usr/src/lib/libbsdmalloc/common/malloc.bsd43.c

   1 /*
   2  * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
   3  * Use is subject to license terms.
   4  */
   5
   6 #pragma ident   "%Z%%M% %I%     %E% SMI"
   7 /*
   8  * wizard:/space/4.3reno/usr/src/lib/libc/stdlib/malloc.c
   9  * Copyright (c) 1983 Regents of the University of California.
  10  * All rights reserved.
  11  *
  12  * Redistribution and use in source and binary forms are permitted
  13  * provided that: (1) source distributions retain this entire copyright
  14  * notice and comment, and (2) distributions including binaries display
  15  * the following acknowledgement:  ``This product includes software
  16  * developed by the University of California, Berkeley and its contributors''
  17  * in the documentation or other materials provided with the distribution
  18  * and in all advertising materials mentioning features or use of this
  19  * software. Neither the name of the University nor the names of its
  20  * contributors may be used to endorse or promote products derived
  21  * from this software without specific prior written permission.
  22  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
  23  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
  24  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  25  */
  26
  27 /*
  28  * malloc.c (Caltech) 2/21/82
  29  * Chris Kingsley, kingsley@cit-20.
  30  *
  31  * This is a very fast storage allocator.  It allocates blocks of a small
  32  * number of different sizes, and keeps free lists of each size.  Blocks that
  33  * don't exactly fit are passed up to the next larger size.  In this
  34  * implementation, the available sizes are 2^n-4 bytes long (ILP32)
  35  * or 2^n-8 bytes long (LP64).
  36  */
  37
  38 /*LINTLIBRARY*/
  39 #include <sys/types.h>
  40 #include <stdlib.h>
  41 #include <unistd.h>
  42 #include <string.h>
  43 #include <limits.h>
  44
  45 /*
  46  * The overhead on a block is at least 4 bytes.  When free, this space
  47  * contains a pointer to the next free block, and the bottom two bits must
  48  * be zero.  When in use, the first byte is set to MAGIC, and the second
  49  * byte is the size index.  The remaining bytes are for alignment.
  50  * The order of elements is critical: ov_magic must overlay the low order
  51  * bits of ov_next, and ov_magic can not be a valid ov_next bit pattern.
  52  * Overhead is 4 bytes for ILP32, 8 bytes for LP64
  53  */
  54 union   overhead {
  55         union   overhead *ov_next;      /* when free */
  56         struct {
  57 #if defined(_LITTLE_ENDIAN)
  58                 uchar_t ovu_magic;      /* magic number */
  59                 uchar_t ovu_index;      /* bucket # */
  60                 uchar_t ovu_pad[sizeof (union overhead *) - 2];
  61 #elif defined(_BIG_ENDIAN)
  62                 uchar_t ovu_pad[sizeof (union overhead *) - 2];
  63                 uchar_t ovu_index;      /* bucket # */
  64                 uchar_t ovu_magic;      /* magic number */
  65 #else
  66 #error "Endianness is not defined"
  67 #endif
  68         } ovu;
  69 };
  70
  71 #define ov_magic        ovu.ovu_magic
  72 #define ov_index        ovu.ovu_index
  73
  74 #define MAGIC           0xef            /* magic # on accounting info */
  75
  76 /*
  77  * nextf[i] is the pointer to the next free block of size 2^(i+EXP).
  78  * The smallest allocatable block is 8 bytes (ILP32) or 16 bytes (LP64).
  79  * The overhead information precedes the data area returned to the user.
  80  */
  81 #ifdef _LP64
  82 #define EXP     4
  83 #define NBUCKETS 60
  84 #else
  85 #define EXP     3
  86 #define NBUCKETS 29
  87 #endif
  88 static  union overhead *nextf[NBUCKETS];
  89
  90 static  int     pagesz;                 /* page size */
  91 static  long    sbrk_adjust;            /* in case sbrk() does alignment */
  92 static  int     pagebucket;             /* page size bucket */
  93 static  void    morecore(int);
  94 static  int     findbucket(union overhead *, int);
  95
  96 void *
  97 malloc(size_t nbytes)
  98 {
  99         union overhead *op;
 100         int bucket;
 101         ssize_t n;
 102         size_t amt;
 103
 104         /*
 105          * First time malloc is called, setup page size and
 106          * align break pointer so all data will be page aligned.
 107          */
 108         if (pagesz == 0) {
 109                 pagesz = getpagesize();
 110                 op = sbrk(0);
 111                 n = pagesz - sizeof (*op) - ((uintptr_t)op & (pagesz - 1));
 112                 if (n < 0)
 113                         n += pagesz;
 114                 if (n) {
 115                         if (sbrk(n) == (void *)-1)
 116                                 return (NULL);
 117                         /*
 118                          * We were careful to arrange that
 119                          * sbrk(0) + sizeof (union overhead)
 120                          * should end up on a page boundary.
 121                          * If the underlying sbrk() performs alignment
 122                          * then this is false.  We compute the adjustment.
 123                          */
 124                         op = sbrk(0);
 125                         sbrk_adjust = (uintptr_t)(op + 1) & (pagesz - 1);
 126                 } else {
 127                         sbrk_adjust = 0;
 128                 }
 129                 bucket = 0;
 130                 amt = (1UL << EXP);
 131                 while (pagesz > amt) {
 132                         amt <<= 1;
 133                         bucket++;
 134                 }
 135                 pagebucket = bucket;
 136         }
 137         /*
 138          * Convert amount of memory requested into closest block size
 139          * stored in hash buckets which satisfies request.
 140          * Account for space used per block for accounting.
 141          */
 142         if (nbytes <= (n = pagesz - sizeof (*op))) {
 143                 amt = (1UL << EXP);     /* size of first bucket */
 144                 bucket = 0;
 145                 n = -(ssize_t)(sizeof (*op));
 146         } else {
 147                 amt = pagesz;
 148                 bucket = pagebucket;
 149         }
 150         while (nbytes > amt + n) {
 151                 amt <<= 1;
 152                 if (amt == 0)
 153                         return (NULL);
 154                 bucket++;
 155         }
 156         /*
 157          * If nothing in hash bucket right now,
 158          * request more memory from the system.
 159          */
 160         if ((op = nextf[bucket]) == NULL) {
 161                 morecore(bucket);
 162                 if ((op = nextf[bucket]) == NULL)
 163                         return (NULL);
 164         }
 165         /* remove from linked list */
 166         nextf[bucket] = op->ov_next;
 167         op->ov_magic = MAGIC;
 168         op->ov_index = (uchar_t)bucket;
 169         return (op + 1);
 170 }
 171
 172 /*
 173  * Allocate more memory to the indicated bucket.
 174  */
 175 static void
 176 morecore(int bucket)
 177 {
 178         union overhead *op;
 179         size_t sz;                      /* size of desired block */
 180         ssize_t amt;                    /* amount to allocate */
 181         long nblks;                     /* how many blocks we get */
 182
 183         sz = 1UL << (bucket + EXP);
 184         if (sz == 0)
 185                 return;
 186         if (sz < pagesz) {
 187                 amt = pagesz;
 188                 nblks = amt / sz;
 189         } else {
 190                 amt = sz + pagesz;
 191                 nblks = 1;
 192         }
 193         if (amt <= 0)
 194                 return;
 195         if (amt > LONG_MAX) {
 196                 intptr_t        delta;
 197                 /*
 198                  * the value required is too big for sbrk() to deal with
 199                  * in one go, so use sbrk() at most 2 times instead.
 200                  */
 201                 op = sbrk(0);
 202                 delta = LONG_MAX;
 203                 while (delta > 0) {
 204                         if (sbrk(delta) == (void *)-1) {
 205                                 if (op != sbrk(0))
 206                                         (void) sbrk(-LONG_MAX);
 207                                 return;
 208                         }
 209                         amt -= LONG_MAX;
 210                         delta = amt;
 211                 }
 212         }
 213         else
 214                 op = sbrk(amt);
 215         /* no more room! */
 216         if (op == (union overhead *)-1)
 217                 return;
 218         /* LINTED improper alignment */
 219         op = (union overhead *)((caddr_t)op - sbrk_adjust);
 220         /*
 221          * Add new memory allocated to that on
 222          * free list for this hash bucket.
 223          */
 224         nextf[bucket] = op;
 225         while (--nblks > 0) {
 226                 /* LINTED improper alignment */
 227                 op->ov_next = (union overhead *)((caddr_t)op + sz);
 228                 /* LINTED improper alignment */
 229                 op = (union overhead *)((caddr_t)op + sz);
 230         }
 231 }
 232
 233 void
 234 free(void *cp)
 235 {
 236         int size;
 237         union overhead *op;
 238
 239         if (cp == NULL)
 240                 return;
 241         /* LINTED improper alignment */
 242         op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
 243         if (op->ov_magic != MAGIC)
 244                 return;                 /* previously freed? */
 245         size = op->ov_index;
 246         op->ov_next = nextf[size];      /* also clobbers ov_magic */
 247         nextf[size] = op;
 248 }
 249
 250 /*
 251  * When a program attempts "storage compaction" as mentioned in the
 252  * old malloc man page, it realloc's an already freed block.  Usually
 253  * this is the last block it freed; occasionally it might be farther
 254  * back.  We have to search all the free lists for the block in order
 255  * to determine its bucket: 1st we make one pass thru the lists
 256  * checking only the first block in each; if that fails we search
 257  * ``realloc_srchlen'' blocks in each list for a match (the variable
 258  * is extern so the caller can modify it).  If that fails we just copy
 259  * however many bytes was given to realloc() and hope it's not huge.
 260  */
 261 int realloc_srchlen = 4;        /* 4 should be plenty, -1 =>'s whole list */
 262
 263 void *
 264 realloc(void *cp, size_t nbytes)
 265 {
 266         size_t onb;
 267         int i;
 268         union overhead *op;
 269         char *res;
 270         int was_alloced = 0;
 271
 272         if (cp == NULL)
 273                 return (malloc(nbytes));
 274         /* LINTED improper alignment */
 275         op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
 276         if (op->ov_magic == MAGIC) {
 277                 was_alloced++;
 278                 i = op->ov_index;
 279         } else {
 280                 /*
 281                  * Already free, doing "compaction".
 282                  *
 283                  * Search for the old block of memory on the
 284                  * free list.  First, check the most common
 285                  * case (last element free'd), then (this failing)
 286                  * the last ``realloc_srchlen'' items free'd.
 287                  * If all lookups fail, then just malloc() the
 288                  * space and copy the size of the new space.
 289                  */
 290                 if ((i = findbucket(op, 1)) < 0 &&
 291                     (i = findbucket(op, realloc_srchlen)) < 0) {
 292                         if ((res = malloc(nbytes)) != NULL)
 293                                 (void) memmove(res, cp, nbytes);
 294                         return (res);
 295                 }
 296         }
 297         onb = 1UL << (i + EXP);
 298         if (onb < pagesz)
 299                 onb -= sizeof (*op);
 300         else
 301                 onb += pagesz - sizeof (*op);
 302         /* avoid the copy if same size block */
 303         if (was_alloced) {
 304                 size_t sz = 0;
 305                 if (i) {
 306                         sz = 1UL << (i + EXP - 1);
 307                         if (sz < pagesz)
 308                                 sz -= sizeof (*op);
 309                         else
 310                                 sz += pagesz - sizeof (*op);
 311                 }
 312                 if (nbytes <= onb && nbytes > sz) {
 313                         return (cp);
 314                 } else
 315                         free(cp);
 316         }
 317         if ((res = malloc(nbytes)) == NULL)
 318                 return (NULL);
 319         if (cp != res)          /* common optimization if "compacting" */
 320                 (void) memmove(res, cp, (nbytes < onb) ? nbytes : onb);
 321         return (res);
 322 }
 323
 324 /*
 325  * Search ``srchlen'' elements of each free list for a block whose
 326  * header starts at ``freep''.  If srchlen is -1 search the whole list.
 327  * Return bucket number, or -1 if not found.
 328  */
 329 static int
 330 findbucket(union overhead *freep, int srchlen)
 331 {
 332         union overhead *p;
 333         int i, j;
 334
 335         for (i = 0; i < NBUCKETS; i++) {
 336                 j = 0;
 337                 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
 338                         if (p == freep)
 339                                 return (i);
 340                         j++;
 341                 }
 342         }
 343         return (-1);
 344 }