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