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
  34 #if defined(LIBC_SCCS) && !defined(lint)
  35 /*static char *sccsid = "from: @(#)malloc.c     5.11 (Berkeley) 2/23/91";*/
  36 static char *rcsid = "$FreeBSD$";
  37 #endif /* LIBC_SCCS and not lint */
  38
  39 /*
  40  * malloc.c (Caltech) 2/21/82
  41  * Chris Kingsley, kingsley@cit-20.
  42  *
  43  * This is a very fast storage allocator.  It allocates blocks of a small
  44  * number of different sizes, and keeps free lists of each size.  Blocks that
  45  * don't exactly fit are passed up to the next larger size.  In this
  46  * implementation, the available sizes are 2^n-4 (or 2^n-10) bytes long.
  47  * This is designed for use in a virtual memory environment.
  48  */
  49
  50 #include <sys/types.h>
  51 #include <err.h>
  52 #include <paths.h>
  53 #include <stdarg.h>
  54 #include <stddef.h>
  55 #include <stdio.h>
  56 #include <stdlib.h>
  57 #include <string.h>
  58 #include <unistd.h>
  59 #include <sys/param.h>
  60 #include <sys/mman.h>
  61 #ifndef BSD
  62 #define MAP_COPY        MAP_PRIVATE
  63 #define MAP_FILE        0
  64 #define MAP_ANON        0
  65 #endif
  66
  67 #ifndef BSD             /* Need do better than this */
  68 #define NEED_DEV_ZERO   1
  69 #endif
  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 ((unsigned)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 <= (unsigned long)(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 void *
 240 calloc(size_t num, size_t size)
 241 {
 242         void *ret;
 243
 244         if (size != 0 && (num * size) / size != num) {
 245                 /* size_t overflow. */
 246                 return (NULL);
 247         }
 248
 249         if ((ret = malloc(num * size)) != NULL)
 250                 memset(ret, 0, num * size);
 251
 252         return (ret);
 253 }
 254
 255 /*
 256  * Allocate more memory to the indicated bucket.
 257  */
 258 static void
 259 morecore(bucket)
 260         int bucket;
 261 {
 262         register union overhead *op;
 263         register int sz;                /* size of desired block */
 264         int amt;                        /* amount to allocate */
 265         int nblks;                      /* how many blocks we get */
 266
 267         /*
 268          * sbrk_size <= 0 only for big, FLUFFY, requests (about
 269          * 2^30 bytes on a VAX, I think) or for a negative arg.
 270          */
 271         sz = 1 << (bucket + 3);
 272 #ifdef MALLOC_DEBUG
 273         ASSERT(sz > 0);
 274 #else
 275         if (sz <= 0)
 276                 return;
 277 #endif
 278         if (sz < pagesz) {
 279                 amt = pagesz;
 280                 nblks = amt / sz;
 281         } else {
 282                 amt = sz + pagesz;
 283                 nblks = 1;
 284         }
 285         if (amt > pagepool_end - pagepool_start)
 286                 if (morepages(amt/pagesz + NPOOLPAGES) == 0)
 287                         return;
 288         op = (union overhead *)pagepool_start;
 289         pagepool_start += amt;
 290
 291         /*
 292          * Add new memory allocated to that on
 293          * free list for this hash bucket.
 294          */
 295         nextf[bucket] = op;
 296         while (--nblks > 0) {
 297                 op->ov_next = (union overhead *)((caddr_t)op + sz);
 298                 op = (union overhead *)((caddr_t)op + sz);
 299         }
 300 }
 301
 302 void
 303 free(cp)
 304         void *cp;
 305 {
 306         register int size;
 307         register union overhead *op;
 308
 309         if (cp == NULL)
 310                 return;
 311         op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
 312 #ifdef MALLOC_DEBUG
 313         ASSERT(op->ov_magic == MAGIC);          /* make sure it was in use */
 314 #else
 315         if (op->ov_magic != MAGIC)
 316                 return;                         /* sanity */
 317 #endif
 318 #ifdef RCHECK
 319         ASSERT(op->ov_rmagic == RMAGIC);
 320         ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC);
 321 #endif
 322         size = op->ov_index;
 323         ASSERT(size < NBUCKETS);
 324         op->ov_next = nextf[size];      /* also clobbers ov_magic */
 325         nextf[size] = op;
 326 #ifdef MSTATS
 327         nmalloc[size]--;
 328 #endif
 329 }
 330
 331 /*
 332  * When a program attempts "storage compaction" as mentioned in the
 333  * old malloc man page, it realloc's an already freed block.  Usually
 334  * this is the last block it freed; occasionally it might be farther
 335  * back.  We have to search all the free lists for the block in order
 336  * to determine its bucket: 1st we make one pass thru the lists
 337  * checking only the first block in each; if that fails we search
 338  * ``realloc_srchlen'' blocks in each list for a match (the variable
 339  * is extern so the caller can modify it).  If that fails we just copy
 340  * however many bytes was given to realloc() and hope it's not huge.
 341  */
 342 int realloc_srchlen = 4;        /* 4 should be plenty, -1 =>'s whole list */
 343
 344 void *
 345 realloc(cp, nbytes)
 346         void *cp;
 347         size_t nbytes;
 348 {
 349         register u_int onb;
 350         register int i;
 351         union overhead *op;
 352         char *res;
 353         int was_alloced = 0;
 354
 355         if (cp == NULL)
 356                 return (malloc(nbytes));
 357         op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
 358         if (op->ov_magic == MAGIC) {
 359                 was_alloced++;
 360                 i = op->ov_index;
 361         } else {
 362                 /*
 363                  * Already free, doing "compaction".
 364                  *
 365                  * Search for the old block of memory on the
 366                  * free list.  First, check the most common
 367                  * case (last element free'd), then (this failing)
 368                  * the last ``realloc_srchlen'' items free'd.
 369                  * If all lookups fail, then assume the size of
 370                  * the memory block being realloc'd is the
 371                  * largest possible (so that all "nbytes" of new
 372                  * memory are copied into).  Note that this could cause
 373                  * a memory fault if the old area was tiny, and the moon
 374                  * is gibbous.  However, that is very unlikely.
 375                  */
 376                 if ((i = findbucket(op, 1)) < 0 &&
 377                     (i = findbucket(op, realloc_srchlen)) < 0)
 378                         i = NBUCKETS;
 379         }
 380         onb = 1 << (i + 3);
 381         if (onb < (u_int)pagesz)
 382                 onb -= sizeof (*op) + RSLOP;
 383         else
 384                 onb += pagesz - sizeof (*op) - RSLOP;
 385         /* avoid the copy if same size block */
 386         if (was_alloced) {
 387                 if (i) {
 388                         i = 1 << (i + 2);
 389                         if (i < pagesz)
 390                                 i -= sizeof (*op) + RSLOP;
 391                         else
 392                                 i += pagesz - sizeof (*op) - RSLOP;
 393                 }
 394                 if (nbytes <= onb && nbytes > (size_t)i) {
 395 #ifdef RCHECK
 396                         op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
 397                         *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
 398 #endif
 399                         return(cp);
 400                 } else
 401                         free(cp);
 402         }
 403         if ((res = malloc(nbytes)) == NULL)
 404                 return (NULL);
 405         if (cp != res)          /* common optimization if "compacting" */
 406                 bcopy(cp, res, (nbytes < onb) ? nbytes : onb);
 407         return (res);
 408 }
 409
 410 /*
 411  * Search ``srchlen'' elements of each free list for a block whose
 412  * header starts at ``freep''.  If srchlen is -1 search the whole list.
 413  * Return bucket number, or -1 if not found.
 414  */
 415 static int
 416 findbucket(freep, srchlen)
 417         union overhead *freep;
 418         int srchlen;
 419 {
 420         register union overhead *p;
 421         register int i, j;
 422
 423         for (i = 0; i < NBUCKETS; i++) {
 424                 j = 0;
 425                 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
 426                         if (p == freep)
 427                                 return (i);
 428                         j++;
 429                 }
 430         }
 431         return (-1);
 432 }
 433
 434 #ifdef MSTATS
 435 /*
 436  * mstats - print out statistics about malloc
 437  *
 438  * Prints two lines of numbers, one showing the length of the free list
 439  * for each size category, the second showing the number of mallocs -
 440  * frees for each size category.
 441  */
 442 mstats(s)
 443         char *s;
 444 {
 445         register int i, j;
 446         register union overhead *p;
 447         int totfree = 0,
 448         totused = 0;
 449
 450         fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s);
 451         for (i = 0; i < NBUCKETS; i++) {
 452                 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
 453                         ;
 454                 fprintf(stderr, " %d", j);
 455                 totfree += j * (1 << (i + 3));
 456         }
 457         fprintf(stderr, "\nused:\t");
 458         for (i = 0; i < NBUCKETS; i++) {
 459                 fprintf(stderr, " %d", nmalloc[i]);
 460                 totused += nmalloc[i] * (1 << (i + 3));
 461         }
 462         fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n",
 463             totused, totfree);
 464 }
 465 #endif
 466
 467
 468 static int
 469 morepages(n)
 470 int     n;
 471 {
 472         int     fd = -1;
 473         int     offset;
 474
 475 #ifdef NEED_DEV_ZERO
 476         fd = open(_PATH_DEVZERO, O_RDWR, 0);
 477         if (fd == -1)
 478                 perror(_PATH_DEVZERO);
 479 #endif
 480
 481         if (pagepool_end - pagepool_start > pagesz) {
 482                 caddr_t addr = (caddr_t)
 483                         (((long)pagepool_start + pagesz - 1) & ~(pagesz - 1));
 484                 if (munmap(addr, pagepool_end - addr) != 0)
 485                         warn("morepages: munmap %p", addr);
 486         }
 487
 488         offset = (long)pagepool_start - ((long)pagepool_start & ~(pagesz - 1));
 489
 490         if ((pagepool_start = mmap(0, n * pagesz,
 491                         PROT_READ|PROT_WRITE,
 492                         MAP_ANON|MAP_COPY, fd, 0)) == (caddr_t)-1) {
 493                 xprintf("Cannot map anonymous memory");
 494                 return 0;
 495         }
 496         pagepool_end = pagepool_start + n * pagesz;
 497         pagepool_start += offset;
 498
 499 #ifdef NEED_DEV_ZERO
 500         close(fd);
 501 #endif
 502         return n;
 503 }
 504
 505 /*
 506  * Non-mallocing printf, for use by malloc itself.
 507  */
 508 static void
 509 xprintf(const char *fmt, ...)
 510 {
 511     char buf[256];
 512     va_list ap;
 513
 514     va_start(ap, fmt);
 515     vsprintf(buf, fmt, ap);
 516     (void)write(STDOUT_FILENO, buf, strlen(buf));
 517     va_end(ap);
 518 }