1 /* Compute simple checksum from permanent parts of the ELF file.
2 Copyright (C) 2002, 2003, 2004, 2005, 2009, 2015 Red Hat, Inc.
3 This file is part of elfutils.
4 Written by Ulrich Drepper <drepper@redhat.com>, 2002.
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 <endian.h>
36 #include <stdbool.h>
37 #include <stddef.h>
38 #include <string.h>
39
40 #include "gelf.h"
41 #include "libelfP.h"
42 #include "elf-knowledge.h"
43
44 #ifndef LIBELFBITS
45 # define LIBELFBITS 32
46 #endif
47
48
49 #define process_block(crc, data) \
50 __libelf_crc32 (crc, data->d_buf, data->d_size)
51
52
53 long int
elfw2(LIBELFBITS,checksum)54 elfw2(LIBELFBITS,checksum) (Elf *elf)
55 {
56 size_t shstrndx;
57 Elf_Scn *scn;
58 long int result = 0;
59 unsigned char *ident;
60 bool same_byte_order;
61
62 if (elf == NULL)
63 return -1l;
64
65 /* Find the section header string table. */
66 if (INTUSE(elf_getshdrstrndx) (elf, &shstrndx) < 0)
67 {
68 /* This can only happen if the ELF handle is not for real. */
69 __libelf_seterrno (ELF_E_INVALID_HANDLE);
70 return -1l;
71 }
72
73 /* Determine whether the byte order of the file and that of the host
74 is the same. */
75 ident = elf->state.ELFW(elf,LIBELFBITS).ehdr->e_ident;
76 same_byte_order = ((ident[EI_DATA] == ELFDATA2LSB
77 && __BYTE_ORDER == __LITTLE_ENDIAN)
78 || (ident[EI_DATA] == ELFDATA2MSB
79 && __BYTE_ORDER == __BIG_ENDIAN));
80
81 /* If we don't have native byte order, we will likely need to
82 convert the data with xlate functions. We do it upfront instead
83 of relocking mid-iteration. */
84 if (!likely (same_byte_order))
85 rwlock_wrlock (elf->lock);
86 else
87 rwlock_rdlock (elf->lock);
88
89 /* Iterate over all sections to find those which are not strippable. */
90 scn = NULL;
91 while ((scn = INTUSE(elf_nextscn) (elf, scn)) != NULL)
92 {
93 GElf_Shdr shdr_mem;
94 GElf_Shdr *shdr;
95 Elf_Data *data;
96
97 /* Get the section header. */
98 shdr = INTUSE(gelf_getshdr) (scn, &shdr_mem);
99 if (shdr == NULL)
100 {
101 __libelf_seterrno (ELF_E_INVALID_SECTION_HEADER);
102 result = -1l;
103 goto out;
104 }
105
106 if (SECTION_STRIP_P (shdr,
107 INTUSE(elf_strptr) (elf, shstrndx, shdr->sh_name),
108 true))
109 /* The section can be stripped. Don't use it. */
110 continue;
111
112 /* Do not look at NOBITS sections. */
113 if (shdr->sh_type == SHT_NOBITS)
114 continue;
115
116 /* To compute the checksum we need to get to the data. For
117 repeatable results we must use the external format. The data
118 we get with 'elf'getdata' might be changed for endianess
119 reasons. Therefore we use 'elf_rawdata' if possible. But
120 this function can fail if the data was constructed by the
121 program. In this case we have to use 'elf_getdata' and
122 eventually convert the data to the external format. */
123 data = INTUSE(elf_rawdata) (scn, NULL);
124 if (data != NULL)
125 {
126 /* The raw data is available. */
127 result = process_block (result, data);
128
129 /* Maybe the user added more data. These blocks cannot be
130 read using 'elf_rawdata'. Simply proceed with looking
131 for more data block with 'elf_getdata'. */
132 }
133
134 /* Iterate through the list of data blocks. */
135 while ((data = INTUSE(elf_getdata) (scn, data)) != NULL)
136 /* If the file byte order is the same as the host byte order
137 process the buffer directly. If the data is just a stream
138 of bytes which the library will not convert we can use it
139 as well. */
140 if (likely (same_byte_order) || data->d_type == ELF_T_BYTE)
141 result = process_block (result, data);
142 else
143 {
144 /* Convert the data to file byte order. */
145 if (INTUSE(elfw2(LIBELFBITS,xlatetof)) (data, data, ident[EI_DATA])
146 == NULL)
147 {
148 result = -1l;
149 goto out;
150 }
151
152 result = process_block (result, data);
153
154 /* And convert it back. */
155 if (INTUSE(elfw2(LIBELFBITS,xlatetom)) (data, data, ident[EI_DATA])
156 == NULL)
157 {
158 result = -1l;
159 goto out;
160 }
161 }
162 }
163
164 out:
165 rwlock_unlock (elf->lock);
166 return result;
167 }
168 INTDEF(elfw2(LIBELFBITS,checksum))
169