xref: /freebsd/contrib/llvm-project/lld/COFF/Chunks.h (revision 6966ac055c3b7a39266fb982493330df7a097997)
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     AssociatedIterator &operator=(const AssociatedIterator &r) {
272       cur = r.cur;
273       return *this;
274     }
275     bool operator==(const AssociatedIterator &r) const { return cur == r.cur; }
276     const SectionChunk &operator*() const { return *cur; }
277     SectionChunk &operator*() { return *cur; }
278     AssociatedIterator &operator++() {
279       cur = cur->assocChildren;
280       return *this;
281     }
282 
283   private:
284     SectionChunk *cur = nullptr;
285   };
286 
287   // Allow iteration over the associated child chunks for this section.
288   llvm::iterator_range<AssociatedIterator> children() const {
289     return llvm::make_range(AssociatedIterator(assocChildren),
290                             AssociatedIterator(nullptr));
291   }
292 
293   // The section ID this chunk belongs to in its Obj.
294   uint32_t getSectionNumber() const;
295 
296   ArrayRef<uint8_t> consumeDebugMagic();
297 
298   static ArrayRef<uint8_t> consumeDebugMagic(ArrayRef<uint8_t> data,
299                                              StringRef sectionName);
300 
301   static SectionChunk *findByName(ArrayRef<SectionChunk *> sections,
302                                   StringRef name);
303 
304   // The file that this chunk was created from.
305   ObjFile *file;
306 
307   // Pointer to the COFF section header in the input file.
308   const coff_section *header;
309 
310   // The COMDAT leader symbol if this is a COMDAT chunk.
311   DefinedRegular *sym = nullptr;
312 
313   // The CRC of the contents as described in the COFF spec 4.5.5.
314   // Auxiliary Format 5: Section Definitions. Used for ICF.
315   uint32_t checksum = 0;
316 
317   // Used by the garbage collector.
318   bool live;
319 
320   // Whether this section needs to be kept distinct from other sections during
321   // ICF. This is set by the driver using address-significance tables.
322   bool keepUnique = false;
323 
324   // The COMDAT selection if this is a COMDAT chunk.
325   llvm::COFF::COMDATType selection = (llvm::COFF::COMDATType)0;
326 
327   // A pointer pointing to a replacement for this chunk.
328   // Initially it points to "this" object. If this chunk is merged
329   // with other chunk by ICF, it points to another chunk,
330   // and this chunk is considered as dead.
331   SectionChunk *repl;
332 
333 private:
334   SectionChunk *assocChildren = nullptr;
335 
336   // Used for ICF (Identical COMDAT Folding)
337   void replace(SectionChunk *other);
338   uint32_t eqClass[2] = {0, 0};
339 
340   // Relocations for this section. Size is stored below.
341   const coff_relocation *relocsData;
342 
343   // Section name string. Size is stored below.
344   const char *sectionNameData;
345 
346   uint32_t relocsSize = 0;
347   uint32_t sectionNameSize = 0;
348 };
349 
350 // Inline methods to implement faux-virtual dispatch for SectionChunk.
351 
352 inline size_t Chunk::getSize() const {
353   if (isa<SectionChunk>(this))
354     return static_cast<const SectionChunk *>(this)->getSize();
355   else
356     return static_cast<const NonSectionChunk *>(this)->getSize();
357 }
358 
359 inline uint32_t Chunk::getOutputCharacteristics() const {
360   if (isa<SectionChunk>(this))
361     return static_cast<const SectionChunk *>(this)->getOutputCharacteristics();
362   else
363     return static_cast<const NonSectionChunk *>(this)
364         ->getOutputCharacteristics();
365 }
366 
367 inline void Chunk::writeTo(uint8_t *buf) const {
368   if (isa<SectionChunk>(this))
369     static_cast<const SectionChunk *>(this)->writeTo(buf);
370   else
371     static_cast<const NonSectionChunk *>(this)->writeTo(buf);
372 }
373 
374 inline StringRef Chunk::getSectionName() const {
375   if (isa<SectionChunk>(this))
376     return static_cast<const SectionChunk *>(this)->getSectionName();
377   else
378     return static_cast<const NonSectionChunk *>(this)->getSectionName();
379 }
380 
381 inline void Chunk::getBaserels(std::vector<Baserel> *res) {
382   if (isa<SectionChunk>(this))
383     static_cast<SectionChunk *>(this)->getBaserels(res);
384   else
385     static_cast<NonSectionChunk *>(this)->getBaserels(res);
386 }
387 
388 inline StringRef Chunk::getDebugName() const {
389   if (isa<SectionChunk>(this))
390     return static_cast<const SectionChunk *>(this)->getDebugName();
391   else
392     return static_cast<const NonSectionChunk *>(this)->getDebugName();
393 }
394 
395 // This class is used to implement an lld-specific feature (not implemented in
396 // MSVC) that minimizes the output size by finding string literals sharing tail
397 // parts and merging them.
398 //
399 // If string tail merging is enabled and a section is identified as containing a
400 // string literal, it is added to a MergeChunk with an appropriate alignment.
401 // The MergeChunk then tail merges the strings using the StringTableBuilder
402 // class and assigns RVAs and section offsets to each of the member chunks based
403 // on the offsets assigned by the StringTableBuilder.
404 class MergeChunk : public NonSectionChunk {
405 public:
406   MergeChunk(uint32_t alignment);
407   static void addSection(SectionChunk *c);
408   void finalizeContents();
409   void assignSubsectionRVAs();
410 
411   uint32_t getOutputCharacteristics() const override;
412   StringRef getSectionName() const override { return ".rdata"; }
413   size_t getSize() const override;
414   void writeTo(uint8_t *buf) const override;
415 
416   static MergeChunk *instances[Log2MaxSectionAlignment + 1];
417   std::vector<SectionChunk *> sections;
418 
419 private:
420   llvm::StringTableBuilder builder;
421   bool finalized = false;
422 };
423 
424 // A chunk for common symbols. Common chunks don't have actual data.
425 class CommonChunk : public NonSectionChunk {
426 public:
427   CommonChunk(const COFFSymbolRef sym);
428   size_t getSize() const override { return sym.getValue(); }
429   uint32_t getOutputCharacteristics() const override;
430   StringRef getSectionName() const override { return ".bss"; }
431 
432 private:
433   const COFFSymbolRef sym;
434 };
435 
436 // A chunk for linker-created strings.
437 class StringChunk : public NonSectionChunk {
438 public:
439   explicit StringChunk(StringRef s) : str(s) {}
440   size_t getSize() const override { return str.size() + 1; }
441   void writeTo(uint8_t *buf) const override;
442 
443 private:
444   StringRef str;
445 };
446 
447 static const uint8_t importThunkX86[] = {
448     0xff, 0x25, 0x00, 0x00, 0x00, 0x00, // JMP *0x0
449 };
450 
451 static const uint8_t importThunkARM[] = {
452     0x40, 0xf2, 0x00, 0x0c, // mov.w ip, #0
453     0xc0, 0xf2, 0x00, 0x0c, // mov.t ip, #0
454     0xdc, 0xf8, 0x00, 0xf0, // ldr.w pc, [ip]
455 };
456 
457 static const uint8_t importThunkARM64[] = {
458     0x10, 0x00, 0x00, 0x90, // adrp x16, #0
459     0x10, 0x02, 0x40, 0xf9, // ldr  x16, [x16]
460     0x00, 0x02, 0x1f, 0xd6, // br   x16
461 };
462 
463 // Windows-specific.
464 // A chunk for DLL import jump table entry. In a final output, its
465 // contents will be a JMP instruction to some __imp_ symbol.
466 class ImportThunkChunk : public NonSectionChunk {
467 public:
468   ImportThunkChunk(Defined *s)
469       : NonSectionChunk(ImportThunkKind), impSymbol(s) {}
470   static bool classof(const Chunk *c) { return c->kind() == ImportThunkKind; }
471 
472 protected:
473   Defined *impSymbol;
474 };
475 
476 class ImportThunkChunkX64 : public ImportThunkChunk {
477 public:
478   explicit ImportThunkChunkX64(Defined *s);
479   size_t getSize() const override { return sizeof(importThunkX86); }
480   void writeTo(uint8_t *buf) const override;
481 };
482 
483 class ImportThunkChunkX86 : public ImportThunkChunk {
484 public:
485   explicit ImportThunkChunkX86(Defined *s) : ImportThunkChunk(s) {}
486   size_t getSize() const override { return sizeof(importThunkX86); }
487   void getBaserels(std::vector<Baserel> *res) override;
488   void writeTo(uint8_t *buf) const override;
489 };
490 
491 class ImportThunkChunkARM : public ImportThunkChunk {
492 public:
493   explicit ImportThunkChunkARM(Defined *s) : ImportThunkChunk(s) {}
494   size_t getSize() const override { return sizeof(importThunkARM); }
495   void getBaserels(std::vector<Baserel> *res) override;
496   void writeTo(uint8_t *buf) const override;
497 };
498 
499 class ImportThunkChunkARM64 : public ImportThunkChunk {
500 public:
501   explicit ImportThunkChunkARM64(Defined *s) : ImportThunkChunk(s) {}
502   size_t getSize() const override { return sizeof(importThunkARM64); }
503   void writeTo(uint8_t *buf) const override;
504 };
505 
506 class RangeExtensionThunkARM : public NonSectionChunk {
507 public:
508   explicit RangeExtensionThunkARM(Defined *t) : target(t) {}
509   size_t getSize() const override;
510   void writeTo(uint8_t *buf) const override;
511 
512   Defined *target;
513 };
514 
515 class RangeExtensionThunkARM64 : public NonSectionChunk {
516 public:
517   explicit RangeExtensionThunkARM64(Defined *t) : target(t) {}
518   size_t getSize() const override;
519   void writeTo(uint8_t *buf) const override;
520 
521   Defined *target;
522 };
523 
524 // Windows-specific.
525 // See comments for DefinedLocalImport class.
526 class LocalImportChunk : public NonSectionChunk {
527 public:
528   explicit LocalImportChunk(Defined *s) : sym(s) {
529     setAlignment(config->wordsize);
530   }
531   size_t getSize() const override;
532   void getBaserels(std::vector<Baserel> *res) override;
533   void writeTo(uint8_t *buf) const override;
534 
535 private:
536   Defined *sym;
537 };
538 
539 // Duplicate RVAs are not allowed in RVA tables, so unique symbols by chunk and
540 // offset into the chunk. Order does not matter as the RVA table will be sorted
541 // later.
542 struct ChunkAndOffset {
543   Chunk *inputChunk;
544   uint32_t offset;
545 
546   struct DenseMapInfo {
547     static ChunkAndOffset getEmptyKey() {
548       return {llvm::DenseMapInfo<Chunk *>::getEmptyKey(), 0};
549     }
550     static ChunkAndOffset getTombstoneKey() {
551       return {llvm::DenseMapInfo<Chunk *>::getTombstoneKey(), 0};
552     }
553     static unsigned getHashValue(const ChunkAndOffset &co) {
554       return llvm::DenseMapInfo<std::pair<Chunk *, uint32_t>>::getHashValue(
555           {co.inputChunk, co.offset});
556     }
557     static bool isEqual(const ChunkAndOffset &lhs, const ChunkAndOffset &rhs) {
558       return lhs.inputChunk == rhs.inputChunk && lhs.offset == rhs.offset;
559     }
560   };
561 };
562 
563 using SymbolRVASet = llvm::DenseSet<ChunkAndOffset>;
564 
565 // Table which contains symbol RVAs. Used for /safeseh and /guard:cf.
566 class RVATableChunk : public NonSectionChunk {
567 public:
568   explicit RVATableChunk(SymbolRVASet s) : syms(std::move(s)) {}
569   size_t getSize() const override { return syms.size() * 4; }
570   void writeTo(uint8_t *buf) const override;
571 
572 private:
573   SymbolRVASet syms;
574 };
575 
576 // Windows-specific.
577 // This class represents a block in .reloc section.
578 // See the PE/COFF spec 5.6 for details.
579 class BaserelChunk : public NonSectionChunk {
580 public:
581   BaserelChunk(uint32_t page, Baserel *begin, Baserel *end);
582   size_t getSize() const override { return data.size(); }
583   void writeTo(uint8_t *buf) const override;
584 
585 private:
586   std::vector<uint8_t> data;
587 };
588 
589 class Baserel {
590 public:
591   Baserel(uint32_t v, uint8_t ty) : rva(v), type(ty) {}
592   explicit Baserel(uint32_t v) : Baserel(v, getDefaultType()) {}
593   uint8_t getDefaultType();
594 
595   uint32_t rva;
596   uint8_t type;
597 };
598 
599 // This is a placeholder Chunk, to allow attaching a DefinedSynthetic to a
600 // specific place in a section, without any data. This is used for the MinGW
601 // specific symbol __RUNTIME_PSEUDO_RELOC_LIST_END__, even though the concept
602 // of an empty chunk isn't MinGW specific.
603 class EmptyChunk : public NonSectionChunk {
604 public:
605   EmptyChunk() {}
606   size_t getSize() const override { return 0; }
607   void writeTo(uint8_t *buf) const override {}
608 };
609 
610 // MinGW specific, for the "automatic import of variables from DLLs" feature.
611 // This provides the table of runtime pseudo relocations, for variable
612 // references that turned out to need to be imported from a DLL even though
613 // the reference didn't use the dllimport attribute. The MinGW runtime will
614 // process this table after loading, before handling control over to user
615 // code.
616 class PseudoRelocTableChunk : public NonSectionChunk {
617 public:
618   PseudoRelocTableChunk(std::vector<RuntimePseudoReloc> &relocs)
619       : relocs(std::move(relocs)) {
620     setAlignment(4);
621   }
622   size_t getSize() const override;
623   void writeTo(uint8_t *buf) const override;
624 
625 private:
626   std::vector<RuntimePseudoReloc> relocs;
627 };
628 
629 // MinGW specific; information about one individual location in the image
630 // that needs to be fixed up at runtime after loading. This represents
631 // one individual element in the PseudoRelocTableChunk table.
632 class RuntimePseudoReloc {
633 public:
634   RuntimePseudoReloc(Defined *sym, SectionChunk *target, uint32_t targetOffset,
635                      int flags)
636       : sym(sym), target(target), targetOffset(targetOffset), flags(flags) {}
637 
638   Defined *sym;
639   SectionChunk *target;
640   uint32_t targetOffset;
641   // The Flags field contains the size of the relocation, in bits. No other
642   // flags are currently defined.
643   int flags;
644 };
645 
646 // MinGW specific. A Chunk that contains one pointer-sized absolute value.
647 class AbsolutePointerChunk : public NonSectionChunk {
648 public:
649   AbsolutePointerChunk(uint64_t value) : value(value) {
650     setAlignment(getSize());
651   }
652   size_t getSize() const override;
653   void writeTo(uint8_t *buf) const override;
654 
655 private:
656   uint64_t value;
657 };
658 
659 // Return true if this file has the hotpatch flag set to true in the S_COMPILE3
660 // record in codeview debug info. Also returns true for some thunks synthesized
661 // by the linker.
662 inline bool Chunk::isHotPatchable() const {
663   if (auto *sc = dyn_cast<SectionChunk>(this))
664     return sc->file->hotPatchable;
665   else if (isa<ImportThunkChunk>(this))
666     return true;
667   return false;
668 }
669 
670 void applyMOV32T(uint8_t *off, uint32_t v);
671 void applyBranch24T(uint8_t *off, int32_t v);
672 
673 void applyArm64Addr(uint8_t *off, uint64_t s, uint64_t p, int shift);
674 void applyArm64Imm(uint8_t *off, uint64_t imm, uint32_t rangeLimit);
675 void applyArm64Branch26(uint8_t *off, int64_t v);
676 
677 } // namespace coff
678 } // namespace lld
679 
680 namespace llvm {
681 template <>
682 struct DenseMapInfo<lld::coff::ChunkAndOffset>
683     : lld::coff::ChunkAndOffset::DenseMapInfo {};
684 }
685 
686 #endif
687