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kern_uidinfo.c revision 1.3.6.1 
      1 /*	$NetBSD: kern_uidinfo.c,v 1.3.6.1 2009/03/26 17:17:31 snj 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 1.3.6.1 2009/03/26 17:17:31 snj 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 	KASSERT(nsb >= 0);
    142 	return 1;
    143 }
    144