libelf_checksum.c revision 276371 
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 <sys/cdefs.h>
28
29#include <gelf.h>
30
31#include "_libelf.h"
32
33ELFTC_VCSID("$Id: libelf_checksum.c 3003 2014-03-22 07:43:10Z jkoshy $");
34
35static unsigned long
36_libelf_sum(unsigned long c, const unsigned char *s, size_t size)
37{
38	if (s == NULL || size == 0)
39		return (c);
40
41	while (size--)
42		c += *s++;
43
44	return (c);
45}
46
47long
48_libelf_checksum(Elf *e, int elfclass)
49{
50	size_t shn;
51	Elf_Scn *scn;
52	Elf_Data *d;
53	unsigned long checksum;
54	GElf_Ehdr eh;
55	GElf_Shdr shdr;
56
57	if (e == NULL) {
58		LIBELF_SET_ERROR(ARGUMENT, 0);
59		return (0L);
60	}
61
62	if (e->e_class != elfclass) {
63		LIBELF_SET_ERROR(CLASS, 0);
64		return (0L);
65	}
66
67	if (gelf_getehdr(e, &eh) == NULL)
68		return (0);
69
70	/*
71	 * Iterate over all sections in the ELF file, computing the
72	 * checksum along the way.
73	 *
74	 * The first section is always SHN_UNDEF and can be skipped.
75	 * Non-allocatable sections are skipped, as are sections that
76	 * could be affected by utilities such as strip(1).
77	 */
78
79	checksum = 0;
80	for (shn = 1; shn < e->e_u.e_elf.e_nscn; shn++) {
81		if ((scn = elf_getscn(e, shn)) == NULL)
82			return (0);
83		if (gelf_getshdr(scn, &shdr) == NULL)
84			return (0);
85		if ((shdr.sh_flags & SHF_ALLOC) == 0 ||
86		    shdr.sh_type == SHT_DYNAMIC ||
87		    shdr.sh_type == SHT_DYNSYM)
88			continue;
89
90		d = NULL;
91		while ((d = elf_rawdata(scn, d)) != NULL)
92			checksum = _libelf_sum(checksum,
93			    (unsigned char *) d->d_buf, (size_t) d->d_size);
94	}
95
96	/*
97	 * Return a 16-bit checksum compatible with Solaris.
98	 */
99	return (long) (((checksum >> 16) & 0xFFFFUL) + (checksum & 0xFFFFUL));
100}
101