1 /* 2 * Copyright (C) 2012 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #include "elf_file.h" 18 19 #include "base/logging.h" 20 #include "base/stl_util.h" 21 #include "utils.h" 22 23 namespace art { 24 25 ElfFile::ElfFile() 26 : file_(NULL), 27 writable_(false), 28 program_header_only_(false), 29 header_(NULL), 30 base_address_(NULL), 31 program_headers_start_(NULL), 32 section_headers_start_(NULL), 33 dynamic_program_header_(NULL), 34 dynamic_section_start_(NULL), 35 symtab_section_start_(NULL), 36 dynsym_section_start_(NULL), 37 strtab_section_start_(NULL), 38 dynstr_section_start_(NULL), 39 hash_section_start_(NULL), 40 symtab_symbol_table_(NULL), 41 dynsym_symbol_table_(NULL) {} 42 43 ElfFile* ElfFile::Open(File* file, bool writable, bool program_header_only) { 44 UniquePtr<ElfFile> elf_file(new ElfFile()); 45 if (!elf_file->Setup(file, writable, program_header_only)) { 46 return NULL; 47 } 48 return elf_file.release(); 49 } 50 51 bool ElfFile::Setup(File* file, bool writable, bool program_header_only) { 52 CHECK(file != NULL); 53 file_ = file; 54 writable_ = writable; 55 program_header_only_ = program_header_only; 56 57 int prot; 58 int flags; 59 if (writable_) { 60 prot = PROT_READ | PROT_WRITE; 61 flags = MAP_SHARED; 62 } else { 63 prot = PROT_READ; 64 flags = MAP_PRIVATE; 65 } 66 int64_t file_length = file_->GetLength(); 67 if (file_length < 0) { 68 errno = -file_length; 69 PLOG(WARNING) << "Failed to get length of file: " << file_->GetPath() << " fd=" << file_->Fd(); 70 return false; 71 } 72 if (file_length < sizeof(llvm::ELF::Elf32_Ehdr)) { 73 if (writable) { 74 LOG(WARNING) << "File size of " << file_length 75 << " bytes not large enough to contain ELF header of " 76 << sizeof(llvm::ELF::Elf32_Ehdr) << " bytes: " << file_->GetPath(); 77 } 78 return false; 79 } 80 81 if (program_header_only) { 82 // first just map ELF header to get program header size information 83 size_t elf_header_size = sizeof(llvm::ELF::Elf32_Ehdr); 84 if (!SetMap(MemMap::MapFile(elf_header_size, prot, flags, file_->Fd(), 0))) { 85 return false; 86 } 87 // then remap to cover program header 88 size_t program_header_size = header_->e_phoff + (header_->e_phentsize * header_->e_phnum); 89 if (file_length < program_header_size) { 90 LOG(WARNING) << "File size of " << file_length 91 << " bytes not large enough to contain ELF program header of " 92 << program_header_size << " bytes: " << file_->GetPath(); 93 return false; 94 } 95 if (!SetMap(MemMap::MapFile(program_header_size, prot, flags, file_->Fd(), 0))) { 96 LOG(WARNING) << "Failed to map ELF program headers: " << file_->GetPath(); 97 return false; 98 } 99 } else { 100 // otherwise map entire file 101 if (!SetMap(MemMap::MapFile(file_->GetLength(), prot, flags, file_->Fd(), 0))) { 102 LOG(WARNING) << "Failed to map ELF file: " << file_->GetPath(); 103 return false; 104 } 105 } 106 107 // Either way, the program header is relative to the elf header 108 program_headers_start_ = Begin() + GetHeader().e_phoff; 109 110 if (!program_header_only) { 111 // Setup section headers. 112 section_headers_start_ = Begin() + GetHeader().e_shoff; 113 114 // Find .dynamic section info from program header 115 dynamic_program_header_ = FindProgamHeaderByType(llvm::ELF::PT_DYNAMIC); 116 if (dynamic_program_header_ == NULL) { 117 LOG(WARNING) << "Failed to find PT_DYNAMIC program header in ELF file: " << file_->GetPath(); 118 return false; 119 } 120 121 dynamic_section_start_ 122 = reinterpret_cast<llvm::ELF::Elf32_Dyn*>(Begin() + GetDynamicProgramHeader().p_offset); 123 124 // Find other sections from section headers 125 for (llvm::ELF::Elf32_Word i = 0; i < GetSectionHeaderNum(); i++) { 126 llvm::ELF::Elf32_Shdr& section_header = GetSectionHeader(i); 127 byte* section_addr = Begin() + section_header.sh_offset; 128 switch (section_header.sh_type) { 129 case llvm::ELF::SHT_SYMTAB: { 130 symtab_section_start_ = reinterpret_cast<llvm::ELF::Elf32_Sym*>(section_addr); 131 break; 132 } 133 case llvm::ELF::SHT_DYNSYM: { 134 dynsym_section_start_ = reinterpret_cast<llvm::ELF::Elf32_Sym*>(section_addr); 135 break; 136 } 137 case llvm::ELF::SHT_STRTAB: { 138 // TODO: base these off of sh_link from .symtab and .dynsym above 139 if ((section_header.sh_flags & llvm::ELF::SHF_ALLOC) != 0) { 140 dynstr_section_start_ = reinterpret_cast<char*>(section_addr); 141 } else { 142 strtab_section_start_ = reinterpret_cast<char*>(section_addr); 143 } 144 break; 145 } 146 case llvm::ELF::SHT_DYNAMIC: { 147 if (reinterpret_cast<byte*>(dynamic_section_start_) != section_addr) { 148 LOG(WARNING) << "Failed to find matching SHT_DYNAMIC for PT_DYNAMIC in " 149 << file_->GetPath() << ": " << std::hex 150 << reinterpret_cast<void*>(dynamic_section_start_) 151 << " != " << reinterpret_cast<void*>(section_addr); 152 return false; 153 } 154 break; 155 } 156 case llvm::ELF::SHT_HASH: { 157 hash_section_start_ = reinterpret_cast<llvm::ELF::Elf32_Word*>(section_addr); 158 break; 159 } 160 } 161 } 162 } 163 return true; 164 } 165 166 ElfFile::~ElfFile() { 167 STLDeleteElements(&segments_); 168 delete symtab_symbol_table_; 169 delete dynsym_symbol_table_; 170 } 171 172 bool ElfFile::SetMap(MemMap* map) { 173 if (map == NULL) { 174 // MemMap::Open should have already logged 175 return false; 176 } 177 map_.reset(map); 178 CHECK(map_.get() != NULL) << file_->GetPath(); 179 CHECK(map_->Begin() != NULL) << file_->GetPath(); 180 181 header_ = reinterpret_cast<llvm::ELF::Elf32_Ehdr*>(map_->Begin()); 182 if ((llvm::ELF::ElfMagic[0] != header_->e_ident[llvm::ELF::EI_MAG0]) 183 || (llvm::ELF::ElfMagic[1] != header_->e_ident[llvm::ELF::EI_MAG1]) 184 || (llvm::ELF::ElfMagic[2] != header_->e_ident[llvm::ELF::EI_MAG2]) 185 || (llvm::ELF::ElfMagic[3] != header_->e_ident[llvm::ELF::EI_MAG3])) { 186 LOG(WARNING) << "Failed to find ELF magic in " << file_->GetPath() 187 << ": " << std::hex 188 << static_cast<uint8_t>(header_->e_ident[llvm::ELF::EI_MAG0]) 189 << static_cast<uint8_t>(header_->e_ident[llvm::ELF::EI_MAG1]) 190 << static_cast<uint8_t>(header_->e_ident[llvm::ELF::EI_MAG2]) 191 << static_cast<uint8_t>(header_->e_ident[llvm::ELF::EI_MAG3]); 192 return false; 193 } 194 195 196 // TODO: remove these static_casts from enum when using -std=gnu++0x 197 CHECK_EQ(static_cast<unsigned char>(llvm::ELF::ELFCLASS32), header_->e_ident[llvm::ELF::EI_CLASS]) << file_->GetPath(); 198 CHECK_EQ(static_cast<unsigned char>(llvm::ELF::ELFDATA2LSB), header_->e_ident[llvm::ELF::EI_DATA]) << file_->GetPath(); 199 CHECK_EQ(static_cast<unsigned char>(llvm::ELF::EV_CURRENT), header_->e_ident[llvm::ELF::EI_VERSION]) << file_->GetPath(); 200 201 // TODO: remove these static_casts from enum when using -std=gnu++0x 202 CHECK_EQ(static_cast<llvm::ELF::Elf32_Half>(llvm::ELF::ET_DYN), header_->e_type) << file_->GetPath(); 203 CHECK_EQ(static_cast<llvm::ELF::Elf32_Word>(llvm::ELF::EV_CURRENT), header_->e_version) << file_->GetPath(); 204 CHECK_EQ(0U, header_->e_entry) << file_->GetPath(); 205 206 CHECK_NE(0U, header_->e_phoff) << file_->GetPath(); 207 CHECK_NE(0U, header_->e_shoff) << file_->GetPath(); 208 CHECK_NE(0U, header_->e_ehsize) << file_->GetPath(); 209 CHECK_NE(0U, header_->e_phentsize) << file_->GetPath(); 210 CHECK_NE(0U, header_->e_phnum) << file_->GetPath(); 211 CHECK_NE(0U, header_->e_shentsize) << file_->GetPath(); 212 CHECK_NE(0U, header_->e_shnum) << file_->GetPath(); 213 CHECK_NE(0U, header_->e_shstrndx) << file_->GetPath(); 214 CHECK_GE(header_->e_shnum, header_->e_shstrndx) << file_->GetPath(); 215 if (!program_header_only_) { 216 CHECK_GT(Size(), header_->e_phoff) << file_->GetPath(); 217 CHECK_GT(Size(), header_->e_shoff) << file_->GetPath(); 218 } 219 return true; 220 } 221 222 223 llvm::ELF::Elf32_Ehdr& ElfFile::GetHeader() { 224 CHECK(header_ != NULL); 225 return *header_; 226 } 227 228 byte* ElfFile::GetProgramHeadersStart() { 229 CHECK(program_headers_start_ != NULL); 230 return program_headers_start_; 231 } 232 233 byte* ElfFile::GetSectionHeadersStart() { 234 CHECK(section_headers_start_ != NULL); 235 return section_headers_start_; 236 } 237 238 llvm::ELF::Elf32_Phdr& ElfFile::GetDynamicProgramHeader() { 239 CHECK(dynamic_program_header_ != NULL); 240 return *dynamic_program_header_; 241 } 242 243 llvm::ELF::Elf32_Dyn* ElfFile::GetDynamicSectionStart() { 244 CHECK(dynamic_section_start_ != NULL); 245 return dynamic_section_start_; 246 } 247 248 llvm::ELF::Elf32_Sym* ElfFile::GetSymbolSectionStart(llvm::ELF::Elf32_Word section_type) { 249 CHECK(IsSymbolSectionType(section_type)) << file_->GetPath() << " " << section_type; 250 llvm::ELF::Elf32_Sym* symbol_section_start; 251 switch (section_type) { 252 case llvm::ELF::SHT_SYMTAB: { 253 symbol_section_start = symtab_section_start_; 254 break; 255 } 256 case llvm::ELF::SHT_DYNSYM: { 257 symbol_section_start = dynsym_section_start_; 258 break; 259 } 260 default: { 261 LOG(FATAL) << section_type; 262 symbol_section_start = NULL; 263 } 264 } 265 CHECK(symbol_section_start != NULL); 266 return symbol_section_start; 267 } 268 269 const char* ElfFile::GetStringSectionStart(llvm::ELF::Elf32_Word section_type) { 270 CHECK(IsSymbolSectionType(section_type)) << file_->GetPath() << " " << section_type; 271 const char* string_section_start; 272 switch (section_type) { 273 case llvm::ELF::SHT_SYMTAB: { 274 string_section_start = strtab_section_start_; 275 break; 276 } 277 case llvm::ELF::SHT_DYNSYM: { 278 string_section_start = dynstr_section_start_; 279 break; 280 } 281 default: { 282 LOG(FATAL) << section_type; 283 string_section_start = NULL; 284 } 285 } 286 CHECK(string_section_start != NULL); 287 return string_section_start; 288 } 289 290 const char* ElfFile::GetString(llvm::ELF::Elf32_Word section_type, llvm::ELF::Elf32_Word i) { 291 CHECK(IsSymbolSectionType(section_type)) << file_->GetPath() << " " << section_type; 292 if (i == 0) { 293 return NULL; 294 } 295 const char* string_section_start = GetStringSectionStart(section_type); 296 const char* string = string_section_start + i; 297 return string; 298 } 299 300 llvm::ELF::Elf32_Word* ElfFile::GetHashSectionStart() { 301 CHECK(hash_section_start_ != NULL); 302 return hash_section_start_; 303 } 304 305 llvm::ELF::Elf32_Word ElfFile::GetHashBucketNum() { 306 return GetHashSectionStart()[0]; 307 } 308 309 llvm::ELF::Elf32_Word ElfFile::GetHashChainNum() { 310 return GetHashSectionStart()[1]; 311 } 312 313 llvm::ELF::Elf32_Word ElfFile::GetHashBucket(size_t i) { 314 CHECK_LT(i, GetHashBucketNum()); 315 // 0 is nbucket, 1 is nchain 316 return GetHashSectionStart()[2 + i]; 317 } 318 319 llvm::ELF::Elf32_Word ElfFile::GetHashChain(size_t i) { 320 CHECK_LT(i, GetHashChainNum()); 321 // 0 is nbucket, 1 is nchain, & chains are after buckets 322 return GetHashSectionStart()[2 + GetHashBucketNum() + i]; 323 } 324 325 llvm::ELF::Elf32_Word ElfFile::GetProgramHeaderNum() { 326 return GetHeader().e_phnum; 327 } 328 329 llvm::ELF::Elf32_Phdr& ElfFile::GetProgramHeader(llvm::ELF::Elf32_Word i) { 330 CHECK_LT(i, GetProgramHeaderNum()) << file_->GetPath(); 331 byte* program_header = GetProgramHeadersStart() + (i * GetHeader().e_phentsize); 332 CHECK_LT(program_header, End()) << file_->GetPath(); 333 return *reinterpret_cast<llvm::ELF::Elf32_Phdr*>(program_header); 334 } 335 336 llvm::ELF::Elf32_Phdr* ElfFile::FindProgamHeaderByType(llvm::ELF::Elf32_Word type) { 337 for (llvm::ELF::Elf32_Word i = 0; i < GetProgramHeaderNum(); i++) { 338 llvm::ELF::Elf32_Phdr& program_header = GetProgramHeader(i); 339 if (program_header.p_type == type) { 340 return &program_header; 341 } 342 } 343 return NULL; 344 } 345 346 llvm::ELF::Elf32_Word ElfFile::GetSectionHeaderNum() { 347 return GetHeader().e_shnum; 348 } 349 350 llvm::ELF::Elf32_Shdr& ElfFile::GetSectionHeader(llvm::ELF::Elf32_Word i) { 351 // Can only access arbitrary sections when we have the whole file, not just program header. 352 // Even if we Load(), it doesn't bring in all the sections. 353 CHECK(!program_header_only_) << file_->GetPath(); 354 CHECK_LT(i, GetSectionHeaderNum()) << file_->GetPath(); 355 byte* section_header = GetSectionHeadersStart() + (i * GetHeader().e_shentsize); 356 CHECK_LT(section_header, End()) << file_->GetPath(); 357 return *reinterpret_cast<llvm::ELF::Elf32_Shdr*>(section_header); 358 } 359 360 llvm::ELF::Elf32_Shdr* ElfFile::FindSectionByType(llvm::ELF::Elf32_Word type) { 361 // Can only access arbitrary sections when we have the whole file, not just program header. 362 // We could change this to switch on known types if they were detected during loading. 363 CHECK(!program_header_only_) << file_->GetPath(); 364 for (llvm::ELF::Elf32_Word i = 0; i < GetSectionHeaderNum(); i++) { 365 llvm::ELF::Elf32_Shdr& section_header = GetSectionHeader(i); 366 if (section_header.sh_type == type) { 367 return §ion_header; 368 } 369 } 370 return NULL; 371 } 372 373 // from bionic 374 static unsigned elfhash(const char *_name) { 375 const unsigned char *name = (const unsigned char *) _name; 376 unsigned h = 0, g; 377 378 while (*name) { 379 h = (h << 4) + *name++; 380 g = h & 0xf0000000; 381 h ^= g; 382 h ^= g >> 24; 383 } 384 return h; 385 } 386 387 llvm::ELF::Elf32_Shdr& ElfFile::GetSectionNameStringSection() { 388 return GetSectionHeader(GetHeader().e_shstrndx); 389 } 390 391 byte* ElfFile::FindDynamicSymbolAddress(const std::string& symbol_name) { 392 llvm::ELF::Elf32_Word hash = elfhash(symbol_name.c_str()); 393 llvm::ELF::Elf32_Word bucket_index = hash % GetHashBucketNum(); 394 llvm::ELF::Elf32_Word symbol_and_chain_index = GetHashBucket(bucket_index); 395 while (symbol_and_chain_index != 0 /* STN_UNDEF */) { 396 llvm::ELF::Elf32_Sym& symbol = GetSymbol(llvm::ELF::SHT_DYNSYM, symbol_and_chain_index); 397 const char* name = GetString(llvm::ELF::SHT_DYNSYM, symbol.st_name); 398 if (symbol_name == name) { 399 return base_address_ + symbol.st_value; 400 } 401 symbol_and_chain_index = GetHashChain(symbol_and_chain_index); 402 } 403 return NULL; 404 } 405 406 bool ElfFile::IsSymbolSectionType(llvm::ELF::Elf32_Word section_type) { 407 return ((section_type == llvm::ELF::SHT_SYMTAB) || (section_type == llvm::ELF::SHT_DYNSYM)); 408 } 409 410 llvm::ELF::Elf32_Word ElfFile::GetSymbolNum(llvm::ELF::Elf32_Shdr& section_header) { 411 CHECK(IsSymbolSectionType(section_header.sh_type)) << file_->GetPath() << " " << section_header.sh_type; 412 CHECK_NE(0U, section_header.sh_entsize) << file_->GetPath(); 413 return section_header.sh_size / section_header.sh_entsize; 414 } 415 416 llvm::ELF::Elf32_Sym& ElfFile::GetSymbol(llvm::ELF::Elf32_Word section_type, 417 llvm::ELF::Elf32_Word i) { 418 return *(GetSymbolSectionStart(section_type) + i); 419 } 420 421 ElfFile::SymbolTable** ElfFile::GetSymbolTable(llvm::ELF::Elf32_Word section_type) { 422 CHECK(IsSymbolSectionType(section_type)) << file_->GetPath() << " " << section_type; 423 switch (section_type) { 424 case llvm::ELF::SHT_SYMTAB: { 425 return &symtab_symbol_table_; 426 } 427 case llvm::ELF::SHT_DYNSYM: { 428 return &dynsym_symbol_table_; 429 } 430 default: { 431 LOG(FATAL) << section_type; 432 return NULL; 433 } 434 } 435 } 436 437 llvm::ELF::Elf32_Sym* ElfFile::FindSymbolByName(llvm::ELF::Elf32_Word section_type, 438 const std::string& symbol_name, 439 bool build_map) { 440 CHECK(!program_header_only_) << file_->GetPath(); 441 CHECK(IsSymbolSectionType(section_type)) << file_->GetPath() << " " << section_type; 442 443 SymbolTable** symbol_table = GetSymbolTable(section_type); 444 if (*symbol_table != NULL || build_map) { 445 if (*symbol_table == NULL) { 446 DCHECK(build_map); 447 *symbol_table = new SymbolTable; 448 llvm::ELF::Elf32_Shdr* symbol_section = FindSectionByType(section_type); 449 CHECK(symbol_section != NULL) << file_->GetPath(); 450 llvm::ELF::Elf32_Shdr& string_section = GetSectionHeader(symbol_section->sh_link); 451 for (uint32_t i = 0; i < GetSymbolNum(*symbol_section); i++) { 452 llvm::ELF::Elf32_Sym& symbol = GetSymbol(section_type, i); 453 unsigned char type = symbol.getType(); 454 if (type == llvm::ELF::STT_NOTYPE) { 455 continue; 456 } 457 const char* name = GetString(string_section, symbol.st_name); 458 if (name == NULL) { 459 continue; 460 } 461 std::pair<SymbolTable::iterator, bool> result = (*symbol_table)->insert(std::make_pair(name, &symbol)); 462 if (!result.second) { 463 // If a duplicate, make sure it has the same logical value. Seen on x86. 464 CHECK_EQ(symbol.st_value, result.first->second->st_value); 465 CHECK_EQ(symbol.st_size, result.first->second->st_size); 466 CHECK_EQ(symbol.st_info, result.first->second->st_info); 467 CHECK_EQ(symbol.st_other, result.first->second->st_other); 468 CHECK_EQ(symbol.st_shndx, result.first->second->st_shndx); 469 } 470 } 471 } 472 CHECK(*symbol_table != NULL); 473 SymbolTable::const_iterator it = (*symbol_table)->find(symbol_name); 474 if (it == (*symbol_table)->end()) { 475 return NULL; 476 } 477 return it->second; 478 } 479 480 // Fall back to linear search 481 llvm::ELF::Elf32_Shdr* symbol_section = FindSectionByType(section_type); 482 CHECK(symbol_section != NULL) << file_->GetPath(); 483 llvm::ELF::Elf32_Shdr& string_section = GetSectionHeader(symbol_section->sh_link); 484 for (uint32_t i = 0; i < GetSymbolNum(*symbol_section); i++) { 485 llvm::ELF::Elf32_Sym& symbol = GetSymbol(section_type, i); 486 const char* name = GetString(string_section, symbol.st_name); 487 if (name == NULL) { 488 continue; 489 } 490 if (symbol_name == name) { 491 return &symbol; 492 } 493 } 494 return NULL; 495 } 496 497 llvm::ELF::Elf32_Addr ElfFile::FindSymbolAddress(llvm::ELF::Elf32_Word section_type, 498 const std::string& symbol_name, 499 bool build_map) { 500 llvm::ELF::Elf32_Sym* symbol = FindSymbolByName(section_type, symbol_name, build_map); 501 if (symbol == NULL) { 502 return 0; 503 } 504 return symbol->st_value; 505 } 506 507 const char* ElfFile::GetString(llvm::ELF::Elf32_Shdr& string_section, llvm::ELF::Elf32_Word i) { 508 CHECK(!program_header_only_) << file_->GetPath(); 509 // TODO: remove this static_cast from enum when using -std=gnu++0x 510 CHECK_EQ(static_cast<llvm::ELF::Elf32_Word>(llvm::ELF::SHT_STRTAB), string_section.sh_type) << file_->GetPath(); 511 CHECK_LT(i, string_section.sh_size) << file_->GetPath(); 512 if (i == 0) { 513 return NULL; 514 } 515 byte* strings = Begin() + string_section.sh_offset; 516 byte* string = strings + i; 517 CHECK_LT(string, End()) << file_->GetPath(); 518 return reinterpret_cast<const char*>(string); 519 } 520 521 llvm::ELF::Elf32_Word ElfFile::GetDynamicNum() { 522 return GetDynamicProgramHeader().p_filesz / sizeof(llvm::ELF::Elf32_Dyn); 523 } 524 525 llvm::ELF::Elf32_Dyn& ElfFile::GetDynamic(llvm::ELF::Elf32_Word i) { 526 CHECK_LT(i, GetDynamicNum()) << file_->GetPath(); 527 return *(GetDynamicSectionStart() + i); 528 } 529 530 llvm::ELF::Elf32_Word ElfFile::FindDynamicValueByType(llvm::ELF::Elf32_Sword type) { 531 for (llvm::ELF::Elf32_Word i = 0; i < GetDynamicNum(); i++) { 532 llvm::ELF::Elf32_Dyn& elf_dyn = GetDynamic(i); 533 if (elf_dyn.d_tag == type) { 534 return elf_dyn.d_un.d_val; 535 } 536 } 537 return 0; 538 } 539 540 llvm::ELF::Elf32_Rel* ElfFile::GetRelSectionStart(llvm::ELF::Elf32_Shdr& section_header) { 541 CHECK(llvm::ELF::SHT_REL == section_header.sh_type) << file_->GetPath() << " " << section_header.sh_type; 542 return reinterpret_cast<llvm::ELF::Elf32_Rel*>(Begin() + section_header.sh_offset); 543 } 544 545 llvm::ELF::Elf32_Word ElfFile::GetRelNum(llvm::ELF::Elf32_Shdr& section_header) { 546 CHECK(llvm::ELF::SHT_REL == section_header.sh_type) << file_->GetPath() << " " << section_header.sh_type; 547 CHECK_NE(0U, section_header.sh_entsize) << file_->GetPath(); 548 return section_header.sh_size / section_header.sh_entsize; 549 } 550 551 llvm::ELF::Elf32_Rel& ElfFile::GetRel(llvm::ELF::Elf32_Shdr& section_header, llvm::ELF::Elf32_Word i) { 552 CHECK(llvm::ELF::SHT_REL == section_header.sh_type) << file_->GetPath() << " " << section_header.sh_type; 553 CHECK_LT(i, GetRelNum(section_header)) << file_->GetPath(); 554 return *(GetRelSectionStart(section_header) + i); 555 } 556 557 llvm::ELF::Elf32_Rela* ElfFile::GetRelaSectionStart(llvm::ELF::Elf32_Shdr& section_header) { 558 CHECK(llvm::ELF::SHT_RELA == section_header.sh_type) << file_->GetPath() << " " << section_header.sh_type; 559 return reinterpret_cast<llvm::ELF::Elf32_Rela*>(Begin() + section_header.sh_offset); 560 } 561 562 llvm::ELF::Elf32_Word ElfFile::GetRelaNum(llvm::ELF::Elf32_Shdr& section_header) { 563 CHECK(llvm::ELF::SHT_RELA == section_header.sh_type) << file_->GetPath() << " " << section_header.sh_type; 564 return section_header.sh_size / section_header.sh_entsize; 565 } 566 567 llvm::ELF::Elf32_Rela& ElfFile::GetRela(llvm::ELF::Elf32_Shdr& section_header, 568 llvm::ELF::Elf32_Word i) { 569 CHECK(llvm::ELF::SHT_RELA == section_header.sh_type) << file_->GetPath() << " " << section_header.sh_type; 570 CHECK_LT(i, GetRelaNum(section_header)) << file_->GetPath(); 571 return *(GetRelaSectionStart(section_header) + i); 572 } 573 574 // Base on bionic phdr_table_get_load_size 575 size_t ElfFile::GetLoadedSize() { 576 llvm::ELF::Elf32_Addr min_vaddr = 0xFFFFFFFFu; 577 llvm::ELF::Elf32_Addr max_vaddr = 0x00000000u; 578 for (llvm::ELF::Elf32_Word i = 0; i < GetProgramHeaderNum(); i++) { 579 llvm::ELF::Elf32_Phdr& program_header = GetProgramHeader(i); 580 if (program_header.p_type != llvm::ELF::PT_LOAD) { 581 continue; 582 } 583 llvm::ELF::Elf32_Addr begin_vaddr = program_header.p_vaddr; 584 if (begin_vaddr < min_vaddr) { 585 min_vaddr = begin_vaddr; 586 } 587 llvm::ELF::Elf32_Addr end_vaddr = program_header.p_vaddr + program_header.p_memsz; 588 if (end_vaddr > max_vaddr) { 589 max_vaddr = end_vaddr; 590 } 591 } 592 min_vaddr = RoundDown(min_vaddr, kPageSize); 593 max_vaddr = RoundUp(max_vaddr, kPageSize); 594 CHECK_LT(min_vaddr, max_vaddr) << file_->GetPath(); 595 size_t loaded_size = max_vaddr - min_vaddr; 596 return loaded_size; 597 } 598 599 bool ElfFile::Load(bool executable) { 600 // TODO: actually return false error 601 CHECK(program_header_only_) << file_->GetPath(); 602 for (llvm::ELF::Elf32_Word i = 0; i < GetProgramHeaderNum(); i++) { 603 llvm::ELF::Elf32_Phdr& program_header = GetProgramHeader(i); 604 605 // Record .dynamic header information for later use 606 if (program_header.p_type == llvm::ELF::PT_DYNAMIC) { 607 dynamic_program_header_ = &program_header; 608 continue; 609 } 610 611 // Not something to load, move on. 612 if (program_header.p_type != llvm::ELF::PT_LOAD) { 613 continue; 614 } 615 616 // Found something to load. 617 618 // If p_vaddr is zero, it must be the first loadable segment, 619 // since they must be in order. Since it is zero, there isn't a 620 // specific address requested, so first request a contiguous chunk 621 // of required size for all segments, but with no 622 // permissions. We'll then carve that up with the proper 623 // permissions as we load the actual segments. If p_vaddr is 624 // non-zero, the segments require the specific address specified, 625 // which either was specified in the file because we already set 626 // base_address_ after the first zero segment). 627 int64_t file_length = file_->GetLength(); 628 if (program_header.p_vaddr == 0) { 629 std::string reservation_name("ElfFile reservation for "); 630 reservation_name += file_->GetPath(); 631 UniquePtr<MemMap> reserve(MemMap::MapAnonymous(reservation_name.c_str(), 632 NULL, GetLoadedSize(), PROT_NONE)); 633 CHECK(reserve.get() != NULL) << file_->GetPath(); 634 base_address_ = reserve->Begin(); 635 segments_.push_back(reserve.release()); 636 } 637 // empty segment, nothing to map 638 if (program_header.p_memsz == 0) { 639 continue; 640 } 641 byte* p_vaddr = base_address_ + program_header.p_vaddr; 642 int prot = 0; 643 if (executable && ((program_header.p_flags & llvm::ELF::PF_X) != 0)) { 644 prot |= PROT_EXEC; 645 } 646 if ((program_header.p_flags & llvm::ELF::PF_W) != 0) { 647 prot |= PROT_WRITE; 648 } 649 if ((program_header.p_flags & llvm::ELF::PF_R) != 0) { 650 prot |= PROT_READ; 651 } 652 int flags = MAP_FIXED; 653 if (writable_) { 654 prot |= PROT_WRITE; 655 flags |= MAP_SHARED; 656 } else { 657 flags |= MAP_PRIVATE; 658 } 659 if (file_length < (program_header.p_offset + program_header.p_memsz)) { 660 LOG(WARNING) << "File size of " << file_length 661 << " bytes not large enough to contain ELF segment " << i 662 << " of " << (program_header.p_offset + program_header.p_memsz) 663 << " bytes: " << file_->GetPath(); 664 return false; 665 } 666 UniquePtr<MemMap> segment(MemMap::MapFileAtAddress(p_vaddr, 667 program_header.p_memsz, 668 prot, flags, file_->Fd(), 669 program_header.p_offset, 670 true)); 671 CHECK(segment.get() != NULL) << file_->GetPath(); 672 CHECK_EQ(segment->Begin(), p_vaddr) << file_->GetPath(); 673 segments_.push_back(segment.release()); 674 } 675 676 // Now that we are done loading, .dynamic should be in memory to find .dynstr, .dynsym, .hash 677 dynamic_section_start_ 678 = reinterpret_cast<llvm::ELF::Elf32_Dyn*>(base_address_ + GetDynamicProgramHeader().p_vaddr); 679 for (llvm::ELF::Elf32_Word i = 0; i < GetDynamicNum(); i++) { 680 llvm::ELF::Elf32_Dyn& elf_dyn = GetDynamic(i); 681 byte* d_ptr = base_address_ + elf_dyn.d_un.d_ptr; 682 switch (elf_dyn.d_tag) { 683 case llvm::ELF::DT_HASH: { 684 hash_section_start_ = reinterpret_cast<llvm::ELF::Elf32_Word*>(d_ptr); 685 break; 686 } 687 case llvm::ELF::DT_STRTAB: { 688 dynstr_section_start_ = reinterpret_cast<char*>(d_ptr); 689 break; 690 } 691 case llvm::ELF::DT_SYMTAB: { 692 dynsym_section_start_ = reinterpret_cast<llvm::ELF::Elf32_Sym*>(d_ptr); 693 break; 694 } 695 case llvm::ELF::DT_NULL: { 696 CHECK_EQ(GetDynamicNum(), i+1); 697 break; 698 } 699 } 700 } 701 702 return true; 703 } 704 705 } // namespace art 706
