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  1. /* BFD library -- caching of file descriptors.
  2.  
  3.    Copyright 1990, 1991, 1992, 1993, 1994, 1996, 2000, 2001, 2002,
  4.    2003, 2004, 2005, 2007, 2008, 2009 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 3 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,
  23.    MA 02110-1301, USA.  */
  24.  
  25. /*
  26. SECTION
  27.         File caching
  28.  
  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.
  39.  
  40. SUBSECTION
  41.         Caching functions
  42. */
  43.  
  44. #include "sysdep.h"
  45. #include "bfd.h"
  46. #include "libbfd.h"
  47. #include "libiberty.h"
  48. #include "bfd_stdint.h"
  49.  
  50. #ifdef HAVE_MMAP
  51. #include <sys/mman.h>
  52. #endif
  53.  
  54. /* In some cases we can optimize cache operation when reopening files.
  55.    For instance, a flush is entirely unnecessary if the file is already
  56.    closed, so a flush would use CACHE_NO_OPEN.  Similarly, a seek using
  57.    SEEK_SET or SEEK_END need not first seek to the current position.
  58.    For stat we ignore seek errors, just in case the file has changed
  59.    while we weren't looking.  If it has, then it's possible that the
  60.    file is shorter and we don't want a seek error to prevent us doing
  61.    the stat.  */
  62. enum cache_flag {
  63.   CACHE_NORMAL = 0,
  64.   CACHE_NO_OPEN = 1,
  65.   CACHE_NO_SEEK = 2,
  66.   CACHE_NO_SEEK_ERROR = 4
  67. };
  68.  
  69. /* The maximum number of files which the cache will keep open at
  70.    one time.  When needed call bfd_cache_max_open to initialize.  */
  71.  
  72. static int max_open_files = 0;
  73.  
  74. /* Set max_open_files, if not already set, to 12.5% of the allowed open
  75.    file descriptors, but at least 10, and return the value.  */
  76. static int
  77. bfd_cache_max_open (void)
  78. {
  79.   if (max_open_files == 0)
  80.     {
  81.       int max;
  82. #ifdef HAVE_GETRLIMIT
  83.       struct rlimit rlim;
  84.       if (getrlimit (RLIMIT_NOFILE, &rlim) == 0
  85.           && rlim.rlim_cur != RLIM_INFINITY)
  86.         max = rlim.rlim_cur / 8;
  87.       else
  88. #endif /* HAVE_GETRLIMIT */
  89. #ifdef _SC_OPEN_MAX
  90.         max = sysconf (_SC_OPEN_MAX) / 8;
  91. #else
  92.         max = 10;
  93. #endif /* _SC_OPEN_MAX */
  94.       max_open_files = max < 10 ? 10 : max;
  95.     }
  96.  
  97.   return max_open_files;
  98. }
  99.  
  100. /* The number of BFD files we have open.  */
  101.  
  102. static int open_files;
  103.  
  104. /* Zero, or a pointer to the topmost BFD on the chain.  This is
  105.    used by the <<bfd_cache_lookup>> macro in @file{libbfd.h} to
  106.    determine when it can avoid a function call.  */
  107.  
  108. static bfd *bfd_last_cache = NULL;
  109.  
  110. /* Insert a BFD into the cache.  */
  111.  
  112. static void
  113. insert (bfd *abfd)
  114. {
  115.   if (bfd_last_cache == NULL)
  116.     {
  117.       abfd->lru_next = abfd;
  118.       abfd->lru_prev = abfd;
  119.     }
  120.   else
  121.     {
  122.       abfd->lru_next = bfd_last_cache;
  123.       abfd->lru_prev = bfd_last_cache->lru_prev;
  124.       abfd->lru_prev->lru_next = abfd;
  125.       abfd->lru_next->lru_prev = abfd;
  126.     }
  127.   bfd_last_cache = abfd;
  128. }
  129.  
  130. /* Remove a BFD from the cache.  */
  131.  
  132. static void
  133. snip (bfd *abfd)
  134. {
  135.   abfd->lru_prev->lru_next = abfd->lru_next;
  136.   abfd->lru_next->lru_prev = abfd->lru_prev;
  137.   if (abfd == bfd_last_cache)
  138.     {
  139.       bfd_last_cache = abfd->lru_next;
  140.       if (abfd == bfd_last_cache)
  141.         bfd_last_cache = NULL;
  142.     }
  143. }
  144.  
  145. /* Close a BFD and remove it from the cache.  */
  146.  
  147. static bfd_boolean
  148. bfd_cache_delete (bfd *abfd)
  149. {
  150.   bfd_boolean ret;
  151.  
  152.   if (fclose ((FILE *) abfd->iostream) == 0)
  153.     ret = TRUE;
  154.   else
  155.     {
  156.       ret = FALSE;
  157.       bfd_set_error (bfd_error_system_call);
  158.     }
  159.  
  160.   snip (abfd);
  161.  
  162.   abfd->iostream = NULL;
  163.   --open_files;
  164.  
  165.   return ret;
  166. }
  167.  
  168. /* We need to open a new file, and the cache is full.  Find the least
  169.    recently used cacheable BFD and close it.  */
  170.  
  171. static bfd_boolean
  172. close_one (void)
  173. {
  174.   register bfd *to_kill;
  175.  
  176.   if (bfd_last_cache == NULL)
  177.     to_kill = NULL;
  178.   else
  179.     {
  180.       for (to_kill = bfd_last_cache->lru_prev;
  181.            ! to_kill->cacheable;
  182.            to_kill = to_kill->lru_prev)
  183.         {
  184.           if (to_kill == bfd_last_cache)
  185.             {
  186.               to_kill = NULL;
  187.               break;
  188.             }
  189.         }
  190.     }
  191.  
  192.   if (to_kill == NULL)
  193.     {
  194.       /* There are no open cacheable BFD's.  */
  195.       return TRUE;
  196.     }
  197.  
  198.   to_kill->where = real_ftell ((FILE *) to_kill->iostream);
  199.  
  200.   return bfd_cache_delete (to_kill);
  201. }
  202.  
  203. /* Check to see if the required BFD is the same as the last one
  204.    looked up. If so, then it can use the stream in the BFD with
  205.    impunity, since it can't have changed since the last lookup;
  206.    otherwise, it has to perform the complicated lookup function.  */
  207.  
  208. #define bfd_cache_lookup(x, flag) \
  209.   ((x) == bfd_last_cache                        \
  210.    ? (FILE *) (bfd_last_cache->iostream)        \
  211.    : bfd_cache_lookup_worker (x, flag))
  212.  
  213. /* Called when the macro <<bfd_cache_lookup>> fails to find a
  214.    quick answer.  Find a file descriptor for @var{abfd}.  If
  215.    necessary, it open it.  If there are already more than
  216.    <<bfd_cache_max_open>> files open, it tries to close one first, to
  217.    avoid running out of file descriptors.  It will return NULL
  218.    if it is unable to (re)open the @var{abfd}.  */
  219.  
  220. static FILE *
  221. bfd_cache_lookup_worker (bfd *abfd, enum cache_flag flag)
  222. {
  223.   bfd *orig_bfd = abfd;
  224.   if ((abfd->flags & BFD_IN_MEMORY) != 0)
  225.     abort ();
  226.  
  227.   while (abfd->my_archive)
  228.     abfd = abfd->my_archive;
  229.  
  230.   if (abfd->iostream != NULL)
  231.     {
  232.       /* Move the file to the start of the cache.  */
  233.       if (abfd != bfd_last_cache)
  234.         {
  235.           snip (abfd);
  236.           insert (abfd);
  237.         }
  238.       return (FILE *) abfd->iostream;
  239.     }
  240.  
  241.   if (flag & CACHE_NO_OPEN)
  242.     return NULL;
  243.  
  244.   if (bfd_open_file (abfd) == NULL)
  245.     ;
  246.   else if (!(flag & CACHE_NO_SEEK)
  247.            && real_fseek ((FILE *) abfd->iostream, abfd->where, SEEK_SET) != 0
  248.            && !(flag & CACHE_NO_SEEK_ERROR))
  249.     bfd_set_error (bfd_error_system_call);
  250.   else
  251.     return (FILE *) abfd->iostream;
  252.  
  253.   (*_bfd_error_handler) (_("reopening %B: %s\n"),
  254.                          orig_bfd, bfd_errmsg (bfd_get_error ()));
  255.   return NULL;
  256. }
  257.  
  258. static file_ptr
  259. cache_btell (struct bfd *abfd)
  260. {
  261.   FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN);
  262.   if (f == NULL)
  263.     return abfd->where;
  264.   return real_ftell (f);
  265. }
  266.  
  267. static int
  268. cache_bseek (struct bfd *abfd, file_ptr offset, int whence)
  269. {
  270.   FILE *f = bfd_cache_lookup (abfd, whence != SEEK_CUR ? CACHE_NO_SEEK : CACHE_NORMAL);
  271.   if (f == NULL)
  272.     return -1;
  273.   return real_fseek (f, offset, whence);
  274. }
  275.  
  276. /* Note that archive entries don't have streams; they share their parent's.
  277.    This allows someone to play with the iostream behind BFD's back.
  278.  
  279.    Also, note that the origin pointer points to the beginning of a file's
  280.    contents (0 for non-archive elements).  For archive entries this is the
  281.    first octet in the file, NOT the beginning of the archive header.  */
  282.  
  283. static file_ptr
  284. cache_bread_1 (struct bfd *abfd, void *buf, file_ptr nbytes)
  285. {
  286.   FILE *f;
  287.   file_ptr nread;
  288.   /* FIXME - this looks like an optimization, but it's really to cover
  289.      up for a feature of some OSs (not solaris - sigh) that
  290.      ld/pe-dll.c takes advantage of (apparently) when it creates BFDs
  291.      internally and tries to link against them.  BFD seems to be smart
  292.      enough to realize there are no symbol records in the "file" that
  293.      doesn't exist but attempts to read them anyway.  On Solaris,
  294.      attempting to read zero bytes from a NULL file results in a core
  295.      dump, but on other platforms it just returns zero bytes read.
  296.      This makes it to something reasonable. - DJ */
  297.   if (nbytes == 0)
  298.     return 0;
  299.  
  300.   f = bfd_cache_lookup (abfd, CACHE_NORMAL);
  301.   if (f == NULL)
  302.     return 0;
  303.  
  304. #if defined (__VAX) && defined (VMS)
  305.   /* Apparently fread on Vax VMS does not keep the record length
  306.      information.  */
  307.   nread = read (fileno (f), buf, nbytes);
  308.   /* Set bfd_error if we did not read as much data as we expected.  If
  309.      the read failed due to an error set the bfd_error_system_call,
  310.      else set bfd_error_file_truncated.  */
  311.   if (nread == (file_ptr)-1)
  312.     {
  313.       bfd_set_error (bfd_error_system_call);
  314.       return -1;
  315.     }
  316. #else
  317.   nread = fread (buf, 1, nbytes, f);
  318.   /* Set bfd_error if we did not read as much data as we expected.  If
  319.      the read failed due to an error set the bfd_error_system_call,
  320.      else set bfd_error_file_truncated.  */
  321.   if (nread < nbytes && ferror (f))
  322.     {
  323.       bfd_set_error (bfd_error_system_call);
  324.       return -1;
  325.     }
  326. #endif
  327.   if (nread < nbytes)
  328.     /* This may or may not be an error, but in case the calling code
  329.        bails out because of it, set the right error code.  */
  330.     bfd_set_error (bfd_error_file_truncated);
  331.   return nread;
  332. }
  333.  
  334. static file_ptr
  335. cache_bread (struct bfd *abfd, void *buf, file_ptr nbytes)
  336. {
  337.   file_ptr nread = 0;
  338.  
  339.   /* Some filesystems are unable to handle reads that are too large
  340.      (for instance, NetApp shares with oplocks turned off).  To avoid
  341.      hitting this limitation, we read the buffer in chunks of 8MB max.  */
  342.   while (nread < nbytes)
  343.     {
  344.       const file_ptr max_chunk_size = 0x800000;
  345.       file_ptr chunk_size = nbytes - nread;
  346.       file_ptr chunk_nread;
  347.  
  348.       if (chunk_size > max_chunk_size)
  349.         chunk_size = max_chunk_size;
  350.  
  351.       chunk_nread = cache_bread_1 (abfd, (char *) buf + nread, chunk_size);
  352.  
  353.       /* Update the nread count.
  354.  
  355.          We just have to be careful of the case when cache_bread_1 returns
  356.          a negative count:  If this is our first read, then set nread to
  357.          that negative count in order to return that negative value to the
  358.          caller.  Otherwise, don't add it to our total count, or we would
  359.          end up returning a smaller number of bytes read than we actually
  360.          did.  */
  361.       if (nread == 0 || chunk_nread > 0)
  362.         nread += chunk_nread;
  363.  
  364.       if (chunk_nread < chunk_size)
  365.         break;
  366.     }
  367.  
  368.   return nread;
  369. }
  370.  
  371. static file_ptr
  372. cache_bwrite (struct bfd *abfd, const void *where, file_ptr nbytes)
  373. {
  374.   file_ptr nwrite;
  375.   FILE *f = bfd_cache_lookup (abfd, CACHE_NORMAL);
  376.  
  377.   if (f == NULL)
  378.     return 0;
  379.   nwrite = fwrite (where, 1, nbytes, f);
  380.   if (nwrite < nbytes && ferror (f))
  381.     {
  382.       bfd_set_error (bfd_error_system_call);
  383.       return -1;
  384.     }
  385.   return nwrite;
  386. }
  387.  
  388. static int
  389. cache_bclose (struct bfd *abfd)
  390. {
  391.   return bfd_cache_close (abfd) - 1;
  392. }
  393.  
  394. static int
  395. cache_bflush (struct bfd *abfd)
  396. {
  397.   int sts;
  398.   FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN);
  399.  
  400.   if (f == NULL)
  401.     return 0;
  402.   sts = fflush (f);
  403.   if (sts < 0)
  404.     bfd_set_error (bfd_error_system_call);
  405.   return sts;
  406. }
  407.  
  408. static int
  409. cache_bstat (struct bfd *abfd, struct stat *sb)
  410. {
  411.   int sts;
  412.   FILE *f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR);
  413.  
  414.   if (f == NULL)
  415.     return -1;
  416.   sts = fstat (fileno (f), sb);
  417.   if (sts < 0)
  418.     bfd_set_error (bfd_error_system_call);
  419.   return sts;
  420. }
  421.  
  422. static void *
  423. cache_bmmap (struct bfd *abfd ATTRIBUTE_UNUSED,
  424.              void *addr ATTRIBUTE_UNUSED,
  425.              bfd_size_type len ATTRIBUTE_UNUSED,
  426.              int prot ATTRIBUTE_UNUSED,
  427.              int flags ATTRIBUTE_UNUSED,
  428.              file_ptr offset ATTRIBUTE_UNUSED,
  429.              void **map_addr ATTRIBUTE_UNUSED,
  430.              bfd_size_type *map_len ATTRIBUTE_UNUSED)
  431. {
  432.   void *ret = (void *) -1;
  433.  
  434.   if ((abfd->flags & BFD_IN_MEMORY) != 0)
  435.     abort ();
  436. #ifdef HAVE_MMAP
  437.   else
  438.     {
  439.       static uintptr_t pagesize_m1;
  440.       FILE *f;
  441.       file_ptr pg_offset;
  442.       bfd_size_type pg_len;
  443.  
  444.       f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR);
  445.       if (f == NULL)
  446.         return ret;
  447.  
  448.       if (pagesize_m1 == 0)
  449.         pagesize_m1 = getpagesize () - 1;
  450.  
  451.       /* Handle archive members.  */
  452.       if (abfd->my_archive != NULL)
  453.         offset += abfd->origin;
  454.  
  455.       /* Align.  */
  456.       pg_offset = offset & ~pagesize_m1;
  457.       pg_len = (len + (offset - pg_offset) + pagesize_m1) & ~pagesize_m1;
  458.  
  459.       ret = mmap (addr, pg_len, prot, flags, fileno (f), pg_offset);
  460.       if (ret == (void *) -1)
  461.         bfd_set_error (bfd_error_system_call);
  462.       else
  463.         {
  464.           *map_addr = ret;
  465.           *map_len = pg_len;
  466.           ret = (char *) ret + (offset & pagesize_m1);
  467.         }
  468.     }
  469. #endif
  470.  
  471.   return ret;
  472. }
  473.  
  474. static const struct bfd_iovec cache_iovec =
  475. {
  476.   &cache_bread, &cache_bwrite, &cache_btell, &cache_bseek,
  477.   &cache_bclose, &cache_bflush, &cache_bstat, &cache_bmmap
  478. };
  479.  
  480. /*
  481. INTERNAL_FUNCTION
  482.         bfd_cache_init
  483.  
  484. SYNOPSIS
  485.         bfd_boolean bfd_cache_init (bfd *abfd);
  486.  
  487. DESCRIPTION
  488.         Add a newly opened BFD to the cache.
  489. */
  490.  
  491. bfd_boolean
  492. bfd_cache_init (bfd *abfd)
  493. {
  494.   BFD_ASSERT (abfd->iostream != NULL);
  495.   if (open_files >= bfd_cache_max_open ())
  496.     {
  497.       if (! close_one ())
  498.         return FALSE;
  499.     }
  500.   abfd->iovec = &cache_iovec;
  501.   insert (abfd);
  502.   ++open_files;
  503.   return TRUE;
  504. }
  505.  
  506. /*
  507. INTERNAL_FUNCTION
  508.         bfd_cache_close
  509.  
  510. SYNOPSIS
  511.         bfd_boolean bfd_cache_close (bfd *abfd);
  512.  
  513. DESCRIPTION
  514.         Remove the BFD @var{abfd} from the cache. If the attached file is open,
  515.         then close it too.
  516.  
  517. RETURNS
  518.         <<FALSE>> is returned if closing the file fails, <<TRUE>> is
  519.         returned if all is well.
  520. */
  521.  
  522. bfd_boolean
  523. bfd_cache_close (bfd *abfd)
  524. {
  525.   if (abfd->iovec != &cache_iovec)
  526.     return TRUE;
  527.  
  528.   if (abfd->iostream == NULL)
  529.     /* Previously closed.  */
  530.     return TRUE;
  531.  
  532.   return bfd_cache_delete (abfd);
  533. }
  534.  
  535. /*
  536. FUNCTION
  537.         bfd_cache_close_all
  538.  
  539. SYNOPSIS
  540.         bfd_boolean bfd_cache_close_all (void);
  541.  
  542. DESCRIPTION
  543.         Remove all BFDs from the cache. If the attached file is open,
  544.         then close it too.
  545.  
  546. RETURNS
  547.         <<FALSE>> is returned if closing one of the file fails, <<TRUE>> is
  548.         returned if all is well.
  549. */
  550.  
  551. bfd_boolean
  552. bfd_cache_close_all ()
  553. {
  554.   bfd_boolean ret = TRUE;
  555.  
  556.   while (bfd_last_cache != NULL)
  557.     ret &= bfd_cache_close (bfd_last_cache);
  558.  
  559.   return ret;
  560. }
  561.  
  562. /*
  563. INTERNAL_FUNCTION
  564.         bfd_open_file
  565.  
  566. SYNOPSIS
  567.         FILE* bfd_open_file (bfd *abfd);
  568.  
  569. DESCRIPTION
  570.         Call the OS to open a file for @var{abfd}.  Return the <<FILE *>>
  571.         (possibly <<NULL>>) that results from this operation.  Set up the
  572.         BFD so that future accesses know the file is open. If the <<FILE *>>
  573.         returned is <<NULL>>, then it won't have been put in the
  574.         cache, so it won't have to be removed from it.
  575. */
  576.  
  577. FILE *
  578. bfd_open_file (bfd *abfd)
  579. {
  580.   abfd->cacheable = TRUE;       /* Allow it to be closed later.  */
  581.  
  582.   if (open_files >= bfd_cache_max_open ())
  583.     {
  584.       if (! close_one ())
  585.         return NULL;
  586.     }
  587.  
  588.   switch (abfd->direction)
  589.     {
  590.     case read_direction:
  591.     case no_direction:
  592.       abfd->iostream = real_fopen (abfd->filename, FOPEN_RB);
  593.       break;
  594.     case both_direction:
  595.     case write_direction:
  596.       if (abfd->opened_once)
  597.         {
  598.           abfd->iostream = real_fopen (abfd->filename, FOPEN_RUB);
  599.           if (abfd->iostream == NULL)
  600.             abfd->iostream = real_fopen (abfd->filename, FOPEN_WUB);
  601.         }
  602.       else
  603.         {
  604.           /* Create the file.
  605.  
  606.              Some operating systems won't let us overwrite a running
  607.              binary.  For them, we want to unlink the file first.
  608.  
  609.              However, gcc 2.95 will create temporary files using
  610.              O_EXCL and tight permissions to prevent other users from
  611.              substituting other .o files during the compilation.  gcc
  612.              will then tell the assembler to use the newly created
  613.              file as an output file.  If we unlink the file here, we
  614.              open a brief window when another user could still
  615.              substitute a file.
  616.  
  617.              So we unlink the output file if and only if it has
  618.              non-zero size.  */
  619. #ifndef __MSDOS__
  620.           /* Don't do this for MSDOS: it doesn't care about overwriting
  621.              a running binary, but if this file is already open by
  622.              another BFD, we will be in deep trouble if we delete an
  623.              open file.  In fact, objdump does just that if invoked with
  624.              the --info option.  */
  625.           struct stat s;
  626.  
  627.           if (stat (abfd->filename, &s) == 0 && s.st_size != 0)
  628.             unlink_if_ordinary (abfd->filename);
  629. #endif
  630.           abfd->iostream = real_fopen (abfd->filename, FOPEN_WUB);
  631.           abfd->opened_once = TRUE;
  632.         }
  633.       break;
  634.     }
  635.  
  636.   if (abfd->iostream == NULL)
  637.     bfd_set_error (bfd_error_system_call);
  638.   else
  639.     {
  640.       if (! bfd_cache_init (abfd))
  641.         return NULL;
  642.     }
  643.  
  644.   return (FILE *) abfd->iostream;
  645. }
  646.