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llvm-project/lld/COFF/SymbolTable.cpp

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//===- 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 "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/Object/WindowsMachineFlag.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);
}
driver->parseDirectives(file);
}
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->data || d->file != sc->file || d->getChunk() != sc ||
d->getValue() > addr ||
(candidate && d->getValue() < candidate->getValue()))
continue;
candidate = d;
}
return candidate;
}
static std::vector<std::string> getSymbolLocations(BitcodeFile *file) {
std::string res("\n>>> referenced by ");
StringRef source = file->obj->getSourceFileName();
if (!source.empty())
res += source.str() + "\n>>> ";
res += toString(file);
return {res};
}
// Given a file and the index of a symbol in that file, returns a description
// of all references to that symbol from that file. If no debug information is
// available, returns just the name of the file, else one string per actual
// reference as described in the debug info.
std::vector<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->getRelocs()) {
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 std::vector<std::string>({"\n>>> referenced by " + toString(file)});
std::vector<std::string> symbolLocations(locations.size());
size_t i = 0;
for (Location loc : locations) {
llvm::raw_string_ostream os(symbolLocations[i++]);
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 symbolLocations;
}
std::vector<std::string> getSymbolLocations(InputFile *file,
uint32_t symIndex) {
if (auto *o = dyn_cast<ObjFile>(file))
return getSymbolLocations(o, symIndex);
if (auto *b = dyn_cast<BitcodeFile>(file))
return getSymbolLocations(b);
llvm_unreachable("unsupported file type passed to getSymbolLocations");
return {};
}
// For an undefined symbol, stores all files referencing it and the index of
// the undefined symbol in each file.
struct UndefinedDiag {
Symbol *sym;
struct File {
InputFile *file;
uint32_t symIndex;
};
std::vector<File> files;
};
static void reportUndefinedSymbol(const UndefinedDiag &undefDiag) {
std::string out;
llvm::raw_string_ostream os(out);
os << "undefined symbol: " << toString(*undefDiag.sym);
const size_t maxUndefReferences = 10;
size_t i = 0, numRefs = 0;
for (const UndefinedDiag::File &ref : undefDiag.files) {
std::vector<std::string> symbolLocations =
getSymbolLocations(ref.file, ref.symIndex);
numRefs += symbolLocations.size();
for (const std::string &s : symbolLocations) {
if (i >= maxUndefReferences)
break;
os << s;
i++;
}
}
if (i < numRefs)
os << "\n>>> referenced " << numRefs - i << " more times";
errorOrWarn(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;
if (undef->getWeakAlias())
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);
}
}
Defined *SymbolTable::impSymbol(StringRef name) {
if (name.startswith("__imp_"))
return nullptr;
return dyn_cast_or_null<Defined>(find(("__imp_" + name).str()));
}
bool SymbolTable::handleMinGWAutomaticImport(Symbol *sym, StringRef name) {
Defined *imp = impSymbol(name);
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->getRelocs().size() == 1 && *sc->symbols().begin() == sym) {
log("Replacing .refptr." + name + " with " + imp->getName());
refptr->getChunk()->live = false;
refptr->replaceKeepingName(imp, impSize);
}
}
return true;
}
/// Helper function for reportUnresolvable and resolveRemainingUndefines.
/// This function emits an "undefined symbol" diagnostic for each symbol in
/// undefs. If localImports is not nullptr, it also emits a "locally
/// defined symbol imported" diagnostic for symbols in localImports.
/// objFiles and bitcodeFiles (if not nullptr) are used to report where
/// undefined symbols are referenced.
static void
reportProblemSymbols(const SmallPtrSetImpl<Symbol *> &undefs,
const DenseMap<Symbol *, Symbol *> *localImports,
const std::vector<ObjFile *> objFiles,
const std::vector<BitcodeFile *> *bitcodeFiles) {
// Return early if there is nothing to report (which should be
// the common case).
if (undefs.empty() && (!localImports || localImports->empty()))
return;
for (Symbol *b : config->gcroot) {
if (undefs.count(b))
errorOrWarn("<root>: undefined symbol: " + toString(*b));
if (localImports)
if (Symbol *imp = localImports->lookup(b))
warn("<root>: locally defined symbol imported: " + toString(*imp) +
" (defined in " + toString(imp->getFile()) + ") [LNK4217]");
}
std::vector<UndefinedDiag> undefDiags;
DenseMap<Symbol *, int> firstDiag;
auto processFile = [&](InputFile *file, ArrayRef<Symbol *> symbols) {
uint32_t symIndex = (uint32_t)-1;
for (Symbol *sym : symbols) {
++symIndex;
if (!sym)
continue;
if (undefs.count(sym)) {
auto it = firstDiag.find(sym);
if (it == firstDiag.end()) {
firstDiag[sym] = undefDiags.size();
undefDiags.push_back({sym, {{file, symIndex}}});
} else {
undefDiags[it->second].files.push_back({file, symIndex});
}
}
if (localImports)
if (Symbol *imp = localImports->lookup(sym))
warn(toString(file) +
": locally defined symbol imported: " + toString(*imp) +
" (defined in " + toString(imp->getFile()) + ") [LNK4217]");
}
};
for (ObjFile *file : objFiles)
processFile(file, file->getSymbols());
if (bitcodeFiles)
for (BitcodeFile *file : *bitcodeFiles)
processFile(file, file->getSymbols());
for (const UndefinedDiag &undefDiag : undefDiags)
reportUndefinedSymbol(undefDiag);
}
void SymbolTable::reportUnresolvable() {
SmallPtrSet<Symbol *, 8> undefs;
for (auto &i : symMap) {
Symbol *sym = i.second;
auto *undef = dyn_cast<Undefined>(sym);
if (!undef)
continue;
if (undef->getWeakAlias())
continue;
StringRef name = undef->getName();
if (name.startswith("__imp_")) {
Symbol *imp = find(name.substr(strlen("__imp_")));
if (imp && isa<Defined>(imp))
continue;
}
if (name.contains("_PchSym_"))
continue;
if (config->mingw && impSymbol(name))
continue;
undefs.insert(sym);
}
reportProblemSymbols(undefs,
/* localImports */ nullptr, ObjFile::instances,
&BitcodeFile::instances);
}
void SymbolTable::resolveRemainingUndefines() {
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);
}
reportProblemSymbols(
undefs, config->warnLocallyDefinedImported ? &localImports : nullptr,
ObjFile::instances, /* bitcode files no longer needed */ nullptr);
}
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<DefinedRegular *, 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 {cast<DefinedRegular>(s), true};
}
auto *existingSymbol = cast<DefinedRegular>(s);
if (!existingSymbol->isCOMDAT)
reportDuplicate(s, f);
return {existingSymbol, 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);
}
// Return all symbols that start with Prefix, possibly ignoring the first
// character of Prefix or the first character symbol.
std::vector<Symbol *> SymbolTable::getSymsWithPrefix(StringRef prefix) {
std::vector<Symbol *> syms;
for (auto pair : symMap) {
StringRef name = pair.first.val();
if (name.startswith(prefix) || name.startswith(prefix.drop_front()) ||
name.drop_front().startswith(prefix) ||
name.drop_front().startswith(prefix.drop_front())) {
syms.push_back(pair.second);
}
}
return syms;
}
Symbol *SymbolTable::findMangle(StringRef name) {
if (Symbol *sym = find(name))
if (!isa<Undefined>(sym))
return sym;
// Efficient fuzzy string lookup is impossible with a hash table, so iterate
// the symbol table once and collect all possibly matching symbols into this
// vector. Then compare each possibly matching symbol with each possible
// mangling.
std::vector<Symbol *> syms = getSymsWithPrefix(name);
auto findByPrefix = [&syms](const Twine &t) -> Symbol * {
std::string prefix = t.str();
for (auto *s : syms)
if (s->getName().startswith(prefix))
return s;
return nullptr;
};
// For non-x86, just look for C++ functions.
if (config->machine != I386)
return findByPrefix("?" + name + "@@Y");
if (!name.startswith("_"))
return nullptr;
// Search for x86 stdcall function.
if (Symbol *s = findByPrefix(name + "@"))
return s;
// Search for x86 fastcall function.
if (Symbol *s = findByPrefix("@" + name.substr(1) + "@"))
return s;
// Search for x86 vectorcall function.
if (Symbol *s = findByPrefix(name.substr(1) + "@@"))
return s;
// Search for x86 C++ non-member function.
return findByPrefix("?" + name.substr(1) + "@@Y");
}
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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