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llvm-project/lld/COFF/InputFiles.cpp

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//===- InputFiles.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 "InputFiles.h"
#include "Chunks.h"
#include "Config.h"
#include "DebugTypes.h"
#include "Driver.h"
#include "SymbolTable.h"
#include "Symbols.h"
#include "lld/Common/DWARF.h"
#include "lld/Common/ErrorHandler.h"
#include "lld/Common/Memory.h"
#include "llvm-c/lto.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Triple.h"
#include "llvm/ADT/Twine.h"
#include "llvm/BinaryFormat/COFF.h"
#include "llvm/DebugInfo/CodeView/DebugSubsectionRecord.h"
#include "llvm/DebugInfo/CodeView/SymbolDeserializer.h"
#include "llvm/DebugInfo/CodeView/SymbolRecord.h"
#include "llvm/DebugInfo/CodeView/TypeDeserializer.h"
#include "llvm/DebugInfo/PDB/Native/NativeSession.h"
#include "llvm/DebugInfo/PDB/Native/PDBFile.h"
#include "llvm/LTO/LTO.h"
#include "llvm/Object/Binary.h"
#include "llvm/Object/COFF.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/ErrorOr.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/Path.h"
#include "llvm/Target/TargetOptions.h"
#include <cstring>
#include <system_error>
#include <utility>
using namespace llvm;
using namespace llvm::COFF;
using namespace llvm::codeview;
using namespace llvm::object;
using namespace llvm::support::endian;
using namespace lld;
using namespace lld::coff;
using llvm::Triple;
using llvm::support::ulittle32_t;
// Returns the last element of a path, which is supposed to be a filename.
static StringRef getBasename(StringRef path) {
return sys::path::filename(path, sys::path::Style::windows);
}
// Returns a string in the format of "foo.obj" or "foo.obj(bar.lib)".
std::string lld::toString(const coff::InputFile *file) {
if (!file)
return "<internal>";
if (file->parentName.empty() || file->kind() == coff::InputFile::ImportKind)
return std::string(file->getName());
return (getBasename(file->parentName) + "(" + getBasename(file->getName()) +
")")
.str();
}
std::vector<ObjFile *> ObjFile::instances;
std::map<std::string, PDBInputFile *> PDBInputFile::instances;
std::vector<ImportFile *> ImportFile::instances;
std::vector<BitcodeFile *> BitcodeFile::instances;
/// Checks that Source is compatible with being a weak alias to Target.
/// If Source is Undefined and has no weak alias set, makes it a weak
/// alias to Target.
static void checkAndSetWeakAlias(SymbolTable *symtab, InputFile *f,
Symbol *source, Symbol *target) {
if (auto *u = dyn_cast<Undefined>(source)) {
if (u->weakAlias && u->weakAlias != target) {
// Weak aliases as produced by GCC are named in the form
// .weak.<weaksymbol>.<othersymbol>, where <othersymbol> is the name
// of another symbol emitted near the weak symbol.
// Just use the definition from the first object file that defined
// this weak symbol.
if (config->mingw)
return;
symtab->reportDuplicate(source, f);
}
u->weakAlias = target;
}
}
static bool ignoredSymbolName(StringRef name) {
return name == "@feat.00" || name == "@comp.id";
}
ArchiveFile::ArchiveFile(MemoryBufferRef m) : InputFile(ArchiveKind, m) {}
void ArchiveFile::parse() {
// Parse a MemoryBufferRef as an archive file.
file = CHECK(Archive::create(mb), this);
// Read the symbol table to construct Lazy objects.
for (const Archive::Symbol &sym : file->symbols())
symtab->addLazyArchive(this, sym);
}
// Returns a buffer pointing to a member file containing a given symbol.
void ArchiveFile::addMember(const Archive::Symbol &sym) {
const Archive::Child &c =
CHECK(sym.getMember(),
"could not get the member for symbol " + toCOFFString(sym));
// Return an empty buffer if we have already returned the same buffer.
if (!seen.insert(c.getChildOffset()).second)
return;
driver->enqueueArchiveMember(c, sym, getName());
}
std::vector<MemoryBufferRef> lld::coff::getArchiveMembers(Archive *file) {
std::vector<MemoryBufferRef> v;
Error err = Error::success();
for (const Archive::Child &c : file->children(err)) {
MemoryBufferRef mbref =
CHECK(c.getMemoryBufferRef(),
file->getFileName() +
": could not get the buffer for a child of the archive");
v.push_back(mbref);
}
if (err)
fatal(file->getFileName() +
": Archive::children failed: " + toString(std::move(err)));
return v;
}
void LazyObjFile::fetch() {
if (mb.getBuffer().empty())
return;
InputFile *file;
if (isBitcode(mb))
file = make<BitcodeFile>(mb, "", 0, std::move(symbols));
else
file = make<ObjFile>(mb, std::move(symbols));
mb = {};
symtab->addFile(file);
}
void LazyObjFile::parse() {
if (isBitcode(this->mb)) {
// Bitcode file.
std::unique_ptr<lto::InputFile> obj =
CHECK(lto::InputFile::create(this->mb), this);
for (const lto::InputFile::Symbol &sym : obj->symbols()) {
if (!sym.isUndefined())
symtab->addLazyObject(this, sym.getName());
}
return;
}
// Native object file.
std::unique_ptr<Binary> coffObjPtr = CHECK(createBinary(mb), this);
COFFObjectFile *coffObj = cast<COFFObjectFile>(coffObjPtr.get());
uint32_t numSymbols = coffObj->getNumberOfSymbols();
for (uint32_t i = 0; i < numSymbols; ++i) {
COFFSymbolRef coffSym = check(coffObj->getSymbol(i));
if (coffSym.isUndefined() || !coffSym.isExternal() ||
coffSym.isWeakExternal())
continue;
StringRef name = check(coffObj->getSymbolName(coffSym));
if (coffSym.isAbsolute() && ignoredSymbolName(name))
continue;
symtab->addLazyObject(this, name);
i += coffSym.getNumberOfAuxSymbols();
}
}
void ObjFile::parse() {
// Parse a memory buffer as a COFF file.
std::unique_ptr<Binary> bin = CHECK(createBinary(mb), this);
if (auto *obj = dyn_cast<COFFObjectFile>(bin.get())) {
bin.release();
coffObj.reset(obj);
} else {
fatal(toString(this) + " is not a COFF file");
}
// Read section and symbol tables.
initializeChunks();
initializeSymbols();
initializeFlags();
initializeDependencies();
}
const coff_section *ObjFile::getSection(uint32_t i) {
auto sec = coffObj->getSection(i);
if (!sec)
fatal("getSection failed: #" + Twine(i) + ": " + toString(sec.takeError()));
return *sec;
}
// We set SectionChunk pointers in the SparseChunks vector to this value
// temporarily to mark comdat sections as having an unknown resolution. As we
// walk the object file's symbol table, once we visit either a leader symbol or
// an associative section definition together with the parent comdat's leader,
// we set the pointer to either nullptr (to mark the section as discarded) or a
// valid SectionChunk for that section.
static SectionChunk *const pendingComdat = reinterpret_cast<SectionChunk *>(1);
void ObjFile::initializeChunks() {
uint32_t numSections = coffObj->getNumberOfSections();
sparseChunks.resize(numSections + 1);
for (uint32_t i = 1; i < numSections + 1; ++i) {
const coff_section *sec = getSection(i);
if (sec->Characteristics & IMAGE_SCN_LNK_COMDAT)
sparseChunks[i] = pendingComdat;
else
sparseChunks[i] = readSection(i, nullptr, "");
}
}
SectionChunk *ObjFile::readSection(uint32_t sectionNumber,
const coff_aux_section_definition *def,
StringRef leaderName) {
const coff_section *sec = getSection(sectionNumber);
StringRef name;
if (Expected<StringRef> e = coffObj->getSectionName(sec))
name = *e;
else
fatal("getSectionName failed: #" + Twine(sectionNumber) + ": " +
toString(e.takeError()));
if (name == ".drectve") {
ArrayRef<uint8_t> data;
cantFail(coffObj->getSectionContents(sec, data));
directives = StringRef((const char *)data.data(), data.size());
return nullptr;
}
if (name == ".llvm_addrsig") {
addrsigSec = sec;
return nullptr;
}
if (name == ".llvm.call-graph-profile") {
callgraphSec = sec;
return nullptr;
}
// Object files may have DWARF debug info or MS CodeView debug info
// (or both).
//
// DWARF sections don't need any special handling from the perspective
// of the linker; they are just a data section containing relocations.
// We can just link them to complete debug info.
//
// CodeView needs linker support. We need to interpret debug info,
// and then write it to a separate .pdb file.
// Ignore DWARF debug info unless /debug is given.
if (!config->debug && name.startswith(".debug_"))
return nullptr;
if (sec->Characteristics & llvm::COFF::IMAGE_SCN_LNK_REMOVE)
return nullptr;
auto *c = make<SectionChunk>(this, sec);
if (def)
c->checksum = def->CheckSum;
// CodeView sections are stored to a different vector because they are not
// linked in the regular manner.
if (c->isCodeView())
debugChunks.push_back(c);
else if (name == ".gfids$y")
guardFidChunks.push_back(c);
else if (name == ".giats$y")
guardIATChunks.push_back(c);
else if (name == ".gljmp$y")
guardLJmpChunks.push_back(c);
else if (name == ".gehcont$y")
guardEHContChunks.push_back(c);
else if (name == ".sxdata")
sxDataChunks.push_back(c);
else if (config->tailMerge && sec->NumberOfRelocations == 0 &&
name == ".rdata" && leaderName.startswith("??_C@"))
// COFF sections that look like string literal sections (i.e. no
// relocations, in .rdata, leader symbol name matches the MSVC name mangling
// for string literals) are subject to string tail merging.
MergeChunk::addSection(c);
else if (name == ".rsrc" || name.startswith(".rsrc$"))
resourceChunks.push_back(c);
else
chunks.push_back(c);
return c;
}
void ObjFile::includeResourceChunks() {
chunks.insert(chunks.end(), resourceChunks.begin(), resourceChunks.end());
}
void ObjFile::readAssociativeDefinition(
COFFSymbolRef sym, const coff_aux_section_definition *def) {
readAssociativeDefinition(sym, def, def->getNumber(sym.isBigObj()));
}
void ObjFile::readAssociativeDefinition(COFFSymbolRef sym,
const coff_aux_section_definition *def,
uint32_t parentIndex) {
SectionChunk *parent = sparseChunks[parentIndex];
int32_t sectionNumber = sym.getSectionNumber();
auto diag = [&]() {
StringRef name = check(coffObj->getSymbolName(sym));
StringRef parentName;
const coff_section *parentSec = getSection(parentIndex);
if (Expected<StringRef> e = coffObj->getSectionName(parentSec))
parentName = *e;
error(toString(this) + ": associative comdat " + name + " (sec " +
Twine(sectionNumber) + ") has invalid reference to section " +
parentName + " (sec " + Twine(parentIndex) + ")");
};
if (parent == pendingComdat) {
// This can happen if an associative comdat refers to another associative
// comdat that appears after it (invalid per COFF spec) or to a section
// without any symbols.
diag();
return;
}
// Check whether the parent is prevailing. If it is, so are we, and we read
// the section; otherwise mark it as discarded.
if (parent) {
SectionChunk *c = readSection(sectionNumber, def, "");
sparseChunks[sectionNumber] = c;
if (c) {
c->selection = IMAGE_COMDAT_SELECT_ASSOCIATIVE;
parent->addAssociative(c);
}
} else {
sparseChunks[sectionNumber] = nullptr;
}
}
void ObjFile::recordPrevailingSymbolForMingw(
COFFSymbolRef sym, DenseMap<StringRef, uint32_t> &prevailingSectionMap) {
// For comdat symbols in executable sections, where this is the copy
// of the section chunk we actually include instead of discarding it,
// add the symbol to a map to allow using it for implicitly
// associating .[px]data$<func> sections to it.
// Use the suffix from the .text$<func> instead of the leader symbol
// name, for cases where the names differ (i386 mangling/decorations,
// cases where the leader is a weak symbol named .weak.func.default*).
int32_t sectionNumber = sym.getSectionNumber();
SectionChunk *sc = sparseChunks[sectionNumber];
if (sc && sc->getOutputCharacteristics() & IMAGE_SCN_MEM_EXECUTE) {
StringRef name = sc->getSectionName().split('$').second;
prevailingSectionMap[name] = sectionNumber;
}
}
void ObjFile::maybeAssociateSEHForMingw(
COFFSymbolRef sym, const coff_aux_section_definition *def,
const DenseMap<StringRef, uint32_t> &prevailingSectionMap) {
StringRef name = check(coffObj->getSymbolName(sym));
if (name.consume_front(".pdata$") || name.consume_front(".xdata$") ||
name.consume_front(".eh_frame$")) {
// For MinGW, treat .[px]data$<func> and .eh_frame$<func> as implicitly
// associative to the symbol <func>.
auto parentSym = prevailingSectionMap.find(name);
if (parentSym != prevailingSectionMap.end())
readAssociativeDefinition(sym, def, parentSym->second);
}
}
Symbol *ObjFile::createRegular(COFFSymbolRef sym) {
SectionChunk *sc = sparseChunks[sym.getSectionNumber()];
if (sym.isExternal()) {
StringRef name = check(coffObj->getSymbolName(sym));
if (sc)
return symtab->addRegular(this, name, sym.getGeneric(), sc,
sym.getValue());
// For MinGW symbols named .weak.* that point to a discarded section,
// don't create an Undefined symbol. If nothing ever refers to the symbol,
// everything should be fine. If something actually refers to the symbol
// (e.g. the undefined weak alias), linking will fail due to undefined
// references at the end.
if (config->mingw && name.startswith(".weak."))
return nullptr;
return symtab->addUndefined(name, this, false);
}
if (sc)
return make<DefinedRegular>(this, /*Name*/ "", /*IsCOMDAT*/ false,
/*IsExternal*/ false, sym.getGeneric(), sc);
return nullptr;
}
void ObjFile::initializeSymbols() {
uint32_t numSymbols = coffObj->getNumberOfSymbols();
symbols.resize(numSymbols);
SmallVector<std::pair<Symbol *, uint32_t>, 8> weakAliases;
std::vector<uint32_t> pendingIndexes;
pendingIndexes.reserve(numSymbols);
DenseMap<StringRef, uint32_t> prevailingSectionMap;
std::vector<const coff_aux_section_definition *> comdatDefs(
coffObj->getNumberOfSections() + 1);
for (uint32_t i = 0; i < numSymbols; ++i) {
COFFSymbolRef coffSym = check(coffObj->getSymbol(i));
bool prevailingComdat;
if (coffSym.isUndefined()) {
symbols[i] = createUndefined(coffSym);
} else if (coffSym.isWeakExternal()) {
symbols[i] = createUndefined(coffSym);
uint32_t tagIndex = coffSym.getAux<coff_aux_weak_external>()->TagIndex;
weakAliases.emplace_back(symbols[i], tagIndex);
} else if (Optional<Symbol *> optSym =
createDefined(coffSym, comdatDefs, prevailingComdat)) {
symbols[i] = *optSym;
if (config->mingw && prevailingComdat)
recordPrevailingSymbolForMingw(coffSym, prevailingSectionMap);
} else {
// createDefined() returns None if a symbol belongs to a section that
// was pending at the point when the symbol was read. This can happen in
// two cases:
// 1) section definition symbol for a comdat leader;
// 2) symbol belongs to a comdat section associated with another section.
// In both of these cases, we can expect the section to be resolved by
// the time we finish visiting the remaining symbols in the symbol
// table. So we postpone the handling of this symbol until that time.
pendingIndexes.push_back(i);
}
i += coffSym.getNumberOfAuxSymbols();
}
for (uint32_t i : pendingIndexes) {
COFFSymbolRef sym = check(coffObj->getSymbol(i));
if (const coff_aux_section_definition *def = sym.getSectionDefinition()) {
if (def->Selection == IMAGE_COMDAT_SELECT_ASSOCIATIVE)
readAssociativeDefinition(sym, def);
else if (config->mingw)
maybeAssociateSEHForMingw(sym, def, prevailingSectionMap);
}
if (sparseChunks[sym.getSectionNumber()] == pendingComdat) {
StringRef name = check(coffObj->getSymbolName(sym));
log("comdat section " + name +
" without leader and unassociated, discarding");
continue;
}
symbols[i] = createRegular(sym);
}
for (auto &kv : weakAliases) {
Symbol *sym = kv.first;
uint32_t idx = kv.second;
checkAndSetWeakAlias(symtab, this, sym, symbols[idx]);
}
// Free the memory used by sparseChunks now that symbol loading is finished.
decltype(sparseChunks)().swap(sparseChunks);
}
Symbol *ObjFile::createUndefined(COFFSymbolRef sym) {
StringRef name = check(coffObj->getSymbolName(sym));
return symtab->addUndefined(name, this, sym.isWeakExternal());
}
static const coff_aux_section_definition *findSectionDef(COFFObjectFile *obj,
int32_t section) {
uint32_t numSymbols = obj->getNumberOfSymbols();
for (uint32_t i = 0; i < numSymbols; ++i) {
COFFSymbolRef sym = check(obj->getSymbol(i));
if (sym.getSectionNumber() != section)
continue;
if (const coff_aux_section_definition *def = sym.getSectionDefinition())
return def;
}
return nullptr;
}
void ObjFile::handleComdatSelection(
COFFSymbolRef sym, COMDATType &selection, bool &prevailing,
DefinedRegular *leader,
const llvm::object::coff_aux_section_definition *def) {
if (prevailing)
return;
// There's already an existing comdat for this symbol: `Leader`.
// Use the comdats's selection field to determine if the new
// symbol in `Sym` should be discarded, produce a duplicate symbol
// error, etc.
SectionChunk *leaderChunk = leader->getChunk();
COMDATType leaderSelection = leaderChunk->selection;
assert(leader->data && "Comdat leader without SectionChunk?");
if (isa<BitcodeFile>(leader->file)) {
// If the leader is only a LTO symbol, we don't know e.g. its final size
// yet, so we can't do the full strict comdat selection checking yet.
selection = leaderSelection = IMAGE_COMDAT_SELECT_ANY;
}
if ((selection == IMAGE_COMDAT_SELECT_ANY &&
leaderSelection == IMAGE_COMDAT_SELECT_LARGEST) ||
(selection == IMAGE_COMDAT_SELECT_LARGEST &&
leaderSelection == IMAGE_COMDAT_SELECT_ANY)) {
// cl.exe picks "any" for vftables when building with /GR- and
// "largest" when building with /GR. To be able to link object files
// compiled with each flag, "any" and "largest" are merged as "largest".
leaderSelection = selection = IMAGE_COMDAT_SELECT_LARGEST;
}
// GCCs __declspec(selectany) doesn't actually pick "any" but "same size as".
// Clang on the other hand picks "any". To be able to link two object files
// with a __declspec(selectany) declaration, one compiled with gcc and the
// other with clang, we merge them as proper "same size as"
if (config->mingw && ((selection == IMAGE_COMDAT_SELECT_ANY &&
leaderSelection == IMAGE_COMDAT_SELECT_SAME_SIZE) ||
(selection == IMAGE_COMDAT_SELECT_SAME_SIZE &&
leaderSelection == IMAGE_COMDAT_SELECT_ANY))) {
leaderSelection = selection = IMAGE_COMDAT_SELECT_SAME_SIZE;
}
// Other than that, comdat selections must match. This is a bit more
// strict than link.exe which allows merging "any" and "largest" if "any"
// is the first symbol the linker sees, and it allows merging "largest"
// with everything (!) if "largest" is the first symbol the linker sees.
// Making this symmetric independent of which selection is seen first
// seems better though.
// (This behavior matches ModuleLinker::getComdatResult().)
if (selection != leaderSelection) {
log(("conflicting comdat type for " + toString(*leader) + ": " +
Twine((int)leaderSelection) + " in " + toString(leader->getFile()) +
" and " + Twine((int)selection) + " in " + toString(this))
.str());
symtab->reportDuplicate(leader, this);
return;
}
switch (selection) {
case IMAGE_COMDAT_SELECT_NODUPLICATES:
symtab->reportDuplicate(leader, this);
break;
case IMAGE_COMDAT_SELECT_ANY:
// Nothing to do.
break;
case IMAGE_COMDAT_SELECT_SAME_SIZE:
if (leaderChunk->getSize() != getSection(sym)->SizeOfRawData) {
if (!config->mingw) {
symtab->reportDuplicate(leader, this);
} else {
const coff_aux_section_definition *leaderDef = nullptr;
if (leaderChunk->file)
leaderDef = findSectionDef(leaderChunk->file->getCOFFObj(),
leaderChunk->getSectionNumber());
if (!leaderDef || leaderDef->Length != def->Length)
symtab->reportDuplicate(leader, this);
}
}
break;
case IMAGE_COMDAT_SELECT_EXACT_MATCH: {
SectionChunk newChunk(this, getSection(sym));
// link.exe only compares section contents here and doesn't complain
// if the two comdat sections have e.g. different alignment.
// Match that.
if (leaderChunk->getContents() != newChunk.getContents())
symtab->reportDuplicate(leader, this, &newChunk, sym.getValue());
break;
}
case IMAGE_COMDAT_SELECT_ASSOCIATIVE:
// createDefined() is never called for IMAGE_COMDAT_SELECT_ASSOCIATIVE.
// (This means lld-link doesn't produce duplicate symbol errors for
// associative comdats while link.exe does, but associate comdats
// are never extern in practice.)
llvm_unreachable("createDefined not called for associative comdats");
case IMAGE_COMDAT_SELECT_LARGEST:
if (leaderChunk->getSize() < getSection(sym)->SizeOfRawData) {
// Replace the existing comdat symbol with the new one.
StringRef name = check(coffObj->getSymbolName(sym));
// FIXME: This is incorrect: With /opt:noref, the previous sections
// make it into the final executable as well. Correct handling would
// be to undo reading of the whole old section that's being replaced,
// or doing one pass that determines what the final largest comdat
// is for all IMAGE_COMDAT_SELECT_LARGEST comdats and then reading
// only the largest one.
replaceSymbol<DefinedRegular>(leader, this, name, /*IsCOMDAT*/ true,
/*IsExternal*/ true, sym.getGeneric(),
nullptr);
prevailing = true;
}
break;
case IMAGE_COMDAT_SELECT_NEWEST:
llvm_unreachable("should have been rejected earlier");
}
}
Optional<Symbol *> ObjFile::createDefined(
COFFSymbolRef sym,
std::vector<const coff_aux_section_definition *> &comdatDefs,
bool &prevailing) {
prevailing = false;
auto getName = [&]() { return check(coffObj->getSymbolName(sym)); };
if (sym.isCommon()) {
auto *c = make<CommonChunk>(sym);
chunks.push_back(c);
return symtab->addCommon(this, getName(), sym.getValue(), sym.getGeneric(),
c);
}
if (sym.isAbsolute()) {
StringRef name = getName();
if (name == "@feat.00")
feat00Flags = sym.getValue();
// Skip special symbols.
if (ignoredSymbolName(name))
return nullptr;
if (sym.isExternal())
return symtab->addAbsolute(name, sym);
return make<DefinedAbsolute>(name, sym);
}
int32_t sectionNumber = sym.getSectionNumber();
if (sectionNumber == llvm::COFF::IMAGE_SYM_DEBUG)
return nullptr;
if (llvm::COFF::isReservedSectionNumber(sectionNumber))
fatal(toString(this) + ": " + getName() +
" should not refer to special section " + Twine(sectionNumber));
if ((uint32_t)sectionNumber >= sparseChunks.size())
fatal(toString(this) + ": " + getName() +
" should not refer to non-existent section " + Twine(sectionNumber));
// Comdat handling.
// A comdat symbol consists of two symbol table entries.
// The first symbol entry has the name of the section (e.g. .text), fixed
// values for the other fields, and one auxiliary record.
// The second symbol entry has the name of the comdat symbol, called the
// "comdat leader".
// When this function is called for the first symbol entry of a comdat,
// it sets comdatDefs and returns None, and when it's called for the second
// symbol entry it reads comdatDefs and then sets it back to nullptr.
// Handle comdat leader.
if (const coff_aux_section_definition *def = comdatDefs[sectionNumber]) {
comdatDefs[sectionNumber] = nullptr;
DefinedRegular *leader;
if (sym.isExternal()) {
std::tie(leader, prevailing) =
symtab->addComdat(this, getName(), sym.getGeneric());
} else {
leader = make<DefinedRegular>(this, /*Name*/ "", /*IsCOMDAT*/ false,
/*IsExternal*/ false, sym.getGeneric());
prevailing = true;
}
if (def->Selection < (int)IMAGE_COMDAT_SELECT_NODUPLICATES ||
// Intentionally ends at IMAGE_COMDAT_SELECT_LARGEST: link.exe
// doesn't understand IMAGE_COMDAT_SELECT_NEWEST either.
def->Selection > (int)IMAGE_COMDAT_SELECT_LARGEST) {
fatal("unknown comdat type " + std::to_string((int)def->Selection) +
" for " + getName() + " in " + toString(this));
}
COMDATType selection = (COMDATType)def->Selection;
if (leader->isCOMDAT)
handleComdatSelection(sym, selection, prevailing, leader, def);
if (prevailing) {
SectionChunk *c = readSection(sectionNumber, def, getName());
sparseChunks[sectionNumber] = c;
c->sym = cast<DefinedRegular>(leader);
c->selection = selection;
cast<DefinedRegular>(leader)->data = &c->repl;
} else {
sparseChunks[sectionNumber] = nullptr;
}
return leader;
}
// Prepare to handle the comdat leader symbol by setting the section's
// ComdatDefs pointer if we encounter a non-associative comdat.
if (sparseChunks[sectionNumber] == pendingComdat) {
if (const coff_aux_section_definition *def = sym.getSectionDefinition()) {
if (def->Selection != IMAGE_COMDAT_SELECT_ASSOCIATIVE)
comdatDefs[sectionNumber] = def;
}
return None;
}
return createRegular(sym);
}
MachineTypes ObjFile::getMachineType() {
if (coffObj)
return static_cast<MachineTypes>(coffObj->getMachine());
return IMAGE_FILE_MACHINE_UNKNOWN;
}
ArrayRef<uint8_t> ObjFile::getDebugSection(StringRef secName) {
if (SectionChunk *sec = SectionChunk::findByName(debugChunks, secName))
return sec->consumeDebugMagic();
return {};
}
// OBJ files systematically store critical information in a .debug$S stream,
// even if the TU was compiled with no debug info. At least two records are
// always there. S_OBJNAME stores a 32-bit signature, which is loaded into the
// PCHSignature member. S_COMPILE3 stores compile-time cmd-line flags. This is
// currently used to initialize the hotPatchable member.
void ObjFile::initializeFlags() {
ArrayRef<uint8_t> data = getDebugSection(".debug$S");
if (data.empty())
return;
DebugSubsectionArray subsections;
BinaryStreamReader reader(data, support::little);
ExitOnError exitOnErr;
exitOnErr(reader.readArray(subsections, data.size()));
for (const DebugSubsectionRecord &ss : subsections) {
if (ss.kind() != DebugSubsectionKind::Symbols)
continue;
unsigned offset = 0;
// Only parse the first two records. We are only looking for S_OBJNAME
// and S_COMPILE3, and they usually appear at the beginning of the
// stream.
for (unsigned i = 0; i < 2; ++i) {
Expected<CVSymbol> sym = readSymbolFromStream(ss.getRecordData(), offset);
if (!sym) {
consumeError(sym.takeError());
return;
}
if (sym->kind() == SymbolKind::S_COMPILE3) {
auto cs =
cantFail(SymbolDeserializer::deserializeAs<Compile3Sym>(sym.get()));
hotPatchable =
(cs.Flags & CompileSym3Flags::HotPatch) != CompileSym3Flags::None;
}
if (sym->kind() == SymbolKind::S_OBJNAME) {
auto objName = cantFail(SymbolDeserializer::deserializeAs<ObjNameSym>(
sym.get()));
pchSignature = objName.Signature;
}
offset += sym->length();
}
}
}
// Depending on the compilation flags, OBJs can refer to external files,
// necessary to merge this OBJ into the final PDB. We currently support two
// types of external files: Precomp/PCH OBJs, when compiling with /Yc and /Yu.
// And PDB type servers, when compiling with /Zi. This function extracts these
// dependencies and makes them available as a TpiSource interface (see
// DebugTypes.h). Both cases only happen with cl.exe: clang-cl produces regular
// output even with /Yc and /Yu and with /Zi.
void ObjFile::initializeDependencies() {
if (!config->debug)
return;
bool isPCH = false;
ArrayRef<uint8_t> data = getDebugSection(".debug$P");
if (!data.empty())
isPCH = true;
else
data = getDebugSection(".debug$T");
// Don't make a TpiSource for objects with no debug info. If the object has
// symbols but no types, make a plain, empty TpiSource anyway, because it
// simplifies adding the symbols later.
if (data.empty()) {
if (!debugChunks.empty())
debugTypesObj = makeTpiSource(this);
return;
}
// Get the first type record. It will indicate if this object uses a type
// server (/Zi) or a PCH file (/Yu).
CVTypeArray types;
BinaryStreamReader reader(data, support::little);
cantFail(reader.readArray(types, reader.getLength()));
CVTypeArray::Iterator firstType = types.begin();
if (firstType == types.end())
return;
// Remember the .debug$T or .debug$P section.
debugTypes = data;
// This object file is a PCH file that others will depend on.
if (isPCH) {
debugTypesObj = makePrecompSource(this);
return;
}
// This object file was compiled with /Zi. Enqueue the PDB dependency.
if (firstType->kind() == LF_TYPESERVER2) {
TypeServer2Record ts = cantFail(
TypeDeserializer::deserializeAs<TypeServer2Record>(firstType->data()));
debugTypesObj = makeUseTypeServerSource(this, ts);
PDBInputFile::enqueue(ts.getName(), this);
return;
}
// This object was compiled with /Yu. It uses types from another object file
// with a matching signature.
if (firstType->kind() == LF_PRECOMP) {
PrecompRecord precomp = cantFail(
TypeDeserializer::deserializeAs<PrecompRecord>(firstType->data()));
debugTypesObj = makeUsePrecompSource(this, precomp);
// Drop the LF_PRECOMP record from the input stream.
debugTypes = debugTypes.drop_front(firstType->RecordData.size());
return;
}
// This is a plain old object file.
debugTypesObj = makeTpiSource(this);
}
// Make a PDB path assuming the PDB is in the same folder as the OBJ
static std::string getPdbBaseName(ObjFile *file, StringRef tSPath) {
StringRef localPath =
!file->parentName.empty() ? file->parentName : file->getName();
SmallString<128> path = sys::path::parent_path(localPath);
// Currently, type server PDBs are only created by MSVC cl, which only runs
// on Windows, so we can assume type server paths are Windows style.
sys::path::append(path,
sys::path::filename(tSPath, sys::path::Style::windows));
return std::string(path.str());
}
// The casing of the PDB path stamped in the OBJ can differ from the actual path
// on disk. With this, we ensure to always use lowercase as a key for the
// PDBInputFile::instances map, at least on Windows.
static std::string normalizePdbPath(StringRef path) {
#if defined(_WIN32)
return path.lower();
#else // LINUX
return std::string(path);
#endif
}
// If existing, return the actual PDB path on disk.
static Optional<std::string> findPdbPath(StringRef pdbPath,
ObjFile *dependentFile) {
// Ensure the file exists before anything else. In some cases, if the path
// points to a removable device, Driver::enqueuePath() would fail with an
// error (EAGAIN, "resource unavailable try again") which we want to skip
// silently.
if (llvm::sys::fs::exists(pdbPath))
return normalizePdbPath(pdbPath);
std::string ret = getPdbBaseName(dependentFile, pdbPath);
if (llvm::sys::fs::exists(ret))
return normalizePdbPath(ret);
return None;
}
PDBInputFile::PDBInputFile(MemoryBufferRef m) : InputFile(PDBKind, m) {}
PDBInputFile::~PDBInputFile() = default;
PDBInputFile *PDBInputFile::findFromRecordPath(StringRef path,
ObjFile *fromFile) {
auto p = findPdbPath(path.str(), fromFile);
if (!p)
return nullptr;
auto it = PDBInputFile::instances.find(*p);
if (it != PDBInputFile::instances.end())
return it->second;
return nullptr;
}
void PDBInputFile::enqueue(StringRef path, ObjFile *fromFile) {
auto p = findPdbPath(path.str(), fromFile);
if (!p)
return;
auto it = PDBInputFile::instances.emplace(*p, nullptr);
if (!it.second)
return; // already scheduled for load
driver->enqueuePDB(*p);
}
void PDBInputFile::parse() {
PDBInputFile::instances[mb.getBufferIdentifier().str()] = this;
std::unique_ptr<pdb::IPDBSession> thisSession;
loadErr.emplace(pdb::NativeSession::createFromPdb(
MemoryBuffer::getMemBuffer(mb, false), thisSession));
if (*loadErr)
return; // fail silently at this point - the error will be handled later,
// when merging the debug type stream
session.reset(static_cast<pdb::NativeSession *>(thisSession.release()));
pdb::PDBFile &pdbFile = session->getPDBFile();
auto expectedInfo = pdbFile.getPDBInfoStream();
// All PDB Files should have an Info stream.
if (!expectedInfo) {
loadErr.emplace(expectedInfo.takeError());
return;
}
debugTypesObj = makeTypeServerSource(this);
}
// Used only for DWARF debug info, which is not common (except in MinGW
// environments). This returns an optional pair of file name and line
// number for where the variable was defined.
Optional<std::pair<StringRef, uint32_t>>
ObjFile::getVariableLocation(StringRef var) {
if (!dwarf) {
dwarf = make<DWARFCache>(DWARFContext::create(*getCOFFObj()));
if (!dwarf)
return None;
}
if (config->machine == I386)
var.consume_front("_");
Optional<std::pair<std::string, unsigned>> ret = dwarf->getVariableLoc(var);
if (!ret)
return None;
return std::make_pair(saver.save(ret->first), ret->second);
}
// Used only for DWARF debug info, which is not common (except in MinGW
// environments).
Optional<DILineInfo> ObjFile::getDILineInfo(uint32_t offset,
uint32_t sectionIndex) {
if (!dwarf) {
dwarf = make<DWARFCache>(DWARFContext::create(*getCOFFObj()));
if (!dwarf)
return None;
}
return dwarf->getDILineInfo(offset, sectionIndex);
}
static StringRef ltrim1(StringRef s, const char *chars) {
if (!s.empty() && strchr(chars, s[0]))
return s.substr(1);
return s;
}
void ImportFile::parse() {
const char *buf = mb.getBufferStart();
const auto *hdr = reinterpret_cast<const coff_import_header *>(buf);
// Check if the total size is valid.
if (mb.getBufferSize() != sizeof(*hdr) + hdr->SizeOfData)
fatal("broken import library");
// Read names and create an __imp_ symbol.
StringRef name = saver.save(StringRef(buf + sizeof(*hdr)));
StringRef impName = saver.save("__imp_" + name);
const char *nameStart = buf + sizeof(coff_import_header) + name.size() + 1;
dllName = std::string(StringRef(nameStart));
StringRef extName;
switch (hdr->getNameType()) {
case IMPORT_ORDINAL:
extName = "";
break;
case IMPORT_NAME:
extName = name;
break;
case IMPORT_NAME_NOPREFIX:
extName = ltrim1(name, "?@_");
break;
case IMPORT_NAME_UNDECORATE:
extName = ltrim1(name, "?@_");
extName = extName.substr(0, extName.find('@'));
break;
}
this->hdr = hdr;
externalName = extName;
impSym = symtab->addImportData(impName, this);
// If this was a duplicate, we logged an error but may continue;
// in this case, impSym is nullptr.
if (!impSym)
return;
if (hdr->getType() == llvm::COFF::IMPORT_CONST)
static_cast<void>(symtab->addImportData(name, this));
// If type is function, we need to create a thunk which jump to an
// address pointed by the __imp_ symbol. (This allows you to call
// DLL functions just like regular non-DLL functions.)
if (hdr->getType() == llvm::COFF::IMPORT_CODE)
thunkSym = symtab->addImportThunk(
name, cast_or_null<DefinedImportData>(impSym), hdr->Machine);
}
BitcodeFile::BitcodeFile(MemoryBufferRef mb, StringRef archiveName,
uint64_t offsetInArchive)
: BitcodeFile(mb, archiveName, offsetInArchive, {}) {}
BitcodeFile::BitcodeFile(MemoryBufferRef mb, StringRef archiveName,
uint64_t offsetInArchive,
std::vector<Symbol *> &&symbols)
: InputFile(BitcodeKind, mb), symbols(std::move(symbols)) {
std::string path = mb.getBufferIdentifier().str();
if (config->thinLTOIndexOnly)
path = replaceThinLTOSuffix(mb.getBufferIdentifier());
// ThinLTO assumes that all MemoryBufferRefs given to it have a unique
// name. If two archives define two members with the same name, this
// causes a collision which result in only one of the objects being taken
// into consideration at LTO time (which very likely causes undefined
// symbols later in the link stage). So we append file offset to make
// filename unique.
MemoryBufferRef mbref(
mb.getBuffer(),
saver.save(archiveName.empty() ? path
: archiveName + sys::path::filename(path) +
utostr(offsetInArchive)));
obj = check(lto::InputFile::create(mbref));
}
BitcodeFile::~BitcodeFile() = default;
namespace {
// Convenience class for initializing a coff_section with specific flags.
class FakeSection {
public:
FakeSection(int c) { section.Characteristics = c; }
coff_section section;
};
// Convenience class for initializing a SectionChunk with specific flags.
class FakeSectionChunk {
public:
FakeSectionChunk(const coff_section *section) : chunk(nullptr, section) {
// Comdats from LTO files can't be fully treated as regular comdats
// at this point; we don't know what size or contents they are going to
// have, so we can't do proper checking of such aspects of them.
chunk.selection = IMAGE_COMDAT_SELECT_ANY;
}
SectionChunk chunk;
};
FakeSection ltoTextSection(IMAGE_SCN_MEM_EXECUTE);
FakeSection ltoDataSection(IMAGE_SCN_CNT_INITIALIZED_DATA);
FakeSectionChunk ltoTextSectionChunk(&ltoTextSection.section);
FakeSectionChunk ltoDataSectionChunk(&ltoDataSection.section);
} // namespace
void BitcodeFile::parse() {
std::vector<std::pair<Symbol *, bool>> comdat(obj->getComdatTable().size());
for (size_t i = 0; i != obj->getComdatTable().size(); ++i)
// FIXME: lto::InputFile doesn't keep enough data to do correct comdat
// selection handling.
comdat[i] = symtab->addComdat(this, saver.save(obj->getComdatTable()[i]));
for (const lto::InputFile::Symbol &objSym : obj->symbols()) {
StringRef symName = saver.save(objSym.getName());
int comdatIndex = objSym.getComdatIndex();
Symbol *sym;
SectionChunk *fakeSC = nullptr;
if (objSym.isExecutable())
fakeSC = &ltoTextSectionChunk.chunk;
else
fakeSC = &ltoDataSectionChunk.chunk;
if (objSym.isUndefined()) {
sym = symtab->addUndefined(symName, this, false);
} else if (objSym.isCommon()) {
sym = symtab->addCommon(this, symName, objSym.getCommonSize());
} else if (objSym.isWeak() && objSym.isIndirect()) {
// Weak external.
sym = symtab->addUndefined(symName, this, true);
std::string fallback = std::string(objSym.getCOFFWeakExternalFallback());
Symbol *alias = symtab->addUndefined(saver.save(fallback));
checkAndSetWeakAlias(symtab, this, sym, alias);
} else if (comdatIndex != -1) {
if (symName == obj->getComdatTable()[comdatIndex]) {
sym = comdat[comdatIndex].first;
if (cast<DefinedRegular>(sym)->data == nullptr)
cast<DefinedRegular>(sym)->data = &fakeSC->repl;
} else if (comdat[comdatIndex].second) {
sym = symtab->addRegular(this, symName, nullptr, fakeSC);
} else {
sym = symtab->addUndefined(symName, this, false);
}
} else {
sym = symtab->addRegular(this, symName, nullptr, fakeSC);
}
symbols.push_back(sym);
if (objSym.isUsed())
config->gcroot.push_back(sym);
}
directives = obj->getCOFFLinkerOpts();
}
MachineTypes BitcodeFile::getMachineType() {
switch (Triple(obj->getTargetTriple()).getArch()) {
case Triple::x86_64:
return AMD64;
case Triple::x86:
return I386;
case Triple::arm:
return ARMNT;
case Triple::aarch64:
return ARM64;
default:
return IMAGE_FILE_MACHINE_UNKNOWN;
}
}
std::string lld::coff::replaceThinLTOSuffix(StringRef path) {
StringRef suffix = config->thinLTOObjectSuffixReplace.first;
StringRef repl = config->thinLTOObjectSuffixReplace.second;
if (path.consume_back(suffix))
return (path + repl).str();
return std::string(path);
}
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