1 /* Get note information at the supplied offset.
2 Copyright (C) 2007, 2014, 2015, 2018 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
39 size_t
gelf_getnote(Elf_Data * data,size_t offset,GElf_Nhdr * result,size_t * name_offset,size_t * desc_offset)40 gelf_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 && data->d_type != ELF_T_NHDR8))
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 if (offset > data->d_size)
73 offset = 0;
74 else
75 {
76 /* This is slightly tricky, offset is guaranteed to be 4
77 byte aligned, which is what we need for the name_offset.
78 And normally desc_offset is also 4 byte aligned, but not
79 for GNU Property notes, then it should be 8. So align
80 the offset, after adding the namesz, and include padding
81 in descsz to get to the end. */
82 *name_offset = offset;
83 offset += n->n_namesz;
84 if (offset > data->d_size)
85 offset = 0;
86 else
87 {
88 /* Include padding. Check below for overflow. */
89 GElf_Word descsz = (data->d_type == ELF_T_NHDR8
90 ? NOTE_ALIGN8 (n->n_descsz)
91 : NOTE_ALIGN4 (n->n_descsz));
92
93 if (data->d_type == ELF_T_NHDR8)
94 offset = NOTE_ALIGN8 (offset);
95 else
96 offset = NOTE_ALIGN4 (offset);
97
98 if (unlikely (offset > data->d_size
99 || data->d_size - offset < descsz
100 || (descsz == 0 && n->n_descsz != 0)))
101 offset = 0;
102 else
103 {
104 *desc_offset = offset;
105 offset += descsz;
106 *result = *n;
107 }
108 }
109 }
110 }
111
112 rwlock_unlock (((Elf_Data_Scn *) data)->s->elf->lock);
113
114 return offset;
115 }
116