1/* Get note information at the supplied offset.
2   Copyright (C) 2007, 2014, 2015 Red Hat, Inc.
3   This file is part of elfutils.
4
5   This file is free software; you can redistribute it and/or modify
6   it under the terms of either
7
8     * the GNU Lesser General Public License as published by the Free
9       Software Foundation; either version 3 of the License, or (at
10       your option) any later version
11
12   or
13
14     * the GNU General Public License as published by the Free
15       Software Foundation; either version 2 of the License, or (at
16       your option) any later version
17
18   or both in parallel, as here.
19
20   elfutils is distributed in the hope that it will be useful, but
21   WITHOUT ANY WARRANTY; without even the implied warranty of
22   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
23   General Public License for more details.
24
25   You should have received copies of the GNU General Public License and
26   the GNU Lesser General Public License along with this program.  If
27   not, see <http://www.gnu.org/licenses/>.  */
28
29#ifdef HAVE_CONFIG_H
30# include <config.h>
31#endif
32
33#include <assert.h>
34#include <gelf.h>
35#include <string.h>
36
37#include "libelfP.h"
38
39size_t
40gelf_getnote (Elf_Data *data, size_t offset, GElf_Nhdr *result,
41	      size_t *name_offset, size_t *desc_offset)
42{
43  if (data == NULL)
44    return 0;
45
46  if (unlikely (data->d_type != ELF_T_NHDR))
47    {
48      __libelf_seterrno (ELF_E_INVALID_HANDLE);
49      return 0;
50    }
51
52  /* It's easy to handle this type.  It has the same size for 32 and
53     64 bit objects.  */
54  assert (sizeof (GElf_Nhdr) == sizeof (Elf32_Nhdr));
55  assert (sizeof (GElf_Nhdr) == sizeof (Elf64_Nhdr));
56
57  rwlock_rdlock (((Elf_Data_Scn *) data)->s->elf->lock);
58
59  /* The data is already in the correct form.  Just make sure the
60     offset is OK.  */
61  if (unlikely (offset > data->d_size
62		|| data->d_size - offset < sizeof (GElf_Nhdr)))
63    {
64      __libelf_seterrno (ELF_E_OFFSET_RANGE);
65      offset = 0;
66    }
67  else
68    {
69      const GElf_Nhdr *n = data->d_buf + offset;
70      offset += sizeof *n;
71
72      /* Include padding.  Check below for overflow.  */
73      GElf_Word namesz = NOTE_ALIGN (n->n_namesz);
74      GElf_Word descsz = NOTE_ALIGN (n->n_descsz);
75
76      if (unlikely (offset > data->d_size
77		    || data->d_size - offset < namesz
78		    || (namesz == 0 && n->n_namesz != 0)))
79	offset = 0;
80      else
81	{
82	  *name_offset = offset;
83	  offset += namesz;
84	  if (unlikely (offset > data->d_size
85			|| data->d_size - offset < descsz
86			|| (descsz == 0 && n->n_descsz != 0)))
87	    offset = 0;
88	  else
89	    {
90	      *desc_offset = offset;
91	      offset += descsz;
92	      *result = *n;
93	    }
94	}
95    }
96
97  rwlock_unlock (((Elf_Data_Scn *) data)->s->elf->lock);
98
99  return offset;
100}
101