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