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