Properly check default linker.
[binutils.git] / bfd / cache.c
blob2239c28aac44f357b83e685e91e0605b79e785de
1 /* BFD library -- caching of file descriptors.
3 Copyright 1990, 1991, 1992, 1993, 1994, 1996, 2000, 2001, 2002,
4 2003, 2004, 2005, 2007, 2008, 2009 Free Software Foundation, Inc.
6 Hacked by Steve Chamberlain of Cygnus Support (steve@cygnus.com).
8 This file is part of BFD, the Binary File Descriptor library.
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 3 of the License, or
13 (at your option) any later version.
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.
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,
23 MA 02110-1301, USA. */
26 SECTION
27 File caching
29 The file caching mechanism is embedded within BFD and allows
30 the application to open as many BFDs as it wants without
31 regard to the underlying operating system's file descriptor
32 limit (often as low as 20 open files). The module in
33 <<cache.c>> maintains a least recently used list of
34 <<BFD_CACHE_MAX_OPEN>> files, and exports the name
35 <<bfd_cache_lookup>>, which runs around and makes sure that
36 the required BFD is open. If not, then it chooses a file to
37 close, closes it and opens the one wanted, returning its file
38 handle.
40 SUBSECTION
41 Caching functions
44 #include "sysdep.h"
45 #include "bfd.h"
46 #include "libbfd.h"
47 #include "libiberty.h"
49 #ifdef HAVE_MMAP
50 #include <sys/mman.h>
51 #endif
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
68 /* The maximum number of files which the cache will keep open at
69 one time. */
71 #define BFD_CACHE_MAX_OPEN 10
73 /* The number of BFD files we have open. */
75 static int open_files;
77 /* Zero, or a pointer to the topmost BFD on the chain. This is
78 used by the <<bfd_cache_lookup>> macro in @file{libbfd.h} to
79 determine when it can avoid a function call. */
81 static bfd *bfd_last_cache = NULL;
83 /* Insert a BFD into the cache. */
85 static void
86 insert (bfd *abfd)
88 if (bfd_last_cache == NULL)
90 abfd->lru_next = abfd;
91 abfd->lru_prev = abfd;
93 else
95 abfd->lru_next = bfd_last_cache;
96 abfd->lru_prev = bfd_last_cache->lru_prev;
97 abfd->lru_prev->lru_next = abfd;
98 abfd->lru_next->lru_prev = abfd;
100 bfd_last_cache = abfd;
103 /* Remove a BFD from the cache. */
105 static void
106 snip (bfd *abfd)
108 abfd->lru_prev->lru_next = abfd->lru_next;
109 abfd->lru_next->lru_prev = abfd->lru_prev;
110 if (abfd == bfd_last_cache)
112 bfd_last_cache = abfd->lru_next;
113 if (abfd == bfd_last_cache)
114 bfd_last_cache = NULL;
118 /* Close a BFD and remove it from the cache. */
120 static bfd_boolean
121 bfd_cache_delete (bfd *abfd)
123 bfd_boolean ret;
125 if (fclose ((FILE *) abfd->iostream) == 0)
126 ret = TRUE;
127 else
129 ret = FALSE;
130 bfd_set_error (bfd_error_system_call);
133 snip (abfd);
135 abfd->iostream = NULL;
136 --open_files;
138 return ret;
141 /* We need to open a new file, and the cache is full. Find the least
142 recently used cacheable BFD and close it. */
144 static bfd_boolean
145 close_one (void)
147 register bfd *to_kill;
149 if (bfd_last_cache == NULL)
150 to_kill = NULL;
151 else
153 for (to_kill = bfd_last_cache->lru_prev;
154 ! to_kill->cacheable;
155 to_kill = to_kill->lru_prev)
157 if (to_kill == bfd_last_cache)
159 to_kill = NULL;
160 break;
165 if (to_kill == NULL)
167 /* There are no open cacheable BFD's. */
168 return TRUE;
171 to_kill->where = real_ftell ((FILE *) to_kill->iostream);
173 return bfd_cache_delete (to_kill);
176 /* Check to see if the required BFD is the same as the last one
177 looked up. If so, then it can use the stream in the BFD with
178 impunity, since it can't have changed since the last lookup;
179 otherwise, it has to perform the complicated lookup function. */
181 #define bfd_cache_lookup(x, flag) \
182 ((x) == bfd_last_cache \
183 ? (FILE *) (bfd_last_cache->iostream) \
184 : bfd_cache_lookup_worker (x, flag))
186 /* Called when the macro <<bfd_cache_lookup>> fails to find a
187 quick answer. Find a file descriptor for @var{abfd}. If
188 necessary, it open it. If there are already more than
189 <<BFD_CACHE_MAX_OPEN>> files open, it tries to close one first, to
190 avoid running out of file descriptors. It will return NULL
191 if it is unable to (re)open the @var{abfd}. */
193 static FILE *
194 bfd_cache_lookup_worker (bfd *abfd, enum cache_flag flag)
196 bfd *orig_bfd = abfd;
197 if ((abfd->flags & BFD_IN_MEMORY) != 0)
198 abort ();
200 if (abfd->my_archive)
201 abfd = abfd->my_archive;
203 if (abfd->iostream != NULL)
205 /* Move the file to the start of the cache. */
206 if (abfd != bfd_last_cache)
208 snip (abfd);
209 insert (abfd);
211 return (FILE *) abfd->iostream;
214 if (flag & CACHE_NO_OPEN)
215 return NULL;
217 if (bfd_open_file (abfd) == NULL)
219 else if (!(flag & CACHE_NO_SEEK)
220 && real_fseek ((FILE *) abfd->iostream, abfd->where, SEEK_SET) != 0
221 && !(flag & CACHE_NO_SEEK_ERROR))
222 bfd_set_error (bfd_error_system_call);
223 else
224 return (FILE *) abfd->iostream;
226 (*_bfd_error_handler) (_("reopening %B: %s\n"),
227 orig_bfd, bfd_errmsg (bfd_get_error ()));
228 return NULL;
231 static file_ptr
232 cache_btell (struct bfd *abfd)
234 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN);
235 if (f == NULL)
236 return abfd->where;
237 return real_ftell (f);
240 static int
241 cache_bseek (struct bfd *abfd, file_ptr offset, int whence)
243 FILE *f = bfd_cache_lookup (abfd, whence != SEEK_CUR ? CACHE_NO_SEEK : CACHE_NORMAL);
244 if (f == NULL)
245 return -1;
246 return real_fseek (f, offset, whence);
249 /* Note that archive entries don't have streams; they share their parent's.
250 This allows someone to play with the iostream behind BFD's back.
252 Also, note that the origin pointer points to the beginning of a file's
253 contents (0 for non-archive elements). For archive entries this is the
254 first octet in the file, NOT the beginning of the archive header. */
256 static file_ptr
257 cache_bread_1 (struct bfd *abfd, void *buf, file_ptr nbytes)
259 FILE *f;
260 file_ptr nread;
261 /* FIXME - this looks like an optimization, but it's really to cover
262 up for a feature of some OSs (not solaris - sigh) that
263 ld/pe-dll.c takes advantage of (apparently) when it creates BFDs
264 internally and tries to link against them. BFD seems to be smart
265 enough to realize there are no symbol records in the "file" that
266 doesn't exist but attempts to read them anyway. On Solaris,
267 attempting to read zero bytes from a NULL file results in a core
268 dump, but on other platforms it just returns zero bytes read.
269 This makes it to something reasonable. - DJ */
270 if (nbytes == 0)
271 return 0;
273 f = bfd_cache_lookup (abfd, CACHE_NORMAL);
274 if (f == NULL)
275 return 0;
277 #if defined (__VAX) && defined (VMS)
278 /* Apparently fread on Vax VMS does not keep the record length
279 information. */
280 nread = read (fileno (f), buf, nbytes);
281 /* Set bfd_error if we did not read as much data as we expected. If
282 the read failed due to an error set the bfd_error_system_call,
283 else set bfd_error_file_truncated. */
284 if (nread == (file_ptr)-1)
286 bfd_set_error (bfd_error_system_call);
287 return -1;
289 #else
290 nread = fread (buf, 1, nbytes, f);
291 /* Set bfd_error if we did not read as much data as we expected. If
292 the read failed due to an error set the bfd_error_system_call,
293 else set bfd_error_file_truncated. */
294 if (nread < nbytes && ferror (f))
296 bfd_set_error (bfd_error_system_call);
297 return -1;
299 #endif
300 if (nread < nbytes)
301 /* This may or may not be an error, but in case the calling code
302 bails out because of it, set the right error code. */
303 bfd_set_error (bfd_error_file_truncated);
304 return nread;
307 static file_ptr
308 cache_bread (struct bfd *abfd, void *buf, file_ptr nbytes)
310 file_ptr nread = 0;
312 /* Some filesystems are unable to handle reads that are too large
313 (for instance, NetApp shares with oplocks turned off). To avoid
314 hitting this limitation, we read the buffer in chunks of 8MB max. */
315 while (nread < nbytes)
317 const file_ptr max_chunk_size = 0x800000;
318 file_ptr chunk_size = nbytes - nread;
319 file_ptr chunk_nread;
321 if (chunk_size > max_chunk_size)
322 chunk_size = max_chunk_size;
324 chunk_nread = cache_bread_1 (abfd, (char *) buf + nread, chunk_size);
326 /* Update the nread count.
328 We just have to be careful of the case when cache_bread_1 returns
329 a negative count: If this is our first read, then set nread to
330 that negative count in order to return that negative value to the
331 caller. Otherwise, don't add it to our total count, or we would
332 end up returning a smaller number of bytes read than we actually
333 did. */
334 if (nread == 0 || chunk_nread > 0)
335 nread += chunk_nread;
337 if (chunk_nread < chunk_size)
338 break;
341 return nread;
344 static file_ptr
345 cache_bwrite (struct bfd *abfd, const void *where, file_ptr nbytes)
347 file_ptr nwrite;
348 FILE *f = bfd_cache_lookup (abfd, CACHE_NORMAL);
350 if (f == NULL)
351 return 0;
352 nwrite = fwrite (where, 1, nbytes, f);
353 if (nwrite < nbytes && ferror (f))
355 bfd_set_error (bfd_error_system_call);
356 return -1;
358 return nwrite;
361 static int
362 cache_bclose (struct bfd *abfd)
364 return bfd_cache_close (abfd);
367 static int
368 cache_bflush (struct bfd *abfd)
370 int sts;
371 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN);
373 if (f == NULL)
374 return 0;
375 sts = fflush (f);
376 if (sts < 0)
377 bfd_set_error (bfd_error_system_call);
378 return sts;
381 static int
382 cache_bstat (struct bfd *abfd, struct stat *sb)
384 int sts;
385 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR);
387 if (f == NULL)
388 return -1;
389 sts = fstat (fileno (f), sb);
390 if (sts < 0)
391 bfd_set_error (bfd_error_system_call);
392 return sts;
395 static void *
396 cache_bmmap (struct bfd *abfd ATTRIBUTE_UNUSED,
397 void *addr ATTRIBUTE_UNUSED,
398 bfd_size_type len ATTRIBUTE_UNUSED,
399 int prot ATTRIBUTE_UNUSED,
400 int flags ATTRIBUTE_UNUSED,
401 file_ptr offset ATTRIBUTE_UNUSED)
403 void *ret = (void *) -1;
405 if ((abfd->flags & BFD_IN_MEMORY) != 0)
406 abort ();
407 #ifdef HAVE_MMAP
408 else
410 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR);
411 if (f == NULL)
412 return ret;
414 ret = mmap (addr, len, prot, flags, fileno (f), offset);
415 if (ret == (void *) -1)
416 bfd_set_error (bfd_error_system_call);
418 #endif
420 return ret;
423 static const struct bfd_iovec cache_iovec =
425 &cache_bread, &cache_bwrite, &cache_btell, &cache_bseek,
426 &cache_bclose, &cache_bflush, &cache_bstat, &cache_bmmap
430 INTERNAL_FUNCTION
431 bfd_cache_init
433 SYNOPSIS
434 bfd_boolean bfd_cache_init (bfd *abfd);
436 DESCRIPTION
437 Add a newly opened BFD to the cache.
440 bfd_boolean
441 bfd_cache_init (bfd *abfd)
443 BFD_ASSERT (abfd->iostream != NULL);
444 if (open_files >= BFD_CACHE_MAX_OPEN)
446 if (! close_one ())
447 return FALSE;
449 abfd->iovec = &cache_iovec;
450 insert (abfd);
451 ++open_files;
452 return TRUE;
456 INTERNAL_FUNCTION
457 bfd_cache_close
459 SYNOPSIS
460 bfd_boolean bfd_cache_close (bfd *abfd);
462 DESCRIPTION
463 Remove the BFD @var{abfd} from the cache. If the attached file is open,
464 then close it too.
466 RETURNS
467 <<FALSE>> is returned if closing the file fails, <<TRUE>> is
468 returned if all is well.
471 bfd_boolean
472 bfd_cache_close (bfd *abfd)
474 if (abfd->iovec != &cache_iovec)
475 return TRUE;
477 if (abfd->iostream == NULL)
478 /* Previously closed. */
479 return TRUE;
481 return bfd_cache_delete (abfd);
485 FUNCTION
486 bfd_cache_close_all
488 SYNOPSIS
489 bfd_boolean bfd_cache_close_all (void);
491 DESCRIPTION
492 Remove all BFDs from the cache. If the attached file is open,
493 then close it too.
495 RETURNS
496 <<FALSE>> is returned if closing one of the file fails, <<TRUE>> is
497 returned if all is well.
500 bfd_boolean
501 bfd_cache_close_all ()
503 bfd_boolean ret = TRUE;
505 while (bfd_last_cache != NULL)
506 ret &= bfd_cache_close (bfd_last_cache);
508 return ret;
512 INTERNAL_FUNCTION
513 bfd_open_file
515 SYNOPSIS
516 FILE* bfd_open_file (bfd *abfd);
518 DESCRIPTION
519 Call the OS to open a file for @var{abfd}. Return the <<FILE *>>
520 (possibly <<NULL>>) that results from this operation. Set up the
521 BFD so that future accesses know the file is open. If the <<FILE *>>
522 returned is <<NULL>>, then it won't have been put in the
523 cache, so it won't have to be removed from it.
526 FILE *
527 bfd_open_file (bfd *abfd)
529 abfd->cacheable = TRUE; /* Allow it to be closed later. */
531 if (open_files >= BFD_CACHE_MAX_OPEN)
533 if (! close_one ())
534 return NULL;
537 switch (abfd->direction)
539 case read_direction:
540 case no_direction:
541 abfd->iostream = (PTR) real_fopen (abfd->filename, FOPEN_RB);
542 break;
543 case both_direction:
544 case write_direction:
545 if (abfd->opened_once)
547 abfd->iostream = (PTR) real_fopen (abfd->filename, FOPEN_RUB);
548 if (abfd->iostream == NULL)
549 abfd->iostream = (PTR) real_fopen (abfd->filename, FOPEN_WUB);
551 else
553 /* Create the file.
555 Some operating systems won't let us overwrite a running
556 binary. For them, we want to unlink the file first.
558 However, gcc 2.95 will create temporary files using
559 O_EXCL and tight permissions to prevent other users from
560 substituting other .o files during the compilation. gcc
561 will then tell the assembler to use the newly created
562 file as an output file. If we unlink the file here, we
563 open a brief window when another user could still
564 substitute a file.
566 So we unlink the output file if and only if it has
567 non-zero size. */
568 #ifndef __MSDOS__
569 /* Don't do this for MSDOS: it doesn't care about overwriting
570 a running binary, but if this file is already open by
571 another BFD, we will be in deep trouble if we delete an
572 open file. In fact, objdump does just that if invoked with
573 the --info option. */
574 struct stat s;
576 if (stat (abfd->filename, &s) == 0 && s.st_size != 0)
577 unlink_if_ordinary (abfd->filename);
578 #endif
579 abfd->iostream = (PTR) real_fopen (abfd->filename, FOPEN_WUB);
580 abfd->opened_once = TRUE;
582 break;
585 if (abfd->iostream == NULL)
586 bfd_set_error (bfd_error_system_call);
587 else
589 if (! bfd_cache_init (abfd))
590 return NULL;
593 return (FILE *) abfd->iostream;