| //===---- ELF_x86_64.cpp -JIT linker implementation for ELF/x86-64 ----===// |
| // |
| // 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 |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // ELF/x86-64 jit-link implementation. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/ExecutionEngine/JITLink/ELF_x86_64.h" |
| #include "JITLinkGeneric.h" |
| #include "llvm/ExecutionEngine/JITLink/JITLink.h" |
| #include "llvm/Object/ELFObjectFile.h" |
| |
| #define DEBUG_TYPE "jitlink" |
| |
| using namespace llvm; |
| using namespace llvm::jitlink; |
| |
| static const char *CommonSectionName = "__common"; |
| |
| namespace llvm { |
| namespace jitlink { |
| |
| // This should become a template as the ELFFile is so a lot of this could become |
| // generic |
| class ELFLinkGraphBuilder_x86_64 { |
| |
| private: |
| Section *CommonSection = nullptr; |
| // TODO hack to get this working |
| // Find a better way |
| using SymbolTable = object::ELFFile<object::ELF64LE>::Elf_Shdr; |
| // For now we just assume |
| std::map<int32_t, Symbol *> JITSymbolTable; |
| |
| Section &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; |
| } |
| |
| static Expected<ELF_x86_64_Edges::ELFX86RelocationKind> |
| getRelocationKind(const uint32_t Type) { |
| switch (Type) { |
| case ELF::R_X86_64_PC32: |
| return ELF_x86_64_Edges::ELFX86RelocationKind::PCRel32; |
| } |
| return make_error<JITLinkError>("Unsupported x86-64 relocation:" + |
| formatv("{0:d}", Type)); |
| } |
| |
| std::unique_ptr<LinkGraph> G; |
| // This could be a template |
| const object::ELFFile<object::ELF64LE> &Obj; |
| object::ELFFile<object::ELF64LE>::Elf_Shdr_Range sections; |
| SymbolTable SymTab; |
| |
| bool isRelocatable() { return Obj.getHeader()->e_type == llvm::ELF::ET_REL; } |
| |
| support::endianness |
| getEndianness(const object::ELFFile<object::ELF64LE> &Obj) { |
| return Obj.isLE() ? support::little : support::big; |
| } |
| |
| // This could also just become part of a template |
| unsigned getPointerSize(const object::ELFFile<object::ELF64LE> &Obj) { |
| return Obj.getHeader()->getFileClass() == ELF::ELFCLASS64 ? 8 : 4; |
| } |
| |
| // We don't technically need this right now |
| // But for now going to keep it as it helps me to debug things |
| |
| Error createNormalizedSymbols() { |
| LLVM_DEBUG(dbgs() << "Creating normalized symbols...\n"); |
| |
| for (auto SecRef : sections) { |
| if (SecRef.sh_type != ELF::SHT_SYMTAB && |
| SecRef.sh_type != ELF::SHT_DYNSYM) |
| continue; |
| |
| auto Symbols = Obj.symbols(&SecRef); |
| // TODO: Currently I use this function to test things |
| // I also want to leave it to see if its common between MACH and elf |
| // so for now I just want to continue even if there is an error |
| if (errorToBool(Symbols.takeError())) |
| continue; |
| |
| auto StrTabSec = Obj.getSection(SecRef.sh_link); |
| if (!StrTabSec) |
| return StrTabSec.takeError(); |
| auto StringTable = Obj.getStringTable(*StrTabSec); |
| if (!StringTable) |
| return StringTable.takeError(); |
| |
| for (auto SymRef : *Symbols) { |
| Optional<StringRef> Name; |
| uint64_t Size = 0; |
| |
| // FIXME: Read size. |
| (void)Size; |
| |
| if (auto NameOrErr = SymRef.getName(*StringTable)) |
| Name = *NameOrErr; |
| else |
| return NameOrErr.takeError(); |
| |
| LLVM_DEBUG({ |
| dbgs() << " "; |
| if (!Name) |
| dbgs() << "<anonymous symbol>"; |
| else |
| dbgs() << *Name; |
| dbgs() << ": value = " << formatv("{0:x16}", SymRef.getValue()) |
| << ", type = " << formatv("{0:x2}", SymRef.getType()) |
| << ", binding = " << SymRef.getBinding() |
| << ", size =" << Size; |
| dbgs() << "\n"; |
| }); |
| } |
| } |
| return Error::success(); |
| } |
| |
| Error createNormalizedSections() { |
| LLVM_DEBUG(dbgs() << "Creating normalized sections...\n"); |
| for (auto &SecRef : sections) { |
| auto Name = Obj.getSectionName(&SecRef); |
| if (!Name) |
| return Name.takeError(); |
| sys::Memory::ProtectionFlags Prot; |
| if (SecRef.sh_flags & ELF::SHF_EXECINSTR) { |
| 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); |
| } |
| uint64_t Address = SecRef.sh_addr; |
| uint64_t Size = SecRef.sh_size; |
| uint64_t Flags = SecRef.sh_flags; |
| uint64_t Alignment = SecRef.sh_addralign; |
| const char *Data = nullptr; |
| // TODO: figure out what it is that has 0 size no name and address |
| // 0000-0000 |
| if (Size == 0) |
| continue; |
| |
| // FIXME: Use flags. |
| (void)Flags; |
| |
| LLVM_DEBUG({ |
| dbgs() << " " << *Name << ": " << formatv("{0:x16}", Address) << " -- " |
| << formatv("{0:x16}", Address + Size) << ", align: " << Alignment |
| << " Flags:" << Flags << "\n"; |
| }); |
| |
| if (SecRef.sh_type != ELF::SHT_NOBITS) { |
| // .sections() already checks that the data is not beyond the end of |
| // file |
| auto contents = Obj.getSectionContentsAsArray<char>(&SecRef); |
| if (!contents) |
| return contents.takeError(); |
| |
| Data = contents->data(); |
| // TODO protection flags. |
| // for now everything is |
| auto §ion = G->createSection(*Name, Prot); |
| // Do this here because we have it, but move it into graphify later |
| G->createContentBlock(section, StringRef(Data, Size), Address, |
| Alignment, 0); |
| if (SecRef.sh_type == ELF::SHT_SYMTAB) |
| // TODO: Dynamic? |
| SymTab = SecRef; |
| } |
| } |
| |
| return Error::success(); |
| } |
| |
| Error addRelocations() { |
| LLVM_DEBUG(dbgs() << "Adding relocations\n"); |
| // TODO a partern is forming of iterate some sections but only give me |
| // ones I am interested, i should abstract that concept some where |
| for (auto &SecRef : sections) { |
| if (SecRef.sh_type != ELF::SHT_RELA && SecRef.sh_type != ELF::SHT_REL) |
| continue; |
| // TODO can the elf obj file do this for me? |
| if (SecRef.sh_type == ELF::SHT_REL) |
| return make_error<llvm::StringError>("Shouldn't have REL in x64", |
| llvm::inconvertibleErrorCode()); |
| |
| auto RelSectName = Obj.getSectionName(&SecRef); |
| if (!RelSectName) |
| return RelSectName.takeError(); |
| // Deal with .eh_frame later |
| if (*RelSectName == StringRef(".rela.eh_frame")) |
| continue; |
| |
| auto UpdateSection = Obj.getSection(SecRef.sh_info); |
| if (!UpdateSection) |
| return UpdateSection.takeError(); |
| |
| auto UpdateSectionName = Obj.getSectionName(*UpdateSection); |
| if (!UpdateSectionName) |
| return UpdateSectionName.takeError(); |
| |
| auto JITSection = G->findSectionByName(*UpdateSectionName); |
| if (!JITSection) |
| return make_error<llvm::StringError>( |
| "Refencing a a section that wasn't added to graph" + |
| *UpdateSectionName, |
| llvm::inconvertibleErrorCode()); |
| |
| auto Relocations = Obj.relas(&SecRef); |
| if (!Relocations) |
| return Relocations.takeError(); |
| |
| for (const auto &Rela : *Relocations) { |
| auto Type = Rela.getType(false); |
| |
| LLVM_DEBUG({ |
| dbgs() << "Relocation Type: " << Type << "\n" |
| << "Name: " << Obj.getRelocationTypeName(Type) << "\n"; |
| }); |
| |
| auto Symbol = Obj.getRelocationSymbol(&Rela, &SymTab); |
| if (!Symbol) |
| return Symbol.takeError(); |
| |
| auto BlockToFix = *(JITSection->blocks().begin()); |
| auto TargetSymbol = JITSymbolTable[(*Symbol)->st_shndx]; |
| uint64_t Addend = Rela.r_addend; |
| JITTargetAddress FixupAddress = |
| (*UpdateSection)->sh_addr + Rela.r_offset; |
| |
| LLVM_DEBUG({ |
| dbgs() << "Processing relocation at " |
| << format("0x%016" PRIx64, FixupAddress) << "\n"; |
| }); |
| auto Kind = getRelocationKind(Type); |
| if (!Kind) |
| return Kind.takeError(); |
| |
| LLVM_DEBUG({ |
| Edge GE(*Kind, FixupAddress - BlockToFix->getAddress(), *TargetSymbol, |
| Addend); |
| // TODO a mapping of KIND => type then call getRelocationTypeName4 |
| printEdge(dbgs(), *BlockToFix, GE, StringRef("")); |
| dbgs() << "\n"; |
| }); |
| BlockToFix->addEdge(*Kind, FixupAddress - BlockToFix->getAddress(), |
| *TargetSymbol, Addend); |
| } |
| } |
| return Error::success(); |
| } |
| |
| Error graphifyRegularSymbols() { |
| |
| // TODO: ELF supports beyond SHN_LORESERVE, |
| // need to perf test how a vector vs map handles those cases |
| |
| std::vector<std::vector<object::ELFFile<object::ELF64LE>::Elf_Shdr_Range *>> |
| SecIndexToSymbols; |
| |
| LLVM_DEBUG(dbgs() << "Creating graph symbols...\n"); |
| |
| for (auto SecRef : sections) { |
| |
| if (SecRef.sh_type != ELF::SHT_SYMTAB && |
| SecRef.sh_type != ELF::SHT_DYNSYM) |
| continue; |
| auto Symbols = Obj.symbols(&SecRef); |
| if (!Symbols) |
| return Symbols.takeError(); |
| |
| auto StrTabSec = Obj.getSection(SecRef.sh_link); |
| if (!StrTabSec) |
| return StrTabSec.takeError(); |
| auto StringTable = Obj.getStringTable(*StrTabSec); |
| if (!StringTable) |
| return StringTable.takeError(); |
| auto Name = Obj.getSectionName(&SecRef); |
| if (!Name) |
| return Name.takeError(); |
| auto Section = G->findSectionByName(*Name); |
| if (!Section) |
| return make_error<llvm::StringError>("Could not find a section", |
| llvm::inconvertibleErrorCode()); |
| // we only have one for now |
| auto blocks = Section->blocks(); |
| if (blocks.empty()) |
| return make_error<llvm::StringError>("Section has no block", |
| llvm::inconvertibleErrorCode()); |
| |
| for (auto SymRef : *Symbols) { |
| auto Type = SymRef.getType(); |
| if (Type == ELF::STT_NOTYPE || Type == ELF::STT_FILE) |
| continue; |
| // these should do it for now |
| // if(Type != ELF::STT_NOTYPE && |
| // Type != ELF::STT_OBJECT && |
| // Type != ELF::STT_FUNC && |
| // Type != ELF::STT_SECTION && |
| // Type != ELF::STT_COMMON) { |
| // continue; |
| // } |
| std::pair<Linkage, Scope> bindings; |
| auto Name = SymRef.getName(*StringTable); |
| // I am not sure on If this is going to hold as an invariant. Revisit. |
| if (!Name) |
| return Name.takeError(); |
| // TODO: weak and hidden |
| if (SymRef.isExternal()) |
| bindings = {Linkage::Strong, Scope::Default}; |
| else |
| bindings = {Linkage::Strong, Scope::Local}; |
| |
| if (SymRef.isDefined() && |
| (Type == ELF::STT_FUNC || Type == ELF::STT_OBJECT)) { |
| |
| auto DefinedSection = Obj.getSection(SymRef.st_shndx); |
| if (!DefinedSection) |
| return DefinedSection.takeError(); |
| auto sectName = Obj.getSectionName(*DefinedSection); |
| if (!sectName) |
| return Name.takeError(); |
| |
| auto JitSection = G->findSectionByName(*sectName); |
| if (!JitSection) |
| return make_error<llvm::StringError>( |
| "Could not find a section", llvm::inconvertibleErrorCode()); |
| auto bs = JitSection->blocks(); |
| if (bs.empty()) |
| return make_error<llvm::StringError>( |
| "Section has no block", llvm::inconvertibleErrorCode()); |
| |
| auto B = *bs.begin(); |
| LLVM_DEBUG({ dbgs() << " " << *Name << ": "; }); |
| |
| auto &S = G->addDefinedSymbol( |
| *B, SymRef.getValue(), *Name, SymRef.st_size, bindings.first, |
| bindings.second, SymRef.getType() == ELF::STT_FUNC, false); |
| JITSymbolTable[SymRef.st_shndx] = &S; |
| } |
| //TODO: The following has to be implmented. |
| // leaving commented out to save time for future patchs |
| /* |
| G->addAbsoluteSymbol(*Name, SymRef.getValue(), SymRef.st_size, |
| Linkage::Strong, Scope::Default, false); |
| |
| if(SymRef.isCommon()) { |
| G->addCommonSymbol(*Name, Scope::Default, getCommonSection(), 0, 0, |
| SymRef.getValue(), false); |
| } |
| |
| |
| //G->addExternalSymbol(*Name, SymRef.st_size, Linkage::Strong); |
| */ |
| } |
| } |
| return Error::success(); |
| } |
| |
| public: |
| ELFLinkGraphBuilder_x86_64(std::string filename, |
| const object::ELFFile<object::ELF64LE> &Obj) |
| : G(std::make_unique<LinkGraph>(filename, getPointerSize(Obj), |
| getEndianness(Obj))), |
| Obj(Obj) {} |
| |
| Expected<std::unique_ptr<LinkGraph>> buildGraph() { |
| // Sanity check: we only operate on relocatable objects. |
| if (!isRelocatable()) |
| return make_error<JITLinkError>("Object is not a relocatable ELF"); |
| |
| auto Secs = Obj.sections(); |
| |
| if (!Secs) { |
| return Secs.takeError(); |
| } |
| sections = *Secs; |
| |
| 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 = addRelocations()) |
| return std::move(Err); |
| |
| return std::move(G); |
| } |
| }; |
| |
| class ELFJITLinker_x86_64 : public JITLinker<ELFJITLinker_x86_64> { |
| friend class JITLinker<ELFJITLinker_x86_64>; |
| |
| public: |
| ELFJITLinker_x86_64(std::unique_ptr<JITLinkContext> Ctx, |
| PassConfiguration PassConfig) |
| : JITLinker(std::move(Ctx), std::move(PassConfig)) {} |
| |
| private: |
| StringRef getEdgeKindName(Edge::Kind R) const override { return StringRef(); } |
| |
| Expected<std::unique_ptr<LinkGraph>> |
| buildGraph(MemoryBufferRef ObjBuffer) override { |
| auto ELFObj = object::ObjectFile::createELFObjectFile(ObjBuffer); |
| if (!ELFObj) |
| return ELFObj.takeError(); |
| |
| auto &ELFObjFile = cast<object::ELFObjectFile<object::ELF64LE>>(**ELFObj); |
| std::string fileName(ELFObj->get()->getFileName()); |
| return ELFLinkGraphBuilder_x86_64(std::move(fileName), |
| *ELFObjFile.getELFFile()) |
| .buildGraph(); |
| } |
| |
| Error applyFixup(Block &B, const Edge &E, char *BlockWorkingMem) const { |
| using namespace ELF_x86_64_Edges; |
| char *FixupPtr = BlockWorkingMem + E.getOffset(); |
| JITTargetAddress FixupAddress = B.getAddress() + E.getOffset(); |
| switch (E.getKind()) { |
| |
| case ELFX86RelocationKind::PCRel32: |
| int64_t Value = E.getTarget().getAddress() + E.getAddend() - FixupAddress; |
| // verify |
| *(support::little32_t *)FixupPtr = Value; |
| break; |
| } |
| return Error::success(); |
| } |
| }; |
| |
| void jitLink_ELF_x86_64(std::unique_ptr<JITLinkContext> Ctx) { |
| PassConfiguration Config; |
| Triple TT("x86_64-linux"); |
| // Construct a JITLinker and run the link function. |
| // Add a mark-live pass. |
| if (auto MarkLive = Ctx->getMarkLivePass(TT)) |
| Config.PrePrunePasses.push_back(std::move(MarkLive)); |
| else |
| Config.PrePrunePasses.push_back(markAllSymbolsLive); |
| |
| if (auto Err = Ctx->modifyPassConfig(TT, Config)) |
| return Ctx->notifyFailed(std::move(Err)); |
| |
| ELFJITLinker_x86_64::link(std::move(Ctx), std::move(Config)); |
| } |
| } // end namespace jitlink |
| } // end namespace llvm |