1 /* Return string pointer from string section. 2 Copyright (C) 1998-2002, 2004, 2008, 2009, 2015 Red Hat, Inc. 3 This file is part of elfutils. 4 Contributed by Ulrich Drepper <drepper (at) redhat.com>, 1998. 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 <libelf.h> 35 #include <stddef.h> 36 37 #include "libelfP.h" 38 39 40 static void * 41 get_zdata (Elf_Scn *strscn) 42 { 43 size_t zsize, zalign; 44 void *zdata = __libelf_decompress_elf (strscn, &zsize, &zalign); 45 if (zdata == NULL) 46 return NULL; 47 48 strscn->zdata_base = zdata; 49 strscn->zdata_size = zsize; 50 strscn->zdata_align = zalign; 51 52 return zdata; 53 } 54 55 char * 56 elf_strptr (Elf *elf, size_t idx, size_t offset) 57 { 58 if (elf == NULL) 59 return NULL; 60 61 if (elf->kind != ELF_K_ELF) 62 { 63 __libelf_seterrno (ELF_E_INVALID_HANDLE); 64 return NULL; 65 } 66 67 rwlock_rdlock (elf->lock); 68 69 char *result = NULL; 70 Elf_Scn *strscn; 71 72 /* Find the section in the list. */ 73 Elf_ScnList *runp = (elf->class == ELFCLASS32 74 || (offsetof (struct Elf, state.elf32.scns) 75 == offsetof (struct Elf, state.elf64.scns)) 76 ? &elf->state.elf32.scns : &elf->state.elf64.scns); 77 while (1) 78 { 79 if (idx < runp->max) 80 { 81 if (idx < runp->cnt) 82 strscn = &runp->data[idx]; 83 else 84 { 85 __libelf_seterrno (ELF_E_INVALID_INDEX); 86 goto out; 87 } 88 break; 89 } 90 91 idx -= runp->max; 92 93 runp = runp->next; 94 if (runp == NULL) 95 { 96 __libelf_seterrno (ELF_E_INVALID_INDEX); 97 goto out; 98 } 99 } 100 101 size_t sh_size = 0; 102 if (elf->class == ELFCLASS32) 103 { 104 Elf32_Shdr *shdr = strscn->shdr.e32 ?: __elf32_getshdr_rdlock (strscn); 105 if (unlikely (shdr->sh_type != SHT_STRTAB)) 106 { 107 /* This is no string section. */ 108 __libelf_seterrno (ELF_E_INVALID_SECTION); 109 goto out; 110 } 111 112 if ((shdr->sh_flags & SHF_COMPRESSED) == 0) 113 sh_size = shdr->sh_size; 114 else 115 { 116 if (strscn->zdata_base == NULL && get_zdata (strscn) == NULL) 117 goto out; 118 sh_size = strscn->zdata_size; 119 } 120 121 if (unlikely (offset >= sh_size)) 122 { 123 /* The given offset is too big, it is beyond this section. */ 124 __libelf_seterrno (ELF_E_OFFSET_RANGE); 125 goto out; 126 } 127 } 128 else 129 { 130 Elf64_Shdr *shdr = strscn->shdr.e64 ?: __elf64_getshdr_rdlock (strscn); 131 if (unlikely (shdr->sh_type != SHT_STRTAB)) 132 { 133 /* This is no string section. */ 134 __libelf_seterrno (ELF_E_INVALID_SECTION); 135 goto out; 136 } 137 138 if ((shdr->sh_flags & SHF_COMPRESSED) == 0) 139 sh_size = shdr->sh_size; 140 else 141 { 142 if (strscn->zdata_base == NULL && get_zdata (strscn) == NULL) 143 goto out; 144 sh_size = strscn->zdata_size; 145 } 146 147 if (unlikely (offset >= sh_size)) 148 { 149 /* The given offset is too big, it is beyond this section. */ 150 __libelf_seterrno (ELF_E_OFFSET_RANGE); 151 goto out; 152 } 153 } 154 155 if (strscn->rawdata_base == NULL && ! strscn->data_read) 156 { 157 rwlock_unlock (elf->lock); 158 rwlock_wrlock (elf->lock); 159 if (strscn->rawdata_base == NULL && ! strscn->data_read 160 /* Read the section data. */ 161 && __libelf_set_rawdata_wrlock (strscn) != 0) 162 goto out; 163 } 164 165 if (unlikely (strscn->zdata_base != NULL)) 166 { 167 /* Make sure the string is NUL terminated. Start from the end, 168 which very likely is a NUL char. */ 169 if (likely (memrchr (&strscn->zdata_base[offset], 170 '\0', sh_size - offset) != NULL)) 171 result = &strscn->zdata_base[offset]; 172 else 173 __libelf_seterrno (ELF_E_INVALID_INDEX); 174 } 175 else if (likely (strscn->data_list_rear == NULL)) 176 { 177 // XXX The above is currently correct since elf_newdata will 178 // make sure to convert the rawdata into the datalist if 179 // necessary. But it would be more efficient to keep the rawdata 180 // unconverted and only then iterate over the rest of the (newly 181 // added data) list. Note that when the ELF file is mmapped 182 // rawdata_base can be set while rawdata.d hasn't been 183 // initialized yet (when data_read is zero). So we cannot just 184 // look at the rawdata.d.d_size. 185 186 /* Make sure the string is NUL terminated. Start from the end, 187 which very likely is a NUL char. */ 188 if (likely (memrchr (&strscn->rawdata_base[offset], 189 '\0', sh_size - offset) != NULL)) 190 result = &strscn->rawdata_base[offset]; 191 else 192 __libelf_seterrno (ELF_E_INVALID_INDEX); 193 } 194 else 195 { 196 /* This is a file which is currently created. Use the list of 197 data blocks. */ 198 struct Elf_Data_List *dl = &strscn->data_list; 199 while (dl != NULL) 200 { 201 if (offset >= (size_t) dl->data.d.d_off 202 && offset < dl->data.d.d_off + dl->data.d.d_size) 203 { 204 /* Make sure the string is NUL terminated. Start from 205 the end, which very likely is a NUL char. */ 206 if (likely (memrchr ((char *) dl->data.d.d_buf 207 + (offset - dl->data.d.d_off), '\0', 208 (dl->data.d.d_size 209 - (offset - dl->data.d.d_off))) != NULL)) 210 result = ((char *) dl->data.d.d_buf 211 + (offset - dl->data.d.d_off)); 212 else 213 __libelf_seterrno (ELF_E_INVALID_INDEX); 214 break; 215 } 216 217 dl = dl->next; 218 } 219 } 220 221 out: 222 rwlock_unlock (elf->lock); 223 224 return result; 225 } 226 INTDEF(elf_strptr) 227
