lld/COFF/SymbolTable.h

   1 //===- SymbolTable.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_SYMBOL_TABLE_H
  10 #define LLD_COFF_SYMBOL_TABLE_H
  11
  12 #include "InputFiles.h"
  13 #include "LTO.h"
  14 #include "llvm/ADT/CachedHashString.h"
  15 #include "llvm/ADT/DenseMap.h"
  16 #include "llvm/ADT/DenseMapInfo.h"
  17 #include "llvm/Support/raw_ostream.h"
  18
  19 namespace llvm {
  20 struct LTOCodeGenerator;
  21 }
  22
  23 namespace lld::coff {
  24
  25 class Chunk;
  26 class CommonChunk;
  27 class COFFLinkerContext;
  28 class Defined;
  29 class DefinedAbsolute;
  30 class DefinedRegular;
  31 class ImportThunkChunk;
  32 class LazyArchive;
  33 class SectionChunk;
  34 class Symbol;
  35
  36 // SymbolTable is a bucket of all known symbols, including defined,
  37 // undefined, or lazy symbols (the last one is symbols in archive
  38 // files whose archive members are not yet loaded).
  39 //
  40 // We put all symbols of all files to a SymbolTable, and the
  41 // SymbolTable selects the "best" symbols if there are name
  42 // conflicts. For example, obviously, a defined symbol is better than
  43 // an undefined symbol. Or, if there's a conflict between a lazy and a
  44 // undefined, it'll read an archive member to read a real definition
  45 // to replace the lazy symbol. The logic is implemented in the
  46 // add*() functions, which are called by input files as they are parsed.
  47 // There is one add* function per symbol type.
  48 class SymbolTable {
  49 public:
  50   SymbolTable(COFFLinkerContext &c) : ctx(c) {}
  51
  52   void addFile(InputFile *file);
  53
  54   // Emit errors for symbols that cannot be resolved.
  55   void reportUnresolvable();
  56
  57   // Try to resolve any undefined symbols and update the symbol table
  58   // accordingly, then print an error message for any remaining undefined
  59   // symbols and warn about imported local symbols.
  60   // Returns whether more files might need to be linked in to resolve lazy
  61   // symbols, in which case the caller is expected to call the function again
  62   // after linking those files.
  63   bool resolveRemainingUndefines();
  64
  65   // Load lazy objects that are needed for MinGW automatic import and for
  66   // doing stdcall fixups.
  67   void loadMinGWSymbols();
  68   bool handleMinGWAutomaticImport(Symbol *sym, StringRef name);
  69
  70   // Returns a list of chunks of selected symbols.
  71   std::vector<Chunk *> getChunks() const;
  72
  73   // Returns a symbol for a given name. Returns a nullptr if not found.
  74   Symbol *find(StringRef name) const;
  75   Symbol *findUnderscore(StringRef name) const;
  76
  77   // Occasionally we have to resolve an undefined symbol to its
  78   // mangled symbol. This function tries to find a mangled name
  79   // for U from the symbol table, and if found, set the symbol as
  80   // a weak alias for U.
  81   Symbol *findMangle(StringRef name);
  82
  83   // Build a set of COFF objects representing the combined contents of
  84   // BitcodeFiles and add them to the symbol table. Called after all files are
  85   // added and before the writer writes results to a file.
  86   void compileBitcodeFiles();
  87
  88   // Creates an Undefined symbol for a given name.
  89   Symbol *addUndefined(StringRef name);
  90
  91   Symbol *addSynthetic(StringRef n, Chunk *c);
  92   Symbol *addAbsolute(StringRef n, uint64_t va);
  93
  94   Symbol *addUndefined(StringRef name, InputFile *f, bool overrideLazy);
  95   void addLazyArchive(ArchiveFile *f, const Archive::Symbol &sym);
  96   void addLazyObject(InputFile *f, StringRef n);
  97   void addLazyDLLSymbol(DLLFile *f, DLLFile::Symbol *sym, StringRef n);
  98   Symbol *addAbsolute(StringRef n, COFFSymbolRef s);
  99   Symbol *addRegular(InputFile *f, StringRef n,
 100                      const llvm::object::coff_symbol_generic *s = nullptr,
 101                      SectionChunk *c = nullptr, uint32_t sectionOffset = 0,
 102                      bool isWeak = false);
 103   std::pair<DefinedRegular *, bool>
 104   addComdat(InputFile *f, StringRef n,
 105             const llvm::object::coff_symbol_generic *s = nullptr);
 106   Symbol *addCommon(InputFile *f, StringRef n, uint64_t size,
 107                     const llvm::object::coff_symbol_generic *s = nullptr,
 108                     CommonChunk *c = nullptr);
 109   DefinedImportData *addImportData(StringRef n, ImportFile *f,
 110                                    Chunk *&location);
 111   Defined *addImportThunk(StringRef name, DefinedImportData *s,
 112                           ImportThunkChunk *chunk);
 113   void addLibcall(StringRef name);
 114   void addEntryThunk(Symbol *from, Symbol *to);
 115   void addExitThunk(Symbol *from, Symbol *to);
 116   void initializeECThunks();
 117
 118   void reportDuplicate(Symbol *existing, InputFile *newFile,
 119                        SectionChunk *newSc = nullptr,
 120                        uint32_t newSectionOffset = 0);
 121
 122   // A list of chunks which to be added to .rdata.
 123   std::vector<Chunk *> localImportChunks;
 124
 125   // A list of EC EXP+ symbols.
 126   std::vector<Symbol *> expSymbols;
 127
 128   // Iterates symbols in non-determinstic hash table order.
 129   template <typename T> void forEachSymbol(T callback) {
 130     for (auto &pair : symMap)
 131       callback(pair.second);
 132   }
 133
 134 private:
 135   /// Given a name without "__imp_" prefix, returns a defined symbol
 136   /// with the "__imp_" prefix, if it exists.
 137   Defined *impSymbol(StringRef name);
 138   /// Inserts symbol if not already present.
 139   std::pair<Symbol *, bool> insert(StringRef name);
 140   /// Same as insert(Name), but also sets isUsedInRegularObj.
 141   std::pair<Symbol *, bool> insert(StringRef name, InputFile *f);
 142
 143   std::vector<Symbol *> getSymsWithPrefix(StringRef prefix);
 144
 145   llvm::DenseMap<llvm::CachedHashStringRef, Symbol *> symMap;
 146   std::unique_ptr<BitcodeCompiler> lto;
 147   bool ltoCompilationDone = false;
 148   std::vector<std::pair<Symbol *, Symbol *>> entryThunks;
 149   llvm::DenseMap<Symbol *, Symbol *> exitThunks;
 150
 151   COFFLinkerContext &ctx;
 152 };
 153
 154 std::vector<std::string> getSymbolLocations(ObjFile *file, uint32_t symIndex);
 155
 156 StringRef ltrim1(StringRef s, const char *chars);
 157
 158 } // namespace lld::coff
 159
 160 #endif