lld/COFF/Chunks.h

   1 //===- Chunks.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_COFF_CHUNKS_H
  10 #define LLD_COFF_CHUNKS_H
  11
  12 #include "Config.h"
  13 #include "InputFiles.h"
  14 #include "lld/Common/LLVM.h"
  15 #include "llvm/ADT/ArrayRef.h"
  16 #include "llvm/ADT/PointerIntPair.h"
  17 #include "llvm/ADT/iterator.h"
  18 #include "llvm/ADT/iterator_range.h"
  19 #include "llvm/MC/StringTableBuilder.h"
  20 #include "llvm/Object/COFF.h"
  21 #include <utility>
  22 #include <vector>
  23
  24 namespace lld {
  25 namespace coff {
  26
  27 using llvm::COFF::ImportDirectoryTableEntry;
  28 using llvm::object::COFFSymbolRef;
  29 using llvm::object::SectionRef;
  30 using llvm::object::coff_relocation;
  31 using llvm::object::coff_section;
  32
  33 class Baserel;
  34 class Defined;
  35 class DefinedImportData;
  36 class DefinedRegular;
  37 class ObjFile;
  38 class OutputSection;
  39 class RuntimePseudoReloc;
  40 class Symbol;
  41
  42 // Mask for permissions (discardable, writable, readable, executable, etc).
  43 const uint32_t permMask = 0xFE000000;
  44
  45 // Mask for section types (code, data, bss).
  46 const uint32_t typeMask = 0x000000E0;
  47
  48 // The log base 2 of the largest section alignment, which is log2(8192), or 13.
  49 enum : unsigned { Log2MaxSectionAlignment = 13 };
  50
  51 // A Chunk represents a chunk of data that will occupy space in the
  52 // output (if the resolver chose that). It may or may not be backed by
  53 // a section of an input file. It could be linker-created data, or
  54 // doesn't even have actual data (if common or bss).
  55 class Chunk {
  56 public:
  57   enum Kind : uint8_t { SectionKind, OtherKind, ImportThunkKind };
  58   Kind kind() const { return chunkKind; }
  59
  60   // Returns the size of this chunk (even if this is a common or BSS.)
  61   size_t getSize() const;
  62
  63   // Returns chunk alignment in power of two form. Value values are powers of
  64   // two from 1 to 8192.
  65   uint32_t getAlignment() const { return 1U << p2Align; }
  66
  67   // Update the chunk section alignment measured in bytes. Internally alignment
  68   // is stored in log2.
  69   void setAlignment(uint32_t align) {
  70     // Treat zero byte alignment as 1 byte alignment.
  71     align = align ? align : 1;
  72     assert(llvm::isPowerOf2_32(align) && "alignment is not a power of 2");
  73     p2Align = llvm::Log2_32(align);
  74     assert(p2Align <= Log2MaxSectionAlignment &&
  75            "impossible requested alignment");
  76   }
  77
  78   // Write this chunk to a mmap'ed file, assuming Buf is pointing to
  79   // beginning of the file. Because this function may use RVA values
  80   // of other chunks for relocations, you need to set them properly
  81   // before calling this function.
  82   void writeTo(uint8_t *buf) const;
  83
  84   // The writer sets and uses the addresses. In practice, PE images cannot be
  85   // larger than 2GB. Chunks are always laid as part of the image, so Chunk RVAs
  86   // can be stored with 32 bits.
  87   uint32_t getRVA() const { return rva; }
  88   void setRVA(uint64_t v) {
  89     rva = (uint32_t)v;
  90     assert(rva == v && "RVA truncated");
  91   }
  92
  93   // Returns readable/writable/executable bits.
  94   uint32_t getOutputCharacteristics() const;
  95
  96   // Returns the section name if this is a section chunk.
  97   // It is illegal to call this function on non-section chunks.
  98   StringRef getSectionName() const;
  99
 100   // An output section has pointers to chunks in the section, and each
 101   // chunk has a back pointer to an output section.
 102   void setOutputSectionIdx(uint16_t o) { osidx = o; }
 103   uint16_t getOutputSectionIdx() const { return osidx; }
 104   OutputSection *getOutputSection() const;
 105
 106   // Windows-specific.
 107   // Collect all locations that contain absolute addresses for base relocations.
 108   void getBaserels(std::vector<Baserel> *res);
 109
 110   // Returns a human-readable name of this chunk. Chunks are unnamed chunks of
 111   // bytes, so this is used only for logging or debugging.
 112   StringRef getDebugName() const;
 113
 114   // Return true if this file has the hotpatch flag set to true in the
 115   // S_COMPILE3 record in codeview debug info. Also returns true for some thunks
 116   // synthesized by the linker.
 117   bool isHotPatchable() const;
 118
 119 protected:
 120   Chunk(Kind k = OtherKind) : chunkKind(k), hasData(true), p2Align(0) {}
 121
 122   const Kind chunkKind;
 123
 124 public:
 125   // Returns true if this has non-zero data. BSS chunks return
 126   // false. If false is returned, the space occupied by this chunk
 127   // will be filled with zeros. Corresponds to the
 128   // IMAGE_SCN_CNT_UNINITIALIZED_DATA section characteristic bit.
 129   uint8_t hasData : 1;
 130
 131 public:
 132   // The alignment of this chunk, stored in log2 form. The writer uses the
 133   // value.
 134   uint8_t p2Align : 7;
 135
 136   // The output section index for this chunk. The first valid section number is
 137   // one.
 138   uint16_t osidx = 0;
 139
 140   // The RVA of this chunk in the output. The writer sets a value.
 141   uint32_t rva = 0;
 142 };
 143
 144 class NonSectionChunk : public Chunk {
 145 public:
 146   virtual ~NonSectionChunk() = default;
 147
 148   // Returns the size of this chunk (even if this is a common or BSS.)
 149   virtual size_t getSize() const = 0;
 150
 151   virtual uint32_t getOutputCharacteristics() const { return 0; }
 152
 153   // Write this chunk to a mmap'ed file, assuming Buf is pointing to
 154   // beginning of the file. Because this function may use RVA values
 155   // of other chunks for relocations, you need to set them properly
 156   // before calling this function.
 157   virtual void writeTo(uint8_t *buf) const {}
 158
 159   // Returns the section name if this is a section chunk.
 160   // It is illegal to call this function on non-section chunks.
 161   virtual StringRef getSectionName() const {
 162     llvm_unreachable("unimplemented getSectionName");
 163   }
 164
 165   // Windows-specific.
 166   // Collect all locations that contain absolute addresses for base relocations.
 167   virtual void getBaserels(std::vector<Baserel> *res) {}
 168
 169   // Returns a human-readable name of this chunk. Chunks are unnamed chunks of
 170   // bytes, so this is used only for logging or debugging.
 171   virtual StringRef getDebugName() const { return ""; }
 172
 173   static bool classof(const Chunk *c) { return c->kind() != SectionKind; }
 174
 175 protected:
 176   NonSectionChunk(Kind k = OtherKind) : Chunk(k) {}
 177 };
 178
 179 // A chunk corresponding a section of an input file.
 180 class SectionChunk final : public Chunk {
 181   // Identical COMDAT Folding feature accesses section internal data.
 182   friend class ICF;
 183
 184 public:
 185   class symbol_iterator : public llvm::iterator_adaptor_base<
 186                               symbol_iterator, const coff_relocation *,
 187                               std::random_access_iterator_tag, Symbol *> {
 188     friend SectionChunk;
 189
 190     ObjFile *file;
 191
 192     symbol_iterator(ObjFile *file, const coff_relocation *i)
 193         : symbol_iterator::iterator_adaptor_base(i), file(file) {}
 194
 195   public:
 196     symbol_iterator() = default;
 197
 198     Symbol *operator*() const { return file->getSymbol(I->SymbolTableIndex); }
 199   };
 200
 201   SectionChunk(ObjFile *file, const coff_section *header);
 202   static bool classof(const Chunk *c) { return c->kind() == SectionKind; }
 203   size_t getSize() const { return header->SizeOfRawData; }
 204   ArrayRef<uint8_t> getContents() const;
 205   void writeTo(uint8_t *buf) const;
 206
 207   uint32_t getOutputCharacteristics() const {
 208     return header->Characteristics & (permMask | typeMask);
 209   }
 210   StringRef getSectionName() const {
 211     return StringRef(sectionNameData, sectionNameSize);
 212   }
 213   void getBaserels(std::vector<Baserel> *res);
 214   bool isCOMDAT() const;
 215   void applyRelX64(uint8_t *off, uint16_t type, OutputSection *os, uint64_t s,
 216                    uint64_t p) const;
 217   void applyRelX86(uint8_t *off, uint16_t type, OutputSection *os, uint64_t s,
 218                    uint64_t p) const;
 219   void applyRelARM(uint8_t *off, uint16_t type, OutputSection *os, uint64_t s,
 220                    uint64_t p) const;
 221   void applyRelARM64(uint8_t *off, uint16_t type, OutputSection *os, uint64_t s,
 222                      uint64_t p) const;
 223
 224   void getRuntimePseudoRelocs(std::vector<RuntimePseudoReloc> &res);
 225
 226   // Called if the garbage collector decides to not include this chunk
 227   // in a final output. It's supposed to print out a log message to stdout.
 228   void printDiscardedMessage() const;
 229
 230   // Adds COMDAT associative sections to this COMDAT section. A chunk
 231   // and its children are treated as a group by the garbage collector.
 232   void addAssociative(SectionChunk *child);
 233
 234   StringRef getDebugName() const;
 235
 236   // True if this is a codeview debug info chunk. These will not be laid out in
 237   // the image. Instead they will end up in the PDB, if one is requested.
 238   bool isCodeView() const {
 239     return getSectionName() == ".debug" || getSectionName().startswith(".debug$");
 240   }
 241
 242   // True if this is a DWARF debug info or exception handling chunk.
 243   bool isDWARF() const {
 244     return getSectionName().startswith(".debug_") || getSectionName() == ".eh_frame";
 245   }
 246
 247   // Allow iteration over the bodies of this chunk's relocated symbols.
 248   llvm::iterator_range<symbol_iterator> symbols() const {
 249     return llvm::make_range(symbol_iterator(file, relocsData),
 250                             symbol_iterator(file, relocsData + relocsSize));
 251   }
 252
 253   ArrayRef<coff_relocation> getRelocs() const {
 254     return llvm::makeArrayRef(relocsData, relocsSize);
 255   }
 256
 257   // Reloc setter used by ARM range extension thunk insertion.
 258   void setRelocs(ArrayRef<coff_relocation> newRelocs) {
 259     relocsData = newRelocs.data();
 260     relocsSize = newRelocs.size();
 261     assert(relocsSize == newRelocs.size() && "reloc size truncation");
 262   }
 263
 264   // Single linked list iterator for associated comdat children.
 265   class AssociatedIterator
 266       : public llvm::iterator_facade_base<
 267             AssociatedIterator, std::forward_iterator_tag, SectionChunk> {
 268   public:
 269     AssociatedIterator() = default;
 270     AssociatedIterator(SectionChunk *head) : cur(head) {}
 271     bool operator==(const AssociatedIterator &r) const { return cur == r.cur; }
 272     // FIXME: Wrong const-ness, but it makes filter ranges work.
 273     SectionChunk &operator*() const { return *cur; }
 274     SectionChunk &operator*() { return *cur; }
 275     AssociatedIterator &operator++() {
 276       cur = cur->assocChildren;
 277       return *this;
 278     }
 279
 280   private:
 281     SectionChunk *cur = nullptr;
 282   };
 283
 284   // Allow iteration over the associated child chunks for this section.
 285   llvm::iterator_range<AssociatedIterator> children() const {
 286     return llvm::make_range(AssociatedIterator(assocChildren),
 287                             AssociatedIterator(nullptr));
 288   }
 289
 290   // The section ID this chunk belongs to in its Obj.
 291   uint32_t getSectionNumber() const;
 292
 293   ArrayRef<uint8_t> consumeDebugMagic();
 294
 295   static ArrayRef<uint8_t> consumeDebugMagic(ArrayRef<uint8_t> data,
 296                                              StringRef sectionName);
 297
 298   static SectionChunk *findByName(ArrayRef<SectionChunk *> sections,
 299                                   StringRef name);
 300
 301   // The file that this chunk was created from.
 302   ObjFile *file;
 303
 304   // Pointer to the COFF section header in the input file.
 305   const coff_section *header;
 306
 307   // The COMDAT leader symbol if this is a COMDAT chunk.
 308   DefinedRegular *sym = nullptr;
 309
 310   // The CRC of the contents as described in the COFF spec 4.5.5.
 311   // Auxiliary Format 5: Section Definitions. Used for ICF.
 312   uint32_t checksum = 0;
 313
 314   // Used by the garbage collector.
 315   bool live;
 316
 317   // Whether this section needs to be kept distinct from other sections during
 318   // ICF. This is set by the driver using address-significance tables.
 319   bool keepUnique = false;
 320
 321   // The COMDAT selection if this is a COMDAT chunk.
 322   llvm::COFF::COMDATType selection = (llvm::COFF::COMDATType)0;
 323
 324   // A pointer pointing to a replacement for this chunk.
 325   // Initially it points to "this" object. If this chunk is merged
 326   // with other chunk by ICF, it points to another chunk,
 327   // and this chunk is considered as dead.
 328   SectionChunk *repl;
 329
 330 private:
 331   SectionChunk *assocChildren = nullptr;
 332
 333   // Used for ICF (Identical COMDAT Folding)
 334   void replace(SectionChunk *other);
 335   uint32_t eqClass[2] = {0, 0};
 336
 337   // Relocations for this section. Size is stored below.
 338   const coff_relocation *relocsData;
 339
 340   // Section name string. Size is stored below.
 341   const char *sectionNameData;
 342
 343   uint32_t relocsSize = 0;
 344   uint32_t sectionNameSize = 0;
 345 };
 346
 347 // Inline methods to implement faux-virtual dispatch for SectionChunk.
 348
 349 inline size_t Chunk::getSize() const {
 350   if (isa<SectionChunk>(this))
 351     return static_cast<const SectionChunk *>(this)->getSize();
 352   else
 353     return static_cast<const NonSectionChunk *>(this)->getSize();
 354 }
 355
 356 inline uint32_t Chunk::getOutputCharacteristics() const {
 357   if (isa<SectionChunk>(this))
 358     return static_cast<const SectionChunk *>(this)->getOutputCharacteristics();
 359   else
 360     return static_cast<const NonSectionChunk *>(this)
 361         ->getOutputCharacteristics();
 362 }
 363
 364 inline void Chunk::writeTo(uint8_t *buf) const {
 365   if (isa<SectionChunk>(this))
 366     static_cast<const SectionChunk *>(this)->writeTo(buf);
 367   else
 368     static_cast<const NonSectionChunk *>(this)->writeTo(buf);
 369 }
 370
 371 inline StringRef Chunk::getSectionName() const {
 372   if (isa<SectionChunk>(this))
 373     return static_cast<const SectionChunk *>(this)->getSectionName();
 374   else
 375     return static_cast<const NonSectionChunk *>(this)->getSectionName();
 376 }
 377
 378 inline void Chunk::getBaserels(std::vector<Baserel> *res) {
 379   if (isa<SectionChunk>(this))
 380     static_cast<SectionChunk *>(this)->getBaserels(res);
 381   else
 382     static_cast<NonSectionChunk *>(this)->getBaserels(res);
 383 }
 384
 385 inline StringRef Chunk::getDebugName() const {
 386   if (isa<SectionChunk>(this))
 387     return static_cast<const SectionChunk *>(this)->getDebugName();
 388   else
 389     return static_cast<const NonSectionChunk *>(this)->getDebugName();
 390 }
 391
 392 // This class is used to implement an lld-specific feature (not implemented in
 393 // MSVC) that minimizes the output size by finding string literals sharing tail
 394 // parts and merging them.
 395 //
 396 // If string tail merging is enabled and a section is identified as containing a
 397 // string literal, it is added to a MergeChunk with an appropriate alignment.
 398 // The MergeChunk then tail merges the strings using the StringTableBuilder
 399 // class and assigns RVAs and section offsets to each of the member chunks based
 400 // on the offsets assigned by the StringTableBuilder.
 401 class MergeChunk : public NonSectionChunk {
 402 public:
 403   MergeChunk(uint32_t alignment);
 404   static void addSection(SectionChunk *c);
 405   void finalizeContents();
 406   void assignSubsectionRVAs();
 407
 408   uint32_t getOutputCharacteristics() const override;
 409   StringRef getSectionName() const override { return ".rdata"; }
 410   size_t getSize() const override;
 411   void writeTo(uint8_t *buf) const override;
 412
 413   static MergeChunk *instances[Log2MaxSectionAlignment + 1];
 414   std::vector<SectionChunk *> sections;
 415
 416 private:
 417   llvm::StringTableBuilder builder;
 418   bool finalized = false;
 419 };
 420
 421 // A chunk for common symbols. Common chunks don't have actual data.
 422 class CommonChunk : public NonSectionChunk {
 423 public:
 424   CommonChunk(const COFFSymbolRef sym);
 425   size_t getSize() const override { return sym.getValue(); }
 426   uint32_t getOutputCharacteristics() const override;
 427   StringRef getSectionName() const override { return ".bss"; }
 428
 429 private:
 430   const COFFSymbolRef sym;
 431 };
 432
 433 // A chunk for linker-created strings.
 434 class StringChunk : public NonSectionChunk {
 435 public:
 436   explicit StringChunk(StringRef s) : str(s) {}
 437   size_t getSize() const override { return str.size() + 1; }
 438   void writeTo(uint8_t *buf) const override;
 439
 440 private:
 441   StringRef str;
 442 };
 443
 444 static const uint8_t importThunkX86[] = {
 445     0xff, 0x25, 0x00, 0x00, 0x00, 0x00, // JMP *0x0
 446 };
 447
 448 static const uint8_t importThunkARM[] = {
 449     0x40, 0xf2, 0x00, 0x0c, // mov.w ip, #0
 450     0xc0, 0xf2, 0x00, 0x0c, // mov.t ip, #0
 451     0xdc, 0xf8, 0x00, 0xf0, // ldr.w pc, [ip]
 452 };
 453
 454 static const uint8_t importThunkARM64[] = {
 455     0x10, 0x00, 0x00, 0x90, // adrp x16, #0
 456     0x10, 0x02, 0x40, 0xf9, // ldr  x16, [x16]
 457     0x00, 0x02, 0x1f, 0xd6, // br   x16
 458 };
 459
 460 // Windows-specific.
 461 // A chunk for DLL import jump table entry. In a final output, its
 462 // contents will be a JMP instruction to some __imp_ symbol.
 463 class ImportThunkChunk : public NonSectionChunk {
 464 public:
 465   ImportThunkChunk(Defined *s)
 466       : NonSectionChunk(ImportThunkKind), impSymbol(s) {}
 467   static bool classof(const Chunk *c) { return c->kind() == ImportThunkKind; }
 468
 469 protected:
 470   Defined *impSymbol;
 471 };
 472
 473 class ImportThunkChunkX64 : public ImportThunkChunk {
 474 public:
 475   explicit ImportThunkChunkX64(Defined *s);
 476   size_t getSize() const override { return sizeof(importThunkX86); }
 477   void writeTo(uint8_t *buf) const override;
 478 };
 479
 480 class ImportThunkChunkX86 : public ImportThunkChunk {
 481 public:
 482   explicit ImportThunkChunkX86(Defined *s) : ImportThunkChunk(s) {}
 483   size_t getSize() const override { return sizeof(importThunkX86); }
 484   void getBaserels(std::vector<Baserel> *res) override;
 485   void writeTo(uint8_t *buf) const override;
 486 };
 487
 488 class ImportThunkChunkARM : public ImportThunkChunk {
 489 public:
 490   explicit ImportThunkChunkARM(Defined *s) : ImportThunkChunk(s) {
 491     setAlignment(2);
 492   }
 493   size_t getSize() const override { return sizeof(importThunkARM); }
 494   void getBaserels(std::vector<Baserel> *res) override;
 495   void writeTo(uint8_t *buf) const override;
 496 };
 497
 498 class ImportThunkChunkARM64 : public ImportThunkChunk {
 499 public:
 500   explicit ImportThunkChunkARM64(Defined *s) : ImportThunkChunk(s) {
 501     setAlignment(4);
 502   }
 503   size_t getSize() const override { return sizeof(importThunkARM64); }
 504   void writeTo(uint8_t *buf) const override;
 505 };
 506
 507 class RangeExtensionThunkARM : public NonSectionChunk {
 508 public:
 509   explicit RangeExtensionThunkARM(Defined *t) : target(t) { setAlignment(2); }
 510   size_t getSize() const override;
 511   void writeTo(uint8_t *buf) const override;
 512
 513   Defined *target;
 514 };
 515
 516 class RangeExtensionThunkARM64 : public NonSectionChunk {
 517 public:
 518   explicit RangeExtensionThunkARM64(Defined *t) : target(t) { setAlignment(4); }
 519   size_t getSize() const override;
 520   void writeTo(uint8_t *buf) const override;
 521
 522   Defined *target;
 523 };
 524
 525 // Windows-specific.
 526 // See comments for DefinedLocalImport class.
 527 class LocalImportChunk : public NonSectionChunk {
 528 public:
 529   explicit LocalImportChunk(Defined *s) : sym(s) {
 530     setAlignment(config->wordsize);
 531   }
 532   size_t getSize() const override;
 533   void getBaserels(std::vector<Baserel> *res) override;
 534   void writeTo(uint8_t *buf) const override;
 535
 536 private:
 537   Defined *sym;
 538 };
 539
 540 // Duplicate RVAs are not allowed in RVA tables, so unique symbols by chunk and
 541 // offset into the chunk. Order does not matter as the RVA table will be sorted
 542 // later.
 543 struct ChunkAndOffset {
 544   Chunk *inputChunk;
 545   uint32_t offset;
 546
 547   struct DenseMapInfo {
 548     static ChunkAndOffset getEmptyKey() {
 549       return {llvm::DenseMapInfo<Chunk *>::getEmptyKey(), 0};
 550     }
 551     static ChunkAndOffset getTombstoneKey() {
 552       return {llvm::DenseMapInfo<Chunk *>::getTombstoneKey(), 0};
 553     }
 554     static unsigned getHashValue(const ChunkAndOffset &co) {
 555       return llvm::DenseMapInfo<std::pair<Chunk *, uint32_t>>::getHashValue(
 556           {co.inputChunk, co.offset});
 557     }
 558     static bool isEqual(const ChunkAndOffset &lhs, const ChunkAndOffset &rhs) {
 559       return lhs.inputChunk == rhs.inputChunk && lhs.offset == rhs.offset;
 560     }
 561   };
 562 };
 563
 564 using SymbolRVASet = llvm::DenseSet<ChunkAndOffset>;
 565
 566 // Table which contains symbol RVAs. Used for /safeseh and /guard:cf.
 567 class RVATableChunk : public NonSectionChunk {
 568 public:
 569   explicit RVATableChunk(SymbolRVASet s) : syms(std::move(s)) {}
 570   size_t getSize() const override { return syms.size() * 4; }
 571   void writeTo(uint8_t *buf) const override;
 572
 573 private:
 574   SymbolRVASet syms;
 575 };
 576
 577 // Windows-specific.
 578 // This class represents a block in .reloc section.
 579 // See the PE/COFF spec 5.6 for details.
 580 class BaserelChunk : public NonSectionChunk {
 581 public:
 582   BaserelChunk(uint32_t page, Baserel *begin, Baserel *end);
 583   size_t getSize() const override { return data.size(); }
 584   void writeTo(uint8_t *buf) const override;
 585
 586 private:
 587   std::vector<uint8_t> data;
 588 };
 589
 590 class Baserel {
 591 public:
 592   Baserel(uint32_t v, uint8_t ty) : rva(v), type(ty) {}
 593   explicit Baserel(uint32_t v) : Baserel(v, getDefaultType()) {}
 594   uint8_t getDefaultType();
 595
 596   uint32_t rva;
 597   uint8_t type;
 598 };
 599
 600 // This is a placeholder Chunk, to allow attaching a DefinedSynthetic to a
 601 // specific place in a section, without any data. This is used for the MinGW
 602 // specific symbol __RUNTIME_PSEUDO_RELOC_LIST_END__, even though the concept
 603 // of an empty chunk isn't MinGW specific.
 604 class EmptyChunk : public NonSectionChunk {
 605 public:
 606   EmptyChunk() {}
 607   size_t getSize() const override { return 0; }
 608   void writeTo(uint8_t *buf) const override {}
 609 };
 610
 611 // MinGW specific, for the "automatic import of variables from DLLs" feature.
 612 // This provides the table of runtime pseudo relocations, for variable
 613 // references that turned out to need to be imported from a DLL even though
 614 // the reference didn't use the dllimport attribute. The MinGW runtime will
 615 // process this table after loading, before handling control over to user
 616 // code.
 617 class PseudoRelocTableChunk : public NonSectionChunk {
 618 public:
 619   PseudoRelocTableChunk(std::vector<RuntimePseudoReloc> &relocs)
 620       : relocs(std::move(relocs)) {
 621     setAlignment(4);
 622   }
 623   size_t getSize() const override;
 624   void writeTo(uint8_t *buf) const override;
 625
 626 private:
 627   std::vector<RuntimePseudoReloc> relocs;
 628 };
 629
 630 // MinGW specific; information about one individual location in the image
 631 // that needs to be fixed up at runtime after loading. This represents
 632 // one individual element in the PseudoRelocTableChunk table.
 633 class RuntimePseudoReloc {
 634 public:
 635   RuntimePseudoReloc(Defined *sym, SectionChunk *target, uint32_t targetOffset,
 636                      int flags)
 637       : sym(sym), target(target), targetOffset(targetOffset), flags(flags) {}
 638
 639   Defined *sym;
 640   SectionChunk *target;
 641   uint32_t targetOffset;
 642   // The Flags field contains the size of the relocation, in bits. No other
 643   // flags are currently defined.
 644   int flags;
 645 };
 646
 647 // MinGW specific. A Chunk that contains one pointer-sized absolute value.
 648 class AbsolutePointerChunk : public NonSectionChunk {
 649 public:
 650   AbsolutePointerChunk(uint64_t value) : value(value) {
 651     setAlignment(getSize());
 652   }
 653   size_t getSize() const override;
 654   void writeTo(uint8_t *buf) const override;
 655
 656 private:
 657   uint64_t value;
 658 };
 659
 660 // Return true if this file has the hotpatch flag set to true in the S_COMPILE3
 661 // record in codeview debug info. Also returns true for some thunks synthesized
 662 // by the linker.
 663 inline bool Chunk::isHotPatchable() const {
 664   if (auto *sc = dyn_cast<SectionChunk>(this))
 665     return sc->file->hotPatchable;
 666   else if (isa<ImportThunkChunk>(this))
 667     return true;
 668   return false;
 669 }
 670
 671 void applyMOV32T(uint8_t *off, uint32_t v);
 672 void applyBranch24T(uint8_t *off, int32_t v);
 673
 674 void applyArm64Addr(uint8_t *off, uint64_t s, uint64_t p, int shift);
 675 void applyArm64Imm(uint8_t *off, uint64_t imm, uint32_t rangeLimit);
 676 void applyArm64Branch26(uint8_t *off, int64_t v);
 677
 678 } // namespace coff
 679 } // namespace lld
 680
 681 namespace llvm {
 682 template <>
 683 struct DenseMapInfo<lld::coff::ChunkAndOffset>
 684     : lld::coff::ChunkAndOffset::DenseMapInfo {};
 685 }
 686
 687 #endif