1 /* BFD library -- caching of file descriptors. 2 3 Copyright 1990, 1991, 1992, 1993, 1994, 1996, 2000, 2001, 2002, 4 2003, 2004, 2005, 2007, 2008, 2009 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 #ifdef HAVE_MMAP 50 #include <sys/mman.h> 51 #endif 52 53 /* In some cases we can optimize cache operation when reopening files. 54 For instance, a flush is entirely unnecessary if the file is already 55 closed, so a flush would use CACHE_NO_OPEN. Similarly, a seek using 56 SEEK_SET or SEEK_END need not first seek to the current position. 57 For stat we ignore seek errors, just in case the file has changed 58 while we weren't looking. If it has, then it's possible that the 59 file is shorter and we don't want a seek error to prevent us doing 60 the stat. */ 61 enum cache_flag { 62 CACHE_NORMAL = 0, 63 CACHE_NO_OPEN = 1, 64 CACHE_NO_SEEK = 2, 65 CACHE_NO_SEEK_ERROR = 4 66 }; 67 68 /* The maximum number of files which the cache will keep open at 69 one time. */ 70 71 #define BFD_CACHE_MAX_OPEN 10 72 73 /* The number of BFD files we have open. */ 74 75 static int open_files; 76 77 /* Zero, or a pointer to the topmost BFD on the chain. This is 78 used by the <<bfd_cache_lookup>> macro in @file{libbfd.h} to 79 determine when it can avoid a function call. */ 80 81 static bfd *bfd_last_cache = NULL; 82 83 /* Insert a BFD into the cache. */ 84 85 static void 86 insert (bfd *abfd) 87 { 88 if (bfd_last_cache == NULL) 89 { 90 abfd->lru_next = abfd; 91 abfd->lru_prev = abfd; 92 } 93 else 94 { 95 abfd->lru_next = bfd_last_cache; 96 abfd->lru_prev = bfd_last_cache->lru_prev; 97 abfd->lru_prev->lru_next = abfd; 98 abfd->lru_next->lru_prev = abfd; 99 } 100 bfd_last_cache = abfd; 101 } 102 103 /* Remove a BFD from the cache. */ 104 105 static void 106 snip (bfd *abfd) 107 { 108 abfd->lru_prev->lru_next = abfd->lru_next; 109 abfd->lru_next->lru_prev = abfd->lru_prev; 110 if (abfd == bfd_last_cache) 111 { 112 bfd_last_cache = abfd->lru_next; 113 if (abfd == bfd_last_cache) 114 bfd_last_cache = NULL; 115 } 116 } 117 118 /* Close a BFD and remove it from the cache. */ 119 120 static bfd_boolean 121 bfd_cache_delete (bfd *abfd) 122 { 123 bfd_boolean ret; 124 125 if (fclose ((FILE *) abfd->iostream) == 0) 126 ret = TRUE; 127 else 128 { 129 ret = FALSE; 130 bfd_set_error (bfd_error_system_call); 131 } 132 133 snip (abfd); 134 135 abfd->iostream = NULL; 136 --open_files; 137 138 return ret; 139 } 140 141 /* We need to open a new file, and the cache is full. Find the least 142 recently used cacheable BFD and close it. */ 143 144 static bfd_boolean 145 close_one (void) 146 { 147 register bfd *kill; 148 149 if (bfd_last_cache == NULL) 150 kill = NULL; 151 else 152 { 153 for (kill = bfd_last_cache->lru_prev; 154 ! kill->cacheable; 155 kill = kill->lru_prev) 156 { 157 if (kill == bfd_last_cache) 158 { 159 kill = NULL; 160 break; 161 } 162 } 163 } 164 165 if (kill == NULL) 166 { 167 /* There are no open cacheable BFD's. */ 168 return TRUE; 169 } 170 171 kill->where = real_ftell ((FILE *) kill->iostream); 172 173 return bfd_cache_delete (kill); 174 } 175 176 /* Check to see if the required BFD is the same as the last one 177 looked up. If so, then it can use the stream in the BFD with 178 impunity, since it can't have changed since the last lookup; 179 otherwise, it has to perform the complicated lookup function. */ 180 181 #define bfd_cache_lookup(x, flag) \ 182 ((x) == bfd_last_cache \ 183 ? (FILE *) (bfd_last_cache->iostream) \ 184 : bfd_cache_lookup_worker (x, flag)) 185 186 /* Called when the macro <<bfd_cache_lookup>> fails to find a 187 quick answer. Find a file descriptor for @var{abfd}. If 188 necessary, it open it. If there are already more than 189 <<BFD_CACHE_MAX_OPEN>> files open, it tries to close one first, to 190 avoid running out of file descriptors. It will return NULL 191 if it is unable to (re)open the @var{abfd}. */ 192 193 static FILE * 194 bfd_cache_lookup_worker (bfd *abfd, enum cache_flag flag) 195 { 196 bfd *orig_bfd = abfd; 197 if ((abfd->flags & BFD_IN_MEMORY) != 0) 198 abort (); 199 200 if (abfd->my_archive) 201 abfd = abfd->my_archive; 202 203 if (abfd->iostream != NULL) 204 { 205 /* Move the file to the start of the cache. */ 206 if (abfd != bfd_last_cache) 207 { 208 snip (abfd); 209 insert (abfd); 210 } 211 return (FILE *) abfd->iostream; 212 } 213 214 if (flag & CACHE_NO_OPEN) 215 return NULL; 216 217 if (bfd_open_file (abfd) == NULL) 218 ; 219 else if (!(flag & CACHE_NO_SEEK) 220 && real_fseek ((FILE *) abfd->iostream, abfd->where, SEEK_SET) != 0 221 && !(flag & CACHE_NO_SEEK_ERROR)) 222 bfd_set_error (bfd_error_system_call); 223 else 224 return (FILE *) abfd->iostream; 225 226 (*_bfd_error_handler) (_("reopening %B: %s\n"), 227 orig_bfd, bfd_errmsg (bfd_get_error ())); 228 return NULL; 229 } 230 231 static file_ptr 232 cache_btell (struct bfd *abfd) 233 { 234 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN); 235 if (f == NULL) 236 return abfd->where; 237 return real_ftell (f); 238 } 239 240 static int 241 cache_bseek (struct bfd *abfd, file_ptr offset, int whence) 242 { 243 FILE *f = bfd_cache_lookup (abfd, whence != SEEK_CUR ? CACHE_NO_SEEK : CACHE_NORMAL); 244 if (f == NULL) 245 return -1; 246 return real_fseek (f, offset, whence); 247 } 248 249 /* Note that archive entries don't have streams; they share their parent's. 250 This allows someone to play with the iostream behind BFD's back. 251 252 Also, note that the origin pointer points to the beginning of a file's 253 contents (0 for non-archive elements). For archive entries this is the 254 first octet in the file, NOT the beginning of the archive header. */ 255 256 static file_ptr 257 cache_bread_1 (struct bfd *abfd, void *buf, file_ptr nbytes) 258 { 259 FILE *f; 260 file_ptr nread; 261 /* FIXME - this looks like an optimization, but it's really to cover 262 up for a feature of some OSs (not solaris - sigh) that 263 ld/pe-dll.c takes advantage of (apparently) when it creates BFDs 264 internally and tries to link against them. BFD seems to be smart 265 enough to realize there are no symbol records in the "file" that 266 doesn't exist but attempts to read them anyway. On Solaris, 267 attempting to read zero bytes from a NULL file results in a core 268 dump, but on other platforms it just returns zero bytes read. 269 This makes it to something reasonable. - DJ */ 270 if (nbytes == 0) 271 return 0; 272 273 f = bfd_cache_lookup (abfd, CACHE_NORMAL); 274 if (f == NULL) 275 return 0; 276 277 #if defined (__VAX) && defined (VMS) 278 /* Apparently fread on Vax VMS does not keep the record length 279 information. */ 280 nread = read (fileno (f), buf, nbytes); 281 /* Set bfd_error if we did not read as much data as we expected. If 282 the read failed due to an error set the bfd_error_system_call, 283 else set bfd_error_file_truncated. */ 284 if (nread == (file_ptr)-1) 285 { 286 bfd_set_error (bfd_error_system_call); 287 return -1; 288 } 289 #else 290 nread = fread (buf, 1, nbytes, f); 291 /* Set bfd_error if we did not read as much data as we expected. If 292 the read failed due to an error set the bfd_error_system_call, 293 else set bfd_error_file_truncated. */ 294 if (nread < nbytes && ferror (f)) 295 { 296 bfd_set_error (bfd_error_system_call); 297 return -1; 298 } 299 #endif 300 if (nread < nbytes) 301 /* This may or may not be an error, but in case the calling code 302 bails out because of it, set the right error code. */ 303 bfd_set_error (bfd_error_file_truncated); 304 return nread; 305 } 306 307 static file_ptr 308 cache_bread (struct bfd *abfd, void *buf, file_ptr nbytes) 309 { 310 file_ptr nread = 0; 311 312 /* Some filesystems are unable to handle reads that are too large 313 (for instance, NetApp shares with oplocks turned off). To avoid 314 hitting this limitation, we read the buffer in chunks of 8MB max. */ 315 while (nread < nbytes) 316 { 317 const file_ptr max_chunk_size = 0x800000; 318 file_ptr chunk_size = nbytes - nread; 319 file_ptr chunk_nread; 320 321 if (chunk_size > max_chunk_size) 322 chunk_size = max_chunk_size; 323 324 chunk_nread = cache_bread_1 (abfd, (char *) buf + nread, chunk_size); 325 326 /* Update the nread count. 327 328 We just have to be careful of the case when cache_bread_1 returns 329 a negative count: If this is our first read, then set nread to 330 that negative count in order to return that negative value to the 331 caller. Otherwise, don't add it to our total count, or we would 332 end up returning a smaller number of bytes read than we actually 333 did. */ 334 if (nread == 0 || chunk_nread > 0) 335 nread += chunk_nread; 336 337 if (chunk_nread < chunk_size) 338 break; 339 } 340 341 return nread; 342 } 343 344 static file_ptr 345 cache_bwrite (struct bfd *abfd, const void *where, file_ptr nbytes) 346 { 347 file_ptr nwrite; 348 FILE *f = bfd_cache_lookup (abfd, CACHE_NORMAL); 349 350 if (f == NULL) 351 return 0; 352 nwrite = fwrite (where, 1, nbytes, f); 353 if (nwrite < nbytes && ferror (f)) 354 { 355 bfd_set_error (bfd_error_system_call); 356 return -1; 357 } 358 return nwrite; 359 } 360 361 static int 362 cache_bclose (struct bfd *abfd) 363 { 364 return bfd_cache_close (abfd); 365 } 366 367 static int 368 cache_bflush (struct bfd *abfd) 369 { 370 int sts; 371 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN); 372 373 if (f == NULL) 374 return 0; 375 sts = fflush (f); 376 if (sts < 0) 377 bfd_set_error (bfd_error_system_call); 378 return sts; 379 } 380 381 static int 382 cache_bstat (struct bfd *abfd, struct stat *sb) 383 { 384 int sts; 385 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR); 386 387 if (f == NULL) 388 return -1; 389 sts = fstat (fileno (f), sb); 390 if (sts < 0) 391 bfd_set_error (bfd_error_system_call); 392 return sts; 393 } 394 395 static void * 396 cache_bmmap (struct bfd *abfd ATTRIBUTE_UNUSED, 397 void *addr ATTRIBUTE_UNUSED, 398 bfd_size_type len ATTRIBUTE_UNUSED, 399 int prot ATTRIBUTE_UNUSED, 400 int flags ATTRIBUTE_UNUSED, 401 file_ptr offset ATTRIBUTE_UNUSED) 402 { 403 void *ret = (void *) -1; 404 405 if ((abfd->flags & BFD_IN_MEMORY) != 0) 406 abort (); 407 #ifdef HAVE_MMAP 408 else 409 { 410 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR); 411 if (f == NULL) 412 return ret; 413 414 ret = mmap (addr, len, prot, flags, fileno (f), offset); 415 if (ret == (void *) -1) 416 bfd_set_error (bfd_error_system_call); 417 } 418 #endif 419 420 return ret; 421 } 422 423 static const struct bfd_iovec cache_iovec = 424 { 425 &cache_bread, &cache_bwrite, &cache_btell, &cache_bseek, 426 &cache_bclose, &cache_bflush, &cache_bstat, &cache_bmmap 427 }; 428 429 /* 430 INTERNAL_FUNCTION 431 bfd_cache_init 432 433 SYNOPSIS 434 bfd_boolean bfd_cache_init (bfd *abfd); 435 436 DESCRIPTION 437 Add a newly opened BFD to the cache. 438 */ 439 440 bfd_boolean 441 bfd_cache_init (bfd *abfd) 442 { 443 BFD_ASSERT (abfd->iostream != NULL); 444 if (open_files >= BFD_CACHE_MAX_OPEN) 445 { 446 if (! close_one ()) 447 return FALSE; 448 } 449 abfd->iovec = &cache_iovec; 450 insert (abfd); 451 ++open_files; 452 return TRUE; 453 } 454 455 /* 456 INTERNAL_FUNCTION 457 bfd_cache_close 458 459 SYNOPSIS 460 bfd_boolean bfd_cache_close (bfd *abfd); 461 462 DESCRIPTION 463 Remove the BFD @var{abfd} from the cache. If the attached file is open, 464 then close it too. 465 466 RETURNS 467 <<FALSE>> is returned if closing the file fails, <<TRUE>> is 468 returned if all is well. 469 */ 470 471 bfd_boolean 472 bfd_cache_close (bfd *abfd) 473 { 474 if (abfd->iovec != &cache_iovec) 475 return TRUE; 476 477 if (abfd->iostream == NULL) 478 /* Previously closed. */ 479 return TRUE; 480 481 return bfd_cache_delete (abfd); 482 } 483 484 /* 485 FUNCTION 486 bfd_cache_close_all 487 488 SYNOPSIS 489 bfd_boolean bfd_cache_close_all (void); 490 491 DESCRIPTION 492 Remove all BFDs from the cache. If the attached file is open, 493 then close it too. 494 495 RETURNS 496 <<FALSE>> is returned if closing one of the file fails, <<TRUE>> is 497 returned if all is well. 498 */ 499 500 bfd_boolean 501 bfd_cache_close_all () 502 { 503 bfd_boolean ret = TRUE; 504 505 while (bfd_last_cache != NULL) 506 ret &= bfd_cache_close (bfd_last_cache); 507 508 return ret; 509 } 510 511 /* 512 INTERNAL_FUNCTION 513 bfd_open_file 514 515 SYNOPSIS 516 FILE* bfd_open_file (bfd *abfd); 517 518 DESCRIPTION 519 Call the OS to open a file for @var{abfd}. Return the <<FILE *>> 520 (possibly <<NULL>>) that results from this operation. Set up the 521 BFD so that future accesses know the file is open. If the <<FILE *>> 522 returned is <<NULL>>, then it won't have been put in the 523 cache, so it won't have to be removed from it. 524 */ 525 526 FILE * 527 bfd_open_file (bfd *abfd) 528 { 529 abfd->cacheable = TRUE; /* Allow it to be closed later. */ 530 531 if (open_files >= BFD_CACHE_MAX_OPEN) 532 { 533 if (! close_one ()) 534 return NULL; 535 } 536 537 switch (abfd->direction) 538 { 539 case read_direction: 540 case no_direction: 541 abfd->iostream = (PTR) real_fopen (abfd->filename, FOPEN_RB); 542 break; 543 case both_direction: 544 case write_direction: 545 if (abfd->opened_once) 546 { 547 abfd->iostream = (PTR) real_fopen (abfd->filename, FOPEN_RUB); 548 if (abfd->iostream == NULL) 549 abfd->iostream = (PTR) real_fopen (abfd->filename, FOPEN_WUB); 550 } 551 else 552 { 553 /* Create the file. 554 555 Some operating systems won't let us overwrite a running 556 binary. For them, we want to unlink the file first. 557 558 However, gcc 2.95 will create temporary files using 559 O_EXCL and tight permissions to prevent other users from 560 substituting other .o files during the compilation. gcc 561 will then tell the assembler to use the newly created 562 file as an output file. If we unlink the file here, we 563 open a brief window when another user could still 564 substitute a file. 565 566 So we unlink the output file if and only if it has 567 non-zero size. */ 568 #ifndef __MSDOS__ 569 /* Don't do this for MSDOS: it doesn't care about overwriting 570 a running binary, but if this file is already open by 571 another BFD, we will be in deep trouble if we delete an 572 open file. In fact, objdump does just that if invoked with 573 the --info option. */ 574 struct stat s; 575 576 if (stat (abfd->filename, &s) == 0 && s.st_size != 0) 577 unlink_if_ordinary (abfd->filename); 578 #endif 579 abfd->iostream = (PTR) real_fopen (abfd->filename, FOPEN_WUB); 580 abfd->opened_once = TRUE; 581 } 582 break; 583 } 584 585 if (abfd->iostream == NULL) 586 bfd_set_error (bfd_error_system_call); 587 else 588 { 589 if (! bfd_cache_init (abfd)) 590 return NULL; 591 } 592 593 return (FILE *) abfd->iostream; 594 } 595