Annotation of sys/lib/libsa/alloc.c, Revision 1.1.1.1
1.1 nbrk 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: }
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