1/* BFD library -- caching of file descriptors. 2 3 Copyright (C) 1990-2017 Free Software Foundation, Inc. 4 5 Hacked by Steve Chamberlain of Cygnus Support (steve@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/* 25SECTION 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 39SUBSECTION 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. */ 61enum 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 71static 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. */ 75static int 76bfd_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 119static 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 125static bfd *bfd_last_cache = NULL; 126 127/* Insert a BFD into the cache. */ 128 129static void 130insert (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 149static void 150snip (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 164static bfd_boolean 165bfd_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 188static bfd_boolean 189close_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 237static FILE * 238bfd_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 /* xgettext:c-format */ 272 _bfd_error_handler (_("reopening %B: %s\n"), 273 orig_bfd, bfd_errmsg (bfd_get_error ())); 274 return NULL; 275} 276 277static file_ptr 278cache_btell (struct bfd *abfd) 279{ 280 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN); 281 if (f == NULL) 282 return abfd->where; 283 return real_ftell (f); 284} 285 286static int 287cache_bseek (struct bfd *abfd, file_ptr offset, int whence) 288{ 289 FILE *f = bfd_cache_lookup (abfd, whence != SEEK_CUR ? CACHE_NO_SEEK : CACHE_NORMAL); 290 if (f == NULL) 291 return -1; 292 return real_fseek (f, offset, whence); 293} 294 295/* Note that archive entries don't have streams; they share their parent's. 296 This allows someone to play with the iostream behind BFD's back. 297 298 Also, note that the origin pointer points to the beginning of a file's 299 contents (0 for non-archive elements). For archive entries this is the 300 first octet in the file, NOT the beginning of the archive header. */ 301 302static file_ptr 303cache_bread_1 (struct bfd *abfd, void *buf, file_ptr nbytes) 304{ 305 FILE *f; 306 file_ptr nread; 307 /* FIXME - this looks like an optimization, but it's really to cover 308 up for a feature of some OSs (not solaris - sigh) that 309 ld/pe-dll.c takes advantage of (apparently) when it creates BFDs 310 internally and tries to link against them. BFD seems to be smart 311 enough to realize there are no symbol records in the "file" that 312 doesn't exist but attempts to read them anyway. On Solaris, 313 attempting to read zero bytes from a NULL file results in a core 314 dump, but on other platforms it just returns zero bytes read. 315 This makes it to something reasonable. - DJ */ 316 if (nbytes == 0) 317 return 0; 318 319 f = bfd_cache_lookup (abfd, CACHE_NORMAL); 320 if (f == NULL) 321 return 0; 322 323#if defined (__VAX) && defined (VMS) 324 /* Apparently fread on Vax VMS does not keep the record length 325 information. */ 326 nread = read (fileno (f), buf, nbytes); 327 /* Set bfd_error if we did not read as much data as we expected. If 328 the read failed due to an error set the bfd_error_system_call, 329 else set bfd_error_file_truncated. */ 330 if (nread == (file_ptr)-1) 331 { 332 bfd_set_error (bfd_error_system_call); 333 return nread; 334 } 335#else 336 nread = fread (buf, 1, nbytes, f); 337 /* Set bfd_error if we did not read as much data as we expected. If 338 the read failed due to an error set the bfd_error_system_call, 339 else set bfd_error_file_truncated. */ 340 if (nread < nbytes && ferror (f)) 341 { 342 bfd_set_error (bfd_error_system_call); 343 return nread; 344 } 345#endif 346 if (nread < nbytes) 347 /* This may or may not be an error, but in case the calling code 348 bails out because of it, set the right error code. */ 349 bfd_set_error (bfd_error_file_truncated); 350 return nread; 351} 352 353static file_ptr 354cache_bread (struct bfd *abfd, void *buf, file_ptr nbytes) 355{ 356 file_ptr nread = 0; 357 358 /* Some filesystems are unable to handle reads that are too large 359 (for instance, NetApp shares with oplocks turned off). To avoid 360 hitting this limitation, we read the buffer in chunks of 8MB max. */ 361 while (nread < nbytes) 362 { 363 const file_ptr max_chunk_size = 0x800000; 364 file_ptr chunk_size = nbytes - nread; 365 file_ptr chunk_nread; 366 367 if (chunk_size > max_chunk_size) 368 chunk_size = max_chunk_size; 369 370 chunk_nread = cache_bread_1 (abfd, (char *) buf + nread, chunk_size); 371 372 /* Update the nread count. 373 374 We just have to be careful of the case when cache_bread_1 returns 375 a negative count: If this is our first read, then set nread to 376 that negative count in order to return that negative value to the 377 caller. Otherwise, don't add it to our total count, or we would 378 end up returning a smaller number of bytes read than we actually 379 did. */ 380 if (nread == 0 || chunk_nread > 0) 381 nread += chunk_nread; 382 383 if (chunk_nread < chunk_size) 384 break; 385 } 386 387 return nread; 388} 389 390static file_ptr 391cache_bwrite (struct bfd *abfd, const void *where, file_ptr nbytes) 392{ 393 file_ptr nwrite; 394 FILE *f = bfd_cache_lookup (abfd, CACHE_NORMAL); 395 396 if (f == NULL) 397 return 0; 398 nwrite = fwrite (where, 1, nbytes, f); 399 if (nwrite < nbytes && ferror (f)) 400 { 401 bfd_set_error (bfd_error_system_call); 402 return -1; 403 } 404 return nwrite; 405} 406 407static int 408cache_bclose (struct bfd *abfd) 409{ 410 return bfd_cache_close (abfd) - 1; 411} 412 413static int 414cache_bflush (struct bfd *abfd) 415{ 416 int sts; 417 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN); 418 419 if (f == NULL) 420 return 0; 421 sts = fflush (f); 422 if (sts < 0) 423 bfd_set_error (bfd_error_system_call); 424 return sts; 425} 426 427static int 428cache_bstat (struct bfd *abfd, struct stat *sb) 429{ 430 int sts; 431 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR); 432 433 if (f == NULL) 434 return -1; 435 sts = fstat (fileno (f), sb); 436 if (sts < 0) 437 bfd_set_error (bfd_error_system_call); 438 return sts; 439} 440 441static void * 442cache_bmmap (struct bfd *abfd ATTRIBUTE_UNUSED, 443 void *addr ATTRIBUTE_UNUSED, 444 bfd_size_type len ATTRIBUTE_UNUSED, 445 int prot ATTRIBUTE_UNUSED, 446 int flags ATTRIBUTE_UNUSED, 447 file_ptr offset ATTRIBUTE_UNUSED, 448 void **map_addr ATTRIBUTE_UNUSED, 449 bfd_size_type *map_len ATTRIBUTE_UNUSED) 450{ 451 void *ret = (void *) -1; 452 453 if ((abfd->flags & BFD_IN_MEMORY) != 0) 454 abort (); 455#ifdef HAVE_MMAP 456 else 457 { 458 static uintptr_t pagesize_m1; 459 FILE *f; 460 file_ptr pg_offset; 461 bfd_size_type pg_len; 462 463 f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR); 464 if (f == NULL) 465 return ret; 466 467 if (pagesize_m1 == 0) 468 pagesize_m1 = getpagesize () - 1; 469 470 /* Handle archive members. */ 471 if (abfd->my_archive != NULL 472 && !bfd_is_thin_archive (abfd->my_archive)) 473 offset += abfd->origin; 474 475 /* Align. */ 476 pg_offset = offset & ~pagesize_m1; 477 pg_len = (len + (offset - pg_offset) + pagesize_m1) & ~pagesize_m1; 478 479 ret = mmap (addr, pg_len, prot, flags, fileno (f), pg_offset); 480 if (ret == (void *) -1) 481 bfd_set_error (bfd_error_system_call); 482 else 483 { 484 *map_addr = ret; 485 *map_len = pg_len; 486 ret = (char *) ret + (offset & pagesize_m1); 487 } 488 } 489#endif 490 491 return ret; 492} 493 494static const struct bfd_iovec cache_iovec = 495{ 496 &cache_bread, &cache_bwrite, &cache_btell, &cache_bseek, 497 &cache_bclose, &cache_bflush, &cache_bstat, &cache_bmmap 498}; 499 500/* 501INTERNAL_FUNCTION 502 bfd_cache_init 503 504SYNOPSIS 505 bfd_boolean bfd_cache_init (bfd *abfd); 506 507DESCRIPTION 508 Add a newly opened BFD to the cache. 509*/ 510 511bfd_boolean 512bfd_cache_init (bfd *abfd) 513{ 514 BFD_ASSERT (abfd->iostream != NULL); 515 if (open_files >= bfd_cache_max_open ()) 516 { 517 if (! close_one ()) 518 return FALSE; 519 } 520 abfd->iovec = &cache_iovec; 521 insert (abfd); 522 ++open_files; 523 return TRUE; 524} 525 526/* 527INTERNAL_FUNCTION 528 bfd_cache_close 529 530SYNOPSIS 531 bfd_boolean bfd_cache_close (bfd *abfd); 532 533DESCRIPTION 534 Remove the BFD @var{abfd} from the cache. If the attached file is open, 535 then close it too. 536 537RETURNS 538 <<FALSE>> is returned if closing the file fails, <<TRUE>> is 539 returned if all is well. 540*/ 541 542bfd_boolean 543bfd_cache_close (bfd *abfd) 544{ 545 if (abfd->iovec != &cache_iovec) 546 return TRUE; 547 548 if (abfd->iostream == NULL) 549 /* Previously closed. */ 550 return TRUE; 551 552 return bfd_cache_delete (abfd); 553} 554 555/* 556FUNCTION 557 bfd_cache_close_all 558 559SYNOPSIS 560 bfd_boolean bfd_cache_close_all (void); 561 562DESCRIPTION 563 Remove all BFDs from the cache. If the attached file is open, 564 then close it too. 565 566RETURNS 567 <<FALSE>> is returned if closing one of the file fails, <<TRUE>> is 568 returned if all is well. 569*/ 570 571bfd_boolean 572bfd_cache_close_all (void) 573{ 574 bfd_boolean ret = TRUE; 575 576 while (bfd_last_cache != NULL) 577 ret &= bfd_cache_close (bfd_last_cache); 578 579 return ret; 580} 581 582/* 583INTERNAL_FUNCTION 584 bfd_open_file 585 586SYNOPSIS 587 FILE* bfd_open_file (bfd *abfd); 588 589DESCRIPTION 590 Call the OS to open a file for @var{abfd}. Return the <<FILE *>> 591 (possibly <<NULL>>) that results from this operation. Set up the 592 BFD so that future accesses know the file is open. If the <<FILE *>> 593 returned is <<NULL>>, then it won't have been put in the 594 cache, so it won't have to be removed from it. 595*/ 596 597FILE * 598bfd_open_file (bfd *abfd) 599{ 600 abfd->cacheable = TRUE; /* Allow it to be closed later. */ 601 602 if (open_files >= bfd_cache_max_open ()) 603 { 604 if (! close_one ()) 605 return NULL; 606 } 607 608 switch (abfd->direction) 609 { 610 case read_direction: 611 case no_direction: 612 abfd->iostream = real_fopen (abfd->filename, FOPEN_RB); 613 break; 614 case both_direction: 615 case write_direction: 616 if (abfd->opened_once) 617 { 618 abfd->iostream = real_fopen (abfd->filename, FOPEN_RUB); 619 if (abfd->iostream == NULL) 620 abfd->iostream = real_fopen (abfd->filename, FOPEN_WUB); 621 } 622 else 623 { 624 /* Create the file. 625 626 Some operating systems won't let us overwrite a running 627 binary. For them, we want to unlink the file first. 628 629 However, gcc 2.95 will create temporary files using 630 O_EXCL and tight permissions to prevent other users from 631 substituting other .o files during the compilation. gcc 632 will then tell the assembler to use the newly created 633 file as an output file. If we unlink the file here, we 634 open a brief window when another user could still 635 substitute a file. 636 637 So we unlink the output file if and only if it has 638 non-zero size. */ 639#ifndef __MSDOS__ 640 /* Don't do this for MSDOS: it doesn't care about overwriting 641 a running binary, but if this file is already open by 642 another BFD, we will be in deep trouble if we delete an 643 open file. In fact, objdump does just that if invoked with 644 the --info option. */ 645 struct stat s; 646 647 if (stat (abfd->filename, &s) == 0 && s.st_size != 0) 648 unlink_if_ordinary (abfd->filename); 649#endif 650 abfd->iostream = real_fopen (abfd->filename, FOPEN_WUB); 651 abfd->opened_once = TRUE; 652 } 653 break; 654 } 655 656 if (abfd->iostream == NULL) 657 bfd_set_error (bfd_error_system_call); 658 else 659 { 660 if (! bfd_cache_init (abfd)) 661 return NULL; 662 } 663 664 return (FILE *) abfd->iostream; 665} 666