1 /* 2 * Copyright (c) 1997 Christopher G. Demetriou. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 3. All advertising materials mentioning features or use of this software 13 * must display the following acknowledgement: 14 * This product includes software developed by Christopher G. Demetriou 15 * for the NetBSD Project. 16 * 4. The name of the author may not be used to endorse or promote products 17 * derived from this software without specific prior written permission 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 20 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 21 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 22 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 23 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 24 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 28 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 29 */ 30 31 #include <sys/cdefs.h> 32 #ifndef lint 33 #if 0 34 __RCSID("$NetBSD: exec_elf32.c,v 1.6 1999/09/20 04:12:16 christos Exp $"); 35 #endif 36 #endif 37 __FBSDID("$FreeBSD$"); 38 39 #ifndef ELFSIZE 40 #define ELFSIZE 32 41 #endif 42 43 #include <sys/types.h> 44 #include <sys/endian.h> 45 #include <sys/stat.h> 46 47 #include <errno.h> 48 #include <limits.h> 49 #include <stddef.h> 50 #include <stdio.h> 51 #include <stdlib.h> 52 #include <string.h> 53 #include <unistd.h> 54 55 #include "extern.h" 56 57 #if (defined(NLIST_ELF32) && (ELFSIZE == 32)) || \ 58 (defined(NLIST_ELF64) && (ELFSIZE == 64)) 59 60 #define __ELF_WORD_SIZE ELFSIZE 61 #if (ELFSIZE == 32) 62 #include <sys/elf32.h> 63 #define xewtoh(x) ((data == ELFDATA2MSB) ? be32toh(x) : le32toh(x)) 64 #define htoxew(x) ((data == ELFDATA2MSB) ? htobe32(x) : htole32(x)) 65 #define wewtoh(x) ((data == ELFDATA2MSB) ? be32toh(x) : le32toh(x)) 66 #define htowew(x) ((data == ELFDATA2MSB) ? htobe32(x) : htole32(x)) 67 #elif (ELFSIZE == 64) 68 #include <sys/elf64.h> 69 #define xewtoh(x) ((data == ELFDATA2MSB) ? be64toh(x) : le64toh(x)) 70 #define htoxew(x) ((data == ELFDATA2MSB) ? htobe64(x) : htole64(x)) 71 /* elf64 Elf64_Word are 32 bits */ 72 #define wewtoh(x) ((data == ELFDATA2MSB) ? be32toh(x) : le32toh(x)) 73 #define htowew(x) ((data == ELFDATA2MSB) ? htobe32(x) : htole32(x)) 74 #endif 75 #include <sys/elf_generic.h> 76 77 #define CONCAT(x,y) __CONCAT(x,y) 78 #define ELFNAME(x) CONCAT(elf,CONCAT(ELFSIZE,CONCAT(_,x))) 79 #define ELFNAME2(x,y) CONCAT(x,CONCAT(_elf,CONCAT(ELFSIZE,CONCAT(_,y)))) 80 #define ELFNAMEEND(x) CONCAT(x,CONCAT(_elf,ELFSIZE)) 81 #define ELFDEFNNAME(x) CONCAT(ELF,CONCAT(ELFSIZE,CONCAT(_,x))) 82 #ifndef ELFCLASS 83 #define ELFCLASS CONCAT(ELFCLASS,ELFSIZE) 84 #endif 85 86 #define xe16toh(x) ((data == ELFDATA2MSB) ? be16toh(x) : le16toh(x)) 87 #define xe32toh(x) ((data == ELFDATA2MSB) ? be32toh(x) : le32toh(x)) 88 #define htoxe32(x) ((data == ELFDATA2MSB) ? htobe32(x) : htole32(x)) 89 90 struct shlayout { 91 Elf_Shdr *shdr; 92 void *bufp; 93 }; 94 95 static ssize_t 96 xreadatoff(int fd, void *buf, off_t off, size_t size, const char *fn) 97 { 98 ssize_t rv; 99 100 if (lseek(fd, off, SEEK_SET) != off) { 101 perror(fn); 102 return -1; 103 } 104 if ((size_t)(rv = read(fd, buf, size)) != size) { 105 fprintf(stderr, "%s: read error: %s\n", fn, 106 rv == -1 ? strerror(errno) : "short read"); 107 return -1; 108 } 109 return size; 110 } 111 112 static ssize_t 113 xwriteatoff(int fd, void *buf, off_t off, size_t size, const char *fn) 114 { 115 ssize_t rv; 116 117 if (lseek(fd, off, SEEK_SET) != off) { 118 perror(fn); 119 return -1; 120 } 121 if ((size_t)(rv = write(fd, buf, size)) != size) { 122 fprintf(stderr, "%s: write error: %s\n", fn, 123 rv == -1 ? strerror(errno) : "short write"); 124 return -1; 125 } 126 return size; 127 } 128 129 static void * 130 xmalloc(size_t size, const char *fn, const char *use) 131 { 132 void *rv; 133 134 rv = malloc(size); 135 if (rv == NULL) 136 fprintf(stderr, "%s: out of memory (allocating for %s)\n", 137 fn, use); 138 return (rv); 139 } 140 141 static void * 142 xrealloc(void *ptr, size_t size, const char *fn, const char *use) 143 { 144 void *rv; 145 146 rv = realloc(ptr, size); 147 if (rv == NULL) { 148 free(ptr); 149 fprintf(stderr, "%s: out of memory (reallocating for %s)\n", 150 fn, use); 151 } 152 return (rv); 153 } 154 155 int 156 ELFNAMEEND(check)(int fd, const char *fn) 157 { 158 Elf_Ehdr eh; 159 struct stat sb; 160 unsigned char data; 161 162 /* 163 * Check the header to maek sure it's an ELF file (of the 164 * appropriate size). 165 */ 166 if (fstat(fd, &sb) == -1) 167 return 0; 168 if (sb.st_size < (off_t)(sizeof eh)) 169 return 0; 170 if (read(fd, &eh, sizeof eh) != sizeof eh) 171 return 0; 172 173 if (IS_ELF(eh) == 0 || eh.e_ident[EI_CLASS] != ELFCLASS) 174 return 0; 175 176 data = eh.e_ident[EI_DATA]; 177 178 switch (xe16toh(eh.e_machine)) { 179 case EM_386: break; 180 case EM_ALPHA: break; 181 #ifndef EM_AARCH64 182 #define EM_AARCH64 183 183 #endif 184 case EM_AARCH64: break; 185 case EM_ARM: break; 186 case EM_MIPS: break; 187 case /* EM_MIPS_RS3_LE */ EM_MIPS_RS4_BE: break; 188 case EM_PPC: break; 189 case EM_PPC64: break; 190 #ifndef EM_RISCV 191 #define EM_RISCV 243 192 #endif 193 case EM_RISCV: break; 194 case EM_S390: break; 195 case EM_SPARCV9: break; 196 case EM_X86_64: break; 197 /* ELFDEFNNAME(MACHDEP_ID_CASES) */ 198 199 default: 200 return 0; 201 } 202 203 return 1; 204 } 205 206 /* 207 * This function 'hides' (some of) ELF executable file's symbols. 208 * It hides them by renaming them to "_$$hide$$ <filename> <symbolname>". 209 * Symbols in the global keep list, or which are marked as being undefined, 210 * are left alone. 211 * 212 * An old version of this code shuffled various tables around, turning 213 * global symbols to be hidden into local symbols. That lost on the 214 * mips, because CALL16 relocs must reference global symbols, and, if 215 * those symbols were being hidden, they were no longer global. 216 * 217 * The new renaming behaviour doesn't take global symbols out of the 218 * namespace. However, it's ... unlikely that there will ever be 219 * any collisions in practice because of the new method. 220 */ 221 int 222 ELFNAMEEND(hide)(int fd, const char *fn) 223 { 224 Elf_Ehdr ehdr; 225 struct shlayout *layoutp = NULL; 226 Elf_Shdr *shdrp = NULL, *symtabshdr, *strtabshdr, *shstrtabshdr; 227 Elf_Shdr shdrshdr; 228 Elf_Sym *symtabp = NULL; 229 char *shstrtabp = NULL, *strtabp = NULL; 230 Elf_Size nsyms, ewi; 231 Elf_Off off; 232 ssize_t shdrsize; 233 int rv, i, weird, l, m, r, strtabidx; 234 size_t nstrtab_size, nstrtab_nextoff, fn_size, size; 235 char *nstrtabp = NULL; 236 unsigned char data; 237 const char *weirdreason = NULL; 238 void *buf; 239 Elf_Half shnum; 240 241 rv = 0; 242 if (xreadatoff(fd, &ehdr, 0, sizeof ehdr, fn) != sizeof ehdr) 243 goto bad; 244 245 data = ehdr.e_ident[EI_DATA]; 246 shnum = xe16toh(ehdr.e_shnum); 247 248 shdrsize = shnum * xe16toh(ehdr.e_shentsize); 249 if ((shdrp = xmalloc(shdrsize, fn, "section header table")) == NULL) 250 goto bad; 251 if (xreadatoff(fd, shdrp, xewtoh(ehdr.e_shoff), shdrsize, fn) != 252 shdrsize) 253 goto bad; 254 255 symtabshdr = strtabshdr = shstrtabshdr = NULL; 256 weird = 0; 257 for (i = 0; i < shnum; i++) { 258 switch (xe32toh(shdrp[i].sh_type)) { 259 case SHT_SYMTAB: 260 if (symtabshdr != NULL) { 261 weird = 1; 262 weirdreason = "multiple symbol tables"; 263 } 264 symtabshdr = &shdrp[i]; 265 strtabshdr = &shdrp[xe32toh(shdrp[i].sh_link)]; 266 break; 267 case SHT_STRTAB: 268 if (i == xe16toh(ehdr.e_shstrndx)) 269 shstrtabshdr = &shdrp[i]; 270 break; 271 } 272 } 273 if (symtabshdr == NULL) 274 goto out; 275 if (strtabshdr == NULL) { 276 weird = 1; 277 weirdreason = "string table does not exist"; 278 } 279 if (shstrtabshdr == NULL) { 280 weird = 1; 281 weirdreason = "section header string table does not exist"; 282 } 283 if (strtabshdr == shstrtabshdr) { 284 weird = 1; 285 weirdreason = "combined strtab and shstrtab not supported"; 286 } 287 if (weirdreason == NULL) 288 weirdreason = "unsupported"; 289 if (weird) { 290 fprintf(stderr, "%s: weird executable (%s)\n", fn, weirdreason); 291 goto bad; 292 } 293 294 /* 295 * sort section layout table by offset 296 */ 297 layoutp = xmalloc((shnum + 1) * sizeof(struct shlayout), 298 fn, "layout table"); 299 if (layoutp == NULL) 300 goto bad; 301 302 /* add a pseudo entry to represent the section header table */ 303 shdrshdr.sh_offset = ehdr.e_shoff; 304 shdrshdr.sh_size = htoxew(shdrsize); 305 shdrshdr.sh_addralign = htoxew(ELFSIZE / 8); 306 layoutp[shnum].shdr = &shdrshdr; 307 308 /* insert and sort normal section headers */ 309 for (i = shnum; i-- != 0;) { 310 l = i + 1; 311 r = shnum; 312 while (l <= r) { 313 m = ( l + r) / 2; 314 if (xewtoh(shdrp[i].sh_offset) > 315 xewtoh(layoutp[m].shdr->sh_offset)) 316 l = m + 1; 317 else 318 r = m - 1; 319 } 320 321 if (r != i) { 322 memmove(&layoutp[i], &layoutp[i + 1], 323 sizeof(struct shlayout) * (r - i)); 324 } 325 326 layoutp[r].shdr = &shdrp[i]; 327 layoutp[r].bufp = NULL; 328 } 329 ++shnum; 330 331 /* 332 * load up everything we need 333 */ 334 335 /* load section string table for debug use */ 336 if ((size = xewtoh(shstrtabshdr->sh_size)) == 0) 337 goto bad; 338 if ((shstrtabp = xmalloc(size, fn, "section string table")) == NULL) 339 goto bad; 340 if ((size_t)xreadatoff(fd, shstrtabp, xewtoh(shstrtabshdr->sh_offset), 341 size, fn) != size) 342 goto bad; 343 if (shstrtabp[size - 1] != '\0') 344 goto bad; 345 346 /* we need symtab, strtab, and everything behind strtab */ 347 strtabidx = INT_MAX; 348 for (i = 0; i < shnum; i++) { 349 if (layoutp[i].shdr == &shdrshdr) { 350 /* not load section header again */ 351 layoutp[i].bufp = shdrp; 352 continue; 353 } 354 if (layoutp[i].shdr == shstrtabshdr) { 355 /* not load section string table again */ 356 layoutp[i].bufp = shstrtabp; 357 continue; 358 } 359 360 if (layoutp[i].shdr == strtabshdr) 361 strtabidx = i; 362 if (layoutp[i].shdr == symtabshdr || i >= strtabidx) { 363 off = xewtoh(layoutp[i].shdr->sh_offset); 364 if ((size = xewtoh(layoutp[i].shdr->sh_size)) == 0) 365 goto bad; 366 layoutp[i].bufp = xmalloc(size, fn, 367 shstrtabp + xewtoh(layoutp[i].shdr->sh_name)); 368 if (layoutp[i].bufp == NULL) 369 goto bad; 370 if ((size_t)xreadatoff(fd, layoutp[i].bufp, off, size, fn) != 371 size) 372 goto bad; 373 374 /* set symbol table and string table */ 375 if (layoutp[i].shdr == symtabshdr) { 376 symtabp = layoutp[i].bufp; 377 } else if (layoutp[i].shdr == strtabshdr) { 378 strtabp = layoutp[i].bufp; 379 if (strtabp[size - 1] != '\0') 380 goto bad; 381 } 382 } 383 } 384 385 nstrtab_size = 256; 386 nstrtabp = xmalloc(nstrtab_size, fn, "new string table"); 387 if (nstrtabp == NULL) 388 goto bad; 389 nstrtab_nextoff = 0; 390 391 fn_size = strlen(fn); 392 393 /* Prepare data structures for symbol movement. */ 394 nsyms = xewtoh(symtabshdr->sh_size) / xewtoh(symtabshdr->sh_entsize); 395 396 /* move symbols, making them local */ 397 for (ewi = 0; ewi < nsyms; ewi++) { 398 Elf_Sym *sp = &symtabp[ewi]; 399 const char *symname = strtabp + xe32toh(sp->st_name); 400 size_t newent_len; 401 /* 402 * make sure there's size for the next entry, even if it's 403 * as large as it can be. 404 * 405 * "_$$hide$$ <filename> <symname><NUL>" -> 406 * 9 + 3 + sizes of fn and sym name 407 */ 408 while ((nstrtab_size - nstrtab_nextoff) < 409 strlen(symname) + fn_size + 12) { 410 nstrtab_size *= 2; 411 nstrtabp = xrealloc(nstrtabp, nstrtab_size, fn, 412 "new string table"); 413 if (nstrtabp == NULL) 414 goto bad; 415 } 416 417 sp->st_name = htowew(nstrtab_nextoff); 418 419 /* if it's a keeper or is undefined, don't rename it. */ 420 if (in_keep_list(symname) || 421 (xe16toh(sp->st_shndx) == SHN_UNDEF)) { 422 newent_len = sprintf(nstrtabp + nstrtab_nextoff, 423 "%s", symname) + 1; 424 } else { 425 newent_len = sprintf(nstrtabp + nstrtab_nextoff, 426 "_$$hide$$ %s %s", fn, symname) + 1; 427 } 428 nstrtab_nextoff += newent_len; 429 } 430 strtabshdr->sh_size = htoxew(nstrtab_nextoff); 431 432 /* 433 * update section header table in ascending order of offset 434 */ 435 for (i = strtabidx + 1; i < shnum; i++) { 436 Elf_Off off, align; 437 off = xewtoh(layoutp[i - 1].shdr->sh_offset) + 438 xewtoh(layoutp[i - 1].shdr->sh_size); 439 align = xewtoh(layoutp[i].shdr->sh_addralign); 440 off = (off + (align - 1)) & ~(align - 1); 441 layoutp[i].shdr->sh_offset = htoxew(off); 442 } 443 444 /* 445 * write data to the file in descending order of offset 446 */ 447 for (i = shnum; i-- != 0;) { 448 if (layoutp[i].shdr == strtabshdr) { 449 /* new string table */ 450 buf = nstrtabp; 451 } else 452 buf = layoutp[i].bufp; 453 454 if (layoutp[i].shdr == &shdrshdr || 455 layoutp[i].shdr == symtabshdr || i >= strtabidx) { 456 if (buf == NULL) 457 goto bad; 458 459 /* 460 * update the offset of section header table in elf 461 * header if needed. 462 */ 463 if (layoutp[i].shdr == &shdrshdr && 464 ehdr.e_shoff != shdrshdr.sh_offset) { 465 ehdr.e_shoff = shdrshdr.sh_offset; 466 off = offsetof(Elf_Ehdr, e_shoff); 467 size = sizeof(Elf_Off); 468 if ((size_t)xwriteatoff(fd, &ehdr.e_shoff, off, size, 469 fn) != size) 470 goto bad; 471 } 472 473 off = xewtoh(layoutp[i].shdr->sh_offset); 474 size = xewtoh(layoutp[i].shdr->sh_size); 475 if ((size_t)xwriteatoff(fd, buf, off, size, fn) != size) 476 goto bad; 477 } 478 } 479 480 out: 481 if (layoutp != NULL) { 482 for (i = 0; i < shnum; i++) { 483 if (layoutp[i].bufp != NULL) 484 free(layoutp[i].bufp); 485 } 486 free(layoutp); 487 } 488 free(nstrtabp); 489 return (rv); 490 491 bad: 492 rv = 1; 493 goto out; 494 } 495 496 #endif /* include this size of ELF */ 497