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
34static unsigned long
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
46unsigned long
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