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ebb326a51f
Previously, linker was unnecessarily including a PROVIDE symbol which was referenced by another unused PROVIDE symbol. For example, if a linker script contained the below code and 'not_used_sym' provide symbol is not included, then linker was still unnecessarily including 'foo' PROVIDE symbol because it was referenced by 'not_used_sym'. This commit fixes this behavior. PROVIDE(not_used_sym = foo) PROVIDE(foo = 0x1000) This commit fixes this behavior by using dfs-like algorithm to find all the symbols referenced in provide expressions of included provide symbols. This commit also fixes the issue of unused section not being garbage-collected if a symbol of the section is referenced by an unused PROVIDE symbol. Closes #74771 Closes #84730 Co-authored-by: Fangrui Song <i@maskray.me>
112 lines
4.0 KiB
C++
112 lines
4.0 KiB
C++
//===- SymbolTable.h --------------------------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLD_ELF_SYMBOL_TABLE_H
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#define LLD_ELF_SYMBOL_TABLE_H
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#include "Symbols.h"
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#include "llvm/ADT/CachedHashString.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/Support/Compiler.h"
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namespace lld::elf {
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class InputFile;
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class SharedFile;
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struct ArmCmseEntryFunction {
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Symbol *acleSeSym;
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Symbol *sym;
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};
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// SymbolTable is a bucket of all known symbols, including defined,
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// undefined, or lazy symbols (the last one is symbols in archive
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// files whose archive members are not yet loaded).
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//
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// We put all symbols of all files to a SymbolTable, and the
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// SymbolTable selects the "best" symbols if there are name
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// conflicts. For example, obviously, a defined symbol is better than
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// an undefined symbol. Or, if there's a conflict between a lazy and a
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// undefined, it'll read an archive member to read a real definition
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// to replace the lazy symbol. The logic is implemented in the
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// add*() functions, which are called by input files as they are parsed. There
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// is one add* function per symbol type.
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class SymbolTable {
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public:
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ArrayRef<Symbol *> getSymbols() const { return symVector; }
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void wrap(Symbol *sym, Symbol *real, Symbol *wrap);
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Symbol *insert(StringRef name);
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template <typename T> Symbol *addSymbol(const T &newSym) {
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Symbol *sym = insert(newSym.getName());
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sym->resolve(newSym);
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return sym;
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}
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Symbol *addAndCheckDuplicate(const Defined &newSym);
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void scanVersionScript();
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Symbol *find(StringRef name);
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void handleDynamicList();
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Symbol *addUnusedUndefined(StringRef name,
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uint8_t binding = llvm::ELF::STB_GLOBAL);
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// Set of .so files to not link the same shared object file more than once.
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llvm::DenseMap<llvm::CachedHashStringRef, SharedFile *> soNames;
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// Comdat groups define "link once" sections. If two comdat groups have the
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// same name, only one of them is linked, and the other is ignored. This map
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// is used to uniquify them.
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llvm::DenseMap<llvm::CachedHashStringRef, const InputFile *> comdatGroups;
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// The Map of __acle_se_<sym>, <sym> pairs found in the input objects.
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// Key is the <sym> name.
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llvm::SmallMapVector<StringRef, ArmCmseEntryFunction, 1> cmseSymMap;
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// Map of symbols defined in the Arm CMSE import library. The linker must
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// preserve the addresses in the output objects.
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llvm::StringMap<Defined *> cmseImportLib;
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// True if <sym> from the input Arm CMSE import library is written to the
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// output Arm CMSE import library.
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llvm::StringMap<bool> inCMSEOutImpLib;
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private:
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SmallVector<Symbol *, 0> findByVersion(SymbolVersion ver);
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SmallVector<Symbol *, 0> findAllByVersion(SymbolVersion ver,
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bool includeNonDefault);
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llvm::StringMap<SmallVector<Symbol *, 0>> &getDemangledSyms();
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bool assignExactVersion(SymbolVersion ver, uint16_t versionId,
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StringRef versionName, bool includeNonDefault);
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void assignWildcardVersion(SymbolVersion ver, uint16_t versionId,
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bool includeNonDefault);
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// Global symbols and a map from symbol name to the index. The order is not
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// defined. We can use an arbitrary order, but it has to be deterministic even
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// when cross linking.
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llvm::DenseMap<llvm::CachedHashStringRef, int> symMap;
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SmallVector<Symbol *, 0> symVector;
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// A map from demangled symbol names to their symbol objects.
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// This mapping is 1:N because two symbols with different versions
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// can have the same name. We use this map to handle "extern C++ {}"
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// directive in version scripts.
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std::optional<llvm::StringMap<SmallVector<Symbol *, 0>>> demangledSyms;
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};
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LLVM_LIBRARY_VISIBILITY extern SymbolTable symtab;
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} // namespace lld::elf
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#endif
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