1 /*-
2 * Copyright (c) 2006,2008 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 <gelf.h>
28
29 #include "_libelf.h"
30
31 ELFTC_VCSID("$Id: libelf_checksum.c 3174 2015-03-27 17:13:41Z emaste $");
32
33 static unsigned long
_libelf_sum(unsigned long c,const unsigned char * s,size_t size)34 _libelf_sum(unsigned long c, const unsigned char *s, size_t size)
35 {
36 if (s == NULL || size == 0)
37 return (c);
38
39 while (size--)
40 c += *s++;
41
42 return (c);
43 }
44
45 long
_libelf_checksum(Elf * e,int elfclass)46 _libelf_checksum(Elf *e, int elfclass)
47 {
48 size_t shn;
49 Elf_Scn *scn;
50 Elf_Data *d;
51 unsigned long checksum;
52 GElf_Ehdr eh;
53 GElf_Shdr shdr;
54
55 if (e == NULL) {
56 LIBELF_SET_ERROR(ARGUMENT, 0);
57 return (0L);
58 }
59
60 if (e->e_class != elfclass) {
61 LIBELF_SET_ERROR(CLASS, 0);
62 return (0L);
63 }
64
65 if (gelf_getehdr(e, &eh) == NULL)
66 return (0);
67
68 /*
69 * Iterate over all sections in the ELF file, computing the
70 * checksum along the way.
71 *
72 * The first section is always SHN_UNDEF and can be skipped.
73 * Non-allocatable sections are skipped, as are sections that
74 * could be affected by utilities such as strip(1).
75 */
76
77 checksum = 0;
78 for (shn = 1; shn < e->e_u.e_elf.e_nscn; shn++) {
79 if ((scn = elf_getscn(e, shn)) == NULL)
80 return (0);
81 if (gelf_getshdr(scn, &shdr) == NULL)
82 return (0);
83 if ((shdr.sh_flags & SHF_ALLOC) == 0 ||
84 shdr.sh_type == SHT_DYNAMIC ||
85 shdr.sh_type == SHT_DYNSYM)
86 continue;
87
88 d = NULL;
89 while ((d = elf_rawdata(scn, d)) != NULL)
90 checksum = _libelf_sum(checksum,
91 (unsigned char *) d->d_buf, (size_t) d->d_size);
92 }
93
94 /*
95 * Return a 16-bit checksum compatible with Solaris.
96 */
97 return (long) (((checksum >> 16) & 0xFFFFUL) + (checksum & 0xFFFFUL));
98 }
99