src/elf32_checksum.c

   1 /* Compute simple checksum from permanent parts of the ELF file.
   2    Copyright (C) 2002, 2003, 2004, 2005, 2009 Red Hat, Inc.
   3    This file is part of elfutils.
   4    Written by Ulrich Drepper <drepper@redhat.com>, 2002.
   5
   6    This file is free software; you can redistribute it and/or modify
   7    it under the terms of either
   8
   9      * the GNU Lesser General Public License as published by the Free
  10        Software Foundation; either version 3 of the License, or (at
  11        your option) any later version
  12
  13    or
  14
  15      * the GNU General Public License as published by the Free
  16        Software Foundation; either version 2 of the License, or (at
  17        your option) any later version
  18
  19    or both in parallel, as here.
  20
  21    elfutils is distributed in the hope that it will be useful, but
  22    WITHOUT ANY WARRANTY; without even the implied warranty of
  23    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  24    General Public License for more details.
  25
  26    You should have received copies of the GNU General Public License and
  27    the GNU Lesser General Public License along with this program.  If
  28    not, see <http://www.gnu.org/licenses/>.  */
  29
  30 #ifdef HAVE_CONFIG_H
  31 # include <config.h>
  32 #endif
  33
  34 #include <assert.h>
  35 #include <endian.h>
  36 #include <stdbool.h>
  37 #include <stddef.h>
  38 #include <string.h>
  39
  40 #include "gelf.h"
  41 #include "libelfP.h"
  42 #include "elf-knowledge.h"
  43
  44 #ifndef LIBELFBITS
  45 # define LIBELFBITS 32
  46 #endif
  47
  48
  49 #define process_block(crc, data) \
  50   __libelf_crc32 (crc, data->d_buf, data->d_size)
  51
  52
  53 long int
  54 elfw2(LIBELFBITS,checksum) (elf)
  55      Elf *elf;
  56 {
  57   size_t shstrndx;
  58   Elf_Scn *scn;
  59   long int result = 0;
  60   unsigned char *ident;
  61   bool same_byte_order;
  62
  63   if (elf == NULL)
  64     return -1l;
  65
  66   /* Find the section header string table.  */
  67   if  (INTUSE(elf_getshdrstrndx) (elf, &shstrndx) < 0)
  68     {
  69       /* This can only happen if the ELF handle is not for real.  */
  70       __libelf_seterrno (ELF_E_INVALID_HANDLE);
  71       return -1l;
  72     }
  73
  74   /* Determine whether the byte order of the file and that of the host
  75      is the same.  */
  76   ident = elf->state.ELFW(elf,LIBELFBITS).ehdr->e_ident;
  77   same_byte_order = ((ident[EI_DATA] == ELFDATA2LSB
  78                       && __BYTE_ORDER == __LITTLE_ENDIAN)
  79                      || (ident[EI_DATA] == ELFDATA2MSB
  80                          && __BYTE_ORDER == __BIG_ENDIAN));
  81
  82   /* If we don't have native byte order, we will likely need to
  83      convert the data with xlate functions.  We do it upfront instead
  84      of relocking mid-iteration. */
  85   if (!likely (same_byte_order))
  86     rwlock_wrlock (elf->lock);
  87   else
  88     rwlock_rdlock (elf->lock);
  89
  90   /* Iterate over all sections to find those which are not strippable.  */
  91   scn = NULL;
  92   while ((scn = INTUSE(elf_nextscn) (elf, scn)) != NULL)
  93     {
  94       GElf_Shdr shdr_mem;
  95       GElf_Shdr *shdr;
  96       Elf_Data *data;
  97
  98       /* Get the section header.  */
  99       shdr = INTUSE(gelf_getshdr) (scn, &shdr_mem);
 100       if (shdr == NULL)
 101         {
 102           __libelf_seterrno (ELF_E_INVALID_SECTION_HEADER);
 103           result = -1l;
 104           goto out;
 105         }
 106
 107       if (SECTION_STRIP_P (shdr,
 108                            INTUSE(elf_strptr) (elf, shstrndx, shdr->sh_name),
 109                            true))
 110         /* The section can be stripped.  Don't use it.  */
 111         continue;
 112
 113       /* Do not look at NOBITS sections.  */
 114       if (shdr->sh_type == SHT_NOBITS)
 115         continue;
 116
 117       /* To compute the checksum we need to get to the data.  For
 118          repeatable results we must use the external format.  The data
 119          we get with 'elf'getdata' might be changed for endianess
 120          reasons.  Therefore we use 'elf_rawdata' if possible.  But
 121          this function can fail if the data was constructed by the
 122          program.  In this case we have to use 'elf_getdata' and
 123          eventually convert the data to the external format.  */
 124       data = INTUSE(elf_rawdata) (scn, NULL);
 125       if (data != NULL)
 126         {
 127           /* The raw data is available.  */
 128           result = process_block (result, data);
 129
 130           /* Maybe the user added more data.  These blocks cannot be
 131              read using 'elf_rawdata'.  Simply proceed with looking
 132              for more data block with 'elf_getdata'.  */
 133         }
 134
 135       /* Iterate through the list of data blocks.  */
 136       while ((data = INTUSE(elf_getdata) (scn, data)) != NULL)
 137         /* If the file byte order is the same as the host byte order
 138            process the buffer directly.  If the data is just a stream
 139            of bytes which the library will not convert we can use it
 140            as well.  */
 141         if (likely (same_byte_order) || data->d_type == ELF_T_BYTE)
 142           result = process_block (result, data);
 143         else
 144           {
 145             /* Convert the data to file byte order.  */
 146             if (INTUSE(elfw2(LIBELFBITS,xlatetof)) (data, data, ident[EI_DATA])
 147                 == NULL)
 148               {
 149                 result = -1l;
 150                 goto out;
 151               }
 152
 153             result = process_block (result, data);
 154
 155             /* And convert it back.  */
 156             if (INTUSE(elfw2(LIBELFBITS,xlatetom)) (data, data, ident[EI_DATA])
 157                 == NULL)
 158               {
 159                 result = -1l;
 160                 goto out;
 161               }
 162           }
 163     }
 164
 165  out:
 166   rwlock_unlock (elf->lock);
 167   return result;
 168 }
 169 INTDEF(elfw2(LIBELFBITS,checksum))