lld/MachO/Target.h

   1 //===- Target.h -------------------------------------------------*- 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 #ifndef LLD_MACHO_TARGET_H
  10 #define LLD_MACHO_TARGET_H
  11
  12 #include "MachOStructs.h"
  13 #include "Relocations.h"
  14
  15 #include "llvm/ADT/BitmaskEnum.h"
  16 #include "llvm/BinaryFormat/MachO.h"
  17 #include "llvm/Support/MathExtras.h"
  18 #include "llvm/Support/MemoryBuffer.h"
  19
  20 #include <cstddef>
  21 #include <cstdint>
  22
  23 #include "mach-o/compact_unwind_encoding.h"
  24
  25 namespace lld::macho {
  26 LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE();
  27
  28 class Symbol;
  29 class Defined;
  30 class DylibSymbol;
  31 class InputSection;
  32 class ObjFile;
  33
  34 static_assert(static_cast<uint32_t>(UNWIND_X86_64_MODE_MASK) ==
  35                   static_cast<uint32_t>(UNWIND_X86_MODE_MASK) &&
  36               static_cast<uint32_t>(UNWIND_ARM64_MODE_MASK) ==
  37                   static_cast<uint32_t>(UNWIND_X86_64_MODE_MASK));
  38
  39 // Since the mode masks have the same value on all targets, define
  40 // a common one for convenience.
  41 constexpr uint32_t UNWIND_MODE_MASK = UNWIND_X86_64_MODE_MASK;
  42
  43 class TargetInfo {
  44 public:
  45   template <class LP> TargetInfo(LP) {
  46     // Having these values available in TargetInfo allows us to access them
  47     // without having to resort to templates.
  48     magic = LP::magic;
  49     pageZeroSize = LP::pageZeroSize;
  50     headerSize = sizeof(typename LP::mach_header);
  51     wordSize = LP::wordSize;
  52     p2WordSize = llvm::CTLog2<LP::wordSize>();
  53   }
  54
  55   virtual ~TargetInfo() = default;
  56
  57   // Validate the relocation structure and get its addend.
  58   virtual int64_t
  59   getEmbeddedAddend(llvm::MemoryBufferRef, uint64_t offset,
  60                     const llvm::MachO::relocation_info) const = 0;
  61   virtual void relocateOne(uint8_t *loc, const Reloc &, uint64_t va,
  62                            uint64_t relocVA) const = 0;
  63
  64   // Write code for lazy binding. See the comments on StubsSection for more
  65   // details.
  66   virtual void writeStub(uint8_t *buf, const Symbol &,
  67                          uint64_t pointerVA) const = 0;
  68   virtual void writeStubHelperHeader(uint8_t *buf) const = 0;
  69   virtual void writeStubHelperEntry(uint8_t *buf, const Symbol &,
  70                                     uint64_t entryAddr) const = 0;
  71
  72   virtual void writeObjCMsgSendStub(uint8_t *buf, Symbol *sym,
  73                                     uint64_t stubsAddr, uint64_t &stubOffset,
  74                                     uint64_t selrefVA,
  75                                     Symbol *objcMsgSend) const = 0;
  76
  77   // Init 'thunk' so that it be a direct jump to 'branchTarget'.
  78   virtual void initICFSafeThunkBody(InputSection *thunk,
  79                                     InputSection *branchTarget) const {
  80     llvm_unreachable("target does not support ICF safe thunks");
  81   }
  82
  83   // Given a thunk for which `initICFSafeThunkBody` was called, return the
  84   // branchTarget it was initialized with.
  85   virtual InputSection *getThunkBranchTarget(InputSection *thunk) const {
  86     llvm_unreachable("target does not support ICF safe thunks");
  87   }
  88
  89   virtual uint32_t getICFSafeThunkSize() const {
  90     llvm_unreachable("target does not support ICF safe thunks");
  91   }
  92
  93   // Symbols may be referenced via either the GOT or the stubs section,
  94   // depending on the relocation type. prepareSymbolRelocation() will set up the
  95   // GOT/stubs entries, and resolveSymbolVA() will return the addresses of those
  96   // entries. resolveSymbolVA() may also relax the target instructions to save
  97   // on a level of address indirection.
  98   virtual void relaxGotLoad(uint8_t *loc, uint8_t type) const = 0;
  99
 100   virtual uint64_t getPageSize() const = 0;
 101
 102   virtual void populateThunk(InputSection *thunk, Symbol *funcSym) {
 103     llvm_unreachable("target does not use thunks");
 104   }
 105
 106   const RelocAttrs &getRelocAttrs(uint8_t type) const {
 107     assert(type < relocAttrs.size() && "invalid relocation type");
 108     if (type >= relocAttrs.size())
 109       return invalidRelocAttrs;
 110     return relocAttrs[type];
 111   }
 112
 113   bool hasAttr(uint8_t type, RelocAttrBits bit) const {
 114     return getRelocAttrs(type).hasAttr(bit);
 115   }
 116
 117   bool usesThunks() const { return thunkSize > 0; }
 118
 119   // For now, handleDtraceReloc only implements -no_dtrace_dof, and ensures
 120   // that the linking would not fail even when there are user-provided dtrace
 121   // symbols. However, unlike ld64, lld currently does not emit __dof sections.
 122   virtual void handleDtraceReloc(const Symbol *sym, const Reloc &r,
 123                                  uint8_t *loc) const {
 124     llvm_unreachable("Unsupported architecture for dtrace symbols");
 125   }
 126
 127   virtual void applyOptimizationHints(uint8_t *, const ObjFile &) const {};
 128
 129   uint32_t magic;
 130   llvm::MachO::CPUType cpuType;
 131   uint32_t cpuSubtype;
 132
 133   uint64_t pageZeroSize;
 134   size_t headerSize;
 135   size_t stubSize;
 136   size_t stubHelperHeaderSize;
 137   size_t stubHelperEntrySize;
 138   size_t objcStubsFastSize;
 139   size_t objcStubsSmallSize;
 140   size_t objcStubsFastAlignment;
 141   size_t objcStubsSmallAlignment;
 142   uint8_t p2WordSize;
 143   size_t wordSize;
 144
 145   size_t thunkSize = 0;
 146   uint64_t forwardBranchRange = 0;
 147   uint64_t backwardBranchRange = 0;
 148
 149   uint32_t modeDwarfEncoding;
 150   uint8_t subtractorRelocType;
 151   uint8_t unsignedRelocType;
 152
 153   llvm::ArrayRef<RelocAttrs> relocAttrs;
 154
 155   // We contrive this value as sufficiently far from any valid address that it
 156   // will always be out-of-range for any architecture. UINT64_MAX is not a
 157   // good choice because it is (a) only 1 away from wrapping to 0, and (b) the
 158   // tombstone value for DenseMap<> and caused weird assertions for me.
 159   static constexpr uint64_t outOfRangeVA = 0xfull << 60;
 160 };
 161
 162 TargetInfo *createX86_64TargetInfo();
 163 TargetInfo *createARM64TargetInfo();
 164 TargetInfo *createARM64_32TargetInfo();
 165
 166 struct LP64 {
 167   using mach_header = llvm::MachO::mach_header_64;
 168   using nlist = structs::nlist_64;
 169   using segment_command = llvm::MachO::segment_command_64;
 170   using section = llvm::MachO::section_64;
 171   using encryption_info_command = llvm::MachO::encryption_info_command_64;
 172
 173   static constexpr uint32_t magic = llvm::MachO::MH_MAGIC_64;
 174   static constexpr uint32_t segmentLCType = llvm::MachO::LC_SEGMENT_64;
 175   static constexpr uint32_t encryptionInfoLCType =
 176       llvm::MachO::LC_ENCRYPTION_INFO_64;
 177
 178   static constexpr uint64_t pageZeroSize = 1ull << 32;
 179   static constexpr size_t wordSize = 8;
 180 };
 181
 182 struct ILP32 {
 183   using mach_header = llvm::MachO::mach_header;
 184   using nlist = structs::nlist;
 185   using segment_command = llvm::MachO::segment_command;
 186   using section = llvm::MachO::section;
 187   using encryption_info_command = llvm::MachO::encryption_info_command;
 188
 189   static constexpr uint32_t magic = llvm::MachO::MH_MAGIC;
 190   static constexpr uint32_t segmentLCType = llvm::MachO::LC_SEGMENT;
 191   static constexpr uint32_t encryptionInfoLCType =
 192       llvm::MachO::LC_ENCRYPTION_INFO;
 193
 194   static constexpr uint64_t pageZeroSize = 1ull << 12;
 195   static constexpr size_t wordSize = 4;
 196 };
 197
 198 extern TargetInfo *target;
 199
 200 } // namespace lld::macho
 201
 202 #endif