1 /* $OpenBSD: alloc.c,v 1.5 1997/08/01 21:57:09 pefo 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. All advertising materials mentioning features or use of this software 23 * must display the following acknowledgement: 24 * This product includes software developed by the University of 25 * California, Berkeley and its contributors. 26 * 4. Neither the name of the University nor the names of its contributors 27 * may be used to endorse or promote products derived from this software 28 * without specific prior written permission. 29 * 30 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 31 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 32 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 33 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 34 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 35 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 36 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 37 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 38 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 39 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 40 * SUCH DAMAGE. 41 * 42 * @(#)alloc.c 8.1 (Berkeley) 6/11/93 43 * 44 * 45 * Copyright (c) 1989, 1990, 1991 Carnegie Mellon University 46 * All Rights Reserved. 47 * 48 * Author: Alessandro Forin 49 * 50 * Permission to use, copy, modify and distribute this software and its 51 * documentation is hereby granted, provided that both the copyright 52 * notice and this permission notice appear in all copies of the 53 * software, derivative works or modified versions, and any portions 54 * thereof, and that both notices appear in supporting documentation. 55 * 56 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 57 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR 58 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 59 * 60 * Carnegie Mellon requests users of this software to return to 61 * 62 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 63 * School of Computer Science 64 * Carnegie Mellon University 65 * Pittsburgh PA 15213-3890 66 * 67 * any improvements or extensions that they make and grant Carnegie the 68 * rights to redistribute these changes. 69 */ 70 71 /* 72 * Dynamic memory allocator. 73 * 74 * Compile options: 75 * 76 * ALLOC_TRACE enable tracing of allocations/deallocations 77 * 78 * ALLOC_FIRST_FIT use a first-fit allocation algorithm, rather than 79 * the default best-fit algorithm. 80 * 81 * HEAP_LIMIT heap limit address (defaults to "no limit"). 82 * 83 * HEAP_START start address of heap (defaults to '&end'). 84 * 85 * DEBUG enable debugging sanity checks. 86 */ 87 88 #include <sys/param.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 */ 110 111 #include "stand.h" 112 113 struct fl { 114 unsigned size; 115 struct fl *next; 116 } *freelist = (struct fl *)0; 117 118 #ifdef HEAP_START 119 static char *top = (char*)HEAP_START; 120 #else 121 extern char end[]; 122 static char *top = end; 123 #endif 124 125 void * 126 alloc(size) 127 unsigned size; 128 { 129 register struct fl **f = &freelist, **bestf = NULL; 130 #ifndef ALLOC_FIRST_FIT 131 unsigned bestsize = 0xffffffff; /* greater than any real size */ 132 #endif 133 char *help; 134 int failed; 135 136 #ifdef ALLOC_TRACE 137 printf("alloc(%u)", size); 138 #endif 139 140 #ifdef ALLOC_FIRST_FIT 141 while (*f != (struct fl *)0 && (*f)->size < size) 142 f = &((*f)->next); 143 bestf = f; 144 failed = (*bestf == (struct fl *)0); 145 #else 146 /* scan freelist */ 147 while (*f) { 148 if ((*f)->size >= size) { 149 if ((*f)->size == size) /* exact match */ 150 goto found; 151 152 if ((*f)->size < bestsize) { 153 /* keep best fit */ 154 bestf = f; 155 bestsize = (*f)->size; 156 } 157 } 158 f = &((*f)->next); 159 } 160 161 /* no match in freelist if bestsize unchanged */ 162 failed = (bestsize == 0xffffffff); 163 #endif 164 165 if (failed) { /* nothing found */ 166 /* 167 * allocate from heap, keep chunk len in 168 * first word 169 */ 170 help = top; 171 172 /* make _sure_ the region can hold a struct fl. */ 173 if (size < ALIGN(sizeof (struct fl *))) 174 size = ALIGN(sizeof (struct fl *)); 175 top += ALIGN(sizeof(unsigned)) + ALIGN(size); 176 #ifdef HEAP_LIMIT 177 if (top > (char*)HEAP_LIMIT) 178 panic("heap full (0x%lx+%u)", help, size); 179 #endif 180 *(unsigned *)help = ALIGN(size); 181 #ifdef ALLOC_TRACE 182 printf("=%p\n", help + ALIGN(sizeof(unsigned))); 183 #endif 184 return(help + ALIGN(sizeof(unsigned))); 185 } 186 187 /* we take the best fit */ 188 f = bestf; 189 190 #ifndef ALLOC_FIRST_FIT 191 found: 192 #endif 193 /* remove from freelist */ 194 help = (char*)*f; 195 *f = (*f)->next; 196 #ifdef ALLOC_TRACE 197 printf("=%p (origsize %u)\n", help + ALIGN(sizeof(unsigned)), 198 *(unsigned *)help); 199 #endif 200 return(help + ALIGN(sizeof(unsigned))); 201 } 202 203 void 204 free(ptr, size) 205 void *ptr; 206 unsigned size; /* only for consistence check */ 207 { 208 register struct fl *f = 209 (struct fl *)((char*)ptr - ALIGN(sizeof(unsigned))); 210 #ifdef ALLOC_TRACE 211 printf("free(%p, %u) (origsize %u)\n", ptr, size, f->size); 212 #endif 213 #ifdef DEBUG 214 if (size > f->size) 215 printf("free %u bytes @%p, should be <=%u\n", 216 size, ptr, f->size); 217 #ifdef HEAP_START 218 if (ptr < (void *)HEAP_START) 219 #else 220 if (ptr < (void *)end) 221 #endif 222 printf("free: %lx before start of heap.\n", (u_long)ptr); 223 224 #ifdef HEAP_LIMIT 225 if (ptr > (void *)HEAP_LIMIT) 226 printf("free: %lx beyond end of heap.\n", (u_long)ptr); 227 #endif 228 #endif /* DEBUG */ 229 /* put into freelist */ 230 f->next = freelist; 231 freelist = f; 232 } 233