malloc.c revision 281452
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 281452 2015-04-12 06:43:13Z kib $"; 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__) 141 142/* 143 * The array of supported page sizes is provided by the user, i.e., the 144 * program that calls this storage allocator. That program must initialize 145 * the array before making its first call to allocate storage. The array 146 * must contain at least one page size. The page sizes must be stored in 147 * increasing order. 148 */ 149extern size_t *pagesizes; 150 151void * 152malloc(nbytes) 153 size_t nbytes; 154{ 155 register union overhead *op; 156 register int bucket; 157 register long n; 158 register unsigned amt; 159 160 /* 161 * First time malloc is called, setup page size and 162 * align break pointer so all data will be page aligned. 163 */ 164 if (pagesz == 0) { 165 pagesz = n = pagesizes[0]; 166 if (morepages(NPOOLPAGES) == 0) 167 return NULL; 168 op = (union overhead *)(pagepool_start); 169 n = n - sizeof (*op) - ((long)op & (n - 1)); 170 if (n < 0) 171 n += pagesz; 172 if (n) { 173 pagepool_start += n; 174 } 175 bucket = 0; 176 amt = 8; 177 while ((unsigned)pagesz > amt) { 178 amt <<= 1; 179 bucket++; 180 } 181 pagebucket = bucket; 182 } 183 /* 184 * Convert amount of memory requested into closest block size 185 * stored in hash buckets which satisfies request. 186 * Account for space used per block for accounting. 187 */ 188 if (nbytes <= (unsigned long)(n = pagesz - sizeof (*op) - RSLOP)) { 189#ifndef RCHECK 190 amt = 8; /* size of first bucket */ 191 bucket = 0; 192#else 193 amt = 16; /* size of first bucket */ 194 bucket = 1; 195#endif 196 n = -(sizeof (*op) + RSLOP); 197 } else { 198 amt = pagesz; 199 bucket = pagebucket; 200 } 201 while (nbytes > amt + n) { 202 amt <<= 1; 203 if (amt == 0) 204 return (NULL); 205 bucket++; 206 } 207 /* 208 * If nothing in hash bucket right now, 209 * request more memory from the system. 210 */ 211 if ((op = nextf[bucket]) == NULL) { 212 morecore(bucket); 213 if ((op = nextf[bucket]) == NULL) 214 return (NULL); 215 } 216 /* remove from linked list */ 217 nextf[bucket] = op->ov_next; 218 op->ov_magic = MAGIC; 219 op->ov_index = bucket; 220#ifdef MSTATS 221 nmalloc[bucket]++; 222#endif 223#ifdef RCHECK 224 /* 225 * Record allocated size of block and 226 * bound space with magic numbers. 227 */ 228 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 229 op->ov_rmagic = RMAGIC; 230 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 231#endif 232 return ((char *)(op + 1)); 233} 234 235void * 236calloc(size_t num, size_t size) 237{ 238 void *ret; 239 240 if (size != 0 && (num * size) / size != num) { 241 /* size_t overflow. */ 242 return (NULL); 243 } 244 245 if ((ret = malloc(num * size)) != NULL) 246 memset(ret, 0, num * size); 247 248 return (ret); 249} 250 251/* 252 * Allocate more memory to the indicated bucket. 253 */ 254static void 255morecore(bucket) 256 int bucket; 257{ 258 register union overhead *op; 259 register int sz; /* size of desired block */ 260 int amt; /* amount to allocate */ 261 int nblks; /* how many blocks we get */ 262 263 /* 264 * sbrk_size <= 0 only for big, FLUFFY, requests (about 265 * 2^30 bytes on a VAX, I think) or for a negative arg. 266 */ 267 sz = 1 << (bucket + 3); 268#ifdef MALLOC_DEBUG 269 ASSERT(sz > 0); 270#else 271 if (sz <= 0) 272 return; 273#endif 274 if (sz < pagesz) { 275 amt = pagesz; 276 nblks = amt / sz; 277 } else { 278 amt = sz + pagesz; 279 nblks = 1; 280 } 281 if (amt > pagepool_end - pagepool_start) 282 if (morepages(amt/pagesz + NPOOLPAGES) == 0) 283 return; 284 op = (union overhead *)pagepool_start; 285 pagepool_start += amt; 286 287 /* 288 * Add new memory allocated to that on 289 * free list for this hash bucket. 290 */ 291 nextf[bucket] = op; 292 while (--nblks > 0) { 293 op->ov_next = (union overhead *)((caddr_t)op + sz); 294 op = (union overhead *)((caddr_t)op + sz); 295 } 296} 297 298void 299free(cp) 300 void *cp; 301{ 302 register int size; 303 register union overhead *op; 304 305 if (cp == NULL) 306 return; 307 op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); 308#ifdef MALLOC_DEBUG 309 ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */ 310#else 311 if (op->ov_magic != MAGIC) 312 return; /* sanity */ 313#endif 314#ifdef RCHECK 315 ASSERT(op->ov_rmagic == RMAGIC); 316 ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC); 317#endif 318 size = op->ov_index; 319 ASSERT(size < NBUCKETS); 320 op->ov_next = nextf[size]; /* also clobbers ov_magic */ 321 nextf[size] = op; 322#ifdef MSTATS 323 nmalloc[size]--; 324#endif 325} 326 327/* 328 * When a program attempts "storage compaction" as mentioned in the 329 * old malloc man page, it realloc's an already freed block. Usually 330 * this is the last block it freed; occasionally it might be farther 331 * back. We have to search all the free lists for the block in order 332 * to determine its bucket: 1st we make one pass thru the lists 333 * checking only the first block in each; if that fails we search 334 * ``realloc_srchlen'' blocks in each list for a match (the variable 335 * is extern so the caller can modify it). If that fails we just copy 336 * however many bytes was given to realloc() and hope it's not huge. 337 */ 338int realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */ 339 340void * 341realloc(cp, nbytes) 342 void *cp; 343 size_t nbytes; 344{ 345 register u_int onb; 346 register int i; 347 union overhead *op; 348 char *res; 349 int was_alloced = 0; 350 351 if (cp == NULL) 352 return (malloc(nbytes)); 353 op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); 354 if (op->ov_magic == MAGIC) { 355 was_alloced++; 356 i = op->ov_index; 357 } else { 358 /* 359 * Already free, doing "compaction". 360 * 361 * Search for the old block of memory on the 362 * free list. First, check the most common 363 * case (last element free'd), then (this failing) 364 * the last ``realloc_srchlen'' items free'd. 365 * If all lookups fail, then assume the size of 366 * the memory block being realloc'd is the 367 * largest possible (so that all "nbytes" of new 368 * memory are copied into). Note that this could cause 369 * a memory fault if the old area was tiny, and the moon 370 * is gibbous. However, that is very unlikely. 371 */ 372 if ((i = findbucket(op, 1)) < 0 && 373 (i = findbucket(op, realloc_srchlen)) < 0) 374 i = NBUCKETS; 375 } 376 onb = 1 << (i + 3); 377 if (onb < (u_int)pagesz) 378 onb -= sizeof (*op) + RSLOP; 379 else 380 onb += pagesz - sizeof (*op) - RSLOP; 381 /* avoid the copy if same size block */ 382 if (was_alloced) { 383 if (i) { 384 i = 1 << (i + 2); 385 if (i < pagesz) 386 i -= sizeof (*op) + RSLOP; 387 else 388 i += pagesz - sizeof (*op) - RSLOP; 389 } 390 if (nbytes <= onb && nbytes > (size_t)i) { 391#ifdef RCHECK 392 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 393 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 394#endif 395 return(cp); 396 } else 397 free(cp); 398 } 399 if ((res = malloc(nbytes)) == NULL) 400 return (NULL); 401 if (cp != res) /* common optimization if "compacting" */ 402 bcopy(cp, res, (nbytes < onb) ? nbytes : onb); 403 return (res); 404} 405 406/* 407 * Search ``srchlen'' elements of each free list for a block whose 408 * header starts at ``freep''. If srchlen is -1 search the whole list. 409 * Return bucket number, or -1 if not found. 410 */ 411static int 412findbucket(freep, srchlen) 413 union overhead *freep; 414 int srchlen; 415{ 416 register union overhead *p; 417 register int i, j; 418 419 for (i = 0; i < NBUCKETS; i++) { 420 j = 0; 421 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) { 422 if (p == freep) 423 return (i); 424 j++; 425 } 426 } 427 return (-1); 428} 429 430#ifdef MSTATS 431/* 432 * mstats - print out statistics about malloc 433 * 434 * Prints two lines of numbers, one showing the length of the free list 435 * for each size category, the second showing the number of mallocs - 436 * frees for each size category. 437 */ 438mstats(s) 439 char *s; 440{ 441 register int i, j; 442 register union overhead *p; 443 int totfree = 0, 444 totused = 0; 445 446 fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s); 447 for (i = 0; i < NBUCKETS; i++) { 448 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++) 449 ; 450 fprintf(stderr, " %d", j); 451 totfree += j * (1 << (i + 3)); 452 } 453 fprintf(stderr, "\nused:\t"); 454 for (i = 0; i < NBUCKETS; i++) { 455 fprintf(stderr, " %d", nmalloc[i]); 456 totused += nmalloc[i] * (1 << (i + 3)); 457 } 458 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n", 459 totused, totfree); 460} 461#endif 462 463 464static int 465morepages(n) 466int n; 467{ 468 int fd = -1; 469 int offset; 470 471 if (pagepool_end - pagepool_start > pagesz) { 472 caddr_t addr = (caddr_t) 473 (((long)pagepool_start + pagesz - 1) & ~(pagesz - 1)); 474 if (munmap(addr, pagepool_end - addr) != 0) 475 rtld_fdprintf(STDERR_FILENO, "morepages: munmap %p", 476 addr); 477 } 478 479 offset = (long)pagepool_start - ((long)pagepool_start & ~(pagesz - 1)); 480 481 if ((pagepool_start = mmap(0, n * pagesz, 482 PROT_READ|PROT_WRITE, 483 MAP_ANON|MAP_COPY, fd, 0)) == (caddr_t)-1) { 484 rtld_printf("Cannot map anonymous memory\n"); 485 return 0; 486 } 487 pagepool_end = pagepool_start + n * pagesz; 488 pagepool_start += offset; 489 490 return n; 491} 492