1 /* BFD library -- caching of file descriptors. 2 3 Copyright (C) 1990-2016 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 #if defined(__sun) && !defined(__sparcv9) && !defined(__x86_64__) 82 /* PR ld/19260: 32-bit Solaris has very inelegant handling of the 255 83 file descriptor limit. The problem is that setrlimit(2) can raise 84 RLIMIT_NOFILE to a value that is not supported by libc, resulting 85 in "Too many open files" errors. This can happen here even though 86 max_open_files is set to rlim.rlim_cur / 8. For example, if 87 a parent process has set rlim.rlim_cur to 65536, then max_open_files 88 will be computed as 8192. 89 90 This check essentially reverts to the behavior from binutils 2.23.1 91 for 32-bit Solaris only. (It is hoped that the 32-bit libc 92 limitation will be removed soon). 64-bit Solaris libc does not have 93 this limitation. */ 94 max = 16; 95 #else 96 #ifdef HAVE_GETRLIMIT 97 struct rlimit rlim; 98 99 if (getrlimit (RLIMIT_NOFILE, &rlim) == 0 100 && rlim.rlim_cur != (rlim_t) RLIM_INFINITY) 101 max = rlim.rlim_cur / 8; 102 else 103 #endif 104 #ifdef _SC_OPEN_MAX 105 max = sysconf (_SC_OPEN_MAX) / 8; 106 #else 107 max = 10; 108 #endif 109 #endif /* not 32-bit Solaris */ 110 111 max_open_files = max < 10 ? 10 : max; 112 } 113 114 return max_open_files; 115 } 116 117 /* The number of BFD files we have open. */ 118 119 static int open_files; 120 121 /* Zero, or a pointer to the topmost BFD on the chain. This is 122 used by the <<bfd_cache_lookup>> macro in @file{libbfd.h} to 123 determine when it can avoid a function call. */ 124 125 static bfd *bfd_last_cache = NULL; 126 127 /* Insert a BFD into the cache. */ 128 129 static void 130 insert (bfd *abfd) 131 { 132 if (bfd_last_cache == NULL) 133 { 134 abfd->lru_next = abfd; 135 abfd->lru_prev = abfd; 136 } 137 else 138 { 139 abfd->lru_next = bfd_last_cache; 140 abfd->lru_prev = bfd_last_cache->lru_prev; 141 abfd->lru_prev->lru_next = abfd; 142 abfd->lru_next->lru_prev = abfd; 143 } 144 bfd_last_cache = abfd; 145 } 146 147 /* Remove a BFD from the cache. */ 148 149 static void 150 snip (bfd *abfd) 151 { 152 abfd->lru_prev->lru_next = abfd->lru_next; 153 abfd->lru_next->lru_prev = abfd->lru_prev; 154 if (abfd == bfd_last_cache) 155 { 156 bfd_last_cache = abfd->lru_next; 157 if (abfd == bfd_last_cache) 158 bfd_last_cache = NULL; 159 } 160 } 161 162 /* Close a BFD and remove it from the cache. */ 163 164 static bfd_boolean 165 bfd_cache_delete (bfd *abfd) 166 { 167 bfd_boolean ret; 168 169 if (fclose ((FILE *) abfd->iostream) == 0) 170 ret = TRUE; 171 else 172 { 173 ret = FALSE; 174 bfd_set_error (bfd_error_system_call); 175 } 176 177 snip (abfd); 178 179 abfd->iostream = NULL; 180 --open_files; 181 182 return ret; 183 } 184 185 /* We need to open a new file, and the cache is full. Find the least 186 recently used cacheable BFD and close it. */ 187 188 static bfd_boolean 189 close_one (void) 190 { 191 register bfd *to_kill; 192 193 if (bfd_last_cache == NULL) 194 to_kill = NULL; 195 else 196 { 197 for (to_kill = bfd_last_cache->lru_prev; 198 ! to_kill->cacheable; 199 to_kill = to_kill->lru_prev) 200 { 201 if (to_kill == bfd_last_cache) 202 { 203 to_kill = NULL; 204 break; 205 } 206 } 207 } 208 209 if (to_kill == NULL) 210 { 211 /* There are no open cacheable BFD's. */ 212 return TRUE; 213 } 214 215 to_kill->where = real_ftell ((FILE *) to_kill->iostream); 216 217 return bfd_cache_delete (to_kill); 218 } 219 220 /* Check to see if the required BFD is the same as the last one 221 looked up. If so, then it can use the stream in the BFD with 222 impunity, since it can't have changed since the last lookup; 223 otherwise, it has to perform the complicated lookup function. */ 224 225 #define bfd_cache_lookup(x, flag) \ 226 ((x) == bfd_last_cache \ 227 ? (FILE *) (bfd_last_cache->iostream) \ 228 : bfd_cache_lookup_worker (x, flag)) 229 230 /* Called when the macro <<bfd_cache_lookup>> fails to find a 231 quick answer. Find a file descriptor for @var{abfd}. If 232 necessary, it open it. If there are already more than 233 <<bfd_cache_max_open>> files open, it tries to close one first, to 234 avoid running out of file descriptors. It will return NULL 235 if it is unable to (re)open the @var{abfd}. */ 236 237 static FILE * 238 bfd_cache_lookup_worker (bfd *abfd, enum cache_flag flag) 239 { 240 bfd *orig_bfd = abfd; 241 if ((abfd->flags & BFD_IN_MEMORY) != 0) 242 abort (); 243 244 while (abfd->my_archive != NULL 245 && !bfd_is_thin_archive (abfd->my_archive)) 246 abfd = abfd->my_archive; 247 248 if (abfd->iostream != NULL) 249 { 250 /* Move the file to the start of the cache. */ 251 if (abfd != bfd_last_cache) 252 { 253 snip (abfd); 254 insert (abfd); 255 } 256 return (FILE *) abfd->iostream; 257 } 258 259 if (flag & CACHE_NO_OPEN) 260 return NULL; 261 262 if (bfd_open_file (abfd) == NULL) 263 ; 264 else if (!(flag & CACHE_NO_SEEK) 265 && real_fseek ((FILE *) abfd->iostream, abfd->where, SEEK_SET) != 0 266 && !(flag & CACHE_NO_SEEK_ERROR)) 267 bfd_set_error (bfd_error_system_call); 268 else 269 return (FILE *) abfd->iostream; 270 271 (*_bfd_error_handler) (_("reopening %B: %s\n"), 272 orig_bfd, bfd_errmsg (bfd_get_error ())); 273 return NULL; 274 } 275 276 static file_ptr 277 cache_btell (struct bfd *abfd) 278 { 279 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN); 280 if (f == NULL) 281 return abfd->where; 282 return real_ftell (f); 283 } 284 285 static int 286 cache_bseek (struct bfd *abfd, file_ptr offset, int whence) 287 { 288 FILE *f = bfd_cache_lookup (abfd, whence != SEEK_CUR ? CACHE_NO_SEEK : CACHE_NORMAL); 289 if (f == NULL) 290 return -1; 291 return real_fseek (f, offset, whence); 292 } 293 294 /* Note that archive entries don't have streams; they share their parent's. 295 This allows someone to play with the iostream behind BFD's back. 296 297 Also, note that the origin pointer points to the beginning of a file's 298 contents (0 for non-archive elements). For archive entries this is the 299 first octet in the file, NOT the beginning of the archive header. */ 300 301 static file_ptr 302 cache_bread_1 (struct bfd *abfd, void *buf, file_ptr nbytes) 303 { 304 FILE *f; 305 file_ptr nread; 306 /* FIXME - this looks like an optimization, but it's really to cover 307 up for a feature of some OSs (not solaris - sigh) that 308 ld/pe-dll.c takes advantage of (apparently) when it creates BFDs 309 internally and tries to link against them. BFD seems to be smart 310 enough to realize there are no symbol records in the "file" that 311 doesn't exist but attempts to read them anyway. On Solaris, 312 attempting to read zero bytes from a NULL file results in a core 313 dump, but on other platforms it just returns zero bytes read. 314 This makes it to something reasonable. - DJ */ 315 if (nbytes == 0) 316 return 0; 317 318 f = bfd_cache_lookup (abfd, CACHE_NORMAL); 319 if (f == NULL) 320 return 0; 321 322 #if defined (__VAX) && defined (VMS) 323 /* Apparently fread on Vax VMS does not keep the record length 324 information. */ 325 nread = read (fileno (f), buf, nbytes); 326 /* Set bfd_error if we did not read as much data as we expected. If 327 the read failed due to an error set the bfd_error_system_call, 328 else set bfd_error_file_truncated. */ 329 if (nread == (file_ptr)-1) 330 { 331 bfd_set_error (bfd_error_system_call); 332 return nread; 333 } 334 #else 335 nread = fread (buf, 1, nbytes, f); 336 /* Set bfd_error if we did not read as much data as we expected. If 337 the read failed due to an error set the bfd_error_system_call, 338 else set bfd_error_file_truncated. */ 339 if (nread < nbytes && ferror (f)) 340 { 341 bfd_set_error (bfd_error_system_call); 342 return nread; 343 } 344 #endif 345 if (nread < nbytes) 346 /* This may or may not be an error, but in case the calling code 347 bails out because of it, set the right error code. */ 348 bfd_set_error (bfd_error_file_truncated); 349 return nread; 350 } 351 352 static file_ptr 353 cache_bread (struct bfd *abfd, void *buf, file_ptr nbytes) 354 { 355 file_ptr nread = 0; 356 357 /* Some filesystems are unable to handle reads that are too large 358 (for instance, NetApp shares with oplocks turned off). To avoid 359 hitting this limitation, we read the buffer in chunks of 8MB max. */ 360 while (nread < nbytes) 361 { 362 const file_ptr max_chunk_size = 0x800000; 363 file_ptr chunk_size = nbytes - nread; 364 file_ptr chunk_nread; 365 366 if (chunk_size > max_chunk_size) 367 chunk_size = max_chunk_size; 368 369 chunk_nread = cache_bread_1 (abfd, (char *) buf + nread, chunk_size); 370 371 /* Update the nread count. 372 373 We just have to be careful of the case when cache_bread_1 returns 374 a negative count: If this is our first read, then set nread to 375 that negative count in order to return that negative value to the 376 caller. Otherwise, don't add it to our total count, or we would 377 end up returning a smaller number of bytes read than we actually 378 did. */ 379 if (nread == 0 || chunk_nread > 0) 380 nread += chunk_nread; 381 382 if (chunk_nread < chunk_size) 383 break; 384 } 385 386 return nread; 387 } 388 389 static file_ptr 390 cache_bwrite (struct bfd *abfd, const void *where, file_ptr nbytes) 391 { 392 file_ptr nwrite; 393 FILE *f = bfd_cache_lookup (abfd, CACHE_NORMAL); 394 395 if (f == NULL) 396 return 0; 397 nwrite = fwrite (where, 1, nbytes, f); 398 if (nwrite < nbytes && ferror (f)) 399 { 400 bfd_set_error (bfd_error_system_call); 401 return -1; 402 } 403 return nwrite; 404 } 405 406 static int 407 cache_bclose (struct bfd *abfd) 408 { 409 return bfd_cache_close (abfd) - 1; 410 } 411 412 static int 413 cache_bflush (struct bfd *abfd) 414 { 415 int sts; 416 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN); 417 418 if (f == NULL) 419 return 0; 420 sts = fflush (f); 421 if (sts < 0) 422 bfd_set_error (bfd_error_system_call); 423 return sts; 424 } 425 426 static int 427 cache_bstat (struct bfd *abfd, struct stat *sb) 428 { 429 int sts; 430 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR); 431 432 if (f == NULL) 433 return -1; 434 sts = fstat (fileno (f), sb); 435 if (sts < 0) 436 bfd_set_error (bfd_error_system_call); 437 return sts; 438 } 439 440 static void * 441 cache_bmmap (struct bfd *abfd ATTRIBUTE_UNUSED, 442 void *addr ATTRIBUTE_UNUSED, 443 bfd_size_type len ATTRIBUTE_UNUSED, 444 int prot ATTRIBUTE_UNUSED, 445 int flags ATTRIBUTE_UNUSED, 446 file_ptr offset ATTRIBUTE_UNUSED, 447 void **map_addr ATTRIBUTE_UNUSED, 448 bfd_size_type *map_len ATTRIBUTE_UNUSED) 449 { 450 void *ret = (void *) -1; 451 452 if ((abfd->flags & BFD_IN_MEMORY) != 0) 453 abort (); 454 #ifdef HAVE_MMAP 455 else 456 { 457 static uintptr_t pagesize_m1; 458 FILE *f; 459 file_ptr pg_offset; 460 bfd_size_type pg_len; 461 462 f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR); 463 if (f == NULL) 464 return ret; 465 466 if (pagesize_m1 == 0) 467 pagesize_m1 = getpagesize () - 1; 468 469 /* Handle archive members. */ 470 if (abfd->my_archive != NULL 471 && !bfd_is_thin_archive (abfd->my_archive)) 472 offset += abfd->origin; 473 474 /* Align. */ 475 pg_offset = offset & ~pagesize_m1; 476 pg_len = (len + (offset - pg_offset) + pagesize_m1) & ~pagesize_m1; 477 478 ret = mmap (addr, pg_len, prot, flags, fileno (f), pg_offset); 479 if (ret == (void *) -1) 480 bfd_set_error (bfd_error_system_call); 481 else 482 { 483 *map_addr = ret; 484 *map_len = pg_len; 485 ret = (char *) ret + (offset & pagesize_m1); 486 } 487 } 488 #endif 489 490 return ret; 491 } 492 493 static const struct bfd_iovec cache_iovec = 494 { 495 &cache_bread, &cache_bwrite, &cache_btell, &cache_bseek, 496 &cache_bclose, &cache_bflush, &cache_bstat, &cache_bmmap 497 }; 498 499 /* 500 INTERNAL_FUNCTION 501 bfd_cache_init 502 503 SYNOPSIS 504 bfd_boolean bfd_cache_init (bfd *abfd); 505 506 DESCRIPTION 507 Add a newly opened BFD to the cache. 508 */ 509 510 bfd_boolean 511 bfd_cache_init (bfd *abfd) 512 { 513 BFD_ASSERT (abfd->iostream != NULL); 514 if (open_files >= bfd_cache_max_open ()) 515 { 516 if (! close_one ()) 517 return FALSE; 518 } 519 abfd->iovec = &cache_iovec; 520 insert (abfd); 521 ++open_files; 522 return TRUE; 523 } 524 525 /* 526 INTERNAL_FUNCTION 527 bfd_cache_close 528 529 SYNOPSIS 530 bfd_boolean bfd_cache_close (bfd *abfd); 531 532 DESCRIPTION 533 Remove the BFD @var{abfd} from the cache. If the attached file is open, 534 then close it too. 535 536 RETURNS 537 <<FALSE>> is returned if closing the file fails, <<TRUE>> is 538 returned if all is well. 539 */ 540 541 bfd_boolean 542 bfd_cache_close (bfd *abfd) 543 { 544 if (abfd->iovec != &cache_iovec) 545 return TRUE; 546 547 if (abfd->iostream == NULL) 548 /* Previously closed. */ 549 return TRUE; 550 551 return bfd_cache_delete (abfd); 552 } 553 554 /* 555 FUNCTION 556 bfd_cache_close_all 557 558 SYNOPSIS 559 bfd_boolean bfd_cache_close_all (void); 560 561 DESCRIPTION 562 Remove all BFDs from the cache. If the attached file is open, 563 then close it too. 564 565 RETURNS 566 <<FALSE>> is returned if closing one of the file fails, <<TRUE>> is 567 returned if all is well. 568 */ 569 570 bfd_boolean 571 bfd_cache_close_all (void) 572 { 573 bfd_boolean ret = TRUE; 574 575 while (bfd_last_cache != NULL) 576 ret &= bfd_cache_close (bfd_last_cache); 577 578 return ret; 579 } 580 581 /* 582 INTERNAL_FUNCTION 583 bfd_open_file 584 585 SYNOPSIS 586 FILE* bfd_open_file (bfd *abfd); 587 588 DESCRIPTION 589 Call the OS to open a file for @var{abfd}. Return the <<FILE *>> 590 (possibly <<NULL>>) that results from this operation. Set up the 591 BFD so that future accesses know the file is open. If the <<FILE *>> 592 returned is <<NULL>>, then it won't have been put in the 593 cache, so it won't have to be removed from it. 594 */ 595 596 FILE * 597 bfd_open_file (bfd *abfd) 598 { 599 abfd->cacheable = TRUE; /* Allow it to be closed later. */ 600 601 if (open_files >= bfd_cache_max_open ()) 602 { 603 if (! close_one ()) 604 return NULL; 605 } 606 607 switch (abfd->direction) 608 { 609 case read_direction: 610 case no_direction: 611 abfd->iostream = real_fopen (abfd->filename, FOPEN_RB); 612 break; 613 case both_direction: 614 case write_direction: 615 if (abfd->opened_once) 616 { 617 abfd->iostream = real_fopen (abfd->filename, FOPEN_RUB); 618 if (abfd->iostream == NULL) 619 abfd->iostream = real_fopen (abfd->filename, FOPEN_WUB); 620 } 621 else 622 { 623 /* Create the file. 624 625 Some operating systems won't let us overwrite a running 626 binary. For them, we want to unlink the file first. 627 628 However, gcc 2.95 will create temporary files using 629 O_EXCL and tight permissions to prevent other users from 630 substituting other .o files during the compilation. gcc 631 will then tell the assembler to use the newly created 632 file as an output file. If we unlink the file here, we 633 open a brief window when another user could still 634 substitute a file. 635 636 So we unlink the output file if and only if it has 637 non-zero size. */ 638 #ifndef __MSDOS__ 639 /* Don't do this for MSDOS: it doesn't care about overwriting 640 a running binary, but if this file is already open by 641 another BFD, we will be in deep trouble if we delete an 642 open file. In fact, objdump does just that if invoked with 643 the --info option. */ 644 struct stat s; 645 646 if (stat (abfd->filename, &s) == 0 && s.st_size != 0) 647 unlink_if_ordinary (abfd->filename); 648 #endif 649 abfd->iostream = real_fopen (abfd->filename, FOPEN_WUB); 650 abfd->opened_once = TRUE; 651 } 652 break; 653 } 654 655 if (abfd->iostream == NULL) 656 bfd_set_error (bfd_error_system_call); 657 else 658 { 659 if (! bfd_cache_init (abfd)) 660 return NULL; 661 } 662 663 return (FILE *) abfd->iostream; 664 } 665
