1 /* $NetBSD: libelf_checksum.c,v 1.2 2014/03/09 16:58:04 christos Exp $ */
2
3 /*-
4 * Copyright (c) 2006,2008 Joseph Koshy
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #include <sys/cdefs.h>
30
31 #include <gelf.h>
32
33 #include "_libelf.h"
34
35 __RCSID("$NetBSD: libelf_checksum.c,v 1.2 2014/03/09 16:58:04 christos Exp $");
36 ELFTC_VCSID("Id: libelf_checksum.c 2225 2011-11-26 18:55:54Z jkoshy ");
37
38 static unsigned long
_libelf_sum(unsigned long c,const unsigned char * s,size_t size)39 _libelf_sum(unsigned long c, const unsigned char *s, size_t size)
40 {
41 if (s == NULL || size == 0)
42 return (c);
43
44 while (size--)
45 c += *s++;
46
47 return (c);
48 }
49
50 unsigned long
_libelf_checksum(Elf * e,int elfclass)51 _libelf_checksum(Elf *e, int elfclass)
52 {
53 size_t shn;
54 Elf_Scn *scn;
55 Elf_Data *d;
56 unsigned long checksum;
57 GElf_Ehdr eh;
58 GElf_Shdr shdr;
59
60 if (e == NULL) {
61 LIBELF_SET_ERROR(ARGUMENT, 0);
62 return (0L);
63 }
64
65 if (e->e_class != elfclass) {
66 LIBELF_SET_ERROR(CLASS, 0);
67 return (0L);
68 }
69
70 if (gelf_getehdr(e, &eh) == NULL)
71 return (0);
72
73 /*
74 * Iterate over all sections in the ELF file, computing the
75 * checksum along the way.
76 *
77 * The first section is always SHN_UNDEF and can be skipped.
78 * Non-allocatable sections are skipped, as are sections that
79 * could be affected by utilities such as strip(1).
80 */
81
82 checksum = 0;
83 for (shn = 1; shn < e->e_u.e_elf.e_nscn; shn++) {
84 if ((scn = elf_getscn(e, shn)) == NULL)
85 return (0);
86 if (gelf_getshdr(scn, &shdr) == NULL)
87 return (0);
88 if ((shdr.sh_flags & SHF_ALLOC) == 0 ||
89 shdr.sh_type == SHT_DYNAMIC ||
90 shdr.sh_type == SHT_DYNSYM)
91 continue;
92
93 d = NULL;
94 while ((d = elf_rawdata(scn, d)) != NULL)
95 checksum = _libelf_sum(checksum,
96 (unsigned char *) d->d_buf, d->d_size);
97 }
98
99 /*
100 * Return a 16-bit checksum compatible with Solaris.
101 */
102 return (((checksum >> 16) & 0xFFFFUL) + (checksum & 0xFFFFUL));
103 }
104