1 /* Compute simple checksum from permanent parts of the ELF file. 2 Copyright (C) 2002, 2003, 2004, 2005, 2009, 2015 Red Hat, Inc. 3 This file is part of elfutils. 4 Written by Ulrich Drepper <drepper (at) 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 *elf) 55 { 56 size_t shstrndx; 57 Elf_Scn *scn; 58 long int result = 0; 59 unsigned char *ident; 60 bool same_byte_order; 61 62 if (elf == NULL) 63 return -1l; 64 65 /* Find the section header string table. */ 66 if (INTUSE(elf_getshdrstrndx) (elf, &shstrndx) < 0) 67 { 68 /* This can only happen if the ELF handle is not for real. */ 69 __libelf_seterrno (ELF_E_INVALID_HANDLE); 70 return -1l; 71 } 72 73 /* Determine whether the byte order of the file and that of the host 74 is the same. */ 75 ident = elf->state.ELFW(elf,LIBELFBITS).ehdr->e_ident; 76 same_byte_order = ((ident[EI_DATA] == ELFDATA2LSB 77 && __BYTE_ORDER == __LITTLE_ENDIAN) 78 || (ident[EI_DATA] == ELFDATA2MSB 79 && __BYTE_ORDER == __BIG_ENDIAN)); 80 81 /* If we don't have native byte order, we will likely need to 82 convert the data with xlate functions. We do it upfront instead 83 of relocking mid-iteration. */ 84 if (!likely (same_byte_order)) 85 rwlock_wrlock (elf->lock); 86 else 87 rwlock_rdlock (elf->lock); 88 89 /* Iterate over all sections to find those which are not strippable. */ 90 scn = NULL; 91 while ((scn = INTUSE(elf_nextscn) (elf, scn)) != NULL) 92 { 93 GElf_Shdr shdr_mem; 94 GElf_Shdr *shdr; 95 Elf_Data *data; 96 97 /* Get the section header. */ 98 shdr = INTUSE(gelf_getshdr) (scn, &shdr_mem); 99 if (shdr == NULL) 100 { 101 __libelf_seterrno (ELF_E_INVALID_SECTION_HEADER); 102 result = -1l; 103 goto out; 104 } 105 106 if (SECTION_STRIP_P (shdr, 107 INTUSE(elf_strptr) (elf, shstrndx, shdr->sh_name), 108 true)) 109 /* The section can be stripped. Don't use it. */ 110 continue; 111 112 /* Do not look at NOBITS sections. */ 113 if (shdr->sh_type == SHT_NOBITS) 114 continue; 115 116 /* To compute the checksum we need to get to the data. For 117 repeatable results we must use the external format. The data 118 we get with 'elf'getdata' might be changed for endianess 119 reasons. Therefore we use 'elf_rawdata' if possible. But 120 this function can fail if the data was constructed by the 121 program. In this case we have to use 'elf_getdata' and 122 eventually convert the data to the external format. */ 123 data = INTUSE(elf_rawdata) (scn, NULL); 124 if (data != NULL) 125 { 126 /* The raw data is available. */ 127 result = process_block (result, data); 128 129 /* Maybe the user added more data. These blocks cannot be 130 read using 'elf_rawdata'. Simply proceed with looking 131 for more data block with 'elf_getdata'. */ 132 } 133 134 /* Iterate through the list of data blocks. */ 135 while ((data = INTUSE(elf_getdata) (scn, data)) != NULL) 136 /* If the file byte order is the same as the host byte order 137 process the buffer directly. If the data is just a stream 138 of bytes which the library will not convert we can use it 139 as well. */ 140 if (likely (same_byte_order) || data->d_type == ELF_T_BYTE) 141 result = process_block (result, data); 142 else 143 { 144 /* Convert the data to file byte order. */ 145 if (INTUSE(elfw2(LIBELFBITS,xlatetof)) (data, data, ident[EI_DATA]) 146 == NULL) 147 { 148 result = -1l; 149 goto out; 150 } 151 152 result = process_block (result, data); 153 154 /* And convert it back. */ 155 if (INTUSE(elfw2(LIBELFBITS,xlatetom)) (data, data, ident[EI_DATA]) 156 == NULL) 157 { 158 result = -1l; 159 goto out; 160 } 161 } 162 } 163 164 out: 165 rwlock_unlock (elf->lock); 166 return result; 167 } 168 INTDEF(elfw2(LIBELFBITS,checksum)) 169
