1 //===- ELF.cpp - ELF object file implementation ---------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #include "llvm/Object/ELF.h" 10 #include "llvm/BinaryFormat/ELF.h" 11 #include "llvm/Support/LEB128.h" 12 13 using namespace llvm; 14 using namespace object; 15 16 #define STRINGIFY_ENUM_CASE(ns, name) \ 17 case ns::name: \ 18 return #name; 19 20 #define ELF_RELOC(name, value) STRINGIFY_ENUM_CASE(ELF, name) 21 22 StringRef llvm::object::getELFRelocationTypeName(uint32_t Machine, 23 uint32_t Type) { 24 switch (Machine) { 25 case ELF::EM_X86_64: 26 switch (Type) { 27 #include "llvm/BinaryFormat/ELFRelocs/x86_64.def" 28 default: 29 break; 30 } 31 break; 32 case ELF::EM_386: 33 case ELF::EM_IAMCU: 34 switch (Type) { 35 #include "llvm/BinaryFormat/ELFRelocs/i386.def" 36 default: 37 break; 38 } 39 break; 40 case ELF::EM_MIPS: 41 switch (Type) { 42 #include "llvm/BinaryFormat/ELFRelocs/Mips.def" 43 default: 44 break; 45 } 46 break; 47 case ELF::EM_AARCH64: 48 switch (Type) { 49 #include "llvm/BinaryFormat/ELFRelocs/AArch64.def" 50 default: 51 break; 52 } 53 break; 54 case ELF::EM_ARM: 55 switch (Type) { 56 #include "llvm/BinaryFormat/ELFRelocs/ARM.def" 57 default: 58 break; 59 } 60 break; 61 case ELF::EM_ARC_COMPACT: 62 case ELF::EM_ARC_COMPACT2: 63 switch (Type) { 64 #include "llvm/BinaryFormat/ELFRelocs/ARC.def" 65 default: 66 break; 67 } 68 break; 69 case ELF::EM_AVR: 70 switch (Type) { 71 #include "llvm/BinaryFormat/ELFRelocs/AVR.def" 72 default: 73 break; 74 } 75 break; 76 case ELF::EM_HEXAGON: 77 switch (Type) { 78 #include "llvm/BinaryFormat/ELFRelocs/Hexagon.def" 79 default: 80 break; 81 } 82 break; 83 case ELF::EM_LANAI: 84 switch (Type) { 85 #include "llvm/BinaryFormat/ELFRelocs/Lanai.def" 86 default: 87 break; 88 } 89 break; 90 case ELF::EM_PPC: 91 switch (Type) { 92 #include "llvm/BinaryFormat/ELFRelocs/PowerPC.def" 93 default: 94 break; 95 } 96 break; 97 case ELF::EM_PPC64: 98 switch (Type) { 99 #include "llvm/BinaryFormat/ELFRelocs/PowerPC64.def" 100 default: 101 break; 102 } 103 break; 104 case ELF::EM_RISCV: 105 switch (Type) { 106 #include "llvm/BinaryFormat/ELFRelocs/RISCV.def" 107 default: 108 break; 109 } 110 break; 111 case ELF::EM_S390: 112 switch (Type) { 113 #include "llvm/BinaryFormat/ELFRelocs/SystemZ.def" 114 default: 115 break; 116 } 117 break; 118 case ELF::EM_SPARC: 119 case ELF::EM_SPARC32PLUS: 120 case ELF::EM_SPARCV9: 121 switch (Type) { 122 #include "llvm/BinaryFormat/ELFRelocs/Sparc.def" 123 default: 124 break; 125 } 126 break; 127 case ELF::EM_AMDGPU: 128 switch (Type) { 129 #include "llvm/BinaryFormat/ELFRelocs/AMDGPU.def" 130 default: 131 break; 132 } 133 break; 134 case ELF::EM_BPF: 135 switch (Type) { 136 #include "llvm/BinaryFormat/ELFRelocs/BPF.def" 137 default: 138 break; 139 } 140 break; 141 case ELF::EM_MSP430: 142 switch (Type) { 143 #include "llvm/BinaryFormat/ELFRelocs/MSP430.def" 144 default: 145 break; 146 } 147 break; 148 default: 149 break; 150 } 151 return "Unknown"; 152 } 153 154 #undef ELF_RELOC 155 156 uint32_t llvm::object::getELFRelativeRelocationType(uint32_t Machine) { 157 switch (Machine) { 158 case ELF::EM_X86_64: 159 return ELF::R_X86_64_RELATIVE; 160 case ELF::EM_386: 161 case ELF::EM_IAMCU: 162 return ELF::R_386_RELATIVE; 163 case ELF::EM_MIPS: 164 break; 165 case ELF::EM_AARCH64: 166 return ELF::R_AARCH64_RELATIVE; 167 case ELF::EM_ARM: 168 return ELF::R_ARM_RELATIVE; 169 case ELF::EM_ARC_COMPACT: 170 case ELF::EM_ARC_COMPACT2: 171 return ELF::R_ARC_RELATIVE; 172 case ELF::EM_AVR: 173 break; 174 case ELF::EM_HEXAGON: 175 return ELF::R_HEX_RELATIVE; 176 case ELF::EM_LANAI: 177 break; 178 case ELF::EM_PPC: 179 break; 180 case ELF::EM_PPC64: 181 return ELF::R_PPC64_RELATIVE; 182 case ELF::EM_RISCV: 183 return ELF::R_RISCV_RELATIVE; 184 case ELF::EM_S390: 185 return ELF::R_390_RELATIVE; 186 case ELF::EM_SPARC: 187 case ELF::EM_SPARC32PLUS: 188 case ELF::EM_SPARCV9: 189 return ELF::R_SPARC_RELATIVE; 190 case ELF::EM_AMDGPU: 191 break; 192 case ELF::EM_BPF: 193 break; 194 default: 195 break; 196 } 197 return 0; 198 } 199 200 StringRef llvm::object::getELFSectionTypeName(uint32_t Machine, unsigned Type) { 201 switch (Machine) { 202 case ELF::EM_ARM: 203 switch (Type) { 204 STRINGIFY_ENUM_CASE(ELF, SHT_ARM_EXIDX); 205 STRINGIFY_ENUM_CASE(ELF, SHT_ARM_PREEMPTMAP); 206 STRINGIFY_ENUM_CASE(ELF, SHT_ARM_ATTRIBUTES); 207 STRINGIFY_ENUM_CASE(ELF, SHT_ARM_DEBUGOVERLAY); 208 STRINGIFY_ENUM_CASE(ELF, SHT_ARM_OVERLAYSECTION); 209 } 210 break; 211 case ELF::EM_HEXAGON: 212 switch (Type) { STRINGIFY_ENUM_CASE(ELF, SHT_HEX_ORDERED); } 213 break; 214 case ELF::EM_X86_64: 215 switch (Type) { STRINGIFY_ENUM_CASE(ELF, SHT_X86_64_UNWIND); } 216 break; 217 case ELF::EM_MIPS: 218 case ELF::EM_MIPS_RS3_LE: 219 switch (Type) { 220 STRINGIFY_ENUM_CASE(ELF, SHT_MIPS_REGINFO); 221 STRINGIFY_ENUM_CASE(ELF, SHT_MIPS_OPTIONS); 222 STRINGIFY_ENUM_CASE(ELF, SHT_MIPS_DWARF); 223 STRINGIFY_ENUM_CASE(ELF, SHT_MIPS_ABIFLAGS); 224 } 225 break; 226 default: 227 break; 228 } 229 230 switch (Type) { 231 STRINGIFY_ENUM_CASE(ELF, SHT_NULL); 232 STRINGIFY_ENUM_CASE(ELF, SHT_PROGBITS); 233 STRINGIFY_ENUM_CASE(ELF, SHT_SYMTAB); 234 STRINGIFY_ENUM_CASE(ELF, SHT_STRTAB); 235 STRINGIFY_ENUM_CASE(ELF, SHT_RELA); 236 STRINGIFY_ENUM_CASE(ELF, SHT_HASH); 237 STRINGIFY_ENUM_CASE(ELF, SHT_DYNAMIC); 238 STRINGIFY_ENUM_CASE(ELF, SHT_NOTE); 239 STRINGIFY_ENUM_CASE(ELF, SHT_NOBITS); 240 STRINGIFY_ENUM_CASE(ELF, SHT_REL); 241 STRINGIFY_ENUM_CASE(ELF, SHT_SHLIB); 242 STRINGIFY_ENUM_CASE(ELF, SHT_DYNSYM); 243 STRINGIFY_ENUM_CASE(ELF, SHT_INIT_ARRAY); 244 STRINGIFY_ENUM_CASE(ELF, SHT_FINI_ARRAY); 245 STRINGIFY_ENUM_CASE(ELF, SHT_PREINIT_ARRAY); 246 STRINGIFY_ENUM_CASE(ELF, SHT_GROUP); 247 STRINGIFY_ENUM_CASE(ELF, SHT_SYMTAB_SHNDX); 248 STRINGIFY_ENUM_CASE(ELF, SHT_RELR); 249 STRINGIFY_ENUM_CASE(ELF, SHT_ANDROID_REL); 250 STRINGIFY_ENUM_CASE(ELF, SHT_ANDROID_RELA); 251 STRINGIFY_ENUM_CASE(ELF, SHT_ANDROID_RELR); 252 STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_ODRTAB); 253 STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_LINKER_OPTIONS); 254 STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_CALL_GRAPH_PROFILE); 255 STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_ADDRSIG); 256 STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_DEPENDENT_LIBRARIES); 257 STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_SYMPART); 258 STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_PART_EHDR); 259 STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_PART_PHDR); 260 STRINGIFY_ENUM_CASE(ELF, SHT_GNU_ATTRIBUTES); 261 STRINGIFY_ENUM_CASE(ELF, SHT_GNU_HASH); 262 STRINGIFY_ENUM_CASE(ELF, SHT_GNU_verdef); 263 STRINGIFY_ENUM_CASE(ELF, SHT_GNU_verneed); 264 STRINGIFY_ENUM_CASE(ELF, SHT_GNU_versym); 265 default: 266 return "Unknown"; 267 } 268 } 269 270 template <class ELFT> 271 Expected<std::vector<typename ELFT::Rela>> 272 ELFFile<ELFT>::decode_relrs(Elf_Relr_Range relrs) const { 273 // This function decodes the contents of an SHT_RELR packed relocation 274 // section. 275 // 276 // Proposal for adding SHT_RELR sections to generic-abi is here: 277 // https://groups.google.com/forum/#!topic/generic-abi/bX460iggiKg 278 // 279 // The encoded sequence of Elf64_Relr entries in a SHT_RELR section looks 280 // like [ AAAAAAAA BBBBBBB1 BBBBBBB1 ... AAAAAAAA BBBBBB1 ... ] 281 // 282 // i.e. start with an address, followed by any number of bitmaps. The address 283 // entry encodes 1 relocation. The subsequent bitmap entries encode up to 63 284 // relocations each, at subsequent offsets following the last address entry. 285 // 286 // The bitmap entries must have 1 in the least significant bit. The assumption 287 // here is that an address cannot have 1 in lsb. Odd addresses are not 288 // supported. 289 // 290 // Excluding the least significant bit in the bitmap, each non-zero bit in 291 // the bitmap represents a relocation to be applied to a corresponding machine 292 // word that follows the base address word. The second least significant bit 293 // represents the machine word immediately following the initial address, and 294 // each bit that follows represents the next word, in linear order. As such, 295 // a single bitmap can encode up to 31 relocations in a 32-bit object, and 296 // 63 relocations in a 64-bit object. 297 // 298 // This encoding has a couple of interesting properties: 299 // 1. Looking at any entry, it is clear whether it's an address or a bitmap: 300 // even means address, odd means bitmap. 301 // 2. Just a simple list of addresses is a valid encoding. 302 303 Elf_Rela Rela; 304 Rela.r_info = 0; 305 Rela.r_addend = 0; 306 Rela.setType(getRelativeRelocationType(), false); 307 std::vector<Elf_Rela> Relocs; 308 309 // Word type: uint32_t for Elf32, and uint64_t for Elf64. 310 typedef typename ELFT::uint Word; 311 312 // Word size in number of bytes. 313 const size_t WordSize = sizeof(Word); 314 315 // Number of bits used for the relocation offsets bitmap. 316 // These many relative relocations can be encoded in a single entry. 317 const size_t NBits = 8*WordSize - 1; 318 319 Word Base = 0; 320 for (const Elf_Relr &R : relrs) { 321 Word Entry = R; 322 if ((Entry&1) == 0) { 323 // Even entry: encodes the offset for next relocation. 324 Rela.r_offset = Entry; 325 Relocs.push_back(Rela); 326 // Set base offset for subsequent bitmap entries. 327 Base = Entry + WordSize; 328 continue; 329 } 330 331 // Odd entry: encodes bitmap for relocations starting at base. 332 Word Offset = Base; 333 while (Entry != 0) { 334 Entry >>= 1; 335 if ((Entry&1) != 0) { 336 Rela.r_offset = Offset; 337 Relocs.push_back(Rela); 338 } 339 Offset += WordSize; 340 } 341 342 // Advance base offset by NBits words. 343 Base += NBits * WordSize; 344 } 345 346 return Relocs; 347 } 348 349 template <class ELFT> 350 Expected<std::vector<typename ELFT::Rela>> 351 ELFFile<ELFT>::android_relas(const Elf_Shdr *Sec) const { 352 // This function reads relocations in Android's packed relocation format, 353 // which is based on SLEB128 and delta encoding. 354 Expected<ArrayRef<uint8_t>> ContentsOrErr = getSectionContents(Sec); 355 if (!ContentsOrErr) 356 return ContentsOrErr.takeError(); 357 const uint8_t *Cur = ContentsOrErr->begin(); 358 const uint8_t *End = ContentsOrErr->end(); 359 if (ContentsOrErr->size() < 4 || Cur[0] != 'A' || Cur[1] != 'P' || 360 Cur[2] != 'S' || Cur[3] != '2') 361 return createError("invalid packed relocation header"); 362 Cur += 4; 363 364 const char *ErrStr = nullptr; 365 auto ReadSLEB = [&]() -> int64_t { 366 if (ErrStr) 367 return 0; 368 unsigned Len; 369 int64_t Result = decodeSLEB128(Cur, &Len, End, &ErrStr); 370 Cur += Len; 371 return Result; 372 }; 373 374 uint64_t NumRelocs = ReadSLEB(); 375 uint64_t Offset = ReadSLEB(); 376 uint64_t Addend = 0; 377 378 if (ErrStr) 379 return createError(ErrStr); 380 381 std::vector<Elf_Rela> Relocs; 382 Relocs.reserve(NumRelocs); 383 while (NumRelocs) { 384 uint64_t NumRelocsInGroup = ReadSLEB(); 385 if (NumRelocsInGroup > NumRelocs) 386 return createError("relocation group unexpectedly large"); 387 NumRelocs -= NumRelocsInGroup; 388 389 uint64_t GroupFlags = ReadSLEB(); 390 bool GroupedByInfo = GroupFlags & ELF::RELOCATION_GROUPED_BY_INFO_FLAG; 391 bool GroupedByOffsetDelta = GroupFlags & ELF::RELOCATION_GROUPED_BY_OFFSET_DELTA_FLAG; 392 bool GroupedByAddend = GroupFlags & ELF::RELOCATION_GROUPED_BY_ADDEND_FLAG; 393 bool GroupHasAddend = GroupFlags & ELF::RELOCATION_GROUP_HAS_ADDEND_FLAG; 394 395 uint64_t GroupOffsetDelta; 396 if (GroupedByOffsetDelta) 397 GroupOffsetDelta = ReadSLEB(); 398 399 uint64_t GroupRInfo; 400 if (GroupedByInfo) 401 GroupRInfo = ReadSLEB(); 402 403 if (GroupedByAddend && GroupHasAddend) 404 Addend += ReadSLEB(); 405 406 if (!GroupHasAddend) 407 Addend = 0; 408 409 for (uint64_t I = 0; I != NumRelocsInGroup; ++I) { 410 Elf_Rela R; 411 Offset += GroupedByOffsetDelta ? GroupOffsetDelta : ReadSLEB(); 412 R.r_offset = Offset; 413 R.r_info = GroupedByInfo ? GroupRInfo : ReadSLEB(); 414 if (GroupHasAddend && !GroupedByAddend) 415 Addend += ReadSLEB(); 416 R.r_addend = Addend; 417 Relocs.push_back(R); 418 419 if (ErrStr) 420 return createError(ErrStr); 421 } 422 423 if (ErrStr) 424 return createError(ErrStr); 425 } 426 427 return Relocs; 428 } 429 430 template <class ELFT> 431 std::string ELFFile<ELFT>::getDynamicTagAsString(unsigned Arch, 432 uint64_t Type) const { 433 #define DYNAMIC_STRINGIFY_ENUM(tag, value) \ 434 case value: \ 435 return #tag; 436 437 #define DYNAMIC_TAG(n, v) 438 switch (Arch) { 439 case ELF::EM_AARCH64: 440 switch (Type) { 441 #define AARCH64_DYNAMIC_TAG(name, value) DYNAMIC_STRINGIFY_ENUM(name, value) 442 #include "llvm/BinaryFormat/DynamicTags.def" 443 #undef AARCH64_DYNAMIC_TAG 444 } 445 break; 446 447 case ELF::EM_HEXAGON: 448 switch (Type) { 449 #define HEXAGON_DYNAMIC_TAG(name, value) DYNAMIC_STRINGIFY_ENUM(name, value) 450 #include "llvm/BinaryFormat/DynamicTags.def" 451 #undef HEXAGON_DYNAMIC_TAG 452 } 453 break; 454 455 case ELF::EM_MIPS: 456 switch (Type) { 457 #define MIPS_DYNAMIC_TAG(name, value) DYNAMIC_STRINGIFY_ENUM(name, value) 458 #include "llvm/BinaryFormat/DynamicTags.def" 459 #undef MIPS_DYNAMIC_TAG 460 } 461 break; 462 463 case ELF::EM_PPC64: 464 switch (Type) { 465 #define PPC64_DYNAMIC_TAG(name, value) DYNAMIC_STRINGIFY_ENUM(name, value) 466 #include "llvm/BinaryFormat/DynamicTags.def" 467 #undef PPC64_DYNAMIC_TAG 468 } 469 break; 470 } 471 #undef DYNAMIC_TAG 472 switch (Type) { 473 // Now handle all dynamic tags except the architecture specific ones 474 #define AARCH64_DYNAMIC_TAG(name, value) 475 #define MIPS_DYNAMIC_TAG(name, value) 476 #define HEXAGON_DYNAMIC_TAG(name, value) 477 #define PPC64_DYNAMIC_TAG(name, value) 478 // Also ignore marker tags such as DT_HIOS (maps to DT_VERNEEDNUM), etc. 479 #define DYNAMIC_TAG_MARKER(name, value) 480 #define DYNAMIC_TAG(name, value) case value: return #name; 481 #include "llvm/BinaryFormat/DynamicTags.def" 482 #undef DYNAMIC_TAG 483 #undef AARCH64_DYNAMIC_TAG 484 #undef MIPS_DYNAMIC_TAG 485 #undef HEXAGON_DYNAMIC_TAG 486 #undef PPC64_DYNAMIC_TAG 487 #undef DYNAMIC_TAG_MARKER 488 #undef DYNAMIC_STRINGIFY_ENUM 489 default: 490 return "<unknown:>0x" + utohexstr(Type, true); 491 } 492 } 493 494 template <class ELFT> 495 std::string ELFFile<ELFT>::getDynamicTagAsString(uint64_t Type) const { 496 return getDynamicTagAsString(getHeader()->e_machine, Type); 497 } 498 499 template <class ELFT> 500 Expected<typename ELFT::DynRange> ELFFile<ELFT>::dynamicEntries() const { 501 ArrayRef<Elf_Dyn> Dyn; 502 size_t DynSecSize = 0; 503 504 auto ProgramHeadersOrError = program_headers(); 505 if (!ProgramHeadersOrError) 506 return ProgramHeadersOrError.takeError(); 507 508 for (const Elf_Phdr &Phdr : *ProgramHeadersOrError) { 509 if (Phdr.p_type == ELF::PT_DYNAMIC) { 510 Dyn = makeArrayRef( 511 reinterpret_cast<const Elf_Dyn *>(base() + Phdr.p_offset), 512 Phdr.p_filesz / sizeof(Elf_Dyn)); 513 DynSecSize = Phdr.p_filesz; 514 break; 515 } 516 } 517 518 // If we can't find the dynamic section in the program headers, we just fall 519 // back on the sections. 520 if (Dyn.empty()) { 521 auto SectionsOrError = sections(); 522 if (!SectionsOrError) 523 return SectionsOrError.takeError(); 524 525 for (const Elf_Shdr &Sec : *SectionsOrError) { 526 if (Sec.sh_type == ELF::SHT_DYNAMIC) { 527 Expected<ArrayRef<Elf_Dyn>> DynOrError = 528 getSectionContentsAsArray<Elf_Dyn>(&Sec); 529 if (!DynOrError) 530 return DynOrError.takeError(); 531 Dyn = *DynOrError; 532 DynSecSize = Sec.sh_size; 533 break; 534 } 535 } 536 537 if (!Dyn.data()) 538 return ArrayRef<Elf_Dyn>(); 539 } 540 541 if (Dyn.empty()) 542 // TODO: this error is untested. 543 return createError("invalid empty dynamic section"); 544 545 if (DynSecSize % sizeof(Elf_Dyn) != 0) 546 // TODO: this error is untested. 547 return createError("malformed dynamic section"); 548 549 if (Dyn.back().d_tag != ELF::DT_NULL) 550 // TODO: this error is untested. 551 return createError("dynamic sections must be DT_NULL terminated"); 552 553 return Dyn; 554 } 555 556 template <class ELFT> 557 Expected<const uint8_t *> ELFFile<ELFT>::toMappedAddr(uint64_t VAddr) const { 558 auto ProgramHeadersOrError = program_headers(); 559 if (!ProgramHeadersOrError) 560 return ProgramHeadersOrError.takeError(); 561 562 llvm::SmallVector<Elf_Phdr *, 4> LoadSegments; 563 564 for (const Elf_Phdr &Phdr : *ProgramHeadersOrError) 565 if (Phdr.p_type == ELF::PT_LOAD) 566 LoadSegments.push_back(const_cast<Elf_Phdr *>(&Phdr)); 567 568 const Elf_Phdr *const *I = 569 std::upper_bound(LoadSegments.begin(), LoadSegments.end(), VAddr, 570 [](uint64_t VAddr, const Elf_Phdr_Impl<ELFT> *Phdr) { 571 return VAddr < Phdr->p_vaddr; 572 }); 573 574 if (I == LoadSegments.begin()) 575 return createError("virtual address is not in any segment: 0x" + 576 Twine::utohexstr(VAddr)); 577 --I; 578 const Elf_Phdr &Phdr = **I; 579 uint64_t Delta = VAddr - Phdr.p_vaddr; 580 if (Delta >= Phdr.p_filesz) 581 return createError("virtual address is not in any segment: 0x" + 582 Twine::utohexstr(VAddr)); 583 return base() + Phdr.p_offset + Delta; 584 } 585 586 template class llvm::object::ELFFile<ELF32LE>; 587 template class llvm::object::ELFFile<ELF32BE>; 588 template class llvm::object::ELFFile<ELF64LE>; 589 template class llvm::object::ELFFile<ELF64BE>; 590