malloc.c revision 262435
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. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 */ 29 30#if defined(LIBC_SCCS) && !defined(lint) 31/*static char *sccsid = "from: @(#)malloc.c 5.11 (Berkeley) 2/23/91";*/ 32static char *rcsid = "$FreeBSD: stable/10/libexec/rtld-elf/malloc.c 262435 2014-02-24 08:21:49Z brueffer $"; 33#endif /* LIBC_SCCS and not lint */ 34 35/* 36 * malloc.c (Caltech) 2/21/82 37 * Chris Kingsley, kingsley@cit-20. 38 * 39 * This is a very fast storage allocator. It allocates blocks of a small 40 * number of different sizes, and keeps free lists of each size. Blocks that 41 * don't exactly fit are passed up to the next larger size. In this 42 * implementation, the available sizes are 2^n-4 (or 2^n-10) bytes long. 43 * This is designed for use in a virtual memory environment. 44 */ 45 46#include <sys/types.h> 47#include <sys/sysctl.h> 48#include <paths.h> 49#include <stdarg.h> 50#include <stddef.h> 51#include <stdio.h> 52#include <stdlib.h> 53#include <string.h> 54#include <unistd.h> 55#include <sys/param.h> 56#include <sys/mman.h> 57#include "rtld_printf.h" 58 59static void morecore(); 60static int findbucket(); 61 62/* 63 * Pre-allocate mmap'ed pages 64 */ 65#define NPOOLPAGES (32*1024/pagesz) 66static caddr_t pagepool_start, pagepool_end; 67static int morepages(); 68 69/* 70 * The overhead on a block is at least 4 bytes. When free, this space 71 * contains a pointer to the next free block, and the bottom two bits must 72 * be zero. When in use, the first byte is set to MAGIC, and the second 73 * byte is the size index. The remaining bytes are for alignment. 74 * If range checking is enabled then a second word holds the size of the 75 * requested block, less 1, rounded up to a multiple of sizeof(RMAGIC). 76 * The order of elements is critical: ov_magic must overlay the low order 77 * bits of ov_next, and ov_magic can not be a valid ov_next bit pattern. 78 */ 79union overhead { 80 union overhead *ov_next; /* when free */ 81 struct { 82 u_char ovu_magic; /* magic number */ 83 u_char ovu_index; /* bucket # */ 84#ifdef RCHECK 85 u_short ovu_rmagic; /* range magic number */ 86 u_int ovu_size; /* actual block size */ 87#endif 88 } ovu; 89#define ov_magic ovu.ovu_magic 90#define ov_index ovu.ovu_index 91#define ov_rmagic ovu.ovu_rmagic 92#define ov_size ovu.ovu_size 93}; 94 95#define MAGIC 0xef /* magic # on accounting info */ 96#define RMAGIC 0x5555 /* magic # on range info */ 97 98#ifdef RCHECK 99#define RSLOP sizeof (u_short) 100#else 101#define RSLOP 0 102#endif 103 104/* 105 * nextf[i] is the pointer to the next free block of size 2^(i+3). The 106 * smallest allocatable block is 8 bytes. The overhead information 107 * precedes the data area returned to the user. 108 */ 109#define NBUCKETS 30 110static union overhead *nextf[NBUCKETS]; 111 112static int pagesz; /* page size */ 113static int pagebucket; /* page size bucket */ 114 115#ifdef MSTATS 116/* 117 * nmalloc[i] is the difference between the number of mallocs and frees 118 * for a given block size. 119 */ 120static u_int nmalloc[NBUCKETS]; 121#include <stdio.h> 122#endif 123 124#if defined(MALLOC_DEBUG) || defined(RCHECK) 125#define ASSERT(p) if (!(p)) botch("p") 126#include <stdio.h> 127static void 128botch(s) 129 char *s; 130{ 131 fprintf(stderr, "\r\nassertion botched: %s\r\n", s); 132 (void) fflush(stderr); /* just in case user buffered it */ 133 abort(); 134} 135#else 136#define ASSERT(p) 137#endif 138 139/* Debugging stuff */ 140#define TRACE() rtld_printf("TRACE %s:%d\n", __FILE__, __LINE__) 141 142extern int pagesize; 143 144static int 145rtld_getpagesize(void) 146{ 147 int mib[2]; 148 size_t size; 149 150 if (pagesize != 0) 151 return (pagesize); 152 153 mib[0] = CTL_HW; 154 mib[1] = HW_PAGESIZE; 155 size = sizeof(pagesize); 156 if (sysctl(mib, 2, &pagesize, &size, NULL, 0) == -1) 157 return (-1); 158 return (pagesize); 159 160} 161 162void * 163malloc(nbytes) 164 size_t nbytes; 165{ 166 register union overhead *op; 167 register int bucket; 168 register long n; 169 register unsigned amt; 170 171 /* 172 * First time malloc is called, setup page size and 173 * align break pointer so all data will be page aligned. 174 */ 175 if (pagesz == 0) { 176 pagesz = n = rtld_getpagesize(); 177 if (morepages(NPOOLPAGES) == 0) 178 return NULL; 179 op = (union overhead *)(pagepool_start); 180 n = n - sizeof (*op) - ((long)op & (n - 1)); 181 if (n < 0) 182 n += pagesz; 183 if (n) { 184 pagepool_start += n; 185 } 186 bucket = 0; 187 amt = 8; 188 while ((unsigned)pagesz > amt) { 189 amt <<= 1; 190 bucket++; 191 } 192 pagebucket = bucket; 193 } 194 /* 195 * Convert amount of memory requested into closest block size 196 * stored in hash buckets which satisfies request. 197 * Account for space used per block for accounting. 198 */ 199 if (nbytes <= (unsigned long)(n = pagesz - sizeof (*op) - RSLOP)) { 200#ifndef RCHECK 201 amt = 8; /* size of first bucket */ 202 bucket = 0; 203#else 204 amt = 16; /* size of first bucket */ 205 bucket = 1; 206#endif 207 n = -(sizeof (*op) + RSLOP); 208 } else { 209 amt = pagesz; 210 bucket = pagebucket; 211 } 212 while (nbytes > amt + n) { 213 amt <<= 1; 214 if (amt == 0) 215 return (NULL); 216 bucket++; 217 } 218 /* 219 * If nothing in hash bucket right now, 220 * request more memory from the system. 221 */ 222 if ((op = nextf[bucket]) == NULL) { 223 morecore(bucket); 224 if ((op = nextf[bucket]) == NULL) 225 return (NULL); 226 } 227 /* remove from linked list */ 228 nextf[bucket] = op->ov_next; 229 op->ov_magic = MAGIC; 230 op->ov_index = bucket; 231#ifdef MSTATS 232 nmalloc[bucket]++; 233#endif 234#ifdef RCHECK 235 /* 236 * Record allocated size of block and 237 * bound space with magic numbers. 238 */ 239 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 240 op->ov_rmagic = RMAGIC; 241 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 242#endif 243 return ((char *)(op + 1)); 244} 245 246void * 247calloc(size_t num, size_t size) 248{ 249 void *ret; 250 251 if (size != 0 && (num * size) / size != num) { 252 /* size_t overflow. */ 253 return (NULL); 254 } 255 256 if ((ret = malloc(num * size)) != NULL) 257 memset(ret, 0, num * size); 258 259 return (ret); 260} 261 262/* 263 * Allocate more memory to the indicated bucket. 264 */ 265static void 266morecore(bucket) 267 int bucket; 268{ 269 register union overhead *op; 270 register int sz; /* size of desired block */ 271 int amt; /* amount to allocate */ 272 int nblks; /* how many blocks we get */ 273 274 /* 275 * sbrk_size <= 0 only for big, FLUFFY, requests (about 276 * 2^30 bytes on a VAX, I think) or for a negative arg. 277 */ 278 sz = 1 << (bucket + 3); 279#ifdef MALLOC_DEBUG 280 ASSERT(sz > 0); 281#else 282 if (sz <= 0) 283 return; 284#endif 285 if (sz < pagesz) { 286 amt = pagesz; 287 nblks = amt / sz; 288 } else { 289 amt = sz + pagesz; 290 nblks = 1; 291 } 292 if (amt > pagepool_end - pagepool_start) 293 if (morepages(amt/pagesz + NPOOLPAGES) == 0) 294 return; 295 op = (union overhead *)pagepool_start; 296 pagepool_start += amt; 297 298 /* 299 * Add new memory allocated to that on 300 * free list for this hash bucket. 301 */ 302 nextf[bucket] = op; 303 while (--nblks > 0) { 304 op->ov_next = (union overhead *)((caddr_t)op + sz); 305 op = (union overhead *)((caddr_t)op + sz); 306 } 307} 308 309void 310free(cp) 311 void *cp; 312{ 313 register int size; 314 register union overhead *op; 315 316 if (cp == NULL) 317 return; 318 op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); 319#ifdef MALLOC_DEBUG 320 ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */ 321#else 322 if (op->ov_magic != MAGIC) 323 return; /* sanity */ 324#endif 325#ifdef RCHECK 326 ASSERT(op->ov_rmagic == RMAGIC); 327 ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC); 328#endif 329 size = op->ov_index; 330 ASSERT(size < NBUCKETS); 331 op->ov_next = nextf[size]; /* also clobbers ov_magic */ 332 nextf[size] = op; 333#ifdef MSTATS 334 nmalloc[size]--; 335#endif 336} 337 338/* 339 * When a program attempts "storage compaction" as mentioned in the 340 * old malloc man page, it realloc's an already freed block. Usually 341 * this is the last block it freed; occasionally it might be farther 342 * back. We have to search all the free lists for the block in order 343 * to determine its bucket: 1st we make one pass thru the lists 344 * checking only the first block in each; if that fails we search 345 * ``realloc_srchlen'' blocks in each list for a match (the variable 346 * is extern so the caller can modify it). If that fails we just copy 347 * however many bytes was given to realloc() and hope it's not huge. 348 */ 349int realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */ 350 351void * 352realloc(cp, nbytes) 353 void *cp; 354 size_t nbytes; 355{ 356 register u_int onb; 357 register int i; 358 union overhead *op; 359 char *res; 360 int was_alloced = 0; 361 362 if (cp == NULL) 363 return (malloc(nbytes)); 364 op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); 365 if (op->ov_magic == MAGIC) { 366 was_alloced++; 367 i = op->ov_index; 368 } else { 369 /* 370 * Already free, doing "compaction". 371 * 372 * Search for the old block of memory on the 373 * free list. First, check the most common 374 * case (last element free'd), then (this failing) 375 * the last ``realloc_srchlen'' items free'd. 376 * If all lookups fail, then assume the size of 377 * the memory block being realloc'd is the 378 * largest possible (so that all "nbytes" of new 379 * memory are copied into). Note that this could cause 380 * a memory fault if the old area was tiny, and the moon 381 * is gibbous. However, that is very unlikely. 382 */ 383 if ((i = findbucket(op, 1)) < 0 && 384 (i = findbucket(op, realloc_srchlen)) < 0) 385 i = NBUCKETS; 386 } 387 onb = 1 << (i + 3); 388 if (onb < (u_int)pagesz) 389 onb -= sizeof (*op) + RSLOP; 390 else 391 onb += pagesz - sizeof (*op) - RSLOP; 392 /* avoid the copy if same size block */ 393 if (was_alloced) { 394 if (i) { 395 i = 1 << (i + 2); 396 if (i < pagesz) 397 i -= sizeof (*op) + RSLOP; 398 else 399 i += pagesz - sizeof (*op) - RSLOP; 400 } 401 if (nbytes <= onb && nbytes > (size_t)i) { 402#ifdef RCHECK 403 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 404 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 405#endif 406 return(cp); 407 } else 408 free(cp); 409 } 410 if ((res = malloc(nbytes)) == NULL) 411 return (NULL); 412 if (cp != res) /* common optimization if "compacting" */ 413 bcopy(cp, res, (nbytes < onb) ? nbytes : onb); 414 return (res); 415} 416 417/* 418 * Search ``srchlen'' elements of each free list for a block whose 419 * header starts at ``freep''. If srchlen is -1 search the whole list. 420 * Return bucket number, or -1 if not found. 421 */ 422static int 423findbucket(freep, srchlen) 424 union overhead *freep; 425 int srchlen; 426{ 427 register union overhead *p; 428 register int i, j; 429 430 for (i = 0; i < NBUCKETS; i++) { 431 j = 0; 432 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) { 433 if (p == freep) 434 return (i); 435 j++; 436 } 437 } 438 return (-1); 439} 440 441#ifdef MSTATS 442/* 443 * mstats - print out statistics about malloc 444 * 445 * Prints two lines of numbers, one showing the length of the free list 446 * for each size category, the second showing the number of mallocs - 447 * frees for each size category. 448 */ 449mstats(s) 450 char *s; 451{ 452 register int i, j; 453 register union overhead *p; 454 int totfree = 0, 455 totused = 0; 456 457 fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s); 458 for (i = 0; i < NBUCKETS; i++) { 459 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++) 460 ; 461 fprintf(stderr, " %d", j); 462 totfree += j * (1 << (i + 3)); 463 } 464 fprintf(stderr, "\nused:\t"); 465 for (i = 0; i < NBUCKETS; i++) { 466 fprintf(stderr, " %d", nmalloc[i]); 467 totused += nmalloc[i] * (1 << (i + 3)); 468 } 469 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n", 470 totused, totfree); 471} 472#endif 473 474 475static int 476morepages(n) 477int n; 478{ 479 int fd = -1; 480 int offset; 481 482 if (pagepool_end - pagepool_start > pagesz) { 483 caddr_t addr = (caddr_t) 484 (((long)pagepool_start + pagesz - 1) & ~(pagesz - 1)); 485 if (munmap(addr, pagepool_end - addr) != 0) 486 rtld_fdprintf(STDERR_FILENO, "morepages: munmap %p", 487 addr); 488 } 489 490 offset = (long)pagepool_start - ((long)pagepool_start & ~(pagesz - 1)); 491 492 if ((pagepool_start = mmap(0, n * pagesz, 493 PROT_READ|PROT_WRITE, 494 MAP_ANON|MAP_COPY, fd, 0)) == (caddr_t)-1) { 495 rtld_printf("Cannot map anonymous memory\n"); 496 return 0; 497 } 498 pagepool_end = pagepool_start + n * pagesz; 499 pagepool_start += offset; 500 501 return n; 502} 503