sys/kern/kern_uidinfo.c

   1 /*      $NetBSD: kern_uidinfo.c,v 1.4 2009/01/11 02:45:52 christos Exp $        */
   2
   3 /*-
   4  * Copyright (c) 1982, 1986, 1991, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  * (c) UNIX System Laboratories, Inc.
   7  * All or some portions of this file are derived from material licensed
   8  * to the University of California by American Telephone and Telegraph
   9  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
  10  * the permission of UNIX System Laboratories, Inc.
  11  *
  12  * Redistribution and use in source and binary forms, with or without
  13  * modification, are permitted provided that the following conditions
  14  * are met:
  15  * 1. Redistributions of source code must retain the above copyright
  16  *    notice, this list of conditions and the following disclaimer.
  17  * 2. Redistributions in binary form must reproduce the above copyright
  18  *    notice, this list of conditions and the following disclaimer in the
  19  *    documentation and/or other materials provided with the distribution.
  20  * 3. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  */
  36
  37 #include <sys/cdefs.h>
  38 __KERNEL_RCSID(0, "$NetBSD: kern_uidinfo.c,v 1.4 2009/01/11 02:45:52 christos Exp $");
  39
  40 #include <sys/param.h>
  41 #include <sys/systm.h>
  42 #include <sys/kmem.h>
  43 #include <sys/proc.h>
  44 #include <sys/atomic.h>
  45 #include <sys/uidinfo.h>
  46 #include <sys/cpu.h>
  47
  48 static SLIST_HEAD(uihashhead, uidinfo) *uihashtbl;
  49 static u_long           uihash;
  50
  51 #define UIHASH(uid)     (&uihashtbl[(uid) & uihash])
  52
  53 void
  54 uid_init(void)
  55 {
  56
  57         /*
  58          * In case of MP system, SLIST_FOREACH would force a cache line
  59          * write-back for every modified 'uidinfo', thus we try to keep the
  60          * lists short.
  61          */
  62         const u_int uihash_sz = (maxcpus > 1 ? 1024 : 64);
  63
  64         uihashtbl = hashinit(uihash_sz, HASH_SLIST, true, &uihash);
  65
  66         /*
  67          * Ensure that uid 0 is always in the user hash table, as
  68          * sbreserve() expects it available from interrupt context.
  69          */
  70         (void)uid_find(0);
  71 }
  72
  73 struct uidinfo *
  74 uid_find(uid_t uid)
  75 {
  76         struct uidinfo *uip, *uip_first, *newuip;
  77         struct uihashhead *uipp;
  78
  79         uipp = UIHASH(uid);
  80         newuip = NULL;
  81
  82         /*
  83          * To make insertion atomic, abstraction of SLIST will be violated.
  84          */
  85         uip_first = uipp->slh_first;
  86  again:
  87         SLIST_FOREACH(uip, uipp, ui_hash) {
  88                 if (uip->ui_uid != uid)
  89                         continue;
  90                 if (newuip != NULL)
  91                         kmem_free(newuip, sizeof(*newuip));
  92                 return uip;
  93         }
  94         if (newuip == NULL)
  95                 newuip = kmem_zalloc(sizeof(*newuip), KM_SLEEP);
  96         newuip->ui_uid = uid;
  97
  98         /*
  99          * If atomic insert is unsuccessful, another thread might be
 100          * allocated this 'uid', thus full re-check is needed.
 101          */
 102         newuip->ui_hash.sle_next = uip_first;
 103         membar_producer();
 104         uip = atomic_cas_ptr(&uipp->slh_first, uip_first, newuip);
 105         if (uip != uip_first) {
 106                 uip_first = uip;
 107                 goto again;
 108         }
 109
 110         return newuip;
 111 }
 112
 113 /*
 114  * Change the count associated with number of processes
 115  * a given user is using.
 116  */
 117 int
 118 chgproccnt(uid_t uid, int diff)
 119 {
 120         struct uidinfo *uip;
 121         long proccnt;
 122
 123         uip = uid_find(uid);
 124         proccnt = atomic_add_long_nv(&uip->ui_proccnt, diff);
 125         KASSERT(proccnt >= 0);
 126         return proccnt;
 127 }
 128
 129 int
 130 chgsbsize(struct uidinfo *uip, u_long *hiwat, u_long to, rlim_t xmax)
 131 {
 132         rlim_t nsb;
 133         const long diff = to - *hiwat;
 134
 135         nsb = (rlim_t)atomic_add_long_nv((long *)&uip->ui_sbsize, diff);
 136         if (diff > 0 && nsb > xmax) {
 137                 atomic_add_long((long *)&uip->ui_sbsize, -diff);
 138                 return 0;
 139         }
 140         *hiwat = to;
 141         return 1;
 142 }