alloc.c revision 1.19
1 /* $NetBSD: alloc.c,v 1.19 2005/02/26 22:58:56 perry 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 (at) 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 * ALLOC_TRACE enable tracing of allocations/deallocations 107 108 * ALLOC_FIRST_FIT use a first-fit allocation algorithm, rather than 109 * the default best-fit algorithm. 110 * 111 * HEAP_LIMIT heap limit address (defaults to "no limit"). 112 * 113 * HEAP_START start address of heap (defaults to '&end'). 114 * 115 * DEBUG enable debugging sanity checks. 116 */ 117 118 #include <sys/param.h> 119 #include "stand.h" 120 121 /* 122 * Each block actually has ALIGN(unsigned) + ALIGN(size) bytes allocated 123 * to it, as follows: 124 * 125 * 0 ... (sizeof(unsigned) - 1) 126 * allocated or unallocated: holds size of user-data part of block. 127 * 128 * sizeof(unsigned) ... (ALIGN(sizeof(unsigned)) - 1) 129 * allocated: unused 130 * unallocated: depends on packing of struct fl 131 * 132 * ALIGN(sizeof(unsigned)) ... (ALIGN(sizeof(unsigned)) + ALIGN(data size) - 1) 133 * allocated: user data 134 * unallocated: depends on packing of struct fl 135 * 136 * 'next' is only used when the block is unallocated (i.e. on the free list). 137 * However, note that ALIGN(sizeof(unsigned)) + ALIGN(data size) must 138 * be at least 'sizeof(struct fl)', so that blocks can be used as structures 139 * when on the free list. 140 */ 141 struct fl { 142 unsigned size; 143 struct fl *next; 144 } *freelist; 145 146 #ifdef HEAP_VARIABLE 147 static char *top, *heapstart, *heaplimit; 148 void 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 void * 164 alloc(u_int size) 165 { 166 struct fl **f = &freelist, **bestf = NULL; 167 #ifndef ALLOC_FIRST_FIT 168 unsigned bestsize = 0xffffffff; /* greater than any real size */ 169 #endif 170 char *help; 171 int failed; 172 173 #ifdef ALLOC_TRACE 174 printf("alloc(%u)", size); 175 #endif 176 177 #ifdef ALLOC_FIRST_FIT 178 while (*f != (struct fl *)0 && (*f)->size < size) 179 f = &((*f)->next); 180 bestf = f; 181 failed = (*bestf == (struct fl *)0); 182 #else 183 /* scan freelist */ 184 while (*f) { 185 if ((*f)->size >= size) { 186 if ((*f)->size == size) /* exact match */ 187 goto found; 188 189 if ((*f)->size < bestsize) { 190 /* keep best fit */ 191 bestf = f; 192 bestsize = (*f)->size; 193 } 194 } 195 f = &((*f)->next); 196 } 197 198 /* no match in freelist if bestsize unchanged */ 199 failed = (bestsize == 0xffffffff); 200 #endif 201 202 if (failed) { /* nothing found */ 203 /* 204 * allocate from heap, keep chunk len in 205 * first word 206 */ 207 help = top; 208 209 /* make _sure_ the region can hold a struct fl. */ 210 if (size < ALIGN(sizeof (struct fl *))) 211 size = ALIGN(sizeof (struct fl *)); 212 top += ALIGN(sizeof(unsigned)) + ALIGN(size); 213 #ifdef HEAP_LIMIT 214 if (top > (char*)HEAP_LIMIT) 215 panic("heap full (0x%lx+%u)", help, size); 216 #endif 217 *(unsigned *)(void *)help = (unsigned)ALIGN(size); 218 #ifdef ALLOC_TRACE 219 printf("=%lx\n", (u_long)help + ALIGN(sizeof(unsigned))); 220 #endif 221 return(help + ALIGN(sizeof(unsigned))); 222 } 223 224 /* we take the best fit */ 225 f = bestf; 226 227 #ifndef ALLOC_FIRST_FIT 228 found: 229 #endif 230 /* remove from freelist */ 231 help = (char *)(void *)*f; 232 *f = (*f)->next; 233 #ifdef ALLOC_TRACE 234 printf("=%lx (origsize %u)\n", (u_long)help + ALIGN(sizeof(unsigned)), 235 *(unsigned *)help); 236 #endif 237 return(help + ALIGN(sizeof(unsigned))); 238 } 239 240 void 241 /*ARGSUSED*/ 242 free(void *ptr, u_int size) 243 { 244 struct fl *f = 245 (struct fl *)(void *)((char*)(void *)ptr - ALIGN(sizeof(unsigned))); 246 #ifdef ALLOC_TRACE 247 printf("free(%lx, %u) (origsize %u)\n", (u_long)ptr, size, f->size); 248 #endif 249 #ifdef DEBUG 250 if (size > f->size) 251 printf("free %u bytes @%lx, should be <=%u\n", 252 size, (u_long)ptr, f->size); 253 254 if (ptr < (void *)HEAP_START) 255 printf("free: %lx before start of heap.\n", (u_long)ptr); 256 257 #ifdef HEAP_LIMIT 258 if (ptr > (void *)HEAP_LIMIT) 259 printf("free: %lx beyond end of heap.\n", (u_long)ptr); 260 #endif 261 #endif /* DEBUG */ 262 /* put into freelist */ 263 f->next = freelist; 264 freelist = f; 265 } 266
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