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 1.2 2003/06/17 04:27:08 dillon 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 #define NULL 0 70 71 static void morecore(); 72 static int findbucket(); 73 74 /* 75 * Pre-allocate mmap'ed pages 76 */ 77 #define NPOOLPAGES (32*1024/pagesz) 78 static caddr_t pagepool_start, pagepool_end; 79 static int morepages(); 80 81 /* 82 * The overhead on a block is at least 4 bytes. When free, this space 83 * contains a pointer to the next free block, and the bottom two bits must 84 * be zero. When in use, the first byte is set to MAGIC, and the second 85 * byte is the size index. The remaining bytes are for alignment. 86 * If range checking is enabled then a second word holds the size of the 87 * requested block, less 1, rounded up to a multiple of sizeof(RMAGIC). 88 * The order of elements is critical: ov_magic must overlay the low order 89 * bits of ov_next, and ov_magic can not be a valid ov_next bit pattern. 90 */ 91 union overhead { 92 union overhead *ov_next; /* when free */ 93 struct { 94 u_char ovu_magic; /* magic number */ 95 u_char ovu_index; /* bucket # */ 96 #ifdef RCHECK 97 u_short ovu_rmagic; /* range magic number */ 98 u_int ovu_size; /* actual block size */ 99 #endif 100 } ovu; 101 #define ov_magic ovu.ovu_magic 102 #define ov_index ovu.ovu_index 103 #define ov_rmagic ovu.ovu_rmagic 104 #define ov_size ovu.ovu_size 105 }; 106 107 #define MAGIC 0xef /* magic # on accounting info */ 108 #define RMAGIC 0x5555 /* magic # on range info */ 109 110 #ifdef RCHECK 111 #define RSLOP sizeof (u_short) 112 #else 113 #define RSLOP 0 114 #endif 115 116 /* 117 * nextf[i] is the pointer to the next free block of size 2^(i+3). The 118 * smallest allocatable block is 8 bytes. The overhead information 119 * precedes the data area returned to the user. 120 */ 121 #define NBUCKETS 30 122 static union overhead *nextf[NBUCKETS]; 123 124 static int pagesz; /* page size */ 125 static int pagebucket; /* page size bucket */ 126 127 #ifdef MSTATS 128 /* 129 * nmalloc[i] is the difference between the number of mallocs and frees 130 * for a given block size. 131 */ 132 static u_int nmalloc[NBUCKETS]; 133 #include <stdio.h> 134 #endif 135 136 #if defined(MALLOC_DEBUG) || defined(RCHECK) 137 #define ASSERT(p) if (!(p)) botch("p") 138 #include <stdio.h> 139 static void 140 botch(s) 141 char *s; 142 { 143 fprintf(stderr, "\r\nassertion botched: %s\r\n", s); 144 (void) fflush(stderr); /* just in case user buffered it */ 145 abort(); 146 } 147 #else 148 #define ASSERT(p) 149 #endif 150 151 /* Debugging stuff */ 152 static void xprintf(const char *, ...); 153 #define TRACE() xprintf("TRACE %s:%d\n", __FILE__, __LINE__) 154 155 void * 156 malloc(nbytes) 157 size_t nbytes; 158 { 159 register union overhead *op; 160 register int bucket; 161 register long n; 162 register unsigned amt; 163 164 /* 165 * First time malloc is called, setup page size and 166 * align break pointer so all data will be page aligned. 167 */ 168 if (pagesz == 0) { 169 pagesz = n = getpagesize(); 170 if (morepages(NPOOLPAGES) == 0) 171 return NULL; 172 op = (union overhead *)(pagepool_start); 173 n = n - sizeof (*op) - ((long)op & (n - 1)); 174 if (n < 0) 175 n += pagesz; 176 if (n) { 177 pagepool_start += n; 178 } 179 bucket = 0; 180 amt = 8; 181 while (pagesz > amt) { 182 amt <<= 1; 183 bucket++; 184 } 185 pagebucket = bucket; 186 } 187 /* 188 * Convert amount of memory requested into closest block size 189 * stored in hash buckets which satisfies request. 190 * Account for space used per block for accounting. 191 */ 192 if (nbytes <= (n = pagesz - sizeof (*op) - RSLOP)) { 193 #ifndef RCHECK 194 amt = 8; /* size of first bucket */ 195 bucket = 0; 196 #else 197 amt = 16; /* size of first bucket */ 198 bucket = 1; 199 #endif 200 n = -(sizeof (*op) + RSLOP); 201 } else { 202 amt = pagesz; 203 bucket = pagebucket; 204 } 205 while (nbytes > amt + n) { 206 amt <<= 1; 207 if (amt == 0) 208 return (NULL); 209 bucket++; 210 } 211 /* 212 * If nothing in hash bucket right now, 213 * request more memory from the system. 214 */ 215 if ((op = nextf[bucket]) == NULL) { 216 morecore(bucket); 217 if ((op = nextf[bucket]) == NULL) 218 return (NULL); 219 } 220 /* remove from linked list */ 221 nextf[bucket] = op->ov_next; 222 op->ov_magic = MAGIC; 223 op->ov_index = bucket; 224 #ifdef MSTATS 225 nmalloc[bucket]++; 226 #endif 227 #ifdef RCHECK 228 /* 229 * Record allocated size of block and 230 * bound space with magic numbers. 231 */ 232 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 233 op->ov_rmagic = RMAGIC; 234 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 235 #endif 236 return ((char *)(op + 1)); 237 } 238 239 /* 240 * Allocate more memory to the indicated bucket. 241 */ 242 static void 243 morecore(bucket) 244 int bucket; 245 { 246 register union overhead *op; 247 register int sz; /* size of desired block */ 248 int amt; /* amount to allocate */ 249 int nblks; /* how many blocks we get */ 250 251 /* 252 * sbrk_size <= 0 only for big, FLUFFY, requests (about 253 * 2^30 bytes on a VAX, I think) or for a negative arg. 254 */ 255 sz = 1 << (bucket + 3); 256 #ifdef MALLOC_DEBUG 257 ASSERT(sz > 0); 258 #else 259 if (sz <= 0) 260 return; 261 #endif 262 if (sz < pagesz) { 263 amt = pagesz; 264 nblks = amt / sz; 265 } else { 266 amt = sz + pagesz; 267 nblks = 1; 268 } 269 if (amt > pagepool_end - pagepool_start) 270 if (morepages(amt/pagesz + NPOOLPAGES) == 0) 271 return; 272 op = (union overhead *)pagepool_start; 273 pagepool_start += amt; 274 275 /* 276 * Add new memory allocated to that on 277 * free list for this hash bucket. 278 */ 279 nextf[bucket] = op; 280 while (--nblks > 0) { 281 op->ov_next = (union overhead *)((caddr_t)op + sz); 282 op = (union overhead *)((caddr_t)op + sz); 283 } 284 } 285 286 void 287 free(cp) 288 void *cp; 289 { 290 register int size; 291 register union overhead *op; 292 293 if (cp == NULL) 294 return; 295 op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); 296 #ifdef MALLOC_DEBUG 297 ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */ 298 #else 299 if (op->ov_magic != MAGIC) 300 return; /* sanity */ 301 #endif 302 #ifdef RCHECK 303 ASSERT(op->ov_rmagic == RMAGIC); 304 ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC); 305 #endif 306 size = op->ov_index; 307 ASSERT(size < NBUCKETS); 308 op->ov_next = nextf[size]; /* also clobbers ov_magic */ 309 nextf[size] = op; 310 #ifdef MSTATS 311 nmalloc[size]--; 312 #endif 313 } 314 315 /* 316 * When a program attempts "storage compaction" as mentioned in the 317 * old malloc man page, it realloc's an already freed block. Usually 318 * this is the last block it freed; occasionally it might be farther 319 * back. We have to search all the free lists for the block in order 320 * to determine its bucket: 1st we make one pass thru the lists 321 * checking only the first block in each; if that fails we search 322 * ``realloc_srchlen'' blocks in each list for a match (the variable 323 * is extern so the caller can modify it). If that fails we just copy 324 * however many bytes was given to realloc() and hope it's not huge. 325 */ 326 int realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */ 327 328 void * 329 realloc(cp, nbytes) 330 void *cp; 331 size_t nbytes; 332 { 333 register u_int onb; 334 register int i; 335 union overhead *op; 336 char *res; 337 int was_alloced = 0; 338 339 if (cp == NULL) 340 return (malloc(nbytes)); 341 op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); 342 if (op->ov_magic == MAGIC) { 343 was_alloced++; 344 i = op->ov_index; 345 } else { 346 /* 347 * Already free, doing "compaction". 348 * 349 * Search for the old block of memory on the 350 * free list. First, check the most common 351 * case (last element free'd), then (this failing) 352 * the last ``realloc_srchlen'' items free'd. 353 * If all lookups fail, then assume the size of 354 * the memory block being realloc'd is the 355 * largest possible (so that all "nbytes" of new 356 * memory are copied into). Note that this could cause 357 * a memory fault if the old area was tiny, and the moon 358 * is gibbous. However, that is very unlikely. 359 */ 360 if ((i = findbucket(op, 1)) < 0 && 361 (i = findbucket(op, realloc_srchlen)) < 0) 362 i = NBUCKETS; 363 } 364 onb = 1 << (i + 3); 365 if (onb < pagesz) 366 onb -= sizeof (*op) + RSLOP; 367 else 368 onb += pagesz - sizeof (*op) - RSLOP; 369 /* avoid the copy if same size block */ 370 if (was_alloced) { 371 if (i) { 372 i = 1 << (i + 2); 373 if (i < pagesz) 374 i -= sizeof (*op) + RSLOP; 375 else 376 i += pagesz - sizeof (*op) - RSLOP; 377 } 378 if (nbytes <= onb && nbytes > i) { 379 #ifdef RCHECK 380 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 381 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 382 #endif 383 return(cp); 384 } else 385 free(cp); 386 } 387 if ((res = malloc(nbytes)) == NULL) 388 return (NULL); 389 if (cp != res) /* common optimization if "compacting" */ 390 bcopy(cp, res, (nbytes < onb) ? nbytes : onb); 391 return (res); 392 } 393 394 /* 395 * Search ``srchlen'' elements of each free list for a block whose 396 * header starts at ``freep''. If srchlen is -1 search the whole list. 397 * Return bucket number, or -1 if not found. 398 */ 399 static int 400 findbucket(freep, srchlen) 401 union overhead *freep; 402 int srchlen; 403 { 404 register union overhead *p; 405 register int i, j; 406 407 for (i = 0; i < NBUCKETS; i++) { 408 j = 0; 409 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) { 410 if (p == freep) 411 return (i); 412 j++; 413 } 414 } 415 return (-1); 416 } 417 418 #ifdef MSTATS 419 /* 420 * mstats - print out statistics about malloc 421 * 422 * Prints two lines of numbers, one showing the length of the free list 423 * for each size category, the second showing the number of mallocs - 424 * frees for each size category. 425 */ 426 mstats(s) 427 char *s; 428 { 429 register int i, j; 430 register union overhead *p; 431 int totfree = 0, 432 totused = 0; 433 434 fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s); 435 for (i = 0; i < NBUCKETS; i++) { 436 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++) 437 ; 438 fprintf(stderr, " %d", j); 439 totfree += j * (1 << (i + 3)); 440 } 441 fprintf(stderr, "\nused:\t"); 442 for (i = 0; i < NBUCKETS; i++) { 443 fprintf(stderr, " %d", nmalloc[i]); 444 totused += nmalloc[i] * (1 << (i + 3)); 445 } 446 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n", 447 totused, totfree); 448 } 449 #endif 450 451 452 static int 453 morepages(n) 454 int n; 455 { 456 int fd = -1; 457 int offset; 458 459 #ifdef NEED_DEV_ZERO 460 fd = open(_PATH_DEVZERO, O_RDWR, 0); 461 if (fd == -1) 462 perror(_PATH_DEVZERO); 463 #endif 464 465 if (pagepool_end - pagepool_start > pagesz) { 466 caddr_t addr = (caddr_t) 467 (((long)pagepool_start + pagesz - 1) & ~(pagesz - 1)); 468 if (munmap(addr, pagepool_end - addr) != 0) 469 warn("morepages: munmap %p", addr); 470 } 471 472 offset = (long)pagepool_start - ((long)pagepool_start & ~(pagesz - 1)); 473 474 if ((pagepool_start = mmap(0, n * pagesz, 475 PROT_READ|PROT_WRITE, 476 MAP_ANON|MAP_COPY, fd, 0)) == (caddr_t)-1) { 477 xprintf("Cannot map anonymous memory"); 478 return 0; 479 } 480 pagepool_end = pagepool_start + n * pagesz; 481 pagepool_start += offset; 482 483 #ifdef NEED_DEV_ZERO 484 close(fd); 485 #endif 486 return n; 487 } 488 489 /* 490 * Non-mallocing printf, for use by malloc itself. 491 */ 492 static void 493 xprintf(const char *fmt, ...) 494 { 495 char buf[256]; 496 va_list ap; 497 498 va_start(ap, fmt); 499 vsprintf(buf, fmt, ap); 500 (void)write(STDOUT_FILENO, buf, strlen(buf)); 501 va_end(ap); 502 } 503