| //=--------- MachOLinkGraphBuilder.cpp - MachO LinkGraph builder ----------===// | |
| // | |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. | |
| // See https://llvm.org/LICENSE.txt for license information. | |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception | |
| // | |
| //===----------------------------------------------------------------------===// | |
| // | |
| // Generic MachO LinkGraph buliding code. | |
| // | |
| //===----------------------------------------------------------------------===// | |
| #include "MachOLinkGraphBuilder.h" | |
| #define DEBUG_TYPE "jitlink" | |
| static const char *CommonSectionName = "__common"; | |
| namespace llvm { | |
| namespace jitlink { | |
| MachOLinkGraphBuilder::~MachOLinkGraphBuilder() {} | |
| Expected<std::unique_ptr<LinkGraph>> MachOLinkGraphBuilder::buildGraph() { | |
| // Sanity check: we only operate on relocatable objects. | |
| if (!Obj.isRelocatableObject()) | |
| return make_error<JITLinkError>("Object is not a relocatable MachO"); | |
| if (auto Err = createNormalizedSections()) | |
| return std::move(Err); | |
| if (auto Err = createNormalizedSymbols()) | |
| return std::move(Err); | |
| if (auto Err = graphifyRegularSymbols()) | |
| return std::move(Err); | |
| if (auto Err = graphifySectionsWithCustomParsers()) | |
| return std::move(Err); | |
| if (auto Err = addRelocations()) | |
| return std::move(Err); | |
| return std::move(G); | |
| } | |
| MachOLinkGraphBuilder::MachOLinkGraphBuilder(const object::MachOObjectFile &Obj) | |
| : Obj(Obj), | |
| G(std::make_unique<LinkGraph>(Obj.getFileName(), getPointerSize(Obj), | |
| getEndianness(Obj))) {} | |
| void MachOLinkGraphBuilder::addCustomSectionParser( | |
| StringRef SectionName, SectionParserFunction Parser) { | |
| assert(!CustomSectionParserFunctions.count(SectionName) && | |
| "Custom parser for this section already exists"); | |
| CustomSectionParserFunctions[SectionName] = std::move(Parser); | |
| } | |
| Linkage MachOLinkGraphBuilder::getLinkage(uint16_t Desc) { | |
| if ((Desc & MachO::N_WEAK_DEF) || (Desc & MachO::N_WEAK_REF)) | |
| return Linkage::Weak; | |
| return Linkage::Strong; | |
| } | |
| Scope MachOLinkGraphBuilder::getScope(StringRef Name, uint8_t Type) { | |
| if (Name.startswith("l")) | |
| return Scope::Local; | |
| if (Type & MachO::N_PEXT) | |
| return Scope::Hidden; | |
| if (Type & MachO::N_EXT) | |
| return Scope::Default; | |
| return Scope::Local; | |
| } | |
| bool MachOLinkGraphBuilder::isAltEntry(const NormalizedSymbol &NSym) { | |
| return NSym.Desc & MachO::N_ALT_ENTRY; | |
| } | |
| unsigned | |
| MachOLinkGraphBuilder::getPointerSize(const object::MachOObjectFile &Obj) { | |
| return Obj.is64Bit() ? 8 : 4; | |
| } | |
| support::endianness | |
| MachOLinkGraphBuilder::getEndianness(const object::MachOObjectFile &Obj) { | |
| return Obj.isLittleEndian() ? support::little : support::big; | |
| } | |
| Section &MachOLinkGraphBuilder::getCommonSection() { | |
| if (!CommonSection) { | |
| auto Prot = static_cast<sys::Memory::ProtectionFlags>( | |
| sys::Memory::MF_READ | sys::Memory::MF_WRITE); | |
| CommonSection = &G->createSection(CommonSectionName, Prot); | |
| } | |
| return *CommonSection; | |
| } | |
| Error MachOLinkGraphBuilder::createNormalizedSections() { | |
| // Build normalized sections. Verifies that section data is in-range (for | |
| // sections with content) and that address ranges are non-overlapping. | |
| LLVM_DEBUG(dbgs() << "Creating normalized sections...\n"); | |
| for (auto &SecRef : Obj.sections()) { | |
| NormalizedSection NSec; | |
| uint32_t DataOffset = 0; | |
| auto SecIndex = Obj.getSectionIndex(SecRef.getRawDataRefImpl()); | |
| auto Name = SecRef.getName(); | |
| if (!Name) | |
| return Name.takeError(); | |
| if (Obj.is64Bit()) { | |
| const MachO::section_64 &Sec64 = | |
| Obj.getSection64(SecRef.getRawDataRefImpl()); | |
| NSec.Address = Sec64.addr; | |
| NSec.Size = Sec64.size; | |
| NSec.Alignment = 1ULL << Sec64.align; | |
| NSec.Flags = Sec64.flags; | |
| DataOffset = Sec64.offset; | |
| } else { | |
| const MachO::section &Sec32 = Obj.getSection(SecRef.getRawDataRefImpl()); | |
| NSec.Address = Sec32.addr; | |
| NSec.Size = Sec32.size; | |
| NSec.Alignment = 1ULL << Sec32.align; | |
| NSec.Flags = Sec32.flags; | |
| DataOffset = Sec32.offset; | |
| } | |
| LLVM_DEBUG({ | |
| dbgs() << " " << *Name << ": " << formatv("{0:x16}", NSec.Address) | |
| << " -- " << formatv("{0:x16}", NSec.Address + NSec.Size) | |
| << ", align: " << NSec.Alignment << ", index: " << SecIndex | |
| << "\n"; | |
| }); | |
| // Get the section data if any. | |
| { | |
| unsigned SectionType = NSec.Flags & MachO::SECTION_TYPE; | |
| if (SectionType != MachO::S_ZEROFILL && | |
| SectionType != MachO::S_GB_ZEROFILL) { | |
| if (DataOffset + NSec.Size > Obj.getData().size()) | |
| return make_error<JITLinkError>( | |
| "Section data extends past end of file"); | |
| NSec.Data = Obj.getData().data() + DataOffset; | |
| } | |
| } | |
| // Get prot flags. | |
| // FIXME: Make sure this test is correct (it's probably missing cases | |
| // as-is). | |
| sys::Memory::ProtectionFlags Prot; | |
| if (NSec.Flags & MachO::S_ATTR_PURE_INSTRUCTIONS) | |
| Prot = static_cast<sys::Memory::ProtectionFlags>(sys::Memory::MF_READ | | |
| sys::Memory::MF_EXEC); | |
| else | |
| Prot = static_cast<sys::Memory::ProtectionFlags>(sys::Memory::MF_READ | | |
| sys::Memory::MF_WRITE); | |
| NSec.GraphSection = &G->createSection(*Name, Prot); | |
| IndexToSection.insert(std::make_pair(SecIndex, std::move(NSec))); | |
| } | |
| std::vector<NormalizedSection *> Sections; | |
| Sections.reserve(IndexToSection.size()); | |
| for (auto &KV : IndexToSection) | |
| Sections.push_back(&KV.second); | |
| // If we didn't end up creating any sections then bail out. The code below | |
| // assumes that we have at least one section. | |
| if (Sections.empty()) | |
| return Error::success(); | |
| llvm::sort(Sections, | |
| [](const NormalizedSection *LHS, const NormalizedSection *RHS) { | |
| assert(LHS && RHS && "Null section?"); | |
| if (LHS->Address != RHS->Address) | |
| return LHS->Address < RHS->Address; | |
| return LHS->Size < RHS->Size; | |
| }); | |
| for (unsigned I = 0, E = Sections.size() - 1; I != E; ++I) { | |
| auto &Cur = *Sections[I]; | |
| auto &Next = *Sections[I + 1]; | |
| if (Next.Address < Cur.Address + Cur.Size) | |
| return make_error<JITLinkError>( | |
| "Address range for section " + Cur.GraphSection->getName() + | |
| formatv(" [ {0:x16} -- {1:x16} ] ", Cur.Address, | |
| Cur.Address + Cur.Size) + | |
| "overlaps " + | |
| formatv(" [ {0:x16} -- {1:x16} ] ", Next.Address, | |
| Next.Address + Next.Size)); | |
| } | |
| return Error::success(); | |
| } | |
| Error MachOLinkGraphBuilder::createNormalizedSymbols() { | |
| LLVM_DEBUG(dbgs() << "Creating normalized symbols...\n"); | |
| for (auto &SymRef : Obj.symbols()) { | |
| unsigned SymbolIndex = Obj.getSymbolIndex(SymRef.getRawDataRefImpl()); | |
| uint64_t Value; | |
| uint32_t NStrX; | |
| uint8_t Type; | |
| uint8_t Sect; | |
| uint16_t Desc; | |
| if (Obj.is64Bit()) { | |
| const MachO::nlist_64 &NL64 = | |
| Obj.getSymbol64TableEntry(SymRef.getRawDataRefImpl()); | |
| Value = NL64.n_value; | |
| NStrX = NL64.n_strx; | |
| Type = NL64.n_type; | |
| Sect = NL64.n_sect; | |
| Desc = NL64.n_desc; | |
| } else { | |
| const MachO::nlist &NL32 = | |
| Obj.getSymbolTableEntry(SymRef.getRawDataRefImpl()); | |
| Value = NL32.n_value; | |
| NStrX = NL32.n_strx; | |
| Type = NL32.n_type; | |
| Sect = NL32.n_sect; | |
| Desc = NL32.n_desc; | |
| } | |
| // Skip stabs. | |
| // FIXME: Are there other symbols we should be skipping? | |
| if (Type & MachO::N_STAB) | |
| continue; | |
| Optional<StringRef> Name; | |
| if (NStrX) { | |
| if (auto NameOrErr = SymRef.getName()) | |
| Name = *NameOrErr; | |
| else | |
| return NameOrErr.takeError(); | |
| } | |
| LLVM_DEBUG({ | |
| dbgs() << " "; | |
| if (!Name) | |
| dbgs() << "<anonymous symbol>"; | |
| else | |
| dbgs() << *Name; | |
| dbgs() << ": value = " << formatv("{0:x16}", Value) | |
| << ", type = " << formatv("{0:x2}", Type) | |
| << ", desc = " << formatv("{0:x4}", Desc) << ", sect = "; | |
| if (Sect) | |
| dbgs() << static_cast<unsigned>(Sect - 1); | |
| else | |
| dbgs() << "none"; | |
| dbgs() << "\n"; | |
| }); | |
| // If this symbol has a section, sanity check that the addresses line up. | |
| NormalizedSection *NSec = nullptr; | |
| if (Sect != 0) { | |
| if (auto NSecOrErr = findSectionByIndex(Sect - 1)) | |
| NSec = &*NSecOrErr; | |
| else | |
| return NSecOrErr.takeError(); | |
| if (Value < NSec->Address || Value > NSec->Address + NSec->Size) | |
| return make_error<JITLinkError>("Symbol address does not fall within " | |
| "section"); | |
| } | |
| IndexToSymbol[SymbolIndex] = | |
| &createNormalizedSymbol(*Name, Value, Type, Sect, Desc, | |
| getLinkage(Type), getScope(*Name, Type)); | |
| } | |
| return Error::success(); | |
| } | |
| void MachOLinkGraphBuilder::addSectionStartSymAndBlock( | |
| Section &GraphSec, uint64_t Address, const char *Data, uint64_t Size, | |
| uint32_t Alignment, bool IsLive) { | |
| Block &B = | |
| Data ? G->createContentBlock(GraphSec, StringRef(Data, Size), Address, | |
| Alignment, 0) | |
| : G->createZeroFillBlock(GraphSec, Size, Address, Alignment, 0); | |
| auto &Sym = G->addAnonymousSymbol(B, 0, Size, false, IsLive); | |
| assert(!AddrToCanonicalSymbol.count(Sym.getAddress()) && | |
| "Anonymous block start symbol clashes with existing symbol address"); | |
| AddrToCanonicalSymbol[Sym.getAddress()] = &Sym; | |
| } | |
| Error MachOLinkGraphBuilder::graphifyRegularSymbols() { | |
| LLVM_DEBUG(dbgs() << "Creating graph symbols...\n"); | |
| /// We only have 256 section indexes: Use a vector rather than a map. | |
| std::vector<std::vector<NormalizedSymbol *>> SecIndexToSymbols; | |
| SecIndexToSymbols.resize(256); | |
| // Create commons, externs, and absolutes, and partition all other symbols by | |
| // section. | |
| for (auto &KV : IndexToSymbol) { | |
| auto &NSym = *KV.second; | |
| switch (NSym.Type & MachO::N_TYPE) { | |
| case MachO::N_UNDF: | |
| if (NSym.Value) { | |
| if (!NSym.Name) | |
| return make_error<JITLinkError>("Anonymous common symbol at index " + | |
| Twine(KV.first)); | |
| NSym.GraphSymbol = &G->addCommonSymbol( | |
| *NSym.Name, NSym.S, getCommonSection(), 0, NSym.Value, | |
| 1ull << MachO::GET_COMM_ALIGN(NSym.Desc), | |
| NSym.Desc & MachO::N_NO_DEAD_STRIP); | |
| } else { | |
| if (!NSym.Name) | |
| return make_error<JITLinkError>("Anonymous external symbol at " | |
| "index " + | |
| Twine(KV.first)); | |
| NSym.GraphSymbol = &G->addExternalSymbol( | |
| *NSym.Name, 0, | |
| NSym.Desc & MachO::N_WEAK_REF ? Linkage::Weak : Linkage::Strong); | |
| } | |
| break; | |
| case MachO::N_ABS: | |
| if (!NSym.Name) | |
| return make_error<JITLinkError>("Anonymous absolute symbol at index " + | |
| Twine(KV.first)); | |
| NSym.GraphSymbol = &G->addAbsoluteSymbol( | |
| *NSym.Name, NSym.Value, 0, Linkage::Strong, Scope::Default, | |
| NSym.Desc & MachO::N_NO_DEAD_STRIP); | |
| break; | |
| case MachO::N_SECT: | |
| SecIndexToSymbols[NSym.Sect - 1].push_back(&NSym); | |
| break; | |
| case MachO::N_PBUD: | |
| return make_error<JITLinkError>( | |
| "Unupported N_PBUD symbol " + | |
| (NSym.Name ? ("\"" + *NSym.Name + "\"") : Twine("<anon>")) + | |
| " at index " + Twine(KV.first)); | |
| case MachO::N_INDR: | |
| return make_error<JITLinkError>( | |
| "Unupported N_INDR symbol " + | |
| (NSym.Name ? ("\"" + *NSym.Name + "\"") : Twine("<anon>")) + | |
| " at index " + Twine(KV.first)); | |
| default: | |
| return make_error<JITLinkError>( | |
| "Unrecognized symbol type " + Twine(NSym.Type & MachO::N_TYPE) + | |
| " for symbol " + | |
| (NSym.Name ? ("\"" + *NSym.Name + "\"") : Twine("<anon>")) + | |
| " at index " + Twine(KV.first)); | |
| } | |
| } | |
| // Loop over sections performing regular graphification for those that | |
| // don't have custom parsers. | |
| for (auto &KV : IndexToSection) { | |
| auto SecIndex = KV.first; | |
| auto &NSec = KV.second; | |
| // Skip sections with custom parsers. | |
| if (CustomSectionParserFunctions.count(NSec.GraphSection->getName())) { | |
| LLVM_DEBUG({ | |
| dbgs() << " Skipping section " << NSec.GraphSection->getName() | |
| << " as it has a custom parser.\n"; | |
| }); | |
| continue; | |
| } else | |
| LLVM_DEBUG({ | |
| dbgs() << " Processing section " << NSec.GraphSection->getName() | |
| << "...\n"; | |
| }); | |
| bool SectionIsNoDeadStrip = NSec.Flags & MachO::S_ATTR_NO_DEAD_STRIP; | |
| bool SectionIsText = NSec.Flags & MachO::S_ATTR_PURE_INSTRUCTIONS; | |
| auto &SecNSymStack = SecIndexToSymbols[SecIndex]; | |
| // If this section is non-empty but there are no symbols covering it then | |
| // create one block and anonymous symbol to cover the entire section. | |
| if (SecNSymStack.empty()) { | |
| if (NSec.Size > 0) { | |
| LLVM_DEBUG({ | |
| dbgs() << " Section non-empty, but contains no symbols. " | |
| "Creating anonymous block to cover " | |
| << formatv("{0:x16}", NSec.Address) << " -- " | |
| << formatv("{0:x16}", NSec.Address + NSec.Size) << "\n"; | |
| }); | |
| addSectionStartSymAndBlock(*NSec.GraphSection, NSec.Address, NSec.Data, | |
| NSec.Size, NSec.Alignment, | |
| SectionIsNoDeadStrip); | |
| } else | |
| LLVM_DEBUG({ | |
| dbgs() << " Section empty and contains no symbols. Skipping.\n"; | |
| }); | |
| continue; | |
| } | |
| // Sort the symbol stack in by address, alt-entry status, scope, and name. | |
| // We sort in reverse order so that symbols will be visited in the right | |
| // order when we pop off the stack below. | |
| llvm::sort(SecNSymStack, [](const NormalizedSymbol *LHS, | |
| const NormalizedSymbol *RHS) { | |
| if (LHS->Value != RHS->Value) | |
| return LHS->Value > RHS->Value; | |
| if (isAltEntry(*LHS) != isAltEntry(*RHS)) | |
| return isAltEntry(*RHS); | |
| if (LHS->S != RHS->S) | |
| return static_cast<uint8_t>(LHS->S) < static_cast<uint8_t>(RHS->S); | |
| return LHS->Name < RHS->Name; | |
| }); | |
| // The first symbol in a section can not be an alt-entry symbol. | |
| if (!SecNSymStack.empty() && isAltEntry(*SecNSymStack.back())) | |
| return make_error<JITLinkError>( | |
| "First symbol in " + NSec.GraphSection->getName() + " is alt-entry"); | |
| // If the section is non-empty but there is no symbol covering the start | |
| // address then add an anonymous one. | |
| if (SecNSymStack.back()->Value != NSec.Address) { | |
| auto AnonBlockSize = SecNSymStack.back()->Value - NSec.Address; | |
| LLVM_DEBUG({ | |
| dbgs() << " Section start not covered by symbol. " | |
| << "Creating anonymous block to cover [ " | |
| << formatv("{0:x16}", NSec.Address) << " -- " | |
| << formatv("{0:x16}", NSec.Address + AnonBlockSize) << " ]\n"; | |
| }); | |
| addSectionStartSymAndBlock(*NSec.GraphSection, NSec.Address, NSec.Data, | |
| AnonBlockSize, NSec.Alignment, | |
| SectionIsNoDeadStrip); | |
| } | |
| // Visit section symbols in order by popping off the reverse-sorted stack, | |
| // building blocks for each alt-entry chain and creating symbols as we go. | |
| while (!SecNSymStack.empty()) { | |
| SmallVector<NormalizedSymbol *, 8> BlockSyms; | |
| BlockSyms.push_back(SecNSymStack.back()); | |
| SecNSymStack.pop_back(); | |
| while (!SecNSymStack.empty() && | |
| (isAltEntry(*SecNSymStack.back()) || | |
| SecNSymStack.back()->Value == BlockSyms.back()->Value)) { | |
| BlockSyms.push_back(SecNSymStack.back()); | |
| SecNSymStack.pop_back(); | |
| } | |
| // BlockNSyms now contains the block symbols in reverse canonical order. | |
| JITTargetAddress BlockStart = BlockSyms.front()->Value; | |
| JITTargetAddress BlockEnd = SecNSymStack.empty() | |
| ? NSec.Address + NSec.Size | |
| : SecNSymStack.back()->Value; | |
| JITTargetAddress BlockOffset = BlockStart - NSec.Address; | |
| JITTargetAddress BlockSize = BlockEnd - BlockStart; | |
| LLVM_DEBUG({ | |
| dbgs() << " Creating block for " << formatv("{0:x16}", BlockStart) | |
| << " -- " << formatv("{0:x16}", BlockEnd) << ": " | |
| << NSec.GraphSection->getName() << " + " | |
| << formatv("{0:x16}", BlockOffset) << " with " | |
| << BlockSyms.size() << " symbol(s)...\n"; | |
| }); | |
| Block &B = | |
| NSec.Data | |
| ? G->createContentBlock( | |
| *NSec.GraphSection, | |
| StringRef(NSec.Data + BlockOffset, BlockSize), BlockStart, | |
| NSec.Alignment, BlockStart % NSec.Alignment) | |
| : G->createZeroFillBlock(*NSec.GraphSection, BlockSize, | |
| BlockStart, NSec.Alignment, | |
| BlockStart % NSec.Alignment); | |
| Optional<JITTargetAddress> LastCanonicalAddr; | |
| JITTargetAddress SymEnd = BlockEnd; | |
| while (!BlockSyms.empty()) { | |
| auto &NSym = *BlockSyms.back(); | |
| BlockSyms.pop_back(); | |
| bool SymLive = | |
| (NSym.Desc & MachO::N_NO_DEAD_STRIP) || SectionIsNoDeadStrip; | |
| LLVM_DEBUG({ | |
| dbgs() << " " << formatv("{0:x16}", NSym.Value) << " -- " | |
| << formatv("{0:x16}", SymEnd) << ": "; | |
| if (!NSym.Name) | |
| dbgs() << "<anonymous symbol>"; | |
| else | |
| dbgs() << NSym.Name; | |
| if (SymLive) | |
| dbgs() << " [no-dead-strip]"; | |
| if (LastCanonicalAddr == NSym.Value) | |
| dbgs() << " [non-canonical]"; | |
| dbgs() << "\n"; | |
| }); | |
| auto &Sym = | |
| NSym.Name | |
| ? G->addDefinedSymbol(B, NSym.Value - BlockStart, *NSym.Name, | |
| SymEnd - NSym.Value, NSym.L, NSym.S, | |
| SectionIsText, SymLive) | |
| : G->addAnonymousSymbol(B, NSym.Value - BlockStart, | |
| SymEnd - NSym.Value, SectionIsText, | |
| SymLive); | |
| NSym.GraphSymbol = &Sym; | |
| if (LastCanonicalAddr != Sym.getAddress()) { | |
| if (LastCanonicalAddr) | |
| SymEnd = *LastCanonicalAddr; | |
| LastCanonicalAddr = Sym.getAddress(); | |
| setCanonicalSymbol(Sym); | |
| } | |
| } | |
| } | |
| } | |
| return Error::success(); | |
| } | |
| Error MachOLinkGraphBuilder::graphifySectionsWithCustomParsers() { | |
| // Graphify special sections. | |
| for (auto &KV : IndexToSection) { | |
| auto &NSec = KV.second; | |
| auto HI = CustomSectionParserFunctions.find(NSec.GraphSection->getName()); | |
| if (HI != CustomSectionParserFunctions.end()) { | |
| auto &Parse = HI->second; | |
| if (auto Err = Parse(NSec)) | |
| return Err; | |
| } | |
| } | |
| return Error::success(); | |
| } | |
| } // end namespace jitlink | |
| } // end namespace llvm |