1 /* $OpenBSD: alloc.c,v 1.9 2003/08/11 06:23:09 deraadt Exp $ */
2 /* $NetBSD: alloc.c,v 1.6 1997/02/04 18:36:33 thorpej Exp $ */
3
4 /*
5 * Copyright (c) 1997 Christopher G. Demetriou. All rights reserved.
6 * Copyright (c) 1996
7 * Matthias Drochner. All rights reserved.
8 * Copyright (c) 1993
9 * The Regents of the University of California. All rights reserved.
10 *
11 * This code is derived from software contributed to Berkeley by
12 * The Mach Operating System project at Carnegie-Mellon University.
13 *
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions
16 * are met:
17 * 1. Redistributions of source code must retain the above copyright
18 * notice, this list of conditions and the following disclaimer.
19 * 2. Redistributions in binary form must reproduce the above copyright
20 * notice, this list of conditions and the following disclaimer in the
21 * documentation and/or other materials provided with the distribution.
22 * 3. Neither the name of the University nor the names of its contributors
23 * may be used to endorse or promote products derived from this software
24 * without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * SUCH DAMAGE.
37 *
38 * @(#)alloc.c 8.1 (Berkeley) 6/11/93
39 *
40 *
41 * Copyright (c) 1989, 1990, 1991 Carnegie Mellon University
42 * All Rights Reserved.
43 *
44 * Author: Alessandro Forin
45 *
46 * Permission to use, copy, modify and distribute this software and its
47 * documentation is hereby granted, provided that both the copyright
48 * notice and this permission notice appear in all copies of the
49 * software, derivative works or modified versions, and any portions
50 * thereof, and that both notices appear in supporting documentation.
51 *
52 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
53 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
54 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
55 *
56 * Carnegie Mellon requests users of this software to return to
57 *
58 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
59 * School of Computer Science
60 * Carnegie Mellon University
61 * Pittsburgh PA 15213-3890
62 *
63 * any improvements or extensions that they make and grant Carnegie the
64 * rights to redistribute these changes.
65 */
66
67 /*
68 * Dynamic memory allocator.
69 *
70 * Compile options:
71 *
72 * ALLOC_TRACE enable tracing of allocations/deallocations
73 *
74 * ALLOC_FIRST_FIT use a first-fit allocation algorithm, rather than
75 * the default best-fit algorithm.
76 *
77 * HEAP_LIMIT heap limit address (defaults to "no limit").
78 *
79 * HEAP_START start address of heap (defaults to '&end').
80 *
81 * DEBUG enable debugging sanity checks.
82 */
83
84 #include <sys/param.h>
85
86 /*
87 * Each block actually has ALIGN(unsigned) + ALIGN(size) bytes allocated
88 * to it, as follows:
89 *
90 * 0 ... (sizeof(unsigned) - 1)
91 * allocated or unallocated: holds size of user-data part of block.
92 *
93 * sizeof(unsigned) ... (ALIGN(sizeof(unsigned)) - 1)
94 * allocated: unused
95 * unallocated: depends on packing of struct fl
96 *
97 * ALIGN(sizeof(unsigned)) ... (ALIGN(sizeof(unsigned)) + ALIGN(data size) - 1)
98 * allocated: user data
99 * unallocated: depends on packing of struct fl
100 *
101 * 'next' is only used when the block is unallocated (i.e. on the free list).
102 * However, note that ALIGN(sizeof(unsigned)) + ALIGN(data size) must
103 * be at least 'sizeof(struct fl)', so that blocks can be used as structures
104 * when on the free list.
105 */
106
107 #include "stand.h"
108
109 struct fl {
110 unsigned size;
111 struct fl *next;
112 } *freelist = (struct fl *)0;
113
114 #ifdef HEAP_START
115 static char *top = (char *)HEAP_START;
116 #else
117 extern char end[];
118 static char *top = end;
119 #endif
120
121 void *
122 alloc(unsigned int size)
123 {
124 struct fl **f = &freelist, **bestf = NULL;
125 #ifndef ALLOC_FIRST_FIT
126 unsigned bestsize = 0xffffffff; /* greater than any real size */
127 #endif
128 char *help;
129 int failed;
130
131 #ifdef ALLOC_TRACE
132 printf("alloc(%u)", size);
133 #endif
134
135 #ifdef ALLOC_FIRST_FIT
136 while (*f != (struct fl *)0 && (*f)->size < size)
137 f = &((*f)->next);
138 bestf = f;
139 failed = (*bestf == (struct fl *)0);
140 #else
141 /* scan freelist */
142 while (*f) {
143 if ((*f)->size >= size) {
144 if ((*f)->size == size) /* exact match */
145 goto found;
146
147 if ((*f)->size < bestsize) {
148 /* keep best fit */
149 bestf = f;
150 bestsize = (*f)->size;
151 }
152 }
153 f = &((*f)->next);
154 }
155
156 /* no match in freelist if bestsize unchanged */
157 failed = (bestsize == 0xffffffff);
158 #endif
159
160 if (failed) { /* nothing found */
161 /*
162 * allocate from heap, keep chunk len in
163 * first word
164 */
165 help = top;
166
167 /* make _sure_ the region can hold a struct fl. */
168 if (size < ALIGN(sizeof (struct fl *)))
169 size = ALIGN(sizeof (struct fl *));
170 top += ALIGN(sizeof(unsigned)) + ALIGN(size);
171 #ifdef HEAP_LIMIT
172 if (top > (char *)HEAP_LIMIT)
173 panic("heap full (0x%lx+%u)", help, size);
174 #endif
175 *(unsigned *)help = ALIGN(size);
176 #ifdef ALLOC_TRACE
177 printf("=%p\n", help + ALIGN(sizeof(unsigned)));
178 #endif
179 return(help + ALIGN(sizeof(unsigned)));
180 }
181
182 /* we take the best fit */
183 f = bestf;
184
185 #ifndef ALLOC_FIRST_FIT
186 found:
187 #endif
188 /* remove from freelist */
189 help = (char *)*f;
190 *f = (*f)->next;
191 #ifdef ALLOC_TRACE
192 printf("=%p (origsize %u)\n", help + ALIGN(sizeof(unsigned)),
193 *(unsigned *)help);
194 #endif
195 return(help + ALIGN(sizeof(unsigned)));
196 }
197
198 void
199 free(void *ptr, unsigned int size)
200 {
201 struct fl *f = (struct fl *)((char *)ptr -
202 ALIGN(sizeof(unsigned)));
203
204 #ifdef ALLOC_TRACE
205 printf("free(%p, %u) (origsize %u)\n", ptr, size, f->size);
206 #endif
207 #ifdef DEBUG
208 if (size > f->size)
209 printf("free %u bytes @%p, should be <=%u\n",
210 size, ptr, f->size);
211 #ifdef HEAP_START
212 if (ptr < (void *)HEAP_START)
213 #else
214 if (ptr < (void *)end)
215 #endif
216 printf("free: %lx before start of heap.\n", (u_long)ptr);
217
218 #ifdef HEAP_LIMIT
219 if (ptr > (void *)HEAP_LIMIT)
220 printf("free: %lx beyond end of heap.\n", (u_long)ptr);
221 #endif
222 #endif /* DEBUG */
223 /* put into freelist */
224 f->next = freelist;
225 freelist = f;
226 }