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)) 170