1 //=--------- MachOLinkGraphBuilder.cpp - MachO LinkGraph builder ----------===// 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 // Generic MachO LinkGraph buliding code. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #include "MachOLinkGraphBuilder.h" 14 15 #define DEBUG_TYPE "jitlink" 16 17 static const char *CommonSectionName = "__common"; 18 19 namespace llvm { 20 namespace jitlink { 21 22 MachOLinkGraphBuilder::~MachOLinkGraphBuilder() {} 23 24 Expected<std::unique_ptr<LinkGraph>> MachOLinkGraphBuilder::buildGraph() { 25 26 // We only operate on relocatable objects. 27 if (!Obj.isRelocatableObject()) 28 return make_error<JITLinkError>("Object is not a relocatable MachO"); 29 30 if (auto Err = createNormalizedSections()) 31 return std::move(Err); 32 33 if (auto Err = createNormalizedSymbols()) 34 return std::move(Err); 35 36 if (auto Err = graphifyRegularSymbols()) 37 return std::move(Err); 38 39 if (auto Err = graphifySectionsWithCustomParsers()) 40 return std::move(Err); 41 42 if (auto Err = addRelocations()) 43 return std::move(Err); 44 45 return std::move(G); 46 } 47 48 MachOLinkGraphBuilder::MachOLinkGraphBuilder( 49 const object::MachOObjectFile &Obj, Triple TT, 50 LinkGraph::GetEdgeKindNameFunction GetEdgeKindName) 51 : Obj(Obj), 52 G(std::make_unique<LinkGraph>( 53 std::string(Obj.getFileName()), std::move(TT), getPointerSize(Obj), 54 getEndianness(Obj), std::move(GetEdgeKindName))) {} 55 56 void MachOLinkGraphBuilder::addCustomSectionParser( 57 StringRef SectionName, SectionParserFunction Parser) { 58 assert(!CustomSectionParserFunctions.count(SectionName) && 59 "Custom parser for this section already exists"); 60 CustomSectionParserFunctions[SectionName] = std::move(Parser); 61 } 62 63 Linkage MachOLinkGraphBuilder::getLinkage(uint16_t Desc) { 64 if ((Desc & MachO::N_WEAK_DEF) || (Desc & MachO::N_WEAK_REF)) 65 return Linkage::Weak; 66 return Linkage::Strong; 67 } 68 69 Scope MachOLinkGraphBuilder::getScope(StringRef Name, uint8_t Type) { 70 if (Type & MachO::N_EXT) { 71 if ((Type & MachO::N_PEXT) || Name.startswith("l")) 72 return Scope::Hidden; 73 else 74 return Scope::Default; 75 } 76 return Scope::Local; 77 } 78 79 bool MachOLinkGraphBuilder::isAltEntry(const NormalizedSymbol &NSym) { 80 return NSym.Desc & MachO::N_ALT_ENTRY; 81 } 82 83 bool MachOLinkGraphBuilder::isDebugSection(const NormalizedSection &NSec) { 84 return (NSec.Flags & MachO::S_ATTR_DEBUG && 85 strcmp(NSec.SegName, "__DWARF") == 0); 86 } 87 88 bool MachOLinkGraphBuilder::isZeroFillSection(const NormalizedSection &NSec) { 89 switch (NSec.Flags & MachO::SECTION_TYPE) { 90 case MachO::S_ZEROFILL: 91 case MachO::S_GB_ZEROFILL: 92 case MachO::S_THREAD_LOCAL_ZEROFILL: 93 return true; 94 default: 95 return false; 96 } 97 } 98 99 unsigned 100 MachOLinkGraphBuilder::getPointerSize(const object::MachOObjectFile &Obj) { 101 return Obj.is64Bit() ? 8 : 4; 102 } 103 104 support::endianness 105 MachOLinkGraphBuilder::getEndianness(const object::MachOObjectFile &Obj) { 106 return Obj.isLittleEndian() ? support::little : support::big; 107 } 108 109 Section &MachOLinkGraphBuilder::getCommonSection() { 110 if (!CommonSection) 111 CommonSection = 112 &G->createSection(CommonSectionName, MemProt::Read | MemProt::Write); 113 return *CommonSection; 114 } 115 116 Error MachOLinkGraphBuilder::createNormalizedSections() { 117 // Build normalized sections. Verifies that section data is in-range (for 118 // sections with content) and that address ranges are non-overlapping. 119 120 LLVM_DEBUG(dbgs() << "Creating normalized sections...\n"); 121 122 for (auto &SecRef : Obj.sections()) { 123 NormalizedSection NSec; 124 uint32_t DataOffset = 0; 125 126 auto SecIndex = Obj.getSectionIndex(SecRef.getRawDataRefImpl()); 127 128 if (Obj.is64Bit()) { 129 const MachO::section_64 &Sec64 = 130 Obj.getSection64(SecRef.getRawDataRefImpl()); 131 132 memcpy(&NSec.SectName, &Sec64.sectname, 16); 133 NSec.SectName[16] = '\0'; 134 memcpy(&NSec.SegName, Sec64.segname, 16); 135 NSec.SegName[16] = '\0'; 136 137 NSec.Address = orc::ExecutorAddr(Sec64.addr); 138 NSec.Size = Sec64.size; 139 NSec.Alignment = 1ULL << Sec64.align; 140 NSec.Flags = Sec64.flags; 141 DataOffset = Sec64.offset; 142 } else { 143 const MachO::section &Sec32 = Obj.getSection(SecRef.getRawDataRefImpl()); 144 145 memcpy(&NSec.SectName, &Sec32.sectname, 16); 146 NSec.SectName[16] = '\0'; 147 memcpy(&NSec.SegName, Sec32.segname, 16); 148 NSec.SegName[16] = '\0'; 149 150 NSec.Address = orc::ExecutorAddr(Sec32.addr); 151 NSec.Size = Sec32.size; 152 NSec.Alignment = 1ULL << Sec32.align; 153 NSec.Flags = Sec32.flags; 154 DataOffset = Sec32.offset; 155 } 156 157 LLVM_DEBUG({ 158 dbgs() << " " << NSec.SegName << "," << NSec.SectName << ": " 159 << formatv("{0:x16}", NSec.Address) << " -- " 160 << formatv("{0:x16}", NSec.Address + NSec.Size) 161 << ", align: " << NSec.Alignment << ", index: " << SecIndex 162 << "\n"; 163 }); 164 165 // Get the section data if any. 166 if (!isZeroFillSection(NSec)) { 167 if (DataOffset + NSec.Size > Obj.getData().size()) 168 return make_error<JITLinkError>( 169 "Section data extends past end of file"); 170 171 NSec.Data = Obj.getData().data() + DataOffset; 172 } 173 174 // Get prot flags. 175 // FIXME: Make sure this test is correct (it's probably missing cases 176 // as-is). 177 MemProt Prot; 178 if (NSec.Flags & MachO::S_ATTR_PURE_INSTRUCTIONS) 179 Prot = MemProt::Read | MemProt::Exec; 180 else 181 Prot = MemProt::Read | MemProt::Write; 182 183 auto FullyQualifiedName = 184 G->allocateString(StringRef(NSec.SegName) + "," + NSec.SectName); 185 NSec.GraphSection = &G->createSection( 186 StringRef(FullyQualifiedName.data(), FullyQualifiedName.size()), Prot); 187 188 IndexToSection.insert(std::make_pair(SecIndex, std::move(NSec))); 189 } 190 191 std::vector<NormalizedSection *> Sections; 192 Sections.reserve(IndexToSection.size()); 193 for (auto &KV : IndexToSection) 194 Sections.push_back(&KV.second); 195 196 // If we didn't end up creating any sections then bail out. The code below 197 // assumes that we have at least one section. 198 if (Sections.empty()) 199 return Error::success(); 200 201 llvm::sort(Sections, 202 [](const NormalizedSection *LHS, const NormalizedSection *RHS) { 203 assert(LHS && RHS && "Null section?"); 204 if (LHS->Address != RHS->Address) 205 return LHS->Address < RHS->Address; 206 return LHS->Size < RHS->Size; 207 }); 208 209 for (unsigned I = 0, E = Sections.size() - 1; I != E; ++I) { 210 auto &Cur = *Sections[I]; 211 auto &Next = *Sections[I + 1]; 212 if (Next.Address < Cur.Address + Cur.Size) 213 return make_error<JITLinkError>( 214 "Address range for section " + 215 formatv("\"{0}/{1}\" [ {2:x16} -- {3:x16} ] ", Cur.SegName, 216 Cur.SectName, Cur.Address, Cur.Address + Cur.Size) + 217 "overlaps section \"" + Next.SegName + "/" + Next.SectName + "\"" + 218 formatv("\"{0}/{1}\" [ {2:x16} -- {3:x16} ] ", Next.SegName, 219 Next.SectName, Next.Address, Next.Address + Next.Size)); 220 } 221 222 return Error::success(); 223 } 224 225 Error MachOLinkGraphBuilder::createNormalizedSymbols() { 226 LLVM_DEBUG(dbgs() << "Creating normalized symbols...\n"); 227 228 for (auto &SymRef : Obj.symbols()) { 229 230 unsigned SymbolIndex = Obj.getSymbolIndex(SymRef.getRawDataRefImpl()); 231 uint64_t Value; 232 uint32_t NStrX; 233 uint8_t Type; 234 uint8_t Sect; 235 uint16_t Desc; 236 237 if (Obj.is64Bit()) { 238 const MachO::nlist_64 &NL64 = 239 Obj.getSymbol64TableEntry(SymRef.getRawDataRefImpl()); 240 Value = NL64.n_value; 241 NStrX = NL64.n_strx; 242 Type = NL64.n_type; 243 Sect = NL64.n_sect; 244 Desc = NL64.n_desc; 245 } else { 246 const MachO::nlist &NL32 = 247 Obj.getSymbolTableEntry(SymRef.getRawDataRefImpl()); 248 Value = NL32.n_value; 249 NStrX = NL32.n_strx; 250 Type = NL32.n_type; 251 Sect = NL32.n_sect; 252 Desc = NL32.n_desc; 253 } 254 255 // Skip stabs. 256 // FIXME: Are there other symbols we should be skipping? 257 if (Type & MachO::N_STAB) 258 continue; 259 260 Optional<StringRef> Name; 261 if (NStrX) { 262 if (auto NameOrErr = SymRef.getName()) 263 Name = *NameOrErr; 264 else 265 return NameOrErr.takeError(); 266 } 267 268 LLVM_DEBUG({ 269 dbgs() << " "; 270 if (!Name) 271 dbgs() << "<anonymous symbol>"; 272 else 273 dbgs() << *Name; 274 dbgs() << ": value = " << formatv("{0:x16}", Value) 275 << ", type = " << formatv("{0:x2}", Type) 276 << ", desc = " << formatv("{0:x4}", Desc) << ", sect = "; 277 if (Sect) 278 dbgs() << static_cast<unsigned>(Sect - 1); 279 else 280 dbgs() << "none"; 281 dbgs() << "\n"; 282 }); 283 284 // If this symbol has a section, verify that the addresses line up. 285 if (Sect != 0) { 286 auto NSec = findSectionByIndex(Sect - 1); 287 if (!NSec) 288 return NSec.takeError(); 289 290 if (orc::ExecutorAddr(Value) < NSec->Address || 291 orc::ExecutorAddr(Value) > NSec->Address + NSec->Size) 292 return make_error<JITLinkError>("Address " + formatv("{0:x}", Value) + 293 " for symbol " + *Name + 294 " does not fall within section"); 295 296 if (!NSec->GraphSection) { 297 LLVM_DEBUG({ 298 dbgs() << " Skipping: Symbol is in section " << NSec->SegName << "/" 299 << NSec->SectName 300 << " which has no associated graph section.\n"; 301 }); 302 continue; 303 } 304 } 305 306 IndexToSymbol[SymbolIndex] = 307 &createNormalizedSymbol(*Name, Value, Type, Sect, Desc, 308 getLinkage(Desc), getScope(*Name, Type)); 309 } 310 311 return Error::success(); 312 } 313 314 void MachOLinkGraphBuilder::addSectionStartSymAndBlock( 315 unsigned SecIndex, Section &GraphSec, orc::ExecutorAddr Address, 316 const char *Data, orc::ExecutorAddrDiff Size, uint32_t Alignment, 317 bool IsLive) { 318 Block &B = 319 Data ? G->createContentBlock(GraphSec, ArrayRef<char>(Data, Size), 320 Address, Alignment, 0) 321 : G->createZeroFillBlock(GraphSec, Size, Address, Alignment, 0); 322 auto &Sym = G->addAnonymousSymbol(B, 0, Size, false, IsLive); 323 auto SecI = IndexToSection.find(SecIndex); 324 assert(SecI != IndexToSection.end() && "SecIndex invalid"); 325 auto &NSec = SecI->second; 326 assert(!NSec.CanonicalSymbols.count(Sym.getAddress()) && 327 "Anonymous block start symbol clashes with existing symbol address"); 328 NSec.CanonicalSymbols[Sym.getAddress()] = &Sym; 329 } 330 331 Error MachOLinkGraphBuilder::graphifyRegularSymbols() { 332 333 LLVM_DEBUG(dbgs() << "Creating graph symbols...\n"); 334 335 /// We only have 256 section indexes: Use a vector rather than a map. 336 std::vector<std::vector<NormalizedSymbol *>> SecIndexToSymbols; 337 SecIndexToSymbols.resize(256); 338 339 // Create commons, externs, and absolutes, and partition all other symbols by 340 // section. 341 for (auto &KV : IndexToSymbol) { 342 auto &NSym = *KV.second; 343 344 switch (NSym.Type & MachO::N_TYPE) { 345 case MachO::N_UNDF: 346 if (NSym.Value) { 347 if (!NSym.Name) 348 return make_error<JITLinkError>("Anonymous common symbol at index " + 349 Twine(KV.first)); 350 NSym.GraphSymbol = &G->addCommonSymbol( 351 *NSym.Name, NSym.S, getCommonSection(), orc::ExecutorAddr(), 352 orc::ExecutorAddrDiff(NSym.Value), 353 1ull << MachO::GET_COMM_ALIGN(NSym.Desc), 354 NSym.Desc & MachO::N_NO_DEAD_STRIP); 355 } else { 356 if (!NSym.Name) 357 return make_error<JITLinkError>("Anonymous external symbol at " 358 "index " + 359 Twine(KV.first)); 360 NSym.GraphSymbol = &G->addExternalSymbol( 361 *NSym.Name, 0, 362 NSym.Desc & MachO::N_WEAK_REF ? Linkage::Weak : Linkage::Strong); 363 } 364 break; 365 case MachO::N_ABS: 366 if (!NSym.Name) 367 return make_error<JITLinkError>("Anonymous absolute symbol at index " + 368 Twine(KV.first)); 369 NSym.GraphSymbol = &G->addAbsoluteSymbol( 370 *NSym.Name, orc::ExecutorAddr(NSym.Value), 0, Linkage::Strong, 371 Scope::Default, NSym.Desc & MachO::N_NO_DEAD_STRIP); 372 break; 373 case MachO::N_SECT: 374 SecIndexToSymbols[NSym.Sect - 1].push_back(&NSym); 375 break; 376 case MachO::N_PBUD: 377 return make_error<JITLinkError>( 378 "Unupported N_PBUD symbol " + 379 (NSym.Name ? ("\"" + *NSym.Name + "\"") : Twine("<anon>")) + 380 " at index " + Twine(KV.first)); 381 case MachO::N_INDR: 382 return make_error<JITLinkError>( 383 "Unupported N_INDR symbol " + 384 (NSym.Name ? ("\"" + *NSym.Name + "\"") : Twine("<anon>")) + 385 " at index " + Twine(KV.first)); 386 default: 387 return make_error<JITLinkError>( 388 "Unrecognized symbol type " + Twine(NSym.Type & MachO::N_TYPE) + 389 " for symbol " + 390 (NSym.Name ? ("\"" + *NSym.Name + "\"") : Twine("<anon>")) + 391 " at index " + Twine(KV.first)); 392 } 393 } 394 395 // Loop over sections performing regular graphification for those that 396 // don't have custom parsers. 397 for (auto &KV : IndexToSection) { 398 auto SecIndex = KV.first; 399 auto &NSec = KV.second; 400 401 if (!NSec.GraphSection) { 402 LLVM_DEBUG({ 403 dbgs() << " " << NSec.SegName << "/" << NSec.SectName 404 << " has no graph section. Skipping.\n"; 405 }); 406 continue; 407 } 408 409 // Skip sections with custom parsers. 410 if (CustomSectionParserFunctions.count(NSec.GraphSection->getName())) { 411 LLVM_DEBUG({ 412 dbgs() << " Skipping section " << NSec.GraphSection->getName() 413 << " as it has a custom parser.\n"; 414 }); 415 continue; 416 } else if ((NSec.Flags & MachO::SECTION_TYPE) == 417 MachO::S_CSTRING_LITERALS) { 418 if (auto Err = graphifyCStringSection( 419 NSec, std::move(SecIndexToSymbols[SecIndex]))) 420 return Err; 421 continue; 422 } else 423 LLVM_DEBUG({ 424 dbgs() << " Graphifying regular section " 425 << NSec.GraphSection->getName() << "...\n"; 426 }); 427 428 bool SectionIsNoDeadStrip = NSec.Flags & MachO::S_ATTR_NO_DEAD_STRIP; 429 bool SectionIsText = NSec.Flags & MachO::S_ATTR_PURE_INSTRUCTIONS; 430 431 auto &SecNSymStack = SecIndexToSymbols[SecIndex]; 432 433 // If this section is non-empty but there are no symbols covering it then 434 // create one block and anonymous symbol to cover the entire section. 435 if (SecNSymStack.empty()) { 436 if (NSec.Size > 0) { 437 LLVM_DEBUG({ 438 dbgs() << " Section non-empty, but contains no symbols. " 439 "Creating anonymous block to cover " 440 << formatv("{0:x16}", NSec.Address) << " -- " 441 << formatv("{0:x16}", NSec.Address + NSec.Size) << "\n"; 442 }); 443 addSectionStartSymAndBlock(SecIndex, *NSec.GraphSection, NSec.Address, 444 NSec.Data, NSec.Size, NSec.Alignment, 445 SectionIsNoDeadStrip); 446 } else 447 LLVM_DEBUG({ 448 dbgs() << " Section empty and contains no symbols. Skipping.\n"; 449 }); 450 continue; 451 } 452 453 // Sort the symbol stack in by address, alt-entry status, scope, and name. 454 // We sort in reverse order so that symbols will be visited in the right 455 // order when we pop off the stack below. 456 llvm::sort(SecNSymStack, [](const NormalizedSymbol *LHS, 457 const NormalizedSymbol *RHS) { 458 if (LHS->Value != RHS->Value) 459 return LHS->Value > RHS->Value; 460 if (isAltEntry(*LHS) != isAltEntry(*RHS)) 461 return isAltEntry(*RHS); 462 if (LHS->S != RHS->S) 463 return static_cast<uint8_t>(LHS->S) < static_cast<uint8_t>(RHS->S); 464 return LHS->Name < RHS->Name; 465 }); 466 467 // The first symbol in a section can not be an alt-entry symbol. 468 if (!SecNSymStack.empty() && isAltEntry(*SecNSymStack.back())) 469 return make_error<JITLinkError>( 470 "First symbol in " + NSec.GraphSection->getName() + " is alt-entry"); 471 472 // If the section is non-empty but there is no symbol covering the start 473 // address then add an anonymous one. 474 if (orc::ExecutorAddr(SecNSymStack.back()->Value) != NSec.Address) { 475 auto AnonBlockSize = 476 orc::ExecutorAddr(SecNSymStack.back()->Value) - NSec.Address; 477 LLVM_DEBUG({ 478 dbgs() << " Section start not covered by symbol. " 479 << "Creating anonymous block to cover [ " << NSec.Address 480 << " -- " << (NSec.Address + AnonBlockSize) << " ]\n"; 481 }); 482 addSectionStartSymAndBlock(SecIndex, *NSec.GraphSection, NSec.Address, 483 NSec.Data, AnonBlockSize, NSec.Alignment, 484 SectionIsNoDeadStrip); 485 } 486 487 // Visit section symbols in order by popping off the reverse-sorted stack, 488 // building blocks for each alt-entry chain and creating symbols as we go. 489 while (!SecNSymStack.empty()) { 490 SmallVector<NormalizedSymbol *, 8> BlockSyms; 491 492 BlockSyms.push_back(SecNSymStack.back()); 493 SecNSymStack.pop_back(); 494 while (!SecNSymStack.empty() && 495 (isAltEntry(*SecNSymStack.back()) || 496 SecNSymStack.back()->Value == BlockSyms.back()->Value)) { 497 BlockSyms.push_back(SecNSymStack.back()); 498 SecNSymStack.pop_back(); 499 } 500 501 // BlockNSyms now contains the block symbols in reverse canonical order. 502 auto BlockStart = orc::ExecutorAddr(BlockSyms.front()->Value); 503 orc::ExecutorAddr BlockEnd = 504 SecNSymStack.empty() ? NSec.Address + NSec.Size 505 : orc::ExecutorAddr(SecNSymStack.back()->Value); 506 orc::ExecutorAddrDiff BlockOffset = BlockStart - NSec.Address; 507 orc::ExecutorAddrDiff BlockSize = BlockEnd - BlockStart; 508 509 LLVM_DEBUG({ 510 dbgs() << " Creating block for " << formatv("{0:x16}", BlockStart) 511 << " -- " << formatv("{0:x16}", BlockEnd) << ": " 512 << NSec.GraphSection->getName() << " + " 513 << formatv("{0:x16}", BlockOffset) << " with " 514 << BlockSyms.size() << " symbol(s)...\n"; 515 }); 516 517 Block &B = 518 NSec.Data 519 ? G->createContentBlock( 520 *NSec.GraphSection, 521 ArrayRef<char>(NSec.Data + BlockOffset, BlockSize), 522 BlockStart, NSec.Alignment, BlockStart % NSec.Alignment) 523 : G->createZeroFillBlock(*NSec.GraphSection, BlockSize, 524 BlockStart, NSec.Alignment, 525 BlockStart % NSec.Alignment); 526 527 Optional<orc::ExecutorAddr> LastCanonicalAddr; 528 auto SymEnd = BlockEnd; 529 while (!BlockSyms.empty()) { 530 auto &NSym = *BlockSyms.back(); 531 BlockSyms.pop_back(); 532 533 bool SymLive = 534 (NSym.Desc & MachO::N_NO_DEAD_STRIP) || SectionIsNoDeadStrip; 535 536 auto &Sym = createStandardGraphSymbol( 537 NSym, B, SymEnd - orc::ExecutorAddr(NSym.Value), SectionIsText, 538 SymLive, LastCanonicalAddr != orc::ExecutorAddr(NSym.Value)); 539 540 if (LastCanonicalAddr != Sym.getAddress()) { 541 if (LastCanonicalAddr) 542 SymEnd = *LastCanonicalAddr; 543 LastCanonicalAddr = Sym.getAddress(); 544 } 545 } 546 } 547 } 548 549 return Error::success(); 550 } 551 552 Symbol &MachOLinkGraphBuilder::createStandardGraphSymbol(NormalizedSymbol &NSym, 553 Block &B, size_t Size, 554 bool IsText, 555 bool IsNoDeadStrip, 556 bool IsCanonical) { 557 558 LLVM_DEBUG({ 559 dbgs() << " " << formatv("{0:x16}", NSym.Value) << " -- " 560 << formatv("{0:x16}", NSym.Value + Size) << ": "; 561 if (!NSym.Name) 562 dbgs() << "<anonymous symbol>"; 563 else 564 dbgs() << NSym.Name; 565 if (IsText) 566 dbgs() << " [text]"; 567 if (IsNoDeadStrip) 568 dbgs() << " [no-dead-strip]"; 569 if (!IsCanonical) 570 dbgs() << " [non-canonical]"; 571 dbgs() << "\n"; 572 }); 573 574 auto SymOffset = orc::ExecutorAddr(NSym.Value) - B.getAddress(); 575 auto &Sym = 576 NSym.Name 577 ? G->addDefinedSymbol(B, SymOffset, *NSym.Name, Size, NSym.L, NSym.S, 578 IsText, IsNoDeadStrip) 579 : G->addAnonymousSymbol(B, SymOffset, Size, IsText, IsNoDeadStrip); 580 NSym.GraphSymbol = &Sym; 581 582 if (IsCanonical) 583 setCanonicalSymbol(getSectionByIndex(NSym.Sect - 1), Sym); 584 585 return Sym; 586 } 587 588 Error MachOLinkGraphBuilder::graphifySectionsWithCustomParsers() { 589 // Graphify special sections. 590 for (auto &KV : IndexToSection) { 591 auto &NSec = KV.second; 592 593 // Skip non-graph sections. 594 if (!NSec.GraphSection) 595 continue; 596 597 auto HI = CustomSectionParserFunctions.find(NSec.GraphSection->getName()); 598 if (HI != CustomSectionParserFunctions.end()) { 599 auto &Parse = HI->second; 600 if (auto Err = Parse(NSec)) 601 return Err; 602 } 603 } 604 605 return Error::success(); 606 } 607 608 Error MachOLinkGraphBuilder::graphifyCStringSection( 609 NormalizedSection &NSec, std::vector<NormalizedSymbol *> NSyms) { 610 assert(NSec.GraphSection && "C string literal section missing graph section"); 611 assert(NSec.Data && "C string literal section has no data"); 612 613 LLVM_DEBUG({ 614 dbgs() << " Graphifying C-string literal section " 615 << NSec.GraphSection->getName() << "\n"; 616 }); 617 618 if (NSec.Data[NSec.Size - 1] != '\0') 619 return make_error<JITLinkError>("C string literal section " + 620 NSec.GraphSection->getName() + 621 " does not end with null terminator"); 622 623 /// Sort into reverse order to use as a stack. 624 llvm::sort(NSyms, 625 [](const NormalizedSymbol *LHS, const NormalizedSymbol *RHS) { 626 if (LHS->Value != RHS->Value) 627 return LHS->Value > RHS->Value; 628 if (LHS->L != RHS->L) 629 return LHS->L > RHS->L; 630 if (LHS->S != RHS->S) 631 return LHS->S > RHS->S; 632 if (RHS->Name) { 633 if (!LHS->Name) 634 return true; 635 return *LHS->Name > *RHS->Name; 636 } 637 return false; 638 }); 639 640 bool SectionIsNoDeadStrip = NSec.Flags & MachO::S_ATTR_NO_DEAD_STRIP; 641 bool SectionIsText = NSec.Flags & MachO::S_ATTR_PURE_INSTRUCTIONS; 642 orc::ExecutorAddrDiff BlockStart = 0; 643 644 // Scan section for null characters. 645 for (size_t I = 0; I != NSec.Size; ++I) 646 if (NSec.Data[I] == '\0') { 647 orc::ExecutorAddrDiff BlockEnd = I + 1; 648 size_t BlockSize = BlockEnd - BlockStart; 649 // Create a block for this null terminated string. 650 auto &B = G->createContentBlock(*NSec.GraphSection, 651 {NSec.Data + BlockStart, BlockSize}, 652 NSec.Address + BlockStart, 1, 0); 653 654 LLVM_DEBUG({ 655 dbgs() << " Created block " << formatv("{0:x}", B.getAddress()) 656 << " -- " << formatv("{0:x}", B.getAddress() + B.getSize()) 657 << " for \"" << StringRef(B.getContent().data()) << "\"\n"; 658 }); 659 660 // If there's no symbol at the start of this block then create one. 661 if (NSyms.empty() || 662 orc::ExecutorAddr(NSyms.back()->Value) != B.getAddress()) { 663 auto &S = G->addAnonymousSymbol(B, 0, BlockSize, false, false); 664 setCanonicalSymbol(NSec, S); 665 LLVM_DEBUG({ 666 dbgs() << " Adding anonymous symbol for c-string block " 667 << formatv("{0:x16} -- {1:x16}", S.getAddress(), 668 S.getAddress() + BlockSize) 669 << "\n"; 670 }); 671 } 672 673 // Process any remaining symbols that point into this block. 674 auto LastCanonicalAddr = B.getAddress() + BlockEnd; 675 while (!NSyms.empty() && orc::ExecutorAddr(NSyms.back()->Value) < 676 B.getAddress() + BlockSize) { 677 auto &NSym = *NSyms.back(); 678 size_t SymSize = (B.getAddress() + BlockSize) - 679 orc::ExecutorAddr(NSyms.back()->Value); 680 bool SymLive = 681 (NSym.Desc & MachO::N_NO_DEAD_STRIP) || SectionIsNoDeadStrip; 682 683 bool IsCanonical = false; 684 if (LastCanonicalAddr != orc::ExecutorAddr(NSym.Value)) { 685 IsCanonical = true; 686 LastCanonicalAddr = orc::ExecutorAddr(NSym.Value); 687 } 688 689 createStandardGraphSymbol(NSym, B, SymSize, SectionIsText, SymLive, 690 IsCanonical); 691 692 NSyms.pop_back(); 693 } 694 695 BlockStart += BlockSize; 696 } 697 698 return Error::success(); 699 } 700 701 Error CompactUnwindSplitter::operator()(LinkGraph &G) { 702 auto *CUSec = G.findSectionByName(CompactUnwindSectionName); 703 if (!CUSec) 704 return Error::success(); 705 706 if (!G.getTargetTriple().isOSBinFormatMachO()) 707 return make_error<JITLinkError>( 708 "Error linking " + G.getName() + 709 ": compact unwind splitting not supported on non-macho target " + 710 G.getTargetTriple().str()); 711 712 unsigned CURecordSize = 0; 713 unsigned PersonalityEdgeOffset = 0; 714 unsigned LSDAEdgeOffset = 0; 715 switch (G.getTargetTriple().getArch()) { 716 case Triple::aarch64: 717 case Triple::x86_64: 718 // 64-bit compact-unwind record format: 719 // Range start: 8 bytes. 720 // Range size: 4 bytes. 721 // CU encoding: 4 bytes. 722 // Personality: 8 bytes. 723 // LSDA: 8 bytes. 724 CURecordSize = 32; 725 PersonalityEdgeOffset = 16; 726 LSDAEdgeOffset = 24; 727 break; 728 default: 729 return make_error<JITLinkError>( 730 "Error linking " + G.getName() + 731 ": compact unwind splitting not supported on " + 732 G.getTargetTriple().getArchName()); 733 } 734 735 std::vector<Block *> OriginalBlocks(CUSec->blocks().begin(), 736 CUSec->blocks().end()); 737 LLVM_DEBUG({ 738 dbgs() << "In " << G.getName() << " splitting compact unwind section " 739 << CompactUnwindSectionName << " containing " 740 << OriginalBlocks.size() << " initial blocks...\n"; 741 }); 742 743 while (!OriginalBlocks.empty()) { 744 auto *B = OriginalBlocks.back(); 745 OriginalBlocks.pop_back(); 746 747 if (B->getSize() == 0) { 748 LLVM_DEBUG({ 749 dbgs() << " Skipping empty block at " 750 << formatv("{0:x16}", B->getAddress()) << "\n"; 751 }); 752 continue; 753 } 754 755 LLVM_DEBUG({ 756 dbgs() << " Splitting block at " << formatv("{0:x16}", B->getAddress()) 757 << " into " << (B->getSize() / CURecordSize) 758 << " compact unwind record(s)\n"; 759 }); 760 761 if (B->getSize() % CURecordSize) 762 return make_error<JITLinkError>( 763 "Error splitting compact unwind record in " + G.getName() + 764 ": block at " + formatv("{0:x}", B->getAddress()) + " has size " + 765 formatv("{0:x}", B->getSize()) + 766 " (not a multiple of CU record size of " + 767 formatv("{0:x}", CURecordSize) + ")"); 768 769 unsigned NumBlocks = B->getSize() / CURecordSize; 770 LinkGraph::SplitBlockCache C; 771 772 for (unsigned I = 0; I != NumBlocks; ++I) { 773 auto &CURec = G.splitBlock(*B, CURecordSize, &C); 774 bool AddedKeepAlive = false; 775 776 for (auto &E : CURec.edges()) { 777 if (E.getOffset() == 0) { 778 LLVM_DEBUG({ 779 dbgs() << " Updating compact unwind record at " 780 << formatv("{0:x16}", CURec.getAddress()) << " to point to " 781 << (E.getTarget().hasName() ? E.getTarget().getName() 782 : StringRef()) 783 << " (at " << formatv("{0:x16}", E.getTarget().getAddress()) 784 << ")\n"; 785 }); 786 787 if (E.getTarget().isExternal()) 788 return make_error<JITLinkError>( 789 "Error adding keep-alive edge for compact unwind record at " + 790 formatv("{0:x}", CURec.getAddress()) + ": target " + 791 E.getTarget().getName() + " is an external symbol"); 792 auto &TgtBlock = E.getTarget().getBlock(); 793 auto &CURecSym = 794 G.addAnonymousSymbol(CURec, 0, CURecordSize, false, false); 795 TgtBlock.addEdge(Edge::KeepAlive, 0, CURecSym, 0); 796 AddedKeepAlive = true; 797 } else if (E.getOffset() != PersonalityEdgeOffset && 798 E.getOffset() != LSDAEdgeOffset) 799 return make_error<JITLinkError>("Unexpected edge at offset " + 800 formatv("{0:x}", E.getOffset()) + 801 " in compact unwind record at " + 802 formatv("{0:x}", CURec.getAddress())); 803 } 804 805 if (!AddedKeepAlive) 806 return make_error<JITLinkError>( 807 "Error adding keep-alive edge for compact unwind record at " + 808 formatv("{0:x}", CURec.getAddress()) + 809 ": no outgoing target edge at offset 0"); 810 } 811 } 812 return Error::success(); 813 } 814 815 } // end namespace jitlink 816 } // end namespace llvm 817