llvm-project/lld/ELF/InputFiles.cpp

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//===- 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"
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#include "InputSection.h"
#include "Symbols.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/IR/LLVMContext.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;
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using namespace lld::elf;
namespace {
class ECRAII {
std::error_code EC;
public:
std::error_code &getEC() { return EC; }
~ECRAII() { fatal(EC); }
};
}
template <class ELFT>
ELFFileBase<ELFT>::ELFFileBase(Kind K, MemoryBufferRef M)
: InputFile(K, M), ELFObj(MB.getBuffer(), ECRAII().getEC()) {}
template <class ELFT>
ELFKind ELFFileBase<ELFT>::getELFKind() {
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if (ELFT::TargetEndianness == support::little)
return ELFT::Is64Bits ? ELF64LEKind : ELF32LEKind;
return ELFT::Is64Bits ? ELF64BEKind : ELF32BEKind;
}
template <class ELFT>
typename ELFFileBase<ELFT>::Elf_Sym_Range
ELFFileBase<ELFT>::getSymbolsHelper(bool Local) {
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 (!Local)
return make_range(Syms.begin() + FirstNonLocal, Syms.end());
// +1 to skip over dummy symbol.
return make_range(Syms.begin() + 1, Syms.begin() + FirstNonLocal);
}
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 || I == ELF::SHN_ABS)
return 0;
return I;
}
template <class ELFT> void ELFFileBase<ELFT>::initStringTable() {
if (!Symtab)
return;
ErrorOr<StringRef> StringTableOrErr = ELFObj.getStringTableForSymtab(*Symtab);
fatal(StringTableOrErr);
StringTable = *StringTableOrErr;
}
template <class ELFT>
typename ELFFileBase<ELFT>::Elf_Sym_Range
ELFFileBase<ELFT>::getNonLocalSymbols() {
return getSymbolsHelper(false);
}
template <class ELFT>
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elf::ObjectFile<ELFT>::ObjectFile(MemoryBufferRef M)
: ELFFileBase<ELFT>(Base::ObjectKind, M) {}
template <class ELFT>
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typename elf::ObjectFile<ELFT>::Elf_Sym_Range
elf::ObjectFile<ELFT>::getLocalSymbols() {
return this->getSymbolsHelper(true);
}
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template <class ELFT> uint32_t elf::ObjectFile<ELFT>::getMipsGp0() const {
if (MipsReginfo)
return MipsReginfo->Reginfo->ri_gp_value;
return 0;
}
template <class ELFT>
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const typename elf::ObjectFile<ELFT>::Elf_Sym *
elf::ObjectFile<ELFT>::getLocalSymbol(uintX_t SymIndex) {
uint32_t FirstNonLocal = this->Symtab->sh_info;
if (SymIndex >= FirstNonLocal)
return nullptr;
Elf_Sym_Range Syms = this->ELFObj.symbols(this->Symtab);
return Syms.begin() + SymIndex;
}
template <class ELFT>
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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>
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StringRef elf::ObjectFile<ELFT>::getShtGroupSignature(const Elf_Shdr &Sec) {
const ELFFile<ELFT> &Obj = this->ELFObj;
uint32_t SymtabdSectionIndex = Sec.sh_link;
ErrorOr<const Elf_Shdr *> SecOrErr = Obj.getSection(SymtabdSectionIndex);
fatal(SecOrErr);
const Elf_Shdr *SymtabSec = *SecOrErr;
uint32_t SymIndex = Sec.sh_info;
const Elf_Sym *Sym = Obj.getSymbol(SymtabSec, SymIndex);
ErrorOr<StringRef> StringTableOrErr = Obj.getStringTableForSymtab(*SymtabSec);
fatal(StringTableOrErr);
ErrorOr<StringRef> SignatureOrErr = Sym->getName(*StringTableOrErr);
fatal(SignatureOrErr);
return *SignatureOrErr;
}
template <class ELFT>
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ArrayRef<typename elf::ObjectFile<ELFT>::uint32_X>
elf::ObjectFile<ELFT>::getShtGroupEntries(const Elf_Shdr &Sec) {
const ELFFile<ELFT> &Obj = this->ELFObj;
ErrorOr<ArrayRef<uint32_X>> EntriesOrErr =
Obj.template getSectionContentsAsArray<uint32_X>(&Sec);
fatal(EntriesOrErr);
ArrayRef<uint32_X> Entries = *EntriesOrErr;
if (Entries.empty() || Entries[0] != GRP_COMDAT)
fatal("Unsupported SHT_GROUP format");
return Entries.slice(1);
}
template <class ELFT>
static bool shouldMerge(const typename ELFFile<ELFT>::Elf_Shdr &Sec) {
typedef typename ELFFile<ELFT>::uintX_t 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>
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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: {
ErrorOr<ArrayRef<Elf_Word>> ErrorOrTable = Obj.getSHNDXTable(Sec);
fatal(ErrorOrTable);
this->SymtabSHNDX = *ErrorOrTable;
break;
}
case SHT_STRTAB:
case SHT_NULL:
break;
case SHT_RELA:
case SHT_REL: {
uint32_t RelocatedSectionIndex = Sec.sh_info;
if (RelocatedSectionIndex >= Size)
fatal("Invalid relocated section index");
InputSectionBase<ELFT> *RelocatedSection =
Sections[RelocatedSectionIndex];
// 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 (RelocatedSection == InputSection<ELFT>::Discarded)
continue;
if (!RelocatedSection)
fatal("Unsupported relocation reference");
if (Config->Relocatable) {
// For -r, relocation sections are handled as regular input sections.
Sections[I] = new (Alloc) InputSection<ELFT>(this, &Sec);
} else if (auto *S = dyn_cast<InputSection<ELFT>>(RelocatedSection)) {
S->RelocSections.push_back(&Sec);
} else if (auto *S = dyn_cast<EHInputSection<ELFT>>(RelocatedSection)) {
if (S->RelocSection)
fatal("Multiple relocation sections to .eh_frame are not supported");
S->RelocSection = &Sec;
} else {
fatal("Relocations pointing to SHF_MERGE are not supported");
}
break;
}
default:
Sections[I] = createInputSection(Sec);
}
}
}
template <class ELFT>
InputSectionBase<ELFT> *
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elf::ObjectFile<ELFT>::createInputSection(const Elf_Shdr &Sec) {
ErrorOr<StringRef> NameOrErr = this->ELFObj.getSectionName(&Sec);
fatal(NameOrErr);
StringRef Name = *NameOrErr;
// .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;
// 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;
}
if (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);
}
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template <class ELFT> void elf::ObjectFile<ELFT>::initializeSymbols() {
this->initStringTable();
Elf_Sym_Range Syms = this->getNonLocalSymbols();
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> *
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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>
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SymbolBody *elf::ObjectFile<ELFT>::createSymbolBody(const Elf_Sym *Sym) {
ErrorOr<StringRef> NameOrErr = Sym->getName(this->StringTable);
fatal(NameOrErr);
StringRef Name = *NameOrErr;
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 (Sym->getBinding()) {
default:
fatal("unexpected binding");
case STB_GLOBAL:
case STB_WEAK:
case STB_GNU_UNIQUE: {
InputSectionBase<ELFT> *Sec = getSection(*Sym);
if (Sec == InputSection<ELFT>::Discarded)
return new (Alloc) UndefinedElf<ELFT>(Name, *Sym);
return new (Alloc) DefinedRegular<ELFT>(Name, *Sym, Sec);
}
}
}
void ArchiveFile::parse() {
ErrorOr<std::unique_ptr<Archive>> FileOrErr = Archive::create(MB);
fatal(FileOrErr, "Failed to parse archive");
File = std::move(*FileOrErr);
// 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) {
ErrorOr<Archive::Child> COrErr = Sym->getMember();
fatal(COrErr, "Could not get the member for symbol " + Sym->getName());
const Archive::Child &C = *COrErr;
if (!Seen.insert(C.getChildOffset()).second)
return MemoryBufferRef();
ErrorOr<MemoryBufferRef> RefOrErr = C.getMemoryBufferRef();
if (!RefOrErr)
fatal(RefOrErr, "Could not get the buffer for the member defining symbol " +
Sym->getName());
return *RefOrErr;
}
template <class ELFT>
SharedFile<ELFT>::SharedFile(MemoryBufferRef M)
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: ELFFileBase<ELFT>(Base::SharedKind, M), AsNeeded(Config->AsNeeded) {}
template <class ELFT>
const typename ELFFile<ELFT>::Elf_Shdr *
SharedFile<ELFT>::getSection(const Elf_Sym &Sym) const {
uint32_t Index = this->getSectionIndex(Sym);
if (Index == 0)
return nullptr;
ErrorOr<const Elf_Shdr *> Ret = this->ELFObj.getSection(Index);
fatal(Ret);
return *Ret;
}
// Partially parse the shared object file so that we can call
// getSoName on this object.
template <class ELFT> void SharedFile<ELFT>::parseSoName() {
typedef typename ELFFile<ELFT>::Elf_Dyn Elf_Dyn;
typedef typename ELFFile<ELFT>::uintX_t 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: {
ErrorOr<ArrayRef<Elf_Word>> ErrorOrTable = Obj.getSHNDXTable(Sec);
fatal(ErrorOrTable);
this->SymtabSHNDX = *ErrorOrTable;
break;
}
}
}
this->initStringTable();
SoName = this->getName();
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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);
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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->getNonLocalSymbols();
uint32_t NumSymbols = std::distance(Syms.begin(), Syms.end());
SymbolBodies.reserve(NumSymbols);
for (const Elf_Sym &Sym : Syms) {
ErrorOr<StringRef> NameOrErr = Sym.getName(this->StringTable);
fatal(NameOrErr.getError());
StringRef Name = *NameOrErr;
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;
}
void BitcodeFile::parse() {
LLVMContext Context;
ErrorOr<std::unique_ptr<IRObjectFile>> ObjOrErr =
IRObjectFile::create(MB, Context);
fatal(ObjOrErr);
IRObjectFile &Obj = **ObjOrErr;
for (const BasicSymbolRef &Sym : Obj.symbols()) {
SmallString<64> Name;
raw_svector_ostream OS(Name);
Sym.printName(OS);
StringRef NameRef = Saver.save(StringRef(Name));
SymbolBody *Body;
uint32_t Flags = Sym.getFlags();
bool IsWeak = Flags & BasicSymbolRef::SF_Weak;
if (Flags & BasicSymbolRef::SF_Undefined)
Body = new (Alloc) Undefined(NameRef, IsWeak, STV_DEFAULT, false);
else
Body = new (Alloc) DefinedBitcode(NameRef, IsWeak);
SymbolBodies.push_back(Body);
}
}
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());
}
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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;
}
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std::unique_ptr<InputFile> elf::createSharedFile(MemoryBufferRef MB) {
return createELFFile<SharedFile>(MB);
}
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template class elf::ELFFileBase<ELF32LE>;
template class elf::ELFFileBase<ELF32BE>;
template class elf::ELFFileBase<ELF64LE>;
template class elf::ELFFileBase<ELF64BE>;
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template class elf::ObjectFile<ELF32LE>;
template class elf::ObjectFile<ELF32BE>;
template class elf::ObjectFile<ELF64LE>;
template class elf::ObjectFile<ELF64BE>;
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template class elf::SharedFile<ELF32LE>;
template class elf::SharedFile<ELF32BE>;
template class elf::SharedFile<ELF64LE>;
template class elf::SharedFile<ELF64BE>;