lld/ELF/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_ELF_SYMBOL_TABLE_H
  10 #define LLD_ELF_SYMBOL_TABLE_H
  11
  12 #include "Symbols.h"
  13 #include "llvm/ADT/CachedHashString.h"
  14 #include "llvm/ADT/DenseMap.h"
  15 #include "llvm/Support/Compiler.h"
  16
  17 namespace lld::elf {
  18
  19 class InputFile;
  20 class SharedFile;
  21
  22 struct ArmCmseEntryFunction {
  23   Symbol *acleSeSym;
  24   Symbol *sym;
  25 };
  26
  27 // SymbolTable is a bucket of all known symbols, including defined,
  28 // undefined, or lazy symbols (the last one is symbols in archive
  29 // files whose archive members are not yet loaded).
  30 //
  31 // We put all symbols of all files to a SymbolTable, and the
  32 // SymbolTable selects the "best" symbols if there are name
  33 // conflicts. For example, obviously, a defined symbol is better than
  34 // an undefined symbol. Or, if there's a conflict between a lazy and a
  35 // undefined, it'll read an archive member to read a real definition
  36 // to replace the lazy symbol. The logic is implemented in the
  37 // add*() functions, which are called by input files as they are parsed. There
  38 // is one add* function per symbol type.
  39 class SymbolTable {
  40 public:
  41   ArrayRef<Symbol *> getSymbols() const { return symVector; }
  42
  43   void wrap(Symbol *sym, Symbol *real, Symbol *wrap);
  44
  45   Symbol *insert(StringRef name);
  46
  47   template <typename T> Symbol *addSymbol(const T &newSym) {
  48     Symbol *sym = insert(newSym.getName());
  49     sym->resolve(newSym);
  50     return sym;
  51   }
  52   Symbol *addAndCheckDuplicate(const Defined &newSym);
  53
  54   void scanVersionScript();
  55
  56   Symbol *find(StringRef name);
  57
  58   void handleDynamicList();
  59
  60   Symbol *addUnusedUndefined(StringRef name,
  61                              uint8_t binding = llvm::ELF::STB_GLOBAL);
  62
  63   // Set of .so files to not link the same shared object file more than once.
  64   llvm::DenseMap<llvm::CachedHashStringRef, SharedFile *> soNames;
  65
  66   // Comdat groups define "link once" sections. If two comdat groups have the
  67   // same name, only one of them is linked, and the other is ignored. This map
  68   // is used to uniquify them.
  69   llvm::DenseMap<llvm::CachedHashStringRef, const InputFile *> comdatGroups;
  70
  71   // The Map of __acle_se_<sym>, <sym> pairs found in the input objects.
  72   // Key is the <sym> name.
  73   llvm::SmallMapVector<StringRef, ArmCmseEntryFunction, 1> cmseSymMap;
  74
  75   // Map of symbols defined in the Arm CMSE import library. The linker must
  76   // preserve the addresses in the output objects.
  77   llvm::StringMap<Defined *> cmseImportLib;
  78
  79   // True if <sym> from the input Arm CMSE import library is written to the
  80   // output Arm CMSE import library.
  81   llvm::StringMap<bool> inCMSEOutImpLib;
  82
  83 private:
  84   SmallVector<Symbol *, 0> findByVersion(SymbolVersion ver);
  85   SmallVector<Symbol *, 0> findAllByVersion(SymbolVersion ver,
  86                                             bool includeNonDefault);
  87
  88   llvm::StringMap<SmallVector<Symbol *, 0>> &getDemangledSyms();
  89   bool assignExactVersion(SymbolVersion ver, uint16_t versionId,
  90                           StringRef versionName, bool includeNonDefault);
  91   void assignWildcardVersion(SymbolVersion ver, uint16_t versionId,
  92                              bool includeNonDefault);
  93
  94   // Global symbols and a map from symbol name to the index. The order is not
  95   // defined. We can use an arbitrary order, but it has to be deterministic even
  96   // when cross linking.
  97   llvm::DenseMap<llvm::CachedHashStringRef, int> symMap;
  98   SmallVector<Symbol *, 0> symVector;
  99
 100   // A map from demangled symbol names to their symbol objects.
 101   // This mapping is 1:N because two symbols with different versions
 102   // can have the same name. We use this map to handle "extern C++ {}"
 103   // directive in version scripts.
 104   std::optional<llvm::StringMap<SmallVector<Symbol *, 0>>> demangledSyms;
 105 };
 106
 107 LLVM_LIBRARY_VISIBILITY extern SymbolTable symtab;
 108
 109 } // namespace lld::elf
 110
 111 #endif