1 /* $NetBSD: libelf_checksum.c,v 1.3 2016/02/20 02:43:42 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 <gelf.h> 30 31 #include "_libelf.h" 32 33 __RCSID("$NetBSD: libelf_checksum.c,v 1.3 2016/02/20 02:43:42 christos Exp $"); 34 ELFTC_VCSID("Id: libelf_checksum.c 3174 2015-03-27 17:13:41Z emaste "); 35 36 static unsigned long 37 _libelf_sum(unsigned long c, const unsigned char *s, size_t size) 38 { 39 if (s == NULL || size == 0) 40 return (c); 41 42 while (size--) 43 c += *s++; 44 45 return (c); 46 } 47 48 long 49 _libelf_checksum(Elf *e, int elfclass) 50 { 51 size_t shn; 52 Elf_Scn *scn; 53 Elf_Data *d; 54 unsigned long checksum; 55 GElf_Ehdr eh; 56 GElf_Shdr shdr; 57 58 if (e == NULL) { 59 LIBELF_SET_ERROR(ARGUMENT, 0); 60 return (0L); 61 } 62 63 if (e->e_class != elfclass) { 64 LIBELF_SET_ERROR(CLASS, 0); 65 return (0L); 66 } 67 68 if (gelf_getehdr(e, &eh) == NULL) 69 return (0); 70 71 /* 72 * Iterate over all sections in the ELF file, computing the 73 * checksum along the way. 74 * 75 * The first section is always SHN_UNDEF and can be skipped. 76 * Non-allocatable sections are skipped, as are sections that 77 * could be affected by utilities such as strip(1). 78 */ 79 80 checksum = 0; 81 for (shn = 1; shn < e->e_u.e_elf.e_nscn; shn++) { 82 if ((scn = elf_getscn(e, shn)) == NULL) 83 return (0); 84 if (gelf_getshdr(scn, &shdr) == NULL) 85 return (0); 86 if ((shdr.sh_flags & SHF_ALLOC) == 0 || 87 shdr.sh_type == SHT_DYNAMIC || 88 shdr.sh_type == SHT_DYNSYM) 89 continue; 90 91 d = NULL; 92 while ((d = elf_rawdata(scn, d)) != NULL) 93 checksum = _libelf_sum(checksum, 94 (unsigned char *) d->d_buf, (size_t) d->d_size); 95 } 96 97 /* 98 * Return a 16-bit checksum compatible with Solaris. 99 */ 100 return (long) (((checksum >> 16) & 0xFFFFUL) + (checksum & 0xFFFFUL)); 101 } 102