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, 2007 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 3 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,
  23    MA 02110-1301, USA.  */
  24
  25 /*
  26 SECTION
  27         File caching
  28
  29         The file caching mechanism is embedded within BFD and allows
  30         the application to open as many BFDs as it wants without
  31         regard to the underlying operating system's file descriptor
  32         limit (often as low as 20 open files).  The module in
  33         <<cache.c>> maintains a least recently used list of
  34         <<BFD_CACHE_MAX_OPEN>> files, and exports the name
  35         <<bfd_cache_lookup>>, which runs around and makes sure that
  36         the required BFD is open. If not, then it chooses a file to
  37         close, closes it and opens the one wanted, returning its file
  38         handle.
  39
  40 SUBSECTION
  41         Caching functions
  42 */
  43
  44 #include "sysdep.h"
  45 #include "bfd.h"
  46 #include "libbfd.h"
  47 #include "libiberty.h"
  48
  49 /* In some cases we can optimize cache operation when reopening files.
  50    For instance, a flush is entirely unnecessary if the file is already
  51    closed, so a flush would use CACHE_NO_OPEN.  Similarly, a seek using
  52    SEEK_SET or SEEK_END need not first seek to the current position.
  53    For stat we ignore seek errors, just in case the file has changed
  54    while we weren't looking.  If it has, then it's possible that the
  55    file is shorter and we don't want a seek error to prevent us doing
  56    the stat.  */
  57 enum cache_flag {
  58   CACHE_NORMAL = 0,
  59   CACHE_NO_OPEN = 1,
  60   CACHE_NO_SEEK = 2,
  61   CACHE_NO_SEEK_ERROR = 4
  62 };
  63
  64 /* The maximum number of files which the cache will keep open at
  65    one time.  */
  66
  67 #define BFD_CACHE_MAX_OPEN 10
  68
  69 /* The number of BFD files we have open.  */
  70
  71 static int open_files;
  72
  73 /* Zero, or a pointer to the topmost BFD on the chain.  This is
  74    used by the <<bfd_cache_lookup>> macro in @file{libbfd.h} to
  75    determine when it can avoid a function call.  */
  76
  77 static bfd *bfd_last_cache = NULL;
  78
  79 /* Insert a BFD into the cache.  */
  80
  81 static void
  82 insert (bfd *abfd)
  83 {
  84   if (bfd_last_cache == NULL)
  85     {
  86       abfd->lru_next = abfd;
  87       abfd->lru_prev = abfd;
  88     }
  89   else
  90     {
  91       abfd->lru_next = bfd_last_cache;
  92       abfd->lru_prev = bfd_last_cache->lru_prev;
  93       abfd->lru_prev->lru_next = abfd;
  94       abfd->lru_next->lru_prev = abfd;
  95     }
  96   bfd_last_cache = abfd;
  97 }
  98
  99 /* Remove a BFD from the cache.  */
 100
 101 static void
 102 snip (bfd *abfd)
 103 {
 104   abfd->lru_prev->lru_next = abfd->lru_next;
 105   abfd->lru_next->lru_prev = abfd->lru_prev;
 106   if (abfd == bfd_last_cache)
 107     {
 108       bfd_last_cache = abfd->lru_next;
 109       if (abfd == bfd_last_cache)
 110         bfd_last_cache = NULL;
 111     }
 112 }
 113
 114 /* Close a BFD and remove it from the cache.  */
 115
 116 static bfd_boolean
 117 bfd_cache_delete (bfd *abfd)
 118 {
 119   bfd_boolean ret;
 120
 121   if (fclose ((FILE *) abfd->iostream) == 0)
 122     ret = TRUE;
 123   else
 124     {
 125       ret = FALSE;
 126       bfd_set_error (bfd_error_system_call);
 127     }
 128
 129   snip (abfd);
 130
 131   abfd->iostream = NULL;
 132   --open_files;
 133
 134   return ret;
 135 }
 136
 137 /* We need to open a new file, and the cache is full.  Find the least
 138    recently used cacheable BFD and close it.  */
 139
 140 static bfd_boolean
 141 close_one (void)
 142 {
 143   register bfd *kill;
 144
 145   if (bfd_last_cache == NULL)
 146     kill = NULL;
 147   else
 148     {
 149       for (kill = bfd_last_cache->lru_prev;
 150            ! kill->cacheable;
 151            kill = kill->lru_prev)
 152         {
 153           if (kill == bfd_last_cache)
 154             {
 155               kill = NULL;
 156               break;
 157             }
 158         }
 159     }
 160
 161   if (kill == NULL)
 162     {
 163       /* There are no open cacheable BFD's.  */
 164       return TRUE;
 165     }
 166
 167   kill->where = real_ftell ((FILE *) kill->iostream);
 168
 169   return bfd_cache_delete (kill);
 170 }
 171
 172 /* Check to see if the required BFD is the same as the last one
 173    looked up. If so, then it can use the stream in the BFD with
 174    impunity, since it can't have changed since the last lookup;
 175    otherwise, it has to perform the complicated lookup function.  */
 176
 177 #define bfd_cache_lookup(x, flag) \
 178   ((x) == bfd_last_cache                        \
 179    ? (FILE *) (bfd_last_cache->iostream)        \
 180    : bfd_cache_lookup_worker (x, flag))
 181
 182 /* Called when the macro <<bfd_cache_lookup>> fails to find a
 183    quick answer.  Find a file descriptor for @var{abfd}.  If
 184    necessary, it open it.  If there are already more than
 185    <<BFD_CACHE_MAX_OPEN>> files open, it tries to close one first, to
 186    avoid running out of file descriptors.  It will return NULL
 187    if it is unable to (re)open the @var{abfd}.  */
 188
 189 static FILE *
 190 bfd_cache_lookup_worker (bfd *abfd, enum cache_flag flag)
 191 {
 192   bfd *orig_bfd = abfd;
 193   if ((abfd->flags & BFD_IN_MEMORY) != 0)
 194     abort ();
 195
 196   if (abfd->my_archive)
 197     abfd = abfd->my_archive;
 198
 199   if (abfd->iostream != NULL)
 200     {
 201       /* Move the file to the start of the cache.  */
 202       if (abfd != bfd_last_cache)
 203         {
 204           snip (abfd);
 205           insert (abfd);
 206         }
 207       return (FILE *) abfd->iostream;
 208     }
 209
 210   if (flag & CACHE_NO_OPEN)
 211     return NULL;
 212
 213   if (bfd_open_file (abfd) == NULL)
 214     ;
 215   else if (!(flag & CACHE_NO_SEEK)
 216            && real_fseek ((FILE *) abfd->iostream, abfd->where, SEEK_SET) != 0
 217            && !(flag & CACHE_NO_SEEK_ERROR))
 218     bfd_set_error (bfd_error_system_call);
 219   else
 220     return (FILE *) abfd->iostream;
 221
 222   (*_bfd_error_handler) (_("reopening %B: %s\n"),
 223                          orig_bfd, bfd_errmsg (bfd_get_error ()));
 224   return NULL;
 225 }
 226
 227 static file_ptr
 228 cache_btell (struct bfd *abfd)
 229 {
 230   FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN);
 231   if (f == NULL)
 232     return abfd->where;
 233   return real_ftell (f);
 234 }
 235
 236 static int
 237 cache_bseek (struct bfd *abfd, file_ptr offset, int whence)
 238 {
 239   FILE *f = bfd_cache_lookup (abfd, whence != SEEK_CUR ? CACHE_NO_SEEK : 0);
 240   if (f == NULL)
 241     return -1;
 242   return real_fseek (f, offset, whence);
 243 }
 244
 245 /* Note that archive entries don't have streams; they share their parent's.
 246    This allows someone to play with the iostream behind BFD's back.
 247
 248    Also, note that the origin pointer points to the beginning of a file's
 249    contents (0 for non-archive elements).  For archive entries this is the
 250    first octet in the file, NOT the beginning of the archive header.  */
 251
 252 static file_ptr
 253 cache_bread_1 (struct bfd *abfd, void *buf, file_ptr nbytes)
 254 {
 255   FILE *f;
 256   file_ptr nread;
 257   /* FIXME - this looks like an optimization, but it's really to cover
 258      up for a feature of some OSs (not solaris - sigh) that
 259      ld/pe-dll.c takes advantage of (apparently) when it creates BFDs
 260      internally and tries to link against them.  BFD seems to be smart
 261      enough to realize there are no symbol records in the "file" that
 262      doesn't exist but attempts to read them anyway.  On Solaris,
 263      attempting to read zero bytes from a NULL file results in a core
 264      dump, but on other platforms it just returns zero bytes read.
 265      This makes it to something reasonable. - DJ */
 266   if (nbytes == 0)
 267     return 0;
 268
 269   f = bfd_cache_lookup (abfd, 0);
 270   if (f == NULL)
 271     return 0;
 272
 273 #if defined (__VAX) && defined (VMS)
 274   /* Apparently fread on Vax VMS does not keep the record length
 275      information.  */
 276   nread = read (fileno (f), buf, nbytes);
 277   /* Set bfd_error if we did not read as much data as we expected.  If
 278      the read failed due to an error set the bfd_error_system_call,
 279      else set bfd_error_file_truncated.  */
 280   if (nread == (file_ptr)-1)
 281     {
 282       bfd_set_error (bfd_error_system_call);
 283       return -1;
 284     }
 285 #else
 286   nread = fread (buf, 1, nbytes, f);
 287   /* Set bfd_error if we did not read as much data as we expected.  If
 288      the read failed due to an error set the bfd_error_system_call,
 289      else set bfd_error_file_truncated.  */
 290   if (nread < nbytes && ferror (f))
 291     {
 292       bfd_set_error (bfd_error_system_call);
 293       return -1;
 294     }
 295 #endif
 296   if (nread < nbytes)
 297     /* This may or may not be an error, but in case the calling code
 298        bails out because of it, set the right error code.  */
 299     bfd_set_error (bfd_error_file_truncated);
 300   return nread;
 301 }
 302
 303 static file_ptr
 304 cache_bread (struct bfd *abfd, void *buf, file_ptr nbytes)
 305 {
 306   file_ptr nread = 0;
 307
 308   /* Some filesystems are unable to handle reads that are too large
 309      (for instance, NetApp shares with oplocks turned off).  To avoid
 310      hitting this limitation, we read the buffer in chunks of 8MB max.  */
 311   while (nread < nbytes)
 312     {
 313       const file_ptr max_chunk_size = 0x800000;
 314       file_ptr chunk_size = nbytes - nread;
 315       file_ptr chunk_nread;
 316
 317       if (chunk_size > max_chunk_size)
 318         chunk_size = max_chunk_size;
 319
 320       chunk_nread = cache_bread_1 (abfd, (char *) buf + nread, chunk_size);
 321
 322       /* Update the nread count.
 323
 324          We just have to be careful of the case when cache_bread_1 returns
 325          a negative count:  If this is our first read, then set nread to
 326          that negative count in order to return that negative value to the
 327          caller.  Otherwise, don't add it to our total count, or we would
 328          end up returning a smaller number of bytes read than we actually
 329          did.  */
 330       if (nread == 0 || chunk_nread > 0)
 331         nread += chunk_nread;
 332
 333       if (chunk_nread < chunk_size)
 334         break;
 335     }
 336
 337   return nread;
 338 }
 339
 340 static file_ptr
 341 cache_bwrite (struct bfd *abfd, const void *where, file_ptr nbytes)
 342 {
 343   file_ptr nwrite;
 344   FILE *f = bfd_cache_lookup (abfd, 0);
 345
 346   if (f == NULL)
 347     return 0;
 348   nwrite = fwrite (where, 1, nbytes, f);
 349   if (nwrite < nbytes && ferror (f))
 350     {
 351       bfd_set_error (bfd_error_system_call);
 352       return -1;
 353     }
 354   return nwrite;
 355 }
 356
 357 static int
 358 cache_bclose (struct bfd *abfd)
 359 {
 360   return bfd_cache_close (abfd);
 361 }
 362
 363 static int
 364 cache_bflush (struct bfd *abfd)
 365 {
 366   int sts;
 367   FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN);
 368
 369   if (f == NULL)
 370     return 0;
 371   sts = fflush (f);
 372   if (sts < 0)
 373     bfd_set_error (bfd_error_system_call);
 374   return sts;
 375 }
 376
 377 static int
 378 cache_bstat (struct bfd *abfd, struct stat *sb)
 379 {
 380   int sts;
 381   FILE *f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR);
 382
 383   if (f == NULL)
 384     return -1;
 385   sts = fstat (fileno (f), sb);
 386   if (sts < 0)
 387     bfd_set_error (bfd_error_system_call);
 388   return sts;
 389 }
 390
 391 static const struct bfd_iovec cache_iovec =
 392 {
 393   &cache_bread, &cache_bwrite, &cache_btell, &cache_bseek,
 394   &cache_bclose, &cache_bflush, &cache_bstat
 395 };
 396
 397 /*
 398 INTERNAL_FUNCTION
 399         bfd_cache_init
 400
 401 SYNOPSIS
 402         bfd_boolean bfd_cache_init (bfd *abfd);
 403
 404 DESCRIPTION
 405         Add a newly opened BFD to the cache.
 406 */
 407
 408 bfd_boolean
 409 bfd_cache_init (bfd *abfd)
 410 {
 411   BFD_ASSERT (abfd->iostream != NULL);
 412   if (open_files >= BFD_CACHE_MAX_OPEN)
 413     {
 414       if (! close_one ())
 415         return FALSE;
 416     }
 417   abfd->iovec = &cache_iovec;
 418   insert (abfd);
 419   ++open_files;
 420   return TRUE;
 421 }
 422
 423 /*
 424 INTERNAL_FUNCTION
 425         bfd_cache_close
 426
 427 SYNOPSIS
 428         bfd_boolean bfd_cache_close (bfd *abfd);
 429
 430 DESCRIPTION
 431         Remove the BFD @var{abfd} from the cache. If the attached file is open,
 432         then close it too.
 433
 434 RETURNS
 435         <<FALSE>> is returned if closing the file fails, <<TRUE>> is
 436         returned if all is well.
 437 */
 438
 439 bfd_boolean
 440 bfd_cache_close (bfd *abfd)
 441 {
 442   if (abfd->iovec != &cache_iovec)
 443     return TRUE;
 444
 445   if (abfd->iostream == NULL)
 446     /* Previously closed.  */
 447     return TRUE;
 448
 449   return bfd_cache_delete (abfd);
 450 }
 451
 452 /*
 453 FUNCTION
 454         bfd_cache_close_all
 455
 456 SYNOPSIS
 457         bfd_boolean bfd_cache_close_all (void);
 458
 459 DESCRIPTION
 460         Remove all BFDs from the cache. If the attached file is open,
 461         then close it too.
 462
 463 RETURNS
 464         <<FALSE>> is returned if closing one of the file fails, <<TRUE>> is
 465         returned if all is well.
 466 */
 467
 468 bfd_boolean
 469 bfd_cache_close_all ()
 470 {
 471   bfd_boolean ret = TRUE;
 472
 473   while (bfd_last_cache != NULL)
 474     ret &= bfd_cache_close (bfd_last_cache);
 475
 476   return ret;
 477 }
 478
 479 /*
 480 INTERNAL_FUNCTION
 481         bfd_open_file
 482
 483 SYNOPSIS
 484         FILE* bfd_open_file (bfd *abfd);
 485
 486 DESCRIPTION
 487         Call the OS to open a file for @var{abfd}.  Return the <<FILE *>>
 488         (possibly <<NULL>>) that results from this operation.  Set up the
 489         BFD so that future accesses know the file is open. If the <<FILE *>>
 490         returned is <<NULL>>, then it won't have been put in the
 491         cache, so it won't have to be removed from it.
 492 */
 493
 494 FILE *
 495 bfd_open_file (bfd *abfd)
 496 {
 497   abfd->cacheable = TRUE;       /* Allow it to be closed later.  */
 498
 499   if (open_files >= BFD_CACHE_MAX_OPEN)
 500     {
 501       if (! close_one ())
 502         return NULL;
 503     }
 504
 505   switch (abfd->direction)
 506     {
 507     case read_direction:
 508     case no_direction:
 509       abfd->iostream = (PTR) real_fopen (abfd->filename, FOPEN_RB);
 510       break;
 511     case both_direction:
 512     case write_direction:
 513       if (abfd->opened_once)
 514         {
 515           abfd->iostream = (PTR) real_fopen (abfd->filename, FOPEN_RUB);
 516           if (abfd->iostream == NULL)
 517             abfd->iostream = (PTR) real_fopen (abfd->filename, FOPEN_WUB);
 518         }
 519       else
 520         {
 521           /* Create the file.
 522
 523              Some operating systems won't let us overwrite a running
 524              binary.  For them, we want to unlink the file first.
 525
 526              However, gcc 2.95 will create temporary files using
 527              O_EXCL and tight permissions to prevent other users from
 528              substituting other .o files during the compilation.  gcc
 529              will then tell the assembler to use the newly created
 530              file as an output file.  If we unlink the file here, we
 531              open a brief window when another user could still
 532              substitute a file.
 533
 534              So we unlink the output file if and only if it has
 535              non-zero size.  */
 536 #ifndef __MSDOS__
 537           /* Don't do this for MSDOS: it doesn't care about overwriting
 538              a running binary, but if this file is already open by
 539              another BFD, we will be in deep trouble if we delete an
 540              open file.  In fact, objdump does just that if invoked with
 541              the --info option.  */
 542           struct stat s;
 543
 544           if (stat (abfd->filename, &s) == 0 && s.st_size != 0)
 545             unlink_if_ordinary (abfd->filename);
 546 #endif
 547           abfd->iostream = (PTR) real_fopen (abfd->filename, FOPEN_WUB);
 548           abfd->opened_once = TRUE;
 549         }
 550       break;
 551     }
 552
 553   if (abfd->iostream == NULL)
 554     bfd_set_error (bfd_error_system_call);
 555   else
 556     {
 557       if (! bfd_cache_init (abfd))
 558         return NULL;
 559     }
 560
 561   return (FILE *) abfd->iostream;
 562 }