| //===- Core/SymbolTable.cpp - Main Symbol Table ---------------------------===// |
| // |
| // The LLVM Linker |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "lld/Core/SymbolTable.h" |
| #include "lld/Core/AbsoluteAtom.h" |
| #include "lld/Core/Atom.h" |
| #include "lld/Core/DefinedAtom.h" |
| #include "lld/Core/File.h" |
| #include "lld/Core/LLVM.h" |
| #include "lld/Core/LinkingContext.h" |
| #include "lld/Core/Resolver.h" |
| #include "lld/Core/SharedLibraryAtom.h" |
| #include "lld/Core/UndefinedAtom.h" |
| #include "llvm/ADT/ArrayRef.h" |
| #include "llvm/ADT/DenseMapInfo.h" |
| #include "llvm/ADT/Hashing.h" |
| #include "llvm/Support/ErrorHandling.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include <algorithm> |
| #include <cassert> |
| #include <cstdlib> |
| #include <vector> |
| |
| namespace lld { |
| SymbolTable::SymbolTable(LinkingContext &context) : _context(context) {} |
| |
| bool SymbolTable::add(const UndefinedAtom &atom) { return addByName(atom); } |
| |
| bool SymbolTable::add(const SharedLibraryAtom &atom) { return addByName(atom); } |
| |
| bool SymbolTable::add(const AbsoluteAtom &atom) { return addByName(atom); } |
| |
| bool SymbolTable::add(const DefinedAtom &atom) { |
| if (!atom.name().empty() && |
| atom.scope() != DefinedAtom::scopeTranslationUnit) { |
| // Named atoms cannot be merged by content. |
| assert(atom.merge() != DefinedAtom::mergeByContent); |
| // Track named atoms that are not scoped to file (static). |
| return addByName(atom); |
| } |
| if (atom.merge() == DefinedAtom::mergeByContent) { |
| // Named atoms cannot be merged by content. |
| assert(atom.name().empty()); |
| // Currently only read-only constants can be merged. |
| if (atom.permissions() == DefinedAtom::permR__) |
| return addByContent(atom); |
| // TODO: support mergeByContent of data atoms by comparing content & fixups. |
| } |
| return false; |
| } |
| |
| const Atom *SymbolTable::findGroup(StringRef sym) { |
| NameToAtom::iterator pos = _groupTable.find(sym); |
| if (pos == _groupTable.end()) |
| return nullptr; |
| return pos->second; |
| } |
| |
| bool SymbolTable::addGroup(const DefinedAtom &da) { |
| StringRef name = da.name(); |
| assert(!name.empty()); |
| const Atom *existing = findGroup(name); |
| if (existing == nullptr) { |
| _groupTable[name] = &da; |
| return true; |
| } |
| _replacedAtoms[&da] = existing; |
| return false; |
| } |
| |
| enum NameCollisionResolution { |
| NCR_First, |
| NCR_Second, |
| NCR_DupDef, |
| NCR_DupUndef, |
| NCR_DupShLib, |
| NCR_Error |
| }; |
| |
| static NameCollisionResolution cases[4][4] = { |
| //regular absolute undef sharedLib |
| { |
| // first is regular |
| NCR_DupDef, NCR_Error, NCR_First, NCR_First |
| }, |
| { |
| // first is absolute |
| NCR_Error, NCR_Error, NCR_First, NCR_First |
| }, |
| { |
| // first is undef |
| NCR_Second, NCR_Second, NCR_DupUndef, NCR_Second |
| }, |
| { |
| // first is sharedLib |
| NCR_Second, NCR_Second, NCR_First, NCR_DupShLib |
| } |
| }; |
| |
| static NameCollisionResolution collide(Atom::Definition first, |
| Atom::Definition second) { |
| return cases[first][second]; |
| } |
| |
| enum MergeResolution { |
| MCR_First, |
| MCR_Second, |
| MCR_Largest, |
| MCR_SameSize, |
| MCR_Error |
| }; |
| |
| static MergeResolution mergeCases[][6] = { |
| // no tentative weak weakAddress sameNameAndSize largest |
| {MCR_Error, MCR_First, MCR_First, MCR_First, MCR_SameSize, MCR_Largest}, // no |
| {MCR_Second, MCR_Largest, MCR_Second, MCR_Second, MCR_SameSize, MCR_Largest}, // tentative |
| {MCR_Second, MCR_First, MCR_First, MCR_Second, MCR_SameSize, MCR_Largest}, // weak |
| {MCR_Second, MCR_First, MCR_First, MCR_First, MCR_SameSize, MCR_Largest}, // weakAddress |
| {MCR_SameSize, MCR_SameSize, MCR_SameSize, MCR_SameSize, MCR_SameSize, MCR_SameSize}, // sameSize |
| {MCR_Largest, MCR_Largest, MCR_Largest, MCR_Largest, MCR_SameSize, MCR_Largest}, // largest |
| }; |
| |
| static MergeResolution mergeSelect(DefinedAtom::Merge first, |
| DefinedAtom::Merge second) { |
| assert(first != DefinedAtom::mergeByContent); |
| assert(second != DefinedAtom::mergeByContent); |
| return mergeCases[first][second]; |
| } |
| |
| bool SymbolTable::addByName(const Atom &newAtom) { |
| StringRef name = newAtom.name(); |
| assert(!name.empty()); |
| const Atom *existing = findByName(name); |
| if (existing == nullptr) { |
| // Name is not in symbol table yet, add it associate with this atom. |
| _nameTable[name] = &newAtom; |
| return true; |
| } |
| |
| // Do nothing if the same object is added more than once. |
| if (existing == &newAtom) |
| return false; |
| |
| // Name is already in symbol table and associated with another atom. |
| bool useNew = true; |
| switch (collide(existing->definition(), newAtom.definition())) { |
| case NCR_First: |
| useNew = false; |
| break; |
| case NCR_Second: |
| useNew = true; |
| break; |
| case NCR_DupDef: { |
| const auto *existingDef = cast<DefinedAtom>(existing); |
| const auto *newDef = cast<DefinedAtom>(&newAtom); |
| switch (mergeSelect(existingDef->merge(), newDef->merge())) { |
| case MCR_First: |
| useNew = false; |
| break; |
| case MCR_Second: |
| useNew = true; |
| break; |
| case MCR_Largest: { |
| uint64_t existingSize = existingDef->sectionSize(); |
| uint64_t newSize = newDef->sectionSize(); |
| useNew = (newSize >= existingSize); |
| break; |
| } |
| case MCR_SameSize: { |
| uint64_t existingSize = existingDef->sectionSize(); |
| uint64_t newSize = newDef->sectionSize(); |
| if (existingSize == newSize) { |
| useNew = true; |
| break; |
| } |
| llvm::errs() << "Size mismatch: " |
| << existing->name() << " (" << existingSize << ") " |
| << newAtom.name() << " (" << newSize << ")\n"; |
| // fallthrough |
| } |
| case MCR_Error: |
| if (!_context.getAllowDuplicates()) { |
| llvm::errs() << "Duplicate symbols: " |
| << existing->name() |
| << ":" |
| << existing->file().path() |
| << " and " |
| << newAtom.name() |
| << ":" |
| << newAtom.file().path() |
| << "\n"; |
| llvm::report_fatal_error("duplicate symbol error"); |
| } |
| useNew = false; |
| break; |
| } |
| break; |
| } |
| case NCR_DupUndef: { |
| const UndefinedAtom* existingUndef = cast<UndefinedAtom>(existing); |
| const UndefinedAtom* newUndef = cast<UndefinedAtom>(&newAtom); |
| |
| bool sameCanBeNull = (existingUndef->canBeNull() == newUndef->canBeNull()); |
| if (!sameCanBeNull && |
| _context.warnIfCoalesableAtomsHaveDifferentCanBeNull()) { |
| llvm::errs() << "lld warning: undefined symbol " |
| << existingUndef->name() |
| << " has different weakness in " |
| << existingUndef->file().path() |
| << " and in " << newUndef->file().path() << "\n"; |
| } |
| |
| const UndefinedAtom *existingFallback = existingUndef->fallback(); |
| const UndefinedAtom *newFallback = newUndef->fallback(); |
| bool hasDifferentFallback = |
| (existingFallback && newFallback && |
| existingFallback->name() != newFallback->name()); |
| if (hasDifferentFallback) { |
| llvm::errs() << "lld warning: undefined symbol " |
| << existingUndef->name() << " has different fallback: " |
| << existingFallback->name() << " in " |
| << existingUndef->file().path() << " and " |
| << newFallback->name() << " in " |
| << newUndef->file().path() << "\n"; |
| } |
| |
| bool hasNewFallback = newUndef->fallback(); |
| if (sameCanBeNull) |
| useNew = hasNewFallback; |
| else |
| useNew = (newUndef->canBeNull() < existingUndef->canBeNull()); |
| break; |
| } |
| case NCR_DupShLib: { |
| const SharedLibraryAtom *curShLib = cast<SharedLibraryAtom>(existing); |
| const SharedLibraryAtom *newShLib = cast<SharedLibraryAtom>(&newAtom); |
| bool sameNullness = |
| (curShLib->canBeNullAtRuntime() == newShLib->canBeNullAtRuntime()); |
| bool sameName = curShLib->loadName().equals(newShLib->loadName()); |
| if (sameName && !sameNullness && |
| _context.warnIfCoalesableAtomsHaveDifferentCanBeNull()) { |
| // FIXME: need diagonstics interface for writing warning messages |
| llvm::errs() << "lld warning: shared library symbol " |
| << curShLib->name() << " has different weakness in " |
| << curShLib->file().path() << " and in " |
| << newShLib->file().path(); |
| } |
| if (!sameName && _context.warnIfCoalesableAtomsHaveDifferentLoadName()) { |
| // FIXME: need diagonstics interface for writing warning messages |
| llvm::errs() << "lld warning: shared library symbol " |
| << curShLib->name() << " has different load path in " |
| << curShLib->file().path() << " and in " |
| << newShLib->file().path(); |
| } |
| useNew = false; |
| break; |
| } |
| case NCR_Error: |
| llvm::errs() << "SymbolTable: error while merging " << name << "\n"; |
| llvm::report_fatal_error("duplicate symbol error"); |
| break; |
| } |
| |
| // Give context a chance to change which is kept. |
| _context.notifySymbolTableCoalesce(existing, &newAtom, useNew); |
| |
| if (useNew) { |
| // Update name table to use new atom. |
| _nameTable[name] = &newAtom; |
| // Add existing atom to replacement table. |
| _replacedAtoms[existing] = &newAtom; |
| } else { |
| // New atom is not being used. Add it to replacement table. |
| _replacedAtoms[&newAtom] = existing; |
| } |
| return false; |
| } |
| |
| unsigned SymbolTable::AtomMappingInfo::getHashValue(const DefinedAtom *atom) { |
| auto content = atom->rawContent(); |
| return llvm::hash_combine(atom->size(), |
| atom->contentType(), |
| llvm::hash_combine_range(content.begin(), |
| content.end())); |
| } |
| |
| bool SymbolTable::AtomMappingInfo::isEqual(const DefinedAtom * const l, |
| const DefinedAtom * const r) { |
| if (l == r) |
| return true; |
| if (l == getEmptyKey()) |
| return false; |
| if (r == getEmptyKey()) |
| return false; |
| if (l == getTombstoneKey()) |
| return false; |
| if (r == getTombstoneKey()) |
| return false; |
| if (l->contentType() != r->contentType()) |
| return false; |
| if (l->size() != r->size()) |
| return false; |
| if (l->sectionChoice() != r->sectionChoice()) |
| return false; |
| if (l->sectionChoice() == DefinedAtom::sectionCustomRequired) { |
| if (!l->customSectionName().equals(r->customSectionName())) |
| return false; |
| } |
| ArrayRef<uint8_t> lc = l->rawContent(); |
| ArrayRef<uint8_t> rc = r->rawContent(); |
| return memcmp(lc.data(), rc.data(), lc.size()) == 0; |
| } |
| |
| bool SymbolTable::addByContent(const DefinedAtom &newAtom) { |
| AtomContentSet::iterator pos = _contentTable.find(&newAtom); |
| if (pos == _contentTable.end()) { |
| _contentTable.insert(&newAtom); |
| return true; |
| } |
| const Atom* existing = *pos; |
| // New atom is not being used. Add it to replacement table. |
| _replacedAtoms[&newAtom] = existing; |
| return false; |
| } |
| |
| const Atom *SymbolTable::findByName(StringRef sym) { |
| NameToAtom::iterator pos = _nameTable.find(sym); |
| if (pos == _nameTable.end()) |
| return nullptr; |
| return pos->second; |
| } |
| |
| bool SymbolTable::isDefined(StringRef sym) { |
| if (const Atom *atom = findByName(sym)) |
| return !isa<UndefinedAtom>(atom); |
| return false; |
| } |
| |
| void SymbolTable::addReplacement(const Atom *replaced, |
| const Atom *replacement) { |
| _replacedAtoms[replaced] = replacement; |
| } |
| |
| const Atom *SymbolTable::replacement(const Atom *atom) { |
| // Find the replacement for a given atom. Atoms in _replacedAtoms |
| // may be chained, so find the last one. |
| for (;;) { |
| AtomToAtom::iterator pos = _replacedAtoms.find(atom); |
| if (pos == _replacedAtoms.end()) |
| return atom; |
| atom = pos->second; |
| } |
| } |
| |
| bool SymbolTable::isCoalescedAway(const Atom *atom) { |
| return _replacedAtoms.count(atom) > 0; |
| } |
| |
| std::vector<const UndefinedAtom *> SymbolTable::undefines() { |
| std::vector<const UndefinedAtom *> ret; |
| for (auto it : _nameTable) { |
| const Atom *atom = it.second; |
| assert(atom != nullptr); |
| if (const auto *undef = dyn_cast<const UndefinedAtom>(atom)) |
| if (_replacedAtoms.count(undef) == 0) |
| ret.push_back(undef); |
| } |
| return ret; |
| } |
| |
| std::vector<StringRef> SymbolTable::tentativeDefinitions() { |
| std::vector<StringRef> ret; |
| for (auto entry : _nameTable) { |
| const Atom *atom = entry.second; |
| StringRef name = entry.first; |
| assert(atom != nullptr); |
| if (const DefinedAtom *defAtom = dyn_cast<DefinedAtom>(atom)) |
| if (defAtom->merge() == DefinedAtom::mergeAsTentative) |
| ret.push_back(name); |
| } |
| return ret; |
| } |
| |
| } // namespace lld |