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_GNU_ATTRIBUTES); 258 STRINGIFY_ENUM_CASE(ELF, SHT_GNU_HASH); 259 STRINGIFY_ENUM_CASE(ELF, SHT_GNU_verdef); 260 STRINGIFY_ENUM_CASE(ELF, SHT_GNU_verneed); 261 STRINGIFY_ENUM_CASE(ELF, SHT_GNU_versym); 262 default: 263 return "Unknown"; 264 } 265 } 266 267 template <class ELFT> 268 Expected<std::vector<typename ELFT::Rela>> 269 ELFFile<ELFT>::decode_relrs(Elf_Relr_Range relrs) const { 270 // This function decodes the contents of an SHT_RELR packed relocation 271 // section. 272 // 273 // Proposal for adding SHT_RELR sections to generic-abi is here: 274 // https://groups.google.com/forum/#!topic/generic-abi/bX460iggiKg 275 // 276 // The encoded sequence of Elf64_Relr entries in a SHT_RELR section looks 277 // like [ AAAAAAAA BBBBBBB1 BBBBBBB1 ... AAAAAAAA BBBBBB1 ... ] 278 // 279 // i.e. start with an address, followed by any number of bitmaps. The address 280 // entry encodes 1 relocation. The subsequent bitmap entries encode up to 63 281 // relocations each, at subsequent offsets following the last address entry. 282 // 283 // The bitmap entries must have 1 in the least significant bit. The assumption 284 // here is that an address cannot have 1 in lsb. Odd addresses are not 285 // supported. 286 // 287 // Excluding the least significant bit in the bitmap, each non-zero bit in 288 // the bitmap represents a relocation to be applied to a corresponding machine 289 // word that follows the base address word. The second least significant bit 290 // represents the machine word immediately following the initial address, and 291 // each bit that follows represents the next word, in linear order. As such, 292 // a single bitmap can encode up to 31 relocations in a 32-bit object, and 293 // 63 relocations in a 64-bit object. 294 // 295 // This encoding has a couple of interesting properties: 296 // 1. Looking at any entry, it is clear whether it's an address or a bitmap: 297 // even means address, odd means bitmap. 298 // 2. Just a simple list of addresses is a valid encoding. 299 300 Elf_Rela Rela; 301 Rela.r_info = 0; 302 Rela.r_addend = 0; 303 Rela.setType(getRelativeRelocationType(), false); 304 std::vector<Elf_Rela> Relocs; 305 306 // Word type: uint32_t for Elf32, and uint64_t for Elf64. 307 typedef typename ELFT::uint Word; 308 309 // Word size in number of bytes. 310 const size_t WordSize = sizeof(Word); 311 312 // Number of bits used for the relocation offsets bitmap. 313 // These many relative relocations can be encoded in a single entry. 314 const size_t NBits = 8*WordSize - 1; 315 316 Word Base = 0; 317 for (const Elf_Relr &R : relrs) { 318 Word Entry = R; 319 if ((Entry&1) == 0) { 320 // Even entry: encodes the offset for next relocation. 321 Rela.r_offset = Entry; 322 Relocs.push_back(Rela); 323 // Set base offset for subsequent bitmap entries. 324 Base = Entry + WordSize; 325 continue; 326 } 327 328 // Odd entry: encodes bitmap for relocations starting at base. 329 Word Offset = Base; 330 while (Entry != 0) { 331 Entry >>= 1; 332 if ((Entry&1) != 0) { 333 Rela.r_offset = Offset; 334 Relocs.push_back(Rela); 335 } 336 Offset += WordSize; 337 } 338 339 // Advance base offset by NBits words. 340 Base += NBits * WordSize; 341 } 342 343 return Relocs; 344 } 345 346 template <class ELFT> 347 Expected<std::vector<typename ELFT::Rela>> 348 ELFFile<ELFT>::android_relas(const Elf_Shdr *Sec) const { 349 // This function reads relocations in Android's packed relocation format, 350 // which is based on SLEB128 and delta encoding. 351 Expected<ArrayRef<uint8_t>> ContentsOrErr = getSectionContents(Sec); 352 if (!ContentsOrErr) 353 return ContentsOrErr.takeError(); 354 const uint8_t *Cur = ContentsOrErr->begin(); 355 const uint8_t *End = ContentsOrErr->end(); 356 if (ContentsOrErr->size() < 4 || Cur[0] != 'A' || Cur[1] != 'P' || 357 Cur[2] != 'S' || Cur[3] != '2') 358 return createError("invalid packed relocation header"); 359 Cur += 4; 360 361 const char *ErrStr = nullptr; 362 auto ReadSLEB = [&]() -> int64_t { 363 if (ErrStr) 364 return 0; 365 unsigned Len; 366 int64_t Result = decodeSLEB128(Cur, &Len, End, &ErrStr); 367 Cur += Len; 368 return Result; 369 }; 370 371 uint64_t NumRelocs = ReadSLEB(); 372 uint64_t Offset = ReadSLEB(); 373 uint64_t Addend = 0; 374 375 if (ErrStr) 376 return createError(ErrStr); 377 378 std::vector<Elf_Rela> Relocs; 379 Relocs.reserve(NumRelocs); 380 while (NumRelocs) { 381 uint64_t NumRelocsInGroup = ReadSLEB(); 382 if (NumRelocsInGroup > NumRelocs) 383 return createError("relocation group unexpectedly large"); 384 NumRelocs -= NumRelocsInGroup; 385 386 uint64_t GroupFlags = ReadSLEB(); 387 bool GroupedByInfo = GroupFlags & ELF::RELOCATION_GROUPED_BY_INFO_FLAG; 388 bool GroupedByOffsetDelta = GroupFlags & ELF::RELOCATION_GROUPED_BY_OFFSET_DELTA_FLAG; 389 bool GroupedByAddend = GroupFlags & ELF::RELOCATION_GROUPED_BY_ADDEND_FLAG; 390 bool GroupHasAddend = GroupFlags & ELF::RELOCATION_GROUP_HAS_ADDEND_FLAG; 391 392 uint64_t GroupOffsetDelta; 393 if (GroupedByOffsetDelta) 394 GroupOffsetDelta = ReadSLEB(); 395 396 uint64_t GroupRInfo; 397 if (GroupedByInfo) 398 GroupRInfo = ReadSLEB(); 399 400 if (GroupedByAddend && GroupHasAddend) 401 Addend += ReadSLEB(); 402 403 if (!GroupHasAddend) 404 Addend = 0; 405 406 for (uint64_t I = 0; I != NumRelocsInGroup; ++I) { 407 Elf_Rela R; 408 Offset += GroupedByOffsetDelta ? GroupOffsetDelta : ReadSLEB(); 409 R.r_offset = Offset; 410 R.r_info = GroupedByInfo ? GroupRInfo : ReadSLEB(); 411 if (GroupHasAddend && !GroupedByAddend) 412 Addend += ReadSLEB(); 413 R.r_addend = Addend; 414 Relocs.push_back(R); 415 416 if (ErrStr) 417 return createError(ErrStr); 418 } 419 420 if (ErrStr) 421 return createError(ErrStr); 422 } 423 424 return Relocs; 425 } 426 427 template <class ELFT> 428 std::string ELFFile<ELFT>::getDynamicTagAsString(unsigned Arch, 429 uint64_t Type) const { 430 #define DYNAMIC_STRINGIFY_ENUM(tag, value) \ 431 case value: \ 432 return #tag; 433 434 #define DYNAMIC_TAG(n, v) 435 switch (Arch) { 436 case ELF::EM_HEXAGON: 437 switch (Type) { 438 #define HEXAGON_DYNAMIC_TAG(name, value) DYNAMIC_STRINGIFY_ENUM(name, value) 439 #include "llvm/BinaryFormat/DynamicTags.def" 440 #undef HEXAGON_DYNAMIC_TAG 441 } 442 break; 443 444 case ELF::EM_MIPS: 445 switch (Type) { 446 #define MIPS_DYNAMIC_TAG(name, value) DYNAMIC_STRINGIFY_ENUM(name, value) 447 #include "llvm/BinaryFormat/DynamicTags.def" 448 #undef MIPS_DYNAMIC_TAG 449 } 450 break; 451 452 case ELF::EM_PPC64: 453 switch (Type) { 454 #define PPC64_DYNAMIC_TAG(name, value) DYNAMIC_STRINGIFY_ENUM(name, value) 455 #include "llvm/BinaryFormat/DynamicTags.def" 456 #undef PPC64_DYNAMIC_TAG 457 } 458 break; 459 } 460 #undef DYNAMIC_TAG 461 switch (Type) { 462 // Now handle all dynamic tags except the architecture specific ones 463 #define MIPS_DYNAMIC_TAG(name, value) 464 #define HEXAGON_DYNAMIC_TAG(name, value) 465 #define PPC64_DYNAMIC_TAG(name, value) 466 // Also ignore marker tags such as DT_HIOS (maps to DT_VERNEEDNUM), etc. 467 #define DYNAMIC_TAG_MARKER(name, value) 468 #define DYNAMIC_TAG(name, value) DYNAMIC_STRINGIFY_ENUM(name, value) 469 #include "llvm/BinaryFormat/DynamicTags.def" 470 #undef DYNAMIC_TAG 471 #undef MIPS_DYNAMIC_TAG 472 #undef HEXAGON_DYNAMIC_TAG 473 #undef PPC64_DYNAMIC_TAG 474 #undef DYNAMIC_TAG_MARKER 475 #undef DYNAMIC_STRINGIFY_ENUM 476 default: 477 return "<unknown:>0x" + utohexstr(Type, true); 478 } 479 } 480 481 template <class ELFT> 482 std::string ELFFile<ELFT>::getDynamicTagAsString(uint64_t Type) const { 483 return getDynamicTagAsString(getHeader()->e_machine, Type); 484 } 485 486 template <class ELFT> 487 Expected<typename ELFT::DynRange> ELFFile<ELFT>::dynamicEntries() const { 488 ArrayRef<Elf_Dyn> Dyn; 489 size_t DynSecSize = 0; 490 491 auto ProgramHeadersOrError = program_headers(); 492 if (!ProgramHeadersOrError) 493 return ProgramHeadersOrError.takeError(); 494 495 for (const Elf_Phdr &Phdr : *ProgramHeadersOrError) { 496 if (Phdr.p_type == ELF::PT_DYNAMIC) { 497 Dyn = makeArrayRef( 498 reinterpret_cast<const Elf_Dyn *>(base() + Phdr.p_offset), 499 Phdr.p_filesz / sizeof(Elf_Dyn)); 500 DynSecSize = Phdr.p_filesz; 501 break; 502 } 503 } 504 505 // If we can't find the dynamic section in the program headers, we just fall 506 // back on the sections. 507 if (Dyn.empty()) { 508 auto SectionsOrError = sections(); 509 if (!SectionsOrError) 510 return SectionsOrError.takeError(); 511 512 for (const Elf_Shdr &Sec : *SectionsOrError) { 513 if (Sec.sh_type == ELF::SHT_DYNAMIC) { 514 Expected<ArrayRef<Elf_Dyn>> DynOrError = 515 getSectionContentsAsArray<Elf_Dyn>(&Sec); 516 if (!DynOrError) 517 return DynOrError.takeError(); 518 Dyn = *DynOrError; 519 DynSecSize = Sec.sh_size; 520 break; 521 } 522 } 523 524 if (!Dyn.data()) 525 return ArrayRef<Elf_Dyn>(); 526 } 527 528 if (Dyn.empty()) 529 return createError("invalid empty dynamic section"); 530 531 if (DynSecSize % sizeof(Elf_Dyn) != 0) 532 return createError("malformed dynamic section"); 533 534 if (Dyn.back().d_tag != ELF::DT_NULL) 535 return createError("dynamic sections must be DT_NULL terminated"); 536 537 return Dyn; 538 } 539 540 template <class ELFT> 541 Expected<const uint8_t *> ELFFile<ELFT>::toMappedAddr(uint64_t VAddr) const { 542 auto ProgramHeadersOrError = program_headers(); 543 if (!ProgramHeadersOrError) 544 return ProgramHeadersOrError.takeError(); 545 546 llvm::SmallVector<Elf_Phdr *, 4> LoadSegments; 547 548 for (const Elf_Phdr &Phdr : *ProgramHeadersOrError) 549 if (Phdr.p_type == ELF::PT_LOAD) 550 LoadSegments.push_back(const_cast<Elf_Phdr *>(&Phdr)); 551 552 const Elf_Phdr *const *I = 553 std::upper_bound(LoadSegments.begin(), LoadSegments.end(), VAddr, 554 [](uint64_t VAddr, const Elf_Phdr_Impl<ELFT> *Phdr) { 555 return VAddr < Phdr->p_vaddr; 556 }); 557 558 if (I == LoadSegments.begin()) 559 return createError("Virtual address is not in any segment"); 560 --I; 561 const Elf_Phdr &Phdr = **I; 562 uint64_t Delta = VAddr - Phdr.p_vaddr; 563 if (Delta >= Phdr.p_filesz) 564 return createError("Virtual address is not in any segment"); 565 return base() + Phdr.p_offset + Delta; 566 } 567 568 template class llvm::object::ELFFile<ELF32LE>; 569 template class llvm::object::ELFFile<ELF32BE>; 570 template class llvm::object::ELFFile<ELF64LE>; 571 template class llvm::object::ELFFile<ELF64BE>; 572