alloc.c revision 1.8 1 /* $NetBSD: alloc.c,v 1.8 1997/06/13 14:28:52 drochner Exp $ */
2
3 /*
4 * Copyright (c) 1997 Christopher G. Demetriou. All rights reserved.
5 * Copyright (c) 1996
6 * Matthias Drochner. All rights reserved.
7 * Copyright (c) 1993
8 * The Regents of the University of California. All rights reserved.
9 *
10 * This code is derived from software contributed to Berkeley by
11 * The Mach Operating System project at Carnegie-Mellon University.
12 *
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
15 * are met:
16 * 1. Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 * 2. Redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution.
21 * 3. All advertising materials mentioning features or use of this software
22 * must display the following acknowledgement:
23 * This product includes software developed by the University of
24 * California, Berkeley and its contributors.
25 * 4. Neither the name of the University nor the names of its contributors
26 * may be used to endorse or promote products derived from this software
27 * without specific prior written permission.
28 *
29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
39 * SUCH DAMAGE.
40 *
41 * @(#)alloc.c 8.1 (Berkeley) 6/11/93
42 *
43 *
44 * Copyright (c) 1989, 1990, 1991 Carnegie Mellon University
45 * All Rights Reserved.
46 *
47 * Author: Alessandro Forin
48 *
49 * Permission to use, copy, modify and distribute this software and its
50 * documentation is hereby granted, provided that both the copyright
51 * notice and this permission notice appear in all copies of the
52 * software, derivative works or modified versions, and any portions
53 * thereof, and that both notices appear in supporting documentation.
54 *
55 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
56 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
57 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
58 *
59 * Carnegie Mellon requests users of this software to return to
60 *
61 * Software Distribution Coordinator or Software.Distribution (at) CS.CMU.EDU
62 * School of Computer Science
63 * Carnegie Mellon University
64 * Pittsburgh PA 15213-3890
65 *
66 * any improvements or extensions that they make and grant Carnegie the
67 * rights to redistribute these changes.
68 */
69
70 /*
71 * Dynamic memory allocator.
72 *
73 * Compile options:
74 *
75 * ALLOC_TRACE enable tracing of allocations/deallocations
76
77 * ALLOC_FIRST_FIT use a first-fit allocation algorithm, rather than
78 * the default best-fit algorithm.
79 *
80 * HEAP_LIMIT heap limit address (defaults to "no limit").
81 *
82 * HEAP_START start address of heap (defaults to '&end').
83 *
84 * DEBUG enable debugging sanity checks.
85 */
86
87 #include <sys/param.h>
88 #include "stand.h"
89
90 /*
91 * Each block actually has ALIGN(unsigned) + ALIGN(size) bytes allocated
92 * to it, as follows:
93 *
94 * 0 ... (sizeof(unsigned) - 1)
95 * allocated or unallocated: holds size of user-data part of block.
96 *
97 * sizeof(unsigned) ... (ALIGN(sizeof(unsigned)) - 1)
98 * allocated: unused
99 * unallocated: depends on packing of struct fl
100 *
101 * ALIGN(sizeof(unsigned)) ... (ALIGN(sizeof(unsigned)) + ALIGN(data size) - 1)
102 * allocated: user data
103 * unallocated: depends on packing of struct fl
104 *
105 * 'next' is only used when the block is unallocated (i.e. on the free list).
106 * However, note that ALIGN(sizeof(unsigned)) + ALIGN(data size) must
107 * be at least 'sizeof(struct fl)', so that blocks can be used as structures
108 * when on the free list.
109 */
110 struct fl {
111 unsigned size;
112 struct fl *next;
113 } *freelist = (struct fl *)0;
114
115 #ifdef HEAP_START
116 static char *top = (char*)HEAP_START;
117 #else
118 extern char end[];
119 static char *top = end;
120 #endif
121
122 void *
123 alloc(size)
124 unsigned size;
125 {
126 register struct fl **f = &freelist, **bestf = NULL;
127 unsigned bestsize = 0xffffffff; /* greater than any real size */
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("=%x\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 found:
186 /* remove from freelist */
187 help = (char*)*f;
188 *f = (*f)->next;
189 #ifdef ALLOC_TRACE
190 printf("=%lx (origsize %u)\n", help + ALIGN(sizeof(unsigned)),
191 *(unsigned *)help);
192 #endif
193 return(help + ALIGN(sizeof(unsigned)));
194 }
195
196 void
197 free(ptr, size)
198 void *ptr;
199 unsigned size; /* only for consistence check */
200 {
201 register struct fl *f =
202 (struct fl *)((char*)ptr - ALIGN(sizeof(unsigned)));
203 #ifdef ALLOC_TRACE
204 printf("free(%lx, %u) (origsize %u)\n", ptr, size, f->size);
205 #endif
206 #ifdef DEBUG
207 if (size > f->size)
208 printf("free %u bytes @%lx, should be <=%u\n",
209 size, ptr, f->size);
210 #ifdef HEAP_START
211 if (ptr < (void *)HEAP_START)
212 #else
213 if (ptr < (void *)end[])
214 #endif
215 printf("free: %lx before start of heap.\n", (u_long)ptr);
216
217 #ifdef HEAP_LIMIT
218 if (ptr > (void *)HEAP_LIMIT)
219 printf("free: %lx beyond end of heap.\n", (u_long)ptr);
220 #endif
221 #endif /* DEBUG */
222 /* put into freelist */
223 f->next = freelist;
224 freelist = f;
225 }
226