| 1 | /* BFD library -- caching of file descriptors. |
| 2 | |
| 3 | Copyright 1990, 1991, 1992, 1993, 1994, 1996, 2000, 2001, 2002, |
| 4 | 2003, 2004, 2005, 2007 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 2 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, 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 | |
| 48 | /* In some cases we can optimize cache operation when reopening files. |
| 49 | For instance, a flush is entirely unnecessary if the file is already |
| 50 | closed, so a flush would use CACHE_NO_OPEN. Similarly, a seek using |
| 51 | SEEK_SET or SEEK_END need not first seek to the current position. |
| 52 | For stat we ignore seek errors, just in case the file has changed |
| 53 | while we weren't looking. If it has, then it's possible that the |
| 54 | file is shorter and we don't want a seek error to prevent us doing |
| 55 | the stat. */ |
| 56 | enum cache_flag { |
| 57 | CACHE_NORMAL = 0, |
| 58 | CACHE_NO_OPEN = 1, |
| 59 | CACHE_NO_SEEK = 2, |
| 60 | CACHE_NO_SEEK_ERROR = 4 |
| 61 | }; |
| 62 | |
| 63 | /* The maximum number of files which the cache will keep open at |
| 64 | one time. */ |
| 65 | |
| 66 | #define BFD_CACHE_MAX_OPEN 10 |
| 67 | |
| 68 | /* The number of BFD files we have open. */ |
| 69 | |
| 70 | static int open_files; |
| 71 | |
| 72 | /* Zero, or a pointer to the topmost BFD on the chain. This is |
| 73 | used by the <<bfd_cache_lookup>> macro in @file{libbfd.h} to |
| 74 | determine when it can avoid a function call. */ |
| 75 | |
| 76 | static bfd *bfd_last_cache = NULL; |
| 77 | |
| 78 | /* Insert a BFD into the cache. */ |
| 79 | |
| 80 | static void |
| 81 | insert (bfd *abfd) |
| 82 | { |
| 83 | if (bfd_last_cache == NULL) |
| 84 | { |
| 85 | abfd->lru_next = abfd; |
| 86 | abfd->lru_prev = abfd; |
| 87 | } |
| 88 | else |
| 89 | { |
| 90 | abfd->lru_next = bfd_last_cache; |
| 91 | abfd->lru_prev = bfd_last_cache->lru_prev; |
| 92 | abfd->lru_prev->lru_next = abfd; |
| 93 | abfd->lru_next->lru_prev = abfd; |
| 94 | } |
| 95 | bfd_last_cache = abfd; |
| 96 | } |
| 97 | |
| 98 | /* Remove a BFD from the cache. */ |
| 99 | |
| 100 | static void |
| 101 | snip (bfd *abfd) |
| 102 | { |
| 103 | abfd->lru_prev->lru_next = abfd->lru_next; |
| 104 | abfd->lru_next->lru_prev = abfd->lru_prev; |
| 105 | if (abfd == bfd_last_cache) |
| 106 | { |
| 107 | bfd_last_cache = abfd->lru_next; |
| 108 | if (abfd == bfd_last_cache) |
| 109 | bfd_last_cache = NULL; |
| 110 | } |
| 111 | } |
| 112 | |
| 113 | /* Close a BFD and remove it from the cache. */ |
| 114 | |
| 115 | static bfd_boolean |
| 116 | bfd_cache_delete (bfd *abfd) |
| 117 | { |
| 118 | bfd_boolean ret; |
| 119 | |
| 120 | if (fclose ((FILE *) abfd->iostream) == 0) |
| 121 | ret = TRUE; |
| 122 | else |
| 123 | { |
| 124 | ret = FALSE; |
| 125 | bfd_set_error (bfd_error_system_call); |
| 126 | } |
| 127 | |
| 128 | snip (abfd); |
| 129 | |
| 130 | abfd->iostream = NULL; |
| 131 | --open_files; |
| 132 | |
| 133 | return ret; |
| 134 | } |
| 135 | |
| 136 | /* We need to open a new file, and the cache is full. Find the least |
| 137 | recently used cacheable BFD and close it. */ |
| 138 | |
| 139 | static bfd_boolean |
| 140 | close_one (void) |
| 141 | { |
| 142 | register bfd *kill; |
| 143 | |
| 144 | if (bfd_last_cache == NULL) |
| 145 | kill = NULL; |
| 146 | else |
| 147 | { |
| 148 | for (kill = bfd_last_cache->lru_prev; |
| 149 | ! kill->cacheable; |
| 150 | kill = kill->lru_prev) |
| 151 | { |
| 152 | if (kill == bfd_last_cache) |
| 153 | { |
| 154 | kill = NULL; |
| 155 | break; |
| 156 | } |
| 157 | } |
| 158 | } |
| 159 | |
| 160 | if (kill == NULL) |
| 161 | { |
| 162 | /* There are no open cacheable BFD's. */ |
| 163 | return TRUE; |
| 164 | } |
| 165 | |
| 166 | kill->where = real_ftell ((FILE *) kill->iostream); |
| 167 | |
| 168 | /* Save the file st_mtime. This is a hack so that gdb can detect when |
| 169 | an executable has been deleted and recreated. The only thing that |
| 170 | makes this reasonable is that st_mtime doesn't change when a file |
| 171 | is unlinked, so saving st_mtime makes BFD's file cache operation |
| 172 | a little more transparent for this particular usage pattern. If we |
| 173 | hadn't closed the file then we would not have lost the original |
| 174 | contents, st_mtime etc. Of course, if something is writing to an |
| 175 | existing file, then this is the wrong thing to do. |
| 176 | FIXME: gdb should save these times itself on first opening a file, |
| 177 | and this hack be removed. */ |
| 178 | if (kill->direction == no_direction || kill->direction == read_direction) |
| 179 | { |
| 180 | bfd_get_mtime (kill); |
| 181 | kill->mtime_set = TRUE; |
| 182 | } |
| 183 | |
| 184 | return bfd_cache_delete (kill); |
| 185 | } |
| 186 | |
| 187 | /* Check to see if the required BFD is the same as the last one |
| 188 | looked up. If so, then it can use the stream in the BFD with |
| 189 | impunity, since it can't have changed since the last lookup; |
| 190 | otherwise, it has to perform the complicated lookup function. */ |
| 191 | |
| 192 | #define bfd_cache_lookup(x, flag) \ |
| 193 | ((x) == bfd_last_cache \ |
| 194 | ? (FILE *) (bfd_last_cache->iostream) \ |
| 195 | : bfd_cache_lookup_worker (x, flag)) |
| 196 | |
| 197 | /* Called when the macro <<bfd_cache_lookup>> fails to find a |
| 198 | quick answer. Find a file descriptor for @var{abfd}. If |
| 199 | necessary, it open it. If there are already more than |
| 200 | <<BFD_CACHE_MAX_OPEN>> files open, it tries to close one first, to |
| 201 | avoid running out of file descriptors. It will return NULL |
| 202 | if it is unable to (re)open the @var{abfd}. */ |
| 203 | |
| 204 | static FILE * |
| 205 | bfd_cache_lookup_worker (bfd *abfd, enum cache_flag flag) |
| 206 | { |
| 207 | bfd *orig_bfd = abfd; |
| 208 | if ((abfd->flags & BFD_IN_MEMORY) != 0) |
| 209 | abort (); |
| 210 | |
| 211 | if (abfd->my_archive) |
| 212 | abfd = abfd->my_archive; |
| 213 | |
| 214 | if (abfd->iostream != NULL) |
| 215 | { |
| 216 | /* Move the file to the start of the cache. */ |
| 217 | if (abfd != bfd_last_cache) |
| 218 | { |
| 219 | snip (abfd); |
| 220 | insert (abfd); |
| 221 | } |
| 222 | return (FILE *) abfd->iostream; |
| 223 | } |
| 224 | |
| 225 | if (flag & CACHE_NO_OPEN) |
| 226 | return NULL; |
| 227 | |
| 228 | if (bfd_open_file (abfd) == NULL) |
| 229 | ; |
| 230 | else if (!(flag & CACHE_NO_SEEK) |
| 231 | && real_fseek ((FILE *) abfd->iostream, abfd->where, SEEK_SET) != 0 |
| 232 | && !(flag & CACHE_NO_SEEK_ERROR)) |
| 233 | bfd_set_error (bfd_error_system_call); |
| 234 | else |
| 235 | return (FILE *) abfd->iostream; |
| 236 | |
| 237 | (*_bfd_error_handler) (_("reopening %B: %s\n"), |
| 238 | orig_bfd, bfd_errmsg (bfd_get_error ())); |
| 239 | return NULL; |
| 240 | } |
| 241 | |
| 242 | static file_ptr |
| 243 | cache_btell (struct bfd *abfd) |
| 244 | { |
| 245 | FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN); |
| 246 | if (f == NULL) |
| 247 | return abfd->where; |
| 248 | return real_ftell (f); |
| 249 | } |
| 250 | |
| 251 | static int |
| 252 | cache_bseek (struct bfd *abfd, file_ptr offset, int whence) |
| 253 | { |
| 254 | FILE *f = bfd_cache_lookup (abfd, whence != SEEK_CUR ? CACHE_NO_SEEK : 0); |
| 255 | if (f == NULL) |
| 256 | return -1; |
| 257 | return real_fseek (f, offset, whence); |
| 258 | } |
| 259 | |
| 260 | /* Note that archive entries don't have streams; they share their parent's. |
| 261 | This allows someone to play with the iostream behind BFD's back. |
| 262 | |
| 263 | Also, note that the origin pointer points to the beginning of a file's |
| 264 | contents (0 for non-archive elements). For archive entries this is the |
| 265 | first octet in the file, NOT the beginning of the archive header. */ |
| 266 | |
| 267 | static file_ptr |
| 268 | cache_bread (struct bfd *abfd, void *buf, file_ptr nbytes) |
| 269 | { |
| 270 | FILE *f; |
| 271 | file_ptr nread; |
| 272 | /* FIXME - this looks like an optimization, but it's really to cover |
| 273 | up for a feature of some OSs (not solaris - sigh) that |
| 274 | ld/pe-dll.c takes advantage of (apparently) when it creates BFDs |
| 275 | internally and tries to link against them. BFD seems to be smart |
| 276 | enough to realize there are no symbol records in the "file" that |
| 277 | doesn't exist but attempts to read them anyway. On Solaris, |
| 278 | attempting to read zero bytes from a NULL file results in a core |
| 279 | dump, but on other platforms it just returns zero bytes read. |
| 280 | This makes it to something reasonable. - DJ */ |
| 281 | if (nbytes == 0) |
| 282 | return 0; |
| 283 | |
| 284 | f = bfd_cache_lookup (abfd, 0); |
| 285 | if (f == NULL) |
| 286 | return 0; |
| 287 | |
| 288 | #if defined (__VAX) && defined (VMS) |
| 289 | /* Apparently fread on Vax VMS does not keep the record length |
| 290 | information. */ |
| 291 | nread = read (fileno (f), buf, nbytes); |
| 292 | /* Set bfd_error if we did not read as much data as we expected. If |
| 293 | the read failed due to an error set the bfd_error_system_call, |
| 294 | else set bfd_error_file_truncated. */ |
| 295 | if (nread == (file_ptr)-1) |
| 296 | { |
| 297 | bfd_set_error (bfd_error_system_call); |
| 298 | return -1; |
| 299 | } |
| 300 | #else |
| 301 | nread = fread (buf, 1, nbytes, f); |
| 302 | /* Set bfd_error if we did not read as much data as we expected. If |
| 303 | the read failed due to an error set the bfd_error_system_call, |
| 304 | else set bfd_error_file_truncated. */ |
| 305 | if (nread < nbytes && ferror (f)) |
| 306 | { |
| 307 | bfd_set_error (bfd_error_system_call); |
| 308 | return -1; |
| 309 | } |
| 310 | #endif |
| 311 | return nread; |
| 312 | } |
| 313 | |
| 314 | static file_ptr |
| 315 | cache_bwrite (struct bfd *abfd, const void *where, file_ptr nbytes) |
| 316 | { |
| 317 | file_ptr nwrite; |
| 318 | FILE *f = bfd_cache_lookup (abfd, 0); |
| 319 | if (f == NULL) |
| 320 | return 0; |
| 321 | nwrite = fwrite (where, 1, nbytes, f); |
| 322 | if (nwrite < nbytes && ferror (f)) |
| 323 | { |
| 324 | bfd_set_error (bfd_error_system_call); |
| 325 | return -1; |
| 326 | } |
| 327 | return nwrite; |
| 328 | } |
| 329 | |
| 330 | static int |
| 331 | cache_bclose (struct bfd *abfd) |
| 332 | { |
| 333 | return bfd_cache_close (abfd); |
| 334 | } |
| 335 | |
| 336 | static int |
| 337 | cache_bflush (struct bfd *abfd) |
| 338 | { |
| 339 | int sts; |
| 340 | FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN); |
| 341 | if (f == NULL) |
| 342 | return 0; |
| 343 | sts = fflush (f); |
| 344 | if (sts < 0) |
| 345 | bfd_set_error (bfd_error_system_call); |
| 346 | return sts; |
| 347 | } |
| 348 | |
| 349 | static int |
| 350 | cache_bstat (struct bfd *abfd, struct stat *sb) |
| 351 | { |
| 352 | int sts; |
| 353 | FILE *f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR); |
| 354 | if (f == NULL) |
| 355 | return -1; |
| 356 | sts = fstat (fileno (f), sb); |
| 357 | if (sts < 0) |
| 358 | bfd_set_error (bfd_error_system_call); |
| 359 | return sts; |
| 360 | } |
| 361 | |
| 362 | static const struct bfd_iovec cache_iovec = { |
| 363 | &cache_bread, &cache_bwrite, &cache_btell, &cache_bseek, |
| 364 | &cache_bclose, &cache_bflush, &cache_bstat |
| 365 | }; |
| 366 | |
| 367 | /* |
| 368 | INTERNAL_FUNCTION |
| 369 | bfd_cache_init |
| 370 | |
| 371 | SYNOPSIS |
| 372 | bfd_boolean bfd_cache_init (bfd *abfd); |
| 373 | |
| 374 | DESCRIPTION |
| 375 | Add a newly opened BFD to the cache. |
| 376 | */ |
| 377 | |
| 378 | bfd_boolean |
| 379 | bfd_cache_init (bfd *abfd) |
| 380 | { |
| 381 | BFD_ASSERT (abfd->iostream != NULL); |
| 382 | if (open_files >= BFD_CACHE_MAX_OPEN) |
| 383 | { |
| 384 | if (! close_one ()) |
| 385 | return FALSE; |
| 386 | } |
| 387 | abfd->iovec = &cache_iovec; |
| 388 | insert (abfd); |
| 389 | ++open_files; |
| 390 | return TRUE; |
| 391 | } |
| 392 | |
| 393 | /* |
| 394 | INTERNAL_FUNCTION |
| 395 | bfd_cache_close |
| 396 | |
| 397 | SYNOPSIS |
| 398 | bfd_boolean bfd_cache_close (bfd *abfd); |
| 399 | |
| 400 | DESCRIPTION |
| 401 | Remove the BFD @var{abfd} from the cache. If the attached file is open, |
| 402 | then close it too. |
| 403 | |
| 404 | RETURNS |
| 405 | <<FALSE>> is returned if closing the file fails, <<TRUE>> is |
| 406 | returned if all is well. |
| 407 | */ |
| 408 | |
| 409 | bfd_boolean |
| 410 | bfd_cache_close (bfd *abfd) |
| 411 | { |
| 412 | if (abfd->iovec != &cache_iovec) |
| 413 | return TRUE; |
| 414 | |
| 415 | if (abfd->iostream == NULL) |
| 416 | /* Previously closed. */ |
| 417 | return TRUE; |
| 418 | |
| 419 | return bfd_cache_delete (abfd); |
| 420 | } |
| 421 | |
| 422 | /* |
| 423 | FUNCTION |
| 424 | bfd_cache_close_all |
| 425 | |
| 426 | SYNOPSIS |
| 427 | bfd_boolean bfd_cache_close_all (void); |
| 428 | |
| 429 | DESCRIPTION |
| 430 | Remove all BFDs from the cache. If the attached file is open, |
| 431 | then close it too. |
| 432 | |
| 433 | RETURNS |
| 434 | <<FALSE>> is returned if closing one of the file fails, <<TRUE>> is |
| 435 | returned if all is well. |
| 436 | */ |
| 437 | |
| 438 | bfd_boolean |
| 439 | bfd_cache_close_all () |
| 440 | { |
| 441 | bfd_boolean ret = TRUE; |
| 442 | |
| 443 | while (bfd_last_cache != NULL) |
| 444 | ret &= bfd_cache_close (bfd_last_cache); |
| 445 | |
| 446 | return ret; |
| 447 | } |
| 448 | |
| 449 | /* |
| 450 | INTERNAL_FUNCTION |
| 451 | bfd_open_file |
| 452 | |
| 453 | SYNOPSIS |
| 454 | FILE* bfd_open_file (bfd *abfd); |
| 455 | |
| 456 | DESCRIPTION |
| 457 | Call the OS to open a file for @var{abfd}. Return the <<FILE *>> |
| 458 | (possibly <<NULL>>) that results from this operation. Set up the |
| 459 | BFD so that future accesses know the file is open. If the <<FILE *>> |
| 460 | returned is <<NULL>>, then it won't have been put in the |
| 461 | cache, so it won't have to be removed from it. |
| 462 | */ |
| 463 | |
| 464 | FILE * |
| 465 | bfd_open_file (bfd *abfd) |
| 466 | { |
| 467 | abfd->cacheable = TRUE; /* Allow it to be closed later. */ |
| 468 | |
| 469 | if (open_files >= BFD_CACHE_MAX_OPEN) |
| 470 | { |
| 471 | if (! close_one ()) |
| 472 | return NULL; |
| 473 | } |
| 474 | |
| 475 | switch (abfd->direction) |
| 476 | { |
| 477 | case read_direction: |
| 478 | case no_direction: |
| 479 | abfd->iostream = (PTR) real_fopen (abfd->filename, FOPEN_RB); |
| 480 | break; |
| 481 | case both_direction: |
| 482 | case write_direction: |
| 483 | if (abfd->opened_once) |
| 484 | { |
| 485 | abfd->iostream = (PTR) real_fopen (abfd->filename, FOPEN_RUB); |
| 486 | if (abfd->iostream == NULL) |
| 487 | abfd->iostream = (PTR) real_fopen (abfd->filename, FOPEN_WUB); |
| 488 | } |
| 489 | else |
| 490 | { |
| 491 | /* Create the file. |
| 492 | |
| 493 | Some operating systems won't let us overwrite a running |
| 494 | binary. For them, we want to unlink the file first. |
| 495 | |
| 496 | However, gcc 2.95 will create temporary files using |
| 497 | O_EXCL and tight permissions to prevent other users from |
| 498 | substituting other .o files during the compilation. gcc |
| 499 | will then tell the assembler to use the newly created |
| 500 | file as an output file. If we unlink the file here, we |
| 501 | open a brief window when another user could still |
| 502 | substitute a file. |
| 503 | |
| 504 | So we unlink the output file if and only if it has |
| 505 | non-zero size. */ |
| 506 | #ifndef __MSDOS__ |
| 507 | /* Don't do this for MSDOS: it doesn't care about overwriting |
| 508 | a running binary, but if this file is already open by |
| 509 | another BFD, we will be in deep trouble if we delete an |
| 510 | open file. In fact, objdump does just that if invoked with |
| 511 | the --info option. */ |
| 512 | struct stat s; |
| 513 | |
| 514 | if (stat (abfd->filename, &s) == 0 && s.st_size != 0) |
| 515 | unlink_if_ordinary (abfd->filename); |
| 516 | #endif |
| 517 | abfd->iostream = (PTR) real_fopen (abfd->filename, FOPEN_WUB); |
| 518 | abfd->opened_once = TRUE; |
| 519 | } |
| 520 | break; |
| 521 | } |
| 522 | |
| 523 | if (abfd->iostream == NULL) |
| 524 | bfd_set_error (bfd_error_system_call); |
| 525 | else |
| 526 | { |
| 527 | if (! bfd_cache_init (abfd)) |
| 528 | return NULL; |
| 529 | } |
| 530 | |
| 531 | return (FILE *) abfd->iostream; |
| 532 | } |