libelf_checksum.c revision 280932 
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
31ELFTC_VCSID("$Id: libelf_checksum.c 3174 2015-03-27 17:13:41Z emaste $");
32
33static unsigned long
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
45long
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