llvm-project/lld/COFF/SymbolTable.cpp

410 lines
13 KiB
C++

//===- SymbolTable.cpp ----------------------------------------------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "SymbolTable.h"
#include "Config.h"
#include "Driver.h"
#include "Error.h"
#include "Memory.h"
#include "Symbols.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/LTO/legacy/LTOCodeGenerator.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include <utility>
using namespace llvm;
namespace lld {
namespace coff {
SymbolTable *Symtab;
void SymbolTable::addFile(InputFile *File) {
if (Config->Verbose)
outs() << "Reading " << toString(File) << "\n";
File->parse();
MachineTypes MT = File->getMachineType();
if (Config->Machine == IMAGE_FILE_MACHINE_UNKNOWN) {
Config->Machine = MT;
} else if (MT != IMAGE_FILE_MACHINE_UNKNOWN && Config->Machine != MT) {
fatal(toString(File) + ": machine type " + machineToStr(MT) +
" conflicts with " + machineToStr(Config->Machine));
}
if (auto *F = dyn_cast<ObjectFile>(File)) {
ObjectFiles.push_back(F);
} else if (auto *F = dyn_cast<BitcodeFile>(File)) {
BitcodeFiles.push_back(F);
} else if (auto *F = dyn_cast<ImportFile>(File)) {
ImportFiles.push_back(F);
}
StringRef S = File->getDirectives();
if (S.empty())
return;
if (Config->Verbose)
outs() << "Directives: " << toString(File) << ": " << S << "\n";
Driver->parseDirectives(S);
}
void SymbolTable::reportRemainingUndefines() {
SmallPtrSet<SymbolBody *, 8> Undefs;
for (auto &I : Symtab) {
Symbol *Sym = I.second;
auto *Undef = dyn_cast<Undefined>(Sym->body());
if (!Undef)
continue;
if (!Sym->IsUsedInRegularObj)
continue;
StringRef Name = Undef->getName();
// A weak alias may have been resolved, so check for that.
if (Defined *D = Undef->getWeakAlias()) {
// We resolve weak aliases by replacing the alias's SymbolBody with the
// target's SymbolBody. This causes all SymbolBody pointers referring to
// the old symbol to instead refer to the new symbol. However, we can't
// just blindly copy sizeof(Symbol::Body) bytes from D to Sym->Body
// because D may be an internal symbol, and internal symbols are stored as
// "unparented" SymbolBodies. For that reason we need to check which type
// of symbol we are dealing with and copy the correct number of bytes.
if (isa<DefinedRegular>(D))
memcpy(Sym->Body.buffer, D, sizeof(DefinedRegular));
else if (isa<DefinedAbsolute>(D))
memcpy(Sym->Body.buffer, D, sizeof(DefinedAbsolute));
else
// No other internal symbols are possible.
Sym->Body = D->symbol()->Body;
continue;
}
// If we can resolve a symbol by removing __imp_ prefix, do that.
// This odd rule is for compatibility with MSVC linker.
if (Name.startswith("__imp_")) {
Symbol *Imp = find(Name.substr(strlen("__imp_")));
if (Imp && isa<Defined>(Imp->body())) {
auto *D = cast<Defined>(Imp->body());
replaceBody<DefinedLocalImport>(Sym, Name, D);
LocalImportChunks.push_back(
cast<DefinedLocalImport>(Sym->body())->getChunk());
continue;
}
}
// Remaining undefined symbols are not fatal if /force is specified.
// They are replaced with dummy defined symbols.
if (Config->Force)
replaceBody<DefinedAbsolute>(Sym, Name, 0);
Undefs.insert(Sym->body());
}
if (Undefs.empty())
return;
for (SymbolBody *B : Config->GCRoot)
if (Undefs.count(B))
errs() << "<root>: undefined symbol: " << B->getName() << "\n";
for (ObjectFile *File : ObjectFiles)
for (SymbolBody *Sym : File->getSymbols())
if (Undefs.count(Sym))
errs() << toString(File) << ": undefined symbol: " << Sym->getName()
<< "\n";
if (!Config->Force)
fatal("link failed");
}
std::pair<Symbol *, bool> SymbolTable::insert(StringRef Name) {
Symbol *&Sym = Symtab[CachedHashStringRef(Name)];
if (Sym)
return {Sym, false};
Sym = make<Symbol>();
Sym->IsUsedInRegularObj = false;
Sym->PendingArchiveLoad = false;
return {Sym, true};
}
Symbol *SymbolTable::addUndefined(StringRef Name, InputFile *F,
bool IsWeakAlias) {
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) = insert(Name);
if (!F || !isa<BitcodeFile>(F))
S->IsUsedInRegularObj = true;
if (WasInserted || (isa<Lazy>(S->body()) && IsWeakAlias)) {
replaceBody<Undefined>(S, Name);
return S;
}
if (auto *L = dyn_cast<Lazy>(S->body())) {
if (!S->PendingArchiveLoad) {
S->PendingArchiveLoad = true;
L->File->addMember(&L->Sym);
}
}
return S;
}
void SymbolTable::addLazy(ArchiveFile *F, const Archive::Symbol Sym) {
StringRef Name = Sym.getName();
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) = insert(Name);
if (WasInserted) {
replaceBody<Lazy>(S, F, Sym);
return;
}
auto *U = dyn_cast<Undefined>(S->body());
if (!U || U->WeakAlias || S->PendingArchiveLoad)
return;
S->PendingArchiveLoad = true;
F->addMember(&Sym);
}
void SymbolTable::reportDuplicate(Symbol *Existing, InputFile *NewFile) {
fatal("duplicate symbol: " + toString(*Existing->body()) + " in " +
toString(Existing->body()->getFile()) + " and in " +
(NewFile ? toString(NewFile) : "(internal)"));
}
Symbol *SymbolTable::addAbsolute(StringRef N, COFFSymbolRef Sym) {
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) = insert(N);
S->IsUsedInRegularObj = true;
if (WasInserted || isa<Undefined>(S->body()) || isa<Lazy>(S->body()))
replaceBody<DefinedAbsolute>(S, N, Sym);
else if (!isa<DefinedCOFF>(S->body()))
reportDuplicate(S, nullptr);
return S;
}
Symbol *SymbolTable::addAbsolute(StringRef N, uint64_t VA) {
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) = insert(N);
S->IsUsedInRegularObj = true;
if (WasInserted || isa<Undefined>(S->body()) || isa<Lazy>(S->body()))
replaceBody<DefinedAbsolute>(S, N, VA);
else if (!isa<DefinedCOFF>(S->body()))
reportDuplicate(S, nullptr);
return S;
}
Symbol *SymbolTable::addRelative(StringRef N, uint64_t VA) {
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) = insert(N);
S->IsUsedInRegularObj = true;
if (WasInserted || isa<Undefined>(S->body()) || isa<Lazy>(S->body()))
replaceBody<DefinedRelative>(S, N, VA);
else if (!isa<DefinedCOFF>(S->body()))
reportDuplicate(S, nullptr);
return S;
}
Symbol *SymbolTable::addRegular(ObjectFile *F, COFFSymbolRef Sym,
SectionChunk *C) {
StringRef Name;
F->getCOFFObj()->getSymbolName(Sym, Name);
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) = insert(Name);
S->IsUsedInRegularObj = true;
if (WasInserted || isa<Undefined>(S->body()) || isa<Lazy>(S->body()))
replaceBody<DefinedRegular>(S, F, Sym, C);
else if (auto *R = dyn_cast<DefinedRegular>(S->body())) {
if (!C->isCOMDAT() || !R->isCOMDAT())
reportDuplicate(S, F);
} else if (auto *B = dyn_cast<DefinedBitcode>(S->body())) {
if (B->IsReplaceable)
replaceBody<DefinedRegular>(S, F, Sym, C);
else if (!C->isCOMDAT())
reportDuplicate(S, F);
} else
replaceBody<DefinedRegular>(S, F, Sym, C);
return S;
}
Symbol *SymbolTable::addBitcode(BitcodeFile *F, StringRef N, bool IsReplaceable) {
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) = insert(N);
if (WasInserted || isa<Undefined>(S->body()) || isa<Lazy>(S->body())) {
replaceBody<DefinedBitcode>(S, F, N, IsReplaceable);
return S;
}
if (isa<DefinedCommon>(S->body()))
return S;
if (IsReplaceable)
if (isa<DefinedRegular>(S->body()) || isa<DefinedBitcode>(S->body()))
return S;
reportDuplicate(S, F);
return S;
}
Symbol *SymbolTable::addCommon(ObjectFile *F, COFFSymbolRef Sym,
CommonChunk *C) {
StringRef Name;
F->getCOFFObj()->getSymbolName(Sym, Name);
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) = insert(Name);
S->IsUsedInRegularObj = true;
if (WasInserted || !isa<DefinedCOFF>(S->body()))
replaceBody<DefinedCommon>(S, F, Sym, C);
else if (auto *DC = dyn_cast<DefinedCommon>(S->body()))
if (Sym.getValue() > DC->getSize())
replaceBody<DefinedCommon>(S, F, Sym, C);
return S;
}
Symbol *SymbolTable::addImportData(StringRef N, ImportFile *F) {
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) = insert(N);
S->IsUsedInRegularObj = true;
if (WasInserted || isa<Undefined>(S->body()) || isa<Lazy>(S->body()))
replaceBody<DefinedImportData>(S, N, F);
else if (!isa<DefinedCOFF>(S->body()))
reportDuplicate(S, nullptr);
return S;
}
Symbol *SymbolTable::addImportThunk(StringRef Name, DefinedImportData *ID,
uint16_t Machine) {
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) = insert(Name);
S->IsUsedInRegularObj = true;
if (WasInserted || isa<Undefined>(S->body()) || isa<Lazy>(S->body()))
replaceBody<DefinedImportThunk>(S, Name, ID, Machine);
else if (!isa<DefinedCOFF>(S->body()))
reportDuplicate(S, nullptr);
return S;
}
std::vector<Chunk *> SymbolTable::getChunks() {
std::vector<Chunk *> Res;
for (ObjectFile *File : ObjectFiles) {
std::vector<Chunk *> &V = File->getChunks();
Res.insert(Res.end(), V.begin(), V.end());
}
return Res;
}
Symbol *SymbolTable::find(StringRef Name) {
auto It = Symtab.find(CachedHashStringRef(Name));
if (It == Symtab.end())
return nullptr;
return It->second;
}
Symbol *SymbolTable::findUnderscore(StringRef Name) {
if (Config->Machine == I386)
return find(("_" + Name).str());
return find(Name);
}
StringRef SymbolTable::findByPrefix(StringRef Prefix) {
for (auto Pair : Symtab) {
StringRef Name = Pair.first.val();
if (Name.startswith(Prefix))
return Name;
}
return "";
}
StringRef SymbolTable::findMangle(StringRef Name) {
if (Symbol *Sym = find(Name))
if (!isa<Undefined>(Sym->body()))
return Name;
if (Config->Machine != I386)
return findByPrefix(("?" + Name + "@@Y").str());
if (!Name.startswith("_"))
return "";
// Search for x86 C function.
StringRef S = findByPrefix((Name + "@").str());
if (!S.empty())
return S;
// Search for x86 C++ non-member function.
return findByPrefix(("?" + Name.substr(1) + "@@Y").str());
}
void SymbolTable::mangleMaybe(SymbolBody *B) {
auto *U = dyn_cast<Undefined>(B);
if (!U || U->WeakAlias)
return;
StringRef Alias = findMangle(U->getName());
if (!Alias.empty())
U->WeakAlias = addUndefined(Alias);
}
SymbolBody *SymbolTable::addUndefined(StringRef Name) {
return addUndefined(Name, nullptr, false)->body();
}
void SymbolTable::addCombinedLTOObjects() {
if (BitcodeFiles.empty())
return;
// Create an object file and add it to the symbol table by replacing any
// DefinedBitcode symbols with the definitions in the object file.
LTOCodeGenerator CG(BitcodeFile::Context);
CG.setOptLevel(Config->LTOOptLevel);
for (ObjectFile *Obj : createLTOObjects(&CG))
Obj->parse();
}
// Combine and compile bitcode files and then return the result
// as a vector of regular COFF object files.
std::vector<ObjectFile *> SymbolTable::createLTOObjects(LTOCodeGenerator *CG) {
// All symbols referenced by non-bitcode objects, including GC roots, must be
// preserved. We must also replace bitcode symbols with undefined symbols so
// that they may be replaced with real definitions without conflicting.
for (BitcodeFile *File : BitcodeFiles)
for (SymbolBody *Body : File->getSymbols()) {
if (!isa<DefinedBitcode>(Body))
continue;
if (Body->symbol()->IsUsedInRegularObj)
CG->addMustPreserveSymbol(Body->getName());
replaceBody<Undefined>(Body->symbol(), Body->getName());
}
CG->setModule(BitcodeFiles[0]->takeModule());
for (unsigned I = 1, E = BitcodeFiles.size(); I != E; ++I)
CG->addModule(BitcodeFiles[I]->takeModule().get());
bool DisableVerify = true;
#ifdef NDEBUG
DisableVerify = false;
#endif
if (!CG->optimize(DisableVerify, false, false, false))
fatal(""); // optimize() should have emitted any error message.
Objs.resize(Config->LTOJobs);
// Use std::list to avoid invalidation of pointers in OSPtrs.
std::list<raw_svector_ostream> OSs;
std::vector<raw_pwrite_stream *> OSPtrs;
for (SmallString<0> &Obj : Objs) {
OSs.emplace_back(Obj);
OSPtrs.push_back(&OSs.back());
}
if (!CG->compileOptimized(OSPtrs))
fatal(""); // compileOptimized() should have emitted any error message.
std::vector<ObjectFile *> ObjFiles;
for (SmallString<0> &Obj : Objs) {
auto *ObjFile = make<ObjectFile>(MemoryBufferRef(Obj, "<LTO object>"));
ObjectFiles.push_back(ObjFile);
ObjFiles.push_back(ObjFile);
}
return ObjFiles;
}
} // namespace coff
} // namespace lld