1 /* BFD library -- caching of file descriptors. 2 3 Copyright (C) 1990-2014 Free Software Foundation, Inc. 4 5 Hacked by Steve Chamberlain of Cygnus Support (steve (at) cygnus.com). 6 7 This file is part of BFD, the Binary File Descriptor library. 8 9 This program is free software; you can redistribute it and/or modify 10 it under the terms of the GNU General Public License as published by 11 the Free Software Foundation; either version 3 of the License, or 12 (at your option) any later version. 13 14 This program is distributed in the hope that it will be useful, 15 but WITHOUT ANY WARRANTY; without even the implied warranty of 16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 17 GNU General Public License for more details. 18 19 You should have received a copy of the GNU General Public License 20 along with this program; if not, write to the Free Software 21 Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, 22 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 "sysdep.h" 44 #include "bfd.h" 45 #include "libbfd.h" 46 #include "libiberty.h" 47 #include "bfd_stdint.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. When needed call bfd_cache_max_open to initialize. */ 70 71 static int max_open_files = 0; 72 73 /* Set max_open_files, if not already set, to 12.5% of the allowed open 74 file descriptors, but at least 10, and return the value. */ 75 static int 76 bfd_cache_max_open (void) 77 { 78 if (max_open_files == 0) 79 { 80 int max; 81 #ifdef HAVE_GETRLIMIT 82 struct rlimit rlim; 83 if (getrlimit (RLIMIT_NOFILE, &rlim) == 0 84 && rlim.rlim_cur != (rlim_t) RLIM_INFINITY) 85 max = rlim.rlim_cur / 8; 86 else 87 #endif /* HAVE_GETRLIMIT */ 88 #ifdef _SC_OPEN_MAX 89 max = sysconf (_SC_OPEN_MAX) / 8; 90 #else 91 max = 10; 92 #endif /* _SC_OPEN_MAX */ 93 max_open_files = max < 10 ? 10 : max; 94 } 95 96 return max_open_files; 97 } 98 99 /* The number of BFD files we have open. */ 100 101 static int open_files; 102 103 /* Zero, or a pointer to the topmost BFD on the chain. This is 104 used by the <<bfd_cache_lookup>> macro in @file{libbfd.h} to 105 determine when it can avoid a function call. */ 106 107 static bfd *bfd_last_cache = NULL; 108 109 /* Insert a BFD into the cache. */ 110 111 static void 112 insert (bfd *abfd) 113 { 114 if (bfd_last_cache == NULL) 115 { 116 abfd->lru_next = abfd; 117 abfd->lru_prev = abfd; 118 } 119 else 120 { 121 abfd->lru_next = bfd_last_cache; 122 abfd->lru_prev = bfd_last_cache->lru_prev; 123 abfd->lru_prev->lru_next = abfd; 124 abfd->lru_next->lru_prev = abfd; 125 } 126 bfd_last_cache = abfd; 127 } 128 129 /* Remove a BFD from the cache. */ 130 131 static void 132 snip (bfd *abfd) 133 { 134 abfd->lru_prev->lru_next = abfd->lru_next; 135 abfd->lru_next->lru_prev = abfd->lru_prev; 136 if (abfd == bfd_last_cache) 137 { 138 bfd_last_cache = abfd->lru_next; 139 if (abfd == bfd_last_cache) 140 bfd_last_cache = NULL; 141 } 142 } 143 144 /* Close a BFD and remove it from the cache. */ 145 146 static bfd_boolean 147 bfd_cache_delete (bfd *abfd) 148 { 149 bfd_boolean ret; 150 151 if (fclose ((FILE *) abfd->iostream) == 0) 152 ret = TRUE; 153 else 154 { 155 ret = FALSE; 156 bfd_set_error (bfd_error_system_call); 157 } 158 159 snip (abfd); 160 161 abfd->iostream = NULL; 162 --open_files; 163 164 return ret; 165 } 166 167 /* We need to open a new file, and the cache is full. Find the least 168 recently used cacheable BFD and close it. */ 169 170 static bfd_boolean 171 close_one (void) 172 { 173 register bfd *to_kill; 174 175 if (bfd_last_cache == NULL) 176 to_kill = NULL; 177 else 178 { 179 for (to_kill = bfd_last_cache->lru_prev; 180 ! to_kill->cacheable; 181 to_kill = to_kill->lru_prev) 182 { 183 if (to_kill == bfd_last_cache) 184 { 185 to_kill = NULL; 186 break; 187 } 188 } 189 } 190 191 if (to_kill == NULL) 192 { 193 /* There are no open cacheable BFD's. */ 194 return TRUE; 195 } 196 197 to_kill->where = real_ftell ((FILE *) to_kill->iostream); 198 199 return bfd_cache_delete (to_kill); 200 } 201 202 /* Check to see if the required BFD is the same as the last one 203 looked up. If so, then it can use the stream in the BFD with 204 impunity, since it can't have changed since the last lookup; 205 otherwise, it has to perform the complicated lookup function. */ 206 207 #define bfd_cache_lookup(x, flag) \ 208 ((x) == bfd_last_cache \ 209 ? (FILE *) (bfd_last_cache->iostream) \ 210 : bfd_cache_lookup_worker (x, flag)) 211 212 /* Called when the macro <<bfd_cache_lookup>> fails to find a 213 quick answer. Find a file descriptor for @var{abfd}. If 214 necessary, it open it. If there are already more than 215 <<bfd_cache_max_open>> files open, it tries to close one first, to 216 avoid running out of file descriptors. It will return NULL 217 if it is unable to (re)open the @var{abfd}. */ 218 219 static FILE * 220 bfd_cache_lookup_worker (bfd *abfd, enum cache_flag flag) 221 { 222 bfd *orig_bfd = abfd; 223 if ((abfd->flags & BFD_IN_MEMORY) != 0) 224 abort (); 225 226 while (abfd->my_archive) 227 abfd = abfd->my_archive; 228 229 if (abfd->iostream != NULL) 230 { 231 /* Move the file to the start of the cache. */ 232 if (abfd != bfd_last_cache) 233 { 234 snip (abfd); 235 insert (abfd); 236 } 237 return (FILE *) abfd->iostream; 238 } 239 240 if (flag & CACHE_NO_OPEN) 241 return NULL; 242 243 if (bfd_open_file (abfd) == NULL) 244 ; 245 else if (!(flag & CACHE_NO_SEEK) 246 && real_fseek ((FILE *) abfd->iostream, abfd->where, SEEK_SET) != 0 247 && !(flag & CACHE_NO_SEEK_ERROR)) 248 bfd_set_error (bfd_error_system_call); 249 else 250 return (FILE *) abfd->iostream; 251 252 (*_bfd_error_handler) (_("reopening %B: %s\n"), 253 orig_bfd, bfd_errmsg (bfd_get_error ())); 254 return NULL; 255 } 256 257 static file_ptr 258 cache_btell (struct bfd *abfd) 259 { 260 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN); 261 if (f == NULL) 262 return abfd->where; 263 return real_ftell (f); 264 } 265 266 static int 267 cache_bseek (struct bfd *abfd, file_ptr offset, int whence) 268 { 269 FILE *f = bfd_cache_lookup (abfd, whence != SEEK_CUR ? CACHE_NO_SEEK : CACHE_NORMAL); 270 if (f == NULL) 271 return -1; 272 return real_fseek (f, offset, whence); 273 } 274 275 /* Note that archive entries don't have streams; they share their parent's. 276 This allows someone to play with the iostream behind BFD's back. 277 278 Also, note that the origin pointer points to the beginning of a file's 279 contents (0 for non-archive elements). For archive entries this is the 280 first octet in the file, NOT the beginning of the archive header. */ 281 282 static file_ptr 283 cache_bread_1 (struct bfd *abfd, void *buf, file_ptr nbytes) 284 { 285 FILE *f; 286 file_ptr nread; 287 /* FIXME - this looks like an optimization, but it's really to cover 288 up for a feature of some OSs (not solaris - sigh) that 289 ld/pe-dll.c takes advantage of (apparently) when it creates BFDs 290 internally and tries to link against them. BFD seems to be smart 291 enough to realize there are no symbol records in the "file" that 292 doesn't exist but attempts to read them anyway. On Solaris, 293 attempting to read zero bytes from a NULL file results in a core 294 dump, but on other platforms it just returns zero bytes read. 295 This makes it to something reasonable. - DJ */ 296 if (nbytes == 0) 297 return 0; 298 299 f = bfd_cache_lookup (abfd, CACHE_NORMAL); 300 if (f == NULL) 301 return 0; 302 303 #if defined (__VAX) && defined (VMS) 304 /* Apparently fread on Vax VMS does not keep the record length 305 information. */ 306 nread = read (fileno (f), buf, nbytes); 307 /* Set bfd_error if we did not read as much data as we expected. If 308 the read failed due to an error set the bfd_error_system_call, 309 else set bfd_error_file_truncated. */ 310 if (nread == (file_ptr)-1) 311 { 312 bfd_set_error (bfd_error_system_call); 313 return nread; 314 } 315 #else 316 nread = fread (buf, 1, nbytes, f); 317 /* Set bfd_error if we did not read as much data as we expected. If 318 the read failed due to an error set the bfd_error_system_call, 319 else set bfd_error_file_truncated. */ 320 if (nread < nbytes && ferror (f)) 321 { 322 bfd_set_error (bfd_error_system_call); 323 return nread; 324 } 325 #endif 326 if (nread < nbytes) 327 /* This may or may not be an error, but in case the calling code 328 bails out because of it, set the right error code. */ 329 bfd_set_error (bfd_error_file_truncated); 330 return nread; 331 } 332 333 static file_ptr 334 cache_bread (struct bfd *abfd, void *buf, file_ptr nbytes) 335 { 336 file_ptr nread = 0; 337 338 /* Some filesystems are unable to handle reads that are too large 339 (for instance, NetApp shares with oplocks turned off). To avoid 340 hitting this limitation, we read the buffer in chunks of 8MB max. */ 341 while (nread < nbytes) 342 { 343 const file_ptr max_chunk_size = 0x800000; 344 file_ptr chunk_size = nbytes - nread; 345 file_ptr chunk_nread; 346 347 if (chunk_size > max_chunk_size) 348 chunk_size = max_chunk_size; 349 350 chunk_nread = cache_bread_1 (abfd, (char *) buf + nread, chunk_size); 351 352 /* Update the nread count. 353 354 We just have to be careful of the case when cache_bread_1 returns 355 a negative count: If this is our first read, then set nread to 356 that negative count in order to return that negative value to the 357 caller. Otherwise, don't add it to our total count, or we would 358 end up returning a smaller number of bytes read than we actually 359 did. */ 360 if (nread == 0 || chunk_nread > 0) 361 nread += chunk_nread; 362 363 if (chunk_nread < chunk_size) 364 break; 365 } 366 367 return nread; 368 } 369 370 static file_ptr 371 cache_bwrite (struct bfd *abfd, const void *where, file_ptr nbytes) 372 { 373 file_ptr nwrite; 374 FILE *f = bfd_cache_lookup (abfd, CACHE_NORMAL); 375 376 if (f == NULL) 377 return 0; 378 nwrite = fwrite (where, 1, nbytes, f); 379 if (nwrite < nbytes && ferror (f)) 380 { 381 bfd_set_error (bfd_error_system_call); 382 return -1; 383 } 384 return nwrite; 385 } 386 387 static int 388 cache_bclose (struct bfd *abfd) 389 { 390 return bfd_cache_close (abfd) - 1; 391 } 392 393 static int 394 cache_bflush (struct bfd *abfd) 395 { 396 int sts; 397 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN); 398 399 if (f == NULL) 400 return 0; 401 sts = fflush (f); 402 if (sts < 0) 403 bfd_set_error (bfd_error_system_call); 404 return sts; 405 } 406 407 static int 408 cache_bstat (struct bfd *abfd, struct stat *sb) 409 { 410 int sts; 411 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR); 412 413 if (f == NULL) 414 return -1; 415 sts = fstat (fileno (f), sb); 416 if (sts < 0) 417 bfd_set_error (bfd_error_system_call); 418 return sts; 419 } 420 421 static void * 422 cache_bmmap (struct bfd *abfd ATTRIBUTE_UNUSED, 423 void *addr ATTRIBUTE_UNUSED, 424 bfd_size_type len ATTRIBUTE_UNUSED, 425 int prot ATTRIBUTE_UNUSED, 426 int flags ATTRIBUTE_UNUSED, 427 file_ptr offset ATTRIBUTE_UNUSED, 428 void **map_addr ATTRIBUTE_UNUSED, 429 bfd_size_type *map_len ATTRIBUTE_UNUSED) 430 { 431 void *ret = (void *) -1; 432 433 if ((abfd->flags & BFD_IN_MEMORY) != 0) 434 abort (); 435 #ifdef HAVE_MMAP 436 else 437 { 438 static uintptr_t pagesize_m1; 439 FILE *f; 440 file_ptr pg_offset; 441 bfd_size_type pg_len; 442 443 f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR); 444 if (f == NULL) 445 return ret; 446 447 if (pagesize_m1 == 0) 448 pagesize_m1 = getpagesize () - 1; 449 450 /* Handle archive members. */ 451 if (abfd->my_archive != NULL) 452 offset += abfd->origin; 453 454 /* Align. */ 455 pg_offset = offset & ~pagesize_m1; 456 pg_len = (len + (offset - pg_offset) + pagesize_m1) & ~pagesize_m1; 457 458 ret = mmap (addr, pg_len, prot, flags, fileno (f), pg_offset); 459 if (ret == (void *) -1) 460 bfd_set_error (bfd_error_system_call); 461 else 462 { 463 *map_addr = ret; 464 *map_len = pg_len; 465 ret = (char *) ret + (offset & pagesize_m1); 466 } 467 } 468 #endif 469 470 return ret; 471 } 472 473 static const struct bfd_iovec cache_iovec = 474 { 475 &cache_bread, &cache_bwrite, &cache_btell, &cache_bseek, 476 &cache_bclose, &cache_bflush, &cache_bstat, &cache_bmmap 477 }; 478 479 /* 480 INTERNAL_FUNCTION 481 bfd_cache_init 482 483 SYNOPSIS 484 bfd_boolean bfd_cache_init (bfd *abfd); 485 486 DESCRIPTION 487 Add a newly opened BFD to the cache. 488 */ 489 490 bfd_boolean 491 bfd_cache_init (bfd *abfd) 492 { 493 BFD_ASSERT (abfd->iostream != NULL); 494 if (open_files >= bfd_cache_max_open ()) 495 { 496 if (! close_one ()) 497 return FALSE; 498 } 499 abfd->iovec = &cache_iovec; 500 insert (abfd); 501 ++open_files; 502 return TRUE; 503 } 504 505 /* 506 INTERNAL_FUNCTION 507 bfd_cache_close 508 509 SYNOPSIS 510 bfd_boolean bfd_cache_close (bfd *abfd); 511 512 DESCRIPTION 513 Remove the BFD @var{abfd} from the cache. If the attached file is open, 514 then close it too. 515 516 RETURNS 517 <<FALSE>> is returned if closing the file fails, <<TRUE>> is 518 returned if all is well. 519 */ 520 521 bfd_boolean 522 bfd_cache_close (bfd *abfd) 523 { 524 if (abfd->iovec != &cache_iovec) 525 return TRUE; 526 527 if (abfd->iostream == NULL) 528 /* Previously closed. */ 529 return TRUE; 530 531 return bfd_cache_delete (abfd); 532 } 533 534 /* 535 FUNCTION 536 bfd_cache_close_all 537 538 SYNOPSIS 539 bfd_boolean bfd_cache_close_all (void); 540 541 DESCRIPTION 542 Remove all BFDs from the cache. If the attached file is open, 543 then close it too. 544 545 RETURNS 546 <<FALSE>> is returned if closing one of the file fails, <<TRUE>> is 547 returned if all is well. 548 */ 549 550 bfd_boolean 551 bfd_cache_close_all () 552 { 553 bfd_boolean ret = TRUE; 554 555 while (bfd_last_cache != NULL) 556 ret &= bfd_cache_close (bfd_last_cache); 557 558 return ret; 559 } 560 561 /* 562 INTERNAL_FUNCTION 563 bfd_open_file 564 565 SYNOPSIS 566 FILE* bfd_open_file (bfd *abfd); 567 568 DESCRIPTION 569 Call the OS to open a file for @var{abfd}. Return the <<FILE *>> 570 (possibly <<NULL>>) that results from this operation. Set up the 571 BFD so that future accesses know the file is open. If the <<FILE *>> 572 returned is <<NULL>>, then it won't have been put in the 573 cache, so it won't have to be removed from it. 574 */ 575 576 FILE * 577 bfd_open_file (bfd *abfd) 578 { 579 abfd->cacheable = TRUE; /* Allow it to be closed later. */ 580 581 if (open_files >= bfd_cache_max_open ()) 582 { 583 if (! close_one ()) 584 return NULL; 585 } 586 587 switch (abfd->direction) 588 { 589 case read_direction: 590 case no_direction: 591 abfd->iostream = real_fopen (abfd->filename, FOPEN_RB); 592 break; 593 case both_direction: 594 case write_direction: 595 if (abfd->opened_once) 596 { 597 abfd->iostream = real_fopen (abfd->filename, FOPEN_RUB); 598 if (abfd->iostream == NULL) 599 abfd->iostream = real_fopen (abfd->filename, FOPEN_WUB); 600 } 601 else 602 { 603 /* Create the file. 604 605 Some operating systems won't let us overwrite a running 606 binary. For them, we want to unlink the file first. 607 608 However, gcc 2.95 will create temporary files using 609 O_EXCL and tight permissions to prevent other users from 610 substituting other .o files during the compilation. gcc 611 will then tell the assembler to use the newly created 612 file as an output file. If we unlink the file here, we 613 open a brief window when another user could still 614 substitute a file. 615 616 So we unlink the output file if and only if it has 617 non-zero size. */ 618 #ifndef __MSDOS__ 619 /* Don't do this for MSDOS: it doesn't care about overwriting 620 a running binary, but if this file is already open by 621 another BFD, we will be in deep trouble if we delete an 622 open file. In fact, objdump does just that if invoked with 623 the --info option. */ 624 struct stat s; 625 626 if (stat (abfd->filename, &s) == 0 && s.st_size != 0) 627 unlink_if_ordinary (abfd->filename); 628 #endif 629 abfd->iostream = real_fopen (abfd->filename, FOPEN_WUB); 630 abfd->opened_once = TRUE; 631 } 632 break; 633 } 634 635 if (abfd->iostream == NULL) 636 bfd_set_error (bfd_error_system_call); 637 else 638 { 639 if (! bfd_cache_init (abfd)) 640 return NULL; 641 } 642 643 return (FILE *) abfd->iostream; 644 } 645
