xref: /freebsd/contrib/llvm-project/llvm/lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldMachOAArch64.h (revision 2e3f49888ec8851bafb22011533217487764fdb0)
1 //===-- RuntimeDyldMachOAArch64.h -- MachO/AArch64 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 #ifndef LLVM_LIB_EXECUTIONENGINE_RUNTIMEDYLD_TARGETS_RUNTIMEDYLDMACHOAARCH64_H
10 #define LLVM_LIB_EXECUTIONENGINE_RUNTIMEDYLD_TARGETS_RUNTIMEDYLDMACHOAARCH64_H
11 
12 #include "../RuntimeDyldMachO.h"
13 #include "llvm/Support/Endian.h"
14 
15 #define DEBUG_TYPE "dyld"
16 
17 namespace llvm {
18 
19 class RuntimeDyldMachOAArch64
20     : public RuntimeDyldMachOCRTPBase<RuntimeDyldMachOAArch64> {
21 public:
22 
23   typedef uint64_t TargetPtrT;
24 
25   RuntimeDyldMachOAArch64(RuntimeDyld::MemoryManager &MM,
26                           JITSymbolResolver &Resolver)
27       : RuntimeDyldMachOCRTPBase(MM, Resolver) {}
28 
29   unsigned getMaxStubSize() const override { return 8; }
30 
31   Align getStubAlignment() override { return Align(8); }
32 
33   /// Extract the addend encoded in the instruction / memory location.
34   Expected<int64_t> decodeAddend(const RelocationEntry &RE) const {
35     const SectionEntry &Section = Sections[RE.SectionID];
36     uint8_t *LocalAddress = Section.getAddressWithOffset(RE.Offset);
37     unsigned NumBytes = 1 << RE.Size;
38     int64_t Addend = 0;
39     // Verify that the relocation has the correct size and alignment.
40     switch (RE.RelType) {
41     default: {
42       std::string ErrMsg;
43       {
44         raw_string_ostream ErrStream(ErrMsg);
45         ErrStream << "Unsupported relocation type: "
46                   << getRelocName(RE.RelType);
47       }
48       return make_error<StringError>(std::move(ErrMsg),
49                                      inconvertibleErrorCode());
50     }
51     case MachO::ARM64_RELOC_POINTER_TO_GOT:
52     case MachO::ARM64_RELOC_UNSIGNED: {
53       if (NumBytes != 4 && NumBytes != 8) {
54         std::string ErrMsg;
55         {
56           raw_string_ostream ErrStream(ErrMsg);
57           ErrStream << "Invalid relocation size for relocation "
58                     << getRelocName(RE.RelType);
59         }
60         return make_error<StringError>(std::move(ErrMsg),
61                                        inconvertibleErrorCode());
62       }
63       break;
64     }
65     case MachO::ARM64_RELOC_BRANCH26:
66     case MachO::ARM64_RELOC_PAGE21:
67     case MachO::ARM64_RELOC_PAGEOFF12:
68     case MachO::ARM64_RELOC_GOT_LOAD_PAGE21:
69     case MachO::ARM64_RELOC_GOT_LOAD_PAGEOFF12:
70       assert(NumBytes == 4 && "Invalid relocation size.");
71       assert((((uintptr_t)LocalAddress & 0x3) == 0) &&
72              "Instruction address is not aligned to 4 bytes.");
73       break;
74     }
75 
76     switch (RE.RelType) {
77     default:
78       llvm_unreachable("Unsupported relocation type!");
79     case MachO::ARM64_RELOC_POINTER_TO_GOT:
80     case MachO::ARM64_RELOC_UNSIGNED:
81       // This could be an unaligned memory location.
82       if (NumBytes == 4)
83         Addend = *reinterpret_cast<support::ulittle32_t *>(LocalAddress);
84       else
85         Addend = *reinterpret_cast<support::ulittle64_t *>(LocalAddress);
86       break;
87     case MachO::ARM64_RELOC_BRANCH26: {
88       // Verify that the relocation points to a B/BL instruction.
89       auto *p = reinterpret_cast<support::aligned_ulittle32_t *>(LocalAddress);
90       assert(((*p & 0xFC000000) == 0x14000000 ||
91               (*p & 0xFC000000) == 0x94000000) &&
92              "Expected branch instruction.");
93 
94       // Get the 26 bit addend encoded in the branch instruction and sign-extend
95       // to 64 bit. The lower 2 bits are always zeros and are therefore implicit
96       // (<< 2).
97       Addend = (*p & 0x03FFFFFF) << 2;
98       Addend = SignExtend64(Addend, 28);
99       break;
100     }
101     case MachO::ARM64_RELOC_GOT_LOAD_PAGE21:
102     case MachO::ARM64_RELOC_PAGE21: {
103       // Verify that the relocation points to the expected adrp instruction.
104       auto *p = reinterpret_cast<support::aligned_ulittle32_t *>(LocalAddress);
105       assert((*p & 0x9F000000) == 0x90000000 && "Expected adrp instruction.");
106 
107       // Get the 21 bit addend encoded in the adrp instruction and sign-extend
108       // to 64 bit. The lower 12 bits (4096 byte page) are always zeros and are
109       // therefore implicit (<< 12).
110       Addend = ((*p & 0x60000000) >> 29) | ((*p & 0x01FFFFE0) >> 3) << 12;
111       Addend = SignExtend64(Addend, 33);
112       break;
113     }
114     case MachO::ARM64_RELOC_GOT_LOAD_PAGEOFF12: {
115       // Verify that the relocation points to one of the expected load / store
116       // instructions.
117       auto *p = reinterpret_cast<support::aligned_ulittle32_t *>(LocalAddress);
118       (void)p;
119       assert((*p & 0x3B000000) == 0x39000000 &&
120              "Only expected load / store instructions.");
121       [[fallthrough]];
122     }
123     case MachO::ARM64_RELOC_PAGEOFF12: {
124       // Verify that the relocation points to one of the expected load / store
125       // or add / sub instructions.
126       auto *p = reinterpret_cast<support::aligned_ulittle32_t *>(LocalAddress);
127       assert((((*p & 0x3B000000) == 0x39000000) ||
128               ((*p & 0x11C00000) == 0x11000000)   ) &&
129              "Expected load / store  or add/sub instruction.");
130 
131       // Get the 12 bit addend encoded in the instruction.
132       Addend = (*p & 0x003FFC00) >> 10;
133 
134       // Check which instruction we are decoding to obtain the implicit shift
135       // factor of the instruction.
136       int ImplicitShift = 0;
137       if ((*p & 0x3B000000) == 0x39000000) { // << load / store
138         // For load / store instructions the size is encoded in bits 31:30.
139         ImplicitShift = ((*p >> 30) & 0x3);
140         if (ImplicitShift == 0) {
141           // Check if this a vector op to get the correct shift value.
142           if ((*p & 0x04800000) == 0x04800000)
143             ImplicitShift = 4;
144         }
145       }
146       // Compensate for implicit shift.
147       Addend <<= ImplicitShift;
148       break;
149     }
150     }
151     return Addend;
152   }
153 
154   /// Extract the addend encoded in the instruction.
155   void encodeAddend(uint8_t *LocalAddress, unsigned NumBytes,
156                     MachO::RelocationInfoType RelType, int64_t Addend) const {
157     // Verify that the relocation has the correct alignment.
158     switch (RelType) {
159     default:
160       llvm_unreachable("Unsupported relocation type!");
161     case MachO::ARM64_RELOC_POINTER_TO_GOT:
162     case MachO::ARM64_RELOC_UNSIGNED:
163       assert((NumBytes == 4 || NumBytes == 8) && "Invalid relocation size.");
164       break;
165     case MachO::ARM64_RELOC_BRANCH26:
166     case MachO::ARM64_RELOC_PAGE21:
167     case MachO::ARM64_RELOC_PAGEOFF12:
168     case MachO::ARM64_RELOC_GOT_LOAD_PAGE21:
169     case MachO::ARM64_RELOC_GOT_LOAD_PAGEOFF12:
170       assert(NumBytes == 4 && "Invalid relocation size.");
171       assert((((uintptr_t)LocalAddress & 0x3) == 0) &&
172              "Instruction address is not aligned to 4 bytes.");
173       break;
174     }
175 
176     switch (RelType) {
177     default:
178       llvm_unreachable("Unsupported relocation type!");
179     case MachO::ARM64_RELOC_POINTER_TO_GOT:
180     case MachO::ARM64_RELOC_UNSIGNED:
181       // This could be an unaligned memory location.
182       if (NumBytes == 4)
183         *reinterpret_cast<support::ulittle32_t *>(LocalAddress) = Addend;
184       else
185         *reinterpret_cast<support::ulittle64_t *>(LocalAddress) = Addend;
186       break;
187     case MachO::ARM64_RELOC_BRANCH26: {
188       auto *p = reinterpret_cast<support::aligned_ulittle32_t *>(LocalAddress);
189       // Verify that the relocation points to the expected branch instruction.
190       assert(((*p & 0xFC000000) == 0x14000000 ||
191               (*p & 0xFC000000) == 0x94000000) &&
192              "Expected branch instruction.");
193 
194       // Verify addend value.
195       assert((Addend & 0x3) == 0 && "Branch target is not aligned");
196       assert(isInt<28>(Addend) && "Branch target is out of range.");
197 
198       // Encode the addend as 26 bit immediate in the branch instruction.
199       *p = (*p & 0xFC000000) | ((uint32_t)(Addend >> 2) & 0x03FFFFFF);
200       break;
201     }
202     case MachO::ARM64_RELOC_GOT_LOAD_PAGE21:
203     case MachO::ARM64_RELOC_PAGE21: {
204       // Verify that the relocation points to the expected adrp instruction.
205       auto *p = reinterpret_cast<support::aligned_ulittle32_t *>(LocalAddress);
206       assert((*p & 0x9F000000) == 0x90000000 && "Expected adrp instruction.");
207 
208       // Check that the addend fits into 21 bits (+ 12 lower bits).
209       assert((Addend & 0xFFF) == 0 && "ADRP target is not page aligned.");
210       assert(isInt<33>(Addend) && "Invalid page reloc value.");
211 
212       // Encode the addend into the instruction.
213       uint32_t ImmLoValue = ((uint64_t)Addend << 17) & 0x60000000;
214       uint32_t ImmHiValue = ((uint64_t)Addend >> 9) & 0x00FFFFE0;
215       *p = (*p & 0x9F00001F) | ImmHiValue | ImmLoValue;
216       break;
217     }
218     case MachO::ARM64_RELOC_GOT_LOAD_PAGEOFF12: {
219       // Verify that the relocation points to one of the expected load / store
220       // instructions.
221       auto *p = reinterpret_cast<support::aligned_ulittle32_t *>(LocalAddress);
222       assert((*p & 0x3B000000) == 0x39000000 &&
223              "Only expected load / store instructions.");
224       (void)p;
225       [[fallthrough]];
226     }
227     case MachO::ARM64_RELOC_PAGEOFF12: {
228       // Verify that the relocation points to one of the expected load / store
229       // or add / sub instructions.
230       auto *p = reinterpret_cast<support::aligned_ulittle32_t *>(LocalAddress);
231       assert((((*p & 0x3B000000) == 0x39000000) ||
232               ((*p & 0x11C00000) == 0x11000000)   ) &&
233              "Expected load / store  or add/sub instruction.");
234 
235       // Check which instruction we are decoding to obtain the implicit shift
236       // factor of the instruction and verify alignment.
237       int ImplicitShift = 0;
238       if ((*p & 0x3B000000) == 0x39000000) { // << load / store
239         // For load / store instructions the size is encoded in bits 31:30.
240         ImplicitShift = ((*p >> 30) & 0x3);
241         switch (ImplicitShift) {
242         case 0:
243           // Check if this a vector op to get the correct shift value.
244           if ((*p & 0x04800000) == 0x04800000) {
245             ImplicitShift = 4;
246             assert(((Addend & 0xF) == 0) &&
247                    "128-bit LDR/STR not 16-byte aligned.");
248           }
249           break;
250         case 1:
251           assert(((Addend & 0x1) == 0) && "16-bit LDR/STR not 2-byte aligned.");
252           break;
253         case 2:
254           assert(((Addend & 0x3) == 0) && "32-bit LDR/STR not 4-byte aligned.");
255           break;
256         case 3:
257           assert(((Addend & 0x7) == 0) && "64-bit LDR/STR not 8-byte aligned.");
258           break;
259         }
260       }
261       // Compensate for implicit shift.
262       Addend >>= ImplicitShift;
263       assert(isUInt<12>(Addend) && "Addend cannot be encoded.");
264 
265       // Encode the addend into the instruction.
266       *p = (*p & 0xFFC003FF) | ((uint32_t)(Addend << 10) & 0x003FFC00);
267       break;
268     }
269     }
270   }
271 
272   Expected<relocation_iterator>
273   processRelocationRef(unsigned SectionID, relocation_iterator RelI,
274                        const ObjectFile &BaseObjT,
275                        ObjSectionToIDMap &ObjSectionToID,
276                        StubMap &Stubs) override {
277     const MachOObjectFile &Obj =
278       static_cast<const MachOObjectFile &>(BaseObjT);
279     MachO::any_relocation_info RelInfo =
280         Obj.getRelocation(RelI->getRawDataRefImpl());
281 
282     if (Obj.isRelocationScattered(RelInfo))
283       return make_error<RuntimeDyldError>("Scattered relocations not supported "
284                                           "for MachO AArch64");
285 
286     // ARM64 has an ARM64_RELOC_ADDEND relocation type that carries an explicit
287     // addend for the following relocation. If found: (1) store the associated
288     // addend, (2) consume the next relocation, and (3) use the stored addend to
289     // override the addend.
290     int64_t ExplicitAddend = 0;
291     if (Obj.getAnyRelocationType(RelInfo) == MachO::ARM64_RELOC_ADDEND) {
292       assert(!Obj.getPlainRelocationExternal(RelInfo));
293       assert(!Obj.getAnyRelocationPCRel(RelInfo));
294       assert(Obj.getAnyRelocationLength(RelInfo) == 2);
295       int64_t RawAddend = Obj.getPlainRelocationSymbolNum(RelInfo);
296       // Sign-extend the 24-bit to 64-bit.
297       ExplicitAddend = SignExtend64(RawAddend, 24);
298       ++RelI;
299       RelInfo = Obj.getRelocation(RelI->getRawDataRefImpl());
300     }
301 
302     if (Obj.getAnyRelocationType(RelInfo) == MachO::ARM64_RELOC_SUBTRACTOR)
303       return processSubtractRelocation(SectionID, RelI, Obj, ObjSectionToID);
304 
305     RelocationEntry RE(getRelocationEntry(SectionID, Obj, RelI));
306 
307     if (RE.RelType == MachO::ARM64_RELOC_POINTER_TO_GOT) {
308       bool Valid =
309           (RE.Size == 2 && RE.IsPCRel) || (RE.Size == 3 && !RE.IsPCRel);
310       if (!Valid)
311         return make_error<StringError>("ARM64_RELOC_POINTER_TO_GOT supports "
312                                        "32-bit pc-rel or 64-bit absolute only",
313                                        inconvertibleErrorCode());
314     }
315 
316     if (auto Addend = decodeAddend(RE))
317       RE.Addend = *Addend;
318     else
319       return Addend.takeError();
320 
321     assert((ExplicitAddend == 0 || RE.Addend == 0) && "Relocation has "\
322       "ARM64_RELOC_ADDEND and embedded addend in the instruction.");
323     if (ExplicitAddend)
324       RE.Addend = ExplicitAddend;
325 
326     RelocationValueRef Value;
327     if (auto ValueOrErr = getRelocationValueRef(Obj, RelI, RE, ObjSectionToID))
328       Value = *ValueOrErr;
329     else
330       return ValueOrErr.takeError();
331 
332     bool IsExtern = Obj.getPlainRelocationExternal(RelInfo);
333     if (RE.RelType == MachO::ARM64_RELOC_POINTER_TO_GOT) {
334       // We'll take care of the offset in processGOTRelocation.
335       Value.Offset = 0;
336     } else if (!IsExtern && RE.IsPCRel)
337       makeValueAddendPCRel(Value, RelI, 1 << RE.Size);
338 
339     RE.Addend = Value.Offset;
340 
341     if (RE.RelType == MachO::ARM64_RELOC_GOT_LOAD_PAGE21 ||
342         RE.RelType == MachO::ARM64_RELOC_GOT_LOAD_PAGEOFF12 ||
343         RE.RelType == MachO::ARM64_RELOC_POINTER_TO_GOT)
344       processGOTRelocation(RE, Value, Stubs);
345     else {
346       if (Value.SymbolName)
347         addRelocationForSymbol(RE, Value.SymbolName);
348       else
349         addRelocationForSection(RE, Value.SectionID);
350     }
351 
352     return ++RelI;
353   }
354 
355   void resolveRelocation(const RelocationEntry &RE, uint64_t Value) override {
356     LLVM_DEBUG(dumpRelocationToResolve(RE, Value));
357 
358     const SectionEntry &Section = Sections[RE.SectionID];
359     uint8_t *LocalAddress = Section.getAddressWithOffset(RE.Offset);
360     MachO::RelocationInfoType RelType =
361       static_cast<MachO::RelocationInfoType>(RE.RelType);
362 
363     switch (RelType) {
364     default:
365       llvm_unreachable("Invalid relocation type!");
366     case MachO::ARM64_RELOC_UNSIGNED: {
367       assert(!RE.IsPCRel && "PCRel and ARM64_RELOC_UNSIGNED not supported");
368       // Mask in the target value a byte at a time (we don't have an alignment
369       // guarantee for the target address, so this is safest).
370       if (RE.Size < 2)
371         llvm_unreachable("Invalid size for ARM64_RELOC_UNSIGNED");
372 
373       encodeAddend(LocalAddress, 1 << RE.Size, RelType, Value + RE.Addend);
374       break;
375     }
376 
377     case MachO::ARM64_RELOC_POINTER_TO_GOT: {
378       assert(((RE.Size == 2 && RE.IsPCRel) || (RE.Size == 3 && !RE.IsPCRel)) &&
379              "ARM64_RELOC_POINTER_TO_GOT only supports 32-bit pc-rel or 64-bit "
380              "absolute");
381       // Addend is the GOT entry address and RE.Offset the target of the
382       // relocation.
383       uint64_t Result =
384           RE.IsPCRel ? (RE.Addend - RE.Offset) : (Value + RE.Addend);
385       encodeAddend(LocalAddress, 1 << RE.Size, RelType, Result);
386       break;
387     }
388 
389     case MachO::ARM64_RELOC_BRANCH26: {
390       assert(RE.IsPCRel && "not PCRel and ARM64_RELOC_BRANCH26 not supported");
391       // Check if branch is in range.
392       uint64_t FinalAddress = Section.getLoadAddressWithOffset(RE.Offset);
393       int64_t PCRelVal = Value - FinalAddress + RE.Addend;
394       encodeAddend(LocalAddress, /*Size=*/4, RelType, PCRelVal);
395       break;
396     }
397     case MachO::ARM64_RELOC_GOT_LOAD_PAGE21:
398     case MachO::ARM64_RELOC_PAGE21: {
399       assert(RE.IsPCRel && "not PCRel and ARM64_RELOC_PAGE21 not supported");
400       // Adjust for PC-relative relocation and offset.
401       uint64_t FinalAddress = Section.getLoadAddressWithOffset(RE.Offset);
402       int64_t PCRelVal =
403         ((Value + RE.Addend) & (-4096)) - (FinalAddress & (-4096));
404       encodeAddend(LocalAddress, /*Size=*/4, RelType, PCRelVal);
405       break;
406     }
407     case MachO::ARM64_RELOC_GOT_LOAD_PAGEOFF12:
408     case MachO::ARM64_RELOC_PAGEOFF12: {
409       assert(!RE.IsPCRel && "PCRel and ARM64_RELOC_PAGEOFF21 not supported");
410       // Add the offset from the symbol.
411       Value += RE.Addend;
412       // Mask out the page address and only use the lower 12 bits.
413       Value &= 0xFFF;
414       encodeAddend(LocalAddress, /*Size=*/4, RelType, Value);
415       break;
416     }
417     case MachO::ARM64_RELOC_SUBTRACTOR: {
418       uint64_t SectionABase = Sections[RE.Sections.SectionA].getLoadAddress();
419       uint64_t SectionBBase = Sections[RE.Sections.SectionB].getLoadAddress();
420       assert((Value == SectionABase || Value == SectionBBase) &&
421              "Unexpected SUBTRACTOR relocation value.");
422       Value = SectionABase - SectionBBase + RE.Addend;
423       writeBytesUnaligned(Value, LocalAddress, 1 << RE.Size);
424       break;
425     }
426 
427     case MachO::ARM64_RELOC_TLVP_LOAD_PAGE21:
428     case MachO::ARM64_RELOC_TLVP_LOAD_PAGEOFF12:
429       llvm_unreachable("Relocation type not yet implemented!");
430     case MachO::ARM64_RELOC_ADDEND:
431       llvm_unreachable("ARM64_RELOC_ADDEND should have been handeled by "
432                        "processRelocationRef!");
433     }
434   }
435 
436   Error finalizeSection(const ObjectFile &Obj, unsigned SectionID,
437                        const SectionRef &Section) {
438     return Error::success();
439   }
440 
441 private:
442   void processGOTRelocation(const RelocationEntry &RE,
443                             RelocationValueRef &Value, StubMap &Stubs) {
444     assert((RE.RelType == MachO::ARM64_RELOC_POINTER_TO_GOT &&
445             (RE.Size == 2 || RE.Size == 3)) ||
446            RE.Size == 2);
447     SectionEntry &Section = Sections[RE.SectionID];
448     StubMap::const_iterator i = Stubs.find(Value);
449     int64_t Offset;
450     if (i != Stubs.end())
451       Offset = static_cast<int64_t>(i->second);
452     else {
453       // FIXME: There must be a better way to do this then to check and fix the
454       // alignment every time!!!
455       uintptr_t BaseAddress = uintptr_t(Section.getAddress());
456       uintptr_t StubAlignment = getStubAlignment().value();
457       uintptr_t StubAddress =
458           (BaseAddress + Section.getStubOffset() + StubAlignment - 1) &
459           -StubAlignment;
460       unsigned StubOffset = StubAddress - BaseAddress;
461       Stubs[Value] = StubOffset;
462       assert(isAligned(getStubAlignment(), StubAddress) &&
463              "GOT entry not aligned");
464       RelocationEntry GOTRE(RE.SectionID, StubOffset,
465                             MachO::ARM64_RELOC_UNSIGNED, Value.Offset,
466                             /*IsPCRel=*/false, /*Size=*/3);
467       if (Value.SymbolName)
468         addRelocationForSymbol(GOTRE, Value.SymbolName);
469       else
470         addRelocationForSection(GOTRE, Value.SectionID);
471       Section.advanceStubOffset(getMaxStubSize());
472       Offset = static_cast<int64_t>(StubOffset);
473     }
474     RelocationEntry TargetRE(RE.SectionID, RE.Offset, RE.RelType, Offset,
475                              RE.IsPCRel, RE.Size);
476     addRelocationForSection(TargetRE, RE.SectionID);
477   }
478 
479   Expected<relocation_iterator>
480   processSubtractRelocation(unsigned SectionID, relocation_iterator RelI,
481                             const ObjectFile &BaseObjT,
482                             ObjSectionToIDMap &ObjSectionToID) {
483     const MachOObjectFile &Obj =
484         static_cast<const MachOObjectFile&>(BaseObjT);
485     MachO::any_relocation_info RE =
486         Obj.getRelocation(RelI->getRawDataRefImpl());
487 
488     unsigned Size = Obj.getAnyRelocationLength(RE);
489     uint64_t Offset = RelI->getOffset();
490     uint8_t *LocalAddress = Sections[SectionID].getAddressWithOffset(Offset);
491     unsigned NumBytes = 1 << Size;
492 
493     Expected<StringRef> SubtrahendNameOrErr = RelI->getSymbol()->getName();
494     if (!SubtrahendNameOrErr)
495       return SubtrahendNameOrErr.takeError();
496     auto SubtrahendI = GlobalSymbolTable.find(*SubtrahendNameOrErr);
497     unsigned SectionBID = SubtrahendI->second.getSectionID();
498     uint64_t SectionBOffset = SubtrahendI->second.getOffset();
499     int64_t Addend =
500       SignExtend64(readBytesUnaligned(LocalAddress, NumBytes), NumBytes * 8);
501 
502     ++RelI;
503     Expected<StringRef> MinuendNameOrErr = RelI->getSymbol()->getName();
504     if (!MinuendNameOrErr)
505       return MinuendNameOrErr.takeError();
506     auto MinuendI = GlobalSymbolTable.find(*MinuendNameOrErr);
507     unsigned SectionAID = MinuendI->second.getSectionID();
508     uint64_t SectionAOffset = MinuendI->second.getOffset();
509 
510     RelocationEntry R(SectionID, Offset, MachO::ARM64_RELOC_SUBTRACTOR, (uint64_t)Addend,
511                       SectionAID, SectionAOffset, SectionBID, SectionBOffset,
512                       false, Size);
513 
514     addRelocationForSection(R, SectionAID);
515 
516     return ++RelI;
517   }
518 
519   static const char *getRelocName(uint32_t RelocType) {
520     switch (RelocType) {
521       case MachO::ARM64_RELOC_UNSIGNED: return "ARM64_RELOC_UNSIGNED";
522       case MachO::ARM64_RELOC_SUBTRACTOR: return "ARM64_RELOC_SUBTRACTOR";
523       case MachO::ARM64_RELOC_BRANCH26: return "ARM64_RELOC_BRANCH26";
524       case MachO::ARM64_RELOC_PAGE21: return "ARM64_RELOC_PAGE21";
525       case MachO::ARM64_RELOC_PAGEOFF12: return "ARM64_RELOC_PAGEOFF12";
526       case MachO::ARM64_RELOC_GOT_LOAD_PAGE21: return "ARM64_RELOC_GOT_LOAD_PAGE21";
527       case MachO::ARM64_RELOC_GOT_LOAD_PAGEOFF12: return "ARM64_RELOC_GOT_LOAD_PAGEOFF12";
528       case MachO::ARM64_RELOC_POINTER_TO_GOT: return "ARM64_RELOC_POINTER_TO_GOT";
529       case MachO::ARM64_RELOC_TLVP_LOAD_PAGE21: return "ARM64_RELOC_TLVP_LOAD_PAGE21";
530       case MachO::ARM64_RELOC_TLVP_LOAD_PAGEOFF12: return "ARM64_RELOC_TLVP_LOAD_PAGEOFF12";
531       case MachO::ARM64_RELOC_ADDEND: return "ARM64_RELOC_ADDEND";
532     }
533     return "Unrecognized arm64 addend";
534   }
535 
536 };
537 }
538 
539 #undef DEBUG_TYPE
540 
541 #endif
542