libelf/gelf_getsymshndx.c

/* Get symbol information and separate section index from symbol 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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   this exception must only link to the code of Red Hat elfutils through
   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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   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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   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_Sym *
gelf_getsymshndx (symdata, shndxdata, ndx, dst, dstshndx)
     Elf_Data *symdata;
     Elf_Data *shndxdata;
     int ndx;
     GElf_Sym *dst;
     Elf32_Word *dstshndx;
{
  Elf_Data_Scn *symdata_scn = (Elf_Data_Scn *) symdata;
  Elf_Data_Scn *shndxdata_scn = (Elf_Data_Scn *) shndxdata;
  GElf_Sym *result = NULL;
  Elf32_Word shndx = 0;

  if (symdata == NULL)
    return NULL;

  if (unlikely (symdata->d_type != ELF_T_SYM)
      || (likely (shndxdata_scn != NULL)
	  && unlikely (shndxdata->d_type != ELF_T_WORD)))
    {
      __libelf_seterrno (ELF_E_INVALID_HANDLE);
      return NULL;
    }

  rwlock_rdlock (symdata_scn->s->elf->lock);

  /* The user is not required to pass a data descriptor for an extended
     section index table.  */
  if (likely (shndxdata_scn != NULL))
    {
      if (unlikely ((ndx + 1) * sizeof (Elf32_Word) > shndxdata_scn->d.d_size))
	{
	  __libelf_seterrno (ELF_E_INVALID_INDEX);
	  goto out;
	}

      shndx = ((Elf32_Word *) shndxdata_scn->d.d_buf)[ndx];
    }

  /* 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 (symdata_scn->s->elf->class == ELFCLASS32)
    {
      Elf32_Sym *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_Sym) > symdata->d_size))
	{
	  __libelf_seterrno (ELF_E_INVALID_INDEX);
	  goto out;
	}

      src = &((Elf32_Sym *) symdata->d_buf)[ndx];

      /* This might look like a simple copy operation but it's
	 not.  There are zero- and sign-extensions going on.  */
#define COPY(name) \
      dst->name = src->name
      COPY (st_name);
      /* Please note that we can simply copy the `st_info' element since
	 the definitions of ELFxx_ST_BIND and ELFxx_ST_TYPE are the same
	 for the 64 bit variant.  */
      COPY (st_info);
      COPY (st_other);
      COPY (st_shndx);
      COPY (st_value);
      COPY (st_size);
    }
  else
    {
      /* If this is a 64 bit object it's easy.  */
      assert (sizeof (GElf_Sym) == sizeof (Elf64_Sym));

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

      *dst = ((GElf_Sym *) symdata->d_buf)[ndx];
    }

  /* Now we can store the section index.  */
  if (dstshndx != NULL)
    *dstshndx = shndx;

  result = dst;

 out:
  rwlock_unlock (symdata_scn->s->elf->lock);

  return result;
}