//===- GNULDBackend.h -----------------------------------------------------===// // // The MCLinker Project // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// #ifndef MCLD_TARGET_GNULDBACKEND_H_ #define MCLD_TARGET_GNULDBACKEND_H_ #include "mcld/Module.h" #include "mcld/LD/ELFBinaryReader.h" #include "mcld/LD/ELFDynObjReader.h" #include "mcld/LD/ELFObjectReader.h" #include "mcld/LD/ELFObjectWriter.h" #include "mcld/LD/GNUArchiveReader.h" #include "mcld/Target/TargetLDBackend.h" #include #include namespace mcld { class BranchIslandFactory; class EhFrameHdr; class ELFAttribute; class ELFDynamic; class ELFDynObjFileFormat; class ELFExecFileFormat; class ELFFileFormat; class ELFObjectFileFormat; class ELFSegmentFactory; class GNUInfo; class IRBuilder; class Layout; class LinkerConfig; class LinkerScript; class Module; class Relocation; class StubFactory; /** \class GNULDBackend * \brief GNULDBackend provides a common interface for all GNU Unix-OS * LDBackend. */ class GNULDBackend : public TargetLDBackend { protected: GNULDBackend(const LinkerConfig& pConfig, GNUInfo* pInfo); public: virtual ~GNULDBackend(); // ----- readers/writers ----- // GNUArchiveReader* createArchiveReader(Module& pModule); ELFObjectReader* createObjectReader(IRBuilder& pBuilder); ELFDynObjReader* createDynObjReader(IRBuilder& pBuilder); ELFBinaryReader* createBinaryReader(IRBuilder& pBuilder); ELFObjectWriter* createWriter(); // ----- output sections ----- // /// initStdSections - initialize standard sections of the output file. bool initStdSections(ObjectBuilder& pBuilder); /// getOutputFormat - get the sections of the output file. const ELFFileFormat* getOutputFormat() const; ELFFileFormat* getOutputFormat(); // ----- target symbols ----- // /// initStandardSymbols - initialize standard symbols. /// Some section symbols is undefined in input object, and linkers must set /// up its value. Take __init_array_begin for example. This symbol is an /// undefined symbol in input objects. ObjectLinker must finalize its value /// to the begin of the .init_array section, then relocation enties to /// __init_array_begin can be applied without emission of "undefined /// reference to `__init_array_begin'". bool initStandardSymbols(IRBuilder& pBuilder, Module& pModule); /// finalizeSymbol - Linker checks pSymbol.reserved() if it's not zero, /// then it will ask backend to finalize the symbol value. /// @return ture - if backend set the symbol value sucessfully /// @return false - if backend do not recognize the symbol bool finalizeSymbols() { return (finalizeStandardSymbols() && finalizeTargetSymbols()); } /// finalizeStandardSymbols - set the value of standard symbols virtual bool finalizeStandardSymbols(); /// finalizeTargetSymbols - set the value of target symbols virtual bool finalizeTargetSymbols() = 0; /// finalizeTLSSymbol - set the value of a TLS symbol virtual bool finalizeTLSSymbol(LDSymbol& pSymbol); size_t sectionStartOffset() const; const GNUInfo& getInfo() const { return *m_pInfo; } GNUInfo& getInfo() { return *m_pInfo; } bool hasTextRel() const { return m_bHasTextRel; } bool hasStaticTLS() const { return m_bHasStaticTLS; } /// getSegmentStartAddr - return the start address of the segment uint64_t getSegmentStartAddr(const LinkerScript& pScript) const; /// sizeShstrtab - compute the size of .shstrtab void sizeShstrtab(Module& pModule); /// sizeNamePools - compute the size of regular name pools /// In ELF executable files, regular name pools are .symtab, .strtab., /// .dynsym, .dynstr, and .hash virtual void sizeNamePools(Module& pModule); /// emitSectionData - emit target-dependent section data virtual uint64_t emitSectionData(const LDSection& pSection, MemoryRegion& pRegion) const = 0; /// emitRegNamePools - emit regular name pools - .symtab, .strtab virtual void emitRegNamePools(const Module& pModule, FileOutputBuffer& pOutput); /// emitNamePools - emit dynamic name pools - .dyntab, .dynstr, .hash virtual void emitDynNamePools(Module& pModule, FileOutputBuffer& pOutput); /// emitELFHashTab - emit .hash virtual void emitELFHashTab(const Module::SymbolTable& pSymtab, FileOutputBuffer& pOutput); /// emitGNUHashTab - emit .gnu.hash virtual void emitGNUHashTab(Module::SymbolTable& pSymtab, FileOutputBuffer& pOutput); /// sizeInterp - compute the size of program interpreter's name /// In ELF executables, this is the length of dynamic linker's path name virtual void sizeInterp(); /// emitInterp - emit the .interp virtual void emitInterp(FileOutputBuffer& pOutput); /// hasEntryInStrTab - symbol has an entry in a .strtab virtual bool hasEntryInStrTab(const LDSymbol& pSym) const; /// orderSymbolTable - order symbol table before emitting virtual void orderSymbolTable(Module& pModule); void setHasStaticTLS(bool pVal = true) { m_bHasStaticTLS = pVal; } /// getSectionOrder - compute the layout order of the section /// Layout calls this function to get the default order of the pSectHdr. /// If the pSectHdr.type() is LDFileFormat::Target, then getSectionOrder() /// will call getTargetSectionOrder(). /// /// If targets favors certain order for general sections, please override /// this function. /// /// @see getTargetSectionOrder virtual unsigned int getSectionOrder(const LDSection& pSectHdr) const; /// getTargetSectionOrder - compute the layout order of target section /// If the target favors certain order for the given gSectHdr, please /// override this function. /// /// By default, this function returns the maximun order, and pSectHdr /// will be the last section to be laid out. virtual unsigned int getTargetSectionOrder(const LDSection& pSectHdr) const { return (unsigned int)-1; } /// elfSegmentTable - return the reference of the elf segment table ELFSegmentFactory& elfSegmentTable(); /// elfSegmentTable - return the reference of the elf segment table const ELFSegmentFactory& elfSegmentTable() const; /// commonPageSize - the common page size of the target machine uint64_t commonPageSize() const; /// abiPageSize - the abi page size of the target machine uint64_t abiPageSize() const; /// getSymbolIdx - get the symbol index of ouput symbol table size_t getSymbolIdx(const LDSymbol* pSymbol) const; /// allocateCommonSymbols - allocate common symbols in the corresponding /// sections. /// Different concrete target backend may overlap this function. virtual bool allocateCommonSymbols(Module& pModule); /// updateSectionFlags - update pTo's flags when merging pFrom /// update the output section flags based on input section flags. virtual bool updateSectionFlags(LDSection& pTo, const LDSection& pFrom); /// readRelocation - read ELF32_Rel entry virtual bool readRelocation(const llvm::ELF::Elf32_Rel& pRel, uint32_t& pType, uint32_t& pSymIdx, uint32_t& pOffset) const; /// readRelocation - read ELF32_Rela entry virtual bool readRelocation(const llvm::ELF::Elf32_Rela& pRel, uint32_t& pType, uint32_t& pSymIdx, uint32_t& pOffset, int32_t& pAddend) const; /// readRelocation - read ELF64_Rel entry virtual bool readRelocation(const llvm::ELF::Elf64_Rel& pRel, uint32_t& pType, uint32_t& pSymIdx, uint64_t& pOffset) const; /// readRel - read ELF64_Rela entry virtual bool readRelocation(const llvm::ELF::Elf64_Rela& pRel, uint32_t& pType, uint32_t& pSymIdx, uint64_t& pOffset, int64_t& pAddend) const; /// emitRelocation - write data to the ELF32_Rel entry virtual void emitRelocation(llvm::ELF::Elf32_Rel& pRel, uint32_t pType, uint32_t pSymIdx, uint32_t pOffset) const; /// emitRelocation - write data to the ELF32_Rela entry virtual void emitRelocation(llvm::ELF::Elf32_Rela& pRel, uint32_t pType, uint32_t pSymIdx, uint32_t pOffset, int32_t pAddend) const; /// emitRelocation - write data to the ELF64_Rel entry virtual void emitRelocation(llvm::ELF::Elf64_Rel& pRel, uint32_t pType, uint32_t pSymIdx, uint64_t pOffset) const; /// emitRelocation - write data to the ELF64_Rela entry virtual void emitRelocation(llvm::ELF::Elf64_Rela& pRel, uint32_t pType, uint32_t pSymIdx, uint64_t pOffset, int64_t pAddend) const; /// symbolNeedsPLT - return whether the symbol needs a PLT entry bool symbolNeedsPLT(const ResolveInfo& pSym) const; /// symbolNeedsCopyReloc - return whether the symbol needs a copy relocation bool symbolNeedsCopyReloc(const Relocation& pReloc, const ResolveInfo& pSym) const; /// symbolNeedsDynRel - return whether the symbol needs a dynamic relocation bool symbolNeedsDynRel(const ResolveInfo& pSym, bool pSymHasPLT, bool isAbsReloc) const; /// isSymbolPreemptible - whether the symbol can be preemted by other link /// units bool isSymbolPreemptible(const ResolveInfo& pSym) const; /// symbolHasFinalValue - return true if the symbol's value can be decided at /// link time bool symbolFinalValueIsKnown(const ResolveInfo& pSym) const; /// isDynamicSymbol bool isDynamicSymbol(const LDSymbol& pSymbol) const; /// isDynamicSymbol bool isDynamicSymbol(const ResolveInfo& pResolveInfo) const; virtual ResolveInfo::Desc getSymDesc(uint16_t pShndx) const { return ResolveInfo::Define; } bool hasTDATASymbol() const { return (f_pTDATA != NULL); } bool hasTBSSSymbol() const { return (f_pTBSS != NULL); } void setTDATASymbol(LDSymbol& pTDATA) { f_pTDATA = &pTDATA; } void setTBSSSymbol(LDSymbol& pTBSS) { f_pTBSS = &pTBSS; } // getTDATASymbol - get section symbol of .tdata LDSymbol& getTDATASymbol(); const LDSymbol& getTDATASymbol() const; /// getTBSSSymbol - get section symbol of .tbss LDSymbol& getTBSSSymbol(); const LDSymbol& getTBSSSymbol() const; /// getEntry - get the entry point name llvm::StringRef getEntry(const Module& pModule) const; // ----- relaxation ----- // /// initBRIslandFactory - initialize the branch island factory for relaxation bool initBRIslandFactory(); /// initStubFactory - initialize the stub factory for relaxation bool initStubFactory(); /// getBRIslandFactory BranchIslandFactory* getBRIslandFactory() { return m_pBRIslandFactory; } /// getStubFactory StubFactory* getStubFactory() { return m_pStubFactory; } /// maxFwdBranchOffset - return the max forward branch offset of the backend. /// Target can override this function if needed. virtual int64_t maxFwdBranchOffset() { return INT64_MAX; } /// maxBwdBranchOffset - return the max backward branch offset of the backend. /// Target can override this function if needed. virtual int64_t maxBwdBranchOffset() { return 0; } /// checkAndSetHasTextRel - check pSection flag to set HasTextRel void checkAndSetHasTextRel(const LDSection& pSection); /// sortRelocation - sort the dynamic relocations to let dynamic linker /// process relocations more efficiently void sortRelocation(LDSection& pSection); /// createAndSizeEhFrameHdr - This is seperated since we may add eh_frame /// entry in the middle void createAndSizeEhFrameHdr(Module& pModule); /// attribute - the attribute section data. ELFAttribute& attribute() { return *m_pAttribute; } /// attribute - the attribute section data. const ELFAttribute& attribute() const { return *m_pAttribute; } /// mayHaveUnsafeFunctionPointerAccess - check if the section may have unsafe /// function pointer access bool mayHaveUnsafeFunctionPointerAccess(const LDSection& pSection) const; protected: /// getRelEntrySize - the size in BYTE of rel type relocation virtual size_t getRelEntrySize() = 0; /// getRelEntrySize - the size in BYTE of rela type relocation virtual size_t getRelaEntrySize() = 0; uint64_t getSymbolSize(const LDSymbol& pSymbol) const; uint64_t getSymbolInfo(const LDSymbol& pSymbol) const; uint64_t getSymbolValue(const LDSymbol& pSymbol) const; uint64_t getSymbolShndx(const LDSymbol& pSymbol) const; /// isTemporary - Whether pSymbol is a local label. virtual bool isTemporary(const LDSymbol& pSymbol) const; /// getHashBucketCount - calculate hash bucket count. static unsigned getHashBucketCount(unsigned pNumOfSymbols, bool pIsGNUStyle); /// getGNUHashMaskbitslog2 - calculate the number of mask bits in log2 unsigned getGNUHashMaskbitslog2(unsigned pNumOfSymbols) const; /// emitSymbol32 - emit an ELF32 symbol void emitSymbol32(llvm::ELF::Elf32_Sym& pSym32, LDSymbol& pSymbol, char* pStrtab, size_t pStrtabsize, size_t pSymtabIdx); /// emitSymbol64 - emit an ELF64 symbol void emitSymbol64(llvm::ELF::Elf64_Sym& pSym64, LDSymbol& pSymbol, char* pStrtab, size_t pStrtabsize, size_t pSymtabIdx); protected: /// createProgramHdrs - base on output sections to create the program headers void createProgramHdrs(Module& pModule); /// doCreateProgramHdrs - backend can implement this function to create the /// target-dependent segments virtual void doCreateProgramHdrs(Module& pModule) = 0; /// setupProgramHdrs - set up the attributes of segments /// (i.e., offset, addresses, file/mem size, flag, and alignment) void setupProgramHdrs(const LinkerScript& pScript); /// getSegmentFlag - give a section flag and return the corresponding segment /// flag inline uint32_t getSegmentFlag(const uint32_t pSectionFlag); /// setupGNUStackInfo - setup the section flag of .note.GNU-stack in output void setupGNUStackInfo(Module& pModule); /// setOutputSectionOffset - helper function to set output sections' offset. void setOutputSectionOffset(Module& pModule); /// setOutputSectionAddress - helper function to set output sections' address. void setOutputSectionAddress(Module& pModule); /// placeOutputSections - place output sections based on SectionMap void placeOutputSections(Module& pModule); /// layout - layout method void layout(Module& pModule); /// preLayout - Backend can do any needed modification before layout void preLayout(Module& pModule, IRBuilder& pBuilder); /// postLayout -Backend can do any needed modification after layout void postLayout(Module& pModule, IRBuilder& pBuilder); /// preLayout - Backend can do any needed modification before layout virtual void doPreLayout(IRBuilder& pBuilder) = 0; /// postLayout -Backend can do any needed modification after layout virtual void doPostLayout(Module& pModule, IRBuilder& pLinker) = 0; /// postProcessing - Backend can do any needed modification in the final stage void postProcessing(FileOutputBuffer& pOutput); /// dynamic - the dynamic section of the target machine. virtual ELFDynamic& dynamic() = 0; /// dynamic - the dynamic section of the target machine. virtual const ELFDynamic& dynamic() const = 0; /// relax - the relaxation pass virtual bool relax(Module& pModule, IRBuilder& pBuilder); /// mayRelax - Backends should override this function if they need relaxation virtual bool mayRelax() { return false; } /// doRelax - Backend can orevride this function to add its relaxation /// implementation. Return true if the output (e.g., .text) is "relaxed" /// (i.e. layout is changed), and set pFinished to true if everything is fit, /// otherwise set it to false. virtual bool doRelax(Module& pModule, IRBuilder& pBuilder, bool& pFinished) { return false; } protected: // Based on Kind in LDFileFormat to define basic section orders for ELF. enum SectionOrder { SHO_NULL = 0, // NULL SHO_INTERP, // .interp SHO_RO_NOTE, // .note.ABI-tag, .note.gnu.build-id SHO_NAMEPOOL, // *.hash, .dynsym, .dynstr SHO_RELOCATION, // .rel.*, .rela.* SHO_REL_PLT, // .rel.plt should come after other .rel.* SHO_INIT, // .init SHO_PLT, // .plt SHO_TEXT, // .text SHO_FINI, // .fini SHO_RO, // .rodata SHO_EXCEPTION, // .eh_frame_hdr, .eh_frame, .gcc_except_table SHO_TLS_DATA, // .tdata SHO_TLS_BSS, // .tbss SHO_RELRO_LOCAL, // .data.rel.ro.local SHO_RELRO, // .data.rel.ro, SHO_RELRO_LAST, // for x86 to adjust .got if needed SHO_NON_RELRO_FIRST, // for x86 to adjust .got.plt if needed SHO_DATA, // .data SHO_LARGE_DATA, // .ldata SHO_RW_NOTE, // SHO_SMALL_DATA, // .sdata SHO_SMALL_BSS, // .sbss SHO_BSS, // .bss SHO_LARGE_BSS, // .lbss SHO_UNDEFINED, // default order SHO_STRTAB // .strtab }; // for -z combreloc struct RelocCompare { explicit RelocCompare(const GNULDBackend& pBackend) : m_Backend(pBackend) {} bool operator()(const Relocation& X, const Relocation& Y) const; private: const GNULDBackend& m_Backend; }; // for gnu style hash table struct DynsymCompare { bool needGNUHash(const LDSymbol& X) const; bool operator()(const LDSymbol* X, const LDSymbol* Y) const; }; struct SymCompare { bool operator()(const LDSymbol* X, const LDSymbol* Y) const { return (X == Y); } }; struct SymPtrHash { size_t operator()(const LDSymbol* pKey) const { return (unsigned((uintptr_t)pKey) >> 4) ^ (unsigned((uintptr_t)pKey) >> 9); } }; typedef HashEntry SymHashEntryType; typedef HashTable > HashTableType; protected: ELFObjectReader* m_pObjectReader; // ----- file formats ----- // ELFDynObjFileFormat* m_pDynObjFileFormat; ELFExecFileFormat* m_pExecFileFormat; ELFObjectFileFormat* m_pObjectFileFormat; // GNUInfo GNUInfo* m_pInfo; // ELF segment factory ELFSegmentFactory* m_pELFSegmentTable; // branch island factory BranchIslandFactory* m_pBRIslandFactory; // stub factory StubFactory* m_pStubFactory; // map the LDSymbol to its index in the output symbol table HashTableType* m_pSymIndexMap; // section .eh_frame_hdr EhFrameHdr* m_pEhFrameHdr; // attribute section ELFAttribute* m_pAttribute; // ----- dynamic flags ----- // // DF_TEXTREL of DT_FLAGS bool m_bHasTextRel; // DF_STATIC_TLS of DT_FLAGS bool m_bHasStaticTLS; // ----- standard symbols ----- // // section symbols LDSymbol* f_pPreInitArrayStart; LDSymbol* f_pPreInitArrayEnd; LDSymbol* f_pInitArrayStart; LDSymbol* f_pInitArrayEnd; LDSymbol* f_pFiniArrayStart; LDSymbol* f_pFiniArrayEnd; LDSymbol* f_pStack; LDSymbol* f_pDynamic; // section symbols for .tdata and .tbss LDSymbol* f_pTDATA; LDSymbol* f_pTBSS; // segment symbols LDSymbol* f_pExecutableStart; LDSymbol* f_pEText; LDSymbol* f_p_EText; LDSymbol* f_p__EText; LDSymbol* f_pEData; LDSymbol* f_p_EData; LDSymbol* f_pBSSStart; LDSymbol* f_pEnd; LDSymbol* f_p_End; }; } // namespace mcld #endif // MCLD_TARGET_GNULDBACKEND_H_