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 /*
28 * zmalloc - use mmap(2) to allocate memory from /dev/zero.
29 * zfree - use munmap(2) to unmap (free) memory.
30 *
31 * These functions should be better than malloc(3) for large memory allocation.
32 */
33
34 #include <stdio.h>
35 #include <stdlib.h>
36 #include <fcntl.h>
37 #include <unistd.h>
38 #include <sys/types.h>
39 #include <sys/mman.h>
40 #include <sys/stat.h>
41
42 #include <zmalloc.h>
43
44 /*
45 * a utility structure to keep track of the (possibly) multiple mmaps
46 * that we have done...
47 */
48 struct buffer_map {
49 struct buffer_map *bm_next;
50 char *bm_buffer;
51 int bm_size;
52 };
53
54 static void *bm_empty = (void *) ""; /* special buffer */
55 static struct buffer_map *bm_list; /* NULL by default */
56
57 static struct buffer_map *
insert_bm(char * buf,size_t size)58 insert_bm(char *buf, size_t size)
59 {
60 struct buffer_map *bm;
61
62 bm = (struct buffer_map *)malloc(sizeof (struct buffer_map));
63 bm->bm_buffer = buf;
64 bm->bm_size = size;
65 bm->bm_next = bm_list;
66
67 bm_list = bm;
68
69 return (bm_list);
70 }
71
72 static size_t
delete_bm(char * buf)73 delete_bm(char *buf)
74 {
75 size_t size;
76 register struct buffer_map *p_curr;
77 register struct buffer_map *p_prev;
78
79 p_prev = NULL;
80 p_curr = bm_list;
81 while (p_curr != NULL) {
82 if (p_curr->bm_buffer == buf) {
83 if (p_prev == NULL)
84 bm_list = p_curr->bm_next;
85 else
86 p_prev->bm_next = p_curr->bm_next;
87 size = p_curr->bm_size;
88 free(p_curr);
89 return (size);
90 }
91
92 p_prev = p_curr;
93 p_curr = p_curr->bm_next;
94 }
95 return (0);
96 }
97
98 void *
zmalloc(size_t size)99 zmalloc(size_t size)
100 {
101 int fd;
102 caddr_t mbuf;
103
104 /* XXX - Special case: never allocate 0 bytes, use a special buffer */
105 if (size == 0)
106 return ((void *)NULL); /* return (bm_empty); */
107
108 if ((fd = open("/dev/zero", O_RDWR)) < 0) {
109 perror("/dev/zero");
110 return ((void *) NULL);
111 }
112
113 mbuf = mmap(0, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
114 (void) close(fd);
115
116 if (mbuf == (caddr_t)-1) {
117 perror("zmalloc: mmap");
118 return ((void *) NULL);
119 }
120
121 (void) insert_bm(mbuf, size);
122
123 return ((void *) mbuf);
124 }
125
126 void
zfree(void * mbuf)127 zfree(void* mbuf)
128 {
129 size_t size;
130
131 if (mbuf == bm_empty)
132 return;
133
134 if (mbuf != NULL) {
135 if (size = delete_bm((caddr_t)mbuf)) {
136 if (munmap((char *)mbuf, size) < 0)
137 perror("zfree: munmap");
138 }
139 }
140 }
141