1 /* $OpenBSD: alloc.c,v 1.13 2018/12/16 08:31:50 otto 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 * NEEDS_HEAP_H needs to #include "heap.h" to declare things
82 * needed by HEAP_LIMIT and/or HEAP_START.
83 *
84 * NEEDS_HEAP_INIT needs to invoke heap_init() to initialize
85 * heap boundaries.
86 *
87 * DEBUG enable debugging sanity checks.
88 */
89
90 #include <sys/param.h>
91
92 /*
93 * Each block actually has ALIGN(unsigned) + ALIGN(size) bytes allocated
94 * to it, as follows:
95 *
96 * 0 ... (sizeof(unsigned) - 1)
97 * allocated or unallocated: holds size of user-data part of block.
98 *
99 * sizeof(unsigned) ... (ALIGN(sizeof(unsigned)) - 1)
100 * allocated: unused
101 * unallocated: depends on packing of struct fl
102 *
103 * ALIGN(sizeof(unsigned)) ... (ALIGN(sizeof(unsigned)) + ALIGN(data size) - 1)
104 * allocated: user data
105 * unallocated: depends on packing of struct fl
106 *
107 * 'next' is only used when the block is unallocated (i.e. on the free list).
108 * However, note that ALIGN(sizeof(unsigned)) + ALIGN(data size) must
109 * be at least 'sizeof(struct fl)', so that blocks can be used as structures
110 * when on the free list.
111 */
112
113 #include "stand.h"
114
115 struct fl {
116 unsigned size;
117 struct fl *next;
118 } *freelist = NULL;
119
120 #ifdef NEEDS_HEAP_H
121 #include "heap.h"
122 #endif
123 #ifndef NEEDS_HEAP_INIT
124 #ifdef HEAP_START
125 static char *top = (char *)HEAP_START;
126 #else
127 extern char end[];
128 static char *top = end;
129 #endif
130 #endif
131
132 void *
alloc(unsigned int size)133 alloc(unsigned int size)
134 {
135 struct fl **f = &freelist, **bestf = NULL;
136 #ifndef ALLOC_FIRST_FIT
137 unsigned bestsize = 0xffffffff; /* greater than any real size */
138 #endif
139 char *help;
140 int failed;
141
142 #ifdef NEEDS_HEAP_INIT
143 heap_init();
144 #endif
145
146 #ifdef ALLOC_TRACE
147 printf("alloc(%u)", size);
148 #endif
149
150 #ifdef ALLOC_FIRST_FIT
151 while (*f != NULL && (*f)->size < size)
152 f = &((*f)->next);
153 bestf = f;
154 failed = (*bestf == NULL);
155 #else
156 /* scan freelist */
157 while (*f) {
158 if ((*f)->size >= size) {
159 if ((*f)->size == size) /* exact match */
160 goto found;
161
162 if ((*f)->size < bestsize) {
163 /* keep best fit */
164 bestf = f;
165 bestsize = (*f)->size;
166 }
167 }
168 f = &((*f)->next);
169 }
170
171 /* no match in freelist if bestsize unchanged */
172 failed = (bestsize == 0xffffffff || bestsize >= size * 2);
173 #endif
174
175 if (failed) { /* nothing found */
176 /*
177 * allocate from heap, keep chunk len in
178 * first word
179 */
180 help = top;
181
182 /* make _sure_ the region can hold a struct fl. */
183 if (size < ALIGN(sizeof (struct fl *)))
184 size = ALIGN(sizeof (struct fl *));
185 top += ALIGN(sizeof(unsigned)) + ALIGN(size);
186 #ifdef HEAP_LIMIT
187 if (top > (char *)HEAP_LIMIT)
188 panic("heap full (0x%lx+%u)", help, size);
189 #endif
190 *(unsigned *)help = ALIGN(size);
191 #ifdef ALLOC_TRACE
192 printf("=%p\n", help + ALIGN(sizeof(unsigned)));
193 #endif
194 return(help + ALIGN(sizeof(unsigned)));
195 }
196
197 /* we take the best fit */
198 f = bestf;
199
200 #ifndef ALLOC_FIRST_FIT
201 found:
202 #endif
203 /* remove from freelist */
204 help = (char *)*f;
205 *f = (*f)->next;
206 #ifdef ALLOC_TRACE
207 printf("=%p (origsize %u)\n", help + ALIGN(sizeof(unsigned)),
208 *(unsigned *)help);
209 #endif
210 return(help + ALIGN(sizeof(unsigned)));
211 }
212
213 void
free(void * ptr,unsigned int size)214 free(void *ptr, unsigned int size)
215 {
216 struct fl *f;
217
218 if (ptr == NULL)
219 return;
220
221 f = (struct fl *)((char *)ptr - ALIGN(sizeof(unsigned)));
222
223 #ifdef ALLOC_TRACE
224 printf("free(%p, %u) (origsize %u)\n", ptr, size, f->size);
225 #endif
226 #ifdef DEBUG
227 if (size > f->size)
228 printf("free %u bytes @%p, should be <=%u\n",
229 size, ptr, f->size);
230 #ifdef HEAP_START
231 if (ptr < (void *)HEAP_START)
232 #else
233 if (ptr < (void *)end)
234 #endif
235 printf("free: %lx before start of heap.\n", (u_long)ptr);
236
237 #ifdef HEAP_LIMIT
238 if (ptr > (void *)HEAP_LIMIT)
239 printf("free: %lx beyond end of heap.\n", (u_long)ptr);
240 #endif
241 #endif /* DEBUG */
242 /* put into freelist */
243 f->next = freelist;
244 freelist = f;
245 }
246