1 //===-- ELFHeader.cpp -----------------------------------------------------===// 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 <cstring> 10 11 #include "lldb/Core/Section.h" 12 #include "lldb/Utility/DataExtractor.h" 13 #include "lldb/Utility/Stream.h" 14 15 #include "ELFHeader.h" 16 17 using namespace elf; 18 using namespace lldb; 19 using namespace llvm::ELF; 20 21 // Static utility functions. 22 // 23 // GetMaxU64 and GetMaxS64 wrap the similarly named methods from DataExtractor 24 // with error handling code and provide for parsing a sequence of values. 25 static bool GetMaxU64(const lldb_private::DataExtractor &data, 26 lldb::offset_t *offset, uint64_t *value, 27 uint32_t byte_size) { 28 const lldb::offset_t saved_offset = *offset; 29 *value = data.GetMaxU64(offset, byte_size); 30 return *offset != saved_offset; 31 } 32 33 static bool GetMaxU64(const lldb_private::DataExtractor &data, 34 lldb::offset_t *offset, uint64_t *value, 35 uint32_t byte_size, uint32_t count) { 36 lldb::offset_t saved_offset = *offset; 37 38 for (uint32_t i = 0; i < count; ++i, ++value) { 39 if (!GetMaxU64(data, offset, value, byte_size)) { 40 *offset = saved_offset; 41 return false; 42 } 43 } 44 return true; 45 } 46 47 static bool GetMaxS64(const lldb_private::DataExtractor &data, 48 lldb::offset_t *offset, int64_t *value, 49 uint32_t byte_size) { 50 const lldb::offset_t saved_offset = *offset; 51 *value = data.GetMaxS64(offset, byte_size); 52 return *offset != saved_offset; 53 } 54 55 static bool GetMaxS64(const lldb_private::DataExtractor &data, 56 lldb::offset_t *offset, int64_t *value, 57 uint32_t byte_size, uint32_t count) { 58 lldb::offset_t saved_offset = *offset; 59 60 for (uint32_t i = 0; i < count; ++i, ++value) { 61 if (!GetMaxS64(data, offset, value, byte_size)) { 62 *offset = saved_offset; 63 return false; 64 } 65 } 66 return true; 67 } 68 69 // ELFHeader 70 71 ELFHeader::ELFHeader() { memset(this, 0, sizeof(ELFHeader)); } 72 73 ByteOrder ELFHeader::GetByteOrder() const { 74 if (e_ident[EI_DATA] == ELFDATA2MSB) 75 return eByteOrderBig; 76 if (e_ident[EI_DATA] == ELFDATA2LSB) 77 return eByteOrderLittle; 78 return eByteOrderInvalid; 79 } 80 81 bool ELFHeader::HasHeaderExtension() const { 82 bool result = false; 83 84 // Check if any of these values looks like sentinel. 85 result |= e_phnum_hdr == 0xFFFF; // PN_XNUM 86 result |= e_shnum_hdr == SHN_UNDEF; 87 result |= e_shstrndx_hdr == SHN_XINDEX; 88 89 // If header extension is present, the section offset cannot be null. 90 result &= e_shoff != 0; 91 92 // Done. 93 return result; 94 } 95 96 void ELFHeader::ParseHeaderExtension(lldb_private::DataExtractor &data) { 97 // Extract section #0 header. 98 ELFSectionHeader section_zero; 99 lldb::offset_t offset = 0; 100 lldb_private::DataExtractor sh_data(data, e_shoff, e_shentsize); 101 bool ok = section_zero.Parse(sh_data, &offset); 102 103 // If we succeeded, fix the header. 104 if (ok) { 105 if (e_phnum_hdr == 0xFFFF) // PN_XNUM 106 e_phnum = section_zero.sh_info; 107 if (e_shnum_hdr == SHN_UNDEF) 108 e_shnum = section_zero.sh_size; 109 if (e_shstrndx_hdr == SHN_XINDEX) 110 e_shstrndx = section_zero.sh_link; 111 } 112 } 113 114 bool ELFHeader::Parse(lldb_private::DataExtractor &data, 115 lldb::offset_t *offset) { 116 // Read e_ident. This provides byte order and address size info. 117 if (data.GetU8(offset, &e_ident, EI_NIDENT) == nullptr) 118 return false; 119 120 const unsigned byte_size = Is32Bit() ? 4 : 8; 121 data.SetByteOrder(GetByteOrder()); 122 data.SetAddressByteSize(byte_size); 123 124 // Read e_type and e_machine. 125 if (data.GetU16(offset, &e_type, 2) == nullptr) 126 return false; 127 128 // Read e_version. 129 if (data.GetU32(offset, &e_version, 1) == nullptr) 130 return false; 131 132 // Read e_entry, e_phoff and e_shoff. 133 if (!GetMaxU64(data, offset, &e_entry, byte_size, 3)) 134 return false; 135 136 // Read e_flags. 137 if (data.GetU32(offset, &e_flags, 1) == nullptr) 138 return false; 139 140 // Read e_ehsize, e_phentsize, e_phnum, e_shentsize, e_shnum and e_shstrndx. 141 if (data.GetU16(offset, &e_ehsize, 6) == nullptr) 142 return false; 143 144 // Initialize e_phnum, e_shnum, and e_shstrndx with the values read from the 145 // header. 146 e_phnum = e_phnum_hdr; 147 e_shnum = e_shnum_hdr; 148 e_shstrndx = e_shstrndx_hdr; 149 150 // See if we have extended header in section #0. 151 if (HasHeaderExtension()) 152 ParseHeaderExtension(data); 153 154 return true; 155 } 156 157 bool ELFHeader::MagicBytesMatch(const uint8_t *magic) { 158 return memcmp(magic, ElfMagic, strlen(ElfMagic)) == 0; 159 } 160 161 unsigned ELFHeader::AddressSizeInBytes(const uint8_t *magic) { 162 unsigned address_size = 0; 163 164 switch (magic[EI_CLASS]) { 165 case ELFCLASS32: 166 address_size = 4; 167 break; 168 169 case ELFCLASS64: 170 address_size = 8; 171 break; 172 } 173 return address_size; 174 } 175 176 unsigned ELFHeader::GetRelocationJumpSlotType() const { 177 unsigned slot = 0; 178 179 switch (e_machine) { 180 default: 181 assert(false && "architecture not supported"); 182 break; 183 case EM_PPC: 184 slot = R_PPC_JMP_SLOT; 185 break; 186 case EM_PPC64: 187 slot = R_PPC64_JMP_SLOT; 188 break; 189 case EM_386: 190 case EM_IAMCU: // FIXME: is this correct? 191 slot = R_386_JUMP_SLOT; 192 break; 193 case EM_X86_64: 194 slot = R_X86_64_JUMP_SLOT; 195 break; 196 case EM_ARM: 197 slot = R_ARM_JUMP_SLOT; 198 break; 199 case EM_HEXAGON: 200 slot = R_HEX_JMP_SLOT; 201 break; 202 case EM_AARCH64: 203 slot = R_AARCH64_JUMP_SLOT; 204 break; 205 case EM_MIPS: 206 slot = R_MIPS_JUMP_SLOT; 207 break; 208 case EM_S390: 209 slot = R_390_JMP_SLOT; 210 break; 211 case EM_RISCV: 212 slot = R_RISCV_JUMP_SLOT; 213 break; 214 } 215 216 return slot; 217 } 218 219 // ELFSectionHeader 220 221 ELFSectionHeader::ELFSectionHeader() { 222 memset(this, 0, sizeof(ELFSectionHeader)); 223 } 224 225 bool ELFSectionHeader::Parse(const lldb_private::DataExtractor &data, 226 lldb::offset_t *offset) { 227 const unsigned byte_size = data.GetAddressByteSize(); 228 229 // Read sh_name and sh_type. 230 if (data.GetU32(offset, &sh_name, 2) == nullptr) 231 return false; 232 233 // Read sh_flags. 234 if (!GetMaxU64(data, offset, &sh_flags, byte_size)) 235 return false; 236 237 // Read sh_addr, sh_off and sh_size. 238 if (!GetMaxU64(data, offset, &sh_addr, byte_size, 3)) 239 return false; 240 241 // Read sh_link and sh_info. 242 if (data.GetU32(offset, &sh_link, 2) == nullptr) 243 return false; 244 245 // Read sh_addralign and sh_entsize. 246 if (!GetMaxU64(data, offset, &sh_addralign, byte_size, 2)) 247 return false; 248 249 return true; 250 } 251 252 // ELFSymbol 253 254 ELFSymbol::ELFSymbol() { memset(this, 0, sizeof(ELFSymbol)); } 255 256 #define ENUM_TO_CSTR(e) \ 257 case e: \ 258 return #e 259 260 const char *ELFSymbol::bindingToCString(unsigned char binding) { 261 switch (binding) { 262 ENUM_TO_CSTR(STB_LOCAL); 263 ENUM_TO_CSTR(STB_GLOBAL); 264 ENUM_TO_CSTR(STB_WEAK); 265 ENUM_TO_CSTR(STB_LOOS); 266 ENUM_TO_CSTR(STB_HIOS); 267 ENUM_TO_CSTR(STB_LOPROC); 268 ENUM_TO_CSTR(STB_HIPROC); 269 } 270 return ""; 271 } 272 273 const char *ELFSymbol::typeToCString(unsigned char type) { 274 switch (type) { 275 ENUM_TO_CSTR(STT_NOTYPE); 276 ENUM_TO_CSTR(STT_OBJECT); 277 ENUM_TO_CSTR(STT_FUNC); 278 ENUM_TO_CSTR(STT_SECTION); 279 ENUM_TO_CSTR(STT_FILE); 280 ENUM_TO_CSTR(STT_COMMON); 281 ENUM_TO_CSTR(STT_TLS); 282 ENUM_TO_CSTR(STT_GNU_IFUNC); 283 ENUM_TO_CSTR(STT_HIOS); 284 ENUM_TO_CSTR(STT_LOPROC); 285 ENUM_TO_CSTR(STT_HIPROC); 286 } 287 return ""; 288 } 289 290 const char *ELFSymbol::sectionIndexToCString( 291 elf_half shndx, const lldb_private::SectionList *section_list) { 292 switch (shndx) { 293 ENUM_TO_CSTR(SHN_UNDEF); 294 ENUM_TO_CSTR(SHN_LOPROC); 295 ENUM_TO_CSTR(SHN_HIPROC); 296 ENUM_TO_CSTR(SHN_LOOS); 297 ENUM_TO_CSTR(SHN_HIOS); 298 ENUM_TO_CSTR(SHN_ABS); 299 ENUM_TO_CSTR(SHN_COMMON); 300 ENUM_TO_CSTR(SHN_XINDEX); 301 default: { 302 const lldb_private::Section *section = 303 section_list->GetSectionAtIndex(shndx).get(); 304 if (section) 305 return section->GetName().AsCString(""); 306 } break; 307 } 308 return ""; 309 } 310 311 void ELFSymbol::Dump(lldb_private::Stream *s, uint32_t idx, 312 const lldb_private::DataExtractor *strtab_data, 313 const lldb_private::SectionList *section_list) { 314 s->Printf("[%3u] 0x%16.16" PRIx64 " 0x%16.16" PRIx64 315 " 0x%8.8x 0x%2.2x (%-10s %-13s) 0x%2.2x 0x%4.4x (%-10s) %s\n", 316 idx, st_value, st_size, st_name, st_info, 317 bindingToCString(getBinding()), typeToCString(getType()), st_other, 318 st_shndx, sectionIndexToCString(st_shndx, section_list), 319 strtab_data ? strtab_data->PeekCStr(st_name) : ""); 320 } 321 322 bool ELFSymbol::Parse(const lldb_private::DataExtractor &data, 323 lldb::offset_t *offset) { 324 const unsigned byte_size = data.GetAddressByteSize(); 325 const bool parsing_32 = byte_size == 4; 326 327 // Read st_name. 328 if (data.GetU32(offset, &st_name, 1) == nullptr) 329 return false; 330 331 if (parsing_32) { 332 // Read st_value and st_size. 333 if (!GetMaxU64(data, offset, &st_value, byte_size, 2)) 334 return false; 335 336 // Read st_info and st_other. 337 if (data.GetU8(offset, &st_info, 2) == nullptr) 338 return false; 339 340 // Read st_shndx. 341 if (data.GetU16(offset, &st_shndx, 1) == nullptr) 342 return false; 343 } else { 344 // Read st_info and st_other. 345 if (data.GetU8(offset, &st_info, 2) == nullptr) 346 return false; 347 348 // Read st_shndx. 349 if (data.GetU16(offset, &st_shndx, 1) == nullptr) 350 return false; 351 352 // Read st_value and st_size. 353 if (data.GetU64(offset, &st_value, 2) == nullptr) 354 return false; 355 } 356 return true; 357 } 358 359 // ELFProgramHeader 360 361 ELFProgramHeader::ELFProgramHeader() { 362 memset(this, 0, sizeof(ELFProgramHeader)); 363 } 364 365 bool ELFProgramHeader::Parse(const lldb_private::DataExtractor &data, 366 lldb::offset_t *offset) { 367 const uint32_t byte_size = data.GetAddressByteSize(); 368 const bool parsing_32 = byte_size == 4; 369 370 // Read p_type; 371 if (data.GetU32(offset, &p_type, 1) == nullptr) 372 return false; 373 374 if (parsing_32) { 375 // Read p_offset, p_vaddr, p_paddr, p_filesz and p_memsz. 376 if (!GetMaxU64(data, offset, &p_offset, byte_size, 5)) 377 return false; 378 379 // Read p_flags. 380 if (data.GetU32(offset, &p_flags, 1) == nullptr) 381 return false; 382 383 // Read p_align. 384 if (!GetMaxU64(data, offset, &p_align, byte_size)) 385 return false; 386 } else { 387 // Read p_flags. 388 if (data.GetU32(offset, &p_flags, 1) == nullptr) 389 return false; 390 391 // Read p_offset, p_vaddr, p_paddr, p_filesz, p_memsz and p_align. 392 if (!GetMaxU64(data, offset, &p_offset, byte_size, 6)) 393 return false; 394 } 395 396 return true; 397 } 398 399 // ELFDynamic 400 401 ELFDynamic::ELFDynamic() { memset(this, 0, sizeof(ELFDynamic)); } 402 403 bool ELFDynamic::Parse(const lldb_private::DataExtractor &data, 404 lldb::offset_t *offset) { 405 const unsigned byte_size = data.GetAddressByteSize(); 406 return GetMaxS64(data, offset, &d_tag, byte_size, 2); 407 } 408 409 // ELFRel 410 411 ELFRel::ELFRel() { memset(this, 0, sizeof(ELFRel)); } 412 413 bool ELFRel::Parse(const lldb_private::DataExtractor &data, 414 lldb::offset_t *offset) { 415 const unsigned byte_size = data.GetAddressByteSize(); 416 417 // Read r_offset and r_info. 418 return GetMaxU64(data, offset, &r_offset, byte_size, 2) != false; 419 } 420 421 // ELFRela 422 423 ELFRela::ELFRela() { memset(this, 0, sizeof(ELFRela)); } 424 425 bool ELFRela::Parse(const lldb_private::DataExtractor &data, 426 lldb::offset_t *offset) { 427 const unsigned byte_size = data.GetAddressByteSize(); 428 429 // Read r_offset and r_info. 430 if (!GetMaxU64(data, offset, &r_offset, byte_size, 2)) 431 return false; 432 433 // Read r_addend; 434 if (!GetMaxS64(data, offset, &r_addend, byte_size)) 435 return false; 436 437 return true; 438 } 439