lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldCOFFX86_64.h

   1 //===-- RuntimeDyldCOFFX86_64.h --- COFF/X86_64 specific code ---*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // COFF x86_x64 support for MC-JIT runtime dynamic linker.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #ifndef LLVM_LIB_EXECUTIONENGINE_RUNTIMEDYLD_TARGETS_RUNTIMEDYLDCOFF86_64_H
  14 #define LLVM_LIB_EXECUTIONENGINE_RUNTIMEDYLD_TARGETS_RUNTIMEDYLDCOFF86_64_H
  15
  16 #include "../RuntimeDyldCOFF.h"
  17 #include "llvm/BinaryFormat/COFF.h"
  18 #include "llvm/Object/COFF.h"
  19
  20 #define DEBUG_TYPE "dyld"
  21
  22 namespace llvm {
  23
  24 class RuntimeDyldCOFFX86_64 : public RuntimeDyldCOFF {
  25
  26 private:
  27   // When a module is loaded we save the SectionID of the unwind
  28   // sections in a table until we receive a request to register all
  29   // unregisteredEH frame sections with the memory manager.
  30   SmallVector<SID, 2> UnregisteredEHFrameSections;
  31   SmallVector<SID, 2> RegisteredEHFrameSections;
  32   uint64_t ImageBase;
  33
  34   // Fake an __ImageBase pointer by returning the section with the lowest adress
  35   uint64_t getImageBase() {
  36     if (!ImageBase) {
  37       ImageBase = std::numeric_limits<uint64_t>::max();
  38       for (const SectionEntry &Section : Sections)
  39         // The Sections list may contain sections that weren't loaded for
  40         // whatever reason: they may be debug sections, and ProcessAllSections
  41         // is false, or they may be sections that contain 0 bytes. If the
  42         // section isn't loaded, the load address will be 0, and it should not
  43         // be included in the ImageBase calculation.
  44         if (Section.getLoadAddress() != 0)
  45           ImageBase = std::min(ImageBase, Section.getLoadAddress());
  46     }
  47     return ImageBase;
  48   }
  49
  50   void write32BitOffset(uint8_t *Target, int64_t Addend, uint64_t Delta) {
  51     uint64_t Result = Addend + Delta;
  52     assert(Result <= UINT32_MAX && "Relocation overflow");
  53     writeBytesUnaligned(Result, Target, 4);
  54   }
  55
  56 public:
  57   RuntimeDyldCOFFX86_64(RuntimeDyld::MemoryManager &MM,
  58                         JITSymbolResolver &Resolver)
  59     : RuntimeDyldCOFF(MM, Resolver), ImageBase(0) {}
  60
  61   unsigned getStubAlignment() override { return 1; }
  62
  63   // 2-byte jmp instruction + 32-bit relative address + 64-bit absolute jump
  64   unsigned getMaxStubSize() const override { return 14; }
  65
  66   // The target location for the relocation is described by RE.SectionID and
  67   // RE.Offset.  RE.SectionID can be used to find the SectionEntry.  Each
  68   // SectionEntry has three members describing its location.
  69   // SectionEntry::Address is the address at which the section has been loaded
  70   // into memory in the current (host) process.  SectionEntry::LoadAddress is
  71   // the address that the section will have in the target process.
  72   // SectionEntry::ObjAddress is the address of the bits for this section in the
  73   // original emitted object image (also in the current address space).
  74   //
  75   // Relocations will be applied as if the section were loaded at
  76   // SectionEntry::LoadAddress, but they will be applied at an address based
  77   // on SectionEntry::Address.  SectionEntry::ObjAddress will be used to refer
  78   // to Target memory contents if they are required for value calculations.
  79   //
  80   // The Value parameter here is the load address of the symbol for the
  81   // relocation to be applied.  For relocations which refer to symbols in the
  82   // current object Value will be the LoadAddress of the section in which
  83   // the symbol resides (RE.Addend provides additional information about the
  84   // symbol location).  For external symbols, Value will be the address of the
  85   // symbol in the target address space.
  86   void resolveRelocation(const RelocationEntry &RE, uint64_t Value) override {
  87     const SectionEntry &Section = Sections[RE.SectionID];
  88     uint8_t *Target = Section.getAddressWithOffset(RE.Offset);
  89
  90     switch (RE.RelType) {
  91
  92     case COFF::IMAGE_REL_AMD64_REL32:
  93     case COFF::IMAGE_REL_AMD64_REL32_1:
  94     case COFF::IMAGE_REL_AMD64_REL32_2:
  95     case COFF::IMAGE_REL_AMD64_REL32_3:
  96     case COFF::IMAGE_REL_AMD64_REL32_4:
  97     case COFF::IMAGE_REL_AMD64_REL32_5: {
  98       uint64_t FinalAddress = Section.getLoadAddressWithOffset(RE.Offset);
  99       // Delta is the distance from the start of the reloc to the end of the
 100       // instruction with the reloc.
 101       uint64_t Delta = 4 + (RE.RelType - COFF::IMAGE_REL_AMD64_REL32);
 102       Value -= FinalAddress + Delta;
 103       uint64_t Result = Value + RE.Addend;
 104       assert(((int64_t)Result <= INT32_MAX) && "Relocation overflow");
 105       assert(((int64_t)Result >= INT32_MIN) && "Relocation underflow");
 106       writeBytesUnaligned(Result, Target, 4);
 107       break;
 108     }
 109
 110     case COFF::IMAGE_REL_AMD64_ADDR32NB: {
 111       // ADDR32NB requires an offset less than 2GB from 'ImageBase'.
 112       // The MemoryManager can make sure this is always true by forcing the
 113       // memory layout to be: CodeSection < ReadOnlySection < ReadWriteSection.
 114       const uint64_t ImageBase = getImageBase();
 115       if (Value < ImageBase || ((Value - ImageBase) > UINT32_MAX)) {
 116         llvm::errs() << "IMAGE_REL_AMD64_ADDR32NB relocation requires an"
 117                      << "ordered section layout.\n";
 118         write32BitOffset(Target, 0, 0);
 119       } else {
 120         write32BitOffset(Target, RE.Addend, Value - ImageBase);
 121       }
 122       break;
 123     }
 124
 125     case COFF::IMAGE_REL_AMD64_ADDR64: {
 126       writeBytesUnaligned(Value + RE.Addend, Target, 8);
 127       break;
 128     }
 129
 130     case COFF::IMAGE_REL_AMD64_SECREL: {
 131       assert(static_cast<int64_t>(RE.Addend) <= INT32_MAX && "Relocation overflow");
 132       assert(static_cast<int64_t>(RE.Addend) >= INT32_MIN && "Relocation underflow");
 133       writeBytesUnaligned(RE.Addend, Target, 4);
 134       break;
 135     }
 136
 137     default:
 138       llvm_unreachable("Relocation type not implemented yet!");
 139       break;
 140     }
 141   }
 142
 143   std::tuple<uint64_t, uint64_t, uint64_t>
 144   generateRelocationStub(unsigned SectionID, StringRef TargetName,
 145                          uint64_t Offset, uint64_t RelType, uint64_t Addend,
 146                          StubMap &Stubs) {
 147     uintptr_t StubOffset;
 148     SectionEntry &Section = Sections[SectionID];
 149
 150     RelocationValueRef OriginalRelValueRef;
 151     OriginalRelValueRef.SectionID = SectionID;
 152     OriginalRelValueRef.Offset = Offset;
 153     OriginalRelValueRef.Addend = Addend;
 154     OriginalRelValueRef.SymbolName = TargetName.data();
 155
 156     auto Stub = Stubs.find(OriginalRelValueRef);
 157     if (Stub == Stubs.end()) {
 158       LLVM_DEBUG(dbgs() << " Create a new stub function for "
 159                         << TargetName.data() << "\n");
 160
 161       StubOffset = Section.getStubOffset();
 162       Stubs[OriginalRelValueRef] = StubOffset;
 163       createStubFunction(Section.getAddressWithOffset(StubOffset));
 164       Section.advanceStubOffset(getMaxStubSize());
 165     } else {
 166       LLVM_DEBUG(dbgs() << " Stub function found for " << TargetName.data()
 167                         << "\n");
 168       StubOffset = Stub->second;
 169     }
 170
 171     // FIXME: If RelType == COFF::IMAGE_REL_AMD64_ADDR32NB we should be able
 172     // to ignore the __ImageBase requirement and just forward to the stub
 173     // directly as an offset of this section:
 174     // write32BitOffset(Section.getAddressWithOffset(Offset), 0, StubOffset);
 175     // .xdata exception handler's aren't having this though.
 176
 177     // Resolve original relocation to stub function.
 178     const RelocationEntry RE(SectionID, Offset, RelType, Addend);
 179     resolveRelocation(RE, Section.getLoadAddressWithOffset(StubOffset));
 180
 181     // adjust relocation info so resolution writes to the stub function
 182     Addend = 0;
 183     Offset = StubOffset + 6;
 184     RelType = COFF::IMAGE_REL_AMD64_ADDR64;
 185
 186     return std::make_tuple(Offset, RelType, Addend);
 187   }
 188
 189   Expected<object::relocation_iterator>
 190   processRelocationRef(unsigned SectionID,
 191                        object::relocation_iterator RelI,
 192                        const object::ObjectFile &Obj,
 193                        ObjSectionToIDMap &ObjSectionToID,
 194                        StubMap &Stubs) override {
 195     // If possible, find the symbol referred to in the relocation,
 196     // and the section that contains it.
 197     object::symbol_iterator Symbol = RelI->getSymbol();
 198     if (Symbol == Obj.symbol_end())
 199       report_fatal_error("Unknown symbol in relocation");
 200     auto SectionOrError = Symbol->getSection();
 201     if (!SectionOrError)
 202       return SectionOrError.takeError();
 203     object::section_iterator SecI = *SectionOrError;
 204     // If there is no section, this must be an external reference.
 205     const bool IsExtern = SecI == Obj.section_end();
 206
 207     // Determine the Addend used to adjust the relocation value.
 208     uint64_t RelType = RelI->getType();
 209     uint64_t Offset = RelI->getOffset();
 210     uint64_t Addend = 0;
 211     SectionEntry &Section = Sections[SectionID];
 212     uintptr_t ObjTarget = Section.getObjAddress() + Offset;
 213
 214     Expected<StringRef> TargetNameOrErr = Symbol->getName();
 215     if (!TargetNameOrErr)
 216       return TargetNameOrErr.takeError();
 217     StringRef TargetName = *TargetNameOrErr;
 218
 219     switch (RelType) {
 220
 221     case COFF::IMAGE_REL_AMD64_REL32:
 222     case COFF::IMAGE_REL_AMD64_REL32_1:
 223     case COFF::IMAGE_REL_AMD64_REL32_2:
 224     case COFF::IMAGE_REL_AMD64_REL32_3:
 225     case COFF::IMAGE_REL_AMD64_REL32_4:
 226     case COFF::IMAGE_REL_AMD64_REL32_5:
 227     case COFF::IMAGE_REL_AMD64_ADDR32NB: {
 228       uint8_t *Displacement = (uint8_t *)ObjTarget;
 229       Addend = readBytesUnaligned(Displacement, 4);
 230
 231       if (IsExtern)
 232         std::tie(Offset, RelType, Addend) = generateRelocationStub(
 233           SectionID, TargetName, Offset, RelType, Addend, Stubs);
 234
 235       break;
 236     }
 237
 238     case COFF::IMAGE_REL_AMD64_ADDR64: {
 239       uint8_t *Displacement = (uint8_t *)ObjTarget;
 240       Addend = readBytesUnaligned(Displacement, 8);
 241       break;
 242     }
 243
 244     default:
 245       break;
 246     }
 247
 248     LLVM_DEBUG(dbgs() << "\t\tIn Section " << SectionID << " Offset " << Offset
 249                       << " RelType: " << RelType << " TargetName: "
 250                       << TargetName << " Addend " << Addend << "\n");
 251
 252     if (IsExtern) {
 253       RelocationEntry RE(SectionID, Offset, RelType, Addend);
 254       addRelocationForSymbol(RE, TargetName);
 255     } else {
 256       bool IsCode = SecI->isText();
 257       unsigned TargetSectionID;
 258       if (auto TargetSectionIDOrErr =
 259           findOrEmitSection(Obj, *SecI, IsCode, ObjSectionToID))
 260         TargetSectionID = *TargetSectionIDOrErr;
 261       else
 262         return TargetSectionIDOrErr.takeError();
 263       uint64_t TargetOffset = getSymbolOffset(*Symbol);
 264       RelocationEntry RE(SectionID, Offset, RelType, TargetOffset + Addend);
 265       addRelocationForSection(RE, TargetSectionID);
 266     }
 267
 268     return ++RelI;
 269   }
 270
 271   void registerEHFrames() override {
 272     for (auto const &EHFrameSID : UnregisteredEHFrameSections) {
 273       uint8_t *EHFrameAddr = Sections[EHFrameSID].getAddress();
 274       uint64_t EHFrameLoadAddr = Sections[EHFrameSID].getLoadAddress();
 275       size_t EHFrameSize = Sections[EHFrameSID].getSize();
 276       MemMgr.registerEHFrames(EHFrameAddr, EHFrameLoadAddr, EHFrameSize);
 277       RegisteredEHFrameSections.push_back(EHFrameSID);
 278     }
 279     UnregisteredEHFrameSections.clear();
 280   }
 281
 282   Error finalizeLoad(const object::ObjectFile &Obj,
 283                      ObjSectionToIDMap &SectionMap) override {
 284     // Look for and record the EH frame section IDs.
 285     for (const auto &SectionPair : SectionMap) {
 286       const object::SectionRef &Section = SectionPair.first;
 287       Expected<StringRef> NameOrErr = Section.getName();
 288       if (!NameOrErr)
 289         return NameOrErr.takeError();
 290
 291       // Note unwind info is stored in .pdata but often points to .xdata
 292       // with an IMAGE_REL_AMD64_ADDR32NB relocation. Using a memory manager
 293       // that keeps sections ordered in relation to __ImageBase is necessary.
 294       if ((*NameOrErr) == ".pdata")
 295         UnregisteredEHFrameSections.push_back(SectionPair.second);
 296     }
 297     return Error::success();
 298   }
 299 };
 300
 301 } // end namespace llvm
 302
 303 #undef DEBUG_TYPE
 304
 305 #endif