//===- 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 <llvm/Support/ELF.h>
#include <cstdint>
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);
/// mergeFlags - update set of ELF header flags
virtual void mergeFlags(Input& pInput, const char* ELF_hdr) {}
/// 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() const { return INT64_MAX; }
/// maxBwdBranchOffset - return the max backward branch offset of the backend.
/// Target can override this function if needed.
virtual int64_t maxBwdBranchOffset() const { return 0; }
/// stubGroupSize - return the group size to place stubs between sections.
virtual unsigned stubGroupSize() const;
/// 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<LDSymbol*, size_t, SymCompare> SymHashEntryType;
typedef HashTable<SymHashEntryType,
SymPtrHash,
EntryFactory<SymHashEntryType> > 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_