llvm-project/lld/COFF/SymbolTable.cpp

381 lines
12 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 "LTO.h"
#include "Memory.h"
#include "Symbols.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 {
enum SymbolPreference {
SP_EXISTING = -1,
SP_CONFLICT = 0,
SP_NEW = 1,
};
/// Checks if an existing symbol S should be kept or replaced by a new symbol.
/// Returns SP_EXISTING when S should be kept, SP_NEW when the new symbol
/// should be kept, and SP_CONFLICT if no valid resolution exists.
static SymbolPreference compareDefined(Symbol *S, bool WasInserted,
bool NewIsCOMDAT) {
// If the symbol wasn't previously known, the new symbol wins by default.
if (WasInserted || !isa<Defined>(S->body()))
return SP_NEW;
// If the existing symbol is a DefinedRegular, both it and the new symbol
// must be comdats. In that case, we have no reason to prefer one symbol
// over the other, and we keep the existing one. If one of the symbols
// is not a comdat, we report a conflict.
if (auto *R = dyn_cast<DefinedRegular>(S->body())) {
if (NewIsCOMDAT && R->isCOMDAT())
return SP_EXISTING;
else
return SP_CONFLICT;
}
// Existing symbol is not a DefinedRegular; new symbol wins.
return SP_NEW;
}
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) {
fatal(toString(File) + ": machine type " + machineToStr(MT) +
" conflicts with " + machineToStr(Config->Machine));
}
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);
}
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))
warn("<root>: undefined symbol: " + B->getName());
for (ObjFile *File : ObjFile::Instances)
for (SymbolBody *Sym : File->getSymbols())
if (Undefs.count(Sym))
warn(toString(File) + ": undefined symbol: " + Sym->getName());
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) {
error("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::addSynthetic(StringRef N, Chunk *C) {
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) = insert(N);
S->IsUsedInRegularObj = true;
if (WasInserted || isa<Undefined>(S->body()) || isa<Lazy>(S->body()))
replaceBody<DefinedSynthetic>(S, N, C);
else if (!isa<DefinedCOFF>(S->body()))
reportDuplicate(S, nullptr);
return S;
}
Symbol *SymbolTable::addRegular(InputFile *F, StringRef N, bool IsCOMDAT,
const coff_symbol_generic *Sym,
SectionChunk *C) {
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) = insert(N);
if (!isa<BitcodeFile>(F))
S->IsUsedInRegularObj = true;
SymbolPreference SP = compareDefined(S, WasInserted, IsCOMDAT);
if (SP == SP_CONFLICT) {
reportDuplicate(S, F);
} else if (SP == SP_NEW) {
replaceBody<DefinedRegular>(S, F, N, IsCOMDAT, /*IsExternal*/ true, Sym, C);
} else if (SP == SP_EXISTING && IsCOMDAT && C) {
C->markDiscarded();
// Discard associative chunks that we've parsed so far. No need to recurse
// because an associative section cannot have children.
for (SectionChunk *Child : C->children())
Child->markDiscarded();
}
return S;
}
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);
if (!isa<BitcodeFile>(F))
S->IsUsedInRegularObj = true;
if (WasInserted || !isa<DefinedCOFF>(S->body()))
replaceBody<DefinedCommon>(S, F, N, Size, Sym, C);
else if (auto *DC = dyn_cast<DefinedCommon>(S->body()))
if (Size > DC->getSize())
replaceBody<DefinedCommon>(S, F, N, Size, Sym, C);
return S;
}
DefinedImportData *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);
return cast<DefinedImportData>(S->body());
}
reportDuplicate(S, F);
return nullptr;
}
DefinedImportThunk *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);
return cast<DefinedImportThunk>(S->body());
}
reportDuplicate(S, ID->File);
return nullptr;
}
std::vector<Chunk *> SymbolTable::getChunks() {
std::vector<Chunk *> Res;
for (ObjFile *File : ObjFile::Instances) {
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();
}
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;
for (StringRef Object : compileBitcodeFiles()) {
auto *Obj = make<ObjFile>(MemoryBufferRef(Object, "lto.tmp"));
Obj->parse();
ObjFile::Instances.push_back(Obj);
}
}
} // namespace coff
} // namespace lld