1 /* Test program for adding (more than SHN_LORESERVE) sections. 2 Copyright (C) 2018 Red Hat, Inc. 3 This file is part of elfutils. 4 5 This file is free software; you can redistribute it and/or modify 6 it under the terms of the GNU General Public License as published by 7 the Free Software Foundation; either version 3 of the License, or 8 (at your option) any later version. 9 10 elfutils is distributed in the hope that it will be useful, but 11 WITHOUT ANY WARRANTY; without even the implied warranty of 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 GNU General Public License for more details. 14 15 You should have received a copy of the GNU General Public License 16 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 17 18 19 #ifdef HAVE_CONFIG_H 20 # include <config.h> 21 #endif 22 23 #include <errno.h> 24 #include <fcntl.h> 25 #include <inttypes.h> 26 #include <stdbool.h> 27 #include <stdio.h> 28 #include <stdlib.h> 29 #include <string.h> 30 #include <unistd.h> 31 #include <sys/types.h> 32 #include <sys/stat.h> 33 34 #include ELFUTILS_HEADER(elf) 35 #include <gelf.h> 36 37 38 /* shstrndx is special, might overflow into section zero header sh_link. */ 39 static int 40 setshstrndx (Elf *elf, size_t ndx) 41 { 42 printf ("setshstrndx: %zd\n", ndx); 43 44 GElf_Ehdr ehdr_mem; 45 GElf_Ehdr *ehdr = gelf_getehdr (elf, &ehdr_mem); 46 if (ehdr == NULL) 47 return -1; 48 49 if (ndx < SHN_LORESERVE) 50 ehdr->e_shstrndx = ndx; 51 else 52 { 53 ehdr->e_shstrndx = SHN_XINDEX; 54 Elf_Scn *zscn = elf_getscn (elf, 0); 55 GElf_Shdr zshdr_mem; 56 GElf_Shdr *zshdr = gelf_getshdr (zscn, &zshdr_mem); 57 if (zshdr == NULL) 58 return -1; 59 zshdr->sh_link = ndx; 60 if (gelf_update_shdr (zscn, zshdr) == 0) 61 return -1; 62 } 63 64 if (gelf_update_ehdr (elf, ehdr) == 0) 65 return -1; 66 67 return 0; 68 } 69 70 /* Will add nr new '.extra' sections and a new '.new_shstrtab' section 71 at the end. */ 72 static void 73 add_sections (const char *name, size_t nr, int use_mmap) 74 { 75 printf ("add_sections '%s': %zd\n", name, nr); 76 77 int fd = open (name, O_RDWR); 78 if (fd < 0) 79 { 80 fprintf (stderr, "Couldn't open file '%s': %s\n", 81 name, strerror (errno)); 82 exit (1); 83 } 84 85 Elf *elf = elf_begin (fd, use_mmap ? ELF_C_RDWR_MMAP : ELF_C_RDWR, NULL); 86 if (elf == NULL) 87 { 88 fprintf (stderr, "Couldn't open ELF file '%s': %s\n", 89 name, elf_errmsg (-1)); 90 exit (1); 91 } 92 93 /* We will add a new shstrtab section with two new names at the end. 94 Just get the current shstrtab table and add two entries '.extra' 95 and '.old_shstrtab' at the end of the table, so all existing indexes 96 are still valid. */ 97 size_t shstrndx; 98 if (elf_getshdrstrndx (elf, &shstrndx) < 0) 99 { 100 printf ("cannot get shstrndx: %s\n", elf_errmsg (-1)); 101 exit (1); 102 } 103 104 Elf_Scn *shstrtab_scn = elf_getscn (elf, shstrndx); 105 if (shstrtab_scn == NULL) 106 { 107 printf ("couldn't get shstrtab scn: %s\n", elf_errmsg (-1)); 108 exit (1); 109 } 110 Elf_Data *shstrtab_data = elf_getdata (shstrtab_scn, NULL); 111 if (shstrtab_data == NULL) 112 { 113 printf ("couldn't get shstrtab data: %s\n", elf_errmsg (-1)); 114 exit (1); 115 } 116 size_t new_shstrtab_size = (shstrtab_data->d_size 117 + strlen (".extra") + 1 118 + strlen (".old_shstrtab") + 1); 119 void *new_shstrtab_buf = malloc (new_shstrtab_size); 120 if (new_shstrtab_buf == NULL) 121 { 122 printf ("couldn't allocate new shstrtab data d_buf\n"); 123 exit (1); 124 } 125 memcpy (new_shstrtab_buf, shstrtab_data->d_buf, shstrtab_data->d_size); 126 size_t extra_idx = shstrtab_data->d_size; 127 size_t old_shstrtab_idx = extra_idx + strlen (".extra") + 1; 128 strcpy (new_shstrtab_buf + extra_idx, ".extra"); 129 strcpy (new_shstrtab_buf + old_shstrtab_idx, ".old_shstrtab"); 130 131 /* Change the name of the old shstrtab section, because elflint 132 has a strict check on the name/type for .shstrtab. */ 133 GElf_Shdr shdr_mem; 134 GElf_Shdr *shdr = gelf_getshdr (shstrtab_scn, &shdr_mem); 135 if (shdr == NULL) 136 { 137 printf ("cannot get header for old shstrtab section: %s\n", 138 elf_errmsg (-1)); 139 exit (1); 140 } 141 142 size_t shstrtab_idx = shdr->sh_name; 143 shdr->sh_name = old_shstrtab_idx; 144 145 if (gelf_update_shdr (shstrtab_scn, shdr) == 0) 146 { 147 printf ("cannot update old shstrtab section header: %s\n", 148 elf_errmsg (-1)); 149 exit (1); 150 } 151 152 // Add lots of .extra sections... 153 size_t cnt = 0; 154 while (cnt++ < nr) 155 { 156 Elf_Scn *scn = elf_newscn (elf); 157 if (scn == NULL) 158 { 159 printf ("cannot create .extra section (%zd): %s\n", cnt, 160 elf_errmsg (-1)); 161 exit (1); 162 } 163 164 Elf_Data *data = elf_newdata (scn); 165 if (data == NULL) 166 { 167 printf ("couldn't create new section data (%zd): %s\n", cnt, 168 elf_errmsg (-1)); 169 exit (1); 170 } 171 172 data->d_size = strlen ("extra") + 1; 173 data->d_buf = "extra"; 174 data->d_type = ELF_T_BYTE; 175 data->d_align = 1; 176 177 shdr = gelf_getshdr (scn, &shdr_mem); 178 if (shdr == NULL) 179 { 180 printf ("cannot get header for new section (%zd): %s\n", cnt, 181 elf_errmsg (-1)); 182 exit (1); 183 } 184 185 shdr->sh_type = SHT_PROGBITS; 186 shdr->sh_flags = 0; 187 shdr->sh_addr = 0; 188 shdr->sh_link = SHN_UNDEF; 189 shdr->sh_info = SHN_UNDEF; 190 shdr->sh_addralign = 1; 191 shdr->sh_entsize = 0; 192 shdr->sh_size = data->d_size; 193 shdr->sh_name = extra_idx; 194 195 if (gelf_update_shdr (scn, shdr) == 0) 196 { 197 printf ("cannot update new section header (%zd): %s\n", cnt, 198 elf_errmsg (-1)); 199 exit (1); 200 } 201 } 202 203 // Create new shstrtab section. 204 Elf_Scn *new_shstrtab_scn = elf_newscn (elf); 205 if (new_shstrtab_scn == NULL) 206 { 207 printf ("cannot create new shstrtab section: %s\n", elf_errmsg (-1)); 208 exit (1); 209 } 210 211 Elf_Data *new_shstrtab_data = elf_newdata (new_shstrtab_scn); 212 if (new_shstrtab_data == NULL) 213 { 214 printf ("couldn't create new shstrtab section data: %s\n", 215 elf_errmsg (-1)); 216 exit (1); 217 } 218 219 new_shstrtab_data->d_size = new_shstrtab_size; 220 new_shstrtab_data->d_buf = new_shstrtab_buf; 221 new_shstrtab_data->d_type = ELF_T_BYTE; 222 new_shstrtab_data->d_align = 1; 223 224 shdr = gelf_getshdr (new_shstrtab_scn, &shdr_mem); 225 if (shdr == NULL) 226 { 227 printf ("cannot get header for new shstrtab section: %s\n", 228 elf_errmsg (-1)); 229 exit (1); 230 } 231 232 shdr->sh_type = SHT_STRTAB; 233 shdr->sh_flags = 0; 234 shdr->sh_addr = 0; 235 shdr->sh_link = SHN_UNDEF; 236 shdr->sh_info = SHN_UNDEF; 237 shdr->sh_addralign = 1; 238 shdr->sh_entsize = 0; 239 shdr->sh_size = new_shstrtab_size; 240 shdr->sh_name = shstrtab_idx; 241 242 // Finished new shstrtab section, update the header. 243 if (gelf_update_shdr (new_shstrtab_scn, shdr) == 0) 244 { 245 printf ("cannot update new shstrtab section header: %s\n", 246 elf_errmsg (-1)); 247 exit (1); 248 } 249 250 // Set it as the new shstrtab section to get the names correct. 251 size_t new_shstrndx = elf_ndxscn (new_shstrtab_scn); 252 if (setshstrndx (elf, new_shstrndx) < 0) 253 { 254 printf ("cannot set shstrndx: %s\n", elf_errmsg (-1)); 255 exit (1); 256 } 257 258 // Write everything to disk. 259 if (elf_update (elf, ELF_C_WRITE) < 0) 260 { 261 printf ("failure in elf_update: %s\n", elf_errmsg (-1)); 262 exit (1); 263 } 264 265 if (elf_end (elf) != 0) 266 { 267 printf ("couldn't cleanup elf '%s': %s\n", name, elf_errmsg (-1)); 268 exit (1); 269 } 270 271 if (close (fd) != 0) 272 { 273 printf ("couldn't close '%s': %s\n", name, strerror (errno)); 274 exit (1); 275 } 276 277 free (new_shstrtab_buf); 278 } 279 280 int 281 main (int argc, char *argv[]) 282 { 283 elf_version (EV_CURRENT); 284 285 /* Takes the given file, and adds the given number of sections. */ 286 if (argc < 3 || argc > 4) 287 { 288 fprintf (stderr, "addsections [--mmap] nr elf.file\n"); 289 exit (1); 290 } 291 292 int argn = 1; 293 bool use_mmap = false; 294 if (strcmp (argv[argn], "--mmap") == 0) 295 { 296 use_mmap = true; 297 argn++; 298 } 299 300 size_t nr = atoi (argv[argn++]); 301 const char *file = argv[argn]; 302 add_sections (file, nr, use_mmap); 303 304 return 0; 305 } 306
