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[] = "@(#)malloc.c 5.11 (Berkeley) 2/23/91"; 36 #endif /* LIBC_SCCS and not lint */ 37 38 /* 39 * malloc.c (Caltech) 2/21/82 40 * Chris Kingsley, kingsley@cit-20. 41 * 42 * This is a very fast storage allocator. It allocates blocks of a small 43 * number of different sizes, and keeps free lists of each size. Blocks that 44 * don't exactly fit are passed up to the next larger size. In this 45 * implementation, the available sizes are 2^n-4 (or 2^n-10) bytes long. 46 * This is designed for use in a virtual memory environment. 47 */ 48 49 #include <sys/types.h> 50 #include <stdlib.h> 51 #include <string.h> 52 #include <unistd.h> 53 54 #define NULL 0 55 56 static void morecore(); 57 static int findbucket(); 58 59 /* 60 * The overhead on a block is at least 4 bytes. When free, this space 61 * contains a pointer to the next free block, and the bottom two bits must 62 * be zero. When in use, the first byte is set to MAGIC, and the second 63 * byte is the size index. The remaining bytes are for alignment. 64 * If range checking is enabled then a second word holds the size of the 65 * requested block, less 1, rounded up to a multiple of sizeof(RMAGIC). 66 * The order of elements is critical: ov_magic must overlay the low order 67 * bits of ov_next, and ov_magic can not be a valid ov_next bit pattern. 68 */ 69 union overhead { 70 union overhead *ov_next; /* when free */ 71 struct { 72 u_char ovu_magic; /* magic number */ 73 u_char ovu_index; /* bucket # */ 74 #ifdef RCHECK 75 u_short ovu_rmagic; /* range magic number */ 76 u_int ovu_size; /* actual block size */ 77 #endif 78 } ovu; 79 #define ov_magic ovu.ovu_magic 80 #define ov_index ovu.ovu_index 81 #define ov_rmagic ovu.ovu_rmagic 82 #define ov_size ovu.ovu_size 83 }; 84 85 #define MAGIC 0xef /* magic # on accounting info */ 86 #define RMAGIC 0x5555 /* magic # on range info */ 87 88 #ifdef RCHECK 89 #define RSLOP sizeof (u_short) 90 #else 91 #define RSLOP 0 92 #endif 93 94 /* 95 * nextf[i] is the pointer to the next free block of size 2^(i+3). The 96 * smallest allocatable block is 8 bytes. The overhead information 97 * precedes the data area returned to the user. 98 */ 99 #define NBUCKETS 30 100 static union overhead *nextf[NBUCKETS]; 101 extern char *sbrk(); 102 103 static int pagesz; /* page size */ 104 static int pagebucket; /* page size bucket */ 105 106 #ifdef MSTATS 107 /* 108 * nmalloc[i] is the difference between the number of mallocs and frees 109 * for a given block size. 110 */ 111 static u_int nmalloc[NBUCKETS]; 112 #include <stdio.h> 113 #endif 114 115 #if defined(DEBUG) || defined(RCHECK) 116 #define ASSERT(p) if (!(p)) botch("p") 117 #include <stdio.h> 118 static 119 botch(s) 120 char *s; 121 { 122 fprintf(stderr, "\r\nassertion botched: %s\r\n", s); 123 (void) fflush(stderr); /* just in case user buffered it */ 124 abort(); 125 } 126 #else 127 #define ASSERT(p) 128 #endif 129 130 void * 131 malloc(nbytes) 132 size_t nbytes; 133 { 134 register union overhead *op; 135 register int bucket, n; 136 register unsigned amt; 137 138 /* 139 * First time malloc is called, setup page size and 140 * align break pointer so all data will be page aligned. 141 */ 142 if (pagesz == 0) { 143 pagesz = n = getpagesize(); 144 op = (union overhead *)sbrk(0); 145 n = n - sizeof (*op) - ((int)op & (n - 1)); 146 if (n < 0) 147 n += pagesz; 148 if (n) { 149 if (sbrk(n) == (char *)-1) 150 return (NULL); 151 } 152 bucket = 0; 153 amt = 8; 154 while (pagesz > amt) { 155 amt <<= 1; 156 bucket++; 157 } 158 pagebucket = bucket; 159 } 160 /* 161 * Convert amount of memory requested into closest block size 162 * stored in hash buckets which satisfies request. 163 * Account for space used per block for accounting. 164 */ 165 if (nbytes <= (n = pagesz - sizeof (*op) - RSLOP)) { 166 #ifndef RCHECK 167 amt = 8; /* size of first bucket */ 168 bucket = 0; 169 #else 170 amt = 16; /* size of first bucket */ 171 bucket = 1; 172 #endif 173 n = -(sizeof (*op) + RSLOP); 174 } else { 175 amt = pagesz; 176 bucket = pagebucket; 177 } 178 while (nbytes > amt + n) { 179 amt <<= 1; 180 if (amt == 0) 181 return (NULL); 182 bucket++; 183 } 184 /* 185 * If nothing in hash bucket right now, 186 * request more memory from the system. 187 */ 188 if ((op = nextf[bucket]) == NULL) { 189 morecore(bucket); 190 if ((op = nextf[bucket]) == NULL) 191 return (NULL); 192 } 193 /* remove from linked list */ 194 nextf[bucket] = op->ov_next; 195 op->ov_magic = MAGIC; 196 op->ov_index = bucket; 197 #ifdef MSTATS 198 nmalloc[bucket]++; 199 #endif 200 #ifdef RCHECK 201 /* 202 * Record allocated size of block and 203 * bound space with magic numbers. 204 */ 205 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 206 op->ov_rmagic = RMAGIC; 207 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 208 #endif 209 return ((char *)(op + 1)); 210 } 211 212 /* 213 * Allocate more memory to the indicated bucket. 214 */ 215 static void 216 morecore(bucket) 217 int bucket; 218 { 219 register union overhead *op; 220 register int sz; /* size of desired block */ 221 int amt; /* amount to allocate */ 222 int nblks; /* how many blocks we get */ 223 224 /* 225 * sbrk_size <= 0 only for big, FLUFFY, requests (about 226 * 2^30 bytes on a VAX, I think) or for a negative arg. 227 */ 228 sz = 1 << (bucket + 3); 229 #ifdef DEBUG 230 ASSERT(sz > 0); 231 #else 232 if (sz <= 0) 233 return; 234 #endif 235 if (sz < pagesz) { 236 amt = pagesz; 237 nblks = amt / sz; 238 } else { 239 amt = sz + pagesz; 240 nblks = 1; 241 } 242 op = (union overhead *)sbrk(amt); 243 /* no more room! */ 244 if ((int)op == -1) 245 return; 246 /* 247 * Add new memory allocated to that on 248 * free list for this hash bucket. 249 */ 250 nextf[bucket] = op; 251 while (--nblks > 0) { 252 op->ov_next = (union overhead *)((caddr_t)op + sz); 253 op = (union overhead *)((caddr_t)op + sz); 254 } 255 } 256 257 void 258 free(cp) 259 void *cp; 260 { 261 register int size; 262 register union overhead *op; 263 264 if (cp == NULL) 265 return; 266 op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); 267 #ifdef DEBUG 268 ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */ 269 #else 270 if (op->ov_magic != MAGIC) 271 return; /* sanity */ 272 #endif 273 #ifdef RCHECK 274 ASSERT(op->ov_rmagic == RMAGIC); 275 ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC); 276 #endif 277 size = op->ov_index; 278 ASSERT(size < NBUCKETS); 279 op->ov_next = nextf[size]; /* also clobbers ov_magic */ 280 nextf[size] = op; 281 #ifdef MSTATS 282 nmalloc[size]--; 283 #endif 284 } 285 286 /* 287 * When a program attempts "storage compaction" as mentioned in the 288 * old malloc man page, it realloc's an already freed block. Usually 289 * this is the last block it freed; occasionally it might be farther 290 * back. We have to search all the free lists for the block in order 291 * to determine its bucket: 1st we make one pass thru the lists 292 * checking only the first block in each; if that fails we search 293 * ``realloc_srchlen'' blocks in each list for a match (the variable 294 * is extern so the caller can modify it). If that fails we just copy 295 * however many bytes was given to realloc() and hope it's not huge. 296 */ 297 int realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */ 298 299 void * 300 realloc(cp, nbytes) 301 void *cp; 302 size_t nbytes; 303 { 304 register u_int onb; 305 register int i; 306 union overhead *op; 307 char *res; 308 int was_alloced = 0; 309 310 if (cp == NULL) 311 return (malloc(nbytes)); 312 op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); 313 if (op->ov_magic == MAGIC) { 314 was_alloced++; 315 i = op->ov_index; 316 } else { 317 /* 318 * Already free, doing "compaction". 319 * 320 * Search for the old block of memory on the 321 * free list. First, check the most common 322 * case (last element free'd), then (this failing) 323 * the last ``realloc_srchlen'' items free'd. 324 * If all lookups fail, then assume the size of 325 * the memory block being realloc'd is the 326 * largest possible (so that all "nbytes" of new 327 * memory are copied into). Note that this could cause 328 * a memory fault if the old area was tiny, and the moon 329 * is gibbous. However, that is very unlikely. 330 */ 331 if ((i = findbucket(op, 1)) < 0 && 332 (i = findbucket(op, realloc_srchlen)) < 0) 333 i = NBUCKETS; 334 } 335 onb = 1 << (i + 3); 336 if (onb < pagesz) 337 onb -= sizeof (*op) + RSLOP; 338 else 339 onb += pagesz - sizeof (*op) - RSLOP; 340 /* avoid the copy if same size block */ 341 if (was_alloced) { 342 if (i) { 343 i = 1 << (i + 2); 344 if (i < pagesz) 345 i -= sizeof (*op) + RSLOP; 346 else 347 i += pagesz - sizeof (*op) - RSLOP; 348 } 349 if (nbytes <= onb && nbytes > i) { 350 #ifdef RCHECK 351 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 352 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 353 #endif 354 return(cp); 355 } else 356 free(cp); 357 } 358 if ((res = malloc(nbytes)) == NULL) 359 return (NULL); 360 if (cp != res) /* common optimization if "compacting" */ 361 bcopy(cp, res, (nbytes < onb) ? nbytes : onb); 362 return (res); 363 } 364 365 /* 366 * Search ``srchlen'' elements of each free list for a block whose 367 * header starts at ``freep''. If srchlen is -1 search the whole list. 368 * Return bucket number, or -1 if not found. 369 */ 370 static 371 findbucket(freep, srchlen) 372 union overhead *freep; 373 int srchlen; 374 { 375 register union overhead *p; 376 register int i, j; 377 378 for (i = 0; i < NBUCKETS; i++) { 379 j = 0; 380 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) { 381 if (p == freep) 382 return (i); 383 j++; 384 } 385 } 386 return (-1); 387 } 388 389 #ifdef MSTATS 390 /* 391 * mstats - print out statistics about malloc 392 * 393 * Prints two lines of numbers, one showing the length of the free list 394 * for each size category, the second showing the number of mallocs - 395 * frees for each size category. 396 */ 397 mstats(s) 398 char *s; 399 { 400 register int i, j; 401 register union overhead *p; 402 int totfree = 0, 403 totused = 0; 404 405 fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s); 406 for (i = 0; i < NBUCKETS; i++) { 407 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++) 408 ; 409 fprintf(stderr, " %d", j); 410 totfree += j * (1 << (i + 3)); 411 } 412 fprintf(stderr, "\nused:\t"); 413 for (i = 0; i < NBUCKETS; i++) { 414 fprintf(stderr, " %d", nmalloc[i]); 415 totused += nmalloc[i] * (1 << (i + 3)); 416 } 417 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n", 418 totused, totfree); 419 } 420 #endif 421