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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 };
kind()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.
getAlignment()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.
setAlignment(uint32_t align)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.
getRVA()87   uint32_t getRVA() const { return rva; }
setRVA(uint64_t v)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.
setOutputSectionIdx(uint16_t o)102   void setOutputSectionIdx(uint16_t o) { osidx = o; }
getOutputSectionIdx()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:
chunkKind(k)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 
getOutputCharacteristics()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.
writeTo(uint8_t * buf)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.
getSectionName()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.
getBaserels(std::vector<Baserel> * res)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.
getDebugName()171   virtual StringRef getDebugName() const { return ""; }
172 
classof(const Chunk * c)173   static bool classof(const Chunk *c) { return c->kind() != SectionKind; }
174 
175 protected:
Chunk(k)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 
symbol_iterator(ObjFile * file,const coff_relocation * i)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);
classof(const Chunk * c)202   static bool classof(const Chunk *c) { return c->kind() == SectionKind; }
getSize()203   size_t getSize() const { return header->SizeOfRawData; }
204   ArrayRef<uint8_t> getContents() const;
205   void writeTo(uint8_t *buf) const;
206 
getOutputCharacteristics()207   uint32_t getOutputCharacteristics() const {
208     return header->Characteristics & (permMask | typeMask);
209   }
getSectionName()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.
isCodeView()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.
isDWARF()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.
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 
getRelocs()253   ArrayRef<coff_relocation> getRelocs() const {
254     return llvm::makeArrayRef(relocsData, relocsSize);
255   }
256 
257   // Reloc setter used by ARM range extension thunk insertion.
setRelocs(ArrayRef<coff_relocation> newRelocs)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;
AssociatedIterator(SectionChunk * head)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.
children()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 
getSize()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 
getOutputCharacteristics()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 
writeTo(uint8_t * buf)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 
getSectionName()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 
getBaserels(std::vector<Baserel> * res)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 
getDebugName()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;
getSectionName()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);
getSize()425   size_t getSize() const override { return sym.getValue(); }
426   uint32_t getOutputCharacteristics() const override;
getSectionName()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:
StringChunk(StringRef s)436   explicit StringChunk(StringRef s) : str(s) {}
getSize()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:
ImportThunkChunk(Defined * s)465   ImportThunkChunk(Defined *s)
466       : NonSectionChunk(ImportThunkKind), impSymbol(s) {}
classof(const Chunk * c)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);
getSize()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:
ImportThunkChunkX86(Defined * s)482   explicit ImportThunkChunkX86(Defined *s) : ImportThunkChunk(s) {}
getSize()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:
ImportThunkChunkARM(Defined * s)490   explicit ImportThunkChunkARM(Defined *s) : ImportThunkChunk(s) {
491     setAlignment(2);
492   }
getSize()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:
ImportThunkChunkARM64(Defined * s)500   explicit ImportThunkChunkARM64(Defined *s) : ImportThunkChunk(s) {
501     setAlignment(4);
502   }
getSize()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:
RangeExtensionThunkARM(Defined * t)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:
RangeExtensionThunkARM64(Defined * t)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:
LocalImportChunk(Defined * s)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 {
getEmptyKeyChunkAndOffset::DenseMapInfo548     static ChunkAndOffset getEmptyKey() {
549       return {llvm::DenseMapInfo<Chunk *>::getEmptyKey(), 0};
550     }
getTombstoneKeyChunkAndOffset::DenseMapInfo551     static ChunkAndOffset getTombstoneKey() {
552       return {llvm::DenseMapInfo<Chunk *>::getTombstoneKey(), 0};
553     }
getHashValueChunkAndOffset::DenseMapInfo554     static unsigned getHashValue(const ChunkAndOffset &co) {
555       return llvm::DenseMapInfo<std::pair<Chunk *, uint32_t>>::getHashValue(
556           {co.inputChunk, co.offset});
557     }
isEqualChunkAndOffset::DenseMapInfo558     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:
RVATableChunk(SymbolRVASet s)569   explicit RVATableChunk(SymbolRVASet s) : syms(std::move(s)) {}
getSize()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);
getSize()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:
Baserel(uint32_t v,uint8_t ty)592   Baserel(uint32_t v, uint8_t ty) : rva(v), type(ty) {}
Baserel(uint32_t v)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:
EmptyChunk()606   EmptyChunk() {}
getSize()607   size_t getSize() const override { return 0; }
writeTo(uint8_t * buf)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:
PseudoRelocTableChunk(std::vector<RuntimePseudoReloc> & relocs)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:
RuntimePseudoReloc(Defined * sym,SectionChunk * target,uint32_t targetOffset,int flags)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:
AbsolutePointerChunk(uint64_t value)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.
isHotPatchable()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
688