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 1.2 2003/06/17 06:27:08 dillon 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 #define NULL 0
  70
  71 static void morecore();
  72 static int findbucket();
  73
  74 /*
  75  * Pre-allocate mmap'ed pages
  76  */
  77 #define NPOOLPAGES      (32*1024/pagesz)
  78 static caddr_t          pagepool_start, pagepool_end;
  79 static int              morepages();
  80
  81 /*
  82  * The overhead on a block is at least 4 bytes.  When free, this space
  83  * contains a pointer to the next free block, and the bottom two bits must
  84  * be zero.  When in use, the first byte is set to MAGIC, and the second
  85  * byte is the size index.  The remaining bytes are for alignment.
  86  * If range checking is enabled then a second word holds the size of the
  87  * requested block, less 1, rounded up to a multiple of sizeof(RMAGIC).
  88  * The order of elements is critical: ov_magic must overlay the low order
  89  * bits of ov_next, and ov_magic can not be a valid ov_next bit pattern.
  90  */
  91 union   overhead {
  92         union   overhead *ov_next;      /* when free */
  93         struct {
  94                 u_char  ovu_magic;      /* magic number */
  95                 u_char  ovu_index;      /* bucket # */
  96 #ifdef RCHECK
  97                 u_short ovu_rmagic;     /* range magic number */
  98                 u_int   ovu_size;       /* actual block size */
  99 #endif
 100         } ovu;
 101 #define ov_magic        ovu.ovu_magic
 102 #define ov_index        ovu.ovu_index
 103 #define ov_rmagic       ovu.ovu_rmagic
 104 #define ov_size         ovu.ovu_size
 105 };
 106
 107 #define MAGIC           0xef            /* magic # on accounting info */
 108 #define RMAGIC          0x5555          /* magic # on range info */
 109
 110 #ifdef RCHECK
 111 #define RSLOP           sizeof (u_short)
 112 #else
 113 #define RSLOP           0
 114 #endif
 115
 116 /*
 117  * nextf[i] is the pointer to the next free block of size 2^(i+3).  The
 118  * smallest allocatable block is 8 bytes.  The overhead information
 119  * precedes the data area returned to the user.
 120  */
 121 #define NBUCKETS 30
 122 static  union overhead *nextf[NBUCKETS];
 123
 124 static  int pagesz;                     /* page size */
 125 static  int pagebucket;                 /* page size bucket */
 126
 127 #ifdef MSTATS
 128 /*
 129  * nmalloc[i] is the difference between the number of mallocs and frees
 130  * for a given block size.
 131  */
 132 static  u_int nmalloc[NBUCKETS];
 133 #include <stdio.h>
 134 #endif
 135
 136 #if defined(MALLOC_DEBUG) || defined(RCHECK)
 137 #define ASSERT(p)   if (!(p)) botch("p")
 138 #include <stdio.h>
 139 static void
 140 botch(s)
 141         char *s;
 142 {
 143         fprintf(stderr, "\r\nassertion botched: %s\r\n", s);
 144         (void) fflush(stderr);          /* just in case user buffered it */
 145         abort();
 146 }
 147 #else
 148 #define ASSERT(p)
 149 #endif
 150
 151 /* Debugging stuff */
 152 static void xprintf(const char *, ...);
 153 #define TRACE() xprintf("TRACE %s:%d\n", __FILE__, __LINE__)
 154
 155 void *
 156 malloc(nbytes)
 157         size_t nbytes;
 158 {
 159         register union overhead *op;
 160         register int bucket;
 161         register long n;
 162         register unsigned amt;
 163
 164         /*
 165          * First time malloc is called, setup page size and
 166          * align break pointer so all data will be page aligned.
 167          */
 168         if (pagesz == 0) {
 169                 pagesz = n = getpagesize();
 170                 if (morepages(NPOOLPAGES) == 0)
 171                         return NULL;
 172                 op = (union overhead *)(pagepool_start);
 173                 n = n - sizeof (*op) - ((long)op & (n - 1));
 174                 if (n < 0)
 175                         n += pagesz;
 176                 if (n) {
 177                         pagepool_start += n;
 178                 }
 179                 bucket = 0;
 180                 amt = 8;
 181                 while (pagesz > amt) {
 182                         amt <<= 1;
 183                         bucket++;
 184                 }
 185                 pagebucket = bucket;
 186         }
 187         /*
 188          * Convert amount of memory requested into closest block size
 189          * stored in hash buckets which satisfies request.
 190          * Account for space used per block for accounting.
 191          */
 192         if (nbytes <= (n = pagesz - sizeof (*op) - RSLOP)) {
 193 #ifndef RCHECK
 194                 amt = 8;        /* size of first bucket */
 195                 bucket = 0;
 196 #else
 197                 amt = 16;       /* size of first bucket */
 198                 bucket = 1;
 199 #endif
 200                 n = -(sizeof (*op) + RSLOP);
 201         } else {
 202                 amt = pagesz;
 203                 bucket = pagebucket;
 204         }
 205         while (nbytes > amt + n) {
 206                 amt <<= 1;
 207                 if (amt == 0)
 208                         return (NULL);
 209                 bucket++;
 210         }
 211         /*
 212          * If nothing in hash bucket right now,
 213          * request more memory from the system.
 214          */
 215         if ((op = nextf[bucket]) == NULL) {
 216                 morecore(bucket);
 217                 if ((op = nextf[bucket]) == NULL)
 218                         return (NULL);
 219         }
 220         /* remove from linked list */
 221         nextf[bucket] = op->ov_next;
 222         op->ov_magic = MAGIC;
 223         op->ov_index = bucket;
 224 #ifdef MSTATS
 225         nmalloc[bucket]++;
 226 #endif
 227 #ifdef RCHECK
 228         /*
 229          * Record allocated size of block and
 230          * bound space with magic numbers.
 231          */
 232         op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
 233         op->ov_rmagic = RMAGIC;
 234         *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
 235 #endif
 236         return ((char *)(op + 1));
 237 }
 238
 239 /*
 240  * Allocate more memory to the indicated bucket.
 241  */
 242 static void
 243 morecore(bucket)
 244         int bucket;
 245 {
 246         register union overhead *op;
 247         register int sz;                /* size of desired block */
 248         int amt;                        /* amount to allocate */
 249         int nblks;                      /* how many blocks we get */
 250
 251         /*
 252          * sbrk_size <= 0 only for big, FLUFFY, requests (about
 253          * 2^30 bytes on a VAX, I think) or for a negative arg.
 254          */
 255         sz = 1 << (bucket + 3);
 256 #ifdef MALLOC_DEBUG
 257         ASSERT(sz > 0);
 258 #else
 259         if (sz <= 0)
 260                 return;
 261 #endif
 262         if (sz < pagesz) {
 263                 amt = pagesz;
 264                 nblks = amt / sz;
 265         } else {
 266                 amt = sz + pagesz;
 267                 nblks = 1;
 268         }
 269         if (amt > pagepool_end - pagepool_start)
 270                 if (morepages(amt/pagesz + NPOOLPAGES) == 0)
 271                         return;
 272         op = (union overhead *)pagepool_start;
 273         pagepool_start += amt;
 274
 275         /*
 276          * Add new memory allocated to that on
 277          * free list for this hash bucket.
 278          */
 279         nextf[bucket] = op;
 280         while (--nblks > 0) {
 281                 op->ov_next = (union overhead *)((caddr_t)op + sz);
 282                 op = (union overhead *)((caddr_t)op + sz);
 283         }
 284 }
 285
 286 void
 287 free(cp)
 288         void *cp;
 289 {
 290         register int size;
 291         register union overhead *op;
 292
 293         if (cp == NULL)
 294                 return;
 295         op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
 296 #ifdef MALLOC_DEBUG
 297         ASSERT(op->ov_magic == MAGIC);          /* make sure it was in use */
 298 #else
 299         if (op->ov_magic != MAGIC)
 300                 return;                         /* sanity */
 301 #endif
 302 #ifdef RCHECK
 303         ASSERT(op->ov_rmagic == RMAGIC);
 304         ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC);
 305 #endif
 306         size = op->ov_index;
 307         ASSERT(size < NBUCKETS);
 308         op->ov_next = nextf[size];      /* also clobbers ov_magic */
 309         nextf[size] = op;
 310 #ifdef MSTATS
 311         nmalloc[size]--;
 312 #endif
 313 }
 314
 315 /*
 316  * When a program attempts "storage compaction" as mentioned in the
 317  * old malloc man page, it realloc's an already freed block.  Usually
 318  * this is the last block it freed; occasionally it might be farther
 319  * back.  We have to search all the free lists for the block in order
 320  * to determine its bucket: 1st we make one pass thru the lists
 321  * checking only the first block in each; if that fails we search
 322  * ``realloc_srchlen'' blocks in each list for a match (the variable
 323  * is extern so the caller can modify it).  If that fails we just copy
 324  * however many bytes was given to realloc() and hope it's not huge.
 325  */
 326 int realloc_srchlen = 4;        /* 4 should be plenty, -1 =>'s whole list */
 327
 328 void *
 329 realloc(cp, nbytes)
 330         void *cp;
 331         size_t nbytes;
 332 {
 333         register u_int onb;
 334         register int i;
 335         union overhead *op;
 336         char *res;
 337         int was_alloced = 0;
 338
 339         if (cp == NULL)
 340                 return (malloc(nbytes));
 341         op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
 342         if (op->ov_magic == MAGIC) {
 343                 was_alloced++;
 344                 i = op->ov_index;
 345         } else {
 346                 /*
 347                  * Already free, doing "compaction".
 348                  *
 349                  * Search for the old block of memory on the
 350                  * free list.  First, check the most common
 351                  * case (last element free'd), then (this failing)
 352                  * the last ``realloc_srchlen'' items free'd.
 353                  * If all lookups fail, then assume the size of
 354                  * the memory block being realloc'd is the
 355                  * largest possible (so that all "nbytes" of new
 356                  * memory are copied into).  Note that this could cause
 357                  * a memory fault if the old area was tiny, and the moon
 358                  * is gibbous.  However, that is very unlikely.
 359                  */
 360                 if ((i = findbucket(op, 1)) < 0 &&
 361                     (i = findbucket(op, realloc_srchlen)) < 0)
 362                         i = NBUCKETS;
 363         }
 364         onb = 1 << (i + 3);
 365         if (onb < pagesz)
 366                 onb -= sizeof (*op) + RSLOP;
 367         else
 368                 onb += pagesz - sizeof (*op) - RSLOP;
 369         /* avoid the copy if same size block */
 370         if (was_alloced) {
 371                 if (i) {
 372                         i = 1 << (i + 2);
 373                         if (i < pagesz)
 374                                 i -= sizeof (*op) + RSLOP;
 375                         else
 376                                 i += pagesz - sizeof (*op) - RSLOP;
 377                 }
 378                 if (nbytes <= onb && nbytes > i) {
 379 #ifdef RCHECK
 380                         op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
 381                         *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
 382 #endif
 383                         return(cp);
 384                 } else
 385                         free(cp);
 386         }
 387         if ((res = malloc(nbytes)) == NULL)
 388                 return (NULL);
 389         if (cp != res)          /* common optimization if "compacting" */
 390                 bcopy(cp, res, (nbytes < onb) ? nbytes : onb);
 391         return (res);
 392 }
 393
 394 /*
 395  * Search ``srchlen'' elements of each free list for a block whose
 396  * header starts at ``freep''.  If srchlen is -1 search the whole list.
 397  * Return bucket number, or -1 if not found.
 398  */
 399 static int
 400 findbucket(freep, srchlen)
 401         union overhead *freep;
 402         int srchlen;
 403 {
 404         register union overhead *p;
 405         register int i, j;
 406
 407         for (i = 0; i < NBUCKETS; i++) {
 408                 j = 0;
 409                 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
 410                         if (p == freep)
 411                                 return (i);
 412                         j++;
 413                 }
 414         }
 415         return (-1);
 416 }
 417
 418 #ifdef MSTATS
 419 /*
 420  * mstats - print out statistics about malloc
 421  *
 422  * Prints two lines of numbers, one showing the length of the free list
 423  * for each size category, the second showing the number of mallocs -
 424  * frees for each size category.
 425  */
 426 mstats(s)
 427         char *s;
 428 {
 429         register int i, j;
 430         register union overhead *p;
 431         int totfree = 0,
 432         totused = 0;
 433
 434         fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s);
 435         for (i = 0; i < NBUCKETS; i++) {
 436                 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
 437                         ;
 438                 fprintf(stderr, " %d", j);
 439                 totfree += j * (1 << (i + 3));
 440         }
 441         fprintf(stderr, "\nused:\t");
 442         for (i = 0; i < NBUCKETS; i++) {
 443                 fprintf(stderr, " %d", nmalloc[i]);
 444                 totused += nmalloc[i] * (1 << (i + 3));
 445         }
 446         fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n",
 447             totused, totfree);
 448 }
 449 #endif
 450
 451
 452 static int
 453 morepages(n)
 454 int     n;
 455 {
 456         int     fd = -1;
 457         int     offset;
 458
 459 #ifdef NEED_DEV_ZERO
 460         fd = open(_PATH_DEVZERO, O_RDWR, 0);
 461         if (fd == -1)
 462                 perror(_PATH_DEVZERO);
 463 #endif
 464
 465         if (pagepool_end - pagepool_start > pagesz) {
 466                 caddr_t addr = (caddr_t)
 467                         (((long)pagepool_start + pagesz - 1) & ~(pagesz - 1));
 468                 if (munmap(addr, pagepool_end - addr) != 0)
 469                         warn("morepages: munmap %p", addr);
 470         }
 471
 472         offset = (long)pagepool_start - ((long)pagepool_start & ~(pagesz - 1));
 473
 474         if ((pagepool_start = mmap(0, n * pagesz,
 475                         PROT_READ|PROT_WRITE,
 476                         MAP_ANON|MAP_COPY, fd, 0)) == (caddr_t)-1) {
 477                 xprintf("Cannot map anonymous memory");
 478                 return 0;
 479         }
 480         pagepool_end = pagepool_start + n * pagesz;
 481         pagepool_start += offset;
 482
 483 #ifdef NEED_DEV_ZERO
 484         close(fd);
 485 #endif
 486         return n;
 487 }
 488
 489 /*
 490  * Non-mallocing printf, for use by malloc itself.
 491  */
 492 static void
 493 xprintf(const char *fmt, ...)
 494 {
 495     char buf[256];
 496     va_list ap;
 497
 498     va_start(ap, fmt);
 499     vsprintf(buf, fmt, ap);
 500     (void)write(STDOUT_FILENO, buf, strlen(buf));
 501     va_end(ap);
 502 }