llvm-project/lld/MachO/SymbolTable.cpp

449 lines
15 KiB
C++

//===- SymbolTable.cpp ----------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "SymbolTable.h"
#include "ConcatOutputSection.h"
#include "Config.h"
#include "InputFiles.h"
#include "InputSection.h"
#include "Symbols.h"
#include "SyntheticSections.h"
#include "lld/Common/ErrorHandler.h"
#include "lld/Common/Memory.h"
using namespace llvm;
using namespace lld;
using namespace lld::macho;
Symbol *SymbolTable::find(CachedHashStringRef cachedName) {
auto it = symMap.find(cachedName);
if (it == symMap.end())
return nullptr;
return symVector[it->second];
}
std::pair<Symbol *, bool> SymbolTable::insert(StringRef name,
const InputFile *file) {
auto p = symMap.insert({CachedHashStringRef(name), (int)symVector.size()});
Symbol *sym;
if (!p.second) {
// Name already present in the symbol table.
sym = symVector[p.first->second];
} else {
// Name is a new symbol.
sym = reinterpret_cast<Symbol *>(make<SymbolUnion>());
symVector.push_back(sym);
}
sym->isUsedInRegularObj |= !file || isa<ObjFile>(file);
return {sym, p.second};
}
Defined *SymbolTable::addDefined(StringRef name, InputFile *file,
InputSection *isec, uint64_t value,
uint64_t size, bool isWeakDef,
bool isPrivateExtern, bool isThumb,
bool isReferencedDynamically, bool noDeadStrip,
bool isWeakDefCanBeHidden) {
Symbol *s;
bool wasInserted;
bool overridesWeakDef = false;
std::tie(s, wasInserted) = insert(name, file);
assert(!isWeakDef || (isa<BitcodeFile>(file) && !isec) ||
(isa<ObjFile>(file) && file == isec->getFile()));
if (!wasInserted) {
if (auto *defined = dyn_cast<Defined>(s)) {
if (isWeakDef) {
// See further comment in createDefined() in InputFiles.cpp
if (defined->isWeakDef()) {
defined->privateExtern &= isPrivateExtern;
defined->weakDefCanBeHidden &= isWeakDefCanBeHidden;
defined->referencedDynamically |= isReferencedDynamically;
defined->noDeadStrip |= noDeadStrip;
}
// FIXME: Handle this for bitcode files.
if (auto concatIsec = dyn_cast_or_null<ConcatInputSection>(isec))
concatIsec->wasCoalesced = true;
return defined;
}
if (defined->isWeakDef()) {
// FIXME: Handle this for bitcode files.
if (auto concatIsec =
dyn_cast_or_null<ConcatInputSection>(defined->isec)) {
concatIsec->wasCoalesced = true;
concatIsec->symbols.erase(llvm::find(concatIsec->symbols, defined));
}
} else {
std::string src1 = defined->getSourceLocation();
std::string src2 = isec ? isec->getSourceLocation(value) : "";
std::string message =
"duplicate symbol: " + toString(*defined) + "\n>>> defined in ";
if (!src1.empty())
message += src1 + "\n>>> ";
message += toString(defined->getFile()) + "\n>>> defined in ";
if (!src2.empty())
message += src2 + "\n>>> ";
error(message + toString(file));
}
} else if (auto *dysym = dyn_cast<DylibSymbol>(s)) {
overridesWeakDef = !isWeakDef && dysym->isWeakDef();
dysym->unreference();
}
// Defined symbols take priority over other types of symbols, so in case
// of a name conflict, we fall through to the replaceSymbol() call below.
}
// With -flat_namespace, all extern symbols in dylibs are interposable.
// FIXME: Add support for `-interposable` (PR53680).
bool interposable = config->namespaceKind == NamespaceKind::flat &&
config->outputType != MachO::MH_EXECUTE &&
!isPrivateExtern;
Defined *defined = replaceSymbol<Defined>(
s, name, file, isec, value, size, isWeakDef, /*isExternal=*/true,
isPrivateExtern, /*includeInSymtab=*/true, isThumb,
isReferencedDynamically, noDeadStrip, overridesWeakDef,
isWeakDefCanBeHidden, interposable);
return defined;
}
Defined *SymbolTable::aliasDefined(Defined *src, StringRef target) {
return addDefined(target, src->getFile(), src->isec, src->value, src->size,
src->isWeakDef(), src->privateExtern, src->thumb,
src->referencedDynamically, src->noDeadStrip,
src->weakDefCanBeHidden);
}
Symbol *SymbolTable::addUndefined(StringRef name, InputFile *file,
bool isWeakRef) {
Symbol *s;
bool wasInserted;
std::tie(s, wasInserted) = insert(name, file);
RefState refState = isWeakRef ? RefState::Weak : RefState::Strong;
if (wasInserted)
replaceSymbol<Undefined>(s, name, file, refState);
else if (auto *lazy = dyn_cast<LazyArchive>(s))
lazy->fetchArchiveMember();
else if (isa<LazyObject>(s))
extract(*s->getFile(), s->getName());
else if (auto *dynsym = dyn_cast<DylibSymbol>(s))
dynsym->reference(refState);
else if (auto *undefined = dyn_cast<Undefined>(s))
undefined->refState = std::max(undefined->refState, refState);
return s;
}
Symbol *SymbolTable::addCommon(StringRef name, InputFile *file, uint64_t size,
uint32_t align, bool isPrivateExtern) {
Symbol *s;
bool wasInserted;
std::tie(s, wasInserted) = insert(name, file);
if (!wasInserted) {
if (auto *common = dyn_cast<CommonSymbol>(s)) {
if (size < common->size)
return s;
} else if (isa<Defined>(s)) {
return s;
}
// Common symbols take priority over all non-Defined symbols, so in case of
// a name conflict, we fall through to the replaceSymbol() call below.
}
replaceSymbol<CommonSymbol>(s, name, file, size, align, isPrivateExtern);
return s;
}
Symbol *SymbolTable::addDylib(StringRef name, DylibFile *file, bool isWeakDef,
bool isTlv) {
Symbol *s;
bool wasInserted;
std::tie(s, wasInserted) = insert(name, file);
RefState refState = RefState::Unreferenced;
if (!wasInserted) {
if (auto *defined = dyn_cast<Defined>(s)) {
if (isWeakDef && !defined->isWeakDef())
defined->overridesWeakDef = true;
} else if (auto *undefined = dyn_cast<Undefined>(s)) {
refState = undefined->refState;
} else if (auto *dysym = dyn_cast<DylibSymbol>(s)) {
refState = dysym->getRefState();
}
}
bool isDynamicLookup = file == nullptr;
if (wasInserted || isa<Undefined>(s) ||
(isa<DylibSymbol>(s) &&
((!isWeakDef && s->isWeakDef()) ||
(!isDynamicLookup && cast<DylibSymbol>(s)->isDynamicLookup())))) {
if (auto *dynsym = dyn_cast<DylibSymbol>(s))
dynsym->unreference();
replaceSymbol<DylibSymbol>(s, file, name, isWeakDef, refState, isTlv);
}
return s;
}
Symbol *SymbolTable::addDynamicLookup(StringRef name) {
return addDylib(name, /*file=*/nullptr, /*isWeakDef=*/false, /*isTlv=*/false);
}
Symbol *SymbolTable::addLazyArchive(StringRef name, ArchiveFile *file,
const object::Archive::Symbol &sym) {
Symbol *s;
bool wasInserted;
std::tie(s, wasInserted) = insert(name, file);
if (wasInserted) {
replaceSymbol<LazyArchive>(s, file, sym);
} else if (isa<Undefined>(s)) {
file->fetch(sym);
} else if (auto *dysym = dyn_cast<DylibSymbol>(s)) {
if (dysym->isWeakDef()) {
if (dysym->getRefState() != RefState::Unreferenced)
file->fetch(sym);
else
replaceSymbol<LazyArchive>(s, file, sym);
}
}
return s;
}
Symbol *SymbolTable::addLazyObject(StringRef name, InputFile &file) {
Symbol *s;
bool wasInserted;
std::tie(s, wasInserted) = insert(name, &file);
if (wasInserted) {
replaceSymbol<LazyObject>(s, file, name);
} else if (isa<Undefined>(s)) {
extract(file, name);
} else if (auto *dysym = dyn_cast<DylibSymbol>(s)) {
if (dysym->isWeakDef()) {
if (dysym->getRefState() != RefState::Unreferenced)
extract(file, name);
else
replaceSymbol<LazyObject>(s, file, name);
}
}
return s;
}
Defined *SymbolTable::addSynthetic(StringRef name, InputSection *isec,
uint64_t value, bool isPrivateExtern,
bool includeInSymtab,
bool referencedDynamically) {
assert(!isec || !isec->getFile()); // See makeSyntheticInputSection().
Defined *s =
addDefined(name, /*file=*/nullptr, isec, value, /*size=*/0,
/*isWeakDef=*/false, isPrivateExtern, /*isThumb=*/false,
referencedDynamically, /*noDeadStrip=*/false,
/*isWeakDefCanBeHidden=*/false);
s->includeInSymtab = includeInSymtab;
return s;
}
enum class Boundary {
Start,
End,
};
static Defined *createBoundarySymbol(const Undefined &sym) {
return symtab->addSynthetic(
sym.getName(), /*isec=*/nullptr, /*value=*/-1, /*isPrivateExtern=*/true,
/*includeInSymtab=*/false, /*referencedDynamically=*/false);
}
static void handleSectionBoundarySymbol(const Undefined &sym, StringRef segSect,
Boundary which) {
StringRef segName, sectName;
std::tie(segName, sectName) = segSect.split('$');
// Attach the symbol to any InputSection that will end up in the right
// OutputSection -- it doesn't matter which one we pick.
// Don't bother looking through inputSections for a matching
// ConcatInputSection -- we need to create ConcatInputSection for
// non-existing sections anyways, and that codepath works even if we should
// already have a ConcatInputSection with the right name.
OutputSection *osec = nullptr;
// This looks for __TEXT,__cstring etc.
for (SyntheticSection *ssec : syntheticSections)
if (ssec->segname == segName && ssec->name == sectName) {
osec = ssec->isec->parent;
break;
}
if (!osec) {
ConcatInputSection *isec = makeSyntheticInputSection(segName, sectName);
// This runs after markLive() and is only called for Undefineds that are
// live. Marking the isec live ensures an OutputSection is created that the
// start/end symbol can refer to.
assert(sym.isLive());
isec->live = true;
// This runs after gatherInputSections(), so need to explicitly set parent
// and add to inputSections.
osec = isec->parent = ConcatOutputSection::getOrCreateForInput(isec);
inputSections.push_back(isec);
}
if (which == Boundary::Start)
osec->sectionStartSymbols.push_back(createBoundarySymbol(sym));
else
osec->sectionEndSymbols.push_back(createBoundarySymbol(sym));
}
static void handleSegmentBoundarySymbol(const Undefined &sym, StringRef segName,
Boundary which) {
OutputSegment *seg = getOrCreateOutputSegment(segName);
if (which == Boundary::Start)
seg->segmentStartSymbols.push_back(createBoundarySymbol(sym));
else
seg->segmentEndSymbols.push_back(createBoundarySymbol(sym));
}
// Try to find a definition for an undefined symbol.
// Returns true if a definition was found and no diagnostics are needed.
static bool recoverFromUndefinedSymbol(const Undefined &sym) {
// Handle start/end symbols.
StringRef name = sym.getName();
if (name.consume_front("section$start$")) {
handleSectionBoundarySymbol(sym, name, Boundary::Start);
return true;
}
if (name.consume_front("section$end$")) {
handleSectionBoundarySymbol(sym, name, Boundary::End);
return true;
}
if (name.consume_front("segment$start$")) {
handleSegmentBoundarySymbol(sym, name, Boundary::Start);
return true;
}
if (name.consume_front("segment$end$")) {
handleSegmentBoundarySymbol(sym, name, Boundary::End);
return true;
}
// Leave dtrace symbols, since we will handle them when we do the relocation
if (name.startswith("___dtrace_"))
return true;
// Handle -U.
if (config->explicitDynamicLookups.count(sym.getName())) {
symtab->addDynamicLookup(sym.getName());
return true;
}
// Handle -undefined.
if (config->undefinedSymbolTreatment ==
UndefinedSymbolTreatment::dynamic_lookup ||
config->undefinedSymbolTreatment == UndefinedSymbolTreatment::suppress) {
symtab->addDynamicLookup(sym.getName());
return true;
}
// We do not return true here, as we still need to print diagnostics.
if (config->undefinedSymbolTreatment == UndefinedSymbolTreatment::warning)
symtab->addDynamicLookup(sym.getName());
return false;
}
namespace {
struct UndefinedDiag {
struct SectionAndOffset {
const InputSection *isec;
uint64_t offset;
};
std::vector<SectionAndOffset> codeReferences;
std::vector<std::string> otherReferences;
};
MapVector<const Undefined *, UndefinedDiag> undefs;
}
void macho::reportPendingUndefinedSymbols() {
for (const auto &undef : undefs) {
const UndefinedDiag &locations = undef.second;
std::string message = "undefined symbol";
if (config->archMultiple)
message += (" for arch " + getArchitectureName(config->arch())).str();
message += ": " + toString(*undef.first);
const size_t maxUndefinedReferences = 3;
size_t i = 0;
for (const std::string &loc : locations.otherReferences) {
if (i >= maxUndefinedReferences)
break;
message += "\n>>> referenced by " + loc;
++i;
}
for (const UndefinedDiag::SectionAndOffset &loc :
locations.codeReferences) {
if (i >= maxUndefinedReferences)
break;
message += "\n>>> referenced by ";
std::string src = loc.isec->getSourceLocation(loc.offset);
if (!src.empty())
message += src + "\n>>> ";
message += loc.isec->getLocation(loc.offset);
++i;
}
size_t totalReferences =
locations.otherReferences.size() + locations.codeReferences.size();
if (totalReferences > i)
message +=
("\n>>> referenced " + Twine(totalReferences - i) + " more times")
.str();
if (config->undefinedSymbolTreatment == UndefinedSymbolTreatment::error)
error(message);
else if (config->undefinedSymbolTreatment ==
UndefinedSymbolTreatment::warning)
warn(message);
else
assert(false &&
"diagnostics make sense for -undefined error|warning only");
}
// This function is called multiple times during execution. Clear the printed
// diagnostics to avoid printing the same things again the next time.
undefs.clear();
}
void macho::treatUndefinedSymbol(const Undefined &sym, StringRef source) {
if (recoverFromUndefinedSymbol(sym))
return;
undefs[&sym].otherReferences.push_back(source.str());
}
void macho::treatUndefinedSymbol(const Undefined &sym, const InputSection *isec,
uint64_t offset) {
if (recoverFromUndefinedSymbol(sym))
return;
undefs[&sym].codeReferences.push_back({isec, offset});
}
std::unique_ptr<SymbolTable> macho::symtab;