bfd/cache.c

   1 /* BFD library -- caching of file descriptors.
   2
   3    Copyright 1990, 1991, 1992, 1993, 1994, 1996, 2000, 2001, 2002,
   4    2003, 2004, 2005 Free Software Foundation, Inc.
   5
   6    Hacked by Steve Chamberlain of Cygnus Support (steve@cygnus.com).
   7
   8 This file is part of BFD, the Binary File Descriptor library.
   9
  10 This program is free software; you can redistribute it and/or modify
  11 it under the terms of the GNU General Public License as published by
  12 the Free Software Foundation; either version 2 of the License, or
  13 (at your option) any later version.
  14
  15 This program is distributed in the hope that it will be useful,
  16 but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 GNU General Public License for more details.
  19
  20 You should have received a copy of the GNU General Public License
  21 along with this program; if not, write to the Free Software
  22 Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA.  */
  23
  24 /*
  25 SECTION
  26         File caching
  27
  28         The file caching mechanism is embedded within BFD and allows
  29         the application to open as many BFDs as it wants without
  30         regard to the underlying operating system's file descriptor
  31         limit (often as low as 20 open files).  The module in
  32         <<cache.c>> maintains a least recently used list of
  33         <<BFD_CACHE_MAX_OPEN>> files, and exports the name
  34         <<bfd_cache_lookup>>, which runs around and makes sure that
  35         the required BFD is open. If not, then it chooses a file to
  36         close, closes it and opens the one wanted, returning its file
  37         handle.
  38
  39 SUBSECTION
  40         Caching functions
  41 */
  42
  43 #include "bfd.h"
  44 #include "sysdep.h"
  45 #include "libbfd.h"
  46 #include "libiberty.h"
  47
  48 /* The maximum number of files which the cache will keep open at
  49    one time.  */
  50
  51 #define BFD_CACHE_MAX_OPEN 10
  52
  53 /* The number of BFD files we have open.  */
  54
  55 static int open_files;
  56
  57 /* Zero, or a pointer to the topmost BFD on the chain.  This is
  58    used by the <<bfd_cache_lookup>> macro in @file{libbfd.h} to
  59    determine when it can avoid a function call.  */
  60
  61 static bfd *bfd_last_cache = NULL;
  62
  63 /* Insert a BFD into the cache.  */
  64
  65 static void
  66 insert (bfd *abfd)
  67 {
  68   if (bfd_last_cache == NULL)
  69     {
  70       abfd->lru_next = abfd;
  71       abfd->lru_prev = abfd;
  72     }
  73   else
  74     {
  75       abfd->lru_next = bfd_last_cache;
  76       abfd->lru_prev = bfd_last_cache->lru_prev;
  77       abfd->lru_prev->lru_next = abfd;
  78       abfd->lru_next->lru_prev = abfd;
  79     }
  80   bfd_last_cache = abfd;
  81 }
  82
  83 /* Remove a BFD from the cache.  */
  84
  85 static void
  86 snip (bfd *abfd)
  87 {
  88   abfd->lru_prev->lru_next = abfd->lru_next;
  89   abfd->lru_next->lru_prev = abfd->lru_prev;
  90   if (abfd == bfd_last_cache)
  91     {
  92       bfd_last_cache = abfd->lru_next;
  93       if (abfd == bfd_last_cache)
  94         bfd_last_cache = NULL;
  95     }
  96 }
  97
  98 /* Close a BFD and remove it from the cache.  */
  99
 100 static bfd_boolean
 101 bfd_cache_delete (bfd *abfd)
 102 {
 103   bfd_boolean ret;
 104
 105   if (fclose ((FILE *) abfd->iostream) == 0)
 106     ret = TRUE;
 107   else
 108     {
 109       ret = FALSE;
 110       bfd_set_error (bfd_error_system_call);
 111     }
 112
 113   snip (abfd);
 114
 115   abfd->iostream = NULL;
 116   --open_files;
 117
 118   return ret;
 119 }
 120
 121 /* We need to open a new file, and the cache is full.  Find the least
 122    recently used cacheable BFD and close it.  */
 123
 124 static bfd_boolean
 125 close_one (void)
 126 {
 127   register bfd *kill;
 128
 129   if (bfd_last_cache == NULL)
 130     kill = NULL;
 131   else
 132     {
 133       for (kill = bfd_last_cache->lru_prev;
 134            ! kill->cacheable;
 135            kill = kill->lru_prev)
 136         {
 137           if (kill == bfd_last_cache)
 138             {
 139               kill = NULL;
 140               break;
 141             }
 142         }
 143     }
 144
 145   if (kill == NULL)
 146     {
 147       /* There are no open cacheable BFD's.  */
 148       return TRUE;
 149     }
 150
 151   kill->where = real_ftell ((FILE *) kill->iostream);
 152
 153   return bfd_cache_delete (kill);
 154 }
 155
 156 /* Check to see if the required BFD is the same as the last one
 157    looked up. If so, then it can use the stream in the BFD with
 158    impunity, since it can't have changed since the last lookup;
 159    otherwise, it has to perform the complicated lookup function.  */
 160
 161 #define bfd_cache_lookup(x) \
 162   ((x) == bfd_last_cache                        \
 163    ? (FILE *) (bfd_last_cache->iostream)        \
 164    : bfd_cache_lookup_worker (x))
 165
 166 /* Called when the macro <<bfd_cache_lookup>> fails to find a
 167    quick answer.  Find a file descriptor for @var{abfd}.  If
 168    necessary, it open it.  If there are already more than
 169    <<BFD_CACHE_MAX_OPEN>> files open, it tries to close one first, to
 170    avoid running out of file descriptors.  It will return NULL
 171    if it is unable to (re)open the @var{abfd}.  */
 172
 173 static FILE *
 174 bfd_cache_lookup_worker (bfd *abfd)
 175 {
 176   bfd *orig_bfd = abfd;
 177   if ((abfd->flags & BFD_IN_MEMORY) != 0)
 178     abort ();
 179
 180   if (abfd->my_archive)
 181     abfd = abfd->my_archive;
 182
 183   if (abfd->iostream != NULL)
 184     {
 185       /* Move the file to the start of the cache.  */
 186       if (abfd != bfd_last_cache)
 187         {
 188           snip (abfd);
 189           insert (abfd);
 190         }
 191       return (FILE *) abfd->iostream;
 192     }
 193
 194   if (bfd_open_file (abfd) == NULL)
 195     ;
 196   else if (real_fseek ((FILE *) abfd->iostream, abfd->where, SEEK_SET) != 0)
 197     bfd_set_error (bfd_error_system_call);
 198   else
 199     return (FILE *) abfd->iostream;
 200
 201   (*_bfd_error_handler) (_("reopening %B: %s\n"),
 202                          orig_bfd, bfd_errmsg (bfd_get_error ()));
 203   return NULL;
 204 }
 205
 206 static file_ptr
 207 cache_btell (struct bfd *abfd)
 208 {
 209   FILE *f = bfd_cache_lookup (abfd);
 210   if (f == NULL)
 211     return -1;
 212   return real_ftell (f);
 213 }
 214
 215 static int
 216 cache_bseek (struct bfd *abfd, file_ptr offset, int whence)
 217 {
 218   FILE *f = bfd_cache_lookup (abfd);
 219   if (f == NULL)
 220     return -1;
 221   return real_fseek (f, offset, whence);
 222 }
 223
 224 /* Note that archive entries don't have streams; they share their parent's.
 225    This allows someone to play with the iostream behind BFD's back.
 226
 227    Also, note that the origin pointer points to the beginning of a file's
 228    contents (0 for non-archive elements).  For archive entries this is the
 229    first octet in the file, NOT the beginning of the archive header.  */
 230
 231 static file_ptr
 232 cache_bread (struct bfd *abfd, void *buf, file_ptr nbytes)
 233 {
 234   FILE *f;
 235   file_ptr nread;
 236   /* FIXME - this looks like an optimization, but it's really to cover
 237      up for a feature of some OSs (not solaris - sigh) that
 238      ld/pe-dll.c takes advantage of (apparently) when it creates BFDs
 239      internally and tries to link against them.  BFD seems to be smart
 240      enough to realize there are no symbol records in the "file" that
 241      doesn't exist but attempts to read them anyway.  On Solaris,
 242      attempting to read zero bytes from a NULL file results in a core
 243      dump, but on other platforms it just returns zero bytes read.
 244      This makes it to something reasonable. - DJ */
 245   if (nbytes == 0)
 246     return 0;
 247
 248   f = bfd_cache_lookup (abfd);
 249   if (f == NULL)
 250     return 0;
 251
 252 #if defined (__VAX) && defined (VMS)
 253   /* Apparently fread on Vax VMS does not keep the record length
 254      information.  */
 255   nread = read (fileno (f), buf, nbytes);
 256   /* Set bfd_error if we did not read as much data as we expected.  If
 257      the read failed due to an error set the bfd_error_system_call,
 258      else set bfd_error_file_truncated.  */
 259   if (nread == (file_ptr)-1)
 260     {
 261       bfd_set_error (bfd_error_system_call);
 262       return -1;
 263     }
 264 #else
 265   nread = fread (buf, 1, nbytes, f);
 266   /* Set bfd_error if we did not read as much data as we expected.  If
 267      the read failed due to an error set the bfd_error_system_call,
 268      else set bfd_error_file_truncated.  */
 269   if (nread < nbytes && ferror (f))
 270     {
 271       bfd_set_error (bfd_error_system_call);
 272       return -1;
 273     }
 274 #endif
 275   return nread;
 276 }
 277
 278 static file_ptr
 279 cache_bwrite (struct bfd *abfd, const void *where, file_ptr nbytes)
 280 {
 281   file_ptr nwrite;
 282   FILE *f = bfd_cache_lookup (abfd);
 283   if (f == NULL)
 284     return 0;
 285   nwrite = fwrite (where, 1, nbytes, f);
 286   if (nwrite < nbytes && ferror (f))
 287     {
 288       bfd_set_error (bfd_error_system_call);
 289       return -1;
 290     }
 291   return nwrite;
 292 }
 293
 294 static int
 295 cache_bclose (struct bfd *abfd)
 296 {
 297   return bfd_cache_close (abfd);
 298 }
 299
 300 static int
 301 cache_bflush (struct bfd *abfd)
 302 {
 303   int sts;
 304   FILE *f = bfd_cache_lookup (abfd);
 305   if (f == NULL)
 306     return -1;
 307   sts = fflush (f);
 308   if (sts < 0)
 309     bfd_set_error (bfd_error_system_call);
 310   return sts;
 311 }
 312
 313 static int
 314 cache_bstat (struct bfd *abfd, struct stat *sb)
 315 {
 316   int sts;
 317   FILE *f = bfd_cache_lookup (abfd);
 318   if (f == NULL)
 319     return -1;
 320   sts = fstat (fileno (f), sb);
 321   if (sts < 0)
 322     bfd_set_error (bfd_error_system_call);
 323   return sts;
 324 }
 325
 326 static const struct bfd_iovec cache_iovec = {
 327   &cache_bread, &cache_bwrite, &cache_btell, &cache_bseek,
 328   &cache_bclose, &cache_bflush, &cache_bstat
 329 };
 330
 331 /*
 332 INTERNAL_FUNCTION
 333         bfd_cache_init
 334
 335 SYNOPSIS
 336         bfd_boolean bfd_cache_init (bfd *abfd);
 337
 338 DESCRIPTION
 339         Add a newly opened BFD to the cache.
 340 */
 341
 342 bfd_boolean
 343 bfd_cache_init (bfd *abfd)
 344 {
 345   BFD_ASSERT (abfd->iostream != NULL);
 346   if (open_files >= BFD_CACHE_MAX_OPEN)
 347     {
 348       if (! close_one ())
 349         return FALSE;
 350     }
 351   abfd->iovec = &cache_iovec;
 352   insert (abfd);
 353   ++open_files;
 354   return TRUE;
 355 }
 356
 357 /*
 358 INTERNAL_FUNCTION
 359         bfd_cache_close
 360
 361 SYNOPSIS
 362         bfd_boolean bfd_cache_close (bfd *abfd);
 363
 364 DESCRIPTION
 365         Remove the BFD @var{abfd} from the cache. If the attached file is open,
 366         then close it too.
 367
 368 RETURNS
 369         <<FALSE>> is returned if closing the file fails, <<TRUE>> is
 370         returned if all is well.
 371 */
 372
 373 bfd_boolean
 374 bfd_cache_close (bfd *abfd)
 375 {
 376   if (abfd->iovec != &cache_iovec)
 377     return TRUE;
 378
 379   if (abfd->iostream == NULL)
 380     /* Previously closed.  */
 381     return TRUE;
 382
 383   return bfd_cache_delete (abfd);
 384 }
 385
 386 /*
 387 FUNCTION
 388         bfd_cache_close_all
 389
 390 SYNOPSIS
 391         bfd_boolean bfd_cache_close_all (void);
 392
 393 DESCRIPTION
 394         Remove all BFDs from the cache. If the attached file is open,
 395         then close it too.
 396
 397 RETURNS
 398         <<FALSE>> is returned if closing one of the file fails, <<TRUE>> is
 399         returned if all is well.
 400 */
 401
 402 bfd_boolean
 403 bfd_cache_close_all ()
 404 {
 405   bfd_boolean ret = TRUE;
 406
 407   while (bfd_last_cache != NULL)
 408     ret &= bfd_cache_close (bfd_last_cache);
 409
 410   return ret;
 411 }
 412
 413 /*
 414 INTERNAL_FUNCTION
 415         bfd_open_file
 416
 417 SYNOPSIS
 418         FILE* bfd_open_file (bfd *abfd);
 419
 420 DESCRIPTION
 421         Call the OS to open a file for @var{abfd}.  Return the <<FILE *>>
 422         (possibly <<NULL>>) that results from this operation.  Set up the
 423         BFD so that future accesses know the file is open. If the <<FILE *>>
 424         returned is <<NULL>>, then it won't have been put in the
 425         cache, so it won't have to be removed from it.
 426 */
 427
 428 FILE *
 429 bfd_open_file (bfd *abfd)
 430 {
 431   abfd->cacheable = TRUE;       /* Allow it to be closed later.  */
 432
 433   if (open_files >= BFD_CACHE_MAX_OPEN)
 434     {
 435       if (! close_one ())
 436         return NULL;
 437     }
 438
 439   switch (abfd->direction)
 440     {
 441     case read_direction:
 442     case no_direction:
 443       abfd->iostream = (PTR) fopen (abfd->filename, FOPEN_RB);
 444       break;
 445     case both_direction:
 446     case write_direction:
 447       if (abfd->opened_once)
 448         {
 449           abfd->iostream = (PTR) fopen (abfd->filename, FOPEN_RUB);
 450           if (abfd->iostream == NULL)
 451             abfd->iostream = (PTR) fopen (abfd->filename, FOPEN_WUB);
 452         }
 453       else
 454         {
 455           /* Create the file.
 456
 457              Some operating systems won't let us overwrite a running
 458              binary.  For them, we want to unlink the file first.
 459
 460              However, gcc 2.95 will create temporary files using
 461              O_EXCL and tight permissions to prevent other users from
 462              substituting other .o files during the compilation.  gcc
 463              will then tell the assembler to use the newly created
 464              file as an output file.  If we unlink the file here, we
 465              open a brief window when another user could still
 466              substitute a file.
 467
 468              So we unlink the output file if and only if it has
 469              non-zero size.  */
 470 #ifndef __MSDOS__
 471           /* Don't do this for MSDOS: it doesn't care about overwriting
 472              a running binary, but if this file is already open by
 473              another BFD, we will be in deep trouble if we delete an
 474              open file.  In fact, objdump does just that if invoked with
 475              the --info option.  */
 476           struct stat s;
 477
 478           if (stat (abfd->filename, &s) == 0 && s.st_size != 0)
 479             unlink_if_ordinary (abfd->filename);
 480 #endif
 481           abfd->iostream = (PTR) fopen (abfd->filename, FOPEN_WUB);
 482           abfd->opened_once = TRUE;
 483         }
 484       break;
 485     }
 486
 487   if (abfd->iostream == NULL)
 488     bfd_set_error (bfd_error_system_call);
 489   else
 490     {
 491       if (! bfd_cache_init (abfd))
 492         return NULL;
 493     }
 494
 495   return (FILE *) abfd->iostream;
 496 }