blob: 289cdb1f6cd086512b069cb47270d46277973b45 [file] [log] [blame]
//===- InputFiles.cpp -----------------------------------------------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "InputFiles.h"
#include "Chunks.h"
#include "Config.h"
#include "Driver.h"
#include "SymbolTable.h"
#include "Symbols.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/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::object;
using namespace llvm::support::endian;
using llvm::Triple;
using llvm::support::ulittle32_t;
namespace lld {
namespace coff {
std::vector<ObjFile *> ObjFile::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)
Symtab->reportDuplicate(Source, F);
U->WeakAlias = Target;
}
}
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->addLazy(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 " + Sym->getName());
// Return an empty buffer if we have already returned the same buffer.
if (!Seen.insert(C.getChildOffset()).second)
return;
Driver->enqueueArchiveMember(C, Sym->getName(), getName());
}
std::vector<MemoryBufferRef> getArchiveMembers(Archive *File) {
std::vector<MemoryBufferRef> V;
Error Err = Error::success();
for (const ErrorOr<Archive::Child> &COrErr : File->children(Err)) {
Archive::Child C =
CHECK(COrErr,
File->getFileName() + ": could not get the child of the archive");
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 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();
}
// 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();
Chunks.reserve(NumSections);
SparseChunks.resize(NumSections + 1);
for (uint32_t I = 1; I < NumSections + 1; ++I) {
const coff_section *Sec;
if (auto EC = COFFObj->getSection(I, Sec))
fatal("getSection failed: #" + Twine(I) + ": " + EC.message());
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;
StringRef Name;
if (auto EC = COFFObj->getSection(SectionNumber, Sec))
fatal("getSection failed: #" + Twine(SectionNumber) + ": " + EC.message());
if (auto EC = COFFObj->getSectionName(Sec, Name))
fatal("getSectionName failed: #" + Twine(SectionNumber) + ": " +
EC.message());
if (Name == ".drectve") {
ArrayRef<uint8_t> Data;
COFFObj->getSectionContents(Sec, Data);
Directives = std::string((const char *)Data.data(), Data.size());
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 a linker support. We need to interpret and 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 (Config->GuardCF != GuardCFLevel::Off && Name == ".gfids$y")
GuardFidChunks.push_back(C);
else if (Config->GuardCF != GuardCFLevel::Off && Name == ".gljmp$y")
GuardLJmpChunks.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
Chunks.push_back(C);
return C;
}
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 ParentSection) {
SectionChunk *Parent = SparseChunks[ParentSection];
// If the parent is pending, it probably means that its section definition
// appears after us in the symbol table. Leave the associated section as
// pending; we will handle it during the second pass in initializeSymbols().
if (Parent == PendingComdat)
return;
// Check whether the parent is prevailing. If it is, so are we, and we read
// the section; otherwise mark it as discarded.
int32_t SectionNumber = Sym.getSectionNumber();
if (Parent) {
SparseChunks[SectionNumber] = readSection(SectionNumber, Def, "");
if (SparseChunks[SectionNumber])
Parent->addAssociative(SparseChunks[SectionNumber]);
} 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$<func> sections to it.
int32_t SectionNumber = Sym.getSectionNumber();
SectionChunk *SC = SparseChunks[SectionNumber];
if (SC && SC->getOutputCharacteristics() & IMAGE_SCN_MEM_EXECUTE) {
StringRef Name;
COFFObj->getSymbolName(Sym, Name);
PrevailingSectionMap[Name] = SectionNumber;
}
}
void ObjFile::maybeAssociateSEHForMingw(
COFFSymbolRef Sym, const coff_aux_section_definition *Def,
const DenseMap<StringRef, uint32_t> &PrevailingSectionMap) {
StringRef Name;
COFFObj->getSymbolName(Sym, Name);
if (Name.consume_front(".pdata$") || Name.consume_front(".xdata$")) {
// For MinGW, treat .[px]data$<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;
COFFObj->getSymbolName(Sym, Name);
if (SC)
return Symtab->addRegular(this, Name, Sym.getGeneric(), SC);
return Symtab->addUndefined(Name, this, false);
}
if (SC)
return make<DefinedRegular>(this, /*Name*/ "", 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 a section whose
// section definition symbol appears later in the symbol table.
// 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 (auto *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;
COFFObj->getSymbolName(Sym, Name);
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]);
}
}
Symbol *ObjFile::createUndefined(COFFSymbolRef Sym) {
StringRef Name;
COFFObj->getSymbolName(Sym, Name);
return Symtab->addUndefined(Name, this, Sym.isWeakExternal());
}
Optional<Symbol *> ObjFile::createDefined(
COFFSymbolRef Sym,
std::vector<const coff_aux_section_definition *> &ComdatDefs,
bool &Prevailing) {
Prevailing = false;
auto GetName = [&]() {
StringRef S;
COFFObj->getSymbolName(Sym, S);
return S;
};
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();
// Skip special symbols.
if (Name == "@comp.id")
return nullptr;
if (Name == "@feat.00") {
Feat00Flags = Sym.getValue();
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));
// Handle comdat leader symbols.
if (const coff_aux_section_definition *Def = ComdatDefs[SectionNumber]) {
ComdatDefs[SectionNumber] = nullptr;
Symbol *Leader;
if (Sym.isExternal()) {
std::tie(Leader, Prevailing) =
Symtab->addComdat(this, GetName(), Sym.getGeneric());
} else {
Leader = make<DefinedRegular>(this, /*Name*/ "", false,
/*IsExternal*/ false, Sym.getGeneric());
Prevailing = true;
}
if (Prevailing) {
SectionChunk *C = readSection(SectionNumber, Def, GetName());
SparseChunks[SectionNumber] = C;
C->Sym = cast<DefinedRegular>(Leader);
cast<DefinedRegular>(Leader)->Data = &C->Repl;
} else {
SparseChunks[SectionNumber] = nullptr;
}
return Leader;
}
// Read associative section definitions and 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 (auto *Def = Sym.getSectionDefinition()) {
if (Def->Selection == IMAGE_COMDAT_SELECT_ASSOCIATIVE)
readAssociativeDefinition(Sym, Def);
else
ComdatDefs[SectionNumber] = Def;
}
}
if (SparseChunks[SectionNumber] == PendingComdat)
return None;
return createRegular(Sym);
}
MachineTypes ObjFile::getMachineType() {
if (COFFObj)
return static_cast<MachineTypes>(COFFObj->getMachine());
return IMAGE_FILE_MACHINE_UNKNOWN;
}
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 char *End = MB.getBufferEnd();
const auto *Hdr = reinterpret_cast<const coff_import_header *>(Buf);
// Check if the total size is valid.
if ((size_t)(End - Buf) != (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 = 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 (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);
}
void BitcodeFile::parse() {
Obj = check(lto::InputFile::create(MemoryBufferRef(
MB.getBuffer(), Saver.save(ParentName + MB.getBufferIdentifier()))));
std::vector<std::pair<Symbol *, bool>> Comdat(Obj->getComdatTable().size());
for (size_t I = 0; I != Obj->getComdatTable().size(); ++I)
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;
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 = 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;
else if (Comdat[ComdatIndex].second)
Sym = Symtab->addRegular(this, SymName);
else
Sym = Symtab->addUndefined(SymName, this, false);
} else {
Sym = Symtab->addRegular(this, SymName);
}
Symbols.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;
}
}
} // namespace coff
} // namespace lld
// 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())
return File->getName();
return (getBasename(File->ParentName) + "(" + getBasename(File->getName()) +
")")
.str();
}