1 /* $NetBSD: malloc.c,v 1.1 2003/04/21 22:21:06 elric 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 1.1 2003/04/21 22:21:06 elric 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 <sys/types.h> 57 #if defined(DEBUG) || defined(RCHECK) 58 #include <sys/uio.h> 59 #endif 60 #if defined(RCHECK) || defined(MSTATS) 61 #include <stdio.h> 62 #endif 63 #include <stdlib.h> 64 #include <string.h> 65 #include <unistd.h> 66 #include "reentrant.h" 67 68 69 /* 70 * The overhead on a block is at least 4 bytes. When free, this space 71 * contains a pointer to the next free block, and the bottom two bits must 72 * be zero. When in use, the first byte is set to MAGIC, and the second 73 * byte is the size index. The remaining bytes are for alignment. 74 * If range checking is enabled then a second word holds the size of the 75 * requested block, less 1, rounded up to a multiple of sizeof(RMAGIC). 76 * The order of elements is critical: ov_magic must overlay the low order 77 * bits of ov_next, and ov_magic can not be a valid ov_next bit pattern. 78 */ 79 union overhead { 80 union overhead *ov_next; /* when free */ 81 struct { 82 u_char ovu_magic; /* magic number */ 83 u_char ovu_index; /* bucket # */ 84 #ifdef RCHECK 85 u_short ovu_rmagic; /* range magic number */ 86 u_long ovu_size; /* actual block size */ 87 #endif 88 } ovu; 89 #define ov_magic ovu.ovu_magic 90 #define ov_index ovu.ovu_index 91 #define ov_rmagic ovu.ovu_rmagic 92 #define ov_size ovu.ovu_size 93 }; 94 95 #define MAGIC 0xef /* magic # on accounting info */ 96 #ifdef RCHECK 97 #define RMAGIC 0x5555 /* magic # on range info */ 98 #endif 99 100 #ifdef RCHECK 101 #define RSLOP sizeof (u_short) 102 #else 103 #define RSLOP 0 104 #endif 105 106 /* 107 * nextf[i] is the pointer to the next free block of size 2^(i+3). The 108 * smallest allocatable block is 8 bytes. The overhead information 109 * precedes the data area returned to the user. 110 */ 111 #define NBUCKETS 30 112 static union overhead *nextf[NBUCKETS]; 113 114 static long pagesz; /* page size */ 115 static int pagebucket; /* page size bucket */ 116 117 #ifdef MSTATS 118 /* 119 * nmalloc[i] is the difference between the number of mallocs and frees 120 * for a given block size. 121 */ 122 static u_int nmalloc[NBUCKETS]; 123 #endif 124 125 #ifdef _REENT 126 static mutex_t malloc_mutex = MUTEX_INITIALIZER; 127 #endif 128 129 static void morecore __P((int)); 130 static int findbucket __P((union overhead *, int)); 131 #ifdef MSTATS 132 void mstats __P((const char *)); 133 #endif 134 135 #if defined(DEBUG) || defined(RCHECK) 136 #define ASSERT(p) if (!(p)) botch(__STRING(p)) 137 138 static void botch __P((const char *)); 139 140 /* 141 * NOTE: since this may be called while malloc_mutex is locked, stdio must not 142 * be used in this function. 143 */ 144 static void 145 botch(s) 146 const char *s; 147 { 148 struct iovec iov[3]; 149 150 iov[0].iov_base = "\nassertion botched: "; 151 iov[0].iov_len = 20; 152 iov[1].iov_base = (void *)s; 153 iov[1].iov_len = strlen(s); 154 iov[2].iov_base = "\n"; 155 iov[2].iov_len = 1; 156 157 /* 158 * This place deserves a word of warning: a cancellation point will 159 * occur when executing writev(), and we might be still owning 160 * malloc_mutex. At this point we need to disable cancellation 161 * until `after' abort() because i) establishing a cancellation handler 162 * might, depending on the implementation, result in another malloc() 163 * to be executed, and ii) it is really not desirable to let execution 164 * continue. `Fix me.' 165 * 166 * Note that holding mutex_lock during abort() is safe. 167 */ 168 169 (void)writev(STDERR_FILENO, iov, 3); 170 abort(); 171 } 172 #else 173 #define ASSERT(p) 174 #endif 175 176 void * 177 malloc(nbytes) 178 size_t nbytes; 179 { 180 union overhead *op; 181 int bucket; 182 long n; 183 unsigned amt; 184 185 mutex_lock(&malloc_mutex); 186 187 /* 188 * First time malloc is called, setup page size and 189 * align break pointer so all data will be page aligned. 190 */ 191 if (pagesz == 0) { 192 pagesz = n = getpagesize(); 193 ASSERT(pagesz > 0); 194 op = (union overhead *)(void *)sbrk(0); 195 n = n - sizeof (*op) - ((long)op & (n - 1)); 196 if (n < 0) 197 n += pagesz; 198 if (n) { 199 if (sbrk((int)n) == (void *)-1) { 200 mutex_unlock(&malloc_mutex); 201 return (NULL); 202 } 203 } 204 bucket = 0; 205 amt = 8; 206 while (pagesz > amt) { 207 amt <<= 1; 208 bucket++; 209 } 210 pagebucket = bucket; 211 } 212 /* 213 * Convert amount of memory requested into closest block size 214 * stored in hash buckets which satisfies request. 215 * Account for space used per block for accounting. 216 */ 217 if (nbytes <= (n = pagesz - sizeof (*op) - RSLOP)) { 218 #ifndef RCHECK 219 amt = 8; /* size of first bucket */ 220 bucket = 0; 221 #else 222 amt = 16; /* size of first bucket */ 223 bucket = 1; 224 #endif 225 n = -((long)sizeof (*op) + RSLOP); 226 } else { 227 amt = (unsigned)pagesz; 228 bucket = pagebucket; 229 } 230 while (nbytes > amt + n) { 231 amt <<= 1; 232 if (amt == 0) 233 return (NULL); 234 bucket++; 235 } 236 /* 237 * If nothing in hash bucket right now, 238 * request more memory from the system. 239 */ 240 if ((op = nextf[bucket]) == NULL) { 241 morecore(bucket); 242 if ((op = nextf[bucket]) == NULL) { 243 mutex_unlock(&malloc_mutex); 244 return (NULL); 245 } 246 } 247 /* remove from linked list */ 248 nextf[bucket] = op->ov_next; 249 op->ov_magic = MAGIC; 250 op->ov_index = bucket; 251 #ifdef MSTATS 252 nmalloc[bucket]++; 253 #endif 254 mutex_unlock(&malloc_mutex); 255 #ifdef RCHECK 256 /* 257 * Record allocated size of block and 258 * bound space with magic numbers. 259 */ 260 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 261 op->ov_rmagic = RMAGIC; 262 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 263 #endif 264 return ((void *)(op + 1)); 265 } 266 267 /* 268 * Allocate more memory to the indicated bucket. 269 */ 270 static void 271 morecore(bucket) 272 int bucket; 273 { 274 union overhead *op; 275 long sz; /* size of desired block */ 276 long amt; /* amount to allocate */ 277 long nblks; /* how many blocks we get */ 278 279 /* 280 * sbrk_size <= 0 only for big, FLUFFY, requests (about 281 * 2^30 bytes on a VAX, I think) or for a negative arg. 282 */ 283 sz = 1 << (bucket + 3); 284 #ifdef DEBUG 285 ASSERT(sz > 0); 286 #else 287 if (sz <= 0) 288 return; 289 #endif 290 if (sz < pagesz) { 291 amt = pagesz; 292 nblks = amt / sz; 293 } else { 294 amt = sz + pagesz; 295 nblks = 1; 296 } 297 op = (union overhead *)(void *)sbrk((int)amt); 298 /* no more room! */ 299 if ((long)op == -1) 300 return; 301 /* 302 * Add new memory allocated to that on 303 * free list for this hash bucket. 304 */ 305 nextf[bucket] = op; 306 while (--nblks > 0) { 307 op->ov_next = 308 (union overhead *)(void *)((caddr_t)(void *)op+(size_t)sz); 309 op = op->ov_next; 310 } 311 } 312 313 void 314 free(cp) 315 void *cp; 316 { 317 long size; 318 union overhead *op; 319 320 if (cp == NULL) 321 return; 322 op = (union overhead *)(void *)((caddr_t)cp - sizeof (union overhead)); 323 #ifdef DEBUG 324 ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */ 325 #else 326 if (op->ov_magic != MAGIC) 327 return; /* sanity */ 328 #endif 329 #ifdef RCHECK 330 ASSERT(op->ov_rmagic == RMAGIC); 331 ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC); 332 #endif 333 size = op->ov_index; 334 ASSERT(size < NBUCKETS); 335 mutex_lock(&malloc_mutex); 336 op->ov_next = nextf[(unsigned int)size];/* also clobbers ov_magic */ 337 nextf[(unsigned int)size] = op; 338 #ifdef MSTATS 339 nmalloc[(size_t)size]--; 340 #endif 341 mutex_unlock(&malloc_mutex); 342 } 343 344 /* 345 * When a program attempts "storage compaction" as mentioned in the 346 * old malloc man page, it realloc's an already freed block. Usually 347 * this is the last block it freed; occasionally it might be farther 348 * back. We have to search all the free lists for the block in order 349 * to determine its bucket: 1st we make one pass thru the lists 350 * checking only the first block in each; if that fails we search 351 * ``__realloc_srchlen'' blocks in each list for a match (the variable 352 * is extern so the caller can modify it). If that fails we just copy 353 * however many bytes was given to realloc() and hope it's not huge. 354 */ 355 int __realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */ 356 357 void * 358 realloc(cp, nbytes) 359 void *cp; 360 size_t nbytes; 361 { 362 u_long onb; 363 long i; 364 union overhead *op; 365 char *res; 366 int was_alloced = 0; 367 368 if (cp == NULL) 369 return (malloc(nbytes)); 370 if (nbytes == 0) { 371 free (cp); 372 return (NULL); 373 } 374 op = (union overhead *)(void *)((caddr_t)cp - sizeof (union overhead)); 375 mutex_lock(&malloc_mutex); 376 if (op->ov_magic == MAGIC) { 377 was_alloced++; 378 i = op->ov_index; 379 } else { 380 /* 381 * Already free, doing "compaction". 382 * 383 * Search for the old block of memory on the 384 * free list. First, check the most common 385 * case (last element free'd), then (this failing) 386 * the last ``__realloc_srchlen'' items free'd. 387 * If all lookups fail, then assume the size of 388 * the memory block being realloc'd is the 389 * largest possible (so that all "nbytes" of new 390 * memory are copied into). Note that this could cause 391 * a memory fault if the old area was tiny, and the moon 392 * is gibbous. However, that is very unlikely. 393 */ 394 if ((i = findbucket(op, 1)) < 0 && 395 (i = findbucket(op, __realloc_srchlen)) < 0) 396 i = NBUCKETS; 397 } 398 onb = (u_long)1 << (u_long)(i + 3); 399 if (onb < pagesz) 400 onb -= sizeof (*op) + RSLOP; 401 else 402 onb += pagesz - sizeof (*op) - RSLOP; 403 /* avoid the copy if same size block */ 404 if (was_alloced) { 405 if (i) { 406 i = (long)1 << (long)(i + 2); 407 if (i < pagesz) 408 i -= sizeof (*op) + RSLOP; 409 else 410 i += pagesz - sizeof (*op) - RSLOP; 411 } 412 if (nbytes <= onb && nbytes > i) { 413 #ifdef RCHECK 414 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 415 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 416 #endif 417 mutex_unlock(&malloc_mutex); 418 return (cp); 419 420 } 421 #ifndef _REENT 422 else 423 free(cp); 424 #endif 425 } 426 mutex_unlock(&malloc_mutex); 427 if ((res = malloc(nbytes)) == NULL) { 428 #ifdef _REENT 429 free(cp); 430 #endif 431 return (NULL); 432 } 433 #ifndef _REENT 434 if (cp != res) /* common optimization if "compacting" */ 435 (void)memmove(res, cp, (size_t)((nbytes < onb) ? nbytes : onb)); 436 #else 437 (void)memmove(res, cp, (size_t)((nbytes < onb) ? nbytes : onb)); 438 free(cp); 439 #endif 440 return (res); 441 } 442 443 /* 444 * Search ``srchlen'' elements of each free list for a block whose 445 * header starts at ``freep''. If srchlen is -1 search the whole list. 446 * Return bucket number, or -1 if not found. 447 */ 448 static int 449 findbucket(freep, srchlen) 450 union overhead *freep; 451 int srchlen; 452 { 453 union overhead *p; 454 int i, j; 455 456 for (i = 0; i < NBUCKETS; i++) { 457 j = 0; 458 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) { 459 if (p == freep) 460 return (i); 461 j++; 462 } 463 } 464 return (-1); 465 } 466 467 #ifdef MSTATS 468 /* 469 * mstats - print out statistics about malloc 470 * 471 * Prints two lines of numbers, one showing the length of the free list 472 * for each size category, the second showing the number of mallocs - 473 * frees for each size category. 474 */ 475 void 476 mstats(s) 477 char *s; 478 { 479 int i, j; 480 union overhead *p; 481 int totfree = 0, 482 totused = 0; 483 484 fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s); 485 for (i = 0; i < NBUCKETS; i++) { 486 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++) 487 ; 488 fprintf(stderr, " %d", j); 489 totfree += j * (1 << (i + 3)); 490 } 491 fprintf(stderr, "\nused:\t"); 492 for (i = 0; i < NBUCKETS; i++) { 493 fprintf(stderr, " %d", nmalloc[i]); 494 totused += nmalloc[i] * (1 << (i + 3)); 495 } 496 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n", 497 totused, totfree); 498 } 499 #endif 500