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