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/System/DataTypes.h"
  26
  27 namespace llvm {
  28   class GlobalValue;
  29
  30   // Identification Indexes
  31   enum {
  32     EI_MAG0 = 0,
  33     EI_MAG1 = 1,
  34     EI_MAG2 = 2,
  35     EI_MAG3 = 3
  36   };
  37
  38   // File types
  39   enum {
  40     ET_NONE   = 0,      // No file type
  41     ET_REL    = 1,      // Relocatable file
  42     ET_EXEC   = 2,      // Executable file
  43     ET_DYN    = 3,      // Shared object file
  44     ET_CORE   = 4,      // Core file
  45     ET_LOPROC = 0xff00, // Beginning of processor-specific codes
  46     ET_HIPROC = 0xffff  // Processor-specific
  47   };
  48
  49   // Versioning
  50   enum {
  51     EV_NONE = 0,
  52     EV_CURRENT = 1
  53   };
  54
  55   /// ELFSym - This struct contains information about each symbol that is
  56   /// added to logical symbol table for the module.  This is eventually
  57   /// turned into a real symbol table in the file.
  58   struct ELFSym {
  59
  60     // ELF symbols are related to llvm ones by being one of the two llvm
  61     // types, for the other ones (section, file, func) a null pointer is
  62     // assumed by default.
  63     union {
  64       const GlobalValue *GV;  // If this is a pointer to a GV
  65       const char *Ext;        // If this is a pointer to a named symbol
  66     } Source;
  67
  68     // Describes from which source type this ELF symbol comes from,
  69     // they can be GlobalValue, ExternalSymbol or neither.
  70     enum {
  71       isGV,      // The Source.GV field is valid.
  72       isExtSym,  // The Source.ExtSym field is valid.
  73       isOther    // Not a GlobalValue or External Symbol
  74     };
  75     unsigned SourceType;
  76
  77     bool isGlobalValue() const { return SourceType == isGV; }
  78     bool isExternalSym() const { return SourceType == isExtSym; }
  79
  80     // getGlobalValue - If this is a global value which originated the
  81     // elf symbol, return a reference to it.
  82     const GlobalValue *getGlobalValue() const {
  83       assert(SourceType == isGV && "This is not a global value");
  84       return Source.GV;
  85     }
  86
  87     // getExternalSym - If this is an external symbol which originated the
  88     // elf symbol, return a reference to it.
  89     const char *getExternalSymbol() const {
  90       assert(SourceType == isExtSym && "This is not an external symbol");
  91       return Source.Ext;
  92     }
  93
  94     // getGV - From a global value return a elf symbol to represent it
  95     static ELFSym *getGV(const GlobalValue *GV, unsigned Bind,
  96                          unsigned Type, unsigned Visibility) {
  97       ELFSym *Sym = new ELFSym();
  98       Sym->Source.GV = GV;
  99       Sym->setBind(Bind);
 100       Sym->setType(Type);
 101       Sym->setVisibility(Visibility);
 102       Sym->SourceType = isGV;
 103       return Sym;
 104     }
 105
 106     // getExtSym - Create and return an elf symbol to represent an
 107     // external symbol
 108     static ELFSym *getExtSym(const char *Ext) {
 109       ELFSym *Sym = new ELFSym();
 110       Sym->Source.Ext = Ext;
 111       Sym->setBind(STB_GLOBAL);
 112       Sym->setType(STT_NOTYPE);
 113       Sym->setVisibility(STV_DEFAULT);
 114       Sym->SourceType = isExtSym;
 115       return Sym;
 116     }
 117
 118     // getSectionSym - Returns a elf symbol to represent an elf section
 119     static ELFSym *getSectionSym() {
 120       ELFSym *Sym = new ELFSym();
 121       Sym->setBind(STB_LOCAL);
 122       Sym->setType(STT_SECTION);
 123       Sym->setVisibility(STV_DEFAULT);
 124       Sym->SourceType = isOther;
 125       return Sym;
 126     }
 127
 128     // getFileSym - Returns a elf symbol to represent the module identifier
 129     static ELFSym *getFileSym() {
 130       ELFSym *Sym = new ELFSym();
 131       Sym->setBind(STB_LOCAL);
 132       Sym->setType(STT_FILE);
 133       Sym->setVisibility(STV_DEFAULT);
 134       Sym->SectionIdx = 0xfff1;  // ELFSection::SHN_ABS;
 135       Sym->SourceType = isOther;
 136       return Sym;
 137     }
 138
 139     // getUndefGV - Returns a STT_NOTYPE symbol
 140     static ELFSym *getUndefGV(const GlobalValue *GV, unsigned Bind) {
 141       ELFSym *Sym = new ELFSym();
 142       Sym->Source.GV = GV;
 143       Sym->setBind(Bind);
 144       Sym->setType(STT_NOTYPE);
 145       Sym->setVisibility(STV_DEFAULT);
 146       Sym->SectionIdx = 0;  //ELFSection::SHN_UNDEF;
 147       Sym->SourceType = isGV;
 148       return Sym;
 149     }
 150
 151     // ELF specific fields
 152     unsigned NameIdx;         // Index in .strtab of name, once emitted.
 153     uint64_t Value;
 154     unsigned Size;
 155     uint8_t Info;
 156     uint8_t Other;
 157     unsigned short SectionIdx;
 158
 159     // Symbol index into the Symbol table
 160     unsigned SymTabIdx;
 161
 162     enum {
 163       STB_LOCAL = 0,  // Local sym, not visible outside obj file containing def
 164       STB_GLOBAL = 1, // Global sym, visible to all object files being combined
 165       STB_WEAK = 2    // Weak symbol, like global but lower-precedence
 166     };
 167
 168     enum {
 169       STT_NOTYPE = 0,  // Symbol's type is not specified
 170       STT_OBJECT = 1,  // Symbol is a data object (variable, array, etc.)
 171       STT_FUNC = 2,    // Symbol is executable code (function, etc.)
 172       STT_SECTION = 3, // Symbol refers to a section
 173       STT_FILE = 4     // Local, absolute symbol that refers to a file
 174     };
 175
 176     enum {
 177       STV_DEFAULT = 0,  // Visibility is specified by binding type
 178       STV_INTERNAL = 1, // Defined by processor supplements
 179       STV_HIDDEN = 2,   // Not visible to other components
 180       STV_PROTECTED = 3 // Visible in other components but not preemptable
 181     };
 182
 183     ELFSym() : SourceType(isOther), NameIdx(0), Value(0),
 184                Size(0), Info(0), Other(STV_DEFAULT), SectionIdx(0),
 185                SymTabIdx(0) {}
 186
 187     unsigned getBind() const { return (Info >> 4) & 0xf; }
 188     unsigned getType() const { return Info & 0xf; }
 189     bool isLocalBind() const { return getBind() == STB_LOCAL; }
 190     bool isFileType() const { return getType() == STT_FILE; }
 191
 192     void setBind(unsigned X) {
 193       assert(X == (X & 0xF) && "Bind value out of range!");
 194       Info = (Info & 0x0F) | (X << 4);
 195     }
 196
 197     void setType(unsigned X) {
 198       assert(X == (X & 0xF) && "Type value out of range!");
 199       Info = (Info & 0xF0) | X;
 200     }
 201
 202     void setVisibility(unsigned V) {
 203       assert(V == (V & 0x3) && "Visibility value out of range!");
 204       Other = V;
 205     }
 206   };
 207
 208   /// ELFSection - This struct contains information about each section that is
 209   /// emitted to the file.  This is eventually turned into the section header
 210   /// table at the end of the file.
 211   class ELFSection : public BinaryObject {
 212     public:
 213     // ELF specific fields
 214     unsigned NameIdx;   // sh_name - .shstrtab idx of name, once emitted.
 215     unsigned Type;      // sh_type - Section contents & semantics
 216     unsigned Flags;     // sh_flags - Section flags.
 217     uint64_t Addr;      // sh_addr - The mem addr this section is in.
 218     unsigned Offset;    // sh_offset - Offset from the file start
 219     unsigned Size;      // sh_size - The section size.
 220     unsigned Link;      // sh_link - Section header table index link.
 221     unsigned Info;      // sh_info - Auxillary information.
 222     unsigned Align;     // sh_addralign - Alignment of section.
 223     unsigned EntSize;   // sh_entsize - Size of entries in the section e
 224
 225     // Section Header Flags
 226     enum {
 227       SHF_WRITE            = 1 << 0, // Writable
 228       SHF_ALLOC            = 1 << 1, // Mapped into the process addr space
 229       SHF_EXECINSTR        = 1 << 2, // Executable
 230       SHF_MERGE            = 1 << 4, // Might be merged if equal
 231       SHF_STRINGS          = 1 << 5, // Contains null-terminated strings
 232       SHF_INFO_LINK        = 1 << 6, // 'sh_info' contains SHT index
 233       SHF_LINK_ORDER       = 1 << 7, // Preserve order after combining
 234       SHF_OS_NONCONFORMING = 1 << 8, // nonstandard OS support required
 235       SHF_GROUP            = 1 << 9, // Section is a member of a group
 236       SHF_TLS              = 1 << 10 // Section holds thread-local data
 237     };
 238
 239     // Section Types
 240     enum {
 241       SHT_NULL     = 0,  // No associated section (inactive entry).
 242       SHT_PROGBITS = 1,  // Program-defined contents.
 243       SHT_SYMTAB   = 2,  // Symbol table.
 244       SHT_STRTAB   = 3,  // String table.
 245       SHT_RELA     = 4,  // Relocation entries; explicit addends.
 246       SHT_HASH     = 5,  // Symbol hash table.
 247       SHT_DYNAMIC  = 6,  // Information for dynamic linking.
 248       SHT_NOTE     = 7,  // Information about the file.
 249       SHT_NOBITS   = 8,  // Data occupies no space in the file.
 250       SHT_REL      = 9,  // Relocation entries; no explicit addends.
 251       SHT_SHLIB    = 10, // Reserved.
 252       SHT_DYNSYM   = 11, // Symbol table.
 253       SHT_LOPROC   = 0x70000000, // Lowest processor arch-specific type.
 254       SHT_HIPROC   = 0x7fffffff, // Highest processor arch-specific type.
 255       SHT_LOUSER   = 0x80000000, // Lowest type reserved for applications.
 256       SHT_HIUSER   = 0xffffffff  // Highest type reserved for applications.
 257     };
 258
 259     // Special section indices.
 260     enum {
 261       SHN_UNDEF     = 0,      // Undefined, missing, irrelevant
 262       SHN_LORESERVE = 0xff00, // Lowest reserved index
 263       SHN_LOPROC    = 0xff00, // Lowest processor-specific index
 264       SHN_HIPROC    = 0xff1f, // Highest processor-specific index
 265       SHN_ABS       = 0xfff1, // Symbol has absolute value; no relocation
 266       SHN_COMMON    = 0xfff2, // FORTRAN COMMON or C external global variables
 267       SHN_HIRESERVE = 0xffff  // Highest reserved index
 268     };
 269
 270     /// SectionIdx - The number of the section in the Section Table.
 271     unsigned short SectionIdx;
 272
 273     /// Sym - The symbol to represent this section if it has one.
 274     ELFSym *Sym;
 275
 276     /// getSymIndex - Returns the symbol table index of the symbol
 277     /// representing this section.
 278     unsigned getSymbolTableIndex() const {
 279       assert(Sym && "section not present in the symbol table");
 280       return Sym->SymTabIdx;
 281     }
 282
 283     ELFSection(const std::string &name, bool isLittleEndian, bool is64Bit)
 284       : BinaryObject(name, isLittleEndian, is64Bit), Type(0), Flags(0), Addr(0),
 285         Offset(0), Size(0), Link(0), Info(0), Align(0), EntSize(0), Sym(0) {}
 286   };
 287
 288   /// ELFRelocation - This class contains all the information necessary to
 289   /// to generate any 32-bit or 64-bit ELF relocation entry.
 290   class ELFRelocation {
 291     uint64_t r_offset;    // offset in the section of the object this applies to
 292     uint32_t r_symidx;    // symbol table index of the symbol to use
 293     uint32_t r_type;      // machine specific relocation type
 294     int64_t  r_add;       // explicit relocation addend
 295     bool     r_rela;      // if true then the addend is part of the entry
 296                           // otherwise the addend is at the location specified
 297                           // by r_offset
 298   public:
 299     uint64_t getInfo(bool is64Bit) const {
 300       if (is64Bit)
 301         return ((uint64_t)r_symidx << 32) + ((uint64_t)r_type & 0xFFFFFFFFL);
 302       else
 303         return (r_symidx << 8)  + (r_type & 0xFFL);
 304     }
 305
 306     uint64_t getOffset() const { return r_offset; }
 307     int64_t getAddend() const { return r_add; }
 308
 309     ELFRelocation(uint64_t off, uint32_t sym, uint32_t type,
 310                   bool rela = true, int64_t addend = 0) :
 311       r_offset(off), r_symidx(sym), r_type(type),
 312       r_add(addend), r_rela(rela) {}
 313   };
 314
 315 } // end namespace llvm
 316
 317 #endif