1 /*-
2 * Copyright (c) 2006 Joseph Koshy
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27 #include <sys/cdefs.h>
28 __FBSDID("$FreeBSD$");
29
30 #include <gelf.h>
31
32 #include "_libelf.h"
33
34 static unsigned long
_libelf_sum(unsigned long c,const unsigned char * s,size_t size)35 _libelf_sum(unsigned long c, const unsigned char *s, size_t size)
36 {
37 if (s == NULL || size == 0)
38 return (c);
39
40 while (size--)
41 c += *s++;
42
43 return (c);
44 }
45
46 unsigned long
_libelf_checksum(Elf * e,int elfclass)47 _libelf_checksum(Elf *e, int elfclass)
48 {
49 size_t shn;
50 Elf_Scn *scn;
51 Elf_Data *d;
52 unsigned long checksum;
53 GElf_Ehdr eh;
54 GElf_Shdr shdr;
55
56 if (e == NULL) {
57 LIBELF_SET_ERROR(ARGUMENT, 0);
58 return (0L);
59 }
60
61 if (e->e_class != elfclass) {
62 LIBELF_SET_ERROR(CLASS, 0);
63 return (0L);
64 }
65
66 if (gelf_getehdr(e, &eh) == NULL)
67 return (0);
68
69 /*
70 * Iterate over all sections in the ELF file, computing the
71 * checksum along the way.
72 *
73 * The first section is always SHN_UNDEF and can be skipped.
74 * Non-allocatable sections are skipped, as are sections that
75 * could be affected by utilities such as strip(1).
76 */
77
78 checksum = 0;
79 for (shn = 1; shn < e->e_u.e_elf.e_nscn; shn++) {
80 if ((scn = elf_getscn(e, shn)) == NULL)
81 return (0);
82 if (gelf_getshdr(scn, &shdr) == NULL)
83 return (0);
84 if ((shdr.sh_flags & SHF_ALLOC) == 0 ||
85 shdr.sh_type == SHT_DYNAMIC ||
86 shdr.sh_type == SHT_DYNSYM)
87 continue;
88
89 d = NULL;
90 while ((d = elf_rawdata(scn, d)) != NULL)
91 checksum = _libelf_sum(checksum,
92 (unsigned char *) d->d_buf, d->d_size);
93 }
94
95 /*
96 * Return a 16-bit checksum compatible with Solaris.
97 */
98 return (((checksum >> 16) & 0xFFFFUL) + (checksum & 0xFFFFUL));
99 }
100