lib/CodeGen/ELF.h

   1 //===-- lib/CodeGen/ELF.h - ELF constants and data structures ---*- 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 header contains common, non-processor-specific data structures and
  11 // constants for the ELF file format.
  12 //
  13 // The details of the ELF32 bits in this file are largely based on the Tool
  14 // Interface Standard (TIS) Executable and Linking Format (ELF) Specification
  15 // Version 1.2, May 1995. The ELF64 is based on HP/Intel definition of the
  16 // ELF-64 object file format document, Version 1.5 Draft 2 May 27, 1998
  17 //
  18 //===----------------------------------------------------------------------===//
  19
  20 #ifndef CODEGEN_ELF_H
  21 #define CODEGEN_ELF_H
  22
  23 #include "llvm/CodeGen/BinaryObject.h"
  24 #include "llvm/CodeGen/MachineRelocation.h"
  25 #include "llvm/Support/ELF.h"
  26 #include "llvm/Support/DataTypes.h"
  27
  28 namespace llvm {
  29   class GlobalValue;
  30
  31   /// ELFSym - This struct contains information about each symbol that is
  32   /// added to logical symbol table for the module.  This is eventually
  33   /// turned into a real symbol table in the file.
  34   struct ELFSym {
  35
  36     // ELF symbols are related to llvm ones by being one of the two llvm
  37     // types, for the other ones (section, file, func) a null pointer is
  38     // assumed by default.
  39     union {
  40       const GlobalValue *GV;  // If this is a pointer to a GV
  41       const char *Ext;        // If this is a pointer to a named symbol
  42     } Source;
  43
  44     // Describes from which source type this ELF symbol comes from,
  45     // they can be GlobalValue, ExternalSymbol or neither.
  46     enum {
  47       isGV,      // The Source.GV field is valid.
  48       isExtSym,  // The Source.ExtSym field is valid.
  49       isOther    // Not a GlobalValue or External Symbol
  50     };
  51     unsigned SourceType;
  52
  53     bool isGlobalValue() const { return SourceType == isGV; }
  54     bool isExternalSym() const { return SourceType == isExtSym; }
  55
  56     // getGlobalValue - If this is a global value which originated the
  57     // elf symbol, return a reference to it.
  58     const GlobalValue *getGlobalValue() const {
  59       assert(SourceType == isGV && "This is not a global value");
  60       return Source.GV;
  61     }
  62
  63     // getExternalSym - If this is an external symbol which originated the
  64     // elf symbol, return a reference to it.
  65     const char *getExternalSymbol() const {
  66       assert(SourceType == isExtSym && "This is not an external symbol");
  67       return Source.Ext;
  68     }
  69
  70     // getGV - From a global value return a elf symbol to represent it
  71     static ELFSym *getGV(const GlobalValue *GV, unsigned Bind,
  72                          unsigned Type, unsigned Visibility) {
  73       ELFSym *Sym = new ELFSym();
  74       Sym->Source.GV = GV;
  75       Sym->setBind(Bind);
  76       Sym->setType(Type);
  77       Sym->setVisibility(Visibility);
  78       Sym->SourceType = isGV;
  79       return Sym;
  80     }
  81
  82     // getExtSym - Create and return an elf symbol to represent an
  83     // external symbol
  84     static ELFSym *getExtSym(const char *Ext) {
  85       ELFSym *Sym = new ELFSym();
  86       Sym->Source.Ext = Ext;
  87       Sym->setBind(ELF::STB_GLOBAL);
  88       Sym->setType(ELF::STT_NOTYPE);
  89       Sym->setVisibility(ELF::STV_DEFAULT);
  90       Sym->SourceType = isExtSym;
  91       return Sym;
  92     }
  93
  94     // getSectionSym - Returns a elf symbol to represent an elf section
  95     static ELFSym *getSectionSym() {
  96       ELFSym *Sym = new ELFSym();
  97       Sym->setBind(ELF::STB_LOCAL);
  98       Sym->setType(ELF::STT_SECTION);
  99       Sym->setVisibility(ELF::STV_DEFAULT);
 100       Sym->SourceType = isOther;
 101       return Sym;
 102     }
 103
 104     // getFileSym - Returns a elf symbol to represent the module identifier
 105     static ELFSym *getFileSym() {
 106       ELFSym *Sym = new ELFSym();
 107       Sym->setBind(ELF::STB_LOCAL);
 108       Sym->setType(ELF::STT_FILE);
 109       Sym->setVisibility(ELF::STV_DEFAULT);
 110       Sym->SectionIdx = 0xfff1;  // ELFSection::SHN_ABS;
 111       Sym->SourceType = isOther;
 112       return Sym;
 113     }
 114
 115     // getUndefGV - Returns a STT_NOTYPE symbol
 116     static ELFSym *getUndefGV(const GlobalValue *GV, unsigned Bind) {
 117       ELFSym *Sym = new ELFSym();
 118       Sym->Source.GV = GV;
 119       Sym->setBind(Bind);
 120       Sym->setType(ELF::STT_NOTYPE);
 121       Sym->setVisibility(ELF::STV_DEFAULT);
 122       Sym->SectionIdx = 0;  //ELFSection::SHN_UNDEF;
 123       Sym->SourceType = isGV;
 124       return Sym;
 125     }
 126
 127     // ELF specific fields
 128     unsigned NameIdx;         // Index in .strtab of name, once emitted.
 129     uint64_t Value;
 130     unsigned Size;
 131     uint8_t Info;
 132     uint8_t Other;
 133     unsigned short SectionIdx;
 134
 135     // Symbol index into the Symbol table
 136     unsigned SymTabIdx;
 137
 138     ELFSym() : SourceType(isOther), NameIdx(0), Value(0),
 139                Size(0), Info(0), Other(ELF::STV_DEFAULT), SectionIdx(0),
 140                SymTabIdx(0) {}
 141
 142     unsigned getBind() const { return (Info >> 4) & 0xf; }
 143     unsigned getType() const { return Info & 0xf; }
 144     bool isLocalBind() const { return getBind() == ELF::STB_LOCAL; }
 145     bool isFileType() const { return getType() == ELF::STT_FILE; }
 146
 147     void setBind(unsigned X) {
 148       assert(X == (X & 0xF) && "Bind value out of range!");
 149       Info = (Info & 0x0F) | (X << 4);
 150     }
 151
 152     void setType(unsigned X) {
 153       assert(X == (X & 0xF) && "Type value out of range!");
 154       Info = (Info & 0xF0) | X;
 155     }
 156
 157     void setVisibility(unsigned V) {
 158       assert(V == (V & 0x3) && "Visibility value out of range!");
 159       Other = V;
 160     }
 161   };
 162
 163   /// ELFSection - This struct contains information about each section that is
 164   /// emitted to the file.  This is eventually turned into the section header
 165   /// table at the end of the file.
 166   class ELFSection : public BinaryObject {
 167     public:
 168     // ELF specific fields
 169     unsigned NameIdx;   // sh_name - .shstrtab idx of name, once emitted.
 170     unsigned Type;      // sh_type - Section contents & semantics
 171     unsigned Flags;     // sh_flags - Section flags.
 172     uint64_t Addr;      // sh_addr - The mem addr this section is in.
 173     unsigned Offset;    // sh_offset - Offset from the file start
 174     unsigned Size;      // sh_size - The section size.
 175     unsigned Link;      // sh_link - Section header table index link.
 176     unsigned Info;      // sh_info - Auxiliary information.
 177     unsigned Align;     // sh_addralign - Alignment of section.
 178     unsigned EntSize;   // sh_entsize - Size of entries in the section e
 179
 180     /// SectionIdx - The number of the section in the Section Table.
 181     unsigned short SectionIdx;
 182
 183     /// Sym - The symbol to represent this section if it has one.
 184     ELFSym *Sym;
 185
 186     /// getSymIndex - Returns the symbol table index of the symbol
 187     /// representing this section.
 188     unsigned getSymbolTableIndex() const {
 189       assert(Sym && "section not present in the symbol table");
 190       return Sym->SymTabIdx;
 191     }
 192
 193     ELFSection(const std::string &name, bool isLittleEndian, bool is64Bit)
 194       : BinaryObject(name, isLittleEndian, is64Bit), Type(0), Flags(0), Addr(0),
 195         Offset(0), Size(0), Link(0), Info(0), Align(0), EntSize(0), Sym(0) {}
 196   };
 197
 198   /// ELFRelocation - This class contains all the information necessary to
 199   /// to generate any 32-bit or 64-bit ELF relocation entry.
 200   class ELFRelocation {
 201     uint64_t r_offset;    // offset in the section of the object this applies to
 202     uint32_t r_symidx;    // symbol table index of the symbol to use
 203     uint32_t r_type;      // machine specific relocation type
 204     int64_t  r_add;       // explicit relocation addend
 205     bool     r_rela;      // if true then the addend is part of the entry
 206                           // otherwise the addend is at the location specified
 207                           // by r_offset
 208   public:
 209     uint64_t getInfo(bool is64Bit) const {
 210       if (is64Bit)
 211         return ((uint64_t)r_symidx << 32) + ((uint64_t)r_type & 0xFFFFFFFFL);
 212       else
 213         return (r_symidx << 8)  + (r_type & 0xFFL);
 214     }
 215
 216     uint64_t getOffset() const { return r_offset; }
 217     int64_t getAddend() const { return r_add; }
 218
 219     ELFRelocation(uint64_t off, uint32_t sym, uint32_t type,
 220                   bool rela = true, int64_t addend = 0) :
 221       r_offset(off), r_symidx(sym), r_type(type),
 222       r_add(addend), r_rela(rela) {}
 223   };
 224
 225 } // end namespace llvm
 226
 227 #endif