src/libelf/gelf_getauxv.c

/* Get information from auxiliary vector at the given index.
   Copyright (C) 2007 Red Hat, Inc.
   This file is part of Red Hat elfutils.

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   it under the terms of the GNU General Public License as published by the
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   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
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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_auxv_t *
gelf_getauxv (data, ndx, dst)
     Elf_Data *data;
     int ndx;
     GElf_auxv_t *dst;
{
  Elf_Data_Scn *data_scn = (Elf_Data_Scn *) data;
  GElf_auxv_t *result = NULL;
  Elf *elf;

  if (data_scn == NULL)
    return NULL;

  if (unlikely (data_scn->d.d_type != ELF_T_AUXV))
    {
      __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_auxv_t *src;

      /* Here it gets a bit more complicated.  The format of the vector
	 entries has to be converted.  The user better have provided a
	 buffer where we can store the information.  While copying the data
	 we convert the format.  */
      if (unlikely ((ndx + 1) * sizeof (Elf32_auxv_t) > data_scn->d.d_size))
	{
	  __libelf_seterrno (ELF_E_INVALID_INDEX);
	  goto out;
	}

      src = &((Elf32_auxv_t *) 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->a_type = src->a_type;
      dst->a_un.a_val = src->a_un.a_val;
    }
  else
    {
      /* If this is a 64 bit object it's easy.  */
      assert (sizeof (GElf_auxv_t) == sizeof (Elf64_auxv_t));

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

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

  result = dst;

 out:
  rwlock_unlock (elf->lock);

  return result;
}