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   // Set of .so files to not link the same shared object file more than once.
61   llvm::DenseMap<llvm::CachedHashStringRef, SharedFile *> soNames;
62 
63   // Comdat groups define "link once" sections. If two comdat groups have the
64   // same name, only one of them is linked, and the other is ignored. This map
65   // is used to uniquify them.
66   llvm::DenseMap<llvm::CachedHashStringRef, const InputFile *> comdatGroups;
67 
68   // The Map of __acle_se_<sym>, <sym> pairs found in the input objects.
69   // Key is the <sym> name.
70   llvm::SmallMapVector<StringRef, ArmCmseEntryFunction, 1> cmseSymMap;
71 
72   // Map of symbols defined in the Arm CMSE import library. The linker must
73   // preserve the addresses in the output objects.
74   llvm::StringMap<Defined *> cmseImportLib;
75 
76   // True if <sym> from the input Arm CMSE import library is written to the
77   // output Arm CMSE import library.
78   llvm::StringMap<bool> inCMSEOutImpLib;
79 
80 private:
81   SmallVector<Symbol *, 0> findByVersion(SymbolVersion ver);
82   SmallVector<Symbol *, 0> findAllByVersion(SymbolVersion ver,
83                                             bool includeNonDefault);
84 
85   llvm::StringMap<SmallVector<Symbol *, 0>> &getDemangledSyms();
86   bool assignExactVersion(SymbolVersion ver, uint16_t versionId,
87                           StringRef versionName, bool includeNonDefault);
88   void assignWildcardVersion(SymbolVersion ver, uint16_t versionId,
89                              bool includeNonDefault);
90 
91   // Global symbols and a map from symbol name to the index. The order is not
92   // defined. We can use an arbitrary order, but it has to be deterministic even
93   // when cross linking.
94   llvm::DenseMap<llvm::CachedHashStringRef, int> symMap;
95   SmallVector<Symbol *, 0> symVector;
96 
97   // A map from demangled symbol names to their symbol objects.
98   // This mapping is 1:N because two symbols with different versions
99   // can have the same name. We use this map to handle "extern C++ {}"
100   // directive in version scripts.
101   std::optional<llvm::StringMap<SmallVector<Symbol *, 0>>> demangledSyms;
102 };
103 
104 LLVM_LIBRARY_VISIBILITY extern SymbolTable symtab;
105 
106 } // namespace lld::elf
107 
108 #endif
109