external/bsd/libelf/dist/libelf_checksum.c

   1 /*      $NetBSD$        */
   2
   3 /*-
   4  * Copyright (c) 2006 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 /* __FBSDID("$FreeBSD: src/lib/libelf/libelf_checksum.c,v 1.2.10.1.2.1 2009/10/25 01:10:29 kensmith Exp $"); */
  31
  32 #include <gelf.h>
  33
  34 #include "_libelf.h"
  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 unsigned 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, d->d_size);
  95         }
  96
  97         /*
  98          * Return a 16-bit checksum compatible with Solaris.
  99          */
 100         return (((checksum >> 16) & 0xFFFFUL) + (checksum & 0xFFFFUL));
 101 }