1 /*- 2 * Copyright (c) 2010,2011 Kai Wang 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 */ 26 27 #include <sys/param.h> 28 #include <sys/stat.h> 29 #include <ctype.h> 30 #include <err.h> 31 #include <gelf.h> 32 #include <stdio.h> 33 #include <stdlib.h> 34 #include <string.h> 35 #include <unistd.h> 36 37 #include "elfcopy.h" 38 39 ELFTC_VCSID("$Id: binary.c 3611 2018-04-16 21:35:18Z jkoshy $"); 40 41 /* 42 * Convert ELF object to `binary'. Sections with SHF_ALLOC flag set 43 * are copied to the result binary. The relative offsets for each section 44 * are retained, so the result binary file might contain "holes". 45 */ 46 void 47 create_binary(int ifd, int ofd) 48 { 49 Elf *e; 50 Elf_Scn *scn; 51 Elf_Data *d; 52 GElf_Shdr sh; 53 off_t base, off; 54 int elferr; 55 56 if ((e = elf_begin(ifd, ELF_C_READ, NULL)) == NULL) 57 errx(EXIT_FAILURE, "elf_begin() failed: %s", 58 elf_errmsg(-1)); 59 60 base = 0; 61 if (lseek(ofd, base, SEEK_SET) < 0) 62 err(EXIT_FAILURE, "lseek failed"); 63 64 /* 65 * Find base offset in the first iteration. 66 */ 67 base = -1; 68 scn = NULL; 69 while ((scn = elf_nextscn(e, scn)) != NULL) { 70 if (gelf_getshdr(scn, &sh) == NULL) { 71 warnx("gelf_getshdr failed: %s", elf_errmsg(-1)); 72 (void) elf_errno(); 73 continue; 74 } 75 if ((sh.sh_flags & SHF_ALLOC) == 0 || 76 sh.sh_type == SHT_NOBITS || 77 sh.sh_size == 0) 78 continue; 79 if (base == -1 || (off_t) sh.sh_offset < base) 80 base = sh.sh_offset; 81 } 82 elferr = elf_errno(); 83 if (elferr != 0) 84 warnx("elf_nextscn failed: %s", elf_errmsg(elferr)); 85 86 if (base == -1) 87 return; 88 89 /* 90 * Write out sections in the second iteration. 91 */ 92 scn = NULL; 93 while ((scn = elf_nextscn(e, scn)) != NULL) { 94 if (gelf_getshdr(scn, &sh) == NULL) { 95 warnx("gelf_getshdr failed: %s", elf_errmsg(-1)); 96 (void) elf_errno(); 97 continue; 98 } 99 if ((sh.sh_flags & SHF_ALLOC) == 0 || 100 sh.sh_type == SHT_NOBITS || 101 sh.sh_size == 0) 102 continue; 103 (void) elf_errno(); 104 if ((d = elf_rawdata(scn, NULL)) == NULL) { 105 elferr = elf_errno(); 106 if (elferr != 0) 107 warnx("elf_rawdata failed: %s", elf_errmsg(-1)); 108 continue; 109 } 110 if (d->d_buf == NULL || d->d_size == 0) 111 continue; 112 113 /* lseek to section offset relative to `base'. */ 114 off = sh.sh_offset - base; 115 if (lseek(ofd, off, SEEK_SET) < 0) 116 err(EXIT_FAILURE, "lseek failed"); 117 118 /* Write out section contents. */ 119 if (write(ofd, d->d_buf, d->d_size) != (ssize_t) d->d_size) 120 err(EXIT_FAILURE, "write failed"); 121 } 122 elferr = elf_errno(); 123 if (elferr != 0) 124 warnx("elf_nextscn failed: %s", elf_errmsg(elferr)); 125 } 126 127 #define _SYMBOL_NAMSZ 1024 128 129 /* 130 * Convert `binary' to ELF object. The input `binary' is converted to 131 * a relocatable (.o) file, a few symbols will also be created to make 132 * it easier to access the binary data in other compilation units. 133 */ 134 void 135 create_elf_from_binary(struct elfcopy *ecp, int ifd, const char *ifn) 136 { 137 char name[_SYMBOL_NAMSZ]; 138 struct section *sec, *sec_temp, *shtab; 139 struct stat sb; 140 GElf_Ehdr oeh; 141 GElf_Shdr sh; 142 void *content; 143 uint64_t off, data_start, data_end, data_size; 144 char *sym_basename, *p; 145 146 /* Reset internal section list. */ 147 if (!TAILQ_EMPTY(&ecp->v_sec)) 148 TAILQ_FOREACH_SAFE(sec, &ecp->v_sec, sec_list, sec_temp) { 149 TAILQ_REMOVE(&ecp->v_sec, sec, sec_list); 150 free(sec); 151 } 152 153 if (fstat(ifd, &sb) == -1) 154 err(EXIT_FAILURE, "fstat failed"); 155 156 /* Read the input binary file to a internal buffer. */ 157 if ((content = malloc(sb.st_size)) == NULL) 158 err(EXIT_FAILURE, "malloc failed"); 159 if (read(ifd, content, sb.st_size) != sb.st_size) 160 err(EXIT_FAILURE, "read failed"); 161 162 /* 163 * TODO: copy the input binary to output binary verbatim if -O is not 164 * specified. 165 */ 166 167 /* Create EHDR for output .o file. */ 168 if (gelf_newehdr(ecp->eout, ecp->oec) == NULL) 169 errx(EXIT_FAILURE, "gelf_newehdr failed: %s", 170 elf_errmsg(-1)); 171 if (gelf_getehdr(ecp->eout, &oeh) == NULL) 172 errx(EXIT_FAILURE, "gelf_getehdr() failed: %s", 173 elf_errmsg(-1)); 174 175 /* Initialise e_ident fields. */ 176 oeh.e_ident[EI_CLASS] = ecp->oec; 177 oeh.e_ident[EI_DATA] = ecp->oed; 178 /* 179 * TODO: Set OSABI according to the OS platform where elfcopy(1) 180 * was build. (probably) 181 */ 182 oeh.e_ident[EI_OSABI] = ELFOSABI_NONE; 183 oeh.e_machine = ecp->oem; 184 oeh.e_type = ET_REL; 185 oeh.e_entry = 0; 186 187 ecp->flags |= RELOCATABLE; 188 189 /* Create .shstrtab section */ 190 init_shstrtab(ecp); 191 ecp->shstrtab->off = 0; 192 193 /* 194 * Create `.data' section which contains the binary data. The 195 * section is inserted immediately after EHDR. 196 */ 197 off = gelf_fsize(ecp->eout, ELF_T_EHDR, 1, EV_CURRENT); 198 if (off == 0) 199 errx(EXIT_FAILURE, "gelf_fsize() failed: %s", elf_errmsg(-1)); 200 (void) create_external_section(ecp, ".data", NULL, content, sb.st_size, 201 off, SHT_PROGBITS, ELF_T_BYTE, SHF_ALLOC | SHF_WRITE, 1, 0, 1); 202 203 /* Insert .shstrtab after .data section. */ 204 if ((ecp->shstrtab->os = elf_newscn(ecp->eout)) == NULL) 205 errx(EXIT_FAILURE, "elf_newscn failed: %s", 206 elf_errmsg(-1)); 207 insert_to_sec_list(ecp, ecp->shstrtab, 1); 208 209 /* Insert section header table here. */ 210 shtab = insert_shtab(ecp, 1); 211 212 /* Count in .symtab and .strtab section headers. */ 213 shtab->sz += gelf_fsize(ecp->eout, ELF_T_SHDR, 2, EV_CURRENT); 214 215 if ((sym_basename = strdup(ifn)) == NULL) 216 err(1, "strdup"); 217 for (p = sym_basename; *p != '\0'; p++) 218 if (!isalnum(*p & 0xFF)) 219 *p = '_'; 220 #define _GEN_SYMNAME(S) do { \ 221 snprintf(name, sizeof(name), "%s%s%s", "_binary_", sym_basename, S); \ 222 } while (0) 223 224 /* 225 * Create symbol table. 226 */ 227 create_external_symtab(ecp); 228 data_start = 0; 229 data_end = data_start + sb.st_size; 230 data_size = sb.st_size; 231 _GEN_SYMNAME("_start"); 232 add_to_symtab(ecp, name, data_start, 0, 1, 233 ELF32_ST_INFO(STB_GLOBAL, STT_NOTYPE), 0, 1); 234 _GEN_SYMNAME("_end"); 235 add_to_symtab(ecp, name, data_end, 0, 1, 236 ELF32_ST_INFO(STB_GLOBAL, STT_NOTYPE), 0, 1); 237 _GEN_SYMNAME("_size"); 238 add_to_symtab(ecp, name, data_size, 0, SHN_ABS, 239 ELF32_ST_INFO(STB_GLOBAL, STT_NOTYPE), 0, 1); 240 finalize_external_symtab(ecp); 241 create_symtab_data(ecp); 242 #undef _GEN_SYMNAME 243 free(sym_basename); 244 245 /* 246 * Write the underlying ehdr. Note that it should be called 247 * before elf_setshstrndx() since it will overwrite e->e_shstrndx. 248 */ 249 if (gelf_update_ehdr(ecp->eout, &oeh) == 0) 250 errx(EXIT_FAILURE, "gelf_update_ehdr() failed: %s", 251 elf_errmsg(-1)); 252 253 /* Generate section name string table (.shstrtab). */ 254 ecp->flags |= SYMTAB_EXIST; 255 set_shstrtab(ecp); 256 257 /* Update sh_name pointer for each section header entry. */ 258 update_shdr(ecp, 0); 259 260 /* Properly set sh_link field of .symtab section. */ 261 if (gelf_getshdr(ecp->symtab->os, &sh) == NULL) 262 errx(EXIT_FAILURE, "692 gelf_getshdr() failed: %s", 263 elf_errmsg(-1)); 264 sh.sh_link = elf_ndxscn(ecp->strtab->os); 265 if (!gelf_update_shdr(ecp->symtab->os, &sh)) 266 errx(EXIT_FAILURE, "gelf_update_shdr() failed: %s", 267 elf_errmsg(-1)); 268 269 /* Renew oeh to get the updated e_shstrndx. */ 270 if (gelf_getehdr(ecp->eout, &oeh) == NULL) 271 errx(EXIT_FAILURE, "gelf_getehdr() failed: %s", 272 elf_errmsg(-1)); 273 274 /* Resync section offsets. */ 275 resync_sections(ecp); 276 277 /* Store SHDR offset in EHDR. */ 278 oeh.e_shoff = shtab->off; 279 280 /* Update ehdr since we modified e_shoff. */ 281 if (gelf_update_ehdr(ecp->eout, &oeh) == 0) 282 errx(EXIT_FAILURE, "gelf_update_ehdr() failed: %s", 283 elf_errmsg(-1)); 284 285 /* Write out the output elf object. */ 286 if (elf_update(ecp->eout, ELF_C_WRITE) < 0) 287 errx(EXIT_FAILURE, "elf_update() failed: %s", 288 elf_errmsg(-1)); 289 290 /* Release allocated resource. */ 291 free(content); 292 free_elf(ecp); 293 } 294