libelf/gelf_getdyn.c

   1 /* Get information from dynamic table at the given index.
   2    Copyright (C) 2000, 2001, 2002, 2005, 2009, 2014, 2015 Red Hat, Inc.
   3    This file is part of elfutils.
   4    Written by Ulrich Drepper <drepper@redhat.com>, 2000.
   5
   6    This file is free software; you can redistribute it and/or modify
   7    it under the terms of either
   8
   9      * the GNU Lesser General Public License as published by the Free
  10        Software Foundation; either version 3 of the License, or (at
  11        your option) any later version
  12
  13    or
  14
  15      * the GNU General Public License as published by the Free
  16        Software Foundation; either version 2 of the License, or (at
  17        your option) any later version
  18
  19    or both in parallel, as here.
  20
  21    elfutils is distributed in the hope that it will be useful, but
  22    WITHOUT ANY WARRANTY; without even the implied warranty of
  23    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  24    General Public License for more details.
  25
  26    You should have received copies of the GNU General Public License and
  27    the GNU Lesser General Public License along with this program.  If
  28    not, see <http://www.gnu.org/licenses/>.  */
  29
  30 #ifdef HAVE_CONFIG_H
  31 # include <config.h>
  32 #endif
  33
  34 #include <assert.h>
  35 #include <gelf.h>
  36 #include <string.h>
  37
  38 #include "libelfP.h"
  39
  40
  41 GElf_Dyn *
  42 gelf_getdyn (Elf_Data *data, int ndx, GElf_Dyn *dst)
  43 {
  44   Elf_Data_Scn *data_scn = (Elf_Data_Scn *) data;
  45   GElf_Dyn *result = NULL;
  46   Elf *elf;
  47
  48   if (data_scn == NULL)
  49     return NULL;
  50
  51   if (unlikely (data_scn->d.d_type != ELF_T_DYN))
  52     {
  53       __libelf_seterrno (ELF_E_INVALID_HANDLE);
  54       return NULL;
  55     }
  56
  57   elf = data_scn->s->elf;
  58
  59   rwlock_rdlock (elf->lock);
  60
  61   /* This is the one place where we have to take advantage of the fact
  62      that an `Elf_Data' pointer is also a pointer to `Elf_Data_Scn'.
  63      The interface is broken so that it requires this hack.  */
  64   if (elf->class == ELFCLASS32)
  65     {
  66       Elf32_Dyn *src;
  67
  68       /* Here it gets a bit more complicated.  The format of the symbol
  69          table entries has to be adopted.  The user better has provided
  70          a buffer where we can store the information.  While copying the
  71          data we are converting the format.  */
  72       if (INVALID_NDX (ndx, Elf32_Dyn, &data_scn->d))
  73         {
  74           __libelf_seterrno (ELF_E_INVALID_INDEX);
  75           goto out;
  76         }
  77
  78       src = &((Elf32_Dyn *) data_scn->d.d_buf)[ndx];
  79
  80       /* This might look like a simple copy operation but it's
  81          not.  There are zero- and sign-extensions going on.  */
  82       dst->d_tag = src->d_tag;
  83       /* It OK to copy `d_val' since `d_ptr' has the same size.  */
  84       dst->d_un.d_val = src->d_un.d_val;
  85     }
  86   else
  87     {
  88       /* If this is a 64 bit object it's easy.  */
  89       assert (sizeof (GElf_Dyn) == sizeof (Elf64_Dyn));
  90
  91       /* The data is already in the correct form.  Just make sure the
  92          index is OK.  */
  93       if (INVALID_NDX (ndx, GElf_Dyn, &data_scn->d))
  94         {
  95           __libelf_seterrno (ELF_E_INVALID_INDEX);
  96           goto out;
  97         }
  98
  99       *dst = ((GElf_Dyn *) data_scn->d.d_buf)[ndx];
 100     }
 101
 102   result = dst;
 103
 104  out:
 105   rwlock_unlock (elf->lock);
 106
 107   return result;
 108 }