lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp

   1 //===-- RuntimeDyldMachO.cpp - Run-time dynamic linker for MC-JIT -*- 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 // Implementation of the MC-JIT runtime dynamic linker.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #define DEBUG_TYPE "dyld"
  15 #include "llvm/ADT/OwningPtr.h"
  16 #include "llvm/ADT/StringRef.h"
  17 #include "llvm/ADT/STLExtras.h"
  18 #include "RuntimeDyldMachO.h"
  19 using namespace llvm;
  20 using namespace llvm::object;
  21
  22 namespace llvm {
  23
  24 void RuntimeDyldMachO::resolveRelocation(uint8_t *LocalAddress,
  25                                          uint64_t FinalAddress,
  26                                          uint64_t Value,
  27                                          uint32_t Type,
  28                                          int64_t Addend) {
  29   bool isPCRel = (Type >> 24) & 1;
  30   unsigned MachoType = (Type >> 28) & 0xf;
  31   unsigned Size = 1 << ((Type >> 25) & 3);
  32
  33   DEBUG(dbgs() << "resolveRelocation LocalAddress: "
  34         << format("%p", LocalAddress)
  35         << " FinalAddress: " << format("%p", FinalAddress)
  36         << " Value: " << format("%p", Value)
  37         << " Addend: " << Addend
  38         << " isPCRel: " << isPCRel
  39         << " MachoType: " << MachoType
  40         << " Size: " << Size
  41         << "\n");
  42
  43   // This just dispatches to the proper target specific routine.
  44   switch (Arch) {
  45   default: llvm_unreachable("Unsupported CPU type!");
  46   case Triple::x86_64:
  47     resolveX86_64Relocation(LocalAddress,
  48                             FinalAddress,
  49                             (uintptr_t)Value,
  50                             isPCRel,
  51                             MachoType,
  52                             Size,
  53                             Addend);
  54     break;
  55   case Triple::x86:
  56     resolveI386Relocation(LocalAddress,
  57                           FinalAddress,
  58                           (uintptr_t)Value,
  59                           isPCRel,
  60                           Type,
  61                           Size,
  62                           Addend);
  63     break;
  64   case Triple::arm:    // Fall through.
  65   case Triple::thumb:
  66     resolveARMRelocation(LocalAddress,
  67                          FinalAddress,
  68                          (uintptr_t)Value,
  69                          isPCRel,
  70                          MachoType,
  71                          Size,
  72                          Addend);
  73     break;
  74   }
  75 }
  76
  77 bool RuntimeDyldMachO::resolveI386Relocation(uint8_t *LocalAddress,
  78                                              uint64_t FinalAddress,
  79                                              uint64_t Value,
  80                                              bool isPCRel,
  81                                              unsigned Type,
  82                                              unsigned Size,
  83                                              int64_t Addend) {
  84   if (isPCRel)
  85     Value -= FinalAddress + 4; // see resolveX86_64Relocation
  86
  87   switch (Type) {
  88   default:
  89     llvm_unreachable("Invalid relocation type!");
  90   case macho::RIT_Vanilla: {
  91     uint8_t *p = LocalAddress;
  92     uint64_t ValueToWrite = Value + Addend;
  93     for (unsigned i = 0; i < Size; ++i) {
  94       *p++ = (uint8_t)(ValueToWrite & 0xff);
  95       ValueToWrite >>= 8;
  96     }
  97   }
  98   case macho::RIT_Difference:
  99   case macho::RIT_Generic_LocalDifference:
 100   case macho::RIT_Generic_PreboundLazyPointer:
 101     return Error("Relocation type not implemented yet!");
 102   }
 103 }
 104
 105 bool RuntimeDyldMachO::resolveX86_64Relocation(uint8_t *LocalAddress,
 106                                                uint64_t FinalAddress,
 107                                                uint64_t Value,
 108                                                bool isPCRel,
 109                                                unsigned Type,
 110                                                unsigned Size,
 111                                                int64_t Addend) {
 112   // If the relocation is PC-relative, the value to be encoded is the
 113   // pointer difference.
 114   if (isPCRel)
 115     // FIXME: It seems this value needs to be adjusted by 4 for an effective PC
 116     // address. Is that expected? Only for branches, perhaps?
 117     Value -= FinalAddress + 4;
 118
 119   switch(Type) {
 120   default:
 121     llvm_unreachable("Invalid relocation type!");
 122   case macho::RIT_X86_64_Signed1:
 123   case macho::RIT_X86_64_Signed2:
 124   case macho::RIT_X86_64_Signed4:
 125   case macho::RIT_X86_64_Signed:
 126   case macho::RIT_X86_64_Unsigned:
 127   case macho::RIT_X86_64_Branch: {
 128     Value += Addend;
 129     // Mask in the target value a byte at a time (we don't have an alignment
 130     // guarantee for the target address, so this is safest).
 131     uint8_t *p = (uint8_t*)LocalAddress;
 132     for (unsigned i = 0; i < Size; ++i) {
 133       *p++ = (uint8_t)Value;
 134       Value >>= 8;
 135     }
 136     return false;
 137   }
 138   case macho::RIT_X86_64_GOTLoad:
 139   case macho::RIT_X86_64_GOT:
 140   case macho::RIT_X86_64_Subtractor:
 141   case macho::RIT_X86_64_TLV:
 142     return Error("Relocation type not implemented yet!");
 143   }
 144 }
 145
 146 bool RuntimeDyldMachO::resolveARMRelocation(uint8_t *LocalAddress,
 147                                             uint64_t FinalAddress,
 148                                             uint64_t Value,
 149                                             bool isPCRel,
 150                                             unsigned Type,
 151                                             unsigned Size,
 152                                             int64_t Addend) {
 153   // If the relocation is PC-relative, the value to be encoded is the
 154   // pointer difference.
 155   if (isPCRel) {
 156     Value -= FinalAddress;
 157     // ARM PCRel relocations have an effective-PC offset of two instructions
 158     // (four bytes in Thumb mode, 8 bytes in ARM mode).
 159     // FIXME: For now, assume ARM mode.
 160     Value -= 8;
 161   }
 162
 163   switch(Type) {
 164   default:
 165     llvm_unreachable("Invalid relocation type!");
 166   case macho::RIT_Vanilla: {
 167     // Mask in the target value a byte at a time (we don't have an alignment
 168     // guarantee for the target address, so this is safest).
 169     uint8_t *p = (uint8_t*)LocalAddress;
 170     for (unsigned i = 0; i < Size; ++i) {
 171       *p++ = (uint8_t)Value;
 172       Value >>= 8;
 173     }
 174     break;
 175   }
 176   case macho::RIT_ARM_Branch24Bit: {
 177     // Mask the value into the target address. We know instructions are
 178     // 32-bit aligned, so we can do it all at once.
 179     uint32_t *p = (uint32_t*)LocalAddress;
 180     // The low two bits of the value are not encoded.
 181     Value >>= 2;
 182     // Mask the value to 24 bits.
 183     Value &= 0xffffff;
 184     // FIXME: If the destination is a Thumb function (and the instruction
 185     // is a non-predicated BL instruction), we need to change it to a BLX
 186     // instruction instead.
 187
 188     // Insert the value into the instruction.
 189     *p = (*p & ~0xffffff) | Value;
 190     break;
 191   }
 192   case macho::RIT_ARM_ThumbBranch22Bit:
 193   case macho::RIT_ARM_ThumbBranch32Bit:
 194   case macho::RIT_ARM_Half:
 195   case macho::RIT_ARM_HalfDifference:
 196   case macho::RIT_Pair:
 197   case macho::RIT_Difference:
 198   case macho::RIT_ARM_LocalDifference:
 199   case macho::RIT_ARM_PreboundLazyPointer:
 200     return Error("Relocation type not implemented yet!");
 201   }
 202   return false;
 203 }
 204
 205 void RuntimeDyldMachO::processRelocationRef(const ObjRelocationInfo &Rel,
 206                                             ObjectImage &Obj,
 207                                             ObjSectionToIDMap &ObjSectionToID,
 208                                             const SymbolTableMap &Symbols,
 209                                             StubMap &Stubs) {
 210
 211   uint32_t RelType = (uint32_t) (Rel.Type & 0xffffffffL);
 212   RelocationValueRef Value;
 213   SectionEntry &Section = Sections[Rel.SectionID];
 214   uint8_t *Target = Section.Address + Rel.Offset;
 215
 216   bool isExtern = (RelType >> 27) & 1;
 217   if (isExtern) {
 218     // Obtain the symbol name which is referenced in the relocation
 219     StringRef TargetName;
 220     const SymbolRef &Symbol = Rel.Symbol;
 221     Symbol.getName(TargetName);
 222     // First search for the symbol in the local symbol table
 223     SymbolTableMap::const_iterator lsi = Symbols.find(TargetName.data());
 224     if (lsi != Symbols.end()) {
 225       Value.SectionID = lsi->second.first;
 226       Value.Addend = lsi->second.second;
 227     } else {
 228       // Search for the symbol in the global symbol table
 229       SymbolTableMap::const_iterator gsi = GlobalSymbolTable.find(TargetName.data());
 230       if (gsi != GlobalSymbolTable.end()) {
 231         Value.SectionID = gsi->second.first;
 232         Value.Addend = gsi->second.second;
 233       } else
 234         Value.SymbolName = TargetName.data();
 235     }
 236   } else {
 237     error_code err;
 238     uint8_t sectionIndex = static_cast<uint8_t>(RelType & 0xFF);
 239     section_iterator si = Obj.begin_sections(),
 240                      se = Obj.end_sections();
 241     for (uint8_t i = 1; i < sectionIndex; i++) {
 242       error_code err;
 243       si.increment(err);
 244       if (si == se)
 245         break;
 246     }
 247     assert(si != se && "No section containing relocation!");
 248     Value.SectionID = findOrEmitSection(Obj, *si, true, ObjSectionToID);
 249     Value.Addend = *(const intptr_t *)Target;
 250     if (Value.Addend) {
 251       // The MachO addend is an offset from the current section.  We need it
 252       // to be an offset from the destination section
 253       Value.Addend += Section.ObjAddress - Sections[Value.SectionID].ObjAddress;
 254     }
 255   }
 256
 257   if (Arch == Triple::arm && RelType == macho::RIT_ARM_Branch24Bit) {
 258     // This is an ARM branch relocation, need to use a stub function.
 259
 260     //  Look up for existing stub.
 261     StubMap::const_iterator i = Stubs.find(Value);
 262     if (i != Stubs.end())
 263       resolveRelocation(Target, (uint64_t)Target,
 264                         (uint64_t)Section.Address + i->second,
 265                         RelType, 0);
 266     else {
 267       // Create a new stub function.
 268       Stubs[Value] = Section.StubOffset;
 269       uint8_t *StubTargetAddr = createStubFunction(Section.Address +
 270                                                    Section.StubOffset);
 271       RelocationEntry RE(Rel.SectionID, StubTargetAddr - Section.Address,
 272                          macho::RIT_Vanilla, Value.Addend);
 273       if (Value.SymbolName)
 274         addRelocationForSymbol(RE, Value.SymbolName);
 275       else
 276         addRelocationForSection(RE, Value.SectionID);
 277       resolveRelocation(Target, (uint64_t)Target,
 278                         (uint64_t)Section.Address + Section.StubOffset,
 279                         RelType, 0);
 280       Section.StubOffset += getMaxStubSize();
 281     }
 282   } else {
 283     RelocationEntry RE(Rel.SectionID, Rel.Offset, RelType, Value.Addend);
 284     if (Value.SymbolName)
 285       addRelocationForSymbol(RE, Value.SymbolName);
 286     else
 287       addRelocationForSection(RE, Value.SectionID);
 288   }
 289 }
 290
 291
 292 bool RuntimeDyldMachO::isCompatibleFormat(
 293         const MemoryBuffer *InputBuffer) const {
 294   StringRef Magic = InputBuffer->getBuffer().slice(0, 4);
 295   if (Magic == "\xFE\xED\xFA\xCE") return true;
 296   if (Magic == "\xCE\xFA\xED\xFE") return true;
 297   if (Magic == "\xFE\xED\xFA\xCF") return true;
 298   if (Magic == "\xCF\xFA\xED\xFE") return true;
 299   return false;
 300 }
 301
 302 } // end namespace llvm