1/* BFD library -- caching of file descriptors. 2 3 Copyright (C) 1990-2022 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 48#ifdef HAVE_MMAP 49#include <sys/mman.h> 50#endif 51 52/* In some cases we can optimize cache operation when reopening files. 53 For instance, a flush is entirely unnecessary if the file is already 54 closed, so a flush would use CACHE_NO_OPEN. Similarly, a seek using 55 SEEK_SET or SEEK_END need not first seek to the current position. 56 For stat we ignore seek errors, just in case the file has changed 57 while we weren't looking. If it has, then it's possible that the 58 file is shorter and we don't want a seek error to prevent us doing 59 the stat. */ 60enum cache_flag { 61 CACHE_NORMAL = 0, 62 CACHE_NO_OPEN = 1, 63 CACHE_NO_SEEK = 2, 64 CACHE_NO_SEEK_ERROR = 4 65}; 66 67/* The maximum number of files which the cache will keep open at 68 one time. When needed call bfd_cache_max_open to initialize. */ 69 70static int max_open_files = 0; 71 72/* Set max_open_files, if not already set, to 12.5% of the allowed open 73 file descriptors, but at least 10, and return the value. */ 74static int 75bfd_cache_max_open (void) 76{ 77 if (max_open_files == 0) 78 { 79 int max; 80#if defined(__sun) && !defined(__sparcv9) && !defined(__x86_64__) 81 /* PR ld/19260: 32-bit Solaris has very inelegant handling of the 255 82 file descriptor limit. The problem is that setrlimit(2) can raise 83 RLIMIT_NOFILE to a value that is not supported by libc, resulting 84 in "Too many open files" errors. This can happen here even though 85 max_open_files is set to rlim.rlim_cur / 8. For example, if 86 a parent process has set rlim.rlim_cur to 65536, then max_open_files 87 will be computed as 8192. 88 89 This check essentially reverts to the behavior from binutils 2.23.1 90 for 32-bit Solaris only. (It is hoped that the 32-bit libc 91 limitation will be removed soon). 64-bit Solaris libc does not have 92 this limitation. */ 93 max = 16; 94#else 95#ifdef HAVE_GETRLIMIT 96 struct rlimit rlim; 97 98 if (getrlimit (RLIMIT_NOFILE, &rlim) == 0 99 && rlim.rlim_cur != (rlim_t) RLIM_INFINITY) 100 max = rlim.rlim_cur / 8; 101 else 102#endif 103#ifdef _SC_OPEN_MAX 104 max = sysconf (_SC_OPEN_MAX) / 8; 105#else 106 max = 10; 107#endif 108#endif /* not 32-bit Solaris */ 109 110 max_open_files = max < 10 ? 10 : max; 111 } 112 113 return max_open_files; 114} 115 116/* The number of BFD files we have open. */ 117 118static int open_files; 119 120/* Zero, or a pointer to the topmost BFD on the chain. This is 121 used by the <<bfd_cache_lookup>> macro in @file{libbfd.h} to 122 determine when it can avoid a function call. */ 123 124static bfd *bfd_last_cache = NULL; 125 126/* Insert a BFD into the cache. */ 127 128static void 129insert (bfd *abfd) 130{ 131 if (bfd_last_cache == NULL) 132 { 133 abfd->lru_next = abfd; 134 abfd->lru_prev = abfd; 135 } 136 else 137 { 138 abfd->lru_next = bfd_last_cache; 139 abfd->lru_prev = bfd_last_cache->lru_prev; 140 abfd->lru_prev->lru_next = abfd; 141 abfd->lru_next->lru_prev = abfd; 142 } 143 bfd_last_cache = abfd; 144} 145 146/* Remove a BFD from the cache. */ 147 148static void 149snip (bfd *abfd) 150{ 151 abfd->lru_prev->lru_next = abfd->lru_next; 152 abfd->lru_next->lru_prev = abfd->lru_prev; 153 if (abfd == bfd_last_cache) 154 { 155 bfd_last_cache = abfd->lru_next; 156 if (abfd == bfd_last_cache) 157 bfd_last_cache = NULL; 158 } 159} 160 161/* Close a BFD and remove it from the cache. */ 162 163static bool 164bfd_cache_delete (bfd *abfd) 165{ 166 bool ret; 167 168 if (fclose ((FILE *) abfd->iostream) == 0) 169 ret = true; 170 else 171 { 172 ret = false; 173 bfd_set_error (bfd_error_system_call); 174 } 175 176 snip (abfd); 177 178 abfd->iostream = NULL; 179 --open_files; 180 abfd->flags |= BFD_CLOSED_BY_CACHE; 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 bool 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 = _bfd_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 if ((abfd->flags & BFD_IN_MEMORY) != 0) 241 abort (); 242 243 if (abfd->my_archive != NULL 244 && !bfd_is_thin_archive (abfd->my_archive)) 245 abort (); 246 247 if (abfd->iostream != NULL) 248 { 249 /* Move the file to the start of the cache. */ 250 if (abfd != bfd_last_cache) 251 { 252 snip (abfd); 253 insert (abfd); 254 } 255 return (FILE *) abfd->iostream; 256 } 257 258 if (flag & CACHE_NO_OPEN) 259 return NULL; 260 261 if (bfd_open_file (abfd) == NULL) 262 ; 263 else if (!(flag & CACHE_NO_SEEK) 264 && _bfd_real_fseek ((FILE *) abfd->iostream, 265 abfd->where, SEEK_SET) != 0 266 && !(flag & CACHE_NO_SEEK_ERROR)) 267 bfd_set_error (bfd_error_system_call); 268 else 269 { 270 abfd->flags &= ~BFD_CLOSED_BY_CACHE; 271 return (FILE *) abfd->iostream; 272 } 273 274 /* xgettext:c-format */ 275 _bfd_error_handler (_("reopening %pB: %s"), 276 abfd, bfd_errmsg (bfd_get_error ())); 277 return NULL; 278} 279 280static file_ptr 281cache_btell (struct bfd *abfd) 282{ 283 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN); 284 if (f == NULL) 285 return abfd->where; 286 return _bfd_real_ftell (f); 287} 288 289static int 290cache_bseek (struct bfd *abfd, file_ptr offset, int whence) 291{ 292 FILE *f = bfd_cache_lookup (abfd, whence != SEEK_CUR ? CACHE_NO_SEEK : CACHE_NORMAL); 293 if (f == NULL) 294 return -1; 295 return _bfd_real_fseek (f, offset, whence); 296} 297 298/* Note that archive entries don't have streams; they share their parent's. 299 This allows someone to play with the iostream behind BFD's back. 300 301 Also, note that the origin pointer points to the beginning of a file's 302 contents (0 for non-archive elements). For archive entries this is the 303 first octet in the file, NOT the beginning of the archive header. */ 304 305static file_ptr 306cache_bread_1 (FILE *f, void *buf, file_ptr nbytes) 307{ 308 file_ptr nread; 309 310#if defined (__VAX) && defined (VMS) 311 /* Apparently fread on Vax VMS does not keep the record length 312 information. */ 313 nread = read (fileno (f), buf, nbytes); 314 /* Set bfd_error if we did not read as much data as we expected. If 315 the read failed due to an error set the bfd_error_system_call, 316 else set bfd_error_file_truncated. */ 317 if (nread == (file_ptr)-1) 318 { 319 bfd_set_error (bfd_error_system_call); 320 return nread; 321 } 322#else 323 nread = fread (buf, 1, nbytes, f); 324 /* Set bfd_error if we did not read as much data as we expected. If 325 the read failed due to an error set the bfd_error_system_call, 326 else set bfd_error_file_truncated. */ 327 if (nread < nbytes && ferror (f)) 328 { 329 bfd_set_error (bfd_error_system_call); 330 return nread; 331 } 332#endif 333 if (nread < nbytes) 334 /* This may or may not be an error, but in case the calling code 335 bails out because of it, set the right error code. */ 336 bfd_set_error (bfd_error_file_truncated); 337 return nread; 338} 339 340static file_ptr 341cache_bread (struct bfd *abfd, void *buf, file_ptr nbytes) 342{ 343 file_ptr nread = 0; 344 FILE *f; 345 346 f = bfd_cache_lookup (abfd, CACHE_NORMAL); 347 if (f == NULL) 348 return -1; 349 350 /* Some filesystems are unable to handle reads that are too large 351 (for instance, NetApp shares with oplocks turned off). To avoid 352 hitting this limitation, we read the buffer in chunks of 8MB max. */ 353 while (nread < nbytes) 354 { 355 const file_ptr max_chunk_size = 0x800000; 356 file_ptr chunk_size = nbytes - nread; 357 file_ptr chunk_nread; 358 359 if (chunk_size > max_chunk_size) 360 chunk_size = max_chunk_size; 361 362 chunk_nread = cache_bread_1 (f, (char *) buf + nread, chunk_size); 363 364 /* Update the nread count. 365 366 We just have to be careful of the case when cache_bread_1 returns 367 a negative count: If this is our first read, then set nread to 368 that negative count in order to return that negative value to the 369 caller. Otherwise, don't add it to our total count, or we would 370 end up returning a smaller number of bytes read than we actually 371 did. */ 372 if (nread == 0 || chunk_nread > 0) 373 nread += chunk_nread; 374 375 if (chunk_nread < chunk_size) 376 break; 377 } 378 379 return nread; 380} 381 382static file_ptr 383cache_bwrite (struct bfd *abfd, const void *from, file_ptr nbytes) 384{ 385 file_ptr nwrite; 386 FILE *f = bfd_cache_lookup (abfd, CACHE_NORMAL); 387 388 if (f == NULL) 389 return 0; 390 nwrite = fwrite (from, 1, nbytes, f); 391 if (nwrite < nbytes && ferror (f)) 392 { 393 bfd_set_error (bfd_error_system_call); 394 return -1; 395 } 396 return nwrite; 397} 398 399static int 400cache_bclose (struct bfd *abfd) 401{ 402 return bfd_cache_close (abfd) - 1; 403} 404 405static int 406cache_bflush (struct bfd *abfd) 407{ 408 int sts; 409 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN); 410 411 if (f == NULL) 412 return 0; 413 sts = fflush (f); 414 if (sts < 0) 415 bfd_set_error (bfd_error_system_call); 416 return sts; 417} 418 419static int 420cache_bstat (struct bfd *abfd, struct stat *sb) 421{ 422 int sts; 423 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR); 424 425 if (f == NULL) 426 return -1; 427 sts = fstat (fileno (f), sb); 428 if (sts < 0) 429 bfd_set_error (bfd_error_system_call); 430 return sts; 431} 432 433static void * 434cache_bmmap (struct bfd *abfd ATTRIBUTE_UNUSED, 435 void *addr ATTRIBUTE_UNUSED, 436 bfd_size_type len ATTRIBUTE_UNUSED, 437 int prot ATTRIBUTE_UNUSED, 438 int flags ATTRIBUTE_UNUSED, 439 file_ptr offset ATTRIBUTE_UNUSED, 440 void **map_addr ATTRIBUTE_UNUSED, 441 bfd_size_type *map_len ATTRIBUTE_UNUSED) 442{ 443 void *ret = (void *) -1; 444 445 if ((abfd->flags & BFD_IN_MEMORY) != 0) 446 abort (); 447#ifdef HAVE_MMAP 448 else 449 { 450 static uintptr_t pagesize_m1; 451 FILE *f; 452 file_ptr pg_offset; 453 bfd_size_type pg_len; 454 455 f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR); 456 if (f == NULL) 457 return ret; 458 459 if (pagesize_m1 == 0) 460 pagesize_m1 = getpagesize () - 1; 461 462 /* Align. */ 463 pg_offset = offset & ~pagesize_m1; 464 pg_len = (len + (offset - pg_offset) + pagesize_m1) & ~pagesize_m1; 465 466 ret = mmap (addr, pg_len, prot, flags, fileno (f), pg_offset); 467 if (ret == (void *) -1) 468 bfd_set_error (bfd_error_system_call); 469 else 470 { 471 *map_addr = ret; 472 *map_len = pg_len; 473 ret = (char *) ret + (offset & pagesize_m1); 474 } 475 } 476#endif 477 478 return ret; 479} 480 481static const struct bfd_iovec cache_iovec = 482{ 483 &cache_bread, &cache_bwrite, &cache_btell, &cache_bseek, 484 &cache_bclose, &cache_bflush, &cache_bstat, &cache_bmmap 485}; 486 487/* 488INTERNAL_FUNCTION 489 bfd_cache_init 490 491SYNOPSIS 492 bool bfd_cache_init (bfd *abfd); 493 494DESCRIPTION 495 Add a newly opened BFD to the cache. 496*/ 497 498bool 499bfd_cache_init (bfd *abfd) 500{ 501 BFD_ASSERT (abfd->iostream != NULL); 502 if (open_files >= bfd_cache_max_open ()) 503 { 504 if (! close_one ()) 505 return false; 506 } 507 abfd->iovec = &cache_iovec; 508 insert (abfd); 509 ++open_files; 510 return true; 511} 512 513/* 514INTERNAL_FUNCTION 515 bfd_cache_close 516 517SYNOPSIS 518 bool bfd_cache_close (bfd *abfd); 519 520DESCRIPTION 521 Remove the BFD @var{abfd} from the cache. If the attached file is open, 522 then close it too. 523 524RETURNS 525 <<FALSE>> is returned if closing the file fails, <<TRUE>> is 526 returned if all is well. 527*/ 528 529bool 530bfd_cache_close (bfd *abfd) 531{ 532 if (abfd->iovec != &cache_iovec) 533 return true; 534 535 if (abfd->iostream == NULL) 536 /* Previously closed. */ 537 return true; 538 539 return bfd_cache_delete (abfd); 540} 541 542/* 543FUNCTION 544 bfd_cache_close_all 545 546SYNOPSIS 547 bool bfd_cache_close_all (void); 548 549DESCRIPTION 550 Remove all BFDs from the cache. If the attached file is open, 551 then close it too. 552 553RETURNS 554 <<FALSE>> is returned if closing one of the file fails, <<TRUE>> is 555 returned if all is well. 556*/ 557 558bool 559bfd_cache_close_all (void) 560{ 561 bool ret = true; 562 563 while (bfd_last_cache != NULL) 564 ret &= bfd_cache_close (bfd_last_cache); 565 566 return ret; 567} 568 569/* 570INTERNAL_FUNCTION 571 bfd_open_file 572 573SYNOPSIS 574 FILE* bfd_open_file (bfd *abfd); 575 576DESCRIPTION 577 Call the OS to open a file for @var{abfd}. Return the <<FILE *>> 578 (possibly <<NULL>>) that results from this operation. Set up the 579 BFD so that future accesses know the file is open. If the <<FILE *>> 580 returned is <<NULL>>, then it won't have been put in the 581 cache, so it won't have to be removed from it. 582*/ 583 584FILE * 585bfd_open_file (bfd *abfd) 586{ 587 abfd->cacheable = true; /* Allow it to be closed later. */ 588 589 if (open_files >= bfd_cache_max_open ()) 590 { 591 if (! close_one ()) 592 return NULL; 593 } 594 595 switch (abfd->direction) 596 { 597 case read_direction: 598 case no_direction: 599 abfd->iostream = _bfd_real_fopen (bfd_get_filename (abfd), FOPEN_RB); 600 break; 601 case both_direction: 602 case write_direction: 603 if (abfd->opened_once) 604 { 605 abfd->iostream = _bfd_real_fopen (bfd_get_filename (abfd), 606 FOPEN_RUB); 607 if (abfd->iostream == NULL) 608 abfd->iostream = _bfd_real_fopen (bfd_get_filename (abfd), 609 FOPEN_WUB); 610 } 611 else 612 { 613 /* Create the file. 614 615 Some operating systems won't let us overwrite a running 616 binary. For them, we want to unlink the file first. 617 618 However, gcc 2.95 will create temporary files using 619 O_EXCL and tight permissions to prevent other users from 620 substituting other .o files during the compilation. gcc 621 will then tell the assembler to use the newly created 622 file as an output file. If we unlink the file here, we 623 open a brief window when another user could still 624 substitute a file. 625 626 So we unlink the output file if and only if it has 627 non-zero size. */ 628#ifndef __MSDOS__ 629 /* Don't do this for MSDOS: it doesn't care about overwriting 630 a running binary, but if this file is already open by 631 another BFD, we will be in deep trouble if we delete an 632 open file. In fact, objdump does just that if invoked with 633 the --info option. */ 634 struct stat s; 635 636 if (stat (bfd_get_filename (abfd), &s) == 0 && s.st_size != 0) 637 unlink_if_ordinary (bfd_get_filename (abfd)); 638#endif 639 abfd->iostream = _bfd_real_fopen (bfd_get_filename (abfd), 640 FOPEN_WUB); 641 abfd->opened_once = true; 642 } 643 break; 644 } 645 646 if (abfd->iostream == NULL) 647 bfd_set_error (bfd_error_system_call); 648 else 649 { 650 if (! bfd_cache_init (abfd)) 651 return NULL; 652 } 653 654 return (FILE *) abfd->iostream; 655} 656