libexec/rtld-elf/malloc.c

   1 /*-
   2  * Copyright (c) 1983 Regents of the University of California.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  * @(#)malloc.c 5.11 (Berkeley) 2/23/91
  34  * $FreeBSD: src/libexec/rtld-elf/malloc.c,v 1.3.2.3 2003/02/20 20:42:46 kan Exp $
  35  * $DragonFly: src/libexec/rtld-elf/malloc.c,v 1.3 2008/06/05 18:01:49 swildner Exp $
  36  */
  37
  38 /*
  39  * malloc.c (Caltech) 2/21/82
  40  * Chris Kingsley, kingsley@cit-20.
  41  *
  42  * This is a very fast storage allocator.  It allocates blocks of a small
  43  * number of different sizes, and keeps free lists of each size.  Blocks that
  44  * don't exactly fit are passed up to the next larger size.  In this
  45  * implementation, the available sizes are 2^n-4 (or 2^n-10) bytes long.
  46  * This is designed for use in a virtual memory environment.
  47  */
  48
  49 #include <sys/types.h>
  50 #include <err.h>
  51 #include <paths.h>
  52 #include <stdarg.h>
  53 #include <stdio.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_COPY        MAP_PRIVATE
  61 #define MAP_FILE        0
  62 #define MAP_ANON        0
  63 #endif
  64
  65 #ifndef BSD             /* Need do better than this */
  66 #define NEED_DEV_ZERO   1
  67 #endif
  68
  69 static void morecore();
  70 static int findbucket();
  71
  72 /*
  73  * Pre-allocate mmap'ed pages
  74  */
  75 #define NPOOLPAGES      (32*1024/pagesz)
  76 static caddr_t          pagepool_start, pagepool_end;
  77 static int              morepages();
  78
  79 /*
  80  * The overhead on a block is at least 4 bytes.  When free, this space
  81  * contains a pointer to the next free block, and the bottom two bits must
  82  * be zero.  When in use, the first byte is set to MAGIC, and the second
  83  * byte is the size index.  The remaining bytes are for alignment.
  84  * If range checking is enabled then a second word holds the size of the
  85  * requested block, less 1, rounded up to a multiple of sizeof(RMAGIC).
  86  * The order of elements is critical: ov_magic must overlay the low order
  87  * bits of ov_next, and ov_magic can not be a valid ov_next bit pattern.
  88  */
  89 union   overhead {
  90         union   overhead *ov_next;      /* when free */
  91         struct {
  92                 u_char  ovu_magic;      /* magic number */
  93                 u_char  ovu_index;      /* bucket # */
  94 #ifdef RCHECK
  95                 u_short ovu_rmagic;     /* range magic number */
  96                 u_int   ovu_size;       /* actual block size */
  97 #endif
  98         } ovu;
  99 #define ov_magic        ovu.ovu_magic
 100 #define ov_index        ovu.ovu_index
 101 #define ov_rmagic       ovu.ovu_rmagic
 102 #define ov_size         ovu.ovu_size
 103 };
 104
 105 #define MAGIC           0xef            /* magic # on accounting info */
 106 #define RMAGIC          0x5555          /* magic # on range info */
 107
 108 #ifdef RCHECK
 109 #define RSLOP           sizeof (u_short)
 110 #else
 111 #define RSLOP           0
 112 #endif
 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(MALLOC_DEBUG) || defined(RCHECK)
 135 #define ASSERT(p)   if (!(p)) botch("p")
 136 #include <stdio.h>
 137 static void
 138 botch(s)
 139         char *s;
 140 {
 141         fprintf(stderr, "\r\nassertion botched: %s\r\n", s);
 142         (void) fflush(stderr);          /* just in case user buffered it */
 143         abort();
 144 }
 145 #else
 146 #define ASSERT(p)
 147 #endif
 148
 149 /* Debugging stuff */
 150 static void xprintf(const char *, ...);
 151 #define TRACE() xprintf("TRACE %s:%d\n", __FILE__, __LINE__)
 152
 153 void *
 154 malloc(nbytes)
 155         size_t nbytes;
 156 {
 157         register union overhead *op;
 158         register int bucket;
 159         register long n;
 160         register unsigned amt;
 161
 162         /*
 163          * First time malloc is called, setup page size and
 164          * align break pointer so all data will be page aligned.
 165          */
 166         if (pagesz == 0) {
 167                 pagesz = n = getpagesize();
 168                 if (morepages(NPOOLPAGES) == 0)
 169                         return NULL;
 170                 op = (union overhead *)(pagepool_start);
 171                 n = n - sizeof (*op) - ((long)op & (n - 1));
 172                 if (n < 0)
 173                         n += pagesz;
 174                 if (n) {
 175                         pagepool_start += n;
 176                 }
 177                 bucket = 0;
 178                 amt = 8;
 179                 while (pagesz > amt) {
 180                         amt <<= 1;
 181                         bucket++;
 182                 }
 183                 pagebucket = bucket;
 184         }
 185         /*
 186          * Convert amount of memory requested into closest block size
 187          * stored in hash buckets which satisfies request.
 188          * Account for space used per block for accounting.
 189          */
 190         if (nbytes <= (n = pagesz - sizeof (*op) - RSLOP)) {
 191 #ifndef RCHECK
 192                 amt = 8;        /* size of first bucket */
 193                 bucket = 0;
 194 #else
 195                 amt = 16;       /* size of first bucket */
 196                 bucket = 1;
 197 #endif
 198                 n = -(sizeof (*op) + RSLOP);
 199         } else {
 200                 amt = pagesz;
 201                 bucket = pagebucket;
 202         }
 203         while (nbytes > amt + n) {
 204                 amt <<= 1;
 205                 if (amt == 0)
 206                         return (NULL);
 207                 bucket++;
 208         }
 209         /*
 210          * If nothing in hash bucket right now,
 211          * request more memory from the system.
 212          */
 213         if ((op = nextf[bucket]) == NULL) {
 214                 morecore(bucket);
 215                 if ((op = nextf[bucket]) == NULL)
 216                         return (NULL);
 217         }
 218         /* remove from linked list */
 219         nextf[bucket] = op->ov_next;
 220         op->ov_magic = MAGIC;
 221         op->ov_index = bucket;
 222 #ifdef MSTATS
 223         nmalloc[bucket]++;
 224 #endif
 225 #ifdef RCHECK
 226         /*
 227          * Record allocated size of block and
 228          * bound space with magic numbers.
 229          */
 230         op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
 231         op->ov_rmagic = RMAGIC;
 232         *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
 233 #endif
 234         return ((char *)(op + 1));
 235 }
 236
 237 /*
 238  * Allocate more memory to the indicated bucket.
 239  */
 240 static void
 241 morecore(bucket)
 242         int bucket;
 243 {
 244         register union overhead *op;
 245         register int sz;                /* size of desired block */
 246         int amt;                        /* amount to allocate */
 247         int nblks;                      /* how many blocks we get */
 248
 249         /*
 250          * sbrk_size <= 0 only for big, FLUFFY, requests (about
 251          * 2^30 bytes on a VAX, I think) or for a negative arg.
 252          */
 253         sz = 1 << (bucket + 3);
 254 #ifdef MALLOC_DEBUG
 255         ASSERT(sz > 0);
 256 #else
 257         if (sz <= 0)
 258                 return;
 259 #endif
 260         if (sz < pagesz) {
 261                 amt = pagesz;
 262                 nblks = amt / sz;
 263         } else {
 264                 amt = sz + pagesz;
 265                 nblks = 1;
 266         }
 267         if (amt > pagepool_end - pagepool_start)
 268                 if (morepages(amt/pagesz + NPOOLPAGES) == 0)
 269                         return;
 270         op = (union overhead *)pagepool_start;
 271         pagepool_start += amt;
 272
 273         /*
 274          * Add new memory allocated to that on
 275          * free list for this hash bucket.
 276          */
 277         nextf[bucket] = op;
 278         while (--nblks > 0) {
 279                 op->ov_next = (union overhead *)((caddr_t)op + sz);
 280                 op = (union overhead *)((caddr_t)op + sz);
 281         }
 282 }
 283
 284 void
 285 free(cp)
 286         void *cp;
 287 {
 288         register int size;
 289         register union overhead *op;
 290
 291         if (cp == NULL)
 292                 return;
 293         op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
 294 #ifdef MALLOC_DEBUG
 295         ASSERT(op->ov_magic == MAGIC);          /* make sure it was in use */
 296 #else
 297         if (op->ov_magic != MAGIC)
 298                 return;                         /* sanity */
 299 #endif
 300 #ifdef RCHECK
 301         ASSERT(op->ov_rmagic == RMAGIC);
 302         ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC);
 303 #endif
 304         size = op->ov_index;
 305         ASSERT(size < NBUCKETS);
 306         op->ov_next = nextf[size];      /* also clobbers ov_magic */
 307         nextf[size] = op;
 308 #ifdef MSTATS
 309         nmalloc[size]--;
 310 #endif
 311 }
 312
 313 /*
 314  * When a program attempts "storage compaction" as mentioned in the
 315  * old malloc man page, it realloc's an already freed block.  Usually
 316  * this is the last block it freed; occasionally it might be farther
 317  * back.  We have to search all the free lists for the block in order
 318  * to determine its bucket: 1st we make one pass thru the lists
 319  * checking only the first block in each; if that fails we search
 320  * ``realloc_srchlen'' blocks in each list for a match (the variable
 321  * is extern so the caller can modify it).  If that fails we just copy
 322  * however many bytes was given to realloc() and hope it's not huge.
 323  */
 324 int realloc_srchlen = 4;        /* 4 should be plenty, -1 =>'s whole list */
 325
 326 void *
 327 realloc(cp, nbytes)
 328         void *cp;
 329         size_t nbytes;
 330 {
 331         register u_int onb;
 332         register int i;
 333         union overhead *op;
 334         char *res;
 335         int was_alloced = 0;
 336
 337         if (cp == NULL)
 338                 return (malloc(nbytes));
 339         op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
 340         if (op->ov_magic == MAGIC) {
 341                 was_alloced++;
 342                 i = op->ov_index;
 343         } else {
 344                 /*
 345                  * Already free, doing "compaction".
 346                  *
 347                  * Search for the old block of memory on the
 348                  * free list.  First, check the most common
 349                  * case (last element free'd), then (this failing)
 350                  * the last ``realloc_srchlen'' items free'd.
 351                  * If all lookups fail, then assume the size of
 352                  * the memory block being realloc'd is the
 353                  * largest possible (so that all "nbytes" of new
 354                  * memory are copied into).  Note that this could cause
 355                  * a memory fault if the old area was tiny, and the moon
 356                  * is gibbous.  However, that is very unlikely.
 357                  */
 358                 if ((i = findbucket(op, 1)) < 0 &&
 359                     (i = findbucket(op, realloc_srchlen)) < 0)
 360                         i = NBUCKETS;
 361         }
 362         onb = 1 << (i + 3);
 363         if (onb < pagesz)
 364                 onb -= sizeof (*op) + RSLOP;
 365         else
 366                 onb += pagesz - sizeof (*op) - RSLOP;
 367         /* avoid the copy if same size block */
 368         if (was_alloced) {
 369                 if (i) {
 370                         i = 1 << (i + 2);
 371                         if (i < pagesz)
 372                                 i -= sizeof (*op) + RSLOP;
 373                         else
 374                                 i += pagesz - sizeof (*op) - RSLOP;
 375                 }
 376                 if (nbytes <= onb && nbytes > i) {
 377 #ifdef RCHECK
 378                         op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
 379                         *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
 380 #endif
 381                         return(cp);
 382                 } else
 383                         free(cp);
 384         }
 385         if ((res = malloc(nbytes)) == NULL)
 386                 return (NULL);
 387         if (cp != res)          /* common optimization if "compacting" */
 388                 bcopy(cp, res, (nbytes < onb) ? nbytes : onb);
 389         return (res);
 390 }
 391
 392 /*
 393  * Search ``srchlen'' elements of each free list for a block whose
 394  * header starts at ``freep''.  If srchlen is -1 search the whole list.
 395  * Return bucket number, or -1 if not found.
 396  */
 397 static int
 398 findbucket(freep, srchlen)
 399         union overhead *freep;
 400         int srchlen;
 401 {
 402         register union overhead *p;
 403         register int i, j;
 404
 405         for (i = 0; i < NBUCKETS; i++) {
 406                 j = 0;
 407                 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
 408                         if (p == freep)
 409                                 return (i);
 410                         j++;
 411                 }
 412         }
 413         return (-1);
 414 }
 415
 416 #ifdef MSTATS
 417 /*
 418  * mstats - print out statistics about malloc
 419  *
 420  * Prints two lines of numbers, one showing the length of the free list
 421  * for each size category, the second showing the number of mallocs -
 422  * frees for each size category.
 423  */
 424 mstats(s)
 425         char *s;
 426 {
 427         register int i, j;
 428         register union overhead *p;
 429         int totfree = 0,
 430         totused = 0;
 431
 432         fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s);
 433         for (i = 0; i < NBUCKETS; i++) {
 434                 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
 435                         ;
 436                 fprintf(stderr, " %d", j);
 437                 totfree += j * (1 << (i + 3));
 438         }
 439         fprintf(stderr, "\nused:\t");
 440         for (i = 0; i < NBUCKETS; i++) {
 441                 fprintf(stderr, " %d", nmalloc[i]);
 442                 totused += nmalloc[i] * (1 << (i + 3));
 443         }
 444         fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n",
 445             totused, totfree);
 446 }
 447 #endif
 448
 449
 450 static int
 451 morepages(n)
 452 int     n;
 453 {
 454         int     fd = -1;
 455         int     offset;
 456
 457 #ifdef NEED_DEV_ZERO
 458         fd = open(_PATH_DEVZERO, O_RDWR, 0);
 459         if (fd == -1)
 460                 perror(_PATH_DEVZERO);
 461 #endif
 462
 463         if (pagepool_end - pagepool_start > pagesz) {
 464                 caddr_t addr = (caddr_t)
 465                         (((long)pagepool_start + pagesz - 1) & ~(pagesz - 1));
 466                 if (munmap(addr, pagepool_end - addr) != 0)
 467                         warn("morepages: munmap %p", addr);
 468         }
 469
 470         offset = (long)pagepool_start - ((long)pagepool_start & ~(pagesz - 1));
 471
 472         if ((pagepool_start = mmap(0, n * pagesz,
 473                         PROT_READ|PROT_WRITE,
 474                         MAP_ANON|MAP_COPY, fd, 0)) == (caddr_t)-1) {
 475                 xprintf("Cannot map anonymous memory");
 476                 return 0;
 477         }
 478         pagepool_end = pagepool_start + n * pagesz;
 479         pagepool_start += offset;
 480
 481 #ifdef NEED_DEV_ZERO
 482         close(fd);
 483 #endif
 484         return n;
 485 }
 486
 487 /*
 488  * Non-mallocing printf, for use by malloc itself.
 489  */
 490 static void
 491 xprintf(const char *fmt, ...)
 492 {
 493     char buf[256];
 494     va_list ap;
 495
 496     va_start(ap, fmt);
 497     vsprintf(buf, fmt, ap);
 498     (void)write(STDOUT_FILENO, buf, strlen(buf));
 499     va_end(ap);
 500 }