malloc.c revision 154248
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 34#if defined(LIBC_SCCS) && !defined(lint) 35/*static char *sccsid = "from: @(#)malloc.c 5.11 (Berkeley) 2/23/91";*/ 36static char *rcsid = "$FreeBSD: head/libexec/rtld-elf/malloc.c 154248 2006-01-12 07:28:21Z jasone $"; 37#endif /* LIBC_SCCS and not lint */ 38 39/* 40 * malloc.c (Caltech) 2/21/82 41 * Chris Kingsley, kingsley@cit-20. 42 * 43 * This is a very fast storage allocator. It allocates blocks of a small 44 * number of different sizes, and keeps free lists of each size. Blocks that 45 * don't exactly fit are passed up to the next larger size. In this 46 * implementation, the available sizes are 2^n-4 (or 2^n-10) bytes long. 47 * This is designed for use in a virtual memory environment. 48 */ 49 50#include <sys/types.h> 51#include <err.h> 52#include <paths.h> 53#include <stdarg.h> 54#include <stddef.h> 55#include <stdio.h> 56#include <stdlib.h> 57#include <string.h> 58#include <unistd.h> 59#include <sys/param.h> 60#include <sys/mman.h> 61#ifndef BSD 62#define MAP_COPY MAP_PRIVATE 63#define MAP_FILE 0 64#define MAP_ANON 0 65#endif 66 67#ifndef BSD /* Need do better than this */ 68#define NEED_DEV_ZERO 1 69#endif 70 71static void morecore(); 72static int findbucket(); 73 74/* 75 * Pre-allocate mmap'ed pages 76 */ 77#define NPOOLPAGES (32*1024/pagesz) 78static caddr_t pagepool_start, pagepool_end; 79static 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 */ 91union 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 122static union overhead *nextf[NBUCKETS]; 123 124static int pagesz; /* page size */ 125static 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 */ 132static 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> 139static void 140botch(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 */ 152static void xprintf(const char *, ...); 153#define TRACE() xprintf("TRACE %s:%d\n", __FILE__, __LINE__) 154 155void * 156malloc(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 ((unsigned)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 <= (unsigned long)(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 239void * 240calloc(size_t num, size_t size) 241{ 242 void *ret; 243 244 if (size != 0 && (num * size) / size != num) { 245 /* size_t overflow. */ 246 return (NULL); 247 } 248 249 if ((ret = malloc(num * size)) != NULL) 250 memset(ret, 0, num * size); 251 252 return (ret); 253} 254 255/* 256 * Allocate more memory to the indicated bucket. 257 */ 258static void 259morecore(bucket) 260 int bucket; 261{ 262 register union overhead *op; 263 register int sz; /* size of desired block */ 264 int amt; /* amount to allocate */ 265 int nblks; /* how many blocks we get */ 266 267 /* 268 * sbrk_size <= 0 only for big, FLUFFY, requests (about 269 * 2^30 bytes on a VAX, I think) or for a negative arg. 270 */ 271 sz = 1 << (bucket + 3); 272#ifdef MALLOC_DEBUG 273 ASSERT(sz > 0); 274#else 275 if (sz <= 0) 276 return; 277#endif 278 if (sz < pagesz) { 279 amt = pagesz; 280 nblks = amt / sz; 281 } else { 282 amt = sz + pagesz; 283 nblks = 1; 284 } 285 if (amt > pagepool_end - pagepool_start) 286 if (morepages(amt/pagesz + NPOOLPAGES) == 0) 287 return; 288 op = (union overhead *)pagepool_start; 289 pagepool_start += amt; 290 291 /* 292 * Add new memory allocated to that on 293 * free list for this hash bucket. 294 */ 295 nextf[bucket] = op; 296 while (--nblks > 0) { 297 op->ov_next = (union overhead *)((caddr_t)op + sz); 298 op = (union overhead *)((caddr_t)op + sz); 299 } 300} 301 302void 303free(cp) 304 void *cp; 305{ 306 register int size; 307 register union overhead *op; 308 309 if (cp == NULL) 310 return; 311 op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); 312#ifdef MALLOC_DEBUG 313 ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */ 314#else 315 if (op->ov_magic != MAGIC) 316 return; /* sanity */ 317#endif 318#ifdef RCHECK 319 ASSERT(op->ov_rmagic == RMAGIC); 320 ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC); 321#endif 322 size = op->ov_index; 323 ASSERT(size < NBUCKETS); 324 op->ov_next = nextf[size]; /* also clobbers ov_magic */ 325 nextf[size] = op; 326#ifdef MSTATS 327 nmalloc[size]--; 328#endif 329} 330 331/* 332 * When a program attempts "storage compaction" as mentioned in the 333 * old malloc man page, it realloc's an already freed block. Usually 334 * this is the last block it freed; occasionally it might be farther 335 * back. We have to search all the free lists for the block in order 336 * to determine its bucket: 1st we make one pass thru the lists 337 * checking only the first block in each; if that fails we search 338 * ``realloc_srchlen'' blocks in each list for a match (the variable 339 * is extern so the caller can modify it). If that fails we just copy 340 * however many bytes was given to realloc() and hope it's not huge. 341 */ 342int realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */ 343 344void * 345realloc(cp, nbytes) 346 void *cp; 347 size_t nbytes; 348{ 349 register u_int onb; 350 register int i; 351 union overhead *op; 352 char *res; 353 int was_alloced = 0; 354 355 if (cp == NULL) 356 return (malloc(nbytes)); 357 op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); 358 if (op->ov_magic == MAGIC) { 359 was_alloced++; 360 i = op->ov_index; 361 } else { 362 /* 363 * Already free, doing "compaction". 364 * 365 * Search for the old block of memory on the 366 * free list. First, check the most common 367 * case (last element free'd), then (this failing) 368 * the last ``realloc_srchlen'' items free'd. 369 * If all lookups fail, then assume the size of 370 * the memory block being realloc'd is the 371 * largest possible (so that all "nbytes" of new 372 * memory are copied into). Note that this could cause 373 * a memory fault if the old area was tiny, and the moon 374 * is gibbous. However, that is very unlikely. 375 */ 376 if ((i = findbucket(op, 1)) < 0 && 377 (i = findbucket(op, realloc_srchlen)) < 0) 378 i = NBUCKETS; 379 } 380 onb = 1 << (i + 3); 381 if (onb < (u_int)pagesz) 382 onb -= sizeof (*op) + RSLOP; 383 else 384 onb += pagesz - sizeof (*op) - RSLOP; 385 /* avoid the copy if same size block */ 386 if (was_alloced) { 387 if (i) { 388 i = 1 << (i + 2); 389 if (i < pagesz) 390 i -= sizeof (*op) + RSLOP; 391 else 392 i += pagesz - sizeof (*op) - RSLOP; 393 } 394 if (nbytes <= onb && nbytes > (size_t)i) { 395#ifdef RCHECK 396 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 397 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 398#endif 399 return(cp); 400 } else 401 free(cp); 402 } 403 if ((res = malloc(nbytes)) == NULL) 404 return (NULL); 405 if (cp != res) /* common optimization if "compacting" */ 406 bcopy(cp, res, (nbytes < onb) ? nbytes : onb); 407 return (res); 408} 409 410/* 411 * Search ``srchlen'' elements of each free list for a block whose 412 * header starts at ``freep''. If srchlen is -1 search the whole list. 413 * Return bucket number, or -1 if not found. 414 */ 415static int 416findbucket(freep, srchlen) 417 union overhead *freep; 418 int srchlen; 419{ 420 register union overhead *p; 421 register int i, j; 422 423 for (i = 0; i < NBUCKETS; i++) { 424 j = 0; 425 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) { 426 if (p == freep) 427 return (i); 428 j++; 429 } 430 } 431 return (-1); 432} 433 434#ifdef MSTATS 435/* 436 * mstats - print out statistics about malloc 437 * 438 * Prints two lines of numbers, one showing the length of the free list 439 * for each size category, the second showing the number of mallocs - 440 * frees for each size category. 441 */ 442mstats(s) 443 char *s; 444{ 445 register int i, j; 446 register union overhead *p; 447 int totfree = 0, 448 totused = 0; 449 450 fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s); 451 for (i = 0; i < NBUCKETS; i++) { 452 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++) 453 ; 454 fprintf(stderr, " %d", j); 455 totfree += j * (1 << (i + 3)); 456 } 457 fprintf(stderr, "\nused:\t"); 458 for (i = 0; i < NBUCKETS; i++) { 459 fprintf(stderr, " %d", nmalloc[i]); 460 totused += nmalloc[i] * (1 << (i + 3)); 461 } 462 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n", 463 totused, totfree); 464} 465#endif 466 467 468static int 469morepages(n) 470int n; 471{ 472 int fd = -1; 473 int offset; 474 475#ifdef NEED_DEV_ZERO 476 fd = open(_PATH_DEVZERO, O_RDWR, 0); 477 if (fd == -1) 478 perror(_PATH_DEVZERO); 479#endif 480 481 if (pagepool_end - pagepool_start > pagesz) { 482 caddr_t addr = (caddr_t) 483 (((long)pagepool_start + pagesz - 1) & ~(pagesz - 1)); 484 if (munmap(addr, pagepool_end - addr) != 0) 485 warn("morepages: munmap %p", addr); 486 } 487 488 offset = (long)pagepool_start - ((long)pagepool_start & ~(pagesz - 1)); 489 490 if ((pagepool_start = mmap(0, n * pagesz, 491 PROT_READ|PROT_WRITE, 492 MAP_ANON|MAP_COPY, fd, 0)) == (caddr_t)-1) { 493 xprintf("Cannot map anonymous memory"); 494 return 0; 495 } 496 pagepool_end = pagepool_start + n * pagesz; 497 pagepool_start += offset; 498 499#ifdef NEED_DEV_ZERO 500 close(fd); 501#endif 502 return n; 503} 504 505/* 506 * Non-mallocing printf, for use by malloc itself. 507 */ 508static void 509xprintf(const char *fmt, ...) 510{ 511 char buf[256]; 512 va_list ap; 513 514 va_start(ap, fmt); 515 vsprintf(buf, fmt, ap); 516 (void)write(STDOUT_FILENO, buf, strlen(buf)); 517 va_end(ap); 518} 519