llvm/lib/ExecutionEngine/JITLink/MachO_x86_64.cpp

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