lib/libelf/libelf_checksum.c

   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 LIBELF_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 unsigned 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, d->d_size);
  94         }
  95
  96         /*
  97          * Return a 16-bit checksum compatible with Solaris.
  98          */
  99         return (((checksum >> 16) & 0xFFFFUL) + (checksum & 0xFFFFUL));
 100 }