| //=--------- 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, Triple TT, |
| LinkGraph::GetEdgeKindNameFunction GetEdgeKindName) |
| : Obj(Obj), |
| G(std::make_unique<LinkGraph>( |
| std::string(Obj.getFileName()), std::move(TT), getPointerSize(Obj), |
| getEndianness(Obj), std::move(GetEdgeKindName))) {} |
| |
| 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 (Type & MachO::N_EXT) { |
| if ((Type & MachO::N_PEXT) || Name.startswith("l")) |
| return Scope::Hidden; |
| else |
| return Scope::Default; |
| } |
| return Scope::Local; |
| } |
| |
| bool MachOLinkGraphBuilder::isAltEntry(const NormalizedSymbol &NSym) { |
| return NSym.Desc & MachO::N_ALT_ENTRY; |
| } |
| |
| bool MachOLinkGraphBuilder::isDebugSection(const NormalizedSection &NSec) { |
| return (NSec.Flags & MachO::S_ATTR_DEBUG && |
| strcmp(NSec.SegName, "__DWARF") == 0); |
| } |
| |
| 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()); |
| |
| memcpy(&NSec.SectName, &Sec64.sectname, 16); |
| NSec.SectName[16] = '\0'; |
| memcpy(&NSec.SegName, Sec64.segname, 16); |
| NSec.SegName[16] = '\0'; |
| |
| 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()); |
| |
| memcpy(&NSec.SectName, &Sec32.sectname, 16); |
| NSec.SectName[16] = '\0'; |
| memcpy(&NSec.SegName, Sec32.segname, 16); |
| NSec.SegName[16] = '\0'; |
| |
| 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); |
| |
| if (!isDebugSection(NSec)) |
| NSec.GraphSection = &G->createSection(*Name, Prot); |
| else |
| LLVM_DEBUG({ |
| dbgs() << " " << *Name |
| << " is a debug section: No graph section will be created.\n"; |
| }); |
| |
| 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 " + |
| formatv("\"{0}/{1}\" [ {2:x16} -- {3:x16} ] ", Cur.SegName, |
| Cur.SectName, Cur.Address, Cur.Address + Cur.Size) + |
| "overlaps section \"" + Next.SegName + "/" + Next.SectName + "\"" + |
| formatv("\"{0}/{1}\" [ {2:x16} -- {3:x16} ] ", Next.SegName, |
| Next.SectName, 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. |
| if (Sect != 0) { |
| auto NSec = findSectionByIndex(Sect - 1); |
| if (!NSec) |
| return NSec.takeError(); |
| |
| if (Value < NSec->Address || Value > NSec->Address + NSec->Size) |
| return make_error<JITLinkError>("Symbol address does not fall within " |
| "section"); |
| |
| if (!NSec->GraphSection) { |
| LLVM_DEBUG({ |
| dbgs() << " Skipping: Symbol is in section " << NSec->SegName << "/" |
| << NSec->SectName |
| << " which has no associated graph section.\n"; |
| }); |
| continue; |
| } |
| } |
| |
| IndexToSymbol[SymbolIndex] = |
| &createNormalizedSymbol(*Name, Value, Type, Sect, Desc, |
| getLinkage(Desc), 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; |
| |
| if (!NSec.GraphSection) { |
| LLVM_DEBUG({ |
| dbgs() << " " << NSec.SegName << "/" << NSec.SectName |
| << " has no graph section. Skipping.\n"; |
| }); |
| continue; |
| } |
| |
| // 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; |
| |
| // Skip non-graph sections. |
| if (!NSec.GraphSection) |
| continue; |
| |
| 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 |
