/*      $NetBSD: subr_hash.c,v 1.12 2021/06/13 14:58:49 simonb Exp $    */

/*
* Copyright (c) 1982, 1986, 1991, 1993
*      The Regents of the University of California.  All rights reserved.
* (c) UNIX System Laboratories, Inc.
* All or some portions of this file are derived from material licensed
* to the University of California by American Telephone and Telegraph
* Co. or Unix System Laboratories, Inc. and are reproduced herein with
* the permission of UNIX System Laboratories, Inc.
*
* 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.
* 3. Neither the name of the University nor the names of its contributors
*    may be used to endorse or promote products derived from this software
*    without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
*
*      @(#)kern_subr.c 8.4 (Berkeley) 2/14/95
*/

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: subr_hash.c,v 1.12 2021/06/13 14:58:49 simonb Exp $");

#include <sys/param.h>
#include <sys/bitops.h>
#include <sys/kmem.h>
#include <sys/systm.h>
#include <sys/pslist.h>
#include <sys/rwlock.h>
#include <sys/sysctl.h>

static int hashstat_sysctl(SYSCTLFN_PROTO);

static size_t
hash_list_size(enum hashtype htype)
{
       LIST_HEAD(, generic) *hashtbl_list;
       SLIST_HEAD(, generic) *hashtbl_slist;
       TAILQ_HEAD(, generic) *hashtbl_tailq;
       struct pslist_head *hashtbl_pslist;
       size_t esize;

       switch (htype) {
       case HASH_LIST:
               esize = sizeof(*hashtbl_list);
               break;
       case HASH_PSLIST:
               esize = sizeof(*hashtbl_pslist);
               break;
       case HASH_SLIST:
               esize = sizeof(*hashtbl_slist);
               break;
       case HASH_TAILQ:
               esize = sizeof(*hashtbl_tailq);
               break;
       default:
               panic("hashdone: invalid table type");
       }
       return esize;
}

/*
* General routine to allocate a hash table.
* Allocate enough memory to hold at least `elements' list-head pointers.
* Return a pointer to the allocated space and set *hashmask to a pattern
* suitable for masking a value to use as an index into the returned array.
*/
void *
hashinit(u_int elements, enum hashtype htype, bool waitok, u_long *hashmask)
{
       LIST_HEAD(, generic) *hashtbl_list;
       SLIST_HEAD(, generic) *hashtbl_slist;
       TAILQ_HEAD(, generic) *hashtbl_tailq;
       struct pslist_head *hashtbl_pslist;
       u_long hashsize, i;
       size_t esize;
       void *p;

       KASSERT(elements > 0);

#define MAXELEMENTS (1U << ((sizeof(elements) * NBBY) - 1))
       if (elements > MAXELEMENTS)
               elements = MAXELEMENTS;

       hashsize = 1UL << (ilog2(elements - 1) + 1);
       esize = hash_list_size(htype);

       p = kmem_alloc(hashsize * esize, waitok ? KM_SLEEP : KM_NOSLEEP);
       if (p == NULL)
               return NULL;

       switch (htype) {
       case HASH_LIST:
               hashtbl_list = p;
               for (i = 0; i < hashsize; i++)
                       LIST_INIT(&hashtbl_list[i]);
               break;
       case HASH_PSLIST:
               hashtbl_pslist = p;
               for (i = 0; i < hashsize; i++)
                       PSLIST_INIT(&hashtbl_pslist[i]);
               break;
       case HASH_SLIST:
               hashtbl_slist = p;
               for (i = 0; i < hashsize; i++)
                       SLIST_INIT(&hashtbl_slist[i]);
               break;
       case HASH_TAILQ:
               hashtbl_tailq = p;
               for (i = 0; i < hashsize; i++)
                       TAILQ_INIT(&hashtbl_tailq[i]);
               break;
       }
       *hashmask = hashsize - 1;
       return p;
}

/*
* Free memory from hash table previosly allocated via hashinit().
*/
void
hashdone(void *hashtbl, enum hashtype htype, u_long hashmask)
{
       const size_t esize = hash_list_size(htype);
       kmem_free(hashtbl, esize * (hashmask + 1));
}

/*
* Support for hash statistics (vmstat -H / vmstat -h hashname).
*/

struct hashstat {
       const char *hs_name;
       hashstat_func_t hs_func;
       TAILQ_ENTRY(hashstat) hs_next;
};
TAILQ_HEAD(, hashstat) hashstat_list =
   TAILQ_HEAD_INITIALIZER(hashstat_list);
static krwlock_t hashstat_lock;

void
hashstat_register(const char *name, hashstat_func_t func)
{
       struct hashstat *hs;

       hs = kmem_alloc(sizeof(*hs), KM_SLEEP);

       hs->hs_name = name;
       hs->hs_func = func;

       rw_enter(&hashstat_lock, RW_WRITER);
       TAILQ_INSERT_TAIL(&hashstat_list, hs, hs_next);
       rw_exit(&hashstat_lock);
}

/*
* sysctl support for returning kernel hash statistics.
*
* We (ab)use CTL_DESCRIBE and CTL_QUERY:
* When passed an OID of CTL_DESCRIBE, return a list and description
* of the available hashes.
* When passed an OID of CTL_QUERY, use the hash name passed in the
* "new" hash input as the name of a single hash to return stats on.
*/
static int
hashstat_sysctl(SYSCTLFN_ARGS)
{
       struct hashstat_sysctl hs;
       struct hashstat *hash;
       char queryname[SYSCTL_NAMELEN];
       size_t written;
       bool fill, query;
       int error;

       if (oldp == NULL) {
               *oldlenp = 0;
               TAILQ_FOREACH(hash, &hashstat_list, hs_next)
                       *oldlenp += sizeof(hs);
               return 0;
       }

       error = 0;
       written = 0;

       if (namelen > 0 && name[0] == CTL_DESCRIBE)
               fill = false;
       else
               fill = true;

       if (namelen > 0 && name[0] == CTL_QUERY) {
               const struct hashstat_sysctl *h = newp;
               size_t s;

               if (h == NULL) {
                       /* Can't QUERY one hash without supplying the hash name. */
                       return EINVAL;
               }
               query = true;
               error = sysctl_copyinstr(l, h->hash_name, queryname,
                   sizeof(queryname), &s);
               if (error)
                       return error;
       } else {
               query = false;
       }

       sysctl_unlock();
       rw_enter(&hashstat_lock, RW_READER);
       TAILQ_FOREACH(hash, &hashstat_list, hs_next) {
               if (query && (strcmp(hash->hs_name, queryname) != 0)) {
                       continue;
               }

               memset(&hs, 0, sizeof(hs));
               error = hash->hs_func(&hs, fill);
               if (error)
                       break;

               error = sysctl_copyout(l, &hs, oldp, sizeof(hs));
               if (error)
                       break;
               written += sizeof(hs);
               oldp = (char *)oldp + sizeof(hs);
       }
       rw_exit(&hashstat_lock);
       sysctl_relock();

       if (query && written == 0)      /* query not found? */
               error = ENOENT;

       *oldlenp = written;
       return error;
}


SYSCTL_SETUP(sysctl_hash_setup, "sysctl hash stats setup")
{

       rw_init(&hashstat_lock);        /* as good a place as any for this */

       sysctl_createv(NULL, 0, NULL, NULL,
                      CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                      CTLTYPE_STRUCT,
                      "hashstat", SYSCTL_DESCR("kernel hash statistics"),
                      hashstat_sysctl, 0, NULL, 0,
                      CTL_KERN, CTL_CREATE, CTL_EOL);
}

You are viewing proxied material from ftp.icm.edu.pl. The copyright of proxied material belongs to its original authors. Any comments or complaints in relation to proxied material should be directed to the original authors of the content concerned. Please see the disclaimer for more details.