1 /* $NetBSD: alloc.c,v 1.28 2019/03/31 20:08:45 christos Exp $ */
2
3 /*
4 * Copyright (c) 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * The Mach Operating System project at Carnegie-Mellon University.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 *
34 * @(#)alloc.c 8.1 (Berkeley) 6/11/93
35 *
36 *
37 * Copyright (c) 1997 Christopher G. Demetriou. All rights reserved.
38 * Copyright (c) 1996
39 * Matthias Drochner. All rights reserved.
40 *
41 * This code is derived from software contributed to Berkeley by
42 * The Mach Operating System project at Carnegie-Mellon University.
43 *
44 * Redistribution and use in source and binary forms, with or without
45 * modification, are permitted provided that the following conditions
46 * are met:
47 * 1. Redistributions of source code must retain the above copyright
48 * notice, this list of conditions and the following disclaimer.
49 * 2. Redistributions in binary form must reproduce the above copyright
50 * notice, this list of conditions and the following disclaimer in the
51 * documentation and/or other materials provided with the distribution.
52 * 3. All advertising materials mentioning features or use of this software
53 * must display the following acknowledgement:
54 * This product includes software developed by the University of
55 * California, Berkeley and its contributors.
56 * 4. Neither the name of the University nor the names of its contributors
57 * may be used to endorse or promote products derived from this software
58 * without specific prior written permission.
59 *
60 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
61 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
62 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
63 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
64 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
65 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
66 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
67 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
68 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
69 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
70 * SUCH DAMAGE.
71 *
72 * @(#)alloc.c 8.1 (Berkeley) 6/11/93
73 *
74 *
75 * Copyright (c) 1989, 1990, 1991 Carnegie Mellon University
76 * All Rights Reserved.
77 *
78 * Author: Alessandro Forin
79 *
80 * Permission to use, copy, modify and distribute this software and its
81 * documentation is hereby granted, provided that both the copyright
82 * notice and this permission notice appear in all copies of the
83 * software, derivative works or modified versions, and any portions
84 * thereof, and that both notices appear in supporting documentation.
85 *
86 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
87 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
88 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
89 *
90 * Carnegie Mellon requests users of this software to return to
91 *
92 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
93 * School of Computer Science
94 * Carnegie Mellon University
95 * Pittsburgh PA 15213-3890
96 *
97 * any improvements or extensions that they make and grant Carnegie the
98 * rights to redistribute these changes.
99 */
100
101 /*
102 * Dynamic memory allocator.
103 *
104 * Compile options:
105 *
106 * HEAP_LIMIT heap limit address (defaults to "no limit").
107 *
108 * HEAP_START start address of heap (defaults to '&end').
109 *
110 * DEBUG enable debugging sanity checks.
111 */
112
113 #include <sys/param.h>
114 #include "stand.h"
115
116 /*
117 * Each block actually has ALIGN(unsigned int) + ALIGN(size) bytes allocated
118 * to it, as follows:
119 *
120 * 0 ... (sizeof(unsigned int) - 1)
121 * allocated or unallocated: holds size of user-data part of block.
122 *
123 * sizeof(unsigned int) ... (ALIGN(sizeof(unsigned int)) - 1)
124 * allocated: unused
125 * unallocated: depends on packing of struct fl
126 *
127 * ALIGN(sizeof(unsigned int)) ...
128 * (ALIGN(sizeof(unsigned int)) + ALIGN(data size) - 1)
129 * allocated: user data
130 * unallocated: depends on packing of struct fl
131 *
132 * 'next' is only used when the block is unallocated (i.e. on the free list).
133 * However, note that ALIGN(sizeof(unsigned int)) + ALIGN(data size) must
134 * be at least 'sizeof(struct fl)', so that blocks can be used as structures
135 * when on the free list.
136 *
137 * When HEAP_LIMIT is defined and the heap limit is reached, alloc() panics.
138 * Otherwise, it never fails.
139 */
140 struct fl {
141 unsigned int size;
142 struct fl *next;
143 } *freelist;
144
145 #ifdef HEAP_VARIABLE
146 static char *top, *heapstart, *heaplimit;
147 void
setheap(void * start,void * limit)148 setheap(void *start, void *limit)
149 {
150 heapstart = top = start;
151 heaplimit = limit;
152 }
153 #define HEAP_START heapstart
154 #define HEAP_LIMIT heaplimit
155 #else /* !HEAP_VARIABLE */
156 #ifndef HEAP_START
157 extern char end[];
158 #define HEAP_START end
159 #endif
160 static char *top = (char *)HEAP_START;
161 #endif /* HEAP_VARIABLE */
162
163 __compactcall void *
alloc(size_t size)164 alloc(size_t size)
165 {
166 struct fl **f = &freelist, **bestf = NULL;
167 unsigned int bestsize = 0xffffffff; /* greater than any real size */
168 char *help;
169 int failed;
170
171 /* scan freelist */
172 while (*f) {
173 if ((size_t)(*f)->size >= size) {
174 if ((size_t)(*f)->size == size) /* exact match */
175 goto found;
176
177 if ((*f)->size < bestsize) {
178 /* keep best fit */
179 bestf = f;
180 bestsize = (*f)->size;
181 }
182 }
183 f = &((*f)->next);
184 }
185
186 /* no match in freelist if bestsize unchanged */
187 failed = (bestsize == 0xffffffff);
188
189 if (failed) { /* nothing found */
190 /*
191 * allocate from heap, keep chunk len in
192 * first word
193 */
194 help = top;
195
196 /* make _sure_ the region can hold a struct fl. */
197 if (size < ALIGN(sizeof (struct fl *)))
198 size = ALIGN(sizeof (struct fl *));
199 top += ALIGN(sizeof(unsigned int)) + ALIGN(size);
200 #ifdef HEAP_LIMIT
201 if (top > (char *)HEAP_LIMIT)
202 panic("heap full (%p+%zu)", help, size);
203 #endif
204 *(unsigned int *)(void *)help = (unsigned int)ALIGN(size);
205 return help + ALIGN(sizeof(unsigned int));
206 }
207
208 /* we take the best fit */
209 f = bestf;
210
211 found:
212 /* remove from freelist */
213 help = (char *)(void *)*f;
214 *f = (*f)->next;
215 return help + ALIGN(sizeof(unsigned int));
216 }
217
218 __compactcall void
219 /*ARGSUSED*/
dealloc(void * ptr,size_t size)220 dealloc(void *ptr, size_t size)
221 {
222 struct fl *f =
223 (struct fl *)(void *)((char *)(void *)ptr -
224 ALIGN(sizeof(unsigned int)));
225 #ifdef DEBUG
226 if (size > (size_t)f->size) {
227 printf("%s: %zu bytes @%p, should be <=%u\n", __func__,
228 size, ptr, f->size);
229 }
230
231 if (ptr < (void *)HEAP_START)
232 printf("%s: %p before start of heap.\n", __func__, ptr);
233
234 #ifdef HEAP_LIMIT
235 if (ptr > (void *)HEAP_LIMIT)
236 printf("%s: %p beyond end of heap.\n", __func__, ptr);
237 #endif
238 #endif /* DEBUG */
239 /* put into freelist */
240 f->next = freelist;
241 freelist = f;
242 }
243