malloc.c revision 225152
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 225152 2011-08-24 20:05:13Z kib $"; 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 <sys/sysctl.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#include "rtld_printf.h" 62#ifndef BSD 63#define MAP_COPY MAP_PRIVATE 64#define MAP_FILE 0 65#define MAP_ANON 0 66#endif 67 68#ifndef BSD /* Need do better than this */ 69#define NEED_DEV_ZERO 1 70#endif 71 72static void morecore(); 73static int findbucket(); 74 75/* 76 * Pre-allocate mmap'ed pages 77 */ 78#define NPOOLPAGES (32*1024/pagesz) 79static caddr_t pagepool_start, pagepool_end; 80static int morepages(); 81 82/* 83 * The overhead on a block is at least 4 bytes. When free, this space 84 * contains a pointer to the next free block, and the bottom two bits must 85 * be zero. When in use, the first byte is set to MAGIC, and the second 86 * byte is the size index. The remaining bytes are for alignment. 87 * If range checking is enabled then a second word holds the size of the 88 * requested block, less 1, rounded up to a multiple of sizeof(RMAGIC). 89 * The order of elements is critical: ov_magic must overlay the low order 90 * bits of ov_next, and ov_magic can not be a valid ov_next bit pattern. 91 */ 92union overhead { 93 union overhead *ov_next; /* when free */ 94 struct { 95 u_char ovu_magic; /* magic number */ 96 u_char ovu_index; /* bucket # */ 97#ifdef RCHECK 98 u_short ovu_rmagic; /* range magic number */ 99 u_int ovu_size; /* actual block size */ 100#endif 101 } ovu; 102#define ov_magic ovu.ovu_magic 103#define ov_index ovu.ovu_index 104#define ov_rmagic ovu.ovu_rmagic 105#define ov_size ovu.ovu_size 106}; 107 108#define MAGIC 0xef /* magic # on accounting info */ 109#define RMAGIC 0x5555 /* magic # on range info */ 110 111#ifdef RCHECK 112#define RSLOP sizeof (u_short) 113#else 114#define RSLOP 0 115#endif 116 117/* 118 * nextf[i] is the pointer to the next free block of size 2^(i+3). The 119 * smallest allocatable block is 8 bytes. The overhead information 120 * precedes the data area returned to the user. 121 */ 122#define NBUCKETS 30 123static union overhead *nextf[NBUCKETS]; 124 125static int pagesz; /* page size */ 126static int pagebucket; /* page size bucket */ 127 128#ifdef MSTATS 129/* 130 * nmalloc[i] is the difference between the number of mallocs and frees 131 * for a given block size. 132 */ 133static u_int nmalloc[NBUCKETS]; 134#include <stdio.h> 135#endif 136 137#if defined(MALLOC_DEBUG) || defined(RCHECK) 138#define ASSERT(p) if (!(p)) botch("p") 139#include <stdio.h> 140static void 141botch(s) 142 char *s; 143{ 144 fprintf(stderr, "\r\nassertion botched: %s\r\n", s); 145 (void) fflush(stderr); /* just in case user buffered it */ 146 abort(); 147} 148#else 149#define ASSERT(p) 150#endif 151 152/* Debugging stuff */ 153#define TRACE() rtld_printf("TRACE %s:%d\n", __FILE__, __LINE__) 154 155extern int pagesize; 156 157static int 158rtld_getpagesize(void) 159{ 160 int mib[2]; 161 size_t size; 162 163 if (pagesize != 0) 164 return (pagesize); 165 166 mib[0] = CTL_HW; 167 mib[1] = HW_PAGESIZE; 168 size = sizeof(pagesize); 169 if (sysctl(mib, 2, &pagesize, &size, NULL, 0) == -1) 170 return (-1); 171 return (pagesize); 172 173} 174 175void * 176malloc(nbytes) 177 size_t nbytes; 178{ 179 register union overhead *op; 180 register int bucket; 181 register long n; 182 register unsigned amt; 183 184 /* 185 * First time malloc is called, setup page size and 186 * align break pointer so all data will be page aligned. 187 */ 188 if (pagesz == 0) { 189 pagesz = n = rtld_getpagesize(); 190 if (morepages(NPOOLPAGES) == 0) 191 return NULL; 192 op = (union overhead *)(pagepool_start); 193 n = n - sizeof (*op) - ((long)op & (n - 1)); 194 if (n < 0) 195 n += pagesz; 196 if (n) { 197 pagepool_start += n; 198 } 199 bucket = 0; 200 amt = 8; 201 while ((unsigned)pagesz > amt) { 202 amt <<= 1; 203 bucket++; 204 } 205 pagebucket = bucket; 206 } 207 /* 208 * Convert amount of memory requested into closest block size 209 * stored in hash buckets which satisfies request. 210 * Account for space used per block for accounting. 211 */ 212 if (nbytes <= (unsigned long)(n = pagesz - sizeof (*op) - RSLOP)) { 213#ifndef RCHECK 214 amt = 8; /* size of first bucket */ 215 bucket = 0; 216#else 217 amt = 16; /* size of first bucket */ 218 bucket = 1; 219#endif 220 n = -(sizeof (*op) + RSLOP); 221 } else { 222 amt = pagesz; 223 bucket = pagebucket; 224 } 225 while (nbytes > amt + n) { 226 amt <<= 1; 227 if (amt == 0) 228 return (NULL); 229 bucket++; 230 } 231 /* 232 * If nothing in hash bucket right now, 233 * request more memory from the system. 234 */ 235 if ((op = nextf[bucket]) == NULL) { 236 morecore(bucket); 237 if ((op = nextf[bucket]) == NULL) 238 return (NULL); 239 } 240 /* remove from linked list */ 241 nextf[bucket] = op->ov_next; 242 op->ov_magic = MAGIC; 243 op->ov_index = bucket; 244#ifdef MSTATS 245 nmalloc[bucket]++; 246#endif 247#ifdef RCHECK 248 /* 249 * Record allocated size of block and 250 * bound space with magic numbers. 251 */ 252 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 253 op->ov_rmagic = RMAGIC; 254 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 255#endif 256 return ((char *)(op + 1)); 257} 258 259void * 260calloc(size_t num, size_t size) 261{ 262 void *ret; 263 264 if (size != 0 && (num * size) / size != num) { 265 /* size_t overflow. */ 266 return (NULL); 267 } 268 269 if ((ret = malloc(num * size)) != NULL) 270 memset(ret, 0, num * size); 271 272 return (ret); 273} 274 275/* 276 * Allocate more memory to the indicated bucket. 277 */ 278static void 279morecore(bucket) 280 int bucket; 281{ 282 register union overhead *op; 283 register int sz; /* size of desired block */ 284 int amt; /* amount to allocate */ 285 int nblks; /* how many blocks we get */ 286 287 /* 288 * sbrk_size <= 0 only for big, FLUFFY, requests (about 289 * 2^30 bytes on a VAX, I think) or for a negative arg. 290 */ 291 sz = 1 << (bucket + 3); 292#ifdef MALLOC_DEBUG 293 ASSERT(sz > 0); 294#else 295 if (sz <= 0) 296 return; 297#endif 298 if (sz < pagesz) { 299 amt = pagesz; 300 nblks = amt / sz; 301 } else { 302 amt = sz + pagesz; 303 nblks = 1; 304 } 305 if (amt > pagepool_end - pagepool_start) 306 if (morepages(amt/pagesz + NPOOLPAGES) == 0) 307 return; 308 op = (union overhead *)pagepool_start; 309 pagepool_start += amt; 310 311 /* 312 * Add new memory allocated to that on 313 * free list for this hash bucket. 314 */ 315 nextf[bucket] = op; 316 while (--nblks > 0) { 317 op->ov_next = (union overhead *)((caddr_t)op + sz); 318 op = (union overhead *)((caddr_t)op + sz); 319 } 320} 321 322void 323free(cp) 324 void *cp; 325{ 326 register int size; 327 register union overhead *op; 328 329 if (cp == NULL) 330 return; 331 op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); 332#ifdef MALLOC_DEBUG 333 ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */ 334#else 335 if (op->ov_magic != MAGIC) 336 return; /* sanity */ 337#endif 338#ifdef RCHECK 339 ASSERT(op->ov_rmagic == RMAGIC); 340 ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC); 341#endif 342 size = op->ov_index; 343 ASSERT(size < NBUCKETS); 344 op->ov_next = nextf[size]; /* also clobbers ov_magic */ 345 nextf[size] = op; 346#ifdef MSTATS 347 nmalloc[size]--; 348#endif 349} 350 351/* 352 * When a program attempts "storage compaction" as mentioned in the 353 * old malloc man page, it realloc's an already freed block. Usually 354 * this is the last block it freed; occasionally it might be farther 355 * back. We have to search all the free lists for the block in order 356 * to determine its bucket: 1st we make one pass thru the lists 357 * checking only the first block in each; if that fails we search 358 * ``realloc_srchlen'' blocks in each list for a match (the variable 359 * is extern so the caller can modify it). If that fails we just copy 360 * however many bytes was given to realloc() and hope it's not huge. 361 */ 362int realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */ 363 364void * 365realloc(cp, nbytes) 366 void *cp; 367 size_t nbytes; 368{ 369 register u_int onb; 370 register int i; 371 union overhead *op; 372 char *res; 373 int was_alloced = 0; 374 375 if (cp == NULL) 376 return (malloc(nbytes)); 377 op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); 378 if (op->ov_magic == MAGIC) { 379 was_alloced++; 380 i = op->ov_index; 381 } else { 382 /* 383 * Already free, doing "compaction". 384 * 385 * Search for the old block of memory on the 386 * free list. First, check the most common 387 * case (last element free'd), then (this failing) 388 * the last ``realloc_srchlen'' items free'd. 389 * If all lookups fail, then assume the size of 390 * the memory block being realloc'd is the 391 * largest possible (so that all "nbytes" of new 392 * memory are copied into). Note that this could cause 393 * a memory fault if the old area was tiny, and the moon 394 * is gibbous. However, that is very unlikely. 395 */ 396 if ((i = findbucket(op, 1)) < 0 && 397 (i = findbucket(op, realloc_srchlen)) < 0) 398 i = NBUCKETS; 399 } 400 onb = 1 << (i + 3); 401 if (onb < (u_int)pagesz) 402 onb -= sizeof (*op) + RSLOP; 403 else 404 onb += pagesz - sizeof (*op) - RSLOP; 405 /* avoid the copy if same size block */ 406 if (was_alloced) { 407 if (i) { 408 i = 1 << (i + 2); 409 if (i < pagesz) 410 i -= sizeof (*op) + RSLOP; 411 else 412 i += pagesz - sizeof (*op) - RSLOP; 413 } 414 if (nbytes <= onb && nbytes > (size_t)i) { 415#ifdef RCHECK 416 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 417 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 418#endif 419 return(cp); 420 } else 421 free(cp); 422 } 423 if ((res = malloc(nbytes)) == NULL) 424 return (NULL); 425 if (cp != res) /* common optimization if "compacting" */ 426 bcopy(cp, res, (nbytes < onb) ? nbytes : onb); 427 return (res); 428} 429 430/* 431 * Search ``srchlen'' elements of each free list for a block whose 432 * header starts at ``freep''. If srchlen is -1 search the whole list. 433 * Return bucket number, or -1 if not found. 434 */ 435static int 436findbucket(freep, srchlen) 437 union overhead *freep; 438 int srchlen; 439{ 440 register union overhead *p; 441 register int i, j; 442 443 for (i = 0; i < NBUCKETS; i++) { 444 j = 0; 445 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) { 446 if (p == freep) 447 return (i); 448 j++; 449 } 450 } 451 return (-1); 452} 453 454#ifdef MSTATS 455/* 456 * mstats - print out statistics about malloc 457 * 458 * Prints two lines of numbers, one showing the length of the free list 459 * for each size category, the second showing the number of mallocs - 460 * frees for each size category. 461 */ 462mstats(s) 463 char *s; 464{ 465 register int i, j; 466 register union overhead *p; 467 int totfree = 0, 468 totused = 0; 469 470 fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s); 471 for (i = 0; i < NBUCKETS; i++) { 472 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++) 473 ; 474 fprintf(stderr, " %d", j); 475 totfree += j * (1 << (i + 3)); 476 } 477 fprintf(stderr, "\nused:\t"); 478 for (i = 0; i < NBUCKETS; i++) { 479 fprintf(stderr, " %d", nmalloc[i]); 480 totused += nmalloc[i] * (1 << (i + 3)); 481 } 482 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n", 483 totused, totfree); 484} 485#endif 486 487 488static int 489morepages(n) 490int n; 491{ 492 int fd = -1; 493 int offset; 494 495#ifdef NEED_DEV_ZERO 496 fd = open(_PATH_DEVZERO, O_RDWR, 0); 497 if (fd == -1) 498 perror(_PATH_DEVZERO); 499#endif 500 501 if (pagepool_end - pagepool_start > pagesz) { 502 caddr_t addr = (caddr_t) 503 (((long)pagepool_start + pagesz - 1) & ~(pagesz - 1)); 504 if (munmap(addr, pagepool_end - addr) != 0) 505 rtld_fdprintf(STDERR_FILENO, "morepages: munmap %p", 506 addr); 507 } 508 509 offset = (long)pagepool_start - ((long)pagepool_start & ~(pagesz - 1)); 510 511 if ((pagepool_start = mmap(0, n * pagesz, 512 PROT_READ|PROT_WRITE, 513 MAP_ANON|MAP_COPY, fd, 0)) == (caddr_t)-1) { 514 rtld_printf("Cannot map anonymous memory\n"); 515 return 0; 516 } 517 pagepool_end = pagepool_start + n * pagesz; 518 pagepool_start += offset; 519 520#ifdef NEED_DEV_ZERO 521 close(fd); 522#endif 523 return n; 524} 525