lib/CodeGen/ELFWriter.h

   1 //===-- ELFWriter.h - Target-independent ELF writer support -----*- C++ -*-===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file defines the ELFWriter class.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #ifndef ELFWRITER_H
  15 #define ELFWRITER_H
  16
  17 #include "llvm/ADT/SetVector.h"
  18 #include "llvm/CodeGen/MachineFunctionPass.h"
  19 #include <map>
  20
  21 namespace llvm {
  22   class BinaryObject;
  23   class Constant;
  24   class ConstantInt;
  25   class ConstantStruct;
  26   class ELFCodeEmitter;
  27   class ELFRelocation;
  28   class ELFSection;
  29   struct ELFSym;
  30   class GlobalVariable;
  31   class JITDebugRegisterer;
  32   class Mangler;
  33   class MachineCodeEmitter;
  34   class MachineConstantPoolEntry;
  35   class ObjectCodeEmitter;
  36   class MCAsmInfo;
  37   class TargetELFWriterInfo;
  38   class TargetLoweringObjectFile;
  39   class raw_ostream;
  40   class SectionKind;
  41   class MCContext;
  42   class TargetMachine;
  43
  44   typedef std::vector<ELFSym*>::iterator ELFSymIter;
  45   typedef std::vector<ELFSection*>::iterator ELFSectionIter;
  46   typedef SetVector<const GlobalValue*>::const_iterator PendingGblsIter;
  47   typedef SetVector<const char *>::const_iterator PendingExtsIter;
  48   typedef std::pair<const Constant *, int64_t> CstExprResTy;
  49
  50   /// ELFWriter - This class implements the common target-independent code for
  51   /// writing ELF files.  Targets should derive a class from this to
  52   /// parameterize the output format.
  53   ///
  54   class ELFWriter : public MachineFunctionPass {
  55     friend class ELFCodeEmitter;
  56     friend class JITDebugRegisterer;
  57   public:
  58     static char ID;
  59
  60     /// Return the ELFCodeEmitter as an instance of ObjectCodeEmitter
  61     ObjectCodeEmitter *getObjectCodeEmitter() {
  62       return reinterpret_cast<ObjectCodeEmitter*>(ElfCE);
  63     }
  64
  65     ELFWriter(raw_ostream &O, TargetMachine &TM);
  66     ~ELFWriter();
  67
  68   protected:
  69     /// Output stream to send the resultant object file to.
  70     raw_ostream &O;
  71
  72     /// Target machine description.
  73     TargetMachine &TM;
  74
  75     /// Context object for machine code objects.
  76     MCContext &OutContext;
  77
  78     /// Target Elf Writer description.
  79     const TargetELFWriterInfo *TEW;
  80
  81     /// Mang - The object used to perform name mangling for this module.
  82     Mangler *Mang;
  83
  84     /// MCE - The MachineCodeEmitter object that we are exposing to emit machine
  85     /// code for functions to the .o file.
  86     ELFCodeEmitter *ElfCE;
  87
  88     /// TLOF - Target Lowering Object File, provide section names for globals
  89     /// and other object file specific stuff
  90     const TargetLoweringObjectFile &TLOF;
  91
  92     /// MAI - Target Asm Info, provide information about section names for
  93     /// globals and other target specific stuff.
  94     const MCAsmInfo *MAI;
  95
  96     //===------------------------------------------------------------------===//
  97     // Properties inferred automatically from the target machine.
  98     //===------------------------------------------------------------------===//
  99
 100     /// is64Bit/isLittleEndian - This information is inferred from the target
 101     /// machine directly, indicating whether to emit a 32- or 64-bit ELF file.
 102     bool is64Bit, isLittleEndian;
 103
 104     /// doInitialization - Emit the file header and all of the global variables
 105     /// for the module to the ELF file.
 106     bool doInitialization(Module &M);
 107     bool runOnMachineFunction(MachineFunction &MF);
 108
 109     /// doFinalization - Now that the module has been completely processed, emit
 110     /// the ELF file to 'O'.
 111     bool doFinalization(Module &M);
 112
 113   private:
 114     /// Blob containing the Elf header
 115     BinaryObject ElfHdr;
 116
 117     /// SectionList - This is the list of sections that we have emitted to the
 118     /// file. Once the file has been completely built, the section header table
 119     /// is constructed from this info.
 120     std::vector<ELFSection*> SectionList;
 121     unsigned NumSections;   // Always = SectionList.size()
 122
 123     /// SectionLookup - This is a mapping from section name to section number in
 124     /// the SectionList. Used to quickly gather the Section Index from MAI names
 125     std::map<std::string, ELFSection*> SectionLookup;
 126
 127     /// PendingGlobals - Globals not processed as symbols yet.
 128     SetVector<const GlobalValue*> PendingGlobals;
 129
 130     /// GblSymLookup - This is a mapping from global value to a symbol index
 131     /// in the symbol table or private symbols list. This is useful since reloc
 132     /// symbol references must be quickly mapped to their indices on the lists.
 133     std::map<const GlobalValue*, uint32_t> GblSymLookup;
 134
 135     /// PendingExternals - Externals not processed as symbols yet.
 136     SetVector<const char *> PendingExternals;
 137
 138     /// ExtSymLookup - This is a mapping from externals to a symbol index
 139     /// in the symbol table list. This is useful since reloc symbol references
 140     /// must be quickly mapped to their symbol table indices.
 141     std::map<const char *, uint32_t> ExtSymLookup;
 142
 143     /// SymbolList - This is the list of symbols emitted to the symbol table.
 144     /// When the SymbolList is finally built, local symbols must be placed in
 145     /// the beginning while non-locals at the end.
 146     std::vector<ELFSym*> SymbolList;
 147
 148     /// PrivateSyms - Record private symbols, every symbol here must never be
 149     /// present in the SymbolList.
 150     std::vector<ELFSym*> PrivateSyms;
 151
 152     /// getSection - Return the section with the specified name, creating a new
 153     /// section if one does not already exist.
 154     ELFSection &getSection(const std::string &Name, unsigned Type,
 155                            unsigned Flags = 0, unsigned Align = 0) {
 156       ELFSection *&SN = SectionLookup[Name];
 157       if (SN) return *SN;
 158
 159       SectionList.push_back(new ELFSection(Name, isLittleEndian, is64Bit));
 160       SN = SectionList.back();
 161       SN->SectionIdx = NumSections++;
 162       SN->Type = Type;
 163       SN->Flags = Flags;
 164       SN->Link = ELF::SHN_UNDEF;
 165       SN->Align = Align;
 166       return *SN;
 167     }
 168
 169     ELFSection &getNonExecStackSection() {
 170       return getSection(".note.GNU-stack", ELF::SHT_PROGBITS, 0, 1);
 171     }
 172
 173     ELFSection &getSymbolTableSection() {
 174       return getSection(".symtab", ELF::SHT_SYMTAB, 0);
 175     }
 176
 177     ELFSection &getStringTableSection() {
 178       return getSection(".strtab", ELF::SHT_STRTAB, 0, 1);
 179     }
 180
 181     ELFSection &getSectionHeaderStringTableSection() {
 182       return getSection(".shstrtab", ELF::SHT_STRTAB, 0, 1);
 183     }
 184
 185     ELFSection &getNullSection() {
 186       return getSection("", ELF::SHT_NULL, 0);
 187     }
 188
 189     ELFSection &getDataSection();
 190     ELFSection &getBSSSection();
 191     ELFSection &getCtorSection();
 192     ELFSection &getDtorSection();
 193     ELFSection &getJumpTableSection();
 194     ELFSection &getConstantPoolSection(MachineConstantPoolEntry &CPE);
 195     ELFSection &getTextSection(const Function *F);
 196     ELFSection &getRelocSection(ELFSection &S);
 197
 198     // Helpers for obtaining ELF specific info.
 199     unsigned getGlobalELFBinding(const GlobalValue *GV);
 200     unsigned getGlobalELFType(const GlobalValue *GV);
 201     unsigned getGlobalELFVisibility(const GlobalValue *GV);
 202
 203     // AddPendingGlobalSymbol - Add a global to be processed and to
 204     // the global symbol lookup, use a zero index because the table
 205     // index will be determined later.
 206     void AddPendingGlobalSymbol(const GlobalValue *GV,
 207                                 bool AddToLookup = false);
 208
 209     // AddPendingExternalSymbol - Add the external to be processed
 210     // and to the external symbol lookup, use a zero index because
 211     // the symbol table index will be determined later.
 212     void AddPendingExternalSymbol(const char *External);
 213
 214     // AddToSymbolList - Update the symbol lookup and If the symbol is
 215     // private add it to PrivateSyms list, otherwise to SymbolList.
 216     void AddToSymbolList(ELFSym *GblSym);
 217
 218     // As we complete the ELF file, we need to update fields in the ELF header
 219     // (e.g. the location of the section table).  These members keep track of
 220     // the offset in ELFHeader of these various pieces to update and other
 221     // locations in the file.
 222     unsigned ELFHdr_e_shoff_Offset;     // e_shoff    in ELF header.
 223     unsigned ELFHdr_e_shstrndx_Offset;  // e_shstrndx in ELF header.
 224     unsigned ELFHdr_e_shnum_Offset;     // e_shnum    in ELF header.
 225
 226   private:
 227     void EmitGlobal(const GlobalValue *GV);
 228     void EmitGlobalConstant(const Constant *C, ELFSection &GblS);
 229     void EmitGlobalConstantStruct(const ConstantStruct *CVS,
 230                                   ELFSection &GblS);
 231     void EmitGlobalConstantLargeInt(const ConstantInt *CI, ELFSection &S);
 232     void EmitGlobalDataRelocation(const GlobalValue *GV, unsigned Size,
 233                                   ELFSection &GblS, int64_t Offset = 0);
 234     bool EmitSpecialLLVMGlobal(const GlobalVariable *GV);
 235     void EmitXXStructorList(Constant *List, ELFSection &Xtor);
 236     void EmitRelocations();
 237     void EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel, bool HasRelA);
 238     void EmitSectionHeader(BinaryObject &SHdrTab, const ELFSection &SHdr);
 239     void EmitSectionTableStringTable();
 240     void EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym);
 241     void EmitSymbolTable();
 242     void EmitStringTable(const std::string &ModuleName);
 243     void OutputSectionsAndSectionTable();
 244     void RelocateField(BinaryObject &BO, uint32_t Offset, int64_t Value,
 245                        unsigned Size);
 246     unsigned SortSymbols();
 247     CstExprResTy ResolveConstantExpr(const Constant *CV);
 248   };
 249 }
 250
 251 #endif