subr_kobj.c

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/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 2000,2003 Doug Rabson
 * 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 AUTHOR 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 AUTHOR 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/cdefs.h>
__FBSDID("$FreeBSD$");
 
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/kobj.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/sysctl.h>
#ifndef TEST
#include <sys/systm.h>
#endif
 
#ifdef TEST
#include "usertest.h"
#endif
 
static MALLOC_DEFINE(M_KOBJ, "kobj", "Kernel object structures");
 
#ifdef KOBJ_STATS
 
u_int kobj_lookup_hits;
u_int kobj_lookup_misses;
 
SYSCTL_UINT(_kern, OID_AUTO, kobj_hits, CTLFLAG_RD,
           &kobj_lookup_hits, 0, "");
SYSCTL_UINT(_kern, OID_AUTO, kobj_misses, CTLFLAG_RD,
           &kobj_lookup_misses, 0, "");
 
#endif
 
static struct mtx kobj_mtx;
static int kobj_mutex_inited;
static int kobj_next_id = 1;
 
#define KOBJ_LOCK()             mtx_lock(&kobj_mtx)
#define KOBJ_UNLOCK()           mtx_unlock(&kobj_mtx)
#define KOBJ_ASSERT(what)       mtx_assert(&kobj_mtx, what);
 
SYSCTL_INT(_kern, OID_AUTO, kobj_methodcount, CTLFLAG_RD,
    &kobj_next_id, 0,
    "Number of kernel object methods registered");
 
static void
kobj_init_mutex(void *arg)
{
        if (!kobj_mutex_inited) {
                mtx_init(&kobj_mtx, "kobj", NULL, MTX_DEF);
                kobj_mutex_inited = 1;
        }
}
 
SYSINIT(kobj, SI_SUB_LOCK, SI_ORDER_ANY, kobj_init_mutex, NULL);
 
/*
 * This method structure is used to initialise new caches. Since the
 * desc pointer is NULL, it is guaranteed never to match any read
 * descriptors.
 */
static const struct kobj_method null_method = {
        0, 0,
};
 
int
kobj_error_method(void)
{
 
        return ENXIO;
}
 
static void
kobj_class_compile_common(kobj_class_t cls, kobj_ops_t ops)
{
        kobj_method_t *m;
        int i;
 
        /*
         * Don't do anything if we are already compiled.
         */
        if (cls->ops)
                return;
 
        /*
         * First register any methods which need it.
         */
        for (m = cls->methods; m->desc; m++) {
                if (m->desc->id == 0)
                        m->desc->id = kobj_next_id++;
        }
 
        /*
         * Then initialise the ops table.
         */
        for (i = 0; i < KOBJ_CACHE_SIZE; i++)
                ops->cache[i] = &null_method;
        ops->cls = cls;
        cls->ops = ops;
}
 
static int
kobj_class_compile1(kobj_class_t cls, int mflags)
{
        kobj_ops_t ops;
 
        KOBJ_ASSERT(MA_NOTOWNED);
 
        ops = malloc(sizeof(struct kobj_ops), M_KOBJ, mflags);
        if (ops == NULL)
                return (ENOMEM);
 
        /*
         * We may have lost a race for kobj_class_compile here - check
         * to make sure someone else hasn't already compiled this
         * class.
         */
        KOBJ_LOCK();
        if (cls->ops) {
                KOBJ_UNLOCK();
                free(ops, M_KOBJ);
                return (0);
        }
        kobj_class_compile_common(cls, ops);
        KOBJ_UNLOCK();
        return (0);
}
 
void
kobj_class_compile(kobj_class_t cls)
{
        int error __diagused;
 
        error = kobj_class_compile1(cls, M_WAITOK);
        KASSERT(error == 0, ("kobj_class_compile1 returned %d", error));
}
 
void
kobj_class_compile_static(kobj_class_t cls, kobj_ops_t ops)
{
 
        KASSERT(kobj_mutex_inited == 0,
            ("%s: only supported during early cycles", __func__));
 
        /*
         * Increment refs to make sure that the ops table is not freed.
         */
        cls->refs++;
        kobj_class_compile_common(cls, ops);
}
 
static kobj_method_t*
kobj_lookup_method_class(kobj_class_t cls, kobjop_desc_t desc)
{
        kobj_method_t *methods = cls->methods;
        kobj_method_t *ce;
 
        for (ce = methods; ce && ce->desc; ce++) {
                if (ce->desc == desc) {
                        return ce;
                }
        }
 
        return NULL;
}
 
static kobj_method_t*
kobj_lookup_method_mi(kobj_class_t cls,
                      kobjop_desc_t desc)
{
        kobj_method_t *ce;
        kobj_class_t *basep;
 
        ce = kobj_lookup_method_class(cls, desc);
        if (ce)
                return ce;
 
        basep = cls->baseclasses;
        if (basep) {
                for (; *basep; basep++) {
                        ce = kobj_lookup_method_mi(*basep, desc);
                        if (ce)
                                return ce;
                }
        }
 
        return NULL;
}
 
kobj_method_t*
kobj_lookup_method(kobj_class_t cls,
                   kobj_method_t **cep,
                   kobjop_desc_t desc)
{
        kobj_method_t *ce;
 
        ce = kobj_lookup_method_mi(cls, desc);
        if (!ce)
                ce = &desc->deflt;
        if (cep)
                *cep = ce;
        return ce;
}
 
void
kobj_class_free(kobj_class_t cls)
{
        void* ops = NULL;
 
        KOBJ_ASSERT(MA_NOTOWNED);
        KOBJ_LOCK();
 
        /*
         * Protect against a race between kobj_create and
         * kobj_delete.
         */
        if (cls->refs == 0) {
                /*
                 * For now we don't do anything to unregister any methods
                 * which are no longer used.
                 */
 
                /*
                 * Free memory and clean up.
                 */
                ops = cls->ops;
                cls->ops = NULL;
        }
 
        KOBJ_UNLOCK();
 
        if (ops)
                free(ops, M_KOBJ);
}
 
static void
kobj_init_common(kobj_t obj, kobj_class_t cls)
{
 
        obj->ops = cls->ops;
        cls->refs++;
}
 
static int
kobj_init1(kobj_t obj, kobj_class_t cls, int mflags)
{
        int error;
 
        KOBJ_LOCK();
        while (cls->ops == NULL) {
                /*
                 * kobj_class_compile doesn't want the lock held
                 * because of the call to malloc - we drop the lock
                 * and re-try.
                 */
                KOBJ_UNLOCK();
                error = kobj_class_compile1(cls, mflags);
                if (error != 0)
                        return (error);
                KOBJ_LOCK();
        }
        kobj_init_common(obj, cls);
        KOBJ_UNLOCK();
        return (0);
}
 
kobj_t
kobj_create(kobj_class_t cls, struct malloc_type *mtype, int mflags)
{
        kobj_t obj;
 
        obj = malloc(cls->size, mtype, mflags | M_ZERO);
        if (obj == NULL)
                return (NULL);
        if (kobj_init1(obj, cls, mflags) != 0) {
                free(obj, mtype);
                return (NULL);
        }
        return (obj);
}
 
void
kobj_init(kobj_t obj, kobj_class_t cls)
{
        int error;
 
        error = kobj_init1(obj, cls, M_NOWAIT);
        if (error != 0)
                panic("kobj_init1 failed: error %d", error);
}
 
void
kobj_init_static(kobj_t obj, kobj_class_t cls)
{
 
        KASSERT(kobj_mutex_inited == 0,
            ("%s: only supported during early cycles", __func__));
 
        kobj_init_common(obj, cls);
}
 
void
kobj_delete(kobj_t obj, struct malloc_type *mtype)
{
        kobj_class_t cls = obj->ops->cls;
        int refs;
 
        /*
         * Consider freeing the compiled method table for the class
         * after its last instance is deleted. As an optimisation, we
         * should defer this for a short while to avoid thrashing.
         */
        KOBJ_ASSERT(MA_NOTOWNED);
        KOBJ_LOCK();
        cls->refs--;
        refs = cls->refs;
        KOBJ_UNLOCK();
 
        if (!refs)
                kobj_class_free(cls);
 
        obj->ops = NULL;
        if (mtype)
                free(obj, mtype);
}