1 /*- 2 * Copyright (c) 1983 Regents of the University of California. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * @(#)malloc.c 5.11 (Berkeley) 2/23/91 34 * $FreeBSD: src/libexec/rtld-elf/malloc.c,v 1.3.2.3 2003/02/20 20:42:46 kan Exp $ 35 * $DragonFly: src/libexec/rtld-elf/malloc.c,v 1.3 2008/06/05 18:01:49 swildner Exp $ 36 */ 37 38 /* 39 * malloc.c (Caltech) 2/21/82 40 * Chris Kingsley, kingsley@cit-20. 41 * 42 * This is a very fast storage allocator. It allocates blocks of a small 43 * number of different sizes, and keeps free lists of each size. Blocks that 44 * don't exactly fit are passed up to the next larger size. In this 45 * implementation, the available sizes are 2^n-4 (or 2^n-10) bytes long. 46 * This is designed for use in a virtual memory environment. 47 */ 48 49 #include <sys/types.h> 50 #include <err.h> 51 #include <paths.h> 52 #include <stdarg.h> 53 #include <stdio.h> 54 #include <stdlib.h> 55 #include <string.h> 56 #include <unistd.h> 57 #include <sys/param.h> 58 #include <sys/mman.h> 59 #ifndef BSD 60 #define MAP_COPY MAP_PRIVATE 61 #define MAP_FILE 0 62 #define MAP_ANON 0 63 #endif 64 65 #ifndef BSD /* Need do better than this */ 66 #define NEED_DEV_ZERO 1 67 #endif 68 69 static void morecore(); 70 static int findbucket(); 71 72 /* 73 * Pre-allocate mmap'ed pages 74 */ 75 #define NPOOLPAGES (32*1024/pagesz) 76 static caddr_t pagepool_start, pagepool_end; 77 static int morepages(); 78 79 /* 80 * The overhead on a block is at least 4 bytes. When free, this space 81 * contains a pointer to the next free block, and the bottom two bits must 82 * be zero. When in use, the first byte is set to MAGIC, and the second 83 * byte is the size index. The remaining bytes are for alignment. 84 * If range checking is enabled then a second word holds the size of the 85 * requested block, less 1, rounded up to a multiple of sizeof(RMAGIC). 86 * The order of elements is critical: ov_magic must overlay the low order 87 * bits of ov_next, and ov_magic can not be a valid ov_next bit pattern. 88 */ 89 union overhead { 90 union overhead *ov_next; /* when free */ 91 struct { 92 u_char ovu_magic; /* magic number */ 93 u_char ovu_index; /* bucket # */ 94 #ifdef RCHECK 95 u_short ovu_rmagic; /* range magic number */ 96 u_int ovu_size; /* actual block size */ 97 #endif 98 } ovu; 99 #define ov_magic ovu.ovu_magic 100 #define ov_index ovu.ovu_index 101 #define ov_rmagic ovu.ovu_rmagic 102 #define ov_size ovu.ovu_size 103 }; 104 105 #define MAGIC 0xef /* magic # on accounting info */ 106 #define RMAGIC 0x5555 /* magic # on range info */ 107 108 #ifdef RCHECK 109 #define RSLOP sizeof (u_short) 110 #else 111 #define RSLOP 0 112 #endif 113 114 /* 115 * nextf[i] is the pointer to the next free block of size 2^(i+3). The 116 * smallest allocatable block is 8 bytes. The overhead information 117 * precedes the data area returned to the user. 118 */ 119 #define NBUCKETS 30 120 static union overhead *nextf[NBUCKETS]; 121 122 static int pagesz; /* page size */ 123 static int pagebucket; /* page size bucket */ 124 125 #ifdef MSTATS 126 /* 127 * nmalloc[i] is the difference between the number of mallocs and frees 128 * for a given block size. 129 */ 130 static u_int nmalloc[NBUCKETS]; 131 #include <stdio.h> 132 #endif 133 134 #if defined(MALLOC_DEBUG) || defined(RCHECK) 135 #define ASSERT(p) if (!(p)) botch("p") 136 #include <stdio.h> 137 static void 138 botch(s) 139 char *s; 140 { 141 fprintf(stderr, "\r\nassertion botched: %s\r\n", s); 142 (void) fflush(stderr); /* just in case user buffered it */ 143 abort(); 144 } 145 #else 146 #define ASSERT(p) 147 #endif 148 149 /* Debugging stuff */ 150 static void xprintf(const char *, ...); 151 #define TRACE() xprintf("TRACE %s:%d\n", __FILE__, __LINE__) 152 153 void * 154 malloc(nbytes) 155 size_t nbytes; 156 { 157 register union overhead *op; 158 register int bucket; 159 register long n; 160 register unsigned amt; 161 162 /* 163 * First time malloc is called, setup page size and 164 * align break pointer so all data will be page aligned. 165 */ 166 if (pagesz == 0) { 167 pagesz = n = getpagesize(); 168 if (morepages(NPOOLPAGES) == 0) 169 return NULL; 170 op = (union overhead *)(pagepool_start); 171 n = n - sizeof (*op) - ((long)op & (n - 1)); 172 if (n < 0) 173 n += pagesz; 174 if (n) { 175 pagepool_start += n; 176 } 177 bucket = 0; 178 amt = 8; 179 while (pagesz > amt) { 180 amt <<= 1; 181 bucket++; 182 } 183 pagebucket = bucket; 184 } 185 /* 186 * Convert amount of memory requested into closest block size 187 * stored in hash buckets which satisfies request. 188 * Account for space used per block for accounting. 189 */ 190 if (nbytes <= (n = pagesz - sizeof (*op) - RSLOP)) { 191 #ifndef RCHECK 192 amt = 8; /* size of first bucket */ 193 bucket = 0; 194 #else 195 amt = 16; /* size of first bucket */ 196 bucket = 1; 197 #endif 198 n = -(sizeof (*op) + RSLOP); 199 } else { 200 amt = pagesz; 201 bucket = pagebucket; 202 } 203 while (nbytes > amt + n) { 204 amt <<= 1; 205 if (amt == 0) 206 return (NULL); 207 bucket++; 208 } 209 /* 210 * If nothing in hash bucket right now, 211 * request more memory from the system. 212 */ 213 if ((op = nextf[bucket]) == NULL) { 214 morecore(bucket); 215 if ((op = nextf[bucket]) == NULL) 216 return (NULL); 217 } 218 /* remove from linked list */ 219 nextf[bucket] = op->ov_next; 220 op->ov_magic = MAGIC; 221 op->ov_index = bucket; 222 #ifdef MSTATS 223 nmalloc[bucket]++; 224 #endif 225 #ifdef RCHECK 226 /* 227 * Record allocated size of block and 228 * bound space with magic numbers. 229 */ 230 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 231 op->ov_rmagic = RMAGIC; 232 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 233 #endif 234 return ((char *)(op + 1)); 235 } 236 237 /* 238 * Used by rtld.c, if we don't override it here the calloc from 239 * libc may try to pull in the malloc/realloc/free from libc too. 240 */ 241 void * 242 calloc(size_t num, size_t size) 243 { 244 void *p; 245 246 size *= num; 247 if ((p = malloc(size)) != NULL) 248 bzero(p, size); 249 return(p); 250 } 251 252 /* 253 * Allocate more memory to the indicated bucket. 254 */ 255 static void 256 morecore(bucket) 257 int bucket; 258 { 259 register union overhead *op; 260 register int sz; /* size of desired block */ 261 int amt; /* amount to allocate */ 262 int nblks; /* how many blocks we get */ 263 264 /* 265 * sbrk_size <= 0 only for big, FLUFFY, requests (about 266 * 2^30 bytes on a VAX, I think) or for a negative arg. 267 */ 268 sz = 1 << (bucket + 3); 269 #ifdef MALLOC_DEBUG 270 ASSERT(sz > 0); 271 #else 272 if (sz <= 0) 273 return; 274 #endif 275 if (sz < pagesz) { 276 amt = pagesz; 277 nblks = amt / sz; 278 } else { 279 amt = sz + pagesz; 280 nblks = 1; 281 } 282 if (amt > pagepool_end - pagepool_start) 283 if (morepages(amt/pagesz + NPOOLPAGES) == 0) 284 return; 285 op = (union overhead *)pagepool_start; 286 pagepool_start += amt; 287 288 /* 289 * Add new memory allocated to that on 290 * free list for this hash bucket. 291 */ 292 nextf[bucket] = op; 293 while (--nblks > 0) { 294 op->ov_next = (union overhead *)((caddr_t)op + sz); 295 op = (union overhead *)((caddr_t)op + sz); 296 } 297 } 298 299 void 300 free(cp) 301 void *cp; 302 { 303 register int size; 304 register union overhead *op; 305 306 if (cp == NULL) 307 return; 308 op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); 309 #ifdef MALLOC_DEBUG 310 ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */ 311 #else 312 if (op->ov_magic != MAGIC) 313 return; /* sanity */ 314 #endif 315 #ifdef RCHECK 316 ASSERT(op->ov_rmagic == RMAGIC); 317 ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC); 318 #endif 319 size = op->ov_index; 320 ASSERT(size < NBUCKETS); 321 op->ov_next = nextf[size]; /* also clobbers ov_magic */ 322 nextf[size] = op; 323 #ifdef MSTATS 324 nmalloc[size]--; 325 #endif 326 } 327 328 /* 329 * When a program attempts "storage compaction" as mentioned in the 330 * old malloc man page, it realloc's an already freed block. Usually 331 * this is the last block it freed; occasionally it might be farther 332 * back. We have to search all the free lists for the block in order 333 * to determine its bucket: 1st we make one pass thru the lists 334 * checking only the first block in each; if that fails we search 335 * ``realloc_srchlen'' blocks in each list for a match (the variable 336 * is extern so the caller can modify it). If that fails we just copy 337 * however many bytes was given to realloc() and hope it's not huge. 338 */ 339 int realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */ 340 341 void * 342 realloc(cp, nbytes) 343 void *cp; 344 size_t nbytes; 345 { 346 register u_int onb; 347 register int i; 348 union overhead *op; 349 char *res; 350 int was_alloced = 0; 351 352 if (cp == NULL) 353 return (malloc(nbytes)); 354 op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); 355 if (op->ov_magic == MAGIC) { 356 was_alloced++; 357 i = op->ov_index; 358 } else { 359 /* 360 * Already free, doing "compaction". 361 * 362 * Search for the old block of memory on the 363 * free list. First, check the most common 364 * case (last element free'd), then (this failing) 365 * the last ``realloc_srchlen'' items free'd. 366 * If all lookups fail, then assume the size of 367 * the memory block being realloc'd is the 368 * largest possible (so that all "nbytes" of new 369 * memory are copied into). Note that this could cause 370 * a memory fault if the old area was tiny, and the moon 371 * is gibbous. However, that is very unlikely. 372 */ 373 if ((i = findbucket(op, 1)) < 0 && 374 (i = findbucket(op, realloc_srchlen)) < 0) 375 i = NBUCKETS; 376 } 377 onb = 1 << (i + 3); 378 if (onb < pagesz) 379 onb -= sizeof (*op) + RSLOP; 380 else 381 onb += pagesz - sizeof (*op) - RSLOP; 382 /* avoid the copy if same size block */ 383 if (was_alloced) { 384 if (i) { 385 i = 1 << (i + 2); 386 if (i < pagesz) 387 i -= sizeof (*op) + RSLOP; 388 else 389 i += pagesz - sizeof (*op) - RSLOP; 390 } 391 if (nbytes <= onb && nbytes > i) { 392 #ifdef RCHECK 393 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 394 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 395 #endif 396 return(cp); 397 } else 398 free(cp); 399 } 400 if ((res = malloc(nbytes)) == NULL) 401 return (NULL); 402 if (cp != res) /* common optimization if "compacting" */ 403 bcopy(cp, res, (nbytes < onb) ? nbytes : onb); 404 return (res); 405 } 406 407 /* 408 * Search ``srchlen'' elements of each free list for a block whose 409 * header starts at ``freep''. If srchlen is -1 search the whole list. 410 * Return bucket number, or -1 if not found. 411 */ 412 static int 413 findbucket(freep, srchlen) 414 union overhead *freep; 415 int srchlen; 416 { 417 register union overhead *p; 418 register int i, j; 419 420 for (i = 0; i < NBUCKETS; i++) { 421 j = 0; 422 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) { 423 if (p == freep) 424 return (i); 425 j++; 426 } 427 } 428 return (-1); 429 } 430 431 #ifdef MSTATS 432 /* 433 * mstats - print out statistics about malloc 434 * 435 * Prints two lines of numbers, one showing the length of the free list 436 * for each size category, the second showing the number of mallocs - 437 * frees for each size category. 438 */ 439 mstats(s) 440 char *s; 441 { 442 register int i, j; 443 register union overhead *p; 444 int totfree = 0, 445 totused = 0; 446 447 fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s); 448 for (i = 0; i < NBUCKETS; i++) { 449 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++) 450 ; 451 fprintf(stderr, " %d", j); 452 totfree += j * (1 << (i + 3)); 453 } 454 fprintf(stderr, "\nused:\t"); 455 for (i = 0; i < NBUCKETS; i++) { 456 fprintf(stderr, " %d", nmalloc[i]); 457 totused += nmalloc[i] * (1 << (i + 3)); 458 } 459 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n", 460 totused, totfree); 461 } 462 #endif 463 464 465 static int 466 morepages(n) 467 int n; 468 { 469 int fd = -1; 470 int offset; 471 472 #ifdef NEED_DEV_ZERO 473 fd = open(_PATH_DEVZERO, O_RDWR, 0); 474 if (fd == -1) 475 perror(_PATH_DEVZERO); 476 #endif 477 478 if (pagepool_end - pagepool_start > pagesz) { 479 caddr_t addr = (caddr_t) 480 (((long)pagepool_start + pagesz - 1) & ~(pagesz - 1)); 481 if (munmap(addr, pagepool_end - addr) != 0) 482 warn("morepages: munmap %p", addr); 483 } 484 485 offset = (long)pagepool_start - ((long)pagepool_start & ~(pagesz - 1)); 486 487 if ((pagepool_start = mmap(0, n * pagesz, 488 PROT_READ|PROT_WRITE, 489 MAP_ANON|MAP_COPY, fd, 0)) == (caddr_t)-1) { 490 xprintf("Cannot map anonymous memory"); 491 return 0; 492 } 493 pagepool_end = pagepool_start + n * pagesz; 494 pagepool_start += offset; 495 496 #ifdef NEED_DEV_ZERO 497 close(fd); 498 #endif 499 return n; 500 } 501 502 /* 503 * Non-mallocing printf, for use by malloc itself. 504 */ 505 static void 506 xprintf(const char *fmt, ...) 507 { 508 char buf[256]; 509 va_list ap; 510 511 va_start(ap, fmt); 512 vsprintf(buf, fmt, ap); 513 (void)write(STDOUT_FILENO, buf, strlen(buf)); 514 va_end(ap); 515 } 516