malloc.c revision 211413
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 211413 2010-08-17 09:05:39Z 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 <err.h> 53#include <paths.h> 54#include <stdarg.h> 55#include <stddef.h> 56#include <stdio.h> 57#include <stdlib.h> 58#include <string.h> 59#include <unistd.h> 60#include <sys/param.h> 61#include <sys/mman.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 */ 153static void xprintf(const char *, ...); 154#define TRACE() xprintf("TRACE %s:%d\n", __FILE__, __LINE__) 155 156extern int pagesize; 157 158static int 159rtld_getpagesize(void) 160{ 161 int mib[2]; 162 size_t size; 163 164 if (pagesize != 0) 165 return (pagesize); 166 167 mib[0] = CTL_HW; 168 mib[1] = HW_PAGESIZE; 169 size = sizeof(pagesize); 170 if (sysctl(mib, 2, &pagesize, &size, NULL, 0) == -1) 171 return (-1); 172 return (pagesize); 173 174} 175 176void * 177malloc(nbytes) 178 size_t nbytes; 179{ 180 register union overhead *op; 181 register int bucket; 182 register long n; 183 register unsigned amt; 184 185 /* 186 * First time malloc is called, setup page size and 187 * align break pointer so all data will be page aligned. 188 */ 189 if (pagesz == 0) { 190 pagesz = n = rtld_getpagesize(); 191 if (morepages(NPOOLPAGES) == 0) 192 return NULL; 193 op = (union overhead *)(pagepool_start); 194 n = n - sizeof (*op) - ((long)op & (n - 1)); 195 if (n < 0) 196 n += pagesz; 197 if (n) { 198 pagepool_start += n; 199 } 200 bucket = 0; 201 amt = 8; 202 while ((unsigned)pagesz > amt) { 203 amt <<= 1; 204 bucket++; 205 } 206 pagebucket = bucket; 207 } 208 /* 209 * Convert amount of memory requested into closest block size 210 * stored in hash buckets which satisfies request. 211 * Account for space used per block for accounting. 212 */ 213 if (nbytes <= (unsigned long)(n = pagesz - sizeof (*op) - RSLOP)) { 214#ifndef RCHECK 215 amt = 8; /* size of first bucket */ 216 bucket = 0; 217#else 218 amt = 16; /* size of first bucket */ 219 bucket = 1; 220#endif 221 n = -(sizeof (*op) + RSLOP); 222 } else { 223 amt = pagesz; 224 bucket = pagebucket; 225 } 226 while (nbytes > amt + n) { 227 amt <<= 1; 228 if (amt == 0) 229 return (NULL); 230 bucket++; 231 } 232 /* 233 * If nothing in hash bucket right now, 234 * request more memory from the system. 235 */ 236 if ((op = nextf[bucket]) == NULL) { 237 morecore(bucket); 238 if ((op = nextf[bucket]) == NULL) 239 return (NULL); 240 } 241 /* remove from linked list */ 242 nextf[bucket] = op->ov_next; 243 op->ov_magic = MAGIC; 244 op->ov_index = bucket; 245#ifdef MSTATS 246 nmalloc[bucket]++; 247#endif 248#ifdef RCHECK 249 /* 250 * Record allocated size of block and 251 * bound space with magic numbers. 252 */ 253 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 254 op->ov_rmagic = RMAGIC; 255 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 256#endif 257 return ((char *)(op + 1)); 258} 259 260void * 261calloc(size_t num, size_t size) 262{ 263 void *ret; 264 265 if (size != 0 && (num * size) / size != num) { 266 /* size_t overflow. */ 267 return (NULL); 268 } 269 270 if ((ret = malloc(num * size)) != NULL) 271 memset(ret, 0, num * size); 272 273 return (ret); 274} 275 276/* 277 * Allocate more memory to the indicated bucket. 278 */ 279static void 280morecore(bucket) 281 int bucket; 282{ 283 register union overhead *op; 284 register int sz; /* size of desired block */ 285 int amt; /* amount to allocate */ 286 int nblks; /* how many blocks we get */ 287 288 /* 289 * sbrk_size <= 0 only for big, FLUFFY, requests (about 290 * 2^30 bytes on a VAX, I think) or for a negative arg. 291 */ 292 sz = 1 << (bucket + 3); 293#ifdef MALLOC_DEBUG 294 ASSERT(sz > 0); 295#else 296 if (sz <= 0) 297 return; 298#endif 299 if (sz < pagesz) { 300 amt = pagesz; 301 nblks = amt / sz; 302 } else { 303 amt = sz + pagesz; 304 nblks = 1; 305 } 306 if (amt > pagepool_end - pagepool_start) 307 if (morepages(amt/pagesz + NPOOLPAGES) == 0) 308 return; 309 op = (union overhead *)pagepool_start; 310 pagepool_start += amt; 311 312 /* 313 * Add new memory allocated to that on 314 * free list for this hash bucket. 315 */ 316 nextf[bucket] = op; 317 while (--nblks > 0) { 318 op->ov_next = (union overhead *)((caddr_t)op + sz); 319 op = (union overhead *)((caddr_t)op + sz); 320 } 321} 322 323void 324free(cp) 325 void *cp; 326{ 327 register int size; 328 register union overhead *op; 329 330 if (cp == NULL) 331 return; 332 op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); 333#ifdef MALLOC_DEBUG 334 ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */ 335#else 336 if (op->ov_magic != MAGIC) 337 return; /* sanity */ 338#endif 339#ifdef RCHECK 340 ASSERT(op->ov_rmagic == RMAGIC); 341 ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC); 342#endif 343 size = op->ov_index; 344 ASSERT(size < NBUCKETS); 345 op->ov_next = nextf[size]; /* also clobbers ov_magic */ 346 nextf[size] = op; 347#ifdef MSTATS 348 nmalloc[size]--; 349#endif 350} 351 352/* 353 * When a program attempts "storage compaction" as mentioned in the 354 * old malloc man page, it realloc's an already freed block. Usually 355 * this is the last block it freed; occasionally it might be farther 356 * back. We have to search all the free lists for the block in order 357 * to determine its bucket: 1st we make one pass thru the lists 358 * checking only the first block in each; if that fails we search 359 * ``realloc_srchlen'' blocks in each list for a match (the variable 360 * is extern so the caller can modify it). If that fails we just copy 361 * however many bytes was given to realloc() and hope it's not huge. 362 */ 363int realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */ 364 365void * 366realloc(cp, nbytes) 367 void *cp; 368 size_t nbytes; 369{ 370 register u_int onb; 371 register int i; 372 union overhead *op; 373 char *res; 374 int was_alloced = 0; 375 376 if (cp == NULL) 377 return (malloc(nbytes)); 378 op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); 379 if (op->ov_magic == MAGIC) { 380 was_alloced++; 381 i = op->ov_index; 382 } else { 383 /* 384 * Already free, doing "compaction". 385 * 386 * Search for the old block of memory on the 387 * free list. First, check the most common 388 * case (last element free'd), then (this failing) 389 * the last ``realloc_srchlen'' items free'd. 390 * If all lookups fail, then assume the size of 391 * the memory block being realloc'd is the 392 * largest possible (so that all "nbytes" of new 393 * memory are copied into). Note that this could cause 394 * a memory fault if the old area was tiny, and the moon 395 * is gibbous. However, that is very unlikely. 396 */ 397 if ((i = findbucket(op, 1)) < 0 && 398 (i = findbucket(op, realloc_srchlen)) < 0) 399 i = NBUCKETS; 400 } 401 onb = 1 << (i + 3); 402 if (onb < (u_int)pagesz) 403 onb -= sizeof (*op) + RSLOP; 404 else 405 onb += pagesz - sizeof (*op) - RSLOP; 406 /* avoid the copy if same size block */ 407 if (was_alloced) { 408 if (i) { 409 i = 1 << (i + 2); 410 if (i < pagesz) 411 i -= sizeof (*op) + RSLOP; 412 else 413 i += pagesz - sizeof (*op) - RSLOP; 414 } 415 if (nbytes <= onb && nbytes > (size_t)i) { 416#ifdef RCHECK 417 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 418 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 419#endif 420 return(cp); 421 } else 422 free(cp); 423 } 424 if ((res = malloc(nbytes)) == NULL) 425 return (NULL); 426 if (cp != res) /* common optimization if "compacting" */ 427 bcopy(cp, res, (nbytes < onb) ? nbytes : onb); 428 return (res); 429} 430 431/* 432 * Search ``srchlen'' elements of each free list for a block whose 433 * header starts at ``freep''. If srchlen is -1 search the whole list. 434 * Return bucket number, or -1 if not found. 435 */ 436static int 437findbucket(freep, srchlen) 438 union overhead *freep; 439 int srchlen; 440{ 441 register union overhead *p; 442 register int i, j; 443 444 for (i = 0; i < NBUCKETS; i++) { 445 j = 0; 446 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) { 447 if (p == freep) 448 return (i); 449 j++; 450 } 451 } 452 return (-1); 453} 454 455#ifdef MSTATS 456/* 457 * mstats - print out statistics about malloc 458 * 459 * Prints two lines of numbers, one showing the length of the free list 460 * for each size category, the second showing the number of mallocs - 461 * frees for each size category. 462 */ 463mstats(s) 464 char *s; 465{ 466 register int i, j; 467 register union overhead *p; 468 int totfree = 0, 469 totused = 0; 470 471 fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s); 472 for (i = 0; i < NBUCKETS; i++) { 473 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++) 474 ; 475 fprintf(stderr, " %d", j); 476 totfree += j * (1 << (i + 3)); 477 } 478 fprintf(stderr, "\nused:\t"); 479 for (i = 0; i < NBUCKETS; i++) { 480 fprintf(stderr, " %d", nmalloc[i]); 481 totused += nmalloc[i] * (1 << (i + 3)); 482 } 483 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n", 484 totused, totfree); 485} 486#endif 487 488 489static int 490morepages(n) 491int n; 492{ 493 int fd = -1; 494 int offset; 495 496#ifdef NEED_DEV_ZERO 497 fd = open(_PATH_DEVZERO, O_RDWR, 0); 498 if (fd == -1) 499 perror(_PATH_DEVZERO); 500#endif 501 502 if (pagepool_end - pagepool_start > pagesz) { 503 caddr_t addr = (caddr_t) 504 (((long)pagepool_start + pagesz - 1) & ~(pagesz - 1)); 505 if (munmap(addr, pagepool_end - addr) != 0) 506 warn("morepages: munmap %p", 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 xprintf("Cannot map anonymous memory"); 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} 525 526/* 527 * Non-mallocing printf, for use by malloc itself. 528 */ 529static void 530xprintf(const char *fmt, ...) 531{ 532 char buf[256]; 533 va_list ap; 534 535 va_start(ap, fmt); 536 vsprintf(buf, fmt, ap); 537 (void)write(STDOUT_FILENO, buf, strlen(buf)); 538 va_end(ap); 539} 540