1 /* BFD library -- caching of file descriptors.
2
3 Copyright (C) 1990-2023 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
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. */
60 enum 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
70 static 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. */
74 static int
75 bfd_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
118 static 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
124 static bfd *bfd_last_cache = NULL;
125
126 /* Insert a BFD into the cache. */
127
128 static void
129 insert (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
148 static void
149 snip (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
163 static bool
164 bfd_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
188 static bool
189 close_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
237 static FILE *
238 bfd_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 return (FILE *) abfd->iostream;
270
271 /* xgettext:c-format */
272 _bfd_error_handler (_("reopening %pB: %s"),
273 abfd, bfd_errmsg (bfd_get_error ()));
274 return NULL;
275 }
276
277 static file_ptr
278 cache_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 _bfd_real_ftell (f);
284 }
285
286 static int
287 cache_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 _bfd_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
302 static file_ptr
303 cache_bread_1 (FILE *f, void *buf, file_ptr nbytes)
304 {
305 file_ptr nread;
306
307 #if defined (__VAX) && defined (VMS)
308 /* Apparently fread on Vax VMS does not keep the record length
309 information. */
310 nread = read (fileno (f), buf, nbytes);
311 /* Set bfd_error if we did not read as much data as we expected. If
312 the read failed due to an error set the bfd_error_system_call,
313 else set bfd_error_file_truncated. */
314 if (nread == (file_ptr)-1)
315 {
316 bfd_set_error (bfd_error_system_call);
317 return nread;
318 }
319 #else
320 nread = fread (buf, 1, nbytes, f);
321 /* Set bfd_error if we did not read as much data as we expected. If
322 the read failed due to an error set the bfd_error_system_call,
323 else set bfd_error_file_truncated. */
324 if (nread < nbytes && ferror (f))
325 {
326 bfd_set_error (bfd_error_system_call);
327 return nread;
328 }
329 #endif
330 if (nread < nbytes)
331 /* This may or may not be an error, but in case the calling code
332 bails out because of it, set the right error code. */
333 bfd_set_error (bfd_error_file_truncated);
334 return nread;
335 }
336
337 static file_ptr
338 cache_bread (struct bfd *abfd, void *buf, file_ptr nbytes)
339 {
340 file_ptr nread = 0;
341 FILE *f;
342
343 f = bfd_cache_lookup (abfd, CACHE_NORMAL);
344 if (f == NULL)
345 return -1;
346
347 /* Some filesystems are unable to handle reads that are too large
348 (for instance, NetApp shares with oplocks turned off). To avoid
349 hitting this limitation, we read the buffer in chunks of 8MB max. */
350 while (nread < nbytes)
351 {
352 const file_ptr max_chunk_size = 0x800000;
353 file_ptr chunk_size = nbytes - nread;
354 file_ptr chunk_nread;
355
356 if (chunk_size > max_chunk_size)
357 chunk_size = max_chunk_size;
358
359 chunk_nread = cache_bread_1 (f, (char *) buf + nread, chunk_size);
360
361 /* Update the nread count.
362
363 We just have to be careful of the case when cache_bread_1 returns
364 a negative count: If this is our first read, then set nread to
365 that negative count in order to return that negative value to the
366 caller. Otherwise, don't add it to our total count, or we would
367 end up returning a smaller number of bytes read than we actually
368 did. */
369 if (nread == 0 || chunk_nread > 0)
370 nread += chunk_nread;
371
372 if (chunk_nread < chunk_size)
373 break;
374 }
375
376 return nread;
377 }
378
379 static file_ptr
380 cache_bwrite (struct bfd *abfd, const void *from, file_ptr nbytes)
381 {
382 file_ptr nwrite;
383 FILE *f = bfd_cache_lookup (abfd, CACHE_NORMAL);
384
385 if (f == NULL)
386 return 0;
387 nwrite = fwrite (from, 1, nbytes, f);
388 if (nwrite < nbytes && ferror (f))
389 {
390 bfd_set_error (bfd_error_system_call);
391 return -1;
392 }
393 return nwrite;
394 }
395
396 static int
397 cache_bclose (struct bfd *abfd)
398 {
399 return bfd_cache_close (abfd) - 1;
400 }
401
402 static int
403 cache_bflush (struct bfd *abfd)
404 {
405 int sts;
406 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN);
407
408 if (f == NULL)
409 return 0;
410 sts = fflush (f);
411 if (sts < 0)
412 bfd_set_error (bfd_error_system_call);
413 return sts;
414 }
415
416 static int
417 cache_bstat (struct bfd *abfd, struct stat *sb)
418 {
419 int sts;
420 FILE *f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR);
421
422 if (f == NULL)
423 return -1;
424 sts = fstat (fileno (f), sb);
425 if (sts < 0)
426 bfd_set_error (bfd_error_system_call);
427 return sts;
428 }
429
430 static void *
431 cache_bmmap (struct bfd *abfd ATTRIBUTE_UNUSED,
432 void *addr ATTRIBUTE_UNUSED,
433 bfd_size_type len ATTRIBUTE_UNUSED,
434 int prot ATTRIBUTE_UNUSED,
435 int flags ATTRIBUTE_UNUSED,
436 file_ptr offset ATTRIBUTE_UNUSED,
437 void **map_addr ATTRIBUTE_UNUSED,
438 bfd_size_type *map_len ATTRIBUTE_UNUSED)
439 {
440 void *ret = (void *) -1;
441
442 if ((abfd->flags & BFD_IN_MEMORY) != 0)
443 abort ();
444 #ifdef HAVE_MMAP
445 else
446 {
447 static uintptr_t pagesize_m1;
448 FILE *f;
449 file_ptr pg_offset;
450 bfd_size_type pg_len;
451
452 f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR);
453 if (f == NULL)
454 return ret;
455
456 if (pagesize_m1 == 0)
457 pagesize_m1 = getpagesize () - 1;
458
459 /* Align. */
460 pg_offset = offset & ~pagesize_m1;
461 pg_len = (len + (offset - pg_offset) + pagesize_m1) & ~pagesize_m1;
462
463 ret = mmap (addr, pg_len, prot, flags, fileno (f), pg_offset);
464 if (ret == (void *) -1)
465 bfd_set_error (bfd_error_system_call);
466 else
467 {
468 *map_addr = ret;
469 *map_len = pg_len;
470 ret = (char *) ret + (offset & pagesize_m1);
471 }
472 }
473 #endif
474
475 return ret;
476 }
477
478 static const struct bfd_iovec cache_iovec =
479 {
480 &cache_bread, &cache_bwrite, &cache_btell, &cache_bseek,
481 &cache_bclose, &cache_bflush, &cache_bstat, &cache_bmmap
482 };
483
484 /*
485 INTERNAL_FUNCTION
486 bfd_cache_init
487
488 SYNOPSIS
489 bool bfd_cache_init (bfd *abfd);
490
491 DESCRIPTION
492 Add a newly opened BFD to the cache.
493 */
494
495 bool
496 bfd_cache_init (bfd *abfd)
497 {
498 BFD_ASSERT (abfd->iostream != NULL);
499 if (open_files >= bfd_cache_max_open ())
500 {
501 if (! close_one ())
502 return false;
503 }
504 abfd->iovec = &cache_iovec;
505 insert (abfd);
506 abfd->flags &= ~BFD_CLOSED_BY_CACHE;
507 ++open_files;
508 return true;
509 }
510
511 /*
512 FUNCTION
513 bfd_cache_close
514
515 SYNOPSIS
516 bool bfd_cache_close (bfd *abfd);
517
518 DESCRIPTION
519 Remove the BFD @var{abfd} from the cache. If the attached file is open,
520 then close it too.
521
522 <<FALSE>> is returned if closing the file fails, <<TRUE>> is
523 returned if all is well.
524 */
525
526 bool
527 bfd_cache_close (bfd *abfd)
528 {
529 /* Don't remove this test. bfd_reinit depends on it. */
530 if (abfd->iovec != &cache_iovec)
531 return true;
532
533 if (abfd->iostream == NULL)
534 /* Previously closed. */
535 return true;
536
537 return bfd_cache_delete (abfd);
538 }
539
540 /*
541 FUNCTION
542 bfd_cache_close_all
543
544 SYNOPSIS
545 bool bfd_cache_close_all (void);
546
547 DESCRIPTION
548 Remove all BFDs from the cache. If the attached file is open,
549 then close it too.
550
551 <<FALSE>> is returned if closing one of the file fails, <<TRUE>> is
552 returned if all is well.
553 */
554
555 bool
556 bfd_cache_close_all (void)
557 {
558 bool ret = true;
559
560 while (bfd_last_cache != NULL)
561 ret &= bfd_cache_close (bfd_last_cache);
562
563 return ret;
564 }
565
566 /*
567 INTERNAL_FUNCTION
568 bfd_open_file
569
570 SYNOPSIS
571 FILE* bfd_open_file (bfd *abfd);
572
573 DESCRIPTION
574 Call the OS to open a file for @var{abfd}. Return the <<FILE *>>
575 (possibly <<NULL>>) that results from this operation. Set up the
576 BFD so that future accesses know the file is open. If the <<FILE *>>
577 returned is <<NULL>>, then it won't have been put in the
578 cache, so it won't have to be removed from it.
579 */
580
581 FILE *
582 bfd_open_file (bfd *abfd)
583 {
584 abfd->cacheable = true; /* Allow it to be closed later. */
585
586 if (open_files >= bfd_cache_max_open ())
587 {
588 if (! close_one ())
589 return NULL;
590 }
591
592 switch (abfd->direction)
593 {
594 case read_direction:
595 case no_direction:
596 abfd->iostream = _bfd_real_fopen (bfd_get_filename (abfd), FOPEN_RB);
597 break;
598 case both_direction:
599 case write_direction:
600 if (abfd->opened_once)
601 {
602 abfd->iostream = _bfd_real_fopen (bfd_get_filename (abfd),
603 FOPEN_RUB);
604 if (abfd->iostream == NULL)
605 abfd->iostream = _bfd_real_fopen (bfd_get_filename (abfd),
606 FOPEN_WUB);
607 }
608 else
609 {
610 /* Create the file.
611
612 Some operating systems won't let us overwrite a running
613 binary. For them, we want to unlink the file first.
614
615 However, gcc 2.95 will create temporary files using
616 O_EXCL and tight permissions to prevent other users from
617 substituting other .o files during the compilation. gcc
618 will then tell the assembler to use the newly created
619 file as an output file. If we unlink the file here, we
620 open a brief window when another user could still
621 substitute a file.
622
623 So we unlink the output file if and only if it has
624 non-zero size. */
625 #ifndef __MSDOS__
626 /* Don't do this for MSDOS: it doesn't care about overwriting
627 a running binary, but if this file is already open by
628 another BFD, we will be in deep trouble if we delete an
629 open file. In fact, objdump does just that if invoked with
630 the --info option. */
631 struct stat s;
632
633 if (stat (bfd_get_filename (abfd), &s) == 0 && s.st_size != 0)
634 unlink_if_ordinary (bfd_get_filename (abfd));
635 #endif
636 abfd->iostream = _bfd_real_fopen (bfd_get_filename (abfd),
637 FOPEN_WUB);
638 abfd->opened_once = true;
639 }
640 break;
641 }
642
643 if (abfd->iostream == NULL)
644 bfd_set_error (bfd_error_system_call);
645 else
646 {
647 if (! bfd_cache_init (abfd))
648 return NULL;
649 }
650
651 return (FILE *) abfd->iostream;
652 }