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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 "Error.h"
#include "Symbols.h"
using namespace llvm;
using namespace llvm::object;
using namespace llvm::ELF;
using namespace lld;
using namespace lld::elf2;
template <class ELFT> SymbolTable<ELFT>::SymbolTable() {}
template <class ELFT> bool SymbolTable<ELFT>::shouldUseRela() const {
ELFKind K = getFirstELF()->getELFKind();
return K == ELF64LEKind || K == ELF64BEKind;
}
template <class ELFT>
void SymbolTable<ELFT>::addFile(std::unique_ptr<InputFile> File) {
if (auto *E = dyn_cast<ELFFileBase>(File.get())) {
if (E->getELFKind() != Config->ElfKind ||
E->getEMachine() != Config->EMachine) {
StringRef A = E->getName();
StringRef B = Config->Emulation;
if (B.empty())
B = Config->FirstElf->getName();
error(A + " is incompatible with " + B);
}
}
if (auto *AF = dyn_cast<ArchiveFile>(File.get())) {
ArchiveFiles.emplace_back(std::move(File));
AF->parse();
for (Lazy &Sym : AF->getLazySymbols())
addLazy(&Sym);
return;
}
if (auto *S = dyn_cast<SharedFileBase>(File.get())) {
S->parseSoName();
if (!IncludedSoNames.insert(S->getSoName()).second)
return;
S->parse();
} else {
cast<ObjectFileBase>(File.get())->parse(Comdats);
}
addELFFile(cast<ELFFileBase>(File.release()));
}
template <class ELFT>
SymbolBody *SymbolTable<ELFT>::addUndefined(StringRef Name) {
auto *Sym = new (Alloc) Undefined<ELFT>(Name, Undefined<ELFT>::Required);
resolve(Sym);
return Sym;
}
template <class ELFT>
SymbolBody *SymbolTable<ELFT>::addUndefinedOpt(StringRef Name) {
auto *Sym = new (Alloc) Undefined<ELFT>(Name, Undefined<ELFT>::Optional);
resolve(Sym);
return Sym;
}
template <class ELFT>
void SymbolTable<ELFT>::addSyntheticSym(StringRef Name,
OutputSection<ELFT> &Section,
typename ELFFile<ELFT>::uintX_t Value) {
typedef typename DefinedSynthetic<ELFT>::Elf_Sym Elf_Sym;
auto ESym = new (Alloc) Elf_Sym;
memset(ESym, 0, sizeof(Elf_Sym));
ESym->st_value = Value;
auto Sym = new (Alloc) DefinedSynthetic<ELFT>(Name, *ESym, Section);
resolve(Sym);
}
template <class ELFT> void SymbolTable<ELFT>::addIgnoredSym(StringRef Name) {
auto Sym = new (Alloc)
DefinedAbsolute<ELFT>(Name, DefinedAbsolute<ELFT>::IgnoreUndef);
resolve(Sym);
}
template <class ELFT> void SymbolTable<ELFT>::addELFFile(ELFFileBase *File) {
if (auto *O = dyn_cast<ObjectFile<ELFT>>(File))
ObjectFiles.emplace_back(O);
else if (auto *S = dyn_cast<SharedFile<ELFT>>(File))
SharedFiles.emplace_back(S);
if (auto *O = dyn_cast<ObjectFileBase>(File)) {
for (SymbolBody *Body : O->getSymbols())
resolve(Body);
}
if (auto *S = dyn_cast<SharedFile<ELFT>>(File)) {
for (SharedSymbol<ELFT> &Body : S->getSharedSymbols())
resolve(&Body);
}
}
template <class ELFT>
void SymbolTable<ELFT>::reportConflict(const Twine &Message,
const SymbolBody &Old,
const SymbolBody &New, bool Warning) {
typedef typename ELFFile<ELFT>::Elf_Sym Elf_Sym;
typedef typename ELFFile<ELFT>::Elf_Sym_Range Elf_Sym_Range;
const Elf_Sym &OldE = cast<ELFSymbolBody<ELFT>>(Old).Sym;
const Elf_Sym &NewE = cast<ELFSymbolBody<ELFT>>(New).Sym;
ELFFileBase *OldFile = nullptr;
ELFFileBase *NewFile = nullptr;
for (const std::unique_ptr<ObjectFile<ELFT>> &File : ObjectFiles) {
Elf_Sym_Range Syms = File->getObj().symbols(File->getSymbolTable());
if (&OldE > Syms.begin() && &OldE < Syms.end())
OldFile = File.get();
if (&NewE > Syms.begin() && &NewE < Syms.end())
NewFile = File.get();
}
std::string Msg = (Message + ": " + Old.getName() + " in " +
OldFile->getName() + " and " + NewFile->getName())
.str();
if (Warning)
warning(Msg);
else
error(Msg);
}
// This function resolves conflicts if there's an existing symbol with
// the same name. Decisions are made based on symbol type.
template <class ELFT> void SymbolTable<ELFT>::resolve(SymbolBody *New) {
Symbol *Sym = insert(New);
if (Sym->Body == New)
return;
SymbolBody *Existing = Sym->Body;
if (Lazy *L = dyn_cast<Lazy>(Existing)) {
if (New->isUndefined()) {
if (New->isWeak()) {
// See the explanation in SymbolTable::addLazy
L->setUsedInRegularObj();
L->setWeak();
return;
}
addMemberFile(L);
return;
}
// Found a definition for something also in an archive. Ignore the archive
// definition.
Sym->Body = New;
return;
}
if (New->isTLS() != Existing->isTLS())
reportConflict("TLS attribute mismatch for symbol", *Existing, *New, false);
// compare() returns -1, 0, or 1 if the lhs symbol is less preferable,
// equivalent (conflicting), or more preferable, respectively.
int comp = Existing->compare<ELFT>(New);
if (comp < 0)
Sym->Body = New;
else if (comp == 0)
reportConflict("duplicate symbol", *Existing, *New,
Config->AllowMultipleDefinition);
}
template <class ELFT> Symbol *SymbolTable<ELFT>::insert(SymbolBody *New) {
// Find an existing Symbol or create and insert a new one.
StringRef Name = New->getName();
Symbol *&Sym = Symtab[Name];
if (!Sym) {
Sym = new (Alloc) Symbol(New);
New->setBackref(Sym);
return Sym;
}
New->setBackref(Sym);
return Sym;
}
template <class ELFT> void SymbolTable<ELFT>::addLazy(Lazy *New) {
Symbol *Sym = insert(New);
if (Sym->Body == New)
return;
SymbolBody *Existing = Sym->Body;
if (Existing->isDefined() || Existing->isLazy())
return;
Sym->Body = New;
assert(Existing->isUndefined() && "Unexpected symbol kind.");
// Weak undefined symbols should not fetch members from archives.
// If we were to keep old symbol we would not know that an archive member was
// available if a strong undefined symbol shows up afterwards in the link.
// If a strong undefined symbol never shows up, this lazy symbol will
// get to the end of the link and must be treated as the weak undefined one.
// We set UsedInRegularObj in a similar way to what is done with shared
// symbols and mark it as weak to reduce how many special cases are needed.
if (Existing->isWeak()) {
New->setUsedInRegularObj();
New->setWeak();
return;
}
addMemberFile(New);
}
template <class ELFT> void SymbolTable<ELFT>::addMemberFile(Lazy *Body) {
std::unique_ptr<InputFile> File = Body->getMember();
// getMember returns nullptr if the member was already read from the library.
if (!File)
return;
addFile(std::move(File));
}
template class lld::elf2::SymbolTable<ELF32LE>;
template class lld::elf2::SymbolTable<ELF32BE>;
template class lld::elf2::SymbolTable<ELF64LE>;
template class lld::elf2::SymbolTable<ELF64BE>;
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