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 } 227