lld/MachO/Relocations.h

   1 //===- Relocations.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_RELOCATIONS_H
  10 #define LLD_MACHO_RELOCATIONS_H
  11
  12 #include "llvm/ADT/BitmaskEnum.h"
  13 #include "llvm/ADT/PointerUnion.h"
  14 #include "llvm/BinaryFormat/MachO.h"
  15 #include "llvm/Support/Endian.h"
  16
  17 #include <cstddef>
  18 #include <cstdint>
  19
  20 namespace lld::macho {
  21 LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE();
  22
  23 class Symbol;
  24 class InputSection;
  25
  26 enum class RelocAttrBits {
  27   _0 = 0,              // invalid
  28   PCREL = 1 << 0,      // Value is PC-relative offset
  29   ABSOLUTE = 1 << 1,   // Value is an absolute address or fixed offset
  30   BYTE4 = 1 << 2,      // 4 byte datum
  31   BYTE8 = 1 << 3,      // 8 byte datum
  32   EXTERN = 1 << 4,     // Can have an external symbol
  33   LOCAL = 1 << 5,      // Can have a local symbol
  34   ADDEND = 1 << 6,     // *_ADDEND paired prefix reloc
  35   SUBTRAHEND = 1 << 7, // *_SUBTRACTOR paired prefix reloc
  36   BRANCH = 1 << 8,     // Value is branch target
  37   GOT = 1 << 9,        // References a symbol in the Global Offset Table
  38   TLV = 1 << 10,       // References a thread-local symbol
  39   LOAD = 1 << 11,      // Relaxable indirect load
  40   POINTER = 1 << 12,   // Non-relaxable indirect load (pointer is taken)
  41   UNSIGNED = 1 << 13,  // *_UNSIGNED relocs
  42   LLVM_MARK_AS_BITMASK_ENUM(/*LargestValue*/ (1 << 14) - 1),
  43 };
  44 // Note: SUBTRACTOR always pairs with UNSIGNED (a delta between two symbols).
  45
  46 struct RelocAttrs {
  47   llvm::StringRef name;
  48   RelocAttrBits bits;
  49   bool hasAttr(RelocAttrBits b) const { return (bits & b) == b; }
  50 };
  51
  52 struct Reloc {
  53   uint8_t type = llvm::MachO::GENERIC_RELOC_INVALID;
  54   bool pcrel = false;
  55   uint8_t length = 0;
  56   // The offset from the start of the subsection that this relocation belongs
  57   // to.
  58   uint32_t offset = 0;
  59   // Adding this offset to the address of the referent symbol or subsection
  60   // gives the destination that this relocation refers to.
  61   int64_t addend = 0;
  62   llvm::PointerUnion<Symbol *, InputSection *> referent = nullptr;
  63
  64   Reloc() = default;
  65
  66   Reloc(uint8_t type, bool pcrel, uint8_t length, uint32_t offset,
  67         int64_t addend, llvm::PointerUnion<Symbol *, InputSection *> referent)
  68       : type(type), pcrel(pcrel), length(length), offset(offset),
  69         addend(addend), referent(referent) {}
  70
  71   InputSection *getReferentInputSection() const;
  72
  73   // Must point to an offset within a CStringInputSection or a
  74   // ConcatInputSection.
  75   llvm::StringRef getReferentString() const;
  76 };
  77
  78 bool validateSymbolRelocation(const Symbol *, const InputSection *,
  79                               const Reloc &);
  80
  81 /*
  82  * v: The value the relocation is attempting to encode
  83  * bits: The number of bits actually available to encode this relocation
  84  */
  85 void reportRangeError(void *loc, const Reloc &, const llvm::Twine &v,
  86                       uint8_t bits, int64_t min, uint64_t max);
  87
  88 struct SymbolDiagnostic {
  89   const Symbol *symbol;
  90   llvm::StringRef reason;
  91 };
  92
  93 void reportRangeError(void *loc, SymbolDiagnostic, const llvm::Twine &v,
  94                       uint8_t bits, int64_t min, uint64_t max);
  95
  96 template <typename Diagnostic>
  97 inline void checkInt(void *loc, Diagnostic d, int64_t v, int bits) {
  98   if (v != llvm::SignExtend64(v, bits))
  99     reportRangeError(loc, d, llvm::Twine(v), bits, llvm::minIntN(bits),
 100                      llvm::maxIntN(bits));
 101 }
 102
 103 template <typename Diagnostic>
 104 inline void checkUInt(void *loc, Diagnostic d, uint64_t v, int bits) {
 105   if ((v >> bits) != 0)
 106     reportRangeError(loc, d, llvm::Twine(v), bits, 0, llvm::maxUIntN(bits));
 107 }
 108
 109 inline void writeAddress(uint8_t *loc, uint64_t addr, uint8_t length) {
 110   switch (length) {
 111   case 2:
 112     llvm::support::endian::write32le(loc, addr);
 113     break;
 114   case 3:
 115     llvm::support::endian::write64le(loc, addr);
 116     break;
 117   default:
 118     llvm_unreachable("invalid r_length");
 119   }
 120 }
 121
 122 InputSection *offsetToInputSection(uint64_t *);
 123
 124 extern const RelocAttrs invalidRelocAttrs;
 125
 126 } // namespace lld::Macho
 127
 128 #endif