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  
 33  ELFTC_VCSID("$Id$");
 34  
 35  static 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  
 47  long
 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  }