1 /* $NetBSD: malloc.c,v 1.15 1998/11/15 17:13:51 christos Exp $ */ 2 3 /* 4 * Copyright (c) 1983, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. All advertising materials mentioning features or use of this software 16 * must display the following acknowledgement: 17 * This product includes software developed by the University of 18 * California, Berkeley and its contributors. 19 * 4. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 */ 35 36 #include <sys/cdefs.h> 37 #if defined(LIBC_SCCS) && !defined(lint) 38 #if 0 39 static char sccsid[] = "@(#)malloc.c 8.1 (Berkeley) 6/4/93"; 40 #else 41 __RCSID("$NetBSD: malloc.c,v 1.15 1998/11/15 17:13:51 christos Exp $"); 42 #endif 43 #endif /* LIBC_SCCS and not lint */ 44 45 /* 46 * malloc.c (Caltech) 2/21/82 47 * Chris Kingsley, kingsley@cit-20. 48 * 49 * This is a very fast storage allocator. It allocates blocks of a small 50 * number of different sizes, and keeps free lists of each size. Blocks that 51 * don't exactly fit are passed up to the next larger size. In this 52 * implementation, the available sizes are 2^n-4 (or 2^n-10) bytes long. 53 * This is designed for use in a virtual memory environment. 54 */ 55 56 #include "namespace.h" 57 #if defined(DEBUG) || defined(RCHECK) || defined(MSTATS) 58 #include <stdio.h> 59 #endif 60 #include <sys/types.h> 61 #include <stdlib.h> 62 #include <string.h> 63 #include <unistd.h> 64 65 #define NULL 0 66 67 68 /* 69 * The overhead on a block is at least 4 bytes. When free, this space 70 * contains a pointer to the next free block, and the bottom two bits must 71 * be zero. When in use, the first byte is set to MAGIC, and the second 72 * byte is the size index. The remaining bytes are for alignment. 73 * If range checking is enabled then a second word holds the size of the 74 * requested block, less 1, rounded up to a multiple of sizeof(RMAGIC). 75 * The order of elements is critical: ov_magic must overlay the low order 76 * bits of ov_next, and ov_magic can not be a valid ov_next bit pattern. 77 */ 78 union overhead { 79 union overhead *ov_next; /* when free */ 80 struct { 81 u_char ovu_magic; /* magic number */ 82 u_char ovu_index; /* bucket # */ 83 #ifdef RCHECK 84 u_short ovu_rmagic; /* range magic number */ 85 u_long ovu_size; /* actual block size */ 86 #endif 87 } ovu; 88 #define ov_magic ovu.ovu_magic 89 #define ov_index ovu.ovu_index 90 #define ov_rmagic ovu.ovu_rmagic 91 #define ov_size ovu.ovu_size 92 }; 93 94 #define MAGIC 0xef /* magic # on accounting info */ 95 #define RMAGIC 0x5555 /* magic # on range info */ 96 97 #ifdef RCHECK 98 #define RSLOP sizeof (u_short) 99 #else 100 #define RSLOP 0 101 #endif 102 103 /* 104 * nextf[i] is the pointer to the next free block of size 2^(i+3). The 105 * smallest allocatable block is 8 bytes. The overhead information 106 * precedes the data area returned to the user. 107 */ 108 #define NBUCKETS 30 109 static union overhead *nextf[NBUCKETS]; 110 111 static long pagesz; /* page size */ 112 static int pagebucket; /* page size bucket */ 113 114 #ifdef MSTATS 115 /* 116 * nmalloc[i] is the difference between the number of mallocs and frees 117 * for a given block size. 118 */ 119 static u_int nmalloc[NBUCKETS]; 120 #include <stdio.h> 121 #endif 122 123 static void morecore __P((int)); 124 static int findbucket __P((union overhead *, int)); 125 #ifdef MSTATS 126 void mstats __P((char *)); 127 #endif 128 129 #if defined(DEBUG) || defined(RCHECK) 130 #define ASSERT(p) if (!(p)) botch(__STRING(p)) 131 132 static botch __P((char *)); 133 134 static 135 botch(s) 136 char *s; 137 { 138 fprintf(stderr, "\r\nassertion botched: %s\r\n", s); 139 (void) fflush(stderr); /* just in case user buffered it */ 140 abort(); 141 } 142 #else 143 #define ASSERT(p) 144 #endif 145 146 void * 147 malloc(nbytes) 148 size_t nbytes; 149 { 150 union overhead *op; 151 int bucket; 152 long n; 153 unsigned amt; 154 155 /* 156 * First time malloc is called, setup page size and 157 * align break pointer so all data will be page aligned. 158 */ 159 if (pagesz == 0) { 160 pagesz = n = getpagesize(); 161 op = (union overhead *)(void *)sbrk(0); 162 n = n - sizeof (*op) - ((long)op & (n - 1)); 163 if (n < 0) 164 n += pagesz; 165 if (n) { 166 if (sbrk((int)n) == (char *)-1) 167 return (NULL); 168 } 169 bucket = 0; 170 amt = 8; 171 while (pagesz > amt) { 172 amt <<= 1; 173 bucket++; 174 } 175 pagebucket = bucket; 176 } 177 /* 178 * Convert amount of memory requested into closest block size 179 * stored in hash buckets which satisfies request. 180 * Account for space used per block for accounting. 181 */ 182 if (nbytes <= (n = pagesz - sizeof (*op) - RSLOP)) { 183 #ifndef RCHECK 184 amt = 8; /* size of first bucket */ 185 bucket = 0; 186 #else 187 amt = 16; /* size of first bucket */ 188 bucket = 1; 189 #endif 190 n = -((long)sizeof (*op) + RSLOP); 191 } else { 192 amt = (unsigned)pagesz; 193 bucket = pagebucket; 194 } 195 while (nbytes > amt + n) { 196 amt <<= 1; 197 if (amt == 0) 198 return (NULL); 199 bucket++; 200 } 201 /* 202 * If nothing in hash bucket right now, 203 * request more memory from the system. 204 */ 205 if ((op = nextf[bucket]) == NULL) { 206 morecore(bucket); 207 if ((op = nextf[bucket]) == NULL) 208 return (NULL); 209 } 210 /* remove from linked list */ 211 nextf[bucket] = op->ov_next; 212 op->ov_magic = MAGIC; 213 op->ov_index = bucket; 214 #ifdef MSTATS 215 nmalloc[bucket]++; 216 #endif 217 #ifdef RCHECK 218 /* 219 * Record allocated size of block and 220 * bound space with magic numbers. 221 */ 222 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 223 op->ov_rmagic = RMAGIC; 224 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 225 #endif 226 return ((char *)(void *)(op + 1)); 227 } 228 229 /* 230 * Allocate more memory to the indicated bucket. 231 */ 232 static void 233 morecore(bucket) 234 int bucket; 235 { 236 union overhead *op; 237 long sz; /* size of desired block */ 238 long amt; /* amount to allocate */ 239 long nblks; /* how many blocks we get */ 240 241 /* 242 * sbrk_size <= 0 only for big, FLUFFY, requests (about 243 * 2^30 bytes on a VAX, I think) or for a negative arg. 244 */ 245 sz = 1 << (bucket + 3); 246 #ifdef DEBUG 247 ASSERT(sz > 0); 248 #else 249 if (sz <= 0) 250 return; 251 #endif 252 if (sz < pagesz) { 253 amt = pagesz; 254 nblks = amt / sz; 255 } else { 256 amt = sz + pagesz; 257 nblks = 1; 258 } 259 op = (union overhead *)(void *)sbrk((int)amt); 260 /* no more room! */ 261 if ((long)op == -1) 262 return; 263 /* 264 * Add new memory allocated to that on 265 * free list for this hash bucket. 266 */ 267 nextf[bucket] = op; 268 while (--nblks > 0) { 269 op->ov_next = 270 (union overhead *)(void *)((caddr_t)(void *)op+(size_t)sz); 271 op = op->ov_next; 272 } 273 } 274 275 void 276 free(cp) 277 void *cp; 278 { 279 long size; 280 union overhead *op; 281 282 if (cp == NULL) 283 return; 284 op = (union overhead *)(void *)((caddr_t)cp - sizeof (union overhead)); 285 #ifdef DEBUG 286 ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */ 287 #else 288 if (op->ov_magic != MAGIC) 289 return; /* sanity */ 290 #endif 291 #ifdef RCHECK 292 ASSERT(op->ov_rmagic == RMAGIC); 293 ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC); 294 #endif 295 size = op->ov_index; 296 ASSERT(size < NBUCKETS); 297 op->ov_next = nextf[(size_t)size]; /* also clobbers ov_magic */ 298 nextf[(size_t)size] = op; 299 #ifdef MSTATS 300 nmalloc[(size_t)size]--; 301 #endif 302 } 303 304 /* 305 * When a program attempts "storage compaction" as mentioned in the 306 * old malloc man page, it realloc's an already freed block. Usually 307 * this is the last block it freed; occasionally it might be farther 308 * back. We have to search all the free lists for the block in order 309 * to determine its bucket: 1st we make one pass thru the lists 310 * checking only the first block in each; if that fails we search 311 * ``__realloc_srchlen'' blocks in each list for a match (the variable 312 * is extern so the caller can modify it). If that fails we just copy 313 * however many bytes was given to realloc() and hope it's not huge. 314 */ 315 int __realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */ 316 317 void * 318 realloc(cp, nbytes) 319 void *cp; 320 size_t nbytes; 321 { 322 u_long onb; 323 long i; 324 union overhead *op; 325 char *res; 326 int was_alloced = 0; 327 328 if (cp == NULL) 329 return (malloc(nbytes)); 330 if (nbytes == 0) { 331 free (cp); 332 return NULL; 333 } 334 op = (union overhead *)(void *)((caddr_t)cp - sizeof (union overhead)); 335 if (op->ov_magic == MAGIC) { 336 was_alloced++; 337 i = op->ov_index; 338 } else { 339 /* 340 * Already free, doing "compaction". 341 * 342 * Search for the old block of memory on the 343 * free list. First, check the most common 344 * case (last element free'd), then (this failing) 345 * the last ``__realloc_srchlen'' items free'd. 346 * If all lookups fail, then assume the size of 347 * the memory block being realloc'd is the 348 * largest possible (so that all "nbytes" of new 349 * memory are copied into). Note that this could cause 350 * a memory fault if the old area was tiny, and the moon 351 * is gibbous. However, that is very unlikely. 352 */ 353 if ((i = findbucket(op, 1)) < 0 && 354 (i = findbucket(op, __realloc_srchlen)) < 0) 355 i = NBUCKETS; 356 } 357 onb = (u_long)1 << (u_long)(i + 3); 358 if (onb < pagesz) 359 onb -= sizeof (*op) + RSLOP; 360 else 361 onb += pagesz - sizeof (*op) - RSLOP; 362 /* avoid the copy if same size block */ 363 if (was_alloced) { 364 if (i) { 365 i = (long)1 << (long)(i + 2); 366 if (i < pagesz) 367 i -= sizeof (*op) + RSLOP; 368 else 369 i += pagesz - sizeof (*op) - RSLOP; 370 } 371 if (nbytes <= onb && nbytes > i) { 372 #ifdef RCHECK 373 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 374 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 375 #endif 376 return(cp); 377 } else 378 free(cp); 379 } 380 if ((res = malloc(nbytes)) == NULL) 381 return (NULL); 382 if (cp != res) /* common optimization if "compacting" */ 383 memmove(res, cp, (size_t)((nbytes < onb) ? nbytes : onb)); 384 return (res); 385 } 386 387 /* 388 * Search ``srchlen'' elements of each free list for a block whose 389 * header starts at ``freep''. If srchlen is -1 search the whole list. 390 * Return bucket number, or -1 if not found. 391 */ 392 static int 393 findbucket(freep, srchlen) 394 union overhead *freep; 395 int srchlen; 396 { 397 union overhead *p; 398 int i, j; 399 400 for (i = 0; i < NBUCKETS; i++) { 401 j = 0; 402 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) { 403 if (p == freep) 404 return (i); 405 j++; 406 } 407 } 408 return (-1); 409 } 410 411 #ifdef MSTATS 412 /* 413 * mstats - print out statistics about malloc 414 * 415 * Prints two lines of numbers, one showing the length of the free list 416 * for each size category, the second showing the number of mallocs - 417 * frees for each size category. 418 */ 419 void 420 mstats(s) 421 char *s; 422 { 423 int i, j; 424 union overhead *p; 425 int totfree = 0, 426 totused = 0; 427 428 fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s); 429 for (i = 0; i < NBUCKETS; i++) { 430 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++) 431 ; 432 fprintf(stderr, " %d", j); 433 totfree += j * (1 << (i + 3)); 434 } 435 fprintf(stderr, "\nused:\t"); 436 for (i = 0; i < NBUCKETS; i++) { 437 fprintf(stderr, " %d", nmalloc[i]); 438 totused += nmalloc[i] * (1 << (i + 3)); 439 } 440 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n", 441 totused, totfree); 442 } 443 #endif 444