bfd/opncls.c

/* opncls.c -- open and close a BFD.
   Copyright 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 2000,
   2001, 2002, 2003
   Free Software Foundation, Inc.

   Written by Cygnus Support.

   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 2 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */

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

#ifndef S_IXUSR
#define S_IXUSR 0100	/* Execute by owner.  */
#endif
#ifndef S_IXGRP
#define S_IXGRP 0010	/* Execute by group.  */
#endif
#ifndef S_IXOTH
#define S_IXOTH 0001	/* Execute by others.  */
#endif

/* Counter used to initialize the bfd identifier.  */

static unsigned int _bfd_id_counter = 0;

/* fdopen is a loser -- we should use stdio exclusively.  Unfortunately
   if we do that we can't use fcntl.  */

/* Return a new BFD.  All BFD's are allocated through this routine.  */

bfd *
_bfd_new_bfd ()
{
  bfd *nbfd;

  nbfd = (bfd *) bfd_zmalloc ((bfd_size_type) sizeof (bfd));
  if (nbfd == NULL)
    return NULL;

  nbfd->id = _bfd_id_counter++;

  nbfd->memory = (PTR) objalloc_create ();
  if (nbfd->memory == NULL)
    {
      bfd_set_error (bfd_error_no_memory);
      free (nbfd);
      return NULL;
    }

  nbfd->arch_info = &bfd_default_arch_struct;

  nbfd->direction = no_direction;
  nbfd->iostream = NULL;
  nbfd->where = 0;
  if (!bfd_hash_table_init_n (&nbfd->section_htab,
			      bfd_section_hash_newfunc,
			      251))
    {
      free (nbfd);
      return NULL;
    }
  nbfd->sections = (asection *) NULL;
  nbfd->section_tail = &nbfd->sections;
  nbfd->format = bfd_unknown;
  nbfd->my_archive = (bfd *) NULL;
  nbfd->origin = 0;
  nbfd->opened_once = FALSE;
  nbfd->output_has_begun = FALSE;
  nbfd->section_count = 0;
  nbfd->usrdata = (PTR) NULL;
  nbfd->cacheable = FALSE;
  nbfd->flags = BFD_NO_FLAGS;
  nbfd->mtime_set = FALSE;

  return nbfd;
}

/* Allocate a new BFD as a member of archive OBFD.  */

bfd *
_bfd_new_bfd_contained_in (obfd)
     bfd *obfd;
{
  bfd *nbfd;

  nbfd = _bfd_new_bfd ();
  if (nbfd == NULL)
    return NULL;
  nbfd->xvec = obfd->xvec;
  nbfd->my_archive = obfd;
  nbfd->direction = read_direction;
  nbfd->target_defaulted = obfd->target_defaulted;
  return nbfd;
}

/* Delete a BFD.  */

void
_bfd_delete_bfd (abfd)
     bfd *abfd;
{
  bfd_hash_table_free (&abfd->section_htab);
  objalloc_free ((struct objalloc *) abfd->memory);
  free (abfd);
}

/*
SECTION
	Opening and closing BFDs

*/

/*
FUNCTION
	bfd_openr

SYNOPSIS
	bfd *bfd_openr(const char *filename, const char *target);

DESCRIPTION
	Open the file @var{filename} (using <<fopen>>) with the target
	@var{target}.  Return a pointer to the created BFD.

	Calls <<bfd_find_target>>, so @var{target} is interpreted as by
	that function.

	If <<NULL>> is returned then an error has occured.   Possible errors
	are <<bfd_error_no_memory>>, <<bfd_error_invalid_target>> or
	<<system_call>> error.
*/

bfd *
bfd_openr (filename, target)
     const char *filename;
     const char *target;
{
  bfd *nbfd;
  const bfd_target *target_vec;

  nbfd = _bfd_new_bfd ();
  if (nbfd == NULL)
    return NULL;

  target_vec = bfd_find_target (target, nbfd);
  if (target_vec == NULL)
    {
      _bfd_delete_bfd (nbfd);
      return NULL;
    }

  nbfd->filename = filename;
  nbfd->direction = read_direction;

  if (bfd_open_file (nbfd) == NULL)
    {
      /* File didn't exist, or some such.  */
      bfd_set_error (bfd_error_system_call);
      _bfd_delete_bfd (nbfd);
      return NULL;
    }

  return nbfd;
}

/* Don't try to `optimize' this function:

   o - We lock using stack space so that interrupting the locking
       won't cause a storage leak.
   o - We open the file stream last, since we don't want to have to
       close it if anything goes wrong.  Closing the stream means closing
       the file descriptor too, even though we didn't open it.  */
/*
FUNCTION
	bfd_fdopenr

SYNOPSIS
	bfd *bfd_fdopenr(const char *filename, const char *target, int fd);

DESCRIPTION
	<<bfd_fdopenr>> is to <<bfd_fopenr>> much like <<fdopen>> is to
	<<fopen>>.  It opens a BFD on a file already described by the
	@var{fd} supplied.

	When the file is later <<bfd_close>>d, the file descriptor will
	be closed.  If the caller desires that this file descriptor be
	cached by BFD (opened as needed, closed as needed to free
	descriptors for other opens), with the supplied @var{fd} used as
	an initial file descriptor (but subject to closure at any time),
	call bfd_set_cacheable(bfd, 1) on the returned BFD.  The default
	is to assume no cacheing; the file descriptor will remain open
	until <<bfd_close>>, and will not be affected by BFD operations
	on other files.

	Possible errors are <<bfd_error_no_memory>>,
	<<bfd_error_invalid_target>> and <<bfd_error_system_call>>.
*/

bfd *
bfd_fdopenr (filename, target, fd)
     const char *filename;
     const char *target;
     int fd;
{
  bfd *nbfd;
  const bfd_target *target_vec;
  int fdflags;

  bfd_set_error (bfd_error_system_call);
#if ! defined(HAVE_FCNTL) || ! defined(F_GETFL)
  fdflags = O_RDWR;			/* Assume full access.  */
#else
  fdflags = fcntl (fd, F_GETFL, NULL);
#endif
  if (fdflags == -1)
    return NULL;

  nbfd = _bfd_new_bfd ();
  if (nbfd == NULL)
    return NULL;

  target_vec = bfd_find_target (target, nbfd);
  if (target_vec == NULL)
    {
      _bfd_delete_bfd (nbfd);
      return NULL;
    }

#ifndef HAVE_FDOPEN
  nbfd->iostream = (PTR) fopen (filename, FOPEN_RB);
#else
  /* (O_ACCMODE) parens are to avoid Ultrix header file bug.  */
  switch (fdflags & (O_ACCMODE))
    {
    case O_RDONLY: nbfd->iostream = (PTR) fdopen (fd, FOPEN_RB);   break;
    case O_WRONLY: nbfd->iostream = (PTR) fdopen (fd, FOPEN_RUB);  break;
    case O_RDWR:   nbfd->iostream = (PTR) fdopen (fd, FOPEN_RUB);  break;
    default: abort ();
    }
#endif

  if (nbfd->iostream == NULL)
    {
      _bfd_delete_bfd (nbfd);
      return NULL;
    }

  /* OK, put everything where it belongs.  */
  nbfd->filename = filename;

  /* As a special case we allow a FD open for read/write to
     be written through, although doing so requires that we end
     the previous clause with a preposition.  */
  /* (O_ACCMODE) parens are to avoid Ultrix header file bug.  */
  switch (fdflags & (O_ACCMODE))
    {
    case O_RDONLY: nbfd->direction = read_direction; break;
    case O_WRONLY: nbfd->direction = write_direction; break;
    case O_RDWR: nbfd->direction = both_direction; break;
    default: abort ();
    }

  if (! bfd_cache_init (nbfd))
    {
      _bfd_delete_bfd (nbfd);
      return NULL;
    }
  nbfd->opened_once = TRUE;

  return nbfd;
}

/*
FUNCTION
	bfd_openstreamr

SYNOPSIS
	bfd *bfd_openstreamr(const char *, const char *, PTR);

DESCRIPTION

	Open a BFD for read access on an existing stdio stream.  When
	the BFD is passed to <<bfd_close>>, the stream will be closed.
*/

bfd *
bfd_openstreamr (filename, target, streamarg)
     const char *filename;
     const char *target;
     PTR streamarg;
{
  FILE *stream = (FILE *) streamarg;
  bfd *nbfd;
  const bfd_target *target_vec;

  nbfd = _bfd_new_bfd ();
  if (nbfd == NULL)
    return NULL;

  target_vec = bfd_find_target (target, nbfd);
  if (target_vec == NULL)
    {
      _bfd_delete_bfd (nbfd);
      return NULL;
    }

  nbfd->iostream = (PTR) stream;
  nbfd->filename = filename;
  nbfd->direction = read_direction;

  if (! bfd_cache_init (nbfd))
    {
      _bfd_delete_bfd (nbfd);
      return NULL;
    }

  return nbfd;
}

/* bfd_openw -- open for writing.
   Returns a pointer to a freshly-allocated BFD on success, or NULL.

   See comment by bfd_fdopenr before you try to modify this function.  */

/*
FUNCTION
	bfd_openw

SYNOPSIS
	bfd *bfd_openw(const char *filename, const char *target);

DESCRIPTION
	Create a BFD, associated with file @var{filename}, using the
	file format @var{target}, and return a pointer to it.

	Possible errors are <<bfd_error_system_call>>, <<bfd_error_no_memory>>,
	<<bfd_error_invalid_target>>.
*/

bfd *
bfd_openw (filename, target)
     const char *filename;
     const char *target;
{
  bfd *nbfd;
  const bfd_target *target_vec;

  /* nbfd has to point to head of malloc'ed block so that bfd_close may
     reclaim it correctly.  */
  nbfd = _bfd_new_bfd ();
  if (nbfd == NULL)
    return NULL;

  target_vec = bfd_find_target (target, nbfd);
  if (target_vec == NULL)
    {
      _bfd_delete_bfd (nbfd);
      return NULL;
    }

  nbfd->filename = filename;
  nbfd->direction = write_direction;

  if (bfd_open_file (nbfd) == NULL)
    {
      /* File not writeable, etc.  */
      bfd_set_error (bfd_error_system_call);
      _bfd_delete_bfd (nbfd);
      return NULL;
  }

  return nbfd;
}

/*

FUNCTION
	bfd_close

SYNOPSIS
	bfd_boolean bfd_close (bfd *abfd);

DESCRIPTION

	Close a BFD. If the BFD was open for writing, then pending
	operations are completed and the file written out and closed.
	If the created file is executable, then <<chmod>> is called
	to mark it as such.

	All memory attached to the BFD is released.

	The file descriptor associated with the BFD is closed (even
	if it was passed in to BFD by <<bfd_fdopenr>>).

RETURNS
	<<TRUE>> is returned if all is ok, otherwise <<FALSE>>.
*/


bfd_boolean
bfd_close (abfd)
     bfd *abfd;
{
  bfd_boolean ret;

  if (bfd_write_p (abfd))
    {
      if (! BFD_SEND_FMT (abfd, _bfd_write_contents, (abfd)))
	return FALSE;
    }

  if (! BFD_SEND (abfd, _close_and_cleanup, (abfd)))
    return FALSE;

  ret = bfd_cache_close (abfd);

  /* If the file was open for writing and is now executable,
     make it so.  */
  if (ret
      && abfd->direction == write_direction
      && abfd->flags & EXEC_P)
    {
      struct stat buf;

      if (stat (abfd->filename, &buf) == 0)
	{
	  unsigned int mask = umask (0);

	  umask (mask);
	  chmod (abfd->filename,
		 (0777
		  & (buf.st_mode | ((S_IXUSR | S_IXGRP | S_IXOTH) &~ mask))));
	}
    }

  _bfd_delete_bfd (abfd);

  return ret;
}

/*
FUNCTION
	bfd_close_all_done

SYNOPSIS
	bfd_boolean bfd_close_all_done (bfd *);

DESCRIPTION
	Close a BFD.  Differs from <<bfd_close>> since it does not
	complete any pending operations.  This routine would be used
	if the application had just used BFD for swapping and didn't
	want to use any of the writing code.

	If the created file is executable, then <<chmod>> is called
	to mark it as such.

	All memory attached to the BFD is released.

RETURNS
	<<TRUE>> is returned if all is ok, otherwise <<FALSE>>.
*/

bfd_boolean
bfd_close_all_done (abfd)
     bfd *abfd;
{
  bfd_boolean ret;

  ret = bfd_cache_close (abfd);

  /* If the file was open for writing and is now executable,
     make it so.  */
  if (ret
      && abfd->direction == write_direction
      && abfd->flags & EXEC_P)
    {
      struct stat buf;

      if (stat (abfd->filename, &buf) == 0)
	{
	  unsigned int mask = umask (0);

	  umask (mask);
	  chmod (abfd->filename,
		 (0777
		  & (buf.st_mode | ((S_IXUSR | S_IXGRP | S_IXOTH) &~ mask))));
	}
    }

  _bfd_delete_bfd (abfd);

  return ret;
}

/*
FUNCTION
	bfd_create

SYNOPSIS
	bfd *bfd_create(const char *filename, bfd *templ);

DESCRIPTION
	Create a new BFD in the manner of <<bfd_openw>>, but without
	opening a file. The new BFD takes the target from the target
	used by @var{template}. The format is always set to <<bfd_object>>.
*/

bfd *
bfd_create (filename, templ)
     const char *filename;
     bfd *templ;
{
  bfd *nbfd;

  nbfd = _bfd_new_bfd ();
  if (nbfd == NULL)
    return NULL;
  nbfd->filename = filename;
  if (templ)
    nbfd->xvec = templ->xvec;
  nbfd->direction = no_direction;
  bfd_set_format (nbfd, bfd_object);

  return nbfd;
}

/*
FUNCTION
	bfd_make_writable

SYNOPSIS
	bfd_boolean bfd_make_writable (bfd *abfd);

DESCRIPTION
	Takes a BFD as created by <<bfd_create>> and converts it
	into one like as returned by <<bfd_openw>>.  It does this
	by converting the BFD to BFD_IN_MEMORY.  It's assumed that
	you will call <<bfd_make_readable>> on this bfd later.

RETURNS
	<<TRUE>> is returned if all is ok, otherwise <<FALSE>>.
*/

bfd_boolean
bfd_make_writable(abfd)
     bfd *abfd;
{
  struct bfd_in_memory *bim;

  if (abfd->direction != no_direction)
    {
      bfd_set_error (bfd_error_invalid_operation);
      return FALSE;
    }

  bim = ((struct bfd_in_memory *)
	 bfd_malloc ((bfd_size_type) sizeof (struct bfd_in_memory)));
  abfd->iostream = (PTR) bim;
  /* bfd_bwrite will grow these as needed.  */
  bim->size = 0;
  bim->buffer = 0;

  abfd->flags |= BFD_IN_MEMORY;
  abfd->direction = write_direction;
  abfd->where = 0;

  return TRUE;
}

/*
FUNCTION
	bfd_make_readable

SYNOPSIS
	bfd_boolean bfd_make_readable (bfd *abfd);

DESCRIPTION
	Takes a BFD as created by <<bfd_create>> and
	<<bfd_make_writable>> and converts it into one like as
	returned by <<bfd_openr>>.  It does this by writing the
	contents out to the memory buffer, then reversing the
	direction.

RETURNS
	<<TRUE>> is returned if all is ok, otherwise <<FALSE>>.  */

bfd_boolean
bfd_make_readable(abfd)
     bfd *abfd;
{
  if (abfd->direction != write_direction || !(abfd->flags & BFD_IN_MEMORY))
    {
      bfd_set_error (bfd_error_invalid_operation);
      return FALSE;
    }

  if (! BFD_SEND_FMT (abfd, _bfd_write_contents, (abfd)))
    return FALSE;

  if (! BFD_SEND (abfd, _close_and_cleanup, (abfd)))
    return FALSE;


  abfd->arch_info = &bfd_default_arch_struct;

  abfd->where = 0;
  abfd->format = bfd_unknown;
  abfd->my_archive = (bfd *) NULL;
  abfd->origin = 0;
  abfd->opened_once = FALSE;
  abfd->output_has_begun = FALSE;
  abfd->section_count = 0;
  abfd->usrdata = (PTR) NULL;
  abfd->cacheable = FALSE;
  abfd->flags = BFD_IN_MEMORY;
  abfd->mtime_set = FALSE;

  abfd->target_defaulted = TRUE;
  abfd->direction = read_direction;
  abfd->sections = 0;
  abfd->symcount = 0;
  abfd->outsymbols = 0;
  abfd->tdata.any = 0;

  bfd_section_list_clear (abfd);
  bfd_check_format (abfd, bfd_object);

  return TRUE;
}

/*
INTERNAL_FUNCTION
	bfd_alloc

SYNOPSIS
	PTR bfd_alloc (bfd *abfd, size_t wanted);

DESCRIPTION
	Allocate a block of @var{wanted} bytes of memory attached to
	<<abfd>> and return a pointer to it.
*/


PTR
bfd_alloc (abfd, size)
     bfd *abfd;
     bfd_size_type size;
{
  PTR ret;

  if (size != (unsigned long) size)
    {
      bfd_set_error (bfd_error_no_memory);
      return NULL;
    }

  ret = objalloc_alloc (abfd->memory, (unsigned long) size);
  if (ret == NULL)
    bfd_set_error (bfd_error_no_memory);
  return ret;
}

PTR
bfd_zalloc (abfd, size)
     bfd *abfd;
     bfd_size_type size;
{
  PTR res;

  res = bfd_alloc (abfd, size);
  if (res)
    memset (res, 0, (size_t) size);
  return res;
}

/* Free a block allocated for a BFD.
   Note:  Also frees all more recently allocated blocks!  */

void
bfd_release (abfd, block)
     bfd *abfd;
     PTR block;
{
  objalloc_free_block ((struct objalloc *) abfd->memory, block);
}


/* 
   GNU Extension: separate debug-info files 
   
   The idea here is that a special section called .gnu_debuglink might be
   embedded in a binary file, which indicates that some *other* file
   contains the real debugging information. This special section contains a
   filename and CRC32 checksum, which we read and resolve to another file,
   if it exists.

   This facilitates "optional" provision of debugging information, without
   having to provide two complete copies of every binary object (with and
   without debug symbols).
*/

static unsigned long  calc_crc32                  PARAMS ((unsigned long, const unsigned char *, size_t));
static char *         get_debug_link_info         PARAMS ((bfd *, unsigned long *));
static bfd_boolean    separate_debug_file_exists  PARAMS ((const char *, const unsigned long));
static char *         find_separate_debug_file    PARAMS ((bfd *, const char *));

/*
INTERNAL_FUNCTION
	calc_crc32

SYNOPSIS
	unsigned long calc_crc32 (unsigned long crc, const unsigned char *buf, size_t len);

DESCRIPTION
	Advance the CRC32 given by @var{crc} through @var{len}
	bytes of @var{buf}. Return the updated CRC32 value.
*/     

static unsigned long
calc_crc32 (crc, buf, len)
     unsigned long crc;
     const unsigned char *buf;
     size_t len;
{
  static const unsigned long crc32_table[256] =
    {
      0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
      0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
      0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
      0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
      0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
      0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
      0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
      0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
      0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
      0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
      0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
      0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
      0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
      0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
      0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
      0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
      0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
      0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
      0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
      0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
      0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
      0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
      0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
      0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
      0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
      0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
      0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
      0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
      0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
      0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
      0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
      0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
      0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
      0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
      0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
      0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
      0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
      0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
      0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
      0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
      0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
      0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
      0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
      0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
      0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
      0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
      0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
      0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
      0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
      0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
      0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
      0x2d02ef8d
    };
  const unsigned char *end;

  crc = ~crc & 0xffffffff;
  for (end = buf + len; buf < end; ++ buf)
    crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
  return ~crc & 0xffffffff;;
}


/*
INTERNAL_FUNCTION
	get_debug_link_info

SYNOPSIS
	char *get_debug_link_info (bfd *abfd, unsigned long *crc32_out)

DESCRIPTION
	fetch the filename and CRC32 value for any separate debuginfo
	associated with @var{abfd}. Return NULL if no such info found,
	otherwise return filename and update @var{crc32_out}.
*/

static char *
get_debug_link_info (abfd, crc32_out)
     bfd *abfd;
     unsigned long *crc32_out;
{
  asection * sect;
  bfd_size_type debuglink_size;
  unsigned long crc32;
  char * contents;
  int crc_offset;
  bfd_boolean ret;

  BFD_ASSERT (abfd);
  BFD_ASSERT (crc32_out);

  sect = bfd_get_section_by_name (abfd, ".gnu_debuglink");

  if (sect == NULL)
    return NULL;

  debuglink_size = bfd_section_size (abfd, sect);  

  contents = xmalloc (debuglink_size);
  ret = bfd_get_section_contents (abfd, sect, contents,
				  (file_ptr)0, debuglink_size);
  if (! ret)
    {
      free (contents);
      return NULL;
    }

  /* Crc value is stored after the filename, aligned up to 4 bytes.  */
  crc_offset = strlen (contents) + 1;
  crc_offset = (crc_offset + 3) & ~3;

  crc32 = bfd_get_32 (abfd, (bfd_byte *) (contents + crc_offset));

  *crc32_out = crc32;
  return contents;
}

/*
INTERNAL_FUNCTION
	separate_debug_file_exists

SYNOPSIS
	bfd_boolean separate_debug_file_exists (char * name, unsigned long crc32)

DESCRIPTION
	Checks to see if @var{name} is a file and if its contents
	match @var{crc32}.
*/

static bfd_boolean
separate_debug_file_exists (name, crc)
     const char *name;
     const unsigned long crc;
{
  static char buffer [8 * 1024];
  unsigned long file_crc = 0;
  int fd;
  int count;

  BFD_ASSERT (name);

  fd = open (name, O_RDONLY);
  if (fd < 0)
    return FALSE;

  while ((count = read (fd, buffer, sizeof (buffer))) > 0)
    file_crc = calc_crc32 (file_crc, buffer, count);

  close (fd);

  return crc == file_crc;
}


/*
INTERNAL_FUNCTION
	find_separate_debug_file

SYNOPSIS
	char * find_separate_debug_file (bfd *abfd)

DESCRIPTION
	Searches @var{abfd} for a reference to separate debugging
	information, scans various locations in the filesystem, including
	the file tree rooted at @var{debug_file_directory}, and returns a
	filename of such debugging information if the file is found and has
	matching CRC32.  Returns NULL if no reference to debugging file
	exists, or file cannot be found.
*/

static char *
find_separate_debug_file (abfd, debug_file_directory)
     bfd *abfd;
     const char *debug_file_directory;
{
  char *basename;
  char *dir;
  char *debugfile;
  unsigned long crc32;
  int i;

  BFD_ASSERT (abfd);
  if (debug_file_directory == NULL)
    debug_file_directory = ".";

  /* BFD may have been opened from a stream.  */
  if (! abfd->filename)
    return NULL;

  basename = get_debug_link_info (abfd, & crc32);

  if (basename == NULL)
    return NULL;
  if (strlen (basename) < 1)
    {
      free (basename);
      return NULL;
    }

  dir = xstrdup (abfd->filename);
  BFD_ASSERT (strlen (dir) != 0);
  
  /* Strip off filename part.  */
  for (i = strlen (dir) - 1; i >= 0; i--)
    if (IS_DIR_SEPARATOR (dir[i]))
      break;
  
  dir[i + 1] = '\0';
  BFD_ASSERT (dir[i] == '/' || dir[0] == '\0')

  debugfile = xmalloc (strlen (debug_file_directory) + 1
		       + strlen (dir)
		       + strlen (".debug/")
		       + strlen (basename) 
		       + 1);

  /* First try in the same directory as the original file:  */
  strcpy (debugfile, dir);
  strcat (debugfile, basename);

  if (separate_debug_file_exists (debugfile, crc32))
    {
      free (basename);
      free (dir);
      return debugfile;
    }

  /* Then try in a subdirectory called .debug.  */
  strcpy (debugfile, dir);
  strcat (debugfile, ".debug/");
  strcat (debugfile, basename);

  if (separate_debug_file_exists (debugfile, crc32))
    {
      free (basename);
      free (dir);
      return debugfile;
    }

  /* Then try in the global debugfile directory.  */
  strcpy (debugfile, debug_file_directory);
  i = strlen (debug_file_directory) - 1;
  if (i > 0
      && debug_file_directory[i] != '/'
      && dir[0] != '/')
    strcat (debugfile, "/");
  strcat (debugfile, dir);
  strcat (debugfile, basename);

  if (separate_debug_file_exists (debugfile, crc32))
    {
      free (basename);
      free (dir);
      return debugfile;
    }

  free (debugfile);
  free (basename);
  free (dir);
  return NULL;
}


/*
FUNCTION
	bfd_follow_gnu_debuglink

SYNOPSIS
	char * bfd_follow_gnu_debuglink(bfd *abfd, const char *dir);

DESCRIPTION

	Takes a BFD and searches it for a .gnu_debuglink section.  If this
	section is found, examines the section for the name and checksum of
	a '.debug' file containing auxiliary debugging
	information. Searches filesystem for .debug file in some standard
	locations, including the directory tree rooted at @var{dir}, and if
	found returns the full filename. If @var{dir} is NULL, will search
	default path configured into libbfd at build time.

RETURNS
	<<NULL>> on any errors or failure to locate the .debug file,
	otherwise a pointer to a heap-allocated string containing the
	filename. The caller is responsible for freeing this string.
*/

char *
bfd_follow_gnu_debuglink (abfd, dir)
     bfd *abfd;
     const char * dir;
{
#if 0 /* Disabled until DEBUGDIR can be defined by configure.in  */
  if (dir == NULL)
    dir = DEBUGDIR;
#endif
  return find_separate_debug_file (abfd, dir);
}