/* Get note information at the supplied offset.

   Copyright (C) 2007, 2014, 2015, 2018 Red Hat, Inc.

   This file is part of elfutils.

   This file is free software; you can redistribute it and/or modify

   it under the terms of either

     * the GNU Lesser General Public License as published by the Free

       Software Foundation; either version 3 of the License, or (at

       your option) any later version

   or

     * 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

   or both in parallel, as here.

   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 copies of the GNU General Public License and

   the GNU Lesser General Public License along with this program.  If

   not, see <http://www.gnu.org/licenses/>.  */

#ifdef HAVE_CONFIG_H

# include <config.h>

#endif

#include <assert.h>

#include <gelf.h>

#include <string.h>

#include "libelfP.h"

size_t

gelf_getnote (Elf_Data *data, size_t offset, GElf_Nhdr *result,

	      size_t *name_offset, size_t *desc_offset)

{

  if (data == NULL)

    return 0;

  if (unlikely (data->d_type != ELF_T_NHDR && data->d_type != ELF_T_NHDR8))

    {

      __libelf_seterrno (ELF_E_INVALID_HANDLE);

      return 0;

    }

  /* It's easy to handle this type.  It has the same size for 32 and

     64 bit objects.  */

  assert (sizeof (GElf_Nhdr) == sizeof (Elf32_Nhdr));

  assert (sizeof (GElf_Nhdr) == sizeof (Elf64_Nhdr));

  rwlock_rdlock (((Elf_Data_Scn *) data)->s->elf->lock);

  /* The data is already in the correct form.  Just make sure the

     offset is OK.  */

  if (unlikely (offset > data->d_size

		|| data->d_size - offset < sizeof (GElf_Nhdr)))

    {

      __libelf_seterrno (ELF_E_OFFSET_RANGE);

      offset = 0;

    }

  else

    {

      const GElf_Nhdr *n = data->d_buf + offset;

      offset += sizeof *n;

      if (offset > data->d_size)

	offset = 0;

      else

	{

	  /* This is slightly tricky, offset is guaranteed to be 4

	     byte aligned, which is what we need for the name_offset.

	     And normally desc_offset is also 4 byte aligned, but not

	     for GNU Property notes, then it should be 8.  So align

	     the offset, after adding the namesz, and include padding

	     in descsz to get to the end.  */

	  *name_offset = offset;

	  if (n->n_namesz > data->d_size

	      || offset > data->d_size - n->n_namesz)

	    offset = 0;

	  else

	    {

	      offset += n->n_namesz;

	      /* Include padding.  Check below for overflow.  */

	      GElf_Word descsz = (data->d_type == ELF_T_NHDR8

				  ? NOTE_ALIGN8 (n->n_descsz)

				  : NOTE_ALIGN4 (n->n_descsz));

	      if (data->d_type == ELF_T_NHDR8)

		offset = NOTE_ALIGN8 (offset);

	      else

		offset = NOTE_ALIGN4 (offset);

	      if (unlikely (offset > data->d_size

			    || data->d_size - offset < descsz

			    || (descsz == 0 && n->n_descsz != 0)))

		offset = 0;

	      else

		{

		  *desc_offset = offset;

		  offset += descsz;

		  *result = *n;

		}

	    }

	}

    }

  rwlock_unlock (((Elf_Data_Scn *) data)->s->elf->lock);

  return offset;

}