1#include <stdio.h> 2#include <stdarg.h> 3#include <stdlib.h> 4#include <stdint.h> 5#include <string.h> 6#include <errno.h> 7#include <unistd.h> 8#include <elf.h> 9#include <byteswap.h> 10#define USE_BSD 11#include <endian.h> 12 13#define MAX_SHDRS 100 14#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0])) 15static Elf32_Ehdr ehdr; 16static Elf32_Shdr shdr[MAX_SHDRS]; 17static Elf32_Sym *symtab[MAX_SHDRS]; 18static Elf32_Rel *reltab[MAX_SHDRS]; 19static char *strtab[MAX_SHDRS]; 20static unsigned long reloc_count, reloc_idx; 21static unsigned long *relocs; 22 23/* 24 * Following symbols have been audited. There values are constant and do 25 * not change if bzImage is loaded at a different physical address than 26 * the address for which it has been compiled. Don't warn user about 27 * absolute relocations present w.r.t these symbols. 28 */ 29static const char* safe_abs_relocs[] = { 30 "__kernel_vsyscall", 31 "__kernel_rt_sigreturn", 32 "__kernel_sigreturn", 33 "SYSENTER_RETURN", 34}; 35 36static int is_safe_abs_reloc(const char* sym_name) 37{ 38 int i, array_size; 39 40 array_size = sizeof(safe_abs_relocs)/sizeof(char*); 41 42 for(i = 0; i < array_size; i++) { 43 if (!strcmp(sym_name, safe_abs_relocs[i])) 44 /* Match found */ 45 return 1; 46 } 47 if (strncmp(sym_name, "__crc_", 6) == 0) 48 return 1; 49 return 0; 50} 51 52static void die(char *fmt, ...) 53{ 54 va_list ap; 55 va_start(ap, fmt); 56 vfprintf(stderr, fmt, ap); 57 va_end(ap); 58 exit(1); 59} 60 61static const char *sym_type(unsigned type) 62{ 63 static const char *type_name[] = { 64#define SYM_TYPE(X) [X] = #X 65 SYM_TYPE(STT_NOTYPE), 66 SYM_TYPE(STT_OBJECT), 67 SYM_TYPE(STT_FUNC), 68 SYM_TYPE(STT_SECTION), 69 SYM_TYPE(STT_FILE), 70 SYM_TYPE(STT_COMMON), 71 SYM_TYPE(STT_TLS), 72#undef SYM_TYPE 73 }; 74 const char *name = "unknown sym type name"; 75 if (type < ARRAY_SIZE(type_name)) { 76 name = type_name[type]; 77 } 78 return name; 79} 80 81static const char *sym_bind(unsigned bind) 82{ 83 static const char *bind_name[] = { 84#define SYM_BIND(X) [X] = #X 85 SYM_BIND(STB_LOCAL), 86 SYM_BIND(STB_GLOBAL), 87 SYM_BIND(STB_WEAK), 88#undef SYM_BIND 89 }; 90 const char *name = "unknown sym bind name"; 91 if (bind < ARRAY_SIZE(bind_name)) { 92 name = bind_name[bind]; 93 } 94 return name; 95} 96 97static const char *sym_visibility(unsigned visibility) 98{ 99 static const char *visibility_name[] = { 100#define SYM_VISIBILITY(X) [X] = #X 101 SYM_VISIBILITY(STV_DEFAULT), 102 SYM_VISIBILITY(STV_INTERNAL), 103 SYM_VISIBILITY(STV_HIDDEN), 104 SYM_VISIBILITY(STV_PROTECTED), 105#undef SYM_VISIBILITY 106 }; 107 const char *name = "unknown sym visibility name"; 108 if (visibility < ARRAY_SIZE(visibility_name)) { 109 name = visibility_name[visibility]; 110 } 111 return name; 112} 113 114static const char *rel_type(unsigned type) 115{ 116 static const char *type_name[] = { 117#define REL_TYPE(X) [X] = #X 118 REL_TYPE(R_386_NONE), 119 REL_TYPE(R_386_32), 120 REL_TYPE(R_386_PC32), 121 REL_TYPE(R_386_GOT32), 122 REL_TYPE(R_386_PLT32), 123 REL_TYPE(R_386_COPY), 124 REL_TYPE(R_386_GLOB_DAT), 125 REL_TYPE(R_386_JMP_SLOT), 126 REL_TYPE(R_386_RELATIVE), 127 REL_TYPE(R_386_GOTOFF), 128 REL_TYPE(R_386_GOTPC), 129#undef REL_TYPE 130 }; 131 const char *name = "unknown type rel type name"; 132 if (type < ARRAY_SIZE(type_name)) { 133 name = type_name[type]; 134 } 135 return name; 136} 137 138static const char *sec_name(unsigned shndx) 139{ 140 const char *sec_strtab; 141 const char *name; 142 sec_strtab = strtab[ehdr.e_shstrndx]; 143 name = "<noname>"; 144 if (shndx < ehdr.e_shnum) { 145 name = sec_strtab + shdr[shndx].sh_name; 146 } 147 else if (shndx == SHN_ABS) { 148 name = "ABSOLUTE"; 149 } 150 else if (shndx == SHN_COMMON) { 151 name = "COMMON"; 152 } 153 return name; 154} 155 156static const char *sym_name(const char *sym_strtab, Elf32_Sym *sym) 157{ 158 const char *name; 159 name = "<noname>"; 160 if (sym->st_name) { 161 name = sym_strtab + sym->st_name; 162 } 163 else { 164 name = sec_name(shdr[sym->st_shndx].sh_name); 165 } 166 return name; 167} 168 169 170 171#if BYTE_ORDER == LITTLE_ENDIAN 172#define le16_to_cpu(val) (val) 173#define le32_to_cpu(val) (val) 174#endif 175#if BYTE_ORDER == BIG_ENDIAN 176#define le16_to_cpu(val) bswap_16(val) 177#define le32_to_cpu(val) bswap_32(val) 178#endif 179 180static uint16_t elf16_to_cpu(uint16_t val) 181{ 182 return le16_to_cpu(val); 183} 184 185static uint32_t elf32_to_cpu(uint32_t val) 186{ 187 return le32_to_cpu(val); 188} 189 190static void read_ehdr(FILE *fp) 191{ 192 if (fread(&ehdr, sizeof(ehdr), 1, fp) != 1) { 193 die("Cannot read ELF header: %s\n", 194 strerror(errno)); 195 } 196 if (memcmp(ehdr.e_ident, ELFMAG, 4) != 0) { 197 die("No ELF magic\n"); 198 } 199 if (ehdr.e_ident[EI_CLASS] != ELFCLASS32) { 200 die("Not a 32 bit executable\n"); 201 } 202 if (ehdr.e_ident[EI_DATA] != ELFDATA2LSB) { 203 die("Not a LSB ELF executable\n"); 204 } 205 if (ehdr.e_ident[EI_VERSION] != EV_CURRENT) { 206 die("Unknown ELF version\n"); 207 } 208 /* Convert the fields to native endian */ 209 ehdr.e_type = elf16_to_cpu(ehdr.e_type); 210 ehdr.e_machine = elf16_to_cpu(ehdr.e_machine); 211 ehdr.e_version = elf32_to_cpu(ehdr.e_version); 212 ehdr.e_entry = elf32_to_cpu(ehdr.e_entry); 213 ehdr.e_phoff = elf32_to_cpu(ehdr.e_phoff); 214 ehdr.e_shoff = elf32_to_cpu(ehdr.e_shoff); 215 ehdr.e_flags = elf32_to_cpu(ehdr.e_flags); 216 ehdr.e_ehsize = elf16_to_cpu(ehdr.e_ehsize); 217 ehdr.e_phentsize = elf16_to_cpu(ehdr.e_phentsize); 218 ehdr.e_phnum = elf16_to_cpu(ehdr.e_phnum); 219 ehdr.e_shentsize = elf16_to_cpu(ehdr.e_shentsize); 220 ehdr.e_shnum = elf16_to_cpu(ehdr.e_shnum); 221 ehdr.e_shstrndx = elf16_to_cpu(ehdr.e_shstrndx); 222 223 if ((ehdr.e_type != ET_EXEC) && (ehdr.e_type != ET_DYN)) { 224 die("Unsupported ELF header type\n"); 225 } 226 if (ehdr.e_machine != EM_386) { 227 die("Not for x86\n"); 228 } 229 if (ehdr.e_version != EV_CURRENT) { 230 die("Unknown ELF version\n"); 231 } 232 if (ehdr.e_ehsize != sizeof(Elf32_Ehdr)) { 233 die("Bad Elf header size\n"); 234 } 235 if (ehdr.e_phentsize != sizeof(Elf32_Phdr)) { 236 die("Bad program header entry\n"); 237 } 238 if (ehdr.e_shentsize != sizeof(Elf32_Shdr)) { 239 die("Bad section header entry\n"); 240 } 241 if (ehdr.e_shstrndx >= ehdr.e_shnum) { 242 die("String table index out of bounds\n"); 243 } 244} 245 246static void read_shdrs(FILE *fp) 247{ 248 int i; 249 if (ehdr.e_shnum > MAX_SHDRS) { 250 die("%d section headers supported: %d\n", 251 ehdr.e_shnum, MAX_SHDRS); 252 } 253 if (fseek(fp, ehdr.e_shoff, SEEK_SET) < 0) { 254 die("Seek to %d failed: %s\n", 255 ehdr.e_shoff, strerror(errno)); 256 } 257 if (fread(&shdr, sizeof(shdr[0]), ehdr.e_shnum, fp) != ehdr.e_shnum) { 258 die("Cannot read ELF section headers: %s\n", 259 strerror(errno)); 260 } 261 for(i = 0; i < ehdr.e_shnum; i++) { 262 shdr[i].sh_name = elf32_to_cpu(shdr[i].sh_name); 263 shdr[i].sh_type = elf32_to_cpu(shdr[i].sh_type); 264 shdr[i].sh_flags = elf32_to_cpu(shdr[i].sh_flags); 265 shdr[i].sh_addr = elf32_to_cpu(shdr[i].sh_addr); 266 shdr[i].sh_offset = elf32_to_cpu(shdr[i].sh_offset); 267 shdr[i].sh_size = elf32_to_cpu(shdr[i].sh_size); 268 shdr[i].sh_link = elf32_to_cpu(shdr[i].sh_link); 269 shdr[i].sh_info = elf32_to_cpu(shdr[i].sh_info); 270 shdr[i].sh_addralign = elf32_to_cpu(shdr[i].sh_addralign); 271 shdr[i].sh_entsize = elf32_to_cpu(shdr[i].sh_entsize); 272 } 273 274} 275 276static void read_strtabs(FILE *fp) 277{ 278 int i; 279 for(i = 0; i < ehdr.e_shnum; i++) { 280 if (shdr[i].sh_type != SHT_STRTAB) { 281 continue; 282 } 283 strtab[i] = malloc(shdr[i].sh_size); 284 if (!strtab[i]) { 285 die("malloc of %d bytes for strtab failed\n", 286 shdr[i].sh_size); 287 } 288 if (fseek(fp, shdr[i].sh_offset, SEEK_SET) < 0) { 289 die("Seek to %d failed: %s\n", 290 shdr[i].sh_offset, strerror(errno)); 291 } 292 if (fread(strtab[i], 1, shdr[i].sh_size, fp) != shdr[i].sh_size) { 293 die("Cannot read symbol table: %s\n", 294 strerror(errno)); 295 } 296 } 297} 298 299static void read_symtabs(FILE *fp) 300{ 301 int i,j; 302 for(i = 0; i < ehdr.e_shnum; i++) { 303 if (shdr[i].sh_type != SHT_SYMTAB) { 304 continue; 305 } 306 symtab[i] = malloc(shdr[i].sh_size); 307 if (!symtab[i]) { 308 die("malloc of %d bytes for symtab failed\n", 309 shdr[i].sh_size); 310 } 311 if (fseek(fp, shdr[i].sh_offset, SEEK_SET) < 0) { 312 die("Seek to %d failed: %s\n", 313 shdr[i].sh_offset, strerror(errno)); 314 } 315 if (fread(symtab[i], 1, shdr[i].sh_size, fp) != shdr[i].sh_size) { 316 die("Cannot read symbol table: %s\n", 317 strerror(errno)); 318 } 319 for(j = 0; j < shdr[i].sh_size/sizeof(symtab[i][0]); j++) { 320 symtab[i][j].st_name = elf32_to_cpu(symtab[i][j].st_name); 321 symtab[i][j].st_value = elf32_to_cpu(symtab[i][j].st_value); 322 symtab[i][j].st_size = elf32_to_cpu(symtab[i][j].st_size); 323 symtab[i][j].st_shndx = elf16_to_cpu(symtab[i][j].st_shndx); 324 } 325 } 326} 327 328 329static void read_relocs(FILE *fp) 330{ 331 int i,j; 332 for(i = 0; i < ehdr.e_shnum; i++) { 333 if (shdr[i].sh_type != SHT_REL) { 334 continue; 335 } 336 reltab[i] = malloc(shdr[i].sh_size); 337 if (!reltab[i]) { 338 die("malloc of %d bytes for relocs failed\n", 339 shdr[i].sh_size); 340 } 341 if (fseek(fp, shdr[i].sh_offset, SEEK_SET) < 0) { 342 die("Seek to %d failed: %s\n", 343 shdr[i].sh_offset, strerror(errno)); 344 } 345 if (fread(reltab[i], 1, shdr[i].sh_size, fp) != shdr[i].sh_size) { 346 die("Cannot read symbol table: %s\n", 347 strerror(errno)); 348 } 349 for(j = 0; j < shdr[i].sh_size/sizeof(reltab[0][0]); j++) { 350 reltab[i][j].r_offset = elf32_to_cpu(reltab[i][j].r_offset); 351 reltab[i][j].r_info = elf32_to_cpu(reltab[i][j].r_info); 352 } 353 } 354} 355 356 357static void print_absolute_symbols(void) 358{ 359 int i; 360 printf("Absolute symbols\n"); 361 printf(" Num: Value Size Type Bind Visibility Name\n"); 362 for(i = 0; i < ehdr.e_shnum; i++) { 363 char *sym_strtab; 364 Elf32_Sym *sh_symtab; 365 int j; 366 if (shdr[i].sh_type != SHT_SYMTAB) { 367 continue; 368 } 369 sh_symtab = symtab[i]; 370 sym_strtab = strtab[shdr[i].sh_link]; 371 for(j = 0; j < shdr[i].sh_size/sizeof(symtab[0][0]); j++) { 372 Elf32_Sym *sym; 373 const char *name; 374 sym = &symtab[i][j]; 375 name = sym_name(sym_strtab, sym); 376 if (sym->st_shndx != SHN_ABS) { 377 continue; 378 } 379 printf("%5d %08x %5d %10s %10s %12s %s\n", 380 j, sym->st_value, sym->st_size, 381 sym_type(ELF32_ST_TYPE(sym->st_info)), 382 sym_bind(ELF32_ST_BIND(sym->st_info)), 383 sym_visibility(ELF32_ST_VISIBILITY(sym->st_other)), 384 name); 385 } 386 } 387 printf("\n"); 388} 389 390static void print_absolute_relocs(void) 391{ 392 int i, printed = 0; 393 394 for(i = 0; i < ehdr.e_shnum; i++) { 395 char *sym_strtab; 396 Elf32_Sym *sh_symtab; 397 unsigned sec_applies, sec_symtab; 398 int j; 399 if (shdr[i].sh_type != SHT_REL) { 400 continue; 401 } 402 sec_symtab = shdr[i].sh_link; 403 sec_applies = shdr[i].sh_info; 404 if (!(shdr[sec_applies].sh_flags & SHF_ALLOC)) { 405 continue; 406 } 407 sh_symtab = symtab[sec_symtab]; 408 sym_strtab = strtab[shdr[sec_symtab].sh_link]; 409 for(j = 0; j < shdr[i].sh_size/sizeof(reltab[0][0]); j++) { 410 Elf32_Rel *rel; 411 Elf32_Sym *sym; 412 const char *name; 413 rel = &reltab[i][j]; 414 sym = &sh_symtab[ELF32_R_SYM(rel->r_info)]; 415 name = sym_name(sym_strtab, sym); 416 if (sym->st_shndx != SHN_ABS) { 417 continue; 418 } 419 420 /* Absolute symbols are not relocated if bzImage is 421 * loaded at a non-compiled address. Display a warning 422 * to user at compile time about the absolute 423 * relocations present. 424 * 425 * User need to audit the code to make sure 426 * some symbols which should have been section 427 * relative have not become absolute because of some 428 * linker optimization or wrong programming usage. 429 * 430 * Before warning check if this absolute symbol 431 * relocation is harmless. 432 */ 433 if (is_safe_abs_reloc(name)) 434 continue; 435 436 if (!printed) { 437 printf("WARNING: Absolute relocations" 438 " present\n"); 439 printf("Offset Info Type Sym.Value " 440 "Sym.Name\n"); 441 printed = 1; 442 } 443 444 printf("%08x %08x %10s %08x %s\n", 445 rel->r_offset, 446 rel->r_info, 447 rel_type(ELF32_R_TYPE(rel->r_info)), 448 sym->st_value, 449 name); 450 } 451 } 452 453 if (printed) 454 printf("\n"); 455} 456 457static void walk_relocs(void (*visit)(Elf32_Rel *rel, Elf32_Sym *sym)) 458{ 459 int i; 460 /* Walk through the relocations */ 461 for(i = 0; i < ehdr.e_shnum; i++) { 462 char *sym_strtab; 463 Elf32_Sym *sh_symtab; 464 unsigned sec_applies, sec_symtab; 465 int j; 466 if (shdr[i].sh_type != SHT_REL) { 467 continue; 468 } 469 sec_symtab = shdr[i].sh_link; 470 sec_applies = shdr[i].sh_info; 471 if (!(shdr[sec_applies].sh_flags & SHF_ALLOC)) { 472 continue; 473 } 474 sh_symtab = symtab[sec_symtab]; 475 sym_strtab = strtab[shdr[sec_symtab].sh_link]; 476 for(j = 0; j < shdr[i].sh_size/sizeof(reltab[0][0]); j++) { 477 Elf32_Rel *rel; 478 Elf32_Sym *sym; 479 unsigned r_type; 480 rel = &reltab[i][j]; 481 sym = &sh_symtab[ELF32_R_SYM(rel->r_info)]; 482 r_type = ELF32_R_TYPE(rel->r_info); 483 /* Don't visit relocations to absolute symbols */ 484 if (sym->st_shndx == SHN_ABS) { 485 continue; 486 } 487 if (r_type == R_386_PC32) { 488 /* PC relative relocations don't need to be adjusted */ 489 } 490 else if (r_type == R_386_32) { 491 /* Visit relocations that need to be adjusted */ 492 visit(rel, sym); 493 } 494 else { 495 die("Unsupported relocation type: %d\n", r_type); 496 } 497 } 498 } 499} 500 501static void count_reloc(Elf32_Rel *rel, Elf32_Sym *sym) 502{ 503 reloc_count += 1; 504} 505 506static void collect_reloc(Elf32_Rel *rel, Elf32_Sym *sym) 507{ 508 /* Remember the address that needs to be adjusted. */ 509 relocs[reloc_idx++] = rel->r_offset; 510} 511 512static int cmp_relocs(const void *va, const void *vb) 513{ 514 const unsigned long *a, *b; 515 a = va; b = vb; 516 return (*a == *b)? 0 : (*a > *b)? 1 : -1; 517} 518 519static void emit_relocs(int as_text) 520{ 521 int i; 522 /* Count how many relocations I have and allocate space for them. */ 523 reloc_count = 0; 524 walk_relocs(count_reloc); 525 relocs = malloc(reloc_count * sizeof(relocs[0])); 526 if (!relocs) { 527 die("malloc of %d entries for relocs failed\n", 528 reloc_count); 529 } 530 /* Collect up the relocations */ 531 reloc_idx = 0; 532 walk_relocs(collect_reloc); 533 534 /* Order the relocations for more efficient processing */ 535 qsort(relocs, reloc_count, sizeof(relocs[0]), cmp_relocs); 536 537 /* Print the relocations */ 538 if (as_text) { 539 /* Print the relocations in a form suitable that 540 * gas will like. 541 */ 542 printf(".section \".data.reloc\",\"a\"\n"); 543 printf(".balign 4\n"); 544 for(i = 0; i < reloc_count; i++) { 545 printf("\t .long 0x%08lx\n", relocs[i]); 546 } 547 printf("\n"); 548 } 549 else { 550 unsigned char buf[4]; 551 buf[0] = buf[1] = buf[2] = buf[3] = 0; 552 /* Print a stop */ 553 printf("%c%c%c%c", buf[0], buf[1], buf[2], buf[3]); 554 /* Now print each relocation */ 555 for(i = 0; i < reloc_count; i++) { 556 buf[0] = (relocs[i] >> 0) & 0xff; 557 buf[1] = (relocs[i] >> 8) & 0xff; 558 buf[2] = (relocs[i] >> 16) & 0xff; 559 buf[3] = (relocs[i] >> 24) & 0xff; 560 printf("%c%c%c%c", buf[0], buf[1], buf[2], buf[3]); 561 } 562 } 563} 564 565static void usage(void) 566{ 567 die("relocs [--abs-syms |--abs-relocs | --text] vmlinux\n"); 568} 569 570int main(int argc, char **argv) 571{ 572 int show_absolute_syms, show_absolute_relocs; 573 int as_text; 574 const char *fname; 575 FILE *fp; 576 int i; 577 578 show_absolute_syms = 0; 579 show_absolute_relocs = 0; 580 as_text = 0; 581 fname = NULL; 582 for(i = 1; i < argc; i++) { 583 char *arg = argv[i]; 584 if (*arg == '-') { 585 if (strcmp(argv[1], "--abs-syms") == 0) { 586 show_absolute_syms = 1; 587 continue; 588 } 589 590 if (strcmp(argv[1], "--abs-relocs") == 0) { 591 show_absolute_relocs = 1; 592 continue; 593 } 594 else if (strcmp(argv[1], "--text") == 0) { 595 as_text = 1; 596 continue; 597 } 598 } 599 else if (!fname) { 600 fname = arg; 601 continue; 602 } 603 usage(); 604 } 605 if (!fname) { 606 usage(); 607 } 608 fp = fopen(fname, "r"); 609 if (!fp) { 610 die("Cannot open %s: %s\n", 611 fname, strerror(errno)); 612 } 613 read_ehdr(fp); 614 read_shdrs(fp); 615 read_strtabs(fp); 616 read_symtabs(fp); 617 read_relocs(fp); 618 if (show_absolute_syms) { 619 print_absolute_symbols(); 620 return 0; 621 } 622 if (show_absolute_relocs) { 623 print_absolute_relocs(); 624 return 0; 625 } 626 emit_relocs(as_text); 627 return 0; 628} 629