1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License, Version 1.0 only
6 * (the "License"). You may not use this file except in compliance
7 * with the License.
8 *
9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10 * or http://www.opensolaris.org/os/licensing.
11 * See the License for the specific language governing permissions
12 * and limitations under the License.
13 *
14 * When distributing Covered Code, include this CDDL HEADER in each
15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16 * If applicable, add the following below this CDDL HEADER, with the
17 * fields enclosed by brackets "[]" replaced with your own identifying
18 * information: Portions Copyright [yyyy] [name of copyright owner]
19 *
20 * CDDL HEADER END
21 */
22 /*
23 * Copyright (c) 1991-2001 by Sun Microsystems, Inc.
24 * All rights reserved.
25 */
26
27 #pragma ident "%Z%%M% %I% %E% SMI"
28
29 /*
30 * zmalloc - use mmap(2) to allocate memory from /dev/zero.
31 * zfree - use munmap(2) to unmap (free) memory.
32 *
33 * These functions should be better than malloc(3) for large memory allocation.
34 */
35
36 #include <stdio.h>
37 #include <stdlib.h>
38 #include <fcntl.h>
39 #include <unistd.h>
40 #include <sys/types.h>
41 #include <sys/mman.h>
42 #include <sys/stat.h>
43
44 #include <zmalloc.h>
45
46 /*
47 * a utility structure to keep track of the (possibly) multiple mmaps
48 * that we have done...
49 */
50 struct buffer_map {
51 struct buffer_map *bm_next;
52 char *bm_buffer;
53 int bm_size;
54 };
55
56 static void *bm_empty = (void *) ""; /* special buffer */
57 static struct buffer_map *bm_list; /* NULL by default */
58
59 static struct buffer_map *
insert_bm(char * buf,size_t size)60 insert_bm(char *buf, size_t size)
61 {
62 struct buffer_map *bm;
63
64 bm = (struct buffer_map *)malloc(sizeof (struct buffer_map));
65 bm->bm_buffer = buf;
66 bm->bm_size = size;
67 bm->bm_next = bm_list;
68
69 bm_list = bm;
70
71 return (bm_list);
72 }
73
74 static size_t
delete_bm(char * buf)75 delete_bm(char *buf)
76 {
77 size_t size;
78 register struct buffer_map *p_curr;
79 register struct buffer_map *p_prev;
80
81 p_prev = NULL;
82 p_curr = bm_list;
83 while (p_curr != NULL) {
84 if (p_curr->bm_buffer == buf) {
85 if (p_prev == NULL)
86 bm_list = p_curr->bm_next;
87 else
88 p_prev->bm_next = p_curr->bm_next;
89 size = p_curr->bm_size;
90 free(p_curr);
91 return (size);
92 }
93
94 p_prev = p_curr;
95 p_curr = p_curr->bm_next;
96 }
97 return (0);
98 }
99
100 void *
zmalloc(size_t size)101 zmalloc(size_t size)
102 {
103 int fd;
104 caddr_t mbuf;
105
106 /* XXX - Special case: never allocate 0 bytes, use a special buffer */
107 if (size == 0)
108 return ((void *)NULL); /* return (bm_empty); */
109
110 if ((fd = open("/dev/zero", O_RDWR)) < 0) {
111 perror("/dev/zero");
112 return ((void *) NULL);
113 }
114
115 mbuf = mmap(0, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
116 (void) close(fd);
117
118 if (mbuf == (caddr_t)-1) {
119 perror("zmalloc: mmap");
120 return ((void *) NULL);
121 }
122
123 (void) insert_bm(mbuf, size);
124
125 return ((void *) mbuf);
126 }
127
128 void
zfree(void * mbuf)129 zfree(void* mbuf)
130 {
131 size_t size;
132
133 if (mbuf == bm_empty)
134 return;
135
136 if (mbuf != NULL) {
137 if (size = delete_bm((caddr_t)mbuf)) {
138 if (munmap((char *)mbuf, size) < 0)
139 perror("zfree: munmap");
140 }
141 }
142 }
143