1 /* BFD library -- caching of file descriptors.
2
3 Copyright (C) 1990-2014 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 /*
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
bfd_cache_max_open(void)76 bfd_cache_max_open (void)
77 {
78 if (max_open_files == 0)
79 {
80 int max;
81 #ifdef HAVE_GETRLIMIT
82 struct rlimit rlim;
83 if (getrlimit (RLIMIT_NOFILE, &rlim) == 0
84 && rlim.rlim_cur != (rlim_t) RLIM_INFINITY)
85 max = rlim.rlim_cur / 8;
86 else
87 #endif /* HAVE_GETRLIMIT */
88 #ifdef _SC_OPEN_MAX
89 max = sysconf (_SC_OPEN_MAX) / 8;
90 #else
91 max = 10;
92 #endif /* _SC_OPEN_MAX */
93 max_open_files = max < 10 ? 10 : max;
94 }
95
96 return max_open_files;
97 }
98
99 /* The number of BFD files we have open. */
100
101 static int open_files;
102
103 /* Zero, or a pointer to the topmost BFD on the chain. This is
104 used by the <<bfd_cache_lookup>> macro in @file{libbfd.h} to
105 determine when it can avoid a function call. */
106
107 static bfd *bfd_last_cache = NULL;
108
109 /* Insert a BFD into the cache. */
110
111 static void
insert(bfd * abfd)112 insert (bfd *abfd)
113 {
114 if (bfd_last_cache == NULL)
115 {
116 abfd->lru_next = abfd;
117 abfd->lru_prev = abfd;
118 }
119 else
120 {
121 abfd->lru_next = bfd_last_cache;
122 abfd->lru_prev = bfd_last_cache->lru_prev;
123 abfd->lru_prev->lru_next = abfd;
124 abfd->lru_next->lru_prev = abfd;
125 }
126 bfd_last_cache = abfd;
127 }
128
129 /* Remove a BFD from the cache. */
130
131 static void
snip(bfd * abfd)132 snip (bfd *abfd)
133 {
134 abfd->lru_prev->lru_next = abfd->lru_next;
135 abfd->lru_next->lru_prev = abfd->lru_prev;
136 if (abfd == bfd_last_cache)
137 {
138 bfd_last_cache = abfd->lru_next;
139 if (abfd == bfd_last_cache)
140 bfd_last_cache = NULL;
141 }
142 }
143
144 /* Close a BFD and remove it from the cache. */
145
146 static bfd_boolean
bfd_cache_delete(bfd * abfd)147 bfd_cache_delete (bfd *abfd)
148 {
149 bfd_boolean ret;
150
151 if (fclose ((FILE *) abfd->iostream) == 0)
152 ret = TRUE;
153 else
154 {
155 ret = FALSE;
156 bfd_set_error (bfd_error_system_call);
157 }
158
159 snip (abfd);
160
161 abfd->iostream = NULL;
162 --open_files;
163
164 return ret;
165 }
166
167 /* We need to open a new file, and the cache is full. Find the least
168 recently used cacheable BFD and close it. */
169
170 static bfd_boolean
close_one(void)171 close_one (void)
172 {
173 register bfd *to_kill;
174
175 if (bfd_last_cache == NULL)
176 to_kill = NULL;
177 else
178 {
179 for (to_kill = bfd_last_cache->lru_prev;
180 ! to_kill->cacheable;
181 to_kill = to_kill->lru_prev)
182 {
183 if (to_kill == bfd_last_cache)
184 {
185 to_kill = NULL;
186 break;
187 }
188 }
189 }
190
191 if (to_kill == NULL)
192 {
193 /* There are no open cacheable BFD's. */
194 return TRUE;
195 }
196
197 to_kill->where = real_ftell ((FILE *) to_kill->iostream);
198
199 return bfd_cache_delete (to_kill);
200 }
201
202 /* Check to see if the required BFD is the same as the last one
203 looked up. If so, then it can use the stream in the BFD with
204 impunity, since it can't have changed since the last lookup;
205 otherwise, it has to perform the complicated lookup function. */
206
207 #define bfd_cache_lookup(x, flag) \
208 ((x) == bfd_last_cache \
209 ? (FILE *) (bfd_last_cache->iostream) \
210 : bfd_cache_lookup_worker (x, flag))
211
212 /* Called when the macro <<bfd_cache_lookup>> fails to find a
213 quick answer. Find a file descriptor for @var{abfd}. If
214 necessary, it open it. If there are already more than
215 <<bfd_cache_max_open>> files open, it tries to close one first, to
216 avoid running out of file descriptors. It will return NULL
217 if it is unable to (re)open the @var{abfd}. */
218
219 static FILE *
bfd_cache_lookup_worker(bfd * abfd,enum cache_flag flag)220 bfd_cache_lookup_worker (bfd *abfd, enum cache_flag flag)
221 {
222 bfd *orig_bfd = abfd;
223 if ((abfd->flags & BFD_IN_MEMORY) != 0)
224 abort ();
225
226 while (abfd->my_archive)
227 abfd = abfd->my_archive;
228
229 if (abfd->iostream != NULL)
230 {
231 /* Move the file to the start of the cache. */
232 if (abfd != bfd_last_cache)
233 {
234 snip (abfd);
235 insert (abfd);
236 }
237 return (FILE *) abfd->iostream;
238 }
239
240 if (flag & CACHE_NO_OPEN)
241 return NULL;
242
243 if (bfd_open_file (abfd) == NULL)
244 ;
245 else if (!(flag & CACHE_NO_SEEK)
246 && real_fseek ((FILE *) abfd->iostream, abfd->where, SEEK_SET) != 0
247 && !(flag & CACHE_NO_SEEK_ERROR))
248 bfd_set_error (bfd_error_system_call);
249 else
250 return (FILE *) abfd->iostream;
251
252 (*_bfd_error_handler) (_("reopening %B: %s\n"),
253 orig_bfd, bfd_errmsg (bfd_get_error ()));
254 return NULL;
255 }
256
257 static file_ptr
cache_btell(struct bfd * abfd)258 cache_btell (struct bfd *abfd)
259 {
260 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN);
261 if (f == NULL)
262 return abfd->where;
263 return real_ftell (f);
264 }
265
266 static int
cache_bseek(struct bfd * abfd,file_ptr offset,int whence)267 cache_bseek (struct bfd *abfd, file_ptr offset, int whence)
268 {
269 FILE *f = bfd_cache_lookup (abfd, whence != SEEK_CUR ? CACHE_NO_SEEK : CACHE_NORMAL);
270 if (f == NULL)
271 return -1;
272 return real_fseek (f, offset, whence);
273 }
274
275 /* Note that archive entries don't have streams; they share their parent's.
276 This allows someone to play with the iostream behind BFD's back.
277
278 Also, note that the origin pointer points to the beginning of a file's
279 contents (0 for non-archive elements). For archive entries this is the
280 first octet in the file, NOT the beginning of the archive header. */
281
282 static file_ptr
cache_bread_1(struct bfd * abfd,void * buf,file_ptr nbytes)283 cache_bread_1 (struct bfd *abfd, void *buf, file_ptr nbytes)
284 {
285 FILE *f;
286 file_ptr nread;
287 /* FIXME - this looks like an optimization, but it's really to cover
288 up for a feature of some OSs (not solaris - sigh) that
289 ld/pe-dll.c takes advantage of (apparently) when it creates BFDs
290 internally and tries to link against them. BFD seems to be smart
291 enough to realize there are no symbol records in the "file" that
292 doesn't exist but attempts to read them anyway. On Solaris,
293 attempting to read zero bytes from a NULL file results in a core
294 dump, but on other platforms it just returns zero bytes read.
295 This makes it to something reasonable. - DJ */
296 if (nbytes == 0)
297 return 0;
298
299 f = bfd_cache_lookup (abfd, CACHE_NORMAL);
300 if (f == NULL)
301 return 0;
302
303 #if defined (__VAX) && defined (VMS)
304 /* Apparently fread on Vax VMS does not keep the record length
305 information. */
306 nread = read (fileno (f), buf, nbytes);
307 /* Set bfd_error if we did not read as much data as we expected. If
308 the read failed due to an error set the bfd_error_system_call,
309 else set bfd_error_file_truncated. */
310 if (nread == (file_ptr)-1)
311 {
312 bfd_set_error (bfd_error_system_call);
313 return nread;
314 }
315 #else
316 nread = fread (buf, 1, nbytes, f);
317 /* Set bfd_error if we did not read as much data as we expected. If
318 the read failed due to an error set the bfd_error_system_call,
319 else set bfd_error_file_truncated. */
320 if (nread < nbytes && ferror (f))
321 {
322 bfd_set_error (bfd_error_system_call);
323 return nread;
324 }
325 #endif
326 if (nread < nbytes)
327 /* This may or may not be an error, but in case the calling code
328 bails out because of it, set the right error code. */
329 bfd_set_error (bfd_error_file_truncated);
330 return nread;
331 }
332
333 static file_ptr
cache_bread(struct bfd * abfd,void * buf,file_ptr nbytes)334 cache_bread (struct bfd *abfd, void *buf, file_ptr nbytes)
335 {
336 file_ptr nread = 0;
337
338 /* Some filesystems are unable to handle reads that are too large
339 (for instance, NetApp shares with oplocks turned off). To avoid
340 hitting this limitation, we read the buffer in chunks of 8MB max. */
341 while (nread < nbytes)
342 {
343 const file_ptr max_chunk_size = 0x800000;
344 file_ptr chunk_size = nbytes - nread;
345 file_ptr chunk_nread;
346
347 if (chunk_size > max_chunk_size)
348 chunk_size = max_chunk_size;
349
350 chunk_nread = cache_bread_1 (abfd, (char *) buf + nread, chunk_size);
351
352 /* Update the nread count.
353
354 We just have to be careful of the case when cache_bread_1 returns
355 a negative count: If this is our first read, then set nread to
356 that negative count in order to return that negative value to the
357 caller. Otherwise, don't add it to our total count, or we would
358 end up returning a smaller number of bytes read than we actually
359 did. */
360 if (nread == 0 || chunk_nread > 0)
361 nread += chunk_nread;
362
363 if (chunk_nread < chunk_size)
364 break;
365 }
366
367 return nread;
368 }
369
370 static file_ptr
cache_bwrite(struct bfd * abfd,const void * where,file_ptr nbytes)371 cache_bwrite (struct bfd *abfd, const void *where, file_ptr nbytes)
372 {
373 file_ptr nwrite;
374 FILE *f = bfd_cache_lookup (abfd, CACHE_NORMAL);
375
376 if (f == NULL)
377 return 0;
378 nwrite = fwrite (where, 1, nbytes, f);
379 if (nwrite < nbytes && ferror (f))
380 {
381 bfd_set_error (bfd_error_system_call);
382 return -1;
383 }
384 return nwrite;
385 }
386
387 static int
cache_bclose(struct bfd * abfd)388 cache_bclose (struct bfd *abfd)
389 {
390 return bfd_cache_close (abfd) - 1;
391 }
392
393 static int
cache_bflush(struct bfd * abfd)394 cache_bflush (struct bfd *abfd)
395 {
396 int sts;
397 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN);
398
399 if (f == NULL)
400 return 0;
401 sts = fflush (f);
402 if (sts < 0)
403 bfd_set_error (bfd_error_system_call);
404 return sts;
405 }
406
407 static int
cache_bstat(struct bfd * abfd,struct stat * sb)408 cache_bstat (struct bfd *abfd, struct stat *sb)
409 {
410 int sts;
411 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR);
412
413 if (f == NULL)
414 return -1;
415 sts = fstat (fileno (f), sb);
416 if (sts < 0)
417 bfd_set_error (bfd_error_system_call);
418 return sts;
419 }
420
421 static void *
cache_bmmap(struct bfd * abfd ATTRIBUTE_UNUSED,void * addr ATTRIBUTE_UNUSED,bfd_size_type len ATTRIBUTE_UNUSED,int prot ATTRIBUTE_UNUSED,int flags ATTRIBUTE_UNUSED,file_ptr offset ATTRIBUTE_UNUSED,void ** map_addr ATTRIBUTE_UNUSED,bfd_size_type * map_len ATTRIBUTE_UNUSED)422 cache_bmmap (struct bfd *abfd ATTRIBUTE_UNUSED,
423 void *addr ATTRIBUTE_UNUSED,
424 bfd_size_type len ATTRIBUTE_UNUSED,
425 int prot ATTRIBUTE_UNUSED,
426 int flags ATTRIBUTE_UNUSED,
427 file_ptr offset ATTRIBUTE_UNUSED,
428 void **map_addr ATTRIBUTE_UNUSED,
429 bfd_size_type *map_len ATTRIBUTE_UNUSED)
430 {
431 void *ret = (void *) -1;
432
433 if ((abfd->flags & BFD_IN_MEMORY) != 0)
434 abort ();
435 #ifdef HAVE_MMAP
436 else
437 {
438 static uintptr_t pagesize_m1;
439 FILE *f;
440 file_ptr pg_offset;
441 bfd_size_type pg_len;
442
443 f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR);
444 if (f == NULL)
445 return ret;
446
447 if (pagesize_m1 == 0)
448 pagesize_m1 = getpagesize () - 1;
449
450 /* Handle archive members. */
451 if (abfd->my_archive != NULL)
452 offset += abfd->origin;
453
454 /* Align. */
455 pg_offset = offset & ~pagesize_m1;
456 pg_len = (len + (offset - pg_offset) + pagesize_m1) & ~pagesize_m1;
457
458 ret = mmap (addr, pg_len, prot, flags, fileno (f), pg_offset);
459 if (ret == (void *) -1)
460 bfd_set_error (bfd_error_system_call);
461 else
462 {
463 *map_addr = ret;
464 *map_len = pg_len;
465 ret = (char *) ret + (offset & pagesize_m1);
466 }
467 }
468 #endif
469
470 return ret;
471 }
472
473 static const struct bfd_iovec cache_iovec =
474 {
475 &cache_bread, &cache_bwrite, &cache_btell, &cache_bseek,
476 &cache_bclose, &cache_bflush, &cache_bstat, &cache_bmmap
477 };
478
479 /*
480 INTERNAL_FUNCTION
481 bfd_cache_init
482
483 SYNOPSIS
484 bfd_boolean bfd_cache_init (bfd *abfd);
485
486 DESCRIPTION
487 Add a newly opened BFD to the cache.
488 */
489
490 bfd_boolean
bfd_cache_init(bfd * abfd)491 bfd_cache_init (bfd *abfd)
492 {
493 BFD_ASSERT (abfd->iostream != NULL);
494 if (open_files >= bfd_cache_max_open ())
495 {
496 if (! close_one ())
497 return FALSE;
498 }
499 abfd->iovec = &cache_iovec;
500 insert (abfd);
501 ++open_files;
502 return TRUE;
503 }
504
505 /*
506 INTERNAL_FUNCTION
507 bfd_cache_close
508
509 SYNOPSIS
510 bfd_boolean bfd_cache_close (bfd *abfd);
511
512 DESCRIPTION
513 Remove the BFD @var{abfd} from the cache. If the attached file is open,
514 then close it too.
515
516 RETURNS
517 <<FALSE>> is returned if closing the file fails, <<TRUE>> is
518 returned if all is well.
519 */
520
521 bfd_boolean
bfd_cache_close(bfd * abfd)522 bfd_cache_close (bfd *abfd)
523 {
524 if (abfd->iovec != &cache_iovec)
525 return TRUE;
526
527 if (abfd->iostream == NULL)
528 /* Previously closed. */
529 return TRUE;
530
531 return bfd_cache_delete (abfd);
532 }
533
534 /*
535 FUNCTION
536 bfd_cache_close_all
537
538 SYNOPSIS
539 bfd_boolean bfd_cache_close_all (void);
540
541 DESCRIPTION
542 Remove all BFDs from the cache. If the attached file is open,
543 then close it too.
544
545 RETURNS
546 <<FALSE>> is returned if closing one of the file fails, <<TRUE>> is
547 returned if all is well.
548 */
549
550 bfd_boolean
bfd_cache_close_all()551 bfd_cache_close_all ()
552 {
553 bfd_boolean ret = TRUE;
554
555 while (bfd_last_cache != NULL)
556 ret &= bfd_cache_close (bfd_last_cache);
557
558 return ret;
559 }
560
561 /*
562 INTERNAL_FUNCTION
563 bfd_open_file
564
565 SYNOPSIS
566 FILE* bfd_open_file (bfd *abfd);
567
568 DESCRIPTION
569 Call the OS to open a file for @var{abfd}. Return the <<FILE *>>
570 (possibly <<NULL>>) that results from this operation. Set up the
571 BFD so that future accesses know the file is open. If the <<FILE *>>
572 returned is <<NULL>>, then it won't have been put in the
573 cache, so it won't have to be removed from it.
574 */
575
576 FILE *
bfd_open_file(bfd * abfd)577 bfd_open_file (bfd *abfd)
578 {
579 abfd->cacheable = TRUE; /* Allow it to be closed later. */
580
581 if (open_files >= bfd_cache_max_open ())
582 {
583 if (! close_one ())
584 return NULL;
585 }
586
587 switch (abfd->direction)
588 {
589 case read_direction:
590 case no_direction:
591 abfd->iostream = real_fopen (abfd->filename, FOPEN_RB);
592 break;
593 case both_direction:
594 case write_direction:
595 if (abfd->opened_once)
596 {
597 abfd->iostream = real_fopen (abfd->filename, FOPEN_RUB);
598 if (abfd->iostream == NULL)
599 abfd->iostream = real_fopen (abfd->filename, FOPEN_WUB);
600 }
601 else
602 {
603 /* Create the file.
604
605 Some operating systems won't let us overwrite a running
606 binary. For them, we want to unlink the file first.
607
608 However, gcc 2.95 will create temporary files using
609 O_EXCL and tight permissions to prevent other users from
610 substituting other .o files during the compilation. gcc
611 will then tell the assembler to use the newly created
612 file as an output file. If we unlink the file here, we
613 open a brief window when another user could still
614 substitute a file.
615
616 So we unlink the output file if and only if it has
617 non-zero size. */
618 #ifndef __MSDOS__
619 /* Don't do this for MSDOS: it doesn't care about overwriting
620 a running binary, but if this file is already open by
621 another BFD, we will be in deep trouble if we delete an
622 open file. In fact, objdump does just that if invoked with
623 the --info option. */
624 struct stat s;
625
626 if (stat (abfd->filename, &s) == 0 && s.st_size != 0)
627 unlink_if_ordinary (abfd->filename);
628 #endif
629 abfd->iostream = real_fopen (abfd->filename, FOPEN_WUB);
630 abfd->opened_once = TRUE;
631 }
632 break;
633 }
634
635 if (abfd->iostream == NULL)
636 bfd_set_error (bfd_error_system_call);
637 else
638 {
639 if (! bfd_cache_init (abfd))
640 return NULL;
641 }
642
643 return (FILE *) abfd->iostream;
644 }
645