/* BFD library -- caching of file descriptors.

   Copyright (C) 1990-2023 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"

#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 bool

bfd_cache_delete (bfd *abfd)

{

  bool 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;

  abfd->flags |= BFD_CLOSED_BY_CACHE;

  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 bool

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 = _bfd_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)

{

  if ((abfd->flags & BFD_IN_MEMORY) != 0)

    abort ();

  if (abfd->my_archive != NULL

      && !bfd_is_thin_archive (abfd->my_archive))

    abort ();

  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)

     && _bfd_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;

  /* xgettext:c-format */

  _bfd_error_handler (_("reopening %pB: %s"),

          abfd, 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 _bfd_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 _bfd_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 (FILE *f, void *buf, file_ptr nbytes)

{

  file_ptr nread;

#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;

  FILE *f;

  f = bfd_cache_lookup (abfd, CACHE_NORMAL);

  if (f == NULL)

    return -1;

  /* 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 (f, (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 *from, file_ptr nbytes)

{

  file_ptr nwrite;

  FILE *f = bfd_cache_lookup (abfd, CACHE_NORMAL);

  if (f == NULL)

    return 0;

  nwrite = fwrite (from, 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;

      /* 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

  bool bfd_cache_init (bfd *abfd);

DESCRIPTION

  Add a newly opened BFD to the cache.

*/

bool

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);

  abfd->flags &= ~BFD_CLOSED_BY_CACHE;

  ++open_files;

  return true;

}

/*

FUNCTION

  bfd_cache_close

SYNOPSIS

  bool bfd_cache_close (bfd *abfd);

DESCRIPTION

  Remove the BFD @var{abfd} from the cache. If the attached file is open,

  then close it too.

  <<FALSE>> is returned if closing the file fails, <<TRUE>> is

  returned if all is well.

*/

bool

bfd_cache_close (bfd *abfd)

{

  /* Don't remove this test.  bfd_reinit depends on it.  */

  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

  bool bfd_cache_close_all (void);

DESCRIPTION

  Remove all BFDs from the cache. If the attached file is open,

  then close it too.  Note - despite its name this function will

  close a BFD even if it is not marked as being cacheable, ie

  even if bfd_get_cacheable() returns false.

  <<FALSE>> is returned if closing one of the file fails, <<TRUE>> is

  returned if all is well.

*/

bool

bfd_cache_close_all (void)

{

  bool ret = true;

  while (bfd_last_cache != NULL)

    {

      bfd *prev_bfd_last_cache = bfd_last_cache;

      ret &= bfd_cache_close (bfd_last_cache);

      /* Stop a potential infinite loop should bfd_cache_close()

   not update bfd_last_cache.  */

      if (bfd_last_cache == prev_bfd_last_cache)

  break;

    }

  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 = _bfd_real_fopen (bfd_get_filename (abfd), FOPEN_RB);

      break;

    case both_direction:

    case write_direction:

      if (abfd->opened_once)

  {

    abfd->iostream = _bfd_real_fopen (bfd_get_filename (abfd),

              FOPEN_RUB);

    if (abfd->iostream == NULL)

      abfd->iostream = _bfd_real_fopen (bfd_get_filename (abfd),

                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 (bfd_get_filename (abfd), &s) == 0 && s.st_size != 0)

      unlink_if_ordinary (bfd_get_filename (abfd));

#endif

    abfd->iostream = _bfd_real_fopen (bfd_get_filename (abfd),

              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;

}