1 /* $OpenBSD: alloc.c,v 1.13 2018/12/16 08:31:50 otto 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 * NEEDS_HEAP_H needs to #include "heap.h" to declare things 82 * needed by HEAP_LIMIT and/or HEAP_START. 83 * 84 * NEEDS_HEAP_INIT needs to invoke heap_init() to initialize 85 * heap boundaries. 86 * 87 * DEBUG enable debugging sanity checks. 88 */ 89 90 #include <sys/param.h> 91 92 /* 93 * Each block actually has ALIGN(unsigned) + ALIGN(size) bytes allocated 94 * to it, as follows: 95 * 96 * 0 ... (sizeof(unsigned) - 1) 97 * allocated or unallocated: holds size of user-data part of block. 98 * 99 * sizeof(unsigned) ... (ALIGN(sizeof(unsigned)) - 1) 100 * allocated: unused 101 * unallocated: depends on packing of struct fl 102 * 103 * ALIGN(sizeof(unsigned)) ... (ALIGN(sizeof(unsigned)) + ALIGN(data size) - 1) 104 * allocated: user data 105 * unallocated: depends on packing of struct fl 106 * 107 * 'next' is only used when the block is unallocated (i.e. on the free list). 108 * However, note that ALIGN(sizeof(unsigned)) + ALIGN(data size) must 109 * be at least 'sizeof(struct fl)', so that blocks can be used as structures 110 * when on the free list. 111 */ 112 113 #include "stand.h" 114 115 struct fl { 116 unsigned size; 117 struct fl *next; 118 } *freelist = NULL; 119 120 #ifdef NEEDS_HEAP_H 121 #include "heap.h" 122 #endif 123 #ifndef NEEDS_HEAP_INIT 124 #ifdef HEAP_START 125 static char *top = (char *)HEAP_START; 126 #else 127 extern char end[]; 128 static char *top = end; 129 #endif 130 #endif 131 132 void * 133 alloc(unsigned int size) 134 { 135 struct fl **f = &freelist, **bestf = NULL; 136 #ifndef ALLOC_FIRST_FIT 137 unsigned bestsize = 0xffffffff; /* greater than any real size */ 138 #endif 139 char *help; 140 int failed; 141 142 #ifdef NEEDS_HEAP_INIT 143 heap_init(); 144 #endif 145 146 #ifdef ALLOC_TRACE 147 printf("alloc(%u)", size); 148 #endif 149 150 #ifdef ALLOC_FIRST_FIT 151 while (*f != NULL && (*f)->size < size) 152 f = &((*f)->next); 153 bestf = f; 154 failed = (*bestf == NULL); 155 #else 156 /* scan freelist */ 157 while (*f) { 158 if ((*f)->size >= size) { 159 if ((*f)->size == size) /* exact match */ 160 goto found; 161 162 if ((*f)->size < bestsize) { 163 /* keep best fit */ 164 bestf = f; 165 bestsize = (*f)->size; 166 } 167 } 168 f = &((*f)->next); 169 } 170 171 /* no match in freelist if bestsize unchanged */ 172 failed = (bestsize == 0xffffffff || bestsize >= size * 2); 173 #endif 174 175 if (failed) { /* nothing found */ 176 /* 177 * allocate from heap, keep chunk len in 178 * first word 179 */ 180 help = top; 181 182 /* make _sure_ the region can hold a struct fl. */ 183 if (size < ALIGN(sizeof (struct fl *))) 184 size = ALIGN(sizeof (struct fl *)); 185 top += ALIGN(sizeof(unsigned)) + ALIGN(size); 186 #ifdef HEAP_LIMIT 187 if (top > (char *)HEAP_LIMIT) 188 panic("heap full (0x%lx+%u)", help, size); 189 #endif 190 *(unsigned *)help = ALIGN(size); 191 #ifdef ALLOC_TRACE 192 printf("=%p\n", help + ALIGN(sizeof(unsigned))); 193 #endif 194 return(help + ALIGN(sizeof(unsigned))); 195 } 196 197 /* we take the best fit */ 198 f = bestf; 199 200 #ifndef ALLOC_FIRST_FIT 201 found: 202 #endif 203 /* remove from freelist */ 204 help = (char *)*f; 205 *f = (*f)->next; 206 #ifdef ALLOC_TRACE 207 printf("=%p (origsize %u)\n", help + ALIGN(sizeof(unsigned)), 208 *(unsigned *)help); 209 #endif 210 return(help + ALIGN(sizeof(unsigned))); 211 } 212 213 void 214 free(void *ptr, unsigned int size) 215 { 216 struct fl *f; 217 218 if (ptr == NULL) 219 return; 220 221 f = (struct fl *)((char *)ptr - ALIGN(sizeof(unsigned))); 222 223 #ifdef ALLOC_TRACE 224 printf("free(%p, %u) (origsize %u)\n", ptr, size, f->size); 225 #endif 226 #ifdef DEBUG 227 if (size > f->size) 228 printf("free %u bytes @%p, should be <=%u\n", 229 size, ptr, f->size); 230 #ifdef HEAP_START 231 if (ptr < (void *)HEAP_START) 232 #else 233 if (ptr < (void *)end) 234 #endif 235 printf("free: %lx before start of heap.\n", (u_long)ptr); 236 237 #ifdef HEAP_LIMIT 238 if (ptr > (void *)HEAP_LIMIT) 239 printf("free: %lx beyond end of heap.\n", (u_long)ptr); 240 #endif 241 #endif /* DEBUG */ 242 /* put into freelist */ 243 f->next = freelist; 244 freelist = f; 245 } 246