exec_elf32.c revision 292885
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: stable/10/usr.sbin/crunch/crunchide/exec_elf32.c 292885 2015-12-29 20:36:11Z emaste $"); 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 90struct shlayout { 91 Elf_Shdr *shdr; 92 void *bufp; 93}; 94 95static ssize_t 96xreadatoff(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 112static ssize_t 113xwriteatoff(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 129static void * 130xmalloc(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 141static void * 142xrealloc(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 155int 156ELFNAMEEND(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_IA_64: break; 187 case EM_MIPS: break; 188 case /* EM_MIPS_RS3_LE */ EM_MIPS_RS4_BE: break; 189 case EM_PPC: break; 190 case EM_PPC64: break; 191#ifndef EM_RISCV 192#define EM_RISCV 243 193#endif 194 case EM_RISCV: 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 */ 221int 222ELFNAMEEND(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 (weirdreason == NULL) 284 weirdreason = "unsupported"; 285 if (weird) { 286 fprintf(stderr, "%s: weird executable (%s)\n", fn, weirdreason); 287 goto bad; 288 } 289 290 /* 291 * sort section layout table by offset 292 */ 293 layoutp = xmalloc((shnum + 1) * sizeof(struct shlayout), 294 fn, "layout table"); 295 if (layoutp == NULL) 296 goto bad; 297 298 /* add a pseudo entry to represent the section header table */ 299 shdrshdr.sh_offset = ehdr.e_shoff; 300 shdrshdr.sh_size = htoxew(shdrsize); 301 shdrshdr.sh_addralign = htoxew(ELFSIZE / 8); 302 layoutp[shnum].shdr = &shdrshdr; 303 304 /* insert and sort normal section headers */ 305 for (i = shnum; i-- != 0;) { 306 l = i + 1; 307 r = shnum; 308 while (l <= r) { 309 m = ( l + r) / 2; 310 if (xewtoh(shdrp[i].sh_offset) > 311 xewtoh(layoutp[m].shdr->sh_offset)) 312 l = m + 1; 313 else 314 r = m - 1; 315 } 316 317 if (r != i) { 318 memmove(&layoutp[i], &layoutp[i + 1], 319 sizeof(struct shlayout) * (r - i)); 320 } 321 322 layoutp[r].shdr = &shdrp[i]; 323 layoutp[r].bufp = NULL; 324 } 325 ++shnum; 326 327 /* 328 * load up everything we need 329 */ 330 331 /* load section string table for debug use */ 332 if ((size = xewtoh(shstrtabshdr->sh_size)) == 0) 333 goto bad; 334 if ((shstrtabp = xmalloc(size, fn, "section string table")) == NULL) 335 goto bad; 336 if ((size_t)xreadatoff(fd, shstrtabp, xewtoh(shstrtabshdr->sh_offset), 337 size, fn) != size) 338 goto bad; 339 if (shstrtabp[size - 1] != '\0') 340 goto bad; 341 342 /* we need symtab, strtab, and everything behind strtab */ 343 strtabidx = INT_MAX; 344 for (i = 0; i < shnum; i++) { 345 if (layoutp[i].shdr == &shdrshdr) { 346 /* not load section header again */ 347 layoutp[i].bufp = shdrp; 348 continue; 349 } 350 if (layoutp[i].shdr == shstrtabshdr) { 351 /* not load section string table again */ 352 layoutp[i].bufp = shstrtabp; 353 continue; 354 } 355 356 if (layoutp[i].shdr == strtabshdr) 357 strtabidx = i; 358 if (layoutp[i].shdr == symtabshdr || i >= strtabidx) { 359 off = xewtoh(layoutp[i].shdr->sh_offset); 360 if ((size = xewtoh(layoutp[i].shdr->sh_size)) == 0) 361 goto bad; 362 layoutp[i].bufp = xmalloc(size, fn, 363 shstrtabp + xewtoh(layoutp[i].shdr->sh_name)); 364 if (layoutp[i].bufp == NULL) 365 goto bad; 366 if ((size_t)xreadatoff(fd, layoutp[i].bufp, off, size, fn) != 367 size) 368 goto bad; 369 370 /* set symbol table and string table */ 371 if (layoutp[i].shdr == symtabshdr) { 372 symtabp = layoutp[i].bufp; 373 } else if (layoutp[i].shdr == strtabshdr) { 374 strtabp = layoutp[i].bufp; 375 if (strtabp[size - 1] != '\0') 376 goto bad; 377 } 378 } 379 } 380 381 nstrtab_size = 256; 382 nstrtabp = xmalloc(nstrtab_size, fn, "new string table"); 383 if (nstrtabp == NULL) 384 goto bad; 385 nstrtab_nextoff = 0; 386 387 fn_size = strlen(fn); 388 389 /* Prepare data structures for symbol movement. */ 390 nsyms = xewtoh(symtabshdr->sh_size) / xewtoh(symtabshdr->sh_entsize); 391 392 /* move symbols, making them local */ 393 for (ewi = 0; ewi < nsyms; ewi++) { 394 Elf_Sym *sp = &symtabp[ewi]; 395 const char *symname = strtabp + xe32toh(sp->st_name); 396 size_t newent_len; 397 /* 398 * make sure there's size for the next entry, even if it's 399 * as large as it can be. 400 * 401 * "_$$hide$$ <filename> <symname><NUL>" -> 402 * 9 + 3 + sizes of fn and sym name 403 */ 404 while ((nstrtab_size - nstrtab_nextoff) < 405 strlen(symname) + fn_size + 12) { 406 nstrtab_size *= 2; 407 nstrtabp = xrealloc(nstrtabp, nstrtab_size, fn, 408 "new string table"); 409 if (nstrtabp == NULL) 410 goto bad; 411 } 412 413 sp->st_name = htowew(nstrtab_nextoff); 414 415 /* if it's a keeper or is undefined, don't rename it. */ 416 if (in_keep_list(symname) || 417 (xe16toh(sp->st_shndx) == SHN_UNDEF)) { 418 newent_len = sprintf(nstrtabp + nstrtab_nextoff, 419 "%s", symname) + 1; 420 } else { 421 newent_len = sprintf(nstrtabp + nstrtab_nextoff, 422 "_$$hide$$ %s %s", fn, symname) + 1; 423 } 424 nstrtab_nextoff += newent_len; 425 } 426 strtabshdr->sh_size = htoxew(nstrtab_nextoff); 427 428 /* 429 * update section header table in ascending order of offset 430 */ 431 for (i = strtabidx + 1; i < shnum; i++) { 432 Elf_Off off, align; 433 off = xewtoh(layoutp[i - 1].shdr->sh_offset) + 434 xewtoh(layoutp[i - 1].shdr->sh_size); 435 align = xewtoh(layoutp[i].shdr->sh_addralign); 436 off = (off + (align - 1)) & ~(align - 1); 437 layoutp[i].shdr->sh_offset = htoxew(off); 438 } 439 440 /* 441 * write data to the file in descending order of offset 442 */ 443 for (i = shnum; i-- != 0;) { 444 if (layoutp[i].shdr == strtabshdr) { 445 /* new string table */ 446 buf = nstrtabp; 447 } else 448 buf = layoutp[i].bufp; 449 450 if (layoutp[i].shdr == &shdrshdr || 451 layoutp[i].shdr == symtabshdr || i >= strtabidx) { 452 if (buf == NULL) 453 goto bad; 454 455 /* 456 * update the offset of section header table in elf 457 * header if needed. 458 */ 459 if (layoutp[i].shdr == &shdrshdr && 460 ehdr.e_shoff != shdrshdr.sh_offset) { 461 ehdr.e_shoff = shdrshdr.sh_offset; 462 off = offsetof(Elf_Ehdr, e_shoff); 463 size = sizeof(Elf_Off); 464 if ((size_t)xwriteatoff(fd, &ehdr.e_shoff, off, size, 465 fn) != size) 466 goto bad; 467 } 468 469 off = xewtoh(layoutp[i].shdr->sh_offset); 470 size = xewtoh(layoutp[i].shdr->sh_size); 471 if ((size_t)xwriteatoff(fd, buf, off, size, fn) != size) 472 goto bad; 473 } 474 } 475 476out: 477 if (layoutp != NULL) { 478 for (i = 0; i < shnum; i++) { 479 if (layoutp[i].bufp != NULL) 480 free(layoutp[i].bufp); 481 } 482 free(layoutp); 483 } 484 free(nstrtabp); 485 return (rv); 486 487bad: 488 rv = 1; 489 goto out; 490} 491 492#endif /* include this size of ELF */ 493