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(char *s) 126 { 127 fprintf(stderr, "\r\nassertion botched: %s\r\n", s); 128 (void) fflush(stderr); /* just in case user buffered it */ 129 abort(); 130 } 131 #else 132 #define ASSERT(p) 133 #endif 134 135 /* Debugging stuff */ 136 #define TRACE() rtld_printf("TRACE %s:%d\n", __FILE__, __LINE__) 137 138 void * 139 malloc(size_t nbytes) 140 { 141 register union overhead *op; 142 register int bucket; 143 register long n; 144 register unsigned amt; 145 146 /* 147 * First time malloc is called, setup page size and 148 * align break pointer so all data will be page aligned. 149 */ 150 if (pagesz == 0) { 151 pagesz = n = getpagesize(); 152 if (morepages(NPOOLPAGES) == 0) 153 return NULL; 154 op = (union overhead *)(pagepool_start); 155 n = n - sizeof (*op) - ((long)op & (n - 1)); 156 if (n < 0) 157 n += pagesz; 158 if (n) { 159 pagepool_start += n; 160 } 161 bucket = 0; 162 amt = 8; 163 while ((unsigned)pagesz > amt) { 164 amt <<= 1; 165 bucket++; 166 } 167 pagebucket = bucket; 168 } 169 /* 170 * Convert amount of memory requested into closest block size 171 * stored in hash buckets which satisfies request. 172 * Account for space used per block for accounting. 173 */ 174 if (nbytes <= (unsigned long)(n = pagesz - sizeof (*op) - RSLOP)) { 175 #ifndef RCHECK 176 amt = 8; /* size of first bucket */ 177 bucket = 0; 178 #else 179 amt = 16; /* size of first bucket */ 180 bucket = 1; 181 #endif 182 n = -(sizeof (*op) + RSLOP); 183 } else { 184 amt = pagesz; 185 bucket = pagebucket; 186 } 187 while (nbytes > amt + n) { 188 amt <<= 1; 189 if (amt == 0) 190 return (NULL); 191 bucket++; 192 } 193 /* 194 * If nothing in hash bucket right now, 195 * request more memory from the system. 196 */ 197 if ((op = nextf[bucket]) == NULL) { 198 morecore(bucket); 199 if ((op = nextf[bucket]) == NULL) 200 return (NULL); 201 } 202 /* remove from linked list */ 203 nextf[bucket] = op->ov_next; 204 op->ov_magic = MAGIC; 205 op->ov_index = bucket; 206 #ifdef MSTATS 207 nmalloc[bucket]++; 208 #endif 209 #ifdef RCHECK 210 /* 211 * Record allocated size of block and 212 * bound space with magic numbers. 213 */ 214 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 215 op->ov_rmagic = RMAGIC; 216 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 217 #endif 218 return ((char *)(op + 1)); 219 } 220 221 /* 222 * Used by rtld.c, if we don't override it here the calloc from 223 * libc may try to pull in the malloc/realloc/free from libc too. 224 */ 225 void * 226 calloc(size_t num, size_t size) 227 { 228 void *p; 229 230 size *= num; 231 if ((p = malloc(size)) != NULL) 232 bzero(p, size); 233 return(p); 234 } 235 236 /* 237 * Allocate more memory to the indicated bucket. 238 */ 239 static void 240 morecore(int bucket) 241 { 242 register union overhead *op; 243 register int sz; /* size of desired block */ 244 int amt; /* amount to allocate */ 245 int nblks; /* how many blocks we get */ 246 247 /* 248 * sbrk_size <= 0 only for big, FLUFFY, requests (about 249 * 2^30 bytes on a VAX, I think) or for a negative arg. 250 */ 251 sz = 1 << (bucket + 3); 252 #ifdef MALLOC_DEBUG 253 ASSERT(sz > 0); 254 #else 255 if (sz <= 0) 256 return; 257 #endif 258 if (sz < pagesz) { 259 amt = pagesz; 260 nblks = amt / sz; 261 } else { 262 amt = sz + pagesz; 263 nblks = 1; 264 } 265 if (amt > pagepool_end - pagepool_start) 266 if (morepages(amt/pagesz + NPOOLPAGES) == 0) 267 return; 268 op = (union overhead *)pagepool_start; 269 pagepool_start += amt; 270 271 /* 272 * Add new memory allocated to that on 273 * free list for this hash bucket. 274 */ 275 nextf[bucket] = op; 276 while (--nblks > 0) { 277 op->ov_next = (union overhead *)((caddr_t)op + sz); 278 op = (union overhead *)((caddr_t)op + sz); 279 } 280 } 281 282 void 283 free(void *cp) 284 { 285 register int size; 286 register union overhead *op; 287 288 if (cp == NULL) 289 return; 290 op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); 291 #ifdef MALLOC_DEBUG 292 ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */ 293 #else 294 if (op->ov_magic != MAGIC) 295 return; /* sanity */ 296 #endif 297 #ifdef RCHECK 298 ASSERT(op->ov_rmagic == RMAGIC); 299 ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC); 300 #endif 301 size = op->ov_index; 302 ASSERT(size < NBUCKETS); 303 op->ov_next = nextf[size]; /* also clobbers ov_magic */ 304 nextf[size] = op; 305 #ifdef MSTATS 306 nmalloc[size]--; 307 #endif 308 } 309 310 /* 311 * When a program attempts "storage compaction" as mentioned in the 312 * old malloc man page, it realloc's an already freed block. Usually 313 * this is the last block it freed; occasionally it might be farther 314 * back. We have to search all the free lists for the block in order 315 * to determine its bucket: 1st we make one pass thru the lists 316 * checking only the first block in each; if that fails we search 317 * ``realloc_srchlen'' blocks in each list for a match (the variable 318 * is extern so the caller can modify it). If that fails we just copy 319 * however many bytes was given to realloc() and hope it's not huge. 320 */ 321 int realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */ 322 323 void * 324 realloc(void *cp, size_t nbytes) 325 { 326 register u_int onb; 327 register int i; 328 union overhead *op; 329 char *res; 330 int was_alloced = 0; 331 332 if (cp == NULL) 333 return (malloc(nbytes)); 334 op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); 335 if (op->ov_magic == MAGIC) { 336 was_alloced++; 337 i = op->ov_index; 338 } else { 339 /* 340 * Already free, doing "compaction". 341 * 342 * Search for the old block of memory on the 343 * free list. First, check the most common 344 * case (last element free'd), then (this failing) 345 * the last ``realloc_srchlen'' items free'd. 346 * If all lookups fail, then assume the size of 347 * the memory block being realloc'd is the 348 * largest possible (so that all "nbytes" of new 349 * memory are copied into). Note that this could cause 350 * a memory fault if the old area was tiny, and the moon 351 * is gibbous. However, that is very unlikely. 352 */ 353 if ((i = findbucket(op, 1)) < 0 && 354 (i = findbucket(op, realloc_srchlen)) < 0) 355 i = NBUCKETS; 356 } 357 onb = 1 << (i + 3); 358 if (onb < (u_int)pagesz) 359 onb -= sizeof (*op) + RSLOP; 360 else 361 onb += pagesz - sizeof (*op) - RSLOP; 362 /* avoid the copy if same size block */ 363 if (was_alloced) { 364 if (i) { 365 i = 1 << (i + 2); 366 if (i < pagesz) 367 i -= sizeof (*op) + RSLOP; 368 else 369 i += pagesz - sizeof (*op) - RSLOP; 370 } 371 if (nbytes <= onb && nbytes > (size_t)i) { 372 #ifdef RCHECK 373 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 374 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 375 #endif 376 return(cp); 377 } else 378 free(cp); 379 } 380 if ((res = malloc(nbytes)) == NULL) 381 return (NULL); 382 if (cp != res) /* common optimization if "compacting" */ 383 bcopy(cp, res, (nbytes < onb) ? nbytes : onb); 384 return (res); 385 } 386 387 /* 388 * Search ``srchlen'' elements of each free list for a block whose 389 * header starts at ``freep''. If srchlen is -1 search the whole list. 390 * Return bucket number, or -1 if not found. 391 */ 392 static int 393 findbucket(union overhead *freep, int srchlen) 394 { 395 register union overhead *p; 396 register int i, j; 397 398 for (i = 0; i < NBUCKETS; i++) { 399 j = 0; 400 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) { 401 if (p == freep) 402 return (i); 403 j++; 404 } 405 } 406 return (-1); 407 } 408 409 #ifdef MSTATS 410 /* 411 * mstats - print out statistics about malloc 412 * 413 * Prints two lines of numbers, one showing the length of the free list 414 * for each size category, the second showing the number of mallocs - 415 * frees for each size category. 416 */ 417 void 418 mstats(char *s) 419 { 420 register int i, j; 421 register union overhead *p; 422 int totfree = 0, 423 totused = 0; 424 425 fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s); 426 for (i = 0; i < NBUCKETS; i++) { 427 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++) 428 ; 429 fprintf(stderr, " %d", j); 430 totfree += j * (1 << (i + 3)); 431 } 432 fprintf(stderr, "\nused:\t"); 433 for (i = 0; i < NBUCKETS; i++) { 434 fprintf(stderr, " %d", nmalloc[i]); 435 totused += nmalloc[i] * (1 << (i + 3)); 436 } 437 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n", 438 totused, totfree); 439 } 440 #endif 441 442 443 static int 444 morepages(int n) 445 { 446 int fd = -1; 447 int offset; 448 449 if (pagepool_end - pagepool_start > pagesz) { 450 caddr_t addr = (caddr_t) 451 (((long)pagepool_start + pagesz - 1) & ~(pagesz - 1)); 452 if (munmap(addr, pagepool_end - addr) != 0) 453 rtld_fdprintf(STDERR_FILENO, "morepages: munmap %p", 454 addr); 455 } 456 457 offset = (long)pagepool_start - ((long)pagepool_start & ~(pagesz - 1)); 458 459 if ((pagepool_start = mmap(0, n * pagesz, 460 PROT_READ|PROT_WRITE, 461 MAP_ANON|MAP_COPY, fd, 0)) == (caddr_t)-1) { 462 rtld_printf("Cannot map anonymous memory\n"); 463 return 0; 464 } 465 pagepool_end = pagepool_start + n * pagesz; 466 pagepool_start += offset; 467 468 return n; 469 } 470