360 lines
11 KiB
C++
360 lines
11 KiB
C++
//===- SymbolTable.cpp ----------------------------------------------------===//
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//
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// The LLVM Linker
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "Config.h"
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#include "Driver.h"
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#include "Error.h"
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#include "SymbolTable.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/LTO/LTOCodeGenerator.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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namespace lld {
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namespace coff {
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SymbolTable::SymbolTable() {
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resolve(new (Alloc) DefinedAbsolute("__ImageBase", Config->ImageBase));
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if (!Config->EntryName.empty())
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resolve(new (Alloc) Undefined(Config->EntryName));
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}
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void SymbolTable::addFile(std::unique_ptr<InputFile> File) {
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Files.push_back(std::move(File));
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}
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std::error_code SymbolTable::run() {
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while (FileIdx < Files.size()) {
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InputFile *F = Files[FileIdx++].get();
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if (Config->Verbose)
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llvm::outs() << "Reading " << F->getShortName() << "\n";
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if (auto EC = F->parse())
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return EC;
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if (auto *P = dyn_cast<ObjectFile>(F)) {
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ObjectFiles.push_back(P);
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} else if (auto *P = dyn_cast<ArchiveFile>(F)) {
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ArchiveFiles.push_back(P);
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} else if (auto *P = dyn_cast<BitcodeFile>(F)) {
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BitcodeFiles.push_back(P);
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} else {
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ImportFiles.push_back(cast<ImportFile>(F));
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}
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for (SymbolBody *B : F->getSymbols())
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if (B->isExternal())
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if (auto EC = resolve(B))
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return EC;
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// If a object file contains .drectve section,
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// read that and add files listed there.
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StringRef S = F->getDirectives();
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if (!S.empty())
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if (auto EC = Driver->parseDirectives(S))
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return EC;
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}
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return std::error_code();
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}
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bool SymbolTable::reportRemainingUndefines() {
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bool Ret = false;
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for (auto &I : Symtab) {
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Symbol *Sym = I.second;
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auto *Undef = dyn_cast<Undefined>(Sym->Body);
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if (!Undef)
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continue;
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StringRef Name = Undef->getName();
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if (SymbolBody *Alias = Undef->getWeakAlias()) {
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Sym->Body = Alias->getReplacement();
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if (!isa<Defined>(Sym->Body)) {
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// Aliases are yet another symbols pointed by other symbols
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// that could also remain undefined.
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llvm::errs() << "undefined symbol: " << Name << "\n";
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Ret = true;
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}
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continue;
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}
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// If we can resolve a symbol by removing __imp_ prefix, do that.
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// This odd rule is for compatibility with MSVC linker.
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if (Name.startswith("__imp_")) {
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if (Defined *Imp = find(Name.substr(strlen("__imp_")))) {
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auto *S = new (Alloc) DefinedLocalImport(Name, Imp);
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LocalImportChunks.push_back(S->getChunk());
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Sym->Body = S;
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continue;
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}
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}
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llvm::errs() << "undefined symbol: " << Name << "\n";
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Ret = true;
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}
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return Ret;
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}
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// This function resolves conflicts if there's an existing symbol with
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// the same name. Decisions are made based on symbol type.
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std::error_code SymbolTable::resolve(SymbolBody *New) {
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// Find an existing Symbol or create and insert a new one.
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StringRef Name = New->getName();
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Symbol *&Sym = Symtab[Name];
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if (!Sym) {
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Sym = new (Alloc) Symbol(New);
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New->setBackref(Sym);
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++Version;
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return std::error_code();
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}
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New->setBackref(Sym);
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// compare() returns -1, 0, or 1 if the lhs symbol is less preferable,
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// equivalent (conflicting), or more preferable, respectively.
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SymbolBody *Existing = Sym->Body;
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int comp = Existing->compare(New);
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if (comp < 0) {
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Sym->Body = New;
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++Version;
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}
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if (comp == 0) {
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llvm::errs() << "duplicate symbol: " << Name << "\n";
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return make_error_code(LLDError::DuplicateSymbols);
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}
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// If we have an Undefined symbol for a Lazy symbol, we need
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// to read an archive member to replace the Lazy symbol with
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// a Defined symbol.
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if (isa<Undefined>(Existing) || isa<Undefined>(New))
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if (auto *B = dyn_cast<Lazy>(Sym->Body))
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return addMemberFile(B);
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return std::error_code();
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}
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// Reads an archive member file pointed by a given symbol.
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std::error_code SymbolTable::addMemberFile(Lazy *Body) {
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auto FileOrErr = Body->getMember();
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if (auto EC = FileOrErr.getError())
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return EC;
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std::unique_ptr<InputFile> File = std::move(FileOrErr.get());
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// getMember returns an empty buffer if the member was already
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// read from the library.
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if (!File)
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return std::error_code();
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if (Config->Verbose)
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llvm::outs() << "Loaded " << File->getShortName() << " for "
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<< Body->getName() << "\n";
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addFile(std::move(File));
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return std::error_code();
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}
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std::vector<Chunk *> SymbolTable::getChunks() {
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std::vector<Chunk *> Res;
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for (ObjectFile *File : ObjectFiles) {
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std::vector<Chunk *> &V = File->getChunks();
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Res.insert(Res.end(), V.begin(), V.end());
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}
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return Res;
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}
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Defined *SymbolTable::find(StringRef Name) {
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auto It = Symtab.find(Name);
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if (It == Symtab.end())
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return nullptr;
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if (auto *Def = dyn_cast<Defined>(It->second->Body))
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return Def;
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return nullptr;
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}
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std::error_code SymbolTable::resolveLazy(StringRef Name) {
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auto It = Symtab.find(Name);
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if (It == Symtab.end())
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return std::error_code();
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if (auto *B = dyn_cast<Lazy>(It->second->Body)) {
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if (auto EC = addMemberFile(B))
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return EC;
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return run();
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}
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return std::error_code();
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}
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// Windows specific -- Link default entry point name.
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ErrorOr<StringRef> SymbolTable::findDefaultEntry() {
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// If it's DLL, the rule is easy.
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if (Config->DLL) {
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StringRef Sym = "_DllMainCRTStartup";
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if (auto EC = resolve(new (Alloc) Undefined(Sym)))
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return EC;
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return Sym;
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}
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// User-defined main functions and their corresponding entry points.
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static const char *Entries[][2] = {
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{"main", "mainCRTStartup"},
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{"wmain", "wmainCRTStartup"},
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{"WinMain", "WinMainCRTStartup"},
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{"wWinMain", "wWinMainCRTStartup"},
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};
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for (auto E : Entries) {
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resolveLazy(E[1]);
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if (find(E[1]))
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return StringRef(E[1]);
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if (!find(E[0]))
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continue;
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if (auto EC = resolve(new (Alloc) Undefined(E[1])))
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return EC;
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return StringRef(E[1]);
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}
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llvm::errs() << "entry point must be defined\n";
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return make_error_code(LLDError::InvalidOption);
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}
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std::error_code SymbolTable::addUndefined(StringRef Name) {
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return resolve(new (Alloc) Undefined(Name));
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}
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// Resolve To, and make From an alias to To.
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std::error_code SymbolTable::rename(StringRef From, StringRef To) {
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// If From is not undefined, do nothing.
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// Otherwise, rename it to see if To can be resolved instead.
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auto It = Symtab.find(From);
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if (It == Symtab.end())
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return std::error_code();
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Symbol *Sym = It->second;
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if (!isa<Undefined>(Sym->Body))
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return std::error_code();
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SymbolBody *Body = new (Alloc) Undefined(To);
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if (auto EC = resolve(Body))
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return EC;
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Sym->Body = Body->getReplacement();
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Body->setBackref(Sym);
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++Version;
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return std::error_code();
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}
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void SymbolTable::dump() {
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for (auto &P : Symtab) {
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Symbol *Ref = P.second;
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if (auto *Body = dyn_cast<Defined>(Ref->Body))
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llvm::dbgs() << Twine::utohexstr(Config->ImageBase + Body->getRVA())
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<< " " << Body->getName() << "\n";
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}
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}
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std::error_code SymbolTable::addCombinedLTOObject() {
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if (BitcodeFiles.empty())
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return std::error_code();
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// Create an object file and add it to the symbol table by replacing any
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// DefinedBitcode symbols with the definitions in the object file.
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LTOCodeGenerator CG;
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auto FileOrErr = createLTOObject(&CG);
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if (auto EC = FileOrErr.getError())
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return EC;
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ObjectFile *Obj = FileOrErr.get();
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// Skip the combined object file as the file is processed below
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// rather than by run().
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++FileIdx;
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for (SymbolBody *Body : Obj->getSymbols()) {
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if (!Body->isExternal())
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continue;
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// Find an existing Symbol. We should not see any new undefined symbols at
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// this point.
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StringRef Name = Body->getName();
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Symbol *&Sym = Symtab[Name];
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if (!Sym) {
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if (!isa<Defined>(Body)) {
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llvm::errs() << "LTO: undefined symbol: " << Name << '\n';
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return make_error_code(LLDError::BrokenFile);
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}
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Sym = new (Alloc) Symbol(Body);
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Body->setBackref(Sym);
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continue;
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}
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Body->setBackref(Sym);
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if (isa<DefinedBitcode>(Sym->Body)) {
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// The symbol should now be defined.
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if (!isa<Defined>(Body)) {
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llvm::errs() << "LTO: undefined symbol: " << Name << '\n';
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return make_error_code(LLDError::BrokenFile);
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}
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Sym->Body = Body;
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} else {
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int comp = Sym->Body->compare(Body);
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if (comp < 0)
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Sym->Body = Body;
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if (comp == 0) {
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llvm::errs() << "LTO: unexpected duplicate symbol: " << Name << "\n";
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return make_error_code(LLDError::BrokenFile);
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}
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}
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// We may see new references to runtime library symbols such as __chkstk
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// here. These symbols must be wholly defined in non-bitcode files.
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if (auto *B = dyn_cast<Lazy>(Sym->Body))
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if (auto EC = addMemberFile(B))
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return EC;
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}
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size_t NumBitcodeFiles = BitcodeFiles.size();
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if (auto EC = run())
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return EC;
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if (BitcodeFiles.size() != NumBitcodeFiles) {
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llvm::errs() << "LTO: late loaded symbol created new bitcode reference\n";
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return make_error_code(LLDError::BrokenFile);
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}
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// New runtime library symbol references may have created undefined references.
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if (reportRemainingUndefines())
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return make_error_code(LLDError::BrokenFile);
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return std::error_code();
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}
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// Combine and compile bitcode files and then return the result
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// as a regular COFF object file.
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ErrorOr<ObjectFile *> SymbolTable::createLTOObject(LTOCodeGenerator *CG) {
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// All symbols referenced by non-bitcode objects must be preserved.
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for (ObjectFile *File : ObjectFiles)
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for (SymbolBody *Body : File->getSymbols())
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if (auto *S = dyn_cast<DefinedBitcode>(Body->getReplacement()))
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CG->addMustPreserveSymbol(S->getName());
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// Likewise for bitcode symbols which we initially resolved to non-bitcode.
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for (BitcodeFile *File : BitcodeFiles)
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for (SymbolBody *Body : File->getSymbols())
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if (isa<DefinedBitcode>(Body) &&
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!isa<DefinedBitcode>(Body->getReplacement()))
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CG->addMustPreserveSymbol(Body->getName());
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// Likewise for other symbols that must be preserved.
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for (StringRef Name : Config->GCRoots)
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if (isa<DefinedBitcode>(Symtab[Name]->Body))
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CG->addMustPreserveSymbol(Name);
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CG->setModule(BitcodeFiles[0]->releaseModule());
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for (unsigned I = 1, E = BitcodeFiles.size(); I != E; ++I)
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CG->addModule(BitcodeFiles[I]->getModule());
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std::string ErrMsg;
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LTOMB = CG->compile(false, false, false, ErrMsg); // take MB ownership
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if (!LTOMB) {
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llvm::errs() << ErrMsg << '\n';
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return make_error_code(LLDError::BrokenFile);
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}
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auto *Obj = new ObjectFile(LTOMB->getMemBufferRef());
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Files.emplace_back(Obj);
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ObjectFiles.push_back(Obj);
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if (auto EC = Obj->parse())
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return EC;
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return Obj;
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}
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} // namespace coff
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} // namespace lld
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