xref: /external/elfutils/libelf/gelf_getdyn.c

/* Get information from dynamic table at the given index.
   Copyright (C) 2000, 2001, 2002 Red Hat, Inc.
   This file is part of Red Hat elfutils.
   Written by Ulrich Drepper <drepper@redhat.com>, 2000.

   Red Hat elfutils 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; version 2 of the License.

   Red Hat elfutils 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 Red Hat elfutils; if not, write to the Free Software Foundation,
   Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301 USA.

   In addition, as a special exception, Red Hat, Inc. gives You the
   additional right to link the code of Red Hat elfutils with code licensed
   under any Open Source Initiative certified open source license
   (http://www.opensource.org/licenses/index.php) which requires the
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   those well defined interfaces identified in the file named EXCEPTION
   found in the source code files (the "Approved Interfaces").  The files
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   Red Hat's grant of this exception is conditioned upon your not adding
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   exception, please contact Red Hat.  You must obey the GNU General Public
   License in all respects for all of the Red Hat elfutils code and other
   code used in conjunction with Red Hat elfutils except the Non-GPL Code
   covered by this exception.  If you modify this file, you may extend this
   exception to your version of the file, but you are not obligated to do
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   you must delete this exception statement from your version and license
   this file solely under the GPL without exception.

   Red Hat elfutils is an included package of the Open Invention Network.
   An included package of the Open Invention Network is a package for which
   Open Invention Network licensees cross-license their patents.  No patent
   license is granted, either expressly or impliedly, by designation as an
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#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include <assert.h>
#include <gelf.h>
#include <string.h>

#include "libelfP.h"


GElf_Dyn *
gelf_getdyn (data, ndx, dst)
     Elf_Data *data;
     int ndx;
     GElf_Dyn *dst;
{
  Elf_Data_Scn *data_scn = (Elf_Data_Scn *) data;
  GElf_Dyn *result = NULL;
  Elf *elf;

  if (data_scn == NULL)
    return NULL;

  if (unlikely (data_scn->d.d_type != ELF_T_DYN))
    {
      __libelf_seterrno (ELF_E_INVALID_HANDLE);
      return NULL;
    }

  elf = data_scn->s->elf;

  rwlock_rdlock (elf->lock);

  /* This is the one place where we have to take advantage of the fact
     that an `Elf_Data' pointer is also a pointer to `Elf_Data_Scn'.
     The interface is broken so that it requires this hack.  */
  if (elf->class == ELFCLASS32)
    {
      Elf32_Dyn *src;

      /* Here it gets a bit more complicated.  The format of the symbol
	 table entries has to be adopted.  The user better has provided
	 a buffer where we can store the information.  While copying the
	 data we are converting the format.  */
      if (unlikely ((ndx + 1) * sizeof (Elf32_Dyn) > data_scn->d.d_size))
	{
	  __libelf_seterrno (ELF_E_INVALID_INDEX);
	  goto out;
	}

      src = &((Elf32_Dyn *) data_scn->d.d_buf)[ndx];

      /* This might look like a simple copy operation but it's
	 not.  There are zero- and sign-extensions going on.  */
      dst->d_tag = src->d_tag;
      /* It OK to copy `d_val' since `d_ptr' has the same size.  */
      dst->d_un.d_val = src->d_un.d_val;
    }
  else
    {
      /* If this is a 64 bit object it's easy.  */
      assert (sizeof (GElf_Dyn) == sizeof (Elf64_Dyn));

      /* The data is already in the correct form.  Just make sure the
	 index is OK.  */
      if (unlikely ((ndx + 1) * sizeof (GElf_Dyn) > data_scn->d.d_size))
	{
	  __libelf_seterrno (ELF_E_INVALID_INDEX);
	  goto out;
	}

      *dst = ((GElf_Dyn *) data_scn->d.d_buf)[ndx];
    }

  result = dst;

 out:
  rwlock_unlock (elf->lock);

  return result;
}