1 /* $NetBSD: malloc.c,v 1.9 1997/07/13 20:16:47 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 #include <sys/cdefs.h> 37 #if defined(LIBC_SCCS) && !defined(lint) 38 #if 0 39 static char *sccsid = "from: @(#)malloc.c 5.11 (Berkeley) 2/23/91"; 40 #else 41 __RCSID("$NetBSD: malloc.c,v 1.9 1997/07/13 20:16:47 christos Exp $"); 42 #endif 43 #endif /* LIBC_SCCS and not lint */ 44 45 /* 46 * malloc.c (Caltech) 2/21/82 47 * Chris Kingsley, kingsley@cit-20. 48 * 49 * This is a very fast storage allocator. It allocates blocks of a small 50 * number of different sizes, and keeps free lists of each size. Blocks that 51 * don't exactly fit are passed up to the next larger size. In this 52 * implementation, the available sizes are 2^n-4 (or 2^n-10) bytes long. 53 * This is designed for use in a virtual memory environment. 54 */ 55 56 #if defined(DEBUG) || defined(RCHECK) || defined(MSTATS) 57 #include <stdio.h> 58 #endif 59 #include <sys/types.h> 60 #include <stdlib.h> 61 #include <string.h> 62 #include <unistd.h> 63 64 #define NULL 0 65 66 67 /* 68 * The overhead on a block is at least 4 bytes. When free, this space 69 * contains a pointer to the next free block, and the bottom two bits must 70 * be zero. When in use, the first byte is set to MAGIC, and the second 71 * byte is the size index. The remaining bytes are for alignment. 72 * If range checking is enabled then a second word holds the size of the 73 * requested block, less 1, rounded up to a multiple of sizeof(RMAGIC). 74 * The order of elements is critical: ov_magic must overlay the low order 75 * bits of ov_next, and ov_magic can not be a valid ov_next bit pattern. 76 */ 77 union overhead { 78 union overhead *ov_next; /* when free */ 79 struct { 80 u_char ovu_magic; /* magic number */ 81 u_char ovu_index; /* bucket # */ 82 #ifdef RCHECK 83 u_short ovu_rmagic; /* range magic number */ 84 u_long ovu_size; /* actual block size */ 85 #endif 86 } ovu; 87 #define ov_magic ovu.ovu_magic 88 #define ov_index ovu.ovu_index 89 #define ov_rmagic ovu.ovu_rmagic 90 #define ov_size ovu.ovu_size 91 }; 92 93 #define MAGIC 0xef /* magic # on accounting info */ 94 #define RMAGIC 0x5555 /* magic # on range info */ 95 96 #ifdef RCHECK 97 #define RSLOP sizeof (u_short) 98 #else 99 #define RSLOP 0 100 #endif 101 102 /* 103 * nextf[i] is the pointer to the next free block of size 2^(i+3). The 104 * smallest allocatable block is 8 bytes. The overhead information 105 * precedes the data area returned to the user. 106 */ 107 #define NBUCKETS 30 108 static union overhead *nextf[NBUCKETS]; 109 110 static int pagesz; /* page size */ 111 static int pagebucket; /* page size bucket */ 112 113 #ifdef MSTATS 114 /* 115 * nmalloc[i] is the difference between the number of mallocs and frees 116 * for a given block size. 117 */ 118 static u_int nmalloc[NBUCKETS]; 119 #include <stdio.h> 120 #endif 121 122 static void morecore __P((int)); 123 static int findbucket __P((union overhead *, int)); 124 #ifdef MSTATS 125 void mstats __P((char *)); 126 #endif 127 128 #if defined(DEBUG) || defined(RCHECK) 129 #define ASSERT(p) if (!(p)) botch(__STRING(p)) 130 131 static botch __P((char *)); 132 133 static 134 botch(s) 135 char *s; 136 { 137 fprintf(stderr, "\r\nassertion botched: %s\r\n", s); 138 (void) fflush(stderr); /* just in case user buffered it */ 139 abort(); 140 } 141 #else 142 #define ASSERT(p) 143 #endif 144 145 void * 146 malloc(nbytes) 147 size_t nbytes; 148 { 149 register union overhead *op; 150 register int bucket; 151 register long n; 152 register unsigned amt; 153 154 /* 155 * First time malloc is called, setup page size and 156 * align break pointer so all data will be page aligned. 157 */ 158 if (pagesz == 0) { 159 pagesz = n = getpagesize(); 160 op = (union overhead *)sbrk(0); 161 n = n - sizeof (*op) - ((long)op & (n - 1)); 162 if (n < 0) 163 n += pagesz; 164 if (n) { 165 if (sbrk(n) == (char *)-1) 166 return (NULL); 167 } 168 bucket = 0; 169 amt = 8; 170 while (pagesz > amt) { 171 amt <<= 1; 172 bucket++; 173 } 174 pagebucket = bucket; 175 } 176 /* 177 * Convert amount of memory requested into closest block size 178 * stored in hash buckets which satisfies request. 179 * Account for space used per block for accounting. 180 */ 181 if (nbytes <= (n = pagesz - sizeof (*op) - RSLOP)) { 182 #ifndef RCHECK 183 amt = 8; /* size of first bucket */ 184 bucket = 0; 185 #else 186 amt = 16; /* size of first bucket */ 187 bucket = 1; 188 #endif 189 n = -((long)sizeof (*op) + RSLOP); 190 } else { 191 amt = pagesz; 192 bucket = pagebucket; 193 } 194 while (nbytes > amt + n) { 195 amt <<= 1; 196 if (amt == 0) 197 return (NULL); 198 bucket++; 199 } 200 /* 201 * If nothing in hash bucket right now, 202 * request more memory from the system. 203 */ 204 if ((op = nextf[bucket]) == NULL) { 205 morecore(bucket); 206 if ((op = nextf[bucket]) == NULL) 207 return (NULL); 208 } 209 /* remove from linked list */ 210 nextf[bucket] = op->ov_next; 211 op->ov_magic = MAGIC; 212 op->ov_index = bucket; 213 #ifdef MSTATS 214 nmalloc[bucket]++; 215 #endif 216 #ifdef RCHECK 217 /* 218 * Record allocated size of block and 219 * bound space with magic numbers. 220 */ 221 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 222 op->ov_rmagic = RMAGIC; 223 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 224 #endif 225 return ((char *)(op + 1)); 226 } 227 228 /* 229 * Allocate more memory to the indicated bucket. 230 */ 231 static void 232 morecore(bucket) 233 int bucket; 234 { 235 register union overhead *op; 236 register long sz; /* size of desired block */ 237 long amt; /* amount to allocate */ 238 int nblks; /* how many blocks we get */ 239 240 /* 241 * sbrk_size <= 0 only for big, FLUFFY, requests (about 242 * 2^30 bytes on a VAX, I think) or for a negative arg. 243 */ 244 sz = 1 << (bucket + 3); 245 #ifdef DEBUG 246 ASSERT(sz > 0); 247 #else 248 if (sz <= 0) 249 return; 250 #endif 251 if (sz < pagesz) { 252 amt = pagesz; 253 nblks = amt / sz; 254 } else { 255 amt = sz + pagesz; 256 nblks = 1; 257 } 258 op = (union overhead *)sbrk(amt); 259 /* no more room! */ 260 if ((long)op == -1) 261 return; 262 /* 263 * Add new memory allocated to that on 264 * free list for this hash bucket. 265 */ 266 nextf[bucket] = op; 267 while (--nblks > 0) { 268 op->ov_next = (union overhead *)((caddr_t)op + sz); 269 op = (union overhead *)((caddr_t)op + sz); 270 } 271 } 272 273 void 274 free(cp) 275 void *cp; 276 { 277 register long size; 278 register union overhead *op; 279 280 if (cp == NULL) 281 return; 282 op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); 283 #ifdef DEBUG 284 ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */ 285 #else 286 if (op->ov_magic != MAGIC) 287 return; /* sanity */ 288 #endif 289 #ifdef RCHECK 290 ASSERT(op->ov_rmagic == RMAGIC); 291 ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC); 292 #endif 293 size = op->ov_index; 294 ASSERT(size < NBUCKETS); 295 op->ov_next = nextf[size]; /* also clobbers ov_magic */ 296 nextf[size] = op; 297 #ifdef MSTATS 298 nmalloc[size]--; 299 #endif 300 } 301 302 /* 303 * When a program attempts "storage compaction" as mentioned in the 304 * old malloc man page, it realloc's an already freed block. Usually 305 * this is the last block it freed; occasionally it might be farther 306 * back. We have to search all the free lists for the block in order 307 * to determine its bucket: 1st we make one pass thru the lists 308 * checking only the first block in each; if that fails we search 309 * ``realloc_srchlen'' blocks in each list for a match (the variable 310 * is extern so the caller can modify it). If that fails we just copy 311 * however many bytes was given to realloc() and hope it's not huge. 312 */ 313 int realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */ 314 315 void * 316 realloc(cp, nbytes) 317 void *cp; 318 size_t nbytes; 319 { 320 register u_long onb; 321 register long i; 322 union overhead *op; 323 char *res; 324 int was_alloced = 0; 325 326 if (cp == NULL) 327 return (malloc(nbytes)); 328 if (nbytes == 0) { 329 free (cp); 330 return NULL; 331 } 332 op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); 333 if (op->ov_magic == MAGIC) { 334 was_alloced++; 335 i = op->ov_index; 336 } else { 337 /* 338 * Already free, doing "compaction". 339 * 340 * Search for the old block of memory on the 341 * free list. First, check the most common 342 * case (last element free'd), then (this failing) 343 * the last ``realloc_srchlen'' items free'd. 344 * If all lookups fail, then assume the size of 345 * the memory block being realloc'd is the 346 * largest possible (so that all "nbytes" of new 347 * memory are copied into). Note that this could cause 348 * a memory fault if the old area was tiny, and the moon 349 * is gibbous. However, that is very unlikely. 350 */ 351 if ((i = findbucket(op, 1)) < 0 && 352 (i = findbucket(op, realloc_srchlen)) < 0) 353 i = NBUCKETS; 354 } 355 onb = 1 << (i + 3); 356 if (onb < pagesz) 357 onb -= sizeof (*op) + RSLOP; 358 else 359 onb += pagesz - sizeof (*op) - RSLOP; 360 /* avoid the copy if same size block */ 361 if (was_alloced) { 362 if (i) { 363 i = 1 << (i + 2); 364 if (i < pagesz) 365 i -= sizeof (*op) + RSLOP; 366 else 367 i += pagesz - sizeof (*op) - RSLOP; 368 } 369 if (nbytes <= onb && nbytes > i) { 370 #ifdef RCHECK 371 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 372 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 373 #endif 374 return(cp); 375 } else 376 free(cp); 377 } 378 if ((res = malloc(nbytes)) == NULL) 379 return (NULL); 380 if (cp != res) /* common optimization if "compacting" */ 381 bcopy(cp, res, (nbytes < onb) ? nbytes : onb); 382 return (res); 383 } 384 385 /* 386 * Search ``srchlen'' elements of each free list for a block whose 387 * header starts at ``freep''. If srchlen is -1 search the whole list. 388 * Return bucket number, or -1 if not found. 389 */ 390 static int 391 findbucket(freep, srchlen) 392 union overhead *freep; 393 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(s) 419 char *s; 420 { 421 register int i, j; 422 register union overhead *p; 423 int totfree = 0, 424 totused = 0; 425 426 fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s); 427 for (i = 0; i < NBUCKETS; i++) { 428 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++) 429 ; 430 fprintf(stderr, " %d", j); 431 totfree += j * (1 << (i + 3)); 432 } 433 fprintf(stderr, "\nused:\t"); 434 for (i = 0; i < NBUCKETS; i++) { 435 fprintf(stderr, " %d", nmalloc[i]); 436 totused += nmalloc[i] * (1 << (i + 3)); 437 } 438 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n", 439 totused, totfree); 440 } 441 #endif 442