libexec/ld.aout_so/malloc.c

   1 /*      $NetBSD: malloc.c,v 1.7 2000/11/28 06:01:34 mycroft 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. Neither the name of the University nor the names of its contributors
  16  *    may be used to endorse or promote products derived from this software
  17  *    without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  */
  31
  32 #include <sys/cdefs.h>
  33 #if defined(LIBC_SCCS) && !defined(lint)
  34 #if 0
  35 static char *sccsid = "from: @(#)malloc.c       5.11 (Berkeley) 2/23/91";
  36 #else
  37 __RCSID("$NetBSD: malloc.c,v 1.7 2000/11/28 06:01:34 mycroft Exp $");
  38 #endif
  39 #endif /* LIBC_SCCS and not lint */
  40
  41 /*
  42  * malloc.c (Caltech) 2/21/82
  43  * Chris Kingsley, kingsley@cit-20.
  44  *
  45  * This is a very fast storage allocator.  It allocates blocks of a small
  46  * number of different sizes, and keeps free lists of each size.  Blocks that
  47  * don't exactly fit are passed up to the next larger size.  In this
  48  * implementation, the available sizes are 2^n-4 (or 2^n-10) bytes long.
  49  * This is designed for use in a virtual memory environment.
  50  */
  51
  52 #include <sys/types.h>
  53 #include <err.h>
  54 #include <stdlib.h>
  55 #include <string.h>
  56 #include <unistd.h>
  57 #include <sys/param.h>
  58 #include <sys/mman.h>
  59 #ifndef BSD
  60 #define MAP_FILE        0
  61 #define MAP_ANON        0
  62 #endif
  63
  64 #ifndef BSD             /* Need do better than this */
  65 #define NEED_DEV_ZERO   1
  66 #endif
  67
  68 #define NULL 0
  69
  70 /*
  71  * The overhead on a block is at least 4 bytes.  When free, this space
  72  * contains a pointer to the next free block, and the bottom two bits must
  73  * be zero.  When in use, the first byte is set to MAGIC, and the second
  74  * byte is the size index.  The remaining bytes are for alignment.
  75  * If range checking is enabled then a second word holds the size of the
  76  * requested block, less 1, rounded up to a multiple of sizeof(RMAGIC).
  77  * The order of elements is critical: ov_magic must overlay the low order
  78  * bits of ov_next, and ov_magic can not be a valid ov_next bit pattern.
  79  */
  80 union   overhead {
  81         union   overhead *ov_next;      /* when free */
  82         struct {
  83                 u_char  ovu_magic;      /* magic number */
  84                 u_char  ovu_index;      /* bucket # */
  85 #ifdef RCHECK
  86                 u_short ovu_rmagic;     /* range magic number */
  87                 u_int   ovu_size;       /* actual block size */
  88 #endif
  89         } ovu;
  90 #define ov_magic        ovu.ovu_magic
  91 #define ov_index        ovu.ovu_index
  92 #define ov_rmagic       ovu.ovu_rmagic
  93 #define ov_size         ovu.ovu_size
  94 };
  95
  96 #define MAGIC           0xef            /* magic # on accounting info */
  97 #define RMAGIC          0x5555          /* magic # on range info */
  98
  99 #ifdef RCHECK
 100 #define RSLOP           sizeof (u_short)
 101 #else
 102 #define RSLOP           0
 103 #endif
 104
 105 /*
 106  * Pre-allocate mmap'ed pages
 107  */
 108 #define NPOOLPAGES      (32*1024/pagesz)
 109 static caddr_t          pagepool_start, pagepool_end;
 110 static int              morepages __P((int));
 111 static void             morecore __P((int));
 112 static int              findbucket __P((union overhead *, int));
 113
 114 /*
 115  * nextf[i] is the pointer to the next free block of size 2^(i+3).  The
 116  * smallest allocatable block is 8 bytes.  The overhead information
 117  * precedes the data area returned to the user.
 118  */
 119 #define NBUCKETS 30
 120 static  union overhead *nextf[NBUCKETS];
 121
 122 static  int pagesz;                     /* page size */
 123 static  int pagebucket;                 /* page size bucket */
 124
 125 #ifdef MSTATS
 126 /*
 127  * nmalloc[i] is the difference between the number of mallocs and frees
 128  * for a given block size.
 129  */
 130 static  u_int nmalloc[NBUCKETS];
 131 #include <stdio.h>
 132 #endif
 133
 134 #if defined(DEBUG) || defined(RCHECK)
 135 #define ASSERT(p)   if (!(p)) botch("p")
 136 #include <stdio.h>
 137 static void botch __P((char *));
 138 static void
 139 botch(s)
 140         char *s;
 141 {
 142         fprintf(stderr, "\r\nassertion botched: %s\r\n", s);
 143         (void) fflush(stderr);          /* just in case user buffered it */
 144         abort();
 145 }
 146 #else
 147 #define ASSERT(p)
 148 #endif
 149
 150 void *
 151 malloc(nbytes)
 152         size_t nbytes;
 153 {
 154         register union overhead *op;
 155         register int bucket, n;
 156         register unsigned amt;
 157
 158         /*
 159          * First time malloc is called, setup page size and
 160          * align break pointer so all data will be page aligned.
 161          */
 162         if (pagesz == 0) {
 163                 pagesz = n = getpagesize();
 164                 if (morepages(NPOOLPAGES) == 0)
 165                         return NULL;
 166                 op = (union overhead *)(pagepool_start);
 167                 n = n - sizeof (*op) - ((int)op & (n - 1));
 168                 if (n < 0)
 169                         n += pagesz;
 170                 if (n) {
 171                         pagepool_start += n;
 172                 }
 173                 bucket = 0;
 174                 amt = 8;
 175                 while (pagesz > amt) {
 176                         amt <<= 1;
 177                         bucket++;
 178                 }
 179                 pagebucket = bucket;
 180         }
 181         /*
 182          * Convert amount of memory requested into closest block size
 183          * stored in hash buckets which satisfies request.
 184          * Account for space used per block for accounting.
 185          */
 186         if (nbytes <= (n = pagesz - sizeof (*op) - RSLOP)) {
 187 #ifndef RCHECK
 188                 amt = 8;        /* size of first bucket */
 189                 bucket = 0;
 190 #else
 191                 amt = 16;       /* size of first bucket */
 192                 bucket = 1;
 193 #endif
 194                 n = -(sizeof (*op) + RSLOP);
 195         } else {
 196                 amt = pagesz;
 197                 bucket = pagebucket;
 198         }
 199         while (nbytes > amt + n) {
 200                 amt <<= 1;
 201                 if (amt == 0)
 202                         return (NULL);
 203                 bucket++;
 204         }
 205         /*
 206          * If nothing in hash bucket right now,
 207          * request more memory from the system.
 208          */
 209         if ((op = nextf[bucket]) == NULL) {
 210                 morecore(bucket);
 211                 if ((op = nextf[bucket]) == NULL)
 212                         return (NULL);
 213         }
 214         /* remove from linked list */
 215         nextf[bucket] = op->ov_next;
 216         op->ov_magic = MAGIC;
 217         op->ov_index = bucket;
 218 #ifdef MSTATS
 219         nmalloc[bucket]++;
 220 #endif
 221 #ifdef RCHECK
 222         /*
 223          * Record allocated size of block and
 224          * bound space with magic numbers.
 225          */
 226         op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
 227         op->ov_rmagic = RMAGIC;
 228         *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
 229 #endif
 230         return ((char *)(op + 1));
 231 }
 232
 233 /*
 234  * Allocate more memory to the indicated bucket.
 235  */
 236 static void
 237 morecore(bucket)
 238         int bucket;
 239 {
 240         register union overhead *op;
 241         register int sz;                /* size of desired block */
 242         int amt;                        /* amount to allocate */
 243         int nblks;                      /* how many blocks we get */
 244
 245         /* Map bucket number to size */
 246         sz = 1 << (bucket + 3);
 247 #ifdef DEBUG
 248         ASSERT(sz > 0);
 249 #else
 250         if (sz <= 0)
 251                 return;
 252 #endif
 253         if (sz < pagesz) {
 254                 amt = pagesz;
 255                 nblks = amt / sz;
 256         } else {
 257                 amt = sz + pagesz;
 258                 nblks = 1;
 259         }
 260         if (amt > pagepool_end - pagepool_start)
 261                 if (morepages(amt/pagesz + NPOOLPAGES) == 0)
 262                         return;
 263         op = (union overhead *)pagepool_start;
 264         pagepool_start += amt;
 265
 266         /*
 267          * Add new memory allocated to that on
 268          * free list for this hash bucket.
 269          */
 270         nextf[bucket] = op;
 271         while (--nblks > 0) {
 272                 op->ov_next = (union overhead *)((caddr_t)op + sz);
 273                 op = (union overhead *)((caddr_t)op + sz);
 274         }
 275 }
 276
 277 void
 278 free(cp)
 279         void *cp;
 280 {
 281         register int size;
 282         register union overhead *op;
 283
 284         if (cp == NULL)
 285                 return;
 286         op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
 287 #ifdef DEBUG
 288         ASSERT(op->ov_magic == MAGIC);          /* make sure it was in use */
 289 #else
 290         if (op->ov_magic != MAGIC)
 291                 return;                         /* sanity */
 292 #endif
 293 #ifdef RCHECK
 294         ASSERT(op->ov_rmagic == RMAGIC);
 295         ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC);
 296 #endif
 297         size = op->ov_index;
 298         ASSERT(size < NBUCKETS);
 299         op->ov_next = nextf[size];      /* also clobbers ov_magic */
 300         nextf[size] = op;
 301 #ifdef MSTATS
 302         nmalloc[size]--;
 303 #endif
 304 }
 305
 306 /*
 307  * When a program attempts "storage compaction" as mentioned in the
 308  * old malloc man page, it realloc's an already freed block.  Usually
 309  * this is the last block it freed; occasionally it might be farther
 310  * back.  We have to search all the free lists for the block in order
 311  * to determine its bucket: 1st we make one pass thru the lists
 312  * checking only the first block in each; if that fails we search
 313  * ``realloc_srchlen'' blocks in each list for a match (the variable
 314  * is extern so the caller can modify it).  If that fails we just copy
 315  * however many bytes was given to realloc() and hope it's not huge.
 316  */
 317 int realloc_srchlen = 4;        /* 4 should be plenty, -1 =>'s whole list */
 318
 319 void *
 320 realloc(cp, nbytes)
 321         void *cp;
 322         size_t nbytes;
 323 {
 324         register u_int onb;
 325         register int i;
 326         union overhead *op;
 327         char *res;
 328         int was_alloced = 0;
 329
 330         if (cp == NULL)
 331                 return (malloc(nbytes));
 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 mstats(s)
 418         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(n)
 445 int     n;
 446 {
 447         int     fd = -1;
 448         int     offset;
 449
 450 #ifdef NEED_DEV_ZERO
 451         fd = open("/dev/zero", O_RDWR, 0);
 452         if (fd == -1)
 453                 perror("/dev/zero");
 454 #endif
 455
 456         if (pagepool_end - pagepool_start > pagesz) {
 457                 caddr_t addr = (caddr_t)
 458                         (((int)pagepool_start + pagesz - 1) & ~(pagesz - 1));
 459                 if (munmap(addr, pagepool_end - addr) != 0)
 460                         warn("morepages: munmap %p", addr);
 461         }
 462
 463         offset = (int)pagepool_start - ((int)pagepool_start & ~(pagesz - 1));
 464
 465         if ((pagepool_start = mmap(0, n * pagesz,
 466                         PROT_READ|PROT_WRITE,
 467                         MAP_ANON|MAP_PRIVATE, fd, 0)) == (caddr_t)-1) {
 468                 char *str = "ld.so: malloc: cannot map pages\n";
 469                 (void)write(2, str, strlen(str));
 470                 return 0;
 471         }
 472         pagepool_end = pagepool_start + n * pagesz;
 473         pagepool_start += offset;
 474
 475 #ifdef NEED_DEV_ZERO
 476         close(fd);
 477 #endif
 478         return n;
 479 }