1 //===- ELF.cpp - ELF object file implementation ---------------------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 10 #include "llvm/Object/ELF.h" 11 #include "llvm/BinaryFormat/ELF.h" 12 #include "llvm/Support/LEB128.h" 13 14 using namespace llvm; 15 using namespace object; 16 17 #define STRINGIFY_ENUM_CASE(ns, name) \ 18 case ns::name: \ 19 return #name; 20 21 #define ELF_RELOC(name, value) STRINGIFY_ENUM_CASE(ELF, name) 22 23 StringRef llvm::object::getELFRelocationTypeName(uint32_t Machine, 24 uint32_t Type) { 25 switch (Machine) { 26 case ELF::EM_X86_64: 27 switch (Type) { 28 #include "llvm/BinaryFormat/ELFRelocs/x86_64.def" 29 default: 30 break; 31 } 32 break; 33 case ELF::EM_386: 34 case ELF::EM_IAMCU: 35 switch (Type) { 36 #include "llvm/BinaryFormat/ELFRelocs/i386.def" 37 default: 38 break; 39 } 40 break; 41 case ELF::EM_MIPS: 42 switch (Type) { 43 #include "llvm/BinaryFormat/ELFRelocs/Mips.def" 44 default: 45 break; 46 } 47 break; 48 case ELF::EM_AARCH64: 49 switch (Type) { 50 #include "llvm/BinaryFormat/ELFRelocs/AArch64.def" 51 default: 52 break; 53 } 54 break; 55 case ELF::EM_ARM: 56 switch (Type) { 57 #include "llvm/BinaryFormat/ELFRelocs/ARM.def" 58 default: 59 break; 60 } 61 break; 62 case ELF::EM_ARC_COMPACT: 63 case ELF::EM_ARC_COMPACT2: 64 switch (Type) { 65 #include "llvm/BinaryFormat/ELFRelocs/ARC.def" 66 default: 67 break; 68 } 69 break; 70 case ELF::EM_AVR: 71 switch (Type) { 72 #include "llvm/BinaryFormat/ELFRelocs/AVR.def" 73 default: 74 break; 75 } 76 break; 77 case ELF::EM_HEXAGON: 78 switch (Type) { 79 #include "llvm/BinaryFormat/ELFRelocs/Hexagon.def" 80 default: 81 break; 82 } 83 break; 84 case ELF::EM_LANAI: 85 switch (Type) { 86 #include "llvm/BinaryFormat/ELFRelocs/Lanai.def" 87 default: 88 break; 89 } 90 break; 91 case ELF::EM_PPC: 92 switch (Type) { 93 #include "llvm/BinaryFormat/ELFRelocs/PowerPC.def" 94 default: 95 break; 96 } 97 break; 98 case ELF::EM_PPC64: 99 switch (Type) { 100 #include "llvm/BinaryFormat/ELFRelocs/PowerPC64.def" 101 default: 102 break; 103 } 104 break; 105 case ELF::EM_RISCV: 106 switch (Type) { 107 #include "llvm/BinaryFormat/ELFRelocs/RISCV.def" 108 default: 109 break; 110 } 111 break; 112 case ELF::EM_S390: 113 switch (Type) { 114 #include "llvm/BinaryFormat/ELFRelocs/SystemZ.def" 115 default: 116 break; 117 } 118 break; 119 case ELF::EM_SPARC: 120 case ELF::EM_SPARC32PLUS: 121 case ELF::EM_SPARCV9: 122 switch (Type) { 123 #include "llvm/BinaryFormat/ELFRelocs/Sparc.def" 124 default: 125 break; 126 } 127 break; 128 case ELF::EM_WEBASSEMBLY: 129 switch (Type) { 130 #include "llvm/BinaryFormat/ELFRelocs/WebAssembly.def" 131 default: 132 break; 133 } 134 break; 135 case ELF::EM_AMDGPU: 136 switch (Type) { 137 #include "llvm/BinaryFormat/ELFRelocs/AMDGPU.def" 138 default: 139 break; 140 } 141 break; 142 case ELF::EM_BPF: 143 switch (Type) { 144 #include "llvm/BinaryFormat/ELFRelocs/BPF.def" 145 default: 146 break; 147 } 148 break; 149 default: 150 break; 151 } 152 return "Unknown"; 153 } 154 155 #undef ELF_RELOC 156 157 uint32_t llvm::object::getELFRelrRelocationType(uint32_t Machine) { 158 switch (Machine) { 159 case ELF::EM_X86_64: 160 return ELF::R_X86_64_RELATIVE; 161 case ELF::EM_386: 162 case ELF::EM_IAMCU: 163 return ELF::R_386_RELATIVE; 164 case ELF::EM_MIPS: 165 break; 166 case ELF::EM_AARCH64: 167 return ELF::R_AARCH64_RELATIVE; 168 case ELF::EM_ARM: 169 return ELF::R_ARM_RELATIVE; 170 case ELF::EM_ARC_COMPACT: 171 case ELF::EM_ARC_COMPACT2: 172 return ELF::R_ARC_RELATIVE; 173 case ELF::EM_AVR: 174 break; 175 case ELF::EM_HEXAGON: 176 return ELF::R_HEX_RELATIVE; 177 case ELF::EM_LANAI: 178 break; 179 case ELF::EM_PPC: 180 break; 181 case ELF::EM_PPC64: 182 return ELF::R_PPC64_RELATIVE; 183 case ELF::EM_RISCV: 184 return ELF::R_RISCV_RELATIVE; 185 case ELF::EM_S390: 186 return ELF::R_390_RELATIVE; 187 case ELF::EM_SPARC: 188 case ELF::EM_SPARC32PLUS: 189 case ELF::EM_SPARCV9: 190 return ELF::R_SPARC_RELATIVE; 191 case ELF::EM_WEBASSEMBLY: 192 break; 193 case ELF::EM_AMDGPU: 194 break; 195 case ELF::EM_BPF: 196 break; 197 default: 198 break; 199 } 200 return 0; 201 } 202 203 StringRef llvm::object::getELFSectionTypeName(uint32_t Machine, unsigned Type) { 204 switch (Machine) { 205 case ELF::EM_ARM: 206 switch (Type) { 207 STRINGIFY_ENUM_CASE(ELF, SHT_ARM_EXIDX); 208 STRINGIFY_ENUM_CASE(ELF, SHT_ARM_PREEMPTMAP); 209 STRINGIFY_ENUM_CASE(ELF, SHT_ARM_ATTRIBUTES); 210 STRINGIFY_ENUM_CASE(ELF, SHT_ARM_DEBUGOVERLAY); 211 STRINGIFY_ENUM_CASE(ELF, SHT_ARM_OVERLAYSECTION); 212 } 213 break; 214 case ELF::EM_HEXAGON: 215 switch (Type) { STRINGIFY_ENUM_CASE(ELF, SHT_HEX_ORDERED); } 216 break; 217 case ELF::EM_X86_64: 218 switch (Type) { STRINGIFY_ENUM_CASE(ELF, SHT_X86_64_UNWIND); } 219 break; 220 case ELF::EM_MIPS: 221 case ELF::EM_MIPS_RS3_LE: 222 switch (Type) { 223 STRINGIFY_ENUM_CASE(ELF, SHT_MIPS_REGINFO); 224 STRINGIFY_ENUM_CASE(ELF, SHT_MIPS_OPTIONS); 225 STRINGIFY_ENUM_CASE(ELF, SHT_MIPS_ABIFLAGS); 226 STRINGIFY_ENUM_CASE(ELF, SHT_MIPS_DWARF); 227 } 228 break; 229 default: 230 break; 231 } 232 233 switch (Type) { 234 STRINGIFY_ENUM_CASE(ELF, SHT_NULL); 235 STRINGIFY_ENUM_CASE(ELF, SHT_PROGBITS); 236 STRINGIFY_ENUM_CASE(ELF, SHT_SYMTAB); 237 STRINGIFY_ENUM_CASE(ELF, SHT_STRTAB); 238 STRINGIFY_ENUM_CASE(ELF, SHT_RELA); 239 STRINGIFY_ENUM_CASE(ELF, SHT_HASH); 240 STRINGIFY_ENUM_CASE(ELF, SHT_DYNAMIC); 241 STRINGIFY_ENUM_CASE(ELF, SHT_NOTE); 242 STRINGIFY_ENUM_CASE(ELF, SHT_NOBITS); 243 STRINGIFY_ENUM_CASE(ELF, SHT_REL); 244 STRINGIFY_ENUM_CASE(ELF, SHT_SHLIB); 245 STRINGIFY_ENUM_CASE(ELF, SHT_DYNSYM); 246 STRINGIFY_ENUM_CASE(ELF, SHT_INIT_ARRAY); 247 STRINGIFY_ENUM_CASE(ELF, SHT_FINI_ARRAY); 248 STRINGIFY_ENUM_CASE(ELF, SHT_PREINIT_ARRAY); 249 STRINGIFY_ENUM_CASE(ELF, SHT_GROUP); 250 STRINGIFY_ENUM_CASE(ELF, SHT_SYMTAB_SHNDX); 251 STRINGIFY_ENUM_CASE(ELF, SHT_RELR); 252 STRINGIFY_ENUM_CASE(ELF, SHT_ANDROID_REL); 253 STRINGIFY_ENUM_CASE(ELF, SHT_ANDROID_RELA); 254 STRINGIFY_ENUM_CASE(ELF, SHT_ANDROID_RELR); 255 STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_ODRTAB); 256 STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_LINKER_OPTIONS); 257 STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_CALL_GRAPH_PROFILE); 258 STRINGIFY_ENUM_CASE(ELF, SHT_GNU_ATTRIBUTES); 259 STRINGIFY_ENUM_CASE(ELF, SHT_GNU_HASH); 260 STRINGIFY_ENUM_CASE(ELF, SHT_GNU_verdef); 261 STRINGIFY_ENUM_CASE(ELF, SHT_GNU_verneed); 262 STRINGIFY_ENUM_CASE(ELF, SHT_GNU_versym); 263 default: 264 return "Unknown"; 265 } 266 } 267 268 template <class ELFT> 269 Expected<std::vector<typename ELFT::Rela>> 270 ELFFile<ELFT>::decode_relrs(Elf_Relr_Range relrs) const { 271 // This function decodes the contents of an SHT_RELR packed relocation 272 // section. 273 // 274 // Proposal for adding SHT_RELR sections to generic-abi is here: 275 // https://groups.google.com/forum/#!topic/generic-abi/bX460iggiKg 276 // 277 // The encoded sequence of Elf64_Relr entries in a SHT_RELR section looks 278 // like [ AAAAAAAA BBBBBBB1 BBBBBBB1 ... AAAAAAAA BBBBBB1 ... ] 279 // 280 // i.e. start with an address, followed by any number of bitmaps. The address 281 // entry encodes 1 relocation. The subsequent bitmap entries encode up to 63 282 // relocations each, at subsequent offsets following the last address entry. 283 // 284 // The bitmap entries must have 1 in the least significant bit. The assumption 285 // here is that an address cannot have 1 in lsb. Odd addresses are not 286 // supported. 287 // 288 // Excluding the least significant bit in the bitmap, each non-zero bit in 289 // the bitmap represents a relocation to be applied to a corresponding machine 290 // word that follows the base address word. The second least significant bit 291 // represents the machine word immediately following the initial address, and 292 // each bit that follows represents the next word, in linear order. As such, 293 // a single bitmap can encode up to 31 relocations in a 32-bit object, and 294 // 63 relocations in a 64-bit object. 295 // 296 // This encoding has a couple of interesting properties: 297 // 1. Looking at any entry, it is clear whether it's an address or a bitmap: 298 // even means address, odd means bitmap. 299 // 2. Just a simple list of addresses is a valid encoding. 300 301 Elf_Rela Rela; 302 Rela.r_info = 0; 303 Rela.r_addend = 0; 304 Rela.setType(getRelrRelocationType(), false); 305 std::vector<Elf_Rela> Relocs; 306 307 // Word type: uint32_t for Elf32, and uint64_t for Elf64. 308 typedef typename ELFT::uint Word; 309 310 // Word size in number of bytes. 311 const size_t WordSize = sizeof(Word); 312 313 // Number of bits used for the relocation offsets bitmap. 314 // These many relative relocations can be encoded in a single entry. 315 const size_t NBits = 8*WordSize - 1; 316 317 Word Base = 0; 318 for (const Elf_Relr &R : relrs) { 319 Word Entry = R; 320 if ((Entry&1) == 0) { 321 // Even entry: encodes the offset for next relocation. 322 Rela.r_offset = Entry; 323 Relocs.push_back(Rela); 324 // Set base offset for subsequent bitmap entries. 325 Base = Entry + WordSize; 326 continue; 327 } 328 329 // Odd entry: encodes bitmap for relocations starting at base. 330 Word Offset = Base; 331 while (Entry != 0) { 332 Entry >>= 1; 333 if ((Entry&1) != 0) { 334 Rela.r_offset = Offset; 335 Relocs.push_back(Rela); 336 } 337 Offset += WordSize; 338 } 339 340 // Advance base offset by NBits words. 341 Base += NBits * WordSize; 342 } 343 344 return Relocs; 345 } 346 347 template <class ELFT> 348 Expected<std::vector<typename ELFT::Rela>> 349 ELFFile<ELFT>::android_relas(const Elf_Shdr *Sec) const { 350 // This function reads relocations in Android's packed relocation format, 351 // which is based on SLEB128 and delta encoding. 352 Expected<ArrayRef<uint8_t>> ContentsOrErr = getSectionContents(Sec); 353 if (!ContentsOrErr) 354 return ContentsOrErr.takeError(); 355 const uint8_t *Cur = ContentsOrErr->begin(); 356 const uint8_t *End = ContentsOrErr->end(); 357 if (ContentsOrErr->size() < 4 || Cur[0] != 'A' || Cur[1] != 'P' || 358 Cur[2] != 'S' || Cur[3] != '2') 359 return createError("invalid packed relocation header"); 360 Cur += 4; 361 362 const char *ErrStr = nullptr; 363 auto ReadSLEB = [&]() -> int64_t { 364 if (ErrStr) 365 return 0; 366 unsigned Len; 367 int64_t Result = decodeSLEB128(Cur, &Len, End, &ErrStr); 368 Cur += Len; 369 return Result; 370 }; 371 372 uint64_t NumRelocs = ReadSLEB(); 373 uint64_t Offset = ReadSLEB(); 374 uint64_t Addend = 0; 375 376 if (ErrStr) 377 return createError(ErrStr); 378 379 std::vector<Elf_Rela> Relocs; 380 Relocs.reserve(NumRelocs); 381 while (NumRelocs) { 382 uint64_t NumRelocsInGroup = ReadSLEB(); 383 if (NumRelocsInGroup > NumRelocs) 384 return createError("relocation group unexpectedly large"); 385 NumRelocs -= NumRelocsInGroup; 386 387 uint64_t GroupFlags = ReadSLEB(); 388 bool GroupedByInfo = GroupFlags & ELF::RELOCATION_GROUPED_BY_INFO_FLAG; 389 bool GroupedByOffsetDelta = GroupFlags & ELF::RELOCATION_GROUPED_BY_OFFSET_DELTA_FLAG; 390 bool GroupedByAddend = GroupFlags & ELF::RELOCATION_GROUPED_BY_ADDEND_FLAG; 391 bool GroupHasAddend = GroupFlags & ELF::RELOCATION_GROUP_HAS_ADDEND_FLAG; 392 393 uint64_t GroupOffsetDelta; 394 if (GroupedByOffsetDelta) 395 GroupOffsetDelta = ReadSLEB(); 396 397 uint64_t GroupRInfo; 398 if (GroupedByInfo) 399 GroupRInfo = ReadSLEB(); 400 401 if (GroupedByAddend && GroupHasAddend) 402 Addend += ReadSLEB(); 403 404 for (uint64_t I = 0; I != NumRelocsInGroup; ++I) { 405 Elf_Rela R; 406 Offset += GroupedByOffsetDelta ? GroupOffsetDelta : ReadSLEB(); 407 R.r_offset = Offset; 408 R.r_info = GroupedByInfo ? GroupRInfo : ReadSLEB(); 409 410 if (GroupHasAddend) { 411 if (!GroupedByAddend) 412 Addend += ReadSLEB(); 413 R.r_addend = Addend; 414 } else { 415 R.r_addend = 0; 416 } 417 418 Relocs.push_back(R); 419 420 if (ErrStr) 421 return createError(ErrStr); 422 } 423 424 if (ErrStr) 425 return createError(ErrStr); 426 } 427 428 return Relocs; 429 } 430 431 template class llvm::object::ELFFile<ELF32LE>; 432 template class llvm::object::ELFFile<ELF32BE>; 433 template class llvm::object::ELFFile<ELF64LE>; 434 template class llvm::object::ELFFile<ELF64BE>; 435