1//===---- MachO_x86_64.cpp -JIT linker implementation for MachO/x86-64 ----===//
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// MachO/x86-64 jit-link implementation.
10//
11//===----------------------------------------------------------------------===//
12
13#include "llvm/ExecutionEngine/JITLink/MachO_x86_64.h"
14#include "llvm/ExecutionEngine/JITLink/DWARFRecordSectionSplitter.h"
15#include "llvm/ExecutionEngine/JITLink/x86_64.h"
16
17#include "DefineExternalSectionStartAndEndSymbols.h"
18#include "MachOLinkGraphBuilder.h"
19
20#define DEBUG_TYPE "jitlink"
21
22using namespace llvm;
23using namespace llvm::jitlink;
24
25namespace {
26
27class MachOLinkGraphBuilder_x86_64 : public MachOLinkGraphBuilder {
28public:
29 MachOLinkGraphBuilder_x86_64(const object::MachOObjectFile &Obj,
30 SubtargetFeatures Features)
31 : MachOLinkGraphBuilder(Obj, Triple("x86_64-apple-darwin"),
32 std::move(Features), x86_64::getEdgeKindName) {}
33
34private:
35 enum MachONormalizedRelocationType : unsigned {
36 MachOBranch32,
37 MachOPointer32,
38 MachOPointer64,
39 MachOPointer64Anon,
40 MachOPCRel32,
41 MachOPCRel32Minus1,
42 MachOPCRel32Minus2,
43 MachOPCRel32Minus4,
44 MachOPCRel32Anon,
45 MachOPCRel32Minus1Anon,
46 MachOPCRel32Minus2Anon,
47 MachOPCRel32Minus4Anon,
48 MachOPCRel32GOTLoad,
49 MachOPCRel32GOT,
50 MachOPCRel32TLV,
51 MachOSubtractor32,
52 MachOSubtractor64,
53 };
54
55 static Expected<MachONormalizedRelocationType>
56 getRelocKind(const MachO::relocation_info &RI) {
57 switch (RI.r_type) {
58 case MachO::X86_64_RELOC_UNSIGNED:
59 if (!RI.r_pcrel) {
60 if (RI.r_length == 3)
61 return RI.r_extern ? MachOPointer64 : MachOPointer64Anon;
62 else if (RI.r_extern && RI.r_length == 2)
63 return MachOPointer32;
64 }
65 break;
66 case MachO::X86_64_RELOC_SIGNED:
67 if (RI.r_pcrel && RI.r_length == 2)
68 return RI.r_extern ? MachOPCRel32 : MachOPCRel32Anon;
69 break;
70 case MachO::X86_64_RELOC_BRANCH:
71 if (RI.r_pcrel && RI.r_extern && RI.r_length == 2)
72 return MachOBranch32;
73 break;
74 case MachO::X86_64_RELOC_GOT_LOAD:
75 if (RI.r_pcrel && RI.r_extern && RI.r_length == 2)
76 return MachOPCRel32GOTLoad;
77 break;
78 case MachO::X86_64_RELOC_GOT:
79 if (RI.r_pcrel && RI.r_extern && RI.r_length == 2)
80 return MachOPCRel32GOT;
81 break;
82 case MachO::X86_64_RELOC_SUBTRACTOR:
83 if (!RI.r_pcrel && RI.r_extern) {
84 if (RI.r_length == 2)
85 return MachOSubtractor32;
86 else if (RI.r_length == 3)
87 return MachOSubtractor64;
88 }
89 break;
90 case MachO::X86_64_RELOC_SIGNED_1:
91 if (RI.r_pcrel && RI.r_length == 2)
92 return RI.r_extern ? MachOPCRel32Minus1 : MachOPCRel32Minus1Anon;
93 break;
94 case MachO::X86_64_RELOC_SIGNED_2:
95 if (RI.r_pcrel && RI.r_length == 2)
96 return RI.r_extern ? MachOPCRel32Minus2 : MachOPCRel32Minus2Anon;
97 break;
98 case MachO::X86_64_RELOC_SIGNED_4:
99 if (RI.r_pcrel && RI.r_length == 2)
100 return RI.r_extern ? MachOPCRel32Minus4 : MachOPCRel32Minus4Anon;
101 break;
102 case MachO::X86_64_RELOC_TLV:
103 if (RI.r_pcrel && RI.r_extern && RI.r_length == 2)
104 return MachOPCRel32TLV;
105 break;
106 }
107
108 return make_error<JITLinkError>(
109 Args: "Unsupported x86-64 relocation: address=" +
110 formatv(Fmt: "{0:x8}", Vals: RI.r_address) +
111 ", symbolnum=" + formatv(Fmt: "{0:x6}", Vals: RI.r_symbolnum) +
112 ", kind=" + formatv(Fmt: "{0:x1}", Vals: RI.r_type) +
113 ", pc_rel=" + (RI.r_pcrel ? "true" : "false") +
114 ", extern=" + (RI.r_extern ? "true" : "false") +
115 ", length=" + formatv(Fmt: "{0:d}", Vals: RI.r_length));
116 }
117
118 using PairRelocInfo = std::tuple<Edge::Kind, Symbol *, uint64_t>;
119
120 // Parses paired SUBTRACTOR/UNSIGNED relocations and, on success,
121 // returns the edge kind and addend to be used.
122 Expected<PairRelocInfo> parsePairRelocation(
123 Block &BlockToFix, MachONormalizedRelocationType SubtractorKind,
124 const MachO::relocation_info &SubRI, orc::ExecutorAddr FixupAddress,
125 const char *FixupContent, object::relocation_iterator &UnsignedRelItr,
126 object::relocation_iterator &RelEnd) {
127 using namespace support;
128
129 assert(((SubtractorKind == MachOSubtractor32 && SubRI.r_length == 2) ||
130 (SubtractorKind == MachOSubtractor64 && SubRI.r_length == 3)) &&
131 "Subtractor kind should match length");
132 assert(SubRI.r_extern && "SUBTRACTOR reloc symbol should be extern");
133 assert(!SubRI.r_pcrel && "SUBTRACTOR reloc should not be PCRel");
134
135 if (UnsignedRelItr == RelEnd)
136 return make_error<JITLinkError>(Args: "x86_64 SUBTRACTOR without paired "
137 "UNSIGNED relocation");
138
139 auto UnsignedRI = getRelocationInfo(RelItr: UnsignedRelItr);
140
141 if (SubRI.r_address != UnsignedRI.r_address)
142 return make_error<JITLinkError>(Args: "x86_64 SUBTRACTOR and paired UNSIGNED "
143 "point to different addresses");
144
145 if (SubRI.r_length != UnsignedRI.r_length)
146 return make_error<JITLinkError>(Args: "length of x86_64 SUBTRACTOR and paired "
147 "UNSIGNED reloc must match");
148
149 Symbol *FromSymbol;
150 if (auto FromSymbolOrErr = findSymbolByIndex(Index: SubRI.r_symbolnum))
151 FromSymbol = FromSymbolOrErr->GraphSymbol;
152 else
153 return FromSymbolOrErr.takeError();
154
155 // Read the current fixup value.
156 uint64_t FixupValue = 0;
157 if (SubRI.r_length == 3)
158 FixupValue = *(const little64_t *)FixupContent;
159 else
160 FixupValue = *(const little32_t *)FixupContent;
161
162 // Find 'ToSymbol' using symbol number or address, depending on whether the
163 // paired UNSIGNED relocation is extern.
164 Symbol *ToSymbol = nullptr;
165 if (UnsignedRI.r_extern) {
166 // Find target symbol by symbol index.
167 if (auto ToSymbolOrErr = findSymbolByIndex(Index: UnsignedRI.r_symbolnum))
168 ToSymbol = ToSymbolOrErr->GraphSymbol;
169 else
170 return ToSymbolOrErr.takeError();
171 } else {
172 auto ToSymbolSec = findSectionByIndex(Index: UnsignedRI.r_symbolnum - 1);
173 if (!ToSymbolSec)
174 return ToSymbolSec.takeError();
175 ToSymbol = getSymbolByAddress(NSec&: *ToSymbolSec, Address: ToSymbolSec->Address);
176 assert(ToSymbol && "No symbol for section");
177 FixupValue -= ToSymbol->getAddress().getValue();
178 }
179
180 Edge::Kind DeltaKind;
181 Symbol *TargetSymbol;
182 uint64_t Addend;
183
184 bool FixingFromSymbol = true;
185 if (&BlockToFix == &FromSymbol->getAddressable()) {
186 if (LLVM_UNLIKELY(&BlockToFix == &ToSymbol->getAddressable())) {
187 // From and To are symbols in the same block. Decide direction by offset
188 // instead.
189 if (ToSymbol->getAddress() > FixupAddress)
190 FixingFromSymbol = true;
191 else if (FromSymbol->getAddress() > FixupAddress)
192 FixingFromSymbol = false;
193 else
194 FixingFromSymbol = FromSymbol->getAddress() >= ToSymbol->getAddress();
195 } else
196 FixingFromSymbol = true;
197 } else {
198 if (&BlockToFix == &ToSymbol->getAddressable())
199 FixingFromSymbol = false;
200 else {
201 // BlockToFix was neither FromSymbol nor ToSymbol.
202 return make_error<JITLinkError>(Args: "SUBTRACTOR relocation must fix up "
203 "either 'A' or 'B' (or a symbol in one "
204 "of their alt-entry groups)");
205 }
206 }
207
208 if (FixingFromSymbol) {
209 TargetSymbol = ToSymbol;
210 DeltaKind = (SubRI.r_length == 3) ? x86_64::Delta64 : x86_64::Delta32;
211 Addend = FixupValue + (FixupAddress - FromSymbol->getAddress());
212 // FIXME: handle extern 'from'.
213 } else {
214 TargetSymbol = FromSymbol;
215 DeltaKind =
216 (SubRI.r_length == 3) ? x86_64::NegDelta64 : x86_64::NegDelta32;
217 Addend = FixupValue - (FixupAddress - ToSymbol->getAddress());
218 }
219
220 return PairRelocInfo(DeltaKind, TargetSymbol, Addend);
221 }
222
223 Error addRelocations() override {
224 using namespace support;
225 auto &Obj = getObject();
226
227 LLVM_DEBUG(dbgs() << "Processing relocations:\n");
228
229 for (const auto &S : Obj.sections()) {
230
231 orc::ExecutorAddr SectionAddress(S.getAddress());
232
233 // Skip relocations virtual sections.
234 if (S.isVirtual()) {
235 if (S.relocation_begin() != S.relocation_end())
236 return make_error<JITLinkError>(Args: "Virtual section contains "
237 "relocations");
238 continue;
239 }
240
241 auto NSec =
242 findSectionByIndex(Index: Obj.getSectionIndex(Sec: S.getRawDataRefImpl()));
243 if (!NSec)
244 return NSec.takeError();
245
246 // Skip relocations for MachO sections without corresponding graph
247 // sections.
248 {
249 if (!NSec->GraphSection) {
250 LLVM_DEBUG({
251 dbgs() << " Skipping relocations for MachO section "
252 << NSec->SegName << "/" << NSec->SectName
253 << " which has no associated graph section\n";
254 });
255 continue;
256 }
257 }
258
259 // Add relocations for section.
260 for (auto RelItr = S.relocation_begin(), RelEnd = S.relocation_end();
261 RelItr != RelEnd; ++RelItr) {
262
263 MachO::relocation_info RI = getRelocationInfo(RelItr);
264
265 // Find the address of the value to fix up.
266 auto FixupAddress = SectionAddress + (uint32_t)RI.r_address;
267
268 LLVM_DEBUG({
269 dbgs() << " " << NSec->SectName << " + "
270 << formatv("{0:x8}", RI.r_address) << ":\n";
271 });
272
273 // Find the block that the fixup points to.
274 Block *BlockToFix = nullptr;
275 {
276 auto SymbolToFixOrErr = findSymbolByAddress(NSec&: *NSec, Address: FixupAddress);
277 if (!SymbolToFixOrErr)
278 return SymbolToFixOrErr.takeError();
279 BlockToFix = &SymbolToFixOrErr->getBlock();
280 }
281
282 if (FixupAddress + orc::ExecutorAddrDiff(1ULL << RI.r_length) >
283 BlockToFix->getAddress() + BlockToFix->getContent().size())
284 return make_error<JITLinkError>(
285 Args: "Relocation extends past end of fixup block");
286
287 // Get a pointer to the fixup content.
288 const char *FixupContent = BlockToFix->getContent().data() +
289 (FixupAddress - BlockToFix->getAddress());
290
291 size_t FixupOffset = FixupAddress - BlockToFix->getAddress();
292
293 // The target symbol and addend will be populated by the switch below.
294 Symbol *TargetSymbol = nullptr;
295 uint64_t Addend = 0;
296
297 // Validate the relocation kind.
298 auto MachORelocKind = getRelocKind(RI);
299 if (!MachORelocKind)
300 return MachORelocKind.takeError();
301
302 Edge::Kind Kind = Edge::Invalid;
303
304 switch (*MachORelocKind) {
305 case MachOBranch32:
306 if (auto TargetSymbolOrErr = findSymbolByIndex(Index: RI.r_symbolnum))
307 TargetSymbol = TargetSymbolOrErr->GraphSymbol;
308 else
309 return TargetSymbolOrErr.takeError();
310 Addend = *(const little32_t *)FixupContent;
311 Kind = x86_64::BranchPCRel32;
312 break;
313 case MachOPCRel32:
314 if (auto TargetSymbolOrErr = findSymbolByIndex(Index: RI.r_symbolnum))
315 TargetSymbol = TargetSymbolOrErr->GraphSymbol;
316 else
317 return TargetSymbolOrErr.takeError();
318 Addend = *(const little32_t *)FixupContent - 4;
319 Kind = x86_64::Delta32;
320 break;
321 case MachOPCRel32GOTLoad:
322 if (auto TargetSymbolOrErr = findSymbolByIndex(Index: RI.r_symbolnum))
323 TargetSymbol = TargetSymbolOrErr->GraphSymbol;
324 else
325 return TargetSymbolOrErr.takeError();
326 Addend = *(const little32_t *)FixupContent;
327 Kind = x86_64::RequestGOTAndTransformToPCRel32GOTLoadREXRelaxable;
328 if (FixupOffset < 3)
329 return make_error<JITLinkError>(Args: "GOTLD at invalid offset " +
330 formatv(Fmt: "{0}", Vals&: FixupOffset));
331 break;
332 case MachOPCRel32GOT:
333 if (auto TargetSymbolOrErr = findSymbolByIndex(Index: RI.r_symbolnum))
334 TargetSymbol = TargetSymbolOrErr->GraphSymbol;
335 else
336 return TargetSymbolOrErr.takeError();
337 Addend = *(const little32_t *)FixupContent - 4;
338 Kind = x86_64::RequestGOTAndTransformToDelta32;
339 break;
340 case MachOPCRel32TLV:
341 if (auto TargetSymbolOrErr = findSymbolByIndex(Index: RI.r_symbolnum))
342 TargetSymbol = TargetSymbolOrErr->GraphSymbol;
343 else
344 return TargetSymbolOrErr.takeError();
345 Addend = *(const little32_t *)FixupContent;
346 Kind = x86_64::RequestTLVPAndTransformToPCRel32TLVPLoadREXRelaxable;
347 if (FixupOffset < 3)
348 return make_error<JITLinkError>(Args: "TLV at invalid offset " +
349 formatv(Fmt: "{0}", Vals&: FixupOffset));
350 break;
351 case MachOPointer32:
352 if (auto TargetSymbolOrErr = findSymbolByIndex(Index: RI.r_symbolnum))
353 TargetSymbol = TargetSymbolOrErr->GraphSymbol;
354 else
355 return TargetSymbolOrErr.takeError();
356 Addend = *(const ulittle32_t *)FixupContent;
357 Kind = x86_64::Pointer32;
358 break;
359 case MachOPointer64:
360 if (auto TargetSymbolOrErr = findSymbolByIndex(Index: RI.r_symbolnum))
361 TargetSymbol = TargetSymbolOrErr->GraphSymbol;
362 else
363 return TargetSymbolOrErr.takeError();
364 Addend = *(const ulittle64_t *)FixupContent;
365 Kind = x86_64::Pointer64;
366 break;
367 case MachOPointer64Anon: {
368 orc::ExecutorAddr TargetAddress(*(const ulittle64_t *)FixupContent);
369 auto TargetNSec = findSectionByIndex(Index: RI.r_symbolnum - 1);
370 if (!TargetNSec)
371 return TargetNSec.takeError();
372 if (auto TargetSymbolOrErr =
373 findSymbolByAddress(NSec&: *TargetNSec, Address: TargetAddress))
374 TargetSymbol = &*TargetSymbolOrErr;
375 else
376 return TargetSymbolOrErr.takeError();
377 Addend = TargetAddress - TargetSymbol->getAddress();
378 Kind = x86_64::Pointer64;
379 break;
380 }
381 case MachOPCRel32Minus1:
382 case MachOPCRel32Minus2:
383 case MachOPCRel32Minus4:
384 if (auto TargetSymbolOrErr = findSymbolByIndex(Index: RI.r_symbolnum))
385 TargetSymbol = TargetSymbolOrErr->GraphSymbol;
386 else
387 return TargetSymbolOrErr.takeError();
388 Addend = *(const little32_t *)FixupContent - 4;
389 Kind = x86_64::Delta32;
390 break;
391 case MachOPCRel32Anon: {
392 orc::ExecutorAddr TargetAddress(FixupAddress + 4 +
393 *(const little32_t *)FixupContent);
394 auto TargetNSec = findSectionByIndex(Index: RI.r_symbolnum - 1);
395 if (!TargetNSec)
396 return TargetNSec.takeError();
397 if (auto TargetSymbolOrErr =
398 findSymbolByAddress(NSec&: *TargetNSec, Address: TargetAddress))
399 TargetSymbol = &*TargetSymbolOrErr;
400 else
401 return TargetSymbolOrErr.takeError();
402 Addend = TargetAddress - TargetSymbol->getAddress() - 4;
403 Kind = x86_64::Delta32;
404 break;
405 }
406 case MachOPCRel32Minus1Anon:
407 case MachOPCRel32Minus2Anon:
408 case MachOPCRel32Minus4Anon: {
409 orc::ExecutorAddrDiff Delta =
410 4 + orc::ExecutorAddrDiff(
411 1ULL << (*MachORelocKind - MachOPCRel32Minus1Anon));
412 orc::ExecutorAddr TargetAddress =
413 FixupAddress + Delta + *(const little32_t *)FixupContent;
414 auto TargetNSec = findSectionByIndex(Index: RI.r_symbolnum - 1);
415 if (!TargetNSec)
416 return TargetNSec.takeError();
417 if (auto TargetSymbolOrErr =
418 findSymbolByAddress(NSec&: *TargetNSec, Address: TargetAddress))
419 TargetSymbol = &*TargetSymbolOrErr;
420 else
421 return TargetSymbolOrErr.takeError();
422 Addend = TargetAddress - TargetSymbol->getAddress() - Delta;
423 Kind = x86_64::Delta32;
424 break;
425 }
426 case MachOSubtractor32:
427 case MachOSubtractor64: {
428 // We use Delta32/Delta64 to represent SUBTRACTOR relocations.
429 // parsePairRelocation handles the paired reloc, and returns the
430 // edge kind to be used (either Delta32/Delta64, or
431 // NegDelta32/NegDelta64, depending on the direction of the
432 // subtraction) along with the addend.
433 auto PairInfo =
434 parsePairRelocation(BlockToFix&: *BlockToFix, SubtractorKind: *MachORelocKind, SubRI: RI,
435 FixupAddress, FixupContent, UnsignedRelItr&: ++RelItr, RelEnd);
436 if (!PairInfo)
437 return PairInfo.takeError();
438 std::tie(args&: Kind, args&: TargetSymbol, args&: Addend) = *PairInfo;
439 assert(TargetSymbol && "No target symbol from parsePairRelocation?");
440 break;
441 }
442 }
443
444 LLVM_DEBUG({
445 dbgs() << " ";
446 Edge GE(Kind, FixupAddress - BlockToFix->getAddress(), *TargetSymbol,
447 Addend);
448 printEdge(dbgs(), *BlockToFix, GE, x86_64::getEdgeKindName(Kind));
449 dbgs() << "\n";
450 });
451 BlockToFix->addEdge(K: Kind, Offset: FixupAddress - BlockToFix->getAddress(),
452 Target&: *TargetSymbol, Addend);
453 }
454 }
455 return Error::success();
456 }
457};
458
459Error buildGOTAndStubs_MachO_x86_64(LinkGraph &G) {
460 x86_64::GOTTableManager GOT;
461 x86_64::PLTTableManager PLT(GOT);
462 visitExistingEdges(G, Vs&: GOT, Vs&: PLT);
463 return Error::success();
464}
465
466} // namespace
467
468namespace llvm {
469namespace jitlink {
470
471class MachOJITLinker_x86_64 : public JITLinker<MachOJITLinker_x86_64> {
472 friend class JITLinker<MachOJITLinker_x86_64>;
473
474public:
475 MachOJITLinker_x86_64(std::unique_ptr<JITLinkContext> Ctx,
476 std::unique_ptr<LinkGraph> G,
477 PassConfiguration PassConfig)
478 : JITLinker(std::move(Ctx), std::move(G), std::move(PassConfig)) {}
479
480private:
481 Error applyFixup(LinkGraph &G, Block &B, const Edge &E) const {
482 return x86_64::applyFixup(G, B, E, GOTSymbol: nullptr);
483 }
484};
485
486Expected<std::unique_ptr<LinkGraph>>
487createLinkGraphFromMachOObject_x86_64(MemoryBufferRef ObjectBuffer) {
488 auto MachOObj = object::ObjectFile::createMachOObjectFile(Object: ObjectBuffer);
489 if (!MachOObj)
490 return MachOObj.takeError();
491
492 auto Features = (*MachOObj)->getFeatures();
493 if (!Features)
494 return Features.takeError();
495
496 return MachOLinkGraphBuilder_x86_64(**MachOObj, std::move(*Features))
497 .buildGraph();
498}
499
500void link_MachO_x86_64(std::unique_ptr<LinkGraph> G,
501 std::unique_ptr<JITLinkContext> Ctx) {
502
503 PassConfiguration Config;
504
505 if (Ctx->shouldAddDefaultTargetPasses(TT: G->getTargetTriple())) {
506 // Add eh-frame passes.
507 Config.PrePrunePasses.push_back(x: createEHFrameSplitterPass_MachO_x86_64());
508 Config.PrePrunePasses.push_back(x: createEHFrameEdgeFixerPass_MachO_x86_64());
509
510 // Add compact unwind splitter pass.
511 Config.PrePrunePasses.push_back(
512 x: CompactUnwindSplitter("__LD,__compact_unwind"));
513
514 // Add a mark-live pass.
515 if (auto MarkLive = Ctx->getMarkLivePass(TT: G->getTargetTriple()))
516 Config.PrePrunePasses.push_back(x: std::move(MarkLive));
517 else
518 Config.PrePrunePasses.push_back(x: markAllSymbolsLive);
519
520 // Resolve any external section start / end symbols.
521 Config.PostAllocationPasses.push_back(
522 x: createDefineExternalSectionStartAndEndSymbolsPass(
523 F&: identifyMachOSectionStartAndEndSymbols));
524
525 // Add an in-place GOT/Stubs pass.
526 Config.PostPrunePasses.push_back(x: buildGOTAndStubs_MachO_x86_64);
527
528 // Add GOT/Stubs optimizer pass.
529 Config.PreFixupPasses.push_back(x: x86_64::optimizeGOTAndStubAccesses);
530 }
531
532 if (auto Err = Ctx->modifyPassConfig(G&: *G, Config))
533 return Ctx->notifyFailed(Err: std::move(Err));
534
535 // Construct a JITLinker and run the link function.
536 MachOJITLinker_x86_64::link(Args: std::move(Ctx), Args: std::move(G), Args: std::move(Config));
537}
538
539LinkGraphPassFunction createEHFrameSplitterPass_MachO_x86_64() {
540 return DWARFRecordSectionSplitter("__TEXT,__eh_frame");
541}
542
543LinkGraphPassFunction createEHFrameEdgeFixerPass_MachO_x86_64() {
544 return EHFrameEdgeFixer("__TEXT,__eh_frame", x86_64::PointerSize,
545 x86_64::Pointer32, x86_64::Pointer64, x86_64::Delta32,
546 x86_64::Delta64, x86_64::NegDelta32);
547}
548
549} // end namespace jitlink
550} // end namespace llvm
551