text: /* Generic BFD support for file formats.
     Copyright (C) 1990-2020 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 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 formats
  
  	A format is a BFD concept of high level file contents type. The
  	formats supported by BFD are:
  
  	o <<bfd_object>>
  
  	The BFD may contain data, symbols, relocations and debug info.
  
  	o <<bfd_archive>>
  
  	The BFD contains other BFDs and an optional index.
  
  	o <<bfd_core>>
  
  	The BFD contains the result of an executable core dump.
  
  SUBSECTION
  	File format functions
  */
  
  #include "sysdep.h"
  #include "bfd.h"
  #include "libbfd.h"
  
  /* IMPORT from targets.c.  */
  extern const size_t _bfd_target_vector_entries;
  
  /*
  FUNCTION
  	bfd_check_format
  
  SYNOPSIS
  	bfd_boolean bfd_check_format (bfd *abfd, bfd_format format);
  
  DESCRIPTION
  	Verify if the file attached to the BFD @var{abfd} is compatible
  	with the format @var{format} (i.e., one of <<bfd_object>>,
  	<<bfd_archive>> or <<bfd_core>>).
  
  	If the BFD has been set to a specific target before the
  	call, only the named target and format combination is
  	checked. If the target has not been set, or has been set to
  	<<default>>, then all the known target backends is
  	interrogated to determine a match.  If the default target
  	matches, it is used.  If not, exactly one target must recognize
  	the file, or an error results.
  
  	The function returns <<TRUE>> on success, otherwise <<FALSE>>
  	with one of the following error codes:
  
  	o <<bfd_error_invalid_operation>> -
  	if <<format>> is not one of <<bfd_object>>, <<bfd_archive>> or
  	<<bfd_core>>.
  
  	o <<bfd_error_system_call>> -
  	if an error occured during a read - even some file mismatches
  	can cause bfd_error_system_calls.
  
  	o <<file_not_recognised>> -
  	none of the backends recognised the file format.
  
  	o <<bfd_error_file_ambiguously_recognized>> -
  	more than one backend recognised the file format.
  */
  
  bfd_boolean
  bfd_check_format (bfd *abfd, bfd_format format)
  {
    return bfd_check_format_matches (abfd, format, NULL);
  }
  
  struct bfd_preserve
  {
    void *marker;
    void *tdata;
    flagword flags;
    const struct bfd_arch_info *arch_info;
    struct bfd_section *sections;
    struct bfd_section *section_last;
    unsigned int section_count;
    unsigned int section_id;
    struct bfd_hash_table section_htab;
    const struct bfd_build_id *build_id;
  };
  
  /* When testing an object for compatibility with a particular target
     back-end, the back-end object_p function needs to set up certain
     fields in the bfd on successfully recognizing the object.  This
     typically happens in a piecemeal fashion, with failures possible at
     many points.  On failure, the bfd is supposed to be restored to its
     initial state, which is virtually impossible.  However, restoring a
     subset of the bfd state works in practice.  This function stores
     the subset.  */
  
  static bfd_boolean
  bfd_preserve_save (bfd *abfd, struct bfd_preserve *preserve)
  {
    preserve->tdata = abfd->tdata.any;
    preserve->arch_info = abfd->arch_info;
    preserve->flags = abfd->flags;
    preserve->sections = abfd->sections;
    preserve->section_last = abfd->section_last;
    preserve->section_count = abfd->section_count;
    preserve->section_id = _bfd_section_id;
    preserve->section_htab = abfd->section_htab;
    preserve->marker = bfd_alloc (abfd, 1);
    preserve->build_id = abfd->build_id;
    if (preserve->marker == NULL)
      return FALSE;
  
    return bfd_hash_table_init (&abfd->section_htab, bfd_section_hash_newfunc,
  			      sizeof (struct section_hash_entry));
  }
  
  /* Clear out a subset of BFD state.  */
  
  static void
  bfd_reinit (bfd *abfd, unsigned int section_id)
  {
    abfd->tdata.any = NULL;
    abfd->arch_info = &bfd_default_arch_struct;
    abfd->flags &= BFD_FLAGS_SAVED;
    bfd_section_list_clear (abfd);
    _bfd_section_id = section_id;
  }
  
  /* Restores bfd state saved by bfd_preserve_save.  */
  
  static void
  bfd_preserve_restore (bfd *abfd, struct bfd_preserve *preserve)
  {
    bfd_hash_table_free (&abfd->section_htab);
  
    abfd->tdata.any = preserve->tdata;
    abfd->arch_info = preserve->arch_info;
    abfd->flags = preserve->flags;
    abfd->section_htab = preserve->section_htab;
    abfd->sections = preserve->sections;
    abfd->section_last = preserve->section_last;
    abfd->section_count = preserve->section_count;
    _bfd_section_id = preserve->section_id;
    abfd->build_id = preserve->build_id;
  
    /* bfd_release frees all memory more recently bfd_alloc'd than
       its arg, as well as its arg.  */
    bfd_release (abfd, preserve->marker);
    preserve->marker = NULL;
  }
  
  /* Called when the bfd state saved by bfd_preserve_save is no longer
     needed.  */
  
  static void
  bfd_preserve_finish (bfd *abfd ATTRIBUTE_UNUSED, struct bfd_preserve *preserve)
  {
    /* It would be nice to be able to free more memory here, eg. old
       tdata, but that's not possible since these blocks are sitting
       inside bfd_alloc'd memory.  The section hash is on a separate
       objalloc.  */
    bfd_hash_table_free (&preserve->section_htab);
    preserve->marker = NULL;
  }
  
  /*
  FUNCTION
  	bfd_check_format_matches
  
  SYNOPSIS
  	bfd_boolean bfd_check_format_matches
  	  (bfd *abfd, bfd_format format, char ***matching);
  
  DESCRIPTION
  	Like <<bfd_check_format>>, except when it returns FALSE with
  	<<bfd_errno>> set to <<bfd_error_file_ambiguously_recognized>>.  In that
  	case, if @var{matching} is not NULL, it will be filled in with
  	a NULL-terminated list of the names of the formats that matched,
  	allocated with <<malloc>>.
  	Then the user may choose a format and try again.
  
  	When done with the list that @var{matching} points to, the caller
  	should free it.
  */
  
  bfd_boolean
  bfd_check_format_matches (bfd *abfd, bfd_format format, char ***matching)
  {
    extern const bfd_target binary_vec;
  #if BFD_SUPPORTS_PLUGINS
    extern const bfd_target plugin_vec;
  #endif
    const bfd_target * const *target;
    const bfd_target **matching_vector = NULL;
    const bfd_target *save_targ, *right_targ, *ar_right_targ, *match_targ;
    int match_count, best_count, best_match;
    int ar_match_index;
    unsigned int initial_section_id = _bfd_section_id;
    struct bfd_preserve preserve, preserve_match;
  
    if (matching != NULL)
      *matching = NULL;
  
    if (!bfd_read_p (abfd)
        || (unsigned int) abfd->format >= (unsigned int) bfd_type_end)
      {
        bfd_set_error (bfd_error_invalid_operation);
        return FALSE;
      }
  
    if (abfd->format != bfd_unknown)
      return abfd->format == format;
  
    if (matching != NULL || *bfd_associated_vector != NULL)
      {
        bfd_size_type amt;
  
        amt = sizeof (*matching_vector) * 2 * _bfd_target_vector_entries;
        matching_vector = (const bfd_target **) bfd_malloc (amt);
        if (!matching_vector)
  	return FALSE;
      }
  
    /* Presume the answer is yes.  */
    abfd->format = format;
    save_targ = abfd->xvec;
  
    preserve_match.marker = NULL;
    if (!bfd_preserve_save (abfd, &preserve))
      goto err_ret;
  
    /* If the target type was explicitly specified, just check that target.  */
    if (!abfd->target_defaulted)
      {
        if (bfd_seek (abfd, (file_ptr) 0, SEEK_SET) != 0)	/* rewind! */
  	goto err_ret;
  
        right_targ = BFD_SEND_FMT (abfd, _bfd_check_format, (abfd));
  
        if (right_targ)
  	goto ok_ret;
  
        /* For a long time the code has dropped through to check all
  	 targets if the specified target was wrong.  I don't know why,
  	 and I'm reluctant to change it.  However, in the case of an
  	 archive, it can cause problems.  If the specified target does
  	 not permit archives (e.g., the binary target), then we should
  	 not allow some other target to recognize it as an archive, but
  	 should instead allow the specified target to recognize it as an
  	 object.  When I first made this change, it broke the PE target,
  	 because the specified pei-i386 target did not recognize the
  	 actual pe-i386 archive.  Since there may be other problems of
  	 this sort, I changed this test to check only for the binary
  	 target.  */
        if (format == bfd_archive && save_targ == &binary_vec)
  	goto err_unrecog;
      }
  
    /* Since the target type was defaulted, check them all in the hope
       that one will be uniquely recognized.  */
    right_targ = NULL;
    ar_right_targ = NULL;
    match_targ = NULL;
    best_match = 256;
    best_count = 0;
    match_count = 0;
    ar_match_index = _bfd_target_vector_entries;
  
    for (target = bfd_target_vector; *target != NULL; target++)
      {
        const bfd_target *temp;
        void **high_water;
  
        /* The binary target matches anything, so don't return it when
  	 searching.  Don't match the plugin target if we have another
  	 alternative since we want to properly set the input format
  	 before allowing a plugin to claim the file.  Also, don't
  	 check the default target twice.  */
        if (*target == &binary_vec
  #if BFD_SUPPORTS_PLUGINS
  	  || (match_count != 0 && *target == &plugin_vec)
  #endif
  	  || (!abfd->target_defaulted && *target == save_targ))
  	continue;
  
        /* If we already tried a match, the bfd is modified and may
  	 have sections attached, which will confuse the next
  	 _bfd_check_format call.  */
        bfd_reinit (abfd, initial_section_id);
        /* Free bfd_alloc memory too.  If we have matched and preserved
  	 a target then the high water mark is that much higher.  */
        if (preserve_match.marker)
  	high_water = &preserve_match.marker;
        else
  	high_water = &preserve.marker;
        bfd_release (abfd, *high_water);
        *high_water = bfd_alloc (abfd, 1);
  
        /* Change BFD's target temporarily.  */
        abfd->xvec = *target;
  
        if (bfd_seek (abfd, (file_ptr) 0, SEEK_SET) != 0)
  	goto err_ret;
  
        temp = BFD_SEND_FMT (abfd, _bfd_check_format, (abfd));
        if (temp)
  	{
  	  int match_priority = temp->match_priority;
  #if BFD_SUPPORTS_PLUGINS
  	  /* If this object can be handled by a plugin, give that the
  	     lowest priority; objects both handled by a plugin and
  	     with an underlying object format will be claimed
  	     separately by the plugin.  */
  	  if (*target == &plugin_vec)
  	    match_priority = (*target)->match_priority;
  #endif
  
  	  if (abfd->format != bfd_archive
  	      || (bfd_has_map (abfd)
  		  && bfd_get_error () != bfd_error_wrong_object_format))
  	    {
  	      /* If this is the default target, accept it, even if
  		 other targets might match.  People who want those
  		 other targets have to set the GNUTARGET variable.  */
  	      if (temp == bfd_default_vector[0])
  		goto ok_ret;
  
  	      if (matching_vector)
  		matching_vector[match_count] = temp;
  	      match_count++;
  
  	      if (match_priority < best_match)
  		{
  		  best_match = match_priority;
  		  best_count = 0;
  		}
  	      if (match_priority <= best_match)
  		{
  		  /* This format checks out as ok!  */
  		  right_targ = temp;
  		  best_count++;
  		}
  	    }
  	  else
  	    {
  	      /* An archive with no armap or objects of the wrong
  		 type.  We want this target to match if we get no
  		 better matches.  */
  	      if (ar_right_targ != bfd_default_vector[0])
  		ar_right_targ = *target;
  	      if (matching_vector)
  		matching_vector[ar_match_index] = *target;
  	      ar_match_index++;
  	    }
  
  	  if (preserve_match.marker == NULL)
  	    {
  	      match_targ = temp;
  	      if (!bfd_preserve_save (abfd, &preserve_match))
  		goto err_ret;
  	    }
  	}
      }
  
    if (best_count == 1)
      match_count = 1;
  
    if (match_count == 0)
      {
        /* Try partial matches.  */
        right_targ = ar_right_targ;
  
        if (right_targ == bfd_default_vector[0])
  	{
  	  match_count = 1;
  	}
        else
  	{
  	  match_count = ar_match_index - _bfd_target_vector_entries;
  
  	  if (matching_vector && match_count > 1)
  	    memcpy (matching_vector,
  		    matching_vector + _bfd_target_vector_entries,
  		    sizeof (*matching_vector) * match_count);
  	}
      }
  
    /* We have more than one equally good match.  If any of the best
       matches is a target in config.bfd targ_defvec or targ_selvecs,
       choose it.  */
    if (match_count > 1)
      {
        const bfd_target * const *assoc = bfd_associated_vector;
  
        while ((right_targ = *assoc++) != NULL)
  	{
  	  int i = match_count;
  
  	  while (--i >= 0)
  	    if (matching_vector[i] == right_targ
  		&& right_targ->match_priority <= best_match)
  	      break;
  
  	  if (i >= 0)
  	    {
  	      match_count = 1;
  	      break;
  	    }
  	}
      }
  
    /* We still have more than one equally good match, and at least some
       of the targets support match priority.  Choose the first of the
       best matches.  */
    if (matching_vector && match_count > 1 && best_count != match_count)
      {
        int i;
  
        for (i = 0; i < match_count; i++)
  	{
  	  right_targ = matching_vector[i];
  	  if (right_targ->match_priority <= best_match)
  	    break;
  	}
        match_count = 1;
      }
  
    /* There is way too much undoing of half-known state here.  We
       really shouldn't iterate on live bfd's.  Note that saving the
       whole bfd and restoring it would be even worse; the first thing
       you notice is that the cached bfd file position gets out of sync.  */
    if (preserve_match.marker != NULL)
      bfd_preserve_restore (abfd, &preserve_match);
  
    if (match_count == 1)
      {
        abfd->xvec = right_targ;
        /* If we come out of the loop knowing that the last target that
  	 matched is the one we want, then ABFD should still be in a usable
  	 state (except possibly for XVEC).  This is not just an
  	 optimisation.  In the case of plugins a match against the
  	 plugin target can result in the bfd being changed such that
  	 it no longer matches the plugin target, nor will it match
  	 RIGHT_TARG again.  */
        if (match_targ != right_targ)
  	{
  	  bfd_reinit (abfd, initial_section_id);
  	  bfd_release (abfd, preserve.marker);
  	  if (bfd_seek (abfd, (file_ptr) 0, SEEK_SET) != 0)
  	    goto err_ret;
  	  match_targ = BFD_SEND_FMT (abfd, _bfd_check_format, (abfd));
  	  BFD_ASSERT (match_targ != NULL);
  	}
  
      ok_ret:
        /* If the file was opened for update, then `output_has_begun'
  	 some time ago when the file was created.  Do not recompute
  	 sections sizes or alignments in _bfd_set_section_contents.
  	 We can not set this flag until after checking the format,
  	 because it will interfere with creation of BFD sections.  */
        if (abfd->direction == both_direction)
  	abfd->output_has_begun = TRUE;
  
        if (matching_vector)
  	free (matching_vector);
        if (preserve_match.marker != NULL)
  	bfd_preserve_finish (abfd, &preserve_match);
        bfd_preserve_finish (abfd, &preserve);
  
        /* File position has moved, BTW.  */
        return TRUE;
      }
  
    if (match_count == 0)
      {
      err_unrecog:
        bfd_set_error (bfd_error_file_not_recognized);
      err_ret:
        abfd->xvec = save_targ;
        abfd->format = bfd_unknown;
        if (matching_vector)
  	free (matching_vector);
        if (preserve_match.marker != NULL)
  	bfd_preserve_finish (abfd, &preserve_match);
        bfd_preserve_restore (abfd, &preserve);
        return FALSE;
      }
  
    /* Restore original target type and format.  */
    abfd->xvec = save_targ;
    abfd->format = bfd_unknown;
    bfd_set_error (bfd_error_file_ambiguously_recognized);
  
    if (matching)
      {
        *matching = (char **) matching_vector;
        matching_vector[match_count] = NULL;
        /* Return target names.  This is a little nasty.  Maybe we
  	 should do another bfd_malloc?  */
        while (--match_count >= 0)
  	{
  	  const char *name = matching_vector[match_count]->name;
  	  *(const char **) &matching_vector[match_count] = name;
  	}
      }
    else if (matching_vector)
      free (matching_vector);
    if (preserve_match.marker != NULL)
      bfd_preserve_finish (abfd, &preserve_match);
    bfd_preserve_restore (abfd, &preserve);
    return FALSE;
  }
  
  /*
  FUNCTION
  	bfd_set_format
  
  SYNOPSIS
  	bfd_boolean bfd_set_format (bfd *abfd, bfd_format format);
  
  DESCRIPTION
  	This function sets the file format of the BFD @var{abfd} to the
  	format @var{format}. If the target set in the BFD does not
  	support the format requested, the format is invalid, or the BFD
  	is not open for writing, then an error occurs.
  */
  
  bfd_boolean
  bfd_set_format (bfd *abfd, bfd_format format)
  {
    if (bfd_read_p (abfd)
        || (unsigned int) abfd->format >= (unsigned int) bfd_type_end)
      {
        bfd_set_error (bfd_error_invalid_operation);
        return FALSE;
      }
  
    if (abfd->format != bfd_unknown)
      return abfd->format == format;
  
    /* Presume the answer is yes.  */
    abfd->format = format;
  
    if (!BFD_SEND_FMT (abfd, _bfd_set_format, (abfd)))
      {
        abfd->format = bfd_unknown;
        return FALSE;
      }
  
    return TRUE;
  }
  
  /*
  FUNCTION
  	bfd_format_string
  
  SYNOPSIS
  	const char *bfd_format_string (bfd_format format);
  
  DESCRIPTION
  	Return a pointer to a const string
  	<<invalid>>, <<object>>, <<archive>>, <<core>>, or <<unknown>>,
  	depending upon the value of @var{format}.
  */
  
  const char *
  bfd_format_string (bfd_format format)
  {
    if (((int) format < (int) bfd_unknown)
        || ((int) format >= (int) bfd_type_end))
      return "invalid";
  
    switch (format)
      {
      case bfd_object:
        return "object";		/* Linker/assembler/compiler output.  */
      case bfd_archive:
        return "archive";		/* Object archive file.  */
      case bfd_core:
        return "core";		/* Core dump.  */
      default:
        return "unknown";
      }
  }
  