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 *
gelf_getdyn(Elf_Data * data,int ndx,GElf_Dyn * dst)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 }
109