blob: 3622dc2b8c37f6aa5d0c2a4741fe9684ccaa7e43 [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 "Error.h"
#include "InputSection.h"
#include "Symbols.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/Object/IRObjectFile.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
using namespace llvm::ELF;
using namespace llvm::object;
using namespace llvm::sys::fs;
using namespace lld;
using namespace lld::elf;
template <class ELFT>
static ELFFile<ELFT> createELFObj(MemoryBufferRef MB) {
std::error_code EC;
ELFFile<ELFT> F(MB.getBuffer(), EC);
check(EC);
return F;
}
template <class ELFT>
ELFFileBase<ELFT>::ELFFileBase(Kind K, MemoryBufferRef MB)
: InputFile(K, MB), ELFObj(createELFObj<ELFT>(MB)) {}
template <class ELFT>
ELFKind ELFFileBase<ELFT>::getELFKind() {
if (ELFT::TargetEndianness == support::little)
return ELFT::Is64Bits ? ELF64LEKind : ELF32LEKind;
return ELFT::Is64Bits ? ELF64BEKind : ELF32BEKind;
}
template <class ELFT>
typename ELFT::SymRange ELFFileBase<ELFT>::getElfSymbols(bool OnlyGlobals) {
if (!Symtab)
return Elf_Sym_Range(nullptr, nullptr);
Elf_Sym_Range Syms = ELFObj.symbols(Symtab);
uint32_t NumSymbols = std::distance(Syms.begin(), Syms.end());
uint32_t FirstNonLocal = Symtab->sh_info;
if (FirstNonLocal > NumSymbols)
fatal("invalid sh_info in symbol table");
if (OnlyGlobals)
return make_range(Syms.begin() + FirstNonLocal, Syms.end());
return make_range(Syms.begin(), Syms.end());
}
template <class ELFT>
uint32_t ELFFileBase<ELFT>::getSectionIndex(const Elf_Sym &Sym) const {
uint32_t I = Sym.st_shndx;
if (I == ELF::SHN_XINDEX)
return ELFObj.getExtendedSymbolTableIndex(&Sym, Symtab, SymtabSHNDX);
if (I >= ELF::SHN_LORESERVE)
return 0;
return I;
}
template <class ELFT> void ELFFileBase<ELFT>::initStringTable() {
if (!Symtab)
return;
StringTable = check(ELFObj.getStringTableForSymtab(*Symtab));
}
template <class ELFT>
elf::ObjectFile<ELFT>::ObjectFile(MemoryBufferRef M)
: ELFFileBase<ELFT>(Base::ObjectKind, M) {}
template <class ELFT>
ArrayRef<SymbolBody *> elf::ObjectFile<ELFT>::getNonLocalSymbols() {
if (!this->Symtab)
return this->SymbolBodies;
uint32_t FirstNonLocal = this->Symtab->sh_info;
return makeArrayRef(this->SymbolBodies).slice(FirstNonLocal);
}
template <class ELFT>
ArrayRef<SymbolBody *> elf::ObjectFile<ELFT>::getLocalSymbols() {
if (!this->Symtab)
return this->SymbolBodies;
uint32_t FirstNonLocal = this->Symtab->sh_info;
return makeArrayRef(this->SymbolBodies).slice(1, FirstNonLocal - 1);
}
template <class ELFT>
ArrayRef<SymbolBody *> elf::ObjectFile<ELFT>::getSymbols() {
if (!this->Symtab)
return this->SymbolBodies;
return makeArrayRef(this->SymbolBodies).slice(1);
}
template <class ELFT> uint32_t elf::ObjectFile<ELFT>::getMipsGp0() const {
if (MipsReginfo)
return MipsReginfo->Reginfo->ri_gp_value;
return 0;
}
template <class ELFT>
void elf::ObjectFile<ELFT>::parse(DenseSet<StringRef> &ComdatGroups) {
// Read section and symbol tables.
initializeSections(ComdatGroups);
initializeSymbols();
}
// Sections with SHT_GROUP and comdat bits define comdat section groups.
// They are identified and deduplicated by group name. This function
// returns a group name.
template <class ELFT>
StringRef elf::ObjectFile<ELFT>::getShtGroupSignature(const Elf_Shdr &Sec) {
const ELFFile<ELFT> &Obj = this->ELFObj;
uint32_t SymtabdSectionIndex = Sec.sh_link;
const Elf_Shdr *SymtabSec = check(Obj.getSection(SymtabdSectionIndex));
uint32_t SymIndex = Sec.sh_info;
const Elf_Sym *Sym = Obj.getSymbol(SymtabSec, SymIndex);
StringRef StringTable = check(Obj.getStringTableForSymtab(*SymtabSec));
return check(Sym->getName(StringTable));
}
template <class ELFT>
ArrayRef<typename elf::ObjectFile<ELFT>::Elf_Word>
elf::ObjectFile<ELFT>::getShtGroupEntries(const Elf_Shdr &Sec) {
const ELFFile<ELFT> &Obj = this->ELFObj;
ArrayRef<Elf_Word> Entries =
check(Obj.template getSectionContentsAsArray<Elf_Word>(&Sec));
if (Entries.empty() || Entries[0] != GRP_COMDAT)
fatal("unsupported SHT_GROUP format");
return Entries.slice(1);
}
template <class ELFT> static bool shouldMerge(const typename ELFT::Shdr &Sec) {
typedef typename ELFT::uint uintX_t;
uintX_t Flags = Sec.sh_flags;
if (!(Flags & SHF_MERGE))
return false;
if (Flags & SHF_WRITE)
fatal("writable SHF_MERGE sections are not supported");
uintX_t EntSize = Sec.sh_entsize;
if (!EntSize || Sec.sh_size % EntSize)
fatal("SHF_MERGE section size must be a multiple of sh_entsize");
// Don't try to merge if the aligment is larger than the sh_entsize and this
// is not SHF_STRINGS.
//
// Since this is not a SHF_STRINGS, we would need to pad after every entity.
// It would be equivalent for the producer of the .o to just set a larger
// sh_entsize.
if (Flags & SHF_STRINGS)
return true;
if (Sec.sh_addralign > EntSize)
return false;
return true;
}
template <class ELFT>
void elf::ObjectFile<ELFT>::initializeSections(
DenseSet<StringRef> &ComdatGroups) {
uint64_t Size = this->ELFObj.getNumSections();
Sections.resize(Size);
unsigned I = -1;
const ELFFile<ELFT> &Obj = this->ELFObj;
for (const Elf_Shdr &Sec : Obj.sections()) {
++I;
if (Sections[I] == InputSection<ELFT>::Discarded)
continue;
switch (Sec.sh_type) {
case SHT_GROUP:
Sections[I] = InputSection<ELFT>::Discarded;
if (ComdatGroups.insert(getShtGroupSignature(Sec)).second)
continue;
for (uint32_t SecIndex : getShtGroupEntries(Sec)) {
if (SecIndex >= Size)
fatal("invalid section index in group");
Sections[SecIndex] = InputSection<ELFT>::Discarded;
}
break;
case SHT_SYMTAB:
this->Symtab = &Sec;
break;
case SHT_SYMTAB_SHNDX:
this->SymtabSHNDX = check(Obj.getSHNDXTable(Sec));
break;
case SHT_STRTAB:
case SHT_NULL:
break;
case SHT_RELA:
case SHT_REL: {
// This section contains relocation information.
// If -r is given, we do not interpret or apply relocation
// but just copy relocation sections to output.
if (Config->Relocatable) {
Sections[I] = new (Alloc) InputSection<ELFT>(this, &Sec);
break;
}
// Find the relocation target section and associate this
// section with it.
InputSectionBase<ELFT> *Target = getRelocTarget(Sec);
if (!Target)
break;
if (auto *S = dyn_cast<InputSection<ELFT>>(Target)) {
S->RelocSections.push_back(&Sec);
break;
}
if (auto *S = dyn_cast<EHInputSection<ELFT>>(Target)) {
if (S->RelocSection)
fatal("multiple relocation sections to .eh_frame are not supported");
S->RelocSection = &Sec;
break;
}
fatal("relocations pointing to SHF_MERGE are not supported");
}
default:
Sections[I] = createInputSection(Sec);
}
}
}
template <class ELFT>
InputSectionBase<ELFT> *
elf::ObjectFile<ELFT>::getRelocTarget(const Elf_Shdr &Sec) {
uint32_t Idx = Sec.sh_info;
if (Idx >= Sections.size())
fatal("invalid relocated section index");
InputSectionBase<ELFT> *Target = Sections[Idx];
// Strictly speaking, a relocation section must be included in the
// group of the section it relocates. However, LLVM 3.3 and earlier
// would fail to do so, so we gracefully handle that case.
if (Target == InputSection<ELFT>::Discarded)
return nullptr;
if (!Target)
fatal("unsupported relocation reference");
return Target;
}
template <class ELFT>
InputSectionBase<ELFT> *
elf::ObjectFile<ELFT>::createInputSection(const Elf_Shdr &Sec) {
StringRef Name = check(this->ELFObj.getSectionName(&Sec));
// .note.GNU-stack is a marker section to control the presence of
// PT_GNU_STACK segment in outputs. Since the presence of the segment
// is controlled only by the command line option (-z execstack) in LLD,
// .note.GNU-stack is ignored.
if (Name == ".note.GNU-stack")
return InputSection<ELFT>::Discarded;
if (Name == ".note.GNU-split-stack")
error("objects using splitstacks are not supported");
// A MIPS object file has a special section that contains register
// usage info, which needs to be handled by the linker specially.
if (Config->EMachine == EM_MIPS && Name == ".reginfo") {
MipsReginfo = new (Alloc) MipsReginfoInputSection<ELFT>(this, &Sec);
return MipsReginfo;
}
// We dont need special handling of .eh_frame sections if relocatable
// output was choosen. Proccess them as usual input sections.
if (!Config->Relocatable && Name == ".eh_frame")
return new (EHAlloc.Allocate()) EHInputSection<ELFT>(this, &Sec);
if (shouldMerge<ELFT>(Sec))
return new (MAlloc.Allocate()) MergeInputSection<ELFT>(this, &Sec);
return new (Alloc) InputSection<ELFT>(this, &Sec);
}
template <class ELFT> void elf::ObjectFile<ELFT>::initializeSymbols() {
this->initStringTable();
Elf_Sym_Range Syms = this->getElfSymbols(false);
uint32_t NumSymbols = std::distance(Syms.begin(), Syms.end());
SymbolBodies.reserve(NumSymbols);
for (const Elf_Sym &Sym : Syms)
SymbolBodies.push_back(createSymbolBody(&Sym));
}
template <class ELFT>
InputSectionBase<ELFT> *
elf::ObjectFile<ELFT>::getSection(const Elf_Sym &Sym) const {
uint32_t Index = this->getSectionIndex(Sym);
if (Index == 0)
return nullptr;
if (Index >= Sections.size() || !Sections[Index])
fatal("invalid section index");
InputSectionBase<ELFT> *S = Sections[Index];
if (S == InputSectionBase<ELFT>::Discarded)
return S;
return S->Repl;
}
template <class ELFT>
SymbolBody *elf::ObjectFile<ELFT>::createSymbolBody(const Elf_Sym *Sym) {
unsigned char Binding = Sym->getBinding();
InputSectionBase<ELFT> *Sec = getSection(*Sym);
if (Binding == STB_LOCAL) {
if (Sec == InputSection<ELFT>::Discarded)
Sec = nullptr;
return new (Alloc) DefinedRegular<ELFT>("", *Sym, Sec);
}
StringRef Name = check(Sym->getName(this->StringTable));
switch (Sym->st_shndx) {
case SHN_UNDEF:
return new (Alloc) UndefinedElf<ELFT>(Name, *Sym);
case SHN_COMMON:
return new (Alloc) DefinedCommon(Name, Sym->st_size, Sym->st_value,
Sym->getBinding() == llvm::ELF::STB_WEAK,
Sym->getVisibility());
}
switch (Binding) {
default:
fatal("unexpected binding");
case STB_GLOBAL:
case STB_WEAK:
case STB_GNU_UNIQUE:
if (Sec == InputSection<ELFT>::Discarded)
return new (Alloc) UndefinedElf<ELFT>(Name, *Sym);
return new (Alloc) DefinedRegular<ELFT>(Name, *Sym, Sec);
}
}
void ArchiveFile::parse() {
File = check(Archive::create(MB), "failed to parse archive");
// Allocate a buffer for Lazy objects.
size_t NumSyms = File->getNumberOfSymbols();
LazySymbols.reserve(NumSyms);
// Read the symbol table to construct Lazy objects.
for (const Archive::Symbol &Sym : File->symbols())
LazySymbols.emplace_back(this, Sym);
}
// Returns a buffer pointing to a member file containing a given symbol.
MemoryBufferRef ArchiveFile::getMember(const Archive::Symbol *Sym) {
Archive::Child C =
check(Sym->getMember(),
"could not get the member for symbol " + Sym->getName());
if (!Seen.insert(C.getChildOffset()).second)
return MemoryBufferRef();
return check(C.getMemoryBufferRef(),
"could not get the buffer for the member defining symbol " +
Sym->getName());
}
template <class ELFT>
SharedFile<ELFT>::SharedFile(MemoryBufferRef M)
: ELFFileBase<ELFT>(Base::SharedKind, M), AsNeeded(Config->AsNeeded) {}
template <class ELFT>
const typename ELFT::Shdr *
SharedFile<ELFT>::getSection(const Elf_Sym &Sym) const {
uint32_t Index = this->getSectionIndex(Sym);
if (Index == 0)
return nullptr;
return check(this->ELFObj.getSection(Index));
}
// Partially parse the shared object file so that we can call
// getSoName on this object.
template <class ELFT> void SharedFile<ELFT>::parseSoName() {
typedef typename ELFT::Dyn Elf_Dyn;
typedef typename ELFT::uint uintX_t;
const Elf_Shdr *DynamicSec = nullptr;
const ELFFile<ELFT> Obj = this->ELFObj;
for (const Elf_Shdr &Sec : Obj.sections()) {
switch (Sec.sh_type) {
default:
continue;
case SHT_DYNSYM:
this->Symtab = &Sec;
break;
case SHT_DYNAMIC:
DynamicSec = &Sec;
break;
case SHT_SYMTAB_SHNDX:
this->SymtabSHNDX = check(Obj.getSHNDXTable(Sec));
break;
}
}
this->initStringTable();
SoName = this->getName();
if (!DynamicSec)
return;
auto *Begin =
reinterpret_cast<const Elf_Dyn *>(Obj.base() + DynamicSec->sh_offset);
const Elf_Dyn *End = Begin + DynamicSec->sh_size / sizeof(Elf_Dyn);
for (const Elf_Dyn &Dyn : make_range(Begin, End)) {
if (Dyn.d_tag == DT_SONAME) {
uintX_t Val = Dyn.getVal();
if (Val >= this->StringTable.size())
fatal("invalid DT_SONAME entry");
SoName = StringRef(this->StringTable.data() + Val);
return;
}
}
}
// Fully parse the shared object file. This must be called after parseSoName().
template <class ELFT> void SharedFile<ELFT>::parseRest() {
Elf_Sym_Range Syms = this->getElfSymbols(true);
uint32_t NumSymbols = std::distance(Syms.begin(), Syms.end());
SymbolBodies.reserve(NumSymbols);
for (const Elf_Sym &Sym : Syms) {
StringRef Name = check(Sym.getName(this->StringTable));
if (Sym.isUndefined())
Undefs.push_back(Name);
else
SymbolBodies.emplace_back(this, Name, Sym);
}
}
BitcodeFile::BitcodeFile(MemoryBufferRef M) : InputFile(BitcodeKind, M) {}
bool BitcodeFile::classof(const InputFile *F) {
return F->kind() == BitcodeKind;
}
static uint8_t getGvVisibility(const GlobalValue *GV) {
switch (GV->getVisibility()) {
case GlobalValue::DefaultVisibility:
return STV_DEFAULT;
case GlobalValue::HiddenVisibility:
return STV_HIDDEN;
case GlobalValue::ProtectedVisibility:
return STV_PROTECTED;
}
llvm_unreachable("unknown visibility");
}
SymbolBody *
BitcodeFile::createSymbolBody(const DenseSet<const Comdat *> &KeptComdats,
const IRObjectFile &Obj,
const BasicSymbolRef &Sym) {
const GlobalValue *GV = Obj.getSymbolGV(Sym.getRawDataRefImpl());
assert(GV);
if (const Comdat *C = GV->getComdat())
if (!KeptComdats.count(C))
return nullptr;
uint8_t Visibility = getGvVisibility(GV);
SmallString<64> Name;
raw_svector_ostream OS(Name);
Sym.printName(OS);
StringRef NameRef = Saver.save(StringRef(Name));
const Module &M = Obj.getModule();
SymbolBody *Body;
uint32_t Flags = Sym.getFlags();
bool IsWeak = Flags & BasicSymbolRef::SF_Weak;
if (Flags & BasicSymbolRef::SF_Undefined) {
Body = new (Alloc) Undefined(NameRef, IsWeak, Visibility, false);
} else if (Flags & BasicSymbolRef::SF_Common) {
const DataLayout &DL = M.getDataLayout();
uint64_t Size = DL.getTypeAllocSize(GV->getValueType());
Body = new (Alloc)
DefinedCommon(NameRef, Size, GV->getAlignment(), IsWeak, Visibility);
} else {
Body = new (Alloc) DefinedBitcode(NameRef, IsWeak, Visibility);
}
Body->IsTls = GV->isThreadLocal();
return Body;
}
bool BitcodeFile::shouldSkip(const BasicSymbolRef &Sym) {
uint32_t Flags = Sym.getFlags();
if (!(Flags & BasicSymbolRef::SF_Global))
return true;
if (Flags & BasicSymbolRef::SF_FormatSpecific)
return true;
return false;
}
void BitcodeFile::parse(DenseSet<StringRef> &ComdatGroups) {
LLVMContext Context;
std::unique_ptr<IRObjectFile> Obj = check(IRObjectFile::create(MB, Context));
const Module &M = Obj->getModule();
DenseSet<const Comdat *> KeptComdats;
for (const auto &P : M.getComdatSymbolTable()) {
StringRef N = Saver.save(P.first());
if (ComdatGroups.insert(N).second)
KeptComdats.insert(&P.second);
}
for (const BasicSymbolRef &Sym : Obj->symbols())
if (!shouldSkip(Sym))
SymbolBodies.push_back(createSymbolBody(KeptComdats, *Obj, Sym));
}
template <typename T>
static std::unique_ptr<InputFile> createELFFileAux(MemoryBufferRef MB) {
std::unique_ptr<T> Ret = llvm::make_unique<T>(MB);
if (!Config->FirstElf)
Config->FirstElf = Ret.get();
if (Config->EKind == ELFNoneKind) {
Config->EKind = Ret->getELFKind();
Config->EMachine = Ret->getEMachine();
}
return std::move(Ret);
}
template <template <class> class T>
static std::unique_ptr<InputFile> createELFFile(MemoryBufferRef MB) {
std::pair<unsigned char, unsigned char> Type = getElfArchType(MB.getBuffer());
if (Type.second != ELF::ELFDATA2LSB && Type.second != ELF::ELFDATA2MSB)
fatal("invalid data encoding: " + MB.getBufferIdentifier());
if (Type.first == ELF::ELFCLASS32) {
if (Type.second == ELF::ELFDATA2LSB)
return createELFFileAux<T<ELF32LE>>(MB);
return createELFFileAux<T<ELF32BE>>(MB);
}
if (Type.first == ELF::ELFCLASS64) {
if (Type.second == ELF::ELFDATA2LSB)
return createELFFileAux<T<ELF64LE>>(MB);
return createELFFileAux<T<ELF64BE>>(MB);
}
fatal("invalid file class: " + MB.getBufferIdentifier());
}
std::unique_ptr<InputFile> elf::createObjectFile(MemoryBufferRef MB,
StringRef ArchiveName) {
using namespace sys::fs;
std::unique_ptr<InputFile> F;
if (identify_magic(MB.getBuffer()) == file_magic::bitcode)
F.reset(new BitcodeFile(MB));
else
F = createELFFile<ObjectFile>(MB);
F->ArchiveName = ArchiveName;
return F;
}
std::unique_ptr<InputFile> elf::createSharedFile(MemoryBufferRef MB) {
return createELFFile<SharedFile>(MB);
}
template class elf::ELFFileBase<ELF32LE>;
template class elf::ELFFileBase<ELF32BE>;
template class elf::ELFFileBase<ELF64LE>;
template class elf::ELFFileBase<ELF64BE>;
template class elf::ObjectFile<ELF32LE>;
template class elf::ObjectFile<ELF32BE>;
template class elf::ObjectFile<ELF64LE>;
template class elf::ObjectFile<ELF64BE>;
template class elf::SharedFile<ELF32LE>;
template class elf::SharedFile<ELF32BE>;
template class elf::SharedFile<ELF64LE>;
template class elf::SharedFile<ELF64BE>;