aboutsummaryrefslogtreecommitdiff
path: root/bfd/cache.c
blob: 17bf7ea9d595328376be7fc15deea7eea0f5feab (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
/* BFD library -- caching of file descriptors.

   Copyright (C) 1990-2016 Free Software Foundation, Inc.

   Hacked by Steve Chamberlain of Cygnus Support (steve@cygnus.com).

   This file is part of BFD, the Binary File Descriptor library.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
   MA 02110-1301, USA.  */

/*
SECTION
	File caching

	The file caching mechanism is embedded within BFD and allows
	the application to open as many BFDs as it wants without
	regard to the underlying operating system's file descriptor
	limit (often as low as 20 open files).  The module in
	<<cache.c>> maintains a least recently used list of
	<<bfd_cache_max_open>> files, and exports the name
	<<bfd_cache_lookup>>, which runs around and makes sure that
	the required BFD is open. If not, then it chooses a file to
	close, closes it and opens the one wanted, returning its file
	handle.

SUBSECTION
	Caching functions
*/

#include "sysdep.h"
#include "bfd.h"
#include "libbfd.h"
#include "libiberty.h"
#include "bfd_stdint.h"

#ifdef HAVE_MMAP
#include <sys/mman.h>
#endif

/* In some cases we can optimize cache operation when reopening files.
   For instance, a flush is entirely unnecessary if the file is already
   closed, so a flush would use CACHE_NO_OPEN.  Similarly, a seek using
   SEEK_SET or SEEK_END need not first seek to the current position.
   For stat we ignore seek errors, just in case the file has changed
   while we weren't looking.  If it has, then it's possible that the
   file is shorter and we don't want a seek error to prevent us doing
   the stat.  */
enum cache_flag {
  CACHE_NORMAL = 0,
  CACHE_NO_OPEN = 1,
  CACHE_NO_SEEK = 2,
  CACHE_NO_SEEK_ERROR = 4
};

/* The maximum number of files which the cache will keep open at
   one time.  When needed call bfd_cache_max_open to initialize.  */

static int max_open_files = 0;

/* Set max_open_files, if not already set, to 12.5% of the allowed open
   file descriptors, but at least 10, and return the value.  */
static int
bfd_cache_max_open (void)
{
  if (max_open_files == 0)
    {
      int max;
#if defined(__sun) && !defined(__sparcv9) && !defined(__x86_64__)
      /* PR ld/19260: 32-bit Solaris has very inelegant handling of the 255
	 file descriptor limit.  The problem is that setrlimit(2) can raise
	 RLIMIT_NOFILE to a value that is not supported by libc, resulting
         in "Too many open files" errors.  This can happen here even though
	 max_open_files is set to rlim.rlim_cur / 8.  For example, if
	 a parent process has set rlim.rlim_cur to 65536, then max_open_files
	 will be computed as 8192.

	 This check essentially reverts to the behavior from binutils 2.23.1
         for 32-bit Solaris only.  (It is hoped that the 32-bit libc
	 limitation will be removed soon).  64-bit Solaris libc does not have
	 this limitation.  */
      max = 16;
#else
#ifdef HAVE_GETRLIMIT
      struct rlimit rlim;

      if (getrlimit (RLIMIT_NOFILE, &rlim) == 0
	  && rlim.rlim_cur != (rlim_t) RLIM_INFINITY)
	max = rlim.rlim_cur / 8;
      else
#endif
#ifdef _SC_OPEN_MAX
	max = sysconf (_SC_OPEN_MAX) / 8;
#else
        max = 10;
#endif
#endif /* not 32-bit Solaris */

      max_open_files = max < 10 ? 10 : max;
    }

  return max_open_files;
}

/* The number of BFD files we have open.  */

static int open_files;

/* Zero, or a pointer to the topmost BFD on the chain.  This is
   used by the <<bfd_cache_lookup>> macro in @file{libbfd.h} to
   determine when it can avoid a function call.  */

static bfd *bfd_last_cache = NULL;

/* Insert a BFD into the cache.  */

static void
insert (bfd *abfd)
{
  if (bfd_last_cache == NULL)
    {
      abfd->lru_next = abfd;
      abfd->lru_prev = abfd;
    }
  else
    {
      abfd->lru_next = bfd_last_cache;
      abfd->lru_prev = bfd_last_cache->lru_prev;
      abfd->lru_prev->lru_next = abfd;
      abfd->lru_next->lru_prev = abfd;
    }
  bfd_last_cache = abfd;
}

/* Remove a BFD from the cache.  */

static void
snip (bfd *abfd)
{
  abfd->lru_prev->lru_next = abfd->lru_next;
  abfd->lru_next->lru_prev = abfd->lru_prev;
  if (abfd == bfd_last_cache)
    {
      bfd_last_cache = abfd->lru_next;
      if (abfd == bfd_last_cache)
	bfd_last_cache = NULL;
    }
}

/* Close a BFD and remove it from the cache.  */

static bfd_boolean
bfd_cache_delete (bfd *abfd)
{
  bfd_boolean ret;

  if (fclose ((FILE *) abfd->iostream) == 0)
    ret = TRUE;
  else
    {
      ret = FALSE;
      bfd_set_error (bfd_error_system_call);
    }

  snip (abfd);

  abfd->iostream = NULL;
  --open_files;

  return ret;
}

/* We need to open a new file, and the cache is full.  Find the least
   recently used cacheable BFD and close it.  */

static bfd_boolean
close_one (void)
{
  register bfd *to_kill;

  if (bfd_last_cache == NULL)
    to_kill = NULL;
  else
    {
      for (to_kill = bfd_last_cache->lru_prev;
	   ! to_kill->cacheable;
	   to_kill = to_kill->lru_prev)
	{
	  if (to_kill == bfd_last_cache)
	    {
	      to_kill = NULL;
	      break;
	    }
	}
    }

  if (to_kill == NULL)
    {
      /* There are no open cacheable BFD's.  */
      return TRUE;
    }

  to_kill->where = real_ftell ((FILE *) to_kill->iostream);

  return bfd_cache_delete (to_kill);
}

/* Check to see if the required BFD is the same as the last one
   looked up. If so, then it can use the stream in the BFD with
   impunity, since it can't have changed since the last lookup;
   otherwise, it has to perform the complicated lookup function.  */

#define bfd_cache_lookup(x, flag) \
  ((x) == bfd_last_cache			\
   ? (FILE *) (bfd_last_cache->iostream)	\
   : bfd_cache_lookup_worker (x, flag))

/* Called when the macro <<bfd_cache_lookup>> fails to find a
   quick answer.  Find a file descriptor for @var{abfd}.  If
   necessary, it open it.  If there are already more than
   <<bfd_cache_max_open>> files open, it tries to close one first, to
   avoid running out of file descriptors.  It will return NULL
   if it is unable to (re)open the @var{abfd}.  */

static FILE *
bfd_cache_lookup_worker (bfd *abfd, enum cache_flag flag)
{
  bfd *orig_bfd = abfd;
  if ((abfd->flags & BFD_IN_MEMORY) != 0)
    abort ();

  while (abfd->my_archive)
    abfd = abfd->my_archive;

  if (abfd->iostream != NULL)
    {
      /* Move the file to the start of the cache.  */
      if (abfd != bfd_last_cache)
	{
	  snip (abfd);
	  insert (abfd);
	}
      return (FILE *) abfd->iostream;
    }

  if (flag & CACHE_NO_OPEN)
    return NULL;

  if (bfd_open_file (abfd) == NULL)
    ;
  else if (!(flag & CACHE_NO_SEEK)
	   && real_fseek ((FILE *) abfd->iostream, abfd->where, SEEK_SET) != 0
	   && !(flag & CACHE_NO_SEEK_ERROR))
    bfd_set_error (bfd_error_system_call);
  else
    return (FILE *) abfd->iostream;

  (*_bfd_error_handler) (_("reopening %B: %s\n"),
			 orig_bfd, bfd_errmsg (bfd_get_error ()));
  return NULL;
}

static file_ptr
cache_btell (struct bfd *abfd)
{
  FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN);
  if (f == NULL)
    return abfd->where;
  return real_ftell (f);
}

static int
cache_bseek (struct bfd *abfd, file_ptr offset, int whence)
{
  FILE *f = bfd_cache_lookup (abfd, whence != SEEK_CUR ? CACHE_NO_SEEK : CACHE_NORMAL);
  if (f == NULL)
    return -1;
  return real_fseek (f, offset, whence);
}

/* Note that archive entries don't have streams; they share their parent's.
   This allows someone to play with the iostream behind BFD's back.

   Also, note that the origin pointer points to the beginning of a file's
   contents (0 for non-archive elements).  For archive entries this is the
   first octet in the file, NOT the beginning of the archive header.  */

static file_ptr
cache_bread_1 (struct bfd *abfd, void *buf, file_ptr nbytes)
{
  FILE *f;
  file_ptr nread;
  /* FIXME - this looks like an optimization, but it's really to cover
     up for a feature of some OSs (not solaris - sigh) that
     ld/pe-dll.c takes advantage of (apparently) when it creates BFDs
     internally and tries to link against them.  BFD seems to be smart
     enough to realize there are no symbol records in the "file" that
     doesn't exist but attempts to read them anyway.  On Solaris,
     attempting to read zero bytes from a NULL file results in a core
     dump, but on other platforms it just returns zero bytes read.
     This makes it to something reasonable. - DJ */
  if (nbytes == 0)
    return 0;

  f = bfd_cache_lookup (abfd, CACHE_NORMAL);
  if (f == NULL)
    return 0;

#if defined (__VAX) && defined (VMS)
  /* Apparently fread on Vax VMS does not keep the record length
     information.  */
  nread = read (fileno (f), buf, nbytes);
  /* Set bfd_error if we did not read as much data as we expected.  If
     the read failed due to an error set the bfd_error_system_call,
     else set bfd_error_file_truncated.  */
  if (nread == (file_ptr)-1)
    {
      bfd_set_error (bfd_error_system_call);
      return nread;
    }
#else
  nread = fread (buf, 1, nbytes, f);
  /* Set bfd_error if we did not read as much data as we expected.  If
     the read failed due to an error set the bfd_error_system_call,
     else set bfd_error_file_truncated.  */
  if (nread < nbytes && ferror (f))
    {
      bfd_set_error (bfd_error_system_call);
      return nread;
    }
#endif
  if (nread < nbytes)
    /* This may or may not be an error, but in case the calling code
       bails out because of it, set the right error code.  */
    bfd_set_error (bfd_error_file_truncated);
  return nread;
}

static file_ptr
cache_bread (struct bfd *abfd, void *buf, file_ptr nbytes)
{
  file_ptr nread = 0;

  /* Some filesystems are unable to handle reads that are too large
     (for instance, NetApp shares with oplocks turned off).  To avoid
     hitting this limitation, we read the buffer in chunks of 8MB max.  */
  while (nread < nbytes)
    {
      const file_ptr max_chunk_size = 0x800000;
      file_ptr chunk_size = nbytes - nread;
      file_ptr chunk_nread;

      if (chunk_size > max_chunk_size)
        chunk_size = max_chunk_size;

      chunk_nread = cache_bread_1 (abfd, (char *) buf + nread, chunk_size);

      /* Update the nread count.

         We just have to be careful of the case when cache_bread_1 returns
         a negative count:  If this is our first read, then set nread to
         that negative count in order to return that negative value to the
         caller.  Otherwise, don't add it to our total count, or we would
         end up returning a smaller number of bytes read than we actually
         did.  */
      if (nread == 0 || chunk_nread > 0)
        nread += chunk_nread;

      if (chunk_nread < chunk_size)
        break;
    }

  return nread;
}

static file_ptr
cache_bwrite (struct bfd *abfd, const void *where, file_ptr nbytes)
{
  file_ptr nwrite;
  FILE *f = bfd_cache_lookup (abfd, CACHE_NORMAL);

  if (f == NULL)
    return 0;
  nwrite = fwrite (where, 1, nbytes, f);
  if (nwrite < nbytes && ferror (f))
    {
      bfd_set_error (bfd_error_system_call);
      return -1;
    }
  return nwrite;
}

static int
cache_bclose (struct bfd *abfd)
{
  return bfd_cache_close (abfd) - 1;
}

static int
cache_bflush (struct bfd *abfd)
{
  int sts;
  FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN);

  if (f == NULL)
    return 0;
  sts = fflush (f);
  if (sts < 0)
    bfd_set_error (bfd_error_system_call);
  return sts;
}

static int
cache_bstat (struct bfd *abfd, struct stat *sb)
{
  int sts;
  FILE *f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR);

  if (f == NULL)
    return -1;
  sts = fstat (fileno (f), sb);
  if (sts < 0)
    bfd_set_error (bfd_error_system_call);
  return sts;
}

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)
{
  void *ret = (void *) -1;

  if ((abfd->flags & BFD_IN_MEMORY) != 0)
    abort ();
#ifdef HAVE_MMAP
  else
    {
      static uintptr_t pagesize_m1;
      FILE *f;
      file_ptr pg_offset;
      bfd_size_type pg_len;

      f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR);
      if (f == NULL)
	return ret;

      if (pagesize_m1 == 0)
        pagesize_m1 = getpagesize () - 1;

      /* Handle archive members.  */
      if (abfd->my_archive != NULL)
        offset += abfd->origin;

      /* Align.  */
      pg_offset = offset & ~pagesize_m1;
      pg_len = (len + (offset - pg_offset) + pagesize_m1) & ~pagesize_m1;

      ret = mmap (addr, pg_len, prot, flags, fileno (f), pg_offset);
      if (ret == (void *) -1)
	bfd_set_error (bfd_error_system_call);
      else
        {
          *map_addr = ret;
          *map_len = pg_len;
          ret = (char *) ret + (offset & pagesize_m1);
        }
    }
#endif

  return ret;
}

static const struct bfd_iovec cache_iovec =
{
  &cache_bread, &cache_bwrite, &cache_btell, &cache_bseek,
  &cache_bclose, &cache_bflush, &cache_bstat, &cache_bmmap
};

/*
INTERNAL_FUNCTION
	bfd_cache_init

SYNOPSIS
	bfd_boolean bfd_cache_init (bfd *abfd);

DESCRIPTION
	Add a newly opened BFD to the cache.
*/

bfd_boolean
bfd_cache_init (bfd *abfd)
{
  BFD_ASSERT (abfd->iostream != NULL);
  if (open_files >= bfd_cache_max_open ())
    {
      if (! close_one ())
	return FALSE;
    }
  abfd->iovec = &cache_iovec;
  insert (abfd);
  ++open_files;
  return TRUE;
}

/*
INTERNAL_FUNCTION
	bfd_cache_close

SYNOPSIS
	bfd_boolean bfd_cache_close (bfd *abfd);

DESCRIPTION
	Remove the BFD @var{abfd} from the cache. If the attached file is open,
	then close it too.

RETURNS
	<<FALSE>> is returned if closing the file fails, <<TRUE>> is
	returned if all is well.
*/

bfd_boolean
bfd_cache_close (bfd *abfd)
{
  if (abfd->iovec != &cache_iovec)
    return TRUE;

  if (abfd->iostream == NULL)
    /* Previously closed.  */
    return TRUE;

  return bfd_cache_delete (abfd);
}

/*
FUNCTION
	bfd_cache_close_all

SYNOPSIS
	bfd_boolean bfd_cache_close_all (void);

DESCRIPTION
	Remove all BFDs from the cache. If the attached file is open,
	then close it too.

RETURNS
	<<FALSE>> is returned if closing one of the file fails, <<TRUE>> is
	returned if all is well.
*/

bfd_boolean
bfd_cache_close_all ()
{
  bfd_boolean ret = TRUE;

  while (bfd_last_cache != NULL)
    ret &= bfd_cache_close (bfd_last_cache);

  return ret;
}

/*
INTERNAL_FUNCTION
	bfd_open_file

SYNOPSIS
	FILE* bfd_open_file (bfd *abfd);

DESCRIPTION
	Call the OS to open a file for @var{abfd}.  Return the <<FILE *>>
	(possibly <<NULL>>) that results from this operation.  Set up the
	BFD so that future accesses know the file is open. If the <<FILE *>>
	returned is <<NULL>>, then it won't have been put in the
	cache, so it won't have to be removed from it.
*/

FILE *
bfd_open_file (bfd *abfd)
{
  abfd->cacheable = TRUE;	/* Allow it to be closed later.  */

  if (open_files >= bfd_cache_max_open ())
    {
      if (! close_one ())
	return NULL;
    }

  switch (abfd->direction)
    {
    case read_direction:
    case no_direction:
      abfd->iostream = real_fopen (abfd->filename, FOPEN_RB);
      break;
    case both_direction:
    case write_direction:
      if (abfd->opened_once)
	{
	  abfd->iostream = real_fopen (abfd->filename, FOPEN_RUB);
	  if (abfd->iostream == NULL)
	    abfd->iostream = real_fopen (abfd->filename, FOPEN_WUB);
	}
      else
	{
	  /* Create the file.

	     Some operating systems won't let us overwrite a running
	     binary.  For them, we want to unlink the file first.

	     However, gcc 2.95 will create temporary files using
	     O_EXCL and tight permissions to prevent other users from
	     substituting other .o files during the compilation.  gcc
	     will then tell the assembler to use the newly created
	     file as an output file.  If we unlink the file here, we
	     open a brief window when another user could still
	     substitute a file.

	     So we unlink the output file if and only if it has
	     non-zero size.  */
#ifndef __MSDOS__
	  /* Don't do this for MSDOS: it doesn't care about overwriting
	     a running binary, but if this file is already open by
	     another BFD, we will be in deep trouble if we delete an
	     open file.  In fact, objdump does just that if invoked with
	     the --info option.  */
	  struct stat s;

	  if (stat (abfd->filename, &s) == 0 && s.st_size != 0)
	    unlink_if_ordinary (abfd->filename);
#endif
	  abfd->iostream = real_fopen (abfd->filename, FOPEN_WUB);
	  abfd->opened_once = TRUE;
	}
      break;
    }

  if (abfd->iostream == NULL)
    bfd_set_error (bfd_error_system_call);
  else
    {
      if (! bfd_cache_init (abfd))
	return NULL;
    }

  return (FILE *) abfd->iostream;
}