1 /* $NetBSD: malloc.c,v 1.6 1996/01/17 02:45:25 jtc 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 1.6 1996/01/17 02:45:25 jtc 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("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 long bucket, n; 142 register unsigned amt; 143 144 /* 145 * First time malloc is called, setup page size and 146 * align break pointer so all data will be page aligned. 147 */ 148 if (pagesz == 0) { 149 pagesz = n = getpagesize(); 150 op = (union overhead *)sbrk(0); 151 n = n - sizeof (*op) - ((long)op & (n - 1)); 152 if (n < 0) 153 n += pagesz; 154 if (n) { 155 if (sbrk(n) == (char *)-1) 156 return (NULL); 157 } 158 bucket = 0; 159 amt = 8; 160 while (pagesz > amt) { 161 amt <<= 1; 162 bucket++; 163 } 164 pagebucket = bucket; 165 } 166 /* 167 * Convert amount of memory requested into closest block size 168 * stored in hash buckets which satisfies request. 169 * Account for space used per block for accounting. 170 */ 171 if (nbytes <= (n = pagesz - sizeof (*op) - RSLOP)) { 172 #ifndef RCHECK 173 amt = 8; /* size of first bucket */ 174 bucket = 0; 175 #else 176 amt = 16; /* size of first bucket */ 177 bucket = 1; 178 #endif 179 n = -((long)sizeof (*op) + RSLOP); 180 } else { 181 amt = pagesz; 182 bucket = pagebucket; 183 } 184 while (nbytes > amt + n) { 185 amt <<= 1; 186 if (amt == 0) 187 return (NULL); 188 bucket++; 189 } 190 /* 191 * If nothing in hash bucket right now, 192 * request more memory from the system. 193 */ 194 if ((op = nextf[bucket]) == NULL) { 195 morecore(bucket); 196 if ((op = nextf[bucket]) == NULL) 197 return (NULL); 198 } 199 /* remove from linked list */ 200 nextf[bucket] = op->ov_next; 201 op->ov_magic = MAGIC; 202 op->ov_index = bucket; 203 #ifdef MSTATS 204 nmalloc[bucket]++; 205 #endif 206 #ifdef RCHECK 207 /* 208 * Record allocated size of block and 209 * bound space with magic numbers. 210 */ 211 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 212 op->ov_rmagic = RMAGIC; 213 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 214 #endif 215 return ((char *)(op + 1)); 216 } 217 218 /* 219 * Allocate more memory to the indicated bucket. 220 */ 221 static void 222 morecore(bucket) 223 int bucket; 224 { 225 register union overhead *op; 226 register long sz; /* size of desired block */ 227 long amt; /* amount to allocate */ 228 int nblks; /* how many blocks we get */ 229 230 /* 231 * sbrk_size <= 0 only for big, FLUFFY, requests (about 232 * 2^30 bytes on a VAX, I think) or for a negative arg. 233 */ 234 sz = 1 << (bucket + 3); 235 #ifdef DEBUG 236 ASSERT(sz > 0); 237 #else 238 if (sz <= 0) 239 return; 240 #endif 241 if (sz < pagesz) { 242 amt = pagesz; 243 nblks = amt / sz; 244 } else { 245 amt = sz + pagesz; 246 nblks = 1; 247 } 248 op = (union overhead *)sbrk(amt); 249 /* no more room! */ 250 if ((long)op == -1) 251 return; 252 /* 253 * Add new memory allocated to that on 254 * free list for this hash bucket. 255 */ 256 nextf[bucket] = op; 257 while (--nblks > 0) { 258 op->ov_next = (union overhead *)((caddr_t)op + sz); 259 op = (union overhead *)((caddr_t)op + sz); 260 } 261 } 262 263 void 264 free(cp) 265 void *cp; 266 { 267 register long size; 268 register union overhead *op; 269 270 if (cp == NULL) 271 return; 272 op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); 273 #ifdef DEBUG 274 ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */ 275 #else 276 if (op->ov_magic != MAGIC) 277 return; /* sanity */ 278 #endif 279 #ifdef RCHECK 280 ASSERT(op->ov_rmagic == RMAGIC); 281 ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC); 282 #endif 283 size = op->ov_index; 284 ASSERT(size < NBUCKETS); 285 op->ov_next = nextf[size]; /* also clobbers ov_magic */ 286 nextf[size] = op; 287 #ifdef MSTATS 288 nmalloc[size]--; 289 #endif 290 } 291 292 /* 293 * When a program attempts "storage compaction" as mentioned in the 294 * old malloc man page, it realloc's an already freed block. Usually 295 * this is the last block it freed; occasionally it might be farther 296 * back. We have to search all the free lists for the block in order 297 * to determine its bucket: 1st we make one pass thru the lists 298 * checking only the first block in each; if that fails we search 299 * ``realloc_srchlen'' blocks in each list for a match (the variable 300 * is extern so the caller can modify it). If that fails we just copy 301 * however many bytes was given to realloc() and hope it's not huge. 302 */ 303 int realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */ 304 305 void * 306 realloc(cp, nbytes) 307 void *cp; 308 size_t nbytes; 309 { 310 register u_long onb; 311 register long i; 312 union overhead *op; 313 char *res; 314 int was_alloced = 0; 315 316 if (cp == NULL) 317 return (malloc(nbytes)); 318 if (nbytes == 0) { 319 free (cp); 320 return NULL; 321 } 322 op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); 323 if (op->ov_magic == MAGIC) { 324 was_alloced++; 325 i = op->ov_index; 326 } else { 327 /* 328 * Already free, doing "compaction". 329 * 330 * Search for the old block of memory on the 331 * free list. First, check the most common 332 * case (last element free'd), then (this failing) 333 * the last ``realloc_srchlen'' items free'd. 334 * If all lookups fail, then assume the size of 335 * the memory block being realloc'd is the 336 * largest possible (so that all "nbytes" of new 337 * memory are copied into). Note that this could cause 338 * a memory fault if the old area was tiny, and the moon 339 * is gibbous. However, that is very unlikely. 340 */ 341 if ((i = findbucket(op, 1)) < 0 && 342 (i = findbucket(op, realloc_srchlen)) < 0) 343 i = NBUCKETS; 344 } 345 onb = 1 << (i + 3); 346 if (onb < pagesz) 347 onb -= sizeof (*op) + RSLOP; 348 else 349 onb += pagesz - sizeof (*op) - RSLOP; 350 /* avoid the copy if same size block */ 351 if (was_alloced) { 352 if (i) { 353 i = 1 << (i + 2); 354 if (i < pagesz) 355 i -= sizeof (*op) + RSLOP; 356 else 357 i += pagesz - sizeof (*op) - RSLOP; 358 } 359 if (nbytes <= onb && nbytes > i) { 360 #ifdef RCHECK 361 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1); 362 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC; 363 #endif 364 return(cp); 365 } else 366 free(cp); 367 } 368 if ((res = malloc(nbytes)) == NULL) 369 return (NULL); 370 if (cp != res) /* common optimization if "compacting" */ 371 bcopy(cp, res, (nbytes < onb) ? nbytes : onb); 372 return (res); 373 } 374 375 /* 376 * Search ``srchlen'' elements of each free list for a block whose 377 * header starts at ``freep''. If srchlen is -1 search the whole list. 378 * Return bucket number, or -1 if not found. 379 */ 380 static 381 findbucket(freep, srchlen) 382 union overhead *freep; 383 int srchlen; 384 { 385 register union overhead *p; 386 register int i, j; 387 388 for (i = 0; i < NBUCKETS; i++) { 389 j = 0; 390 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) { 391 if (p == freep) 392 return (i); 393 j++; 394 } 395 } 396 return (-1); 397 } 398 399 #ifdef MSTATS 400 /* 401 * mstats - print out statistics about malloc 402 * 403 * Prints two lines of numbers, one showing the length of the free list 404 * for each size category, the second showing the number of mallocs - 405 * frees for each size category. 406 */ 407 mstats(s) 408 char *s; 409 { 410 register int i, j; 411 register union overhead *p; 412 int totfree = 0, 413 totused = 0; 414 415 fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s); 416 for (i = 0; i < NBUCKETS; i++) { 417 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++) 418 ; 419 fprintf(stderr, " %d", j); 420 totfree += j * (1 << (i + 3)); 421 } 422 fprintf(stderr, "\nused:\t"); 423 for (i = 0; i < NBUCKETS; i++) { 424 fprintf(stderr, " %d", nmalloc[i]); 425 totused += nmalloc[i] * (1 << (i + 3)); 426 } 427 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n", 428 totused, totfree); 429 } 430 #endif 431