lock,
                                    &tracker);
                                return (ENOMEM);
                        }
                }
                if (osd->osd_nslots == 0) {
                        /*
                         * First OSD for this object, so we need to put it
                         * onto the list.
                         */
                        mtx_lock(&osdm[type].osd_list_lock);
                        LIST_INSERT_HEAD(&osdm[type].osd_list, osd, osd_next);
                        mtx_unlock(&osdm[type].osd_list_lock);
                        OSD_DEBUG("Setting first slot (type=%u).", type);
                } else
                        OSD_DEBUG("Growing slots array (type=%u).", type);
                osd->osd_slots = newptr;
                osd->osd_nslots = slot;
        } else if (rsv)
                osd_free_reserved(rsv);
        OSD_DEBUG("Setting slot value (type=%u, slot=%u, value=%p).", type,
            slot, value);
        osd->osd_slots[slot - 1] = value;
        rm_runlock(&osdm[type].osd_object_lock, &tracker);
        return (0);
}

void
osd_free_reserved(void **rsv)
{

        OSD_DEBUG("Discarding reserved slot array.");
        free(rsv, M_OSD);
}

void *
osd_get_unlocked(u_int type, struct osd *osd, u_int slot)
{
        void *value;

        KASSERT(osdm[type].osd_destructors[slot - 1] != NULL, ("Unused slot."));

        if (slot > osd->osd_nslots) {
                value = NULL;
                OSD_DEBUG("Slot doesn't exist (type=%u, slot=%u).", type, slot);
        } else {
                value = atomic_load_ptr(&osd->osd_slots[slot - 1]);
                OSD_DEBUG("Returning slot value (type=%u, slot=%u, value=%p).",
                    type, slot, value);
        }
        return (value);
}

void *
osd_get(u_int type, struct osd *osd, u_int slot)
{
        struct rm_priotracker tracker;
        void *value;

        KASSERT(type >= OSD_FIRST && type <= OSD_LAST, ("Invalid type."));
        KASSERT(slot > 0, ("Invalid slot."));

        rm_rlock(&osdm[type].osd_object_lock, &tracker);
        value = osd_get_unlocked(type, osd, slot);
        rm_runlock(&osdm[type].osd_object_lock, &tracker);
        return (value);
}

void
osd_del(u_int type, struct osd *osd, u_int slot)
{
        struct rm_priotracker tracker;

        rm_rlock(&osdm[type].osd_object_lock, &tracker);
        do_osd_del(type, osd, slot, 0);
        rm_runlock(&osdm[type].osd_object_lock, &tracker);
}

static void
do_osd_del(u_int type, struct osd *osd, u_int slot, int list_locked)
{
        int i;

        KASSERT(type >= OSD_FIRST && type <= OSD_LAST, ("Invalid type."));
        KASSERT(slot > 0, ("Invalid slot."));
        KASSERT(osdm[type].osd_destructors[slot - 1] != NULL, ("Unused slot."));

        OSD_DEBUG("Deleting slot (type=%u, slot=%u).", type, slot);

        if (slot > osd->osd_nslots) {
                OSD_DEBUG("Slot doesn't exist (type=%u, slot=%u).", type, slot);
                return;
        }
        if (osd->osd_slots[slot - 1] != NULL) {
                osdm[type].osd_destructors[slot - 1](osd->osd_slots[slot - 1]);
                osd->osd_slots[slot - 1] = NULL;
        }
        for (i = osd->osd_nslots - 1; i >= 0; i--) {
                if (osd->osd_slots[i] != NULL) {
                        OSD_DEBUG("Slot still has a value (type=%u, slot=%u).",
                            type, i + 1);
                        break;
                }
        }
        if (i == -1) {
                /* No values left for this object. */
                OSD_DEBUG("No more slots left (type=%u).", type);
                if (!list_locked)
                        mtx_lock(&osdm[type].osd_list_lock);
                LIST_REMOVE(osd, osd_next);
                if (!list_locked)
                        mtx_unlock(&osdm[type].osd_list_lock);
                free(osd->osd_slots, M_OSD);
                osd->osd_slots = NULL;
                osd->osd_nslots = 0;
        } else if (slot == osd->osd_nslots) {
                /* This was the last slot. */
                osd->osd_slots = realloc(osd->osd_slots,
                    sizeof(void *) * (i + 1), M_OSD, M_NOWAIT | M_ZERO);
                /*
                 * We always reallocate to smaller size, so we assume it will
                 * always succeed.
                 */
                KASSERT(osd->osd_slots != NULL, ("realloc() failed"));
                osd->osd_nslots = i + 1;
                OSD_DEBUG("Reducing slots array to %u (type=%u).",
                    osd->osd_nslots, type);
        }
}

int
osd_call(u_int type, u_int method, void *obj, void *data)
{
        osd_method_t methodfun;
        int error, i;

        KASSERT(type >= OSD_FIRST && type <= OSD_LAST, ("Invalid type."));
        KASSERT(method < osdm[type].osd_nmethods, ("Invalid method."));

        /*
         * Call this method for every slot that defines it, stopping if an
         * error is encountered.
         */
        error = 0;
        sx_slock(&osdm[type].osd_module_lock);
        for (i = 0; i < osdm[type].osd_ntslots; i++) {
                /* Hole in the slot map; avoid dereferencing. */
                if (osdm[type].osd_destructors[i] == NULL)
                        continue;
                methodfun = osdm[type].osd_methods[i * osdm[type].osd_nmethods +
                    method];
                if (methodfun != NULL && (error = methodfun(obj, data)) != 0)
                        break;
        }
        sx_sunlock(&osdm[type].osd_module_lock);
        return (error);
}

void
osd_exit(u_int type, struct osd *osd)
{
        struct rm_priotracker tracker;
        u_int i;

        KASSERT(type >= OSD_FIRST && type <= OSD_LAST, ("Invalid type."));

        if (osd->osd_nslots == 0) {
                KASSERT(osd->osd_slots == NULL, ("Non-null osd_slots."));
                /* No OSD attached, just leave. */
                return;
        }

        rm_rlock(&osdm[type].osd_object_lock, &tracker);
        for (i = 1; i <= osd->osd_nslots; i++) {
                if (osdm[type].osd_destructors[i - 1] != NULL)
                        do_osd_del(type, osd, i, 0);
                else
                        OSD_DEBUG("Unused slot (type=%u, slot=%u).", type, i);
        }
        rm_runlock(&osdm[type].osd_object_lock, &tracker);
        OSD_DEBUG("Object exit (type=%u).", type);
}

static void
osd_init(void *arg __unused)
{
        u_int i;

        for (i = OSD_FIRST; i <= OSD_LAST; i++) {
                sx_init(&osdm[i].osd_module_lock, "osd_module");
                rm_init(&osdm[i].osd_object_lock, "osd_object");
                mtx_init(&osdm[i].osd_list_lock, "osd_list", NULL, MTX_DEF);
                LIST_INIT(&osdm[i].osd_list);
                osdm[i].osd_destructors = NULL;
                osdm[i].osd_ntslots = 0;
                osdm[i].osd_methods = NULL;
        }
}
SYSINIT(osd, SI_SUB_LOCK, SI_ORDER_ANY, osd_init, NULL);