1 /* $NetBSD: malloc.c,v 1.8 1997/04/07 03:12:14 christos Exp $ */ 2 3 /* 4 * Copyright (c) 1983 Regents of the University of California. 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. All advertising materials mentioning features or use of this software 16 * must display the following acknowledgement: 17 * This product includes software developed by the University of 18 * California, Berkeley and its contributors. 19 * 4. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 */ 35 36 #if defined(LIBC_SCCS) && !defined(lint) 37 #if 0 38 static char *sccsid = "from: @(#)malloc.c 5.11 (Berkeley) 2/23/91"; 39 #else 40 static char *rcsid = "$NetBSD: malloc.c,v 1.8 1997/04/07 03:12:14 christos Exp $"; 41 #endif 42 #endif /* LIBC_SCCS and not lint */ 43 44 /* 45 * malloc.c (Caltech) 2/21/82 46 * Chris Kingsley, kingsley@cit-20. 47 * 48 * This is a very fast storage allocator. It allocates blocks of a small 49 * number of different sizes, and keeps free lists of each size. Blocks that 50 * don't exactly fit are passed up to the next larger size. In this 51 * implementation, the available sizes are 2^n-4 (or 2^n-10) bytes long. 52 * This is designed for use in a virtual memory environment. 53 */ 54 55 #include <sys/types.h> 56 #include <stdlib.h> 57 #include <string.h> 58 #include <unistd.h> 59 60 #define NULL 0 61 62 static void morecore(); 63 static int findbucket(); 64 65 /* 66 * The overhead on a block is at least 4 bytes. When free, this space 67 * contains a pointer to the next free block, and the bottom two bits must 68 * be zero. When in use, the first byte is set to MAGIC, and the second 69 * byte is the size index. The remaining bytes are for alignment. 70 * If range checking is enabled then a second word holds the size of the 71 * requested block, less 1, rounded up to a multiple of sizeof(RMAGIC). 72 * The order of elements is critical: ov_magic must overlay the low order 73 * bits of ov_next, and ov_magic can not be a valid ov_next bit pattern. 74 */ 75 union overhead { 76 union overhead *ov_next; /* when free */ 77 struct { 78 u_char ovu_magic; /* magic number */ 79 u_char ovu_index; /* bucket # */ 80 #ifdef RCHECK 81 u_short ovu_rmagic; /* range magic number */ 82 u_long ovu_size; /* actual block size */ 83 #endif 84 } ovu; 85 #define ov_magic ovu.ovu_magic 86 #define ov_index ovu.ovu_index 87 #define ov_rmagic ovu.ovu_rmagic 88 #define ov_size ovu.ovu_size 89 }; 90 91 #define MAGIC 0xef /* magic # on accounting info */ 92 #define RMAGIC 0x5555 /* magic # on range info */ 93 94 #ifdef RCHECK 95 #define RSLOP sizeof (u_short) 96 #else 97 #define RSLOP 0 98 #endif 99 100 /* 101 * nextf[i] is the pointer to the next free block of size 2^(i+3). The 102 * smallest allocatable block is 8 bytes. The overhead information 103 * precedes the data area returned to the user. 104 */ 105 #define NBUCKETS 30 106 static union overhead *nextf[NBUCKETS]; 107 extern char *sbrk(); 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(DEBUG) || defined(RCHECK) 122 #define ASSERT(p) if (!(p)) botch(__STRING(p)) 123 #include <stdio.h> 124 static 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 void * 137 malloc(nbytes) 138 size_t nbytes; 139 { 140 register union overhead *op; 141 register int bucket; 142 register long n; 143 register unsigned amt; 144 145 /* 146 * First time malloc is called, setup page size and 147 * align break pointer so all data will be page aligned. 148 */ 149 if (pagesz == 0) { 150 pagesz = n = getpagesize(); 151 op = (union overhead *)sbrk(0); 152 n = n - sizeof (*op) - ((long)op & (n - 1)); 153 if (n < 0) 154 n += pagesz; 155 if (n) { 156 if (sbrk(n) == (char *)-1) 157 return (NULL); 158 } 159 bucket = 0; 160 amt = 8; 161 while (pagesz > amt) { 162 amt <<= 1; 163 bucket++; 164 } 165 pagebucket = bucket; 166 } 167 /* 168 * Convert amount of memory requested into closest block size 169 * stored in hash buckets which satisfies request. 170 * Account for space used per block for accounting. 171 */ 172 if (nbytes <= (n = pagesz - sizeof (*op) - RSLOP)) { 173 #ifndef RCHECK 174 amt = 8; /* size of first bucket */ 175 bucket = 0; 176 #else 177 amt = 16; /* size of first bucket */ 178 bucket = 1; 179 #endif 180 n = -((long)sizeof (*op) + RSLOP); 181 } else { 182 amt = pagesz; 183 bucket = pagebucket; 184 } 185 while (nbytes > amt + n) { 186 amt <<= 1; 187 if (amt == 0) 188 return (NULL); 189 bucket++; 190 } 191 /* 192 * If nothing in hash bucket right now, 193 * request more memory from the system. 194 */ 195 if ((op = nextf[bucket]) == NULL) { 196 morecore(bucket); 197 if ((op = nextf[bucket]) == NULL) 198 return (NULL); 199 } 200 /* remove from linked list */ 201 nextf[bucket] = op->ov_next; 202 op->ov_magic = MAGIC; 203 op->ov_index = bucket; 204 #ifdef MSTATS 205 nmalloc[bucket]++; 206 #endif 207 #ifdef RCHECK 208 /* 209 * Record allocated size of block and 210 * bound space with magic numbers. 211 */ 212 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 213 op->ov_rmagic = RMAGIC; 214 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 215 #endif 216 return ((char *)(op + 1)); 217 } 218 219 /* 220 * Allocate more memory to the indicated bucket. 221 */ 222 static void 223 morecore(bucket) 224 int bucket; 225 { 226 register union overhead *op; 227 register long sz; /* size of desired block */ 228 long amt; /* amount to allocate */ 229 int nblks; /* how many blocks we get */ 230 231 /* 232 * sbrk_size <= 0 only for big, FLUFFY, requests (about 233 * 2^30 bytes on a VAX, I think) or for a negative arg. 234 */ 235 sz = 1 << (bucket + 3); 236 #ifdef DEBUG 237 ASSERT(sz > 0); 238 #else 239 if (sz <= 0) 240 return; 241 #endif 242 if (sz < pagesz) { 243 amt = pagesz; 244 nblks = amt / sz; 245 } else { 246 amt = sz + pagesz; 247 nblks = 1; 248 } 249 op = (union overhead *)sbrk(amt); 250 /* no more room! */ 251 if ((long)op == -1) 252 return; 253 /* 254 * Add new memory allocated to that on 255 * free list for this hash bucket. 256 */ 257 nextf[bucket] = op; 258 while (--nblks > 0) { 259 op->ov_next = (union overhead *)((caddr_t)op + sz); 260 op = (union overhead *)((caddr_t)op + sz); 261 } 262 } 263 264 void 265 free(cp) 266 void *cp; 267 { 268 register long size; 269 register union overhead *op; 270 271 if (cp == NULL) 272 return; 273 op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); 274 #ifdef DEBUG 275 ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */ 276 #else 277 if (op->ov_magic != MAGIC) 278 return; /* sanity */ 279 #endif 280 #ifdef RCHECK 281 ASSERT(op->ov_rmagic == RMAGIC); 282 ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC); 283 #endif 284 size = op->ov_index; 285 ASSERT(size < NBUCKETS); 286 op->ov_next = nextf[size]; /* also clobbers ov_magic */ 287 nextf[size] = op; 288 #ifdef MSTATS 289 nmalloc[size]--; 290 #endif 291 } 292 293 /* 294 * When a program attempts "storage compaction" as mentioned in the 295 * old malloc man page, it realloc's an already freed block. Usually 296 * this is the last block it freed; occasionally it might be farther 297 * back. We have to search all the free lists for the block in order 298 * to determine its bucket: 1st we make one pass thru the lists 299 * checking only the first block in each; if that fails we search 300 * ``realloc_srchlen'' blocks in each list for a match (the variable 301 * is extern so the caller can modify it). If that fails we just copy 302 * however many bytes was given to realloc() and hope it's not huge. 303 */ 304 int realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */ 305 306 void * 307 realloc(cp, nbytes) 308 void *cp; 309 size_t nbytes; 310 { 311 register u_long onb; 312 register long i; 313 union overhead *op; 314 char *res; 315 int was_alloced = 0; 316 317 if (cp == NULL) 318 return (malloc(nbytes)); 319 if (nbytes == 0) { 320 free (cp); 321 return NULL; 322 } 323 op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); 324 if (op->ov_magic == MAGIC) { 325 was_alloced++; 326 i = op->ov_index; 327 } else { 328 /* 329 * Already free, doing "compaction". 330 * 331 * Search for the old block of memory on the 332 * free list. First, check the most common 333 * case (last element free'd), then (this failing) 334 * the last ``realloc_srchlen'' items free'd. 335 * If all lookups fail, then assume the size of 336 * the memory block being realloc'd is the 337 * largest possible (so that all "nbytes" of new 338 * memory are copied into). Note that this could cause 339 * a memory fault if the old area was tiny, and the moon 340 * is gibbous. However, that is very unlikely. 341 */ 342 if ((i = findbucket(op, 1)) < 0 && 343 (i = findbucket(op, realloc_srchlen)) < 0) 344 i = NBUCKETS; 345 } 346 onb = 1 << (i + 3); 347 if (onb < pagesz) 348 onb -= sizeof (*op) + RSLOP; 349 else 350 onb += pagesz - sizeof (*op) - RSLOP; 351 /* avoid the copy if same size block */ 352 if (was_alloced) { 353 if (i) { 354 i = 1 << (i + 2); 355 if (i < pagesz) 356 i -= sizeof (*op) + RSLOP; 357 else 358 i += pagesz - sizeof (*op) - RSLOP; 359 } 360 if (nbytes <= onb && nbytes > i) { 361 #ifdef RCHECK 362 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 363 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 364 #endif 365 return(cp); 366 } else 367 free(cp); 368 } 369 if ((res = malloc(nbytes)) == NULL) 370 return (NULL); 371 if (cp != res) /* common optimization if "compacting" */ 372 bcopy(cp, res, (nbytes < onb) ? nbytes : onb); 373 return (res); 374 } 375 376 /* 377 * Search ``srchlen'' elements of each free list for a block whose 378 * header starts at ``freep''. If srchlen is -1 search the whole list. 379 * Return bucket number, or -1 if not found. 380 */ 381 static 382 findbucket(freep, srchlen) 383 union overhead *freep; 384 int srchlen; 385 { 386 register union overhead *p; 387 register int i, j; 388 389 for (i = 0; i < NBUCKETS; i++) { 390 j = 0; 391 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) { 392 if (p == freep) 393 return (i); 394 j++; 395 } 396 } 397 return (-1); 398 } 399 400 #ifdef MSTATS 401 /* 402 * mstats - print out statistics about malloc 403 * 404 * Prints two lines of numbers, one showing the length of the free list 405 * for each size category, the second showing the number of mallocs - 406 * frees for each size category. 407 */ 408 mstats(s) 409 char *s; 410 { 411 register int i, j; 412 register union overhead *p; 413 int totfree = 0, 414 totused = 0; 415 416 fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s); 417 for (i = 0; i < NBUCKETS; i++) { 418 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++) 419 ; 420 fprintf(stderr, " %d", j); 421 totfree += j * (1 << (i + 3)); 422 } 423 fprintf(stderr, "\nused:\t"); 424 for (i = 0; i < NBUCKETS; i++) { 425 fprintf(stderr, " %d", nmalloc[i]); 426 totused += nmalloc[i] * (1 << (i + 3)); 427 } 428 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n", 429 totused, totfree); 430 } 431 #endif 432