1/*	$NetBSD: libelf_checksum.c,v 1.5 2024/03/03 17:37:34 christos Exp $	*/
2
3/*-
4 * Copyright (c) 2006,2008 Joseph Koshy
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29#include <sys/cdefs.h>
30
31#include <gelf.h>
32
33#include "_libelf.h"
34
35__RCSID("$NetBSD: libelf_checksum.c,v 1.5 2024/03/03 17:37:34 christos Exp $");
36ELFTC_VCSID("Id: libelf_checksum.c 3977 2022-05-01 06:45:34Z jkoshy");
37
38static unsigned long
39_libelf_sum(unsigned long c, const unsigned char *s, size_t size)
40{
41	if (s == NULL || size == 0)
42		return (c);
43
44	while (size--)
45		c += *s++;
46
47	return (c);
48}
49
50long
51_libelf_checksum(Elf *e, int elfclass)
52{
53	size_t shn;
54	Elf_Scn *scn;
55	Elf_Data *d;
56	unsigned long checksum;
57	GElf_Ehdr eh;
58	GElf_Shdr shdr;
59
60	if (e == NULL) {
61		LIBELF_SET_ERROR(ARGUMENT, 0);
62		return (0L);
63	}
64
65	if (e->e_class != elfclass) {
66		LIBELF_SET_ERROR(CLASS, 0);
67		return (0L);
68	}
69
70	if (gelf_getehdr(e, &eh) == NULL)
71		return (0);
72
73	/*
74	 * Iterate over all sections in the ELF file, computing the
75	 * checksum along the way.
76	 *
77	 * The first section is always SHN_UNDEF and can be skipped.
78	 * Non-allocatable sections are skipped, as are sections that
79	 * could be affected by utilities such as strip(1).
80	 */
81
82	checksum = 0;
83	for (shn = 1; shn < e->e_u.e_elf.e_nscn; shn++) {
84		if ((scn = elf_getscn(e, shn)) == NULL)
85			return (0);
86		if (gelf_getshdr(scn, &shdr) == NULL)
87			return (0);
88		if ((shdr.sh_flags & SHF_ALLOC) == 0 ||
89		    shdr.sh_type == SHT_DYNAMIC ||
90		    shdr.sh_type == SHT_DYNSYM)
91			continue;
92
93		d = NULL;
94		while ((d = elf_rawdata(scn, d)) != NULL)
95			checksum = _libelf_sum(checksum,
96			    (unsigned char *) d->d_buf, (size_t) d->d_size);
97	}
98
99	/*
100	 * Return a 16-bit checksum compatible with Solaris.
101	 */
102	return (long) (((checksum >> 16) & 0xFFFFUL) + (checksum & 0xFFFFUL));
103}
104