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llvm-project/lld/COFF/SymbolTable.cpp

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//===- 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 "LTO.h"
#include "PDB.h"
#include "Symbols.h"
#include "lld/Common/ErrorHandler.h"
#include "lld/Common/Memory.h"
#include "lld/Common/Timer.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include <utility>
using namespace llvm;
namespace lld {
namespace coff {
static Timer LTOTimer("LTO", Timer::root());
SymbolTable *Symtab;
void SymbolTable::addFile(InputFile *File) {
log("Reading " + toString(File));
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) {
error(toString(File) + ": machine type " + machineToStr(MT) +
" conflicts with " + machineToStr(Config->Machine));
return;
}
if (auto *F = dyn_cast<ObjFile>(File)) {
ObjFile::Instances.push_back(F);
} else if (auto *F = dyn_cast<BitcodeFile>(File)) {
BitcodeFile::Instances.push_back(F);
} else if (auto *F = dyn_cast<ImportFile>(File)) {
ImportFile::Instances.push_back(F);
}
StringRef S = File->getDirectives();
if (S.empty())
return;
log("Directives: " + toString(File) + ": " + S);
Driver->parseDirectives(S);
}
static void errorOrWarn(const Twine &S) {
if (Config->ForceUnresolved)
warn(S);
else
error(S);
}
// Returns the symbol in SC whose value is <= Addr that is closest to Addr.
// This is generally the global variable or function whose definition contains
// Addr.
static Symbol *getSymbol(SectionChunk *SC, uint32_t Addr) {
DefinedRegular *Candidate = nullptr;
for (Symbol *S : SC->File->getSymbols()) {
auto *D = dyn_cast_or_null<DefinedRegular>(S);
if (!D || D->getChunk() != SC || D->getValue() > Addr ||
(Candidate && D->getValue() < Candidate->getValue()))
continue;
Candidate = D;
}
return Candidate;
}
std::string getSymbolLocations(ObjFile *File, uint32_t SymIndex) {
struct Location {
Symbol *Sym;
std::pair<StringRef, uint32_t> FileLine;
};
std::vector<Location> Locations;
for (Chunk *C : File->getChunks()) {
auto *SC = dyn_cast<SectionChunk>(C);
if (!SC)
continue;
for (const coff_relocation &R : SC->Relocs) {
if (R.SymbolTableIndex != SymIndex)
continue;
std::pair<StringRef, uint32_t> FileLine =
getFileLine(SC, R.VirtualAddress);
Symbol *Sym = getSymbol(SC, R.VirtualAddress);
if (!FileLine.first.empty() || Sym)
Locations.push_back({Sym, FileLine});
}
}
if (Locations.empty())
return "\n>>> referenced by " + toString(File);
std::string Out;
llvm::raw_string_ostream OS(Out);
for (Location Loc : Locations) {
OS << "\n>>> referenced by ";
if (!Loc.FileLine.first.empty())
OS << Loc.FileLine.first << ":" << Loc.FileLine.second
<< "\n>>> ";
OS << toString(File);
if (Loc.Sym)
OS << ":(" << toString(*Loc.Sym) << ')';
}
return OS.str();
}
void SymbolTable::loadMinGWAutomaticImports() {
for (auto &I : SymMap) {
Symbol *Sym = I.second;
auto *Undef = dyn_cast<Undefined>(Sym);
if (!Undef)
continue;
if (!Sym->IsUsedInRegularObj)
continue;
StringRef Name = Undef->getName();
if (Name.startswith("__imp_"))
continue;
// If we have an undefined symbol, but we have a Lazy representing a
// symbol we could load from file, make sure to load that.
Lazy *L = dyn_cast_or_null<Lazy>(find(("__imp_" + Name).str()));
if (!L || L->PendingArchiveLoad)
continue;
log("Loading lazy " + L->getName() + " from " + L->File->getName() +
" for automatic import");
L->PendingArchiveLoad = true;
L->File->addMember(&L->Sym);
}
}
bool SymbolTable::handleMinGWAutomaticImport(Symbol *Sym, StringRef Name) {
if (Name.startswith("__imp_"))
return false;
Defined *Imp = dyn_cast_or_null<Defined>(find(("__imp_" + Name).str()));
if (!Imp)
return false;
// Replace the reference directly to a variable with a reference
// to the import address table instead. This obviously isn't right,
// but we mark the symbol as IsRuntimePseudoReloc, and a later pass
// will add runtime pseudo relocations for every relocation against
// this Symbol. The runtime pseudo relocation framework expects the
// reference itself to point at the IAT entry.
size_t ImpSize = 0;
if (isa<DefinedImportData>(Imp)) {
log("Automatically importing " + Name + " from " +
cast<DefinedImportData>(Imp)->getDLLName());
ImpSize = sizeof(DefinedImportData);
} else if (isa<DefinedRegular>(Imp)) {
log("Automatically importing " + Name + " from " +
toString(cast<DefinedRegular>(Imp)->File));
ImpSize = sizeof(DefinedRegular);
} else {
warn("unable to automatically import " + Name + " from " + Imp->getName() +
" from " + toString(cast<DefinedRegular>(Imp)->File) +
"; unexpected symbol type");
return false;
}
Sym->replaceKeepingName(Imp, ImpSize);
Sym->IsRuntimePseudoReloc = true;
// There may exist symbols named .refptr.<name> which only consist
// of a single pointer to <name>. If it turns out <name> is
// automatically imported, we don't need to keep the .refptr.<name>
// pointer at all, but redirect all accesses to it to the IAT entry
// for __imp_<name> instead, and drop the whole .refptr.<name> chunk.
DefinedRegular *Refptr =
dyn_cast_or_null<DefinedRegular>(find((".refptr." + Name).str()));
if (Refptr && Refptr->getChunk()->getSize() == Config->Wordsize) {
SectionChunk *SC = dyn_cast_or_null<SectionChunk>(Refptr->getChunk());
if (SC && SC->Relocs.size() == 1 && *SC->symbols().begin() == Sym) {
log("Replacing .refptr." + Name + " with " + Imp->getName());
Refptr->getChunk()->Live = false;
Refptr->replaceKeepingName(Imp, ImpSize);
}
}
return true;
}
void SymbolTable::reportRemainingUndefines() {
SmallPtrSet<Symbol *, 8> Undefs;
DenseMap<Symbol *, Symbol *> LocalImports;
for (auto &I : SymMap) {
Symbol *Sym = I.second;
auto *Undef = dyn_cast<Undefined>(Sym);
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 want to replace Sym with D. However, we can't just blindly
// copy sizeof(SymbolUnion) bytes from D to Sym because D may be an
// internal symbol, and internal symbols are stored as "unparented"
// Symbols. 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, D, sizeof(DefinedRegular));
else if (isa<DefinedAbsolute>(D))
memcpy(Sym, D, sizeof(DefinedAbsolute));
else
memcpy(Sym, D, sizeof(SymbolUnion));
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)) {
auto *D = cast<Defined>(Imp);
replaceSymbol<DefinedLocalImport>(Sym, Name, D);
LocalImportChunks.push_back(cast<DefinedLocalImport>(Sym)->getChunk());
LocalImports[Sym] = D;
continue;
}
}
// We don't want to report missing Microsoft precompiled headers symbols.
// A proper message will be emitted instead in PDBLinker::aquirePrecompObj
if (Name.contains("_PchSym_"))
continue;
if (Config->MinGW && handleMinGWAutomaticImport(Sym, Name))
continue;
// Remaining undefined symbols are not fatal if /force is specified.
// They are replaced with dummy defined symbols.
if (Config->ForceUnresolved)
replaceSymbol<DefinedAbsolute>(Sym, Name, 0);
Undefs.insert(Sym);
}
if (Undefs.empty() && LocalImports.empty())
return;
for (Symbol *B : Config->GCRoot) {
if (Undefs.count(B))
errorOrWarn("<root>: undefined symbol: " + toString(*B));
if (Config->WarnLocallyDefinedImported)
if (Symbol *Imp = LocalImports.lookup(B))
warn("<root>: locally defined symbol imported: " + toString(*Imp) +
" (defined in " + toString(Imp->getFile()) + ") [LNK4217]");
}
for (ObjFile *File : ObjFile::Instances) {
size_t SymIndex = (size_t)-1;
for (Symbol *Sym : File->getSymbols()) {
++SymIndex;
if (!Sym)
continue;
if (Undefs.count(Sym))
errorOrWarn("undefined symbol: " + toString(*Sym) +
getSymbolLocations(File, SymIndex));
if (Config->WarnLocallyDefinedImported)
if (Symbol *Imp = LocalImports.lookup(Sym))
warn(toString(File) +
": locally defined symbol imported: " + toString(*Imp) +
" (defined in " + toString(Imp->getFile()) + ") [LNK4217]");
}
}
}
std::pair<Symbol *, bool> SymbolTable::insert(StringRef Name) {
bool Inserted = false;
Symbol *&Sym = SymMap[CachedHashStringRef(Name)];
if (!Sym) {
Sym = reinterpret_cast<Symbol *>(make<SymbolUnion>());
Sym->IsUsedInRegularObj = false;
Sym->PendingArchiveLoad = false;
Inserted = true;
}
return {Sym, Inserted};
}
std::pair<Symbol *, bool> SymbolTable::insert(StringRef Name, InputFile *File) {
std::pair<Symbol *, bool> Result = insert(Name);
if (!File || !isa<BitcodeFile>(File))
Result.first->IsUsedInRegularObj = true;
return Result;
}
Symbol *SymbolTable::addUndefined(StringRef Name, InputFile *F,
bool IsWeakAlias) {
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) = insert(Name, F);
if (WasInserted || (isa<Lazy>(S) && IsWeakAlias)) {
replaceSymbol<Undefined>(S, Name);
return S;
}
if (auto *L = dyn_cast<Lazy>(S)) {
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) {
replaceSymbol<Lazy>(S, F, Sym);
return;
}
auto *U = dyn_cast<Undefined>(S);
if (!U || U->WeakAlias || S->PendingArchiveLoad)
return;
S->PendingArchiveLoad = true;
F->addMember(&Sym);
}
void SymbolTable::reportDuplicate(Symbol *Existing, InputFile *NewFile) {
std::string Msg = "duplicate symbol: " + toString(*Existing) + " in " +
toString(Existing->getFile()) + " and in " +
toString(NewFile);
if (Config->ForceMultiple)
warn(Msg);
else
error(Msg);
}
Symbol *SymbolTable::addAbsolute(StringRef N, COFFSymbolRef Sym) {
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) = insert(N, nullptr);
S->IsUsedInRegularObj = true;
if (WasInserted || isa<Undefined>(S) || isa<Lazy>(S))
replaceSymbol<DefinedAbsolute>(S, N, Sym);
else if (!isa<DefinedCOFF>(S))
reportDuplicate(S, nullptr);
return S;
}
Symbol *SymbolTable::addAbsolute(StringRef N, uint64_t VA) {
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) = insert(N, nullptr);
S->IsUsedInRegularObj = true;
if (WasInserted || isa<Undefined>(S) || isa<Lazy>(S))
replaceSymbol<DefinedAbsolute>(S, N, VA);
else if (!isa<DefinedCOFF>(S))
reportDuplicate(S, nullptr);
return S;
}
Symbol *SymbolTable::addSynthetic(StringRef N, Chunk *C) {
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) = insert(N, nullptr);
S->IsUsedInRegularObj = true;
if (WasInserted || isa<Undefined>(S) || isa<Lazy>(S))
replaceSymbol<DefinedSynthetic>(S, N, C);
else if (!isa<DefinedCOFF>(S))
reportDuplicate(S, nullptr);
return S;
}
Symbol *SymbolTable::addRegular(InputFile *F, StringRef N,
const coff_symbol_generic *Sym,
SectionChunk *C) {
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) = insert(N, F);
if (WasInserted || !isa<DefinedRegular>(S))
replaceSymbol<DefinedRegular>(S, F, N, /*IsCOMDAT*/ false,
/*IsExternal*/ true, Sym, C);
else
reportDuplicate(S, F);
return S;
}
std::pair<Symbol *, bool>
SymbolTable::addComdat(InputFile *F, StringRef N,
const coff_symbol_generic *Sym) {
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) = insert(N, F);
if (WasInserted || !isa<DefinedRegular>(S)) {
replaceSymbol<DefinedRegular>(S, F, N, /*IsCOMDAT*/ true,
/*IsExternal*/ true, Sym, nullptr);
return {S, true};
}
if (!cast<DefinedRegular>(S)->isCOMDAT())
reportDuplicate(S, F);
return {S, false};
}
Symbol *SymbolTable::addCommon(InputFile *F, StringRef N, uint64_t Size,
const coff_symbol_generic *Sym, CommonChunk *C) {
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) = insert(N, F);
if (WasInserted || !isa<DefinedCOFF>(S))
replaceSymbol<DefinedCommon>(S, F, N, Size, Sym, C);
else if (auto *DC = dyn_cast<DefinedCommon>(S))
if (Size > DC->getSize())
replaceSymbol<DefinedCommon>(S, F, N, Size, Sym, C);
return S;
}
Symbol *SymbolTable::addImportData(StringRef N, ImportFile *F) {
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) = insert(N, nullptr);
S->IsUsedInRegularObj = true;
if (WasInserted || isa<Undefined>(S) || isa<Lazy>(S)) {
replaceSymbol<DefinedImportData>(S, N, F);
return S;
}
reportDuplicate(S, F);
return nullptr;
}
Symbol *SymbolTable::addImportThunk(StringRef Name, DefinedImportData *ID,
uint16_t Machine) {
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) = insert(Name, nullptr);
S->IsUsedInRegularObj = true;
if (WasInserted || isa<Undefined>(S) || isa<Lazy>(S)) {
replaceSymbol<DefinedImportThunk>(S, Name, ID, Machine);
return S;
}
reportDuplicate(S, ID->File);
return nullptr;
}
std::vector<Chunk *> SymbolTable::getChunks() {
std::vector<Chunk *> Res;
for (ObjFile *File : ObjFile::Instances) {
ArrayRef<Chunk *> V = File->getChunks();
Res.insert(Res.end(), V.begin(), V.end());
}
return Res;
}
Symbol *SymbolTable::find(StringRef Name) {
return SymMap.lookup(CachedHashStringRef(Name));
}
Symbol *SymbolTable::findUnderscore(StringRef Name) {
if (Config->Machine == I386)
return find(("_" + Name).str());
return find(Name);
}
StringRef SymbolTable::findByPrefix(StringRef Prefix) {
for (auto Pair : SymMap) {
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))
return Name;
if (Config->Machine != I386)
return findByPrefix(("?" + Name + "@@Y").str());
if (!Name.startswith("_"))
return "";
// Search for x86 stdcall function.
StringRef S = findByPrefix((Name + "@").str());
if (!S.empty())
return S;
// Search for x86 fastcall function.
S = findByPrefix(("@" + Name.substr(1) + "@").str());
if (!S.empty())
return S;
// Search for x86 vectorcall function.
S = findByPrefix((Name.substr(1) + "@@").str());
if (!S.empty())
return S;
// Search for x86 C++ non-member function.
return findByPrefix(("?" + Name.substr(1) + "@@Y").str());
}
void SymbolTable::mangleMaybe(Symbol *B) {
auto *U = dyn_cast<Undefined>(B);
if (!U || U->WeakAlias)
return;
StringRef Alias = findMangle(U->getName());
if (!Alias.empty()) {
log(U->getName() + " aliased to " + Alias);
U->WeakAlias = addUndefined(Alias);
}
}
Symbol *SymbolTable::addUndefined(StringRef Name) {
return addUndefined(Name, nullptr, false);
}
std::vector<StringRef> SymbolTable::compileBitcodeFiles() {
LTO.reset(new BitcodeCompiler);
for (BitcodeFile *F : BitcodeFile::Instances)
LTO->add(*F);
return LTO->compile();
}
void SymbolTable::addCombinedLTOObjects() {
if (BitcodeFile::Instances.empty())
return;
ScopedTimer T(LTOTimer);
for (StringRef Object : compileBitcodeFiles()) {
auto *Obj = make<ObjFile>(MemoryBufferRef(Object, "lto.tmp"));
Obj->parse();
ObjFile::Instances.push_back(Obj);
}
}
} // namespace coff
} // namespace lld
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