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 "InputSection.h"
#include "Error.h"
#include "Symbols.h"
#include "llvm/ADT/STLExtras.h"
using namespace llvm;
using namespace llvm::ELF;
using namespace llvm::object;
using namespace llvm::sys::fs;
using namespace lld;
using namespace lld::elf2;
namespace {
class ECRAII {
std::error_code EC;
public:
std::error_code &getEC() { return EC; }
~ECRAII() { error(EC); }
};
}
template <class ELFT>
ELFFileBase<ELFT>::ELFFileBase(Kind K, MemoryBufferRef M)
: InputFile(K, M), ELFObj(MB.getBuffer(), ECRAII().getEC()) {}
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)
error("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 Index = Sym.st_shndx;
if (Index == ELF::SHN_XINDEX)
Index = this->ELFObj.getExtendedSymbolTableIndex(&Sym, this->Symtab,
SymtabSHNDX);
else if (Index == ELF::SHN_UNDEF || Index >= ELF::SHN_LORESERVE)
return 0;
if (!Index)
error("Invalid section index");
return Index;
}
template <class ELFT> void ELFFileBase<ELFT>::initStringTable() {
if (!Symtab)
return;
ErrorOr<StringRef> StringTableOrErr = ELFObj.getStringTableForSymtab(*Symtab);
error(StringTableOrErr.getError());
StringTable = *StringTableOrErr;
}
template <class ELFT>
typename ELFFileBase<ELFT>::Elf_Sym_Range
ELFFileBase<ELFT>::getNonLocalSymbols() {
return getSymbolsHelper(false);
}
template <class ELFT>
ObjectFile<ELFT>::ObjectFile(MemoryBufferRef M)
: ELFFileBase<ELFT>(Base::ObjectKind, M) {}
template <class ELFT>
typename ObjectFile<ELFT>::Elf_Sym_Range ObjectFile<ELFT>::getLocalSymbols() {
return this->getSymbolsHelper(true);
}
template <class ELFT>
const typename ObjectFile<ELFT>::Elf_Sym *
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>
void elf2::ObjectFile<ELFT>::parse(DenseSet<StringRef> &Comdats) {
// Read section and symbol tables.
initializeSections(Comdats);
initializeSymbols();
}
template <class ELFT>
StringRef 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);
error(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);
error(StringTableOrErr);
ErrorOr<StringRef> SignatureOrErr = Sym->getName(*StringTableOrErr);
error(SignatureOrErr);
return *SignatureOrErr;
}
template <class ELFT>
ArrayRef<typename ObjectFile<ELFT>::GroupEntryType>
ObjectFile<ELFT>::getShtGroupEntries(const Elf_Shdr &Sec) {
const ELFFile<ELFT> &Obj = this->ELFObj;
ErrorOr<ArrayRef<GroupEntryType>> EntriesOrErr =
Obj.template getSectionContentsAsArray<GroupEntryType>(&Sec);
error(EntriesOrErr.getError());
ArrayRef<GroupEntryType> Entries = *EntriesOrErr;
if (Entries.empty() || Entries[0] != GRP_COMDAT)
error("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)
error("Writable SHF_MERGE sections are not supported");
uintX_t EntSize = Sec.sh_entsize;
if (Sec.sh_size % EntSize)
error("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.
//
// If 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 this is a SHF_STRINGS, the larger alignment makes sense. Unfortunately
// it would complicate tail merging. This doesn't seem that common to
// justify the effort.
if (Sec.sh_addralign > EntSize)
return false;
return true;
}
template <class ELFT>
void elf2::ObjectFile<ELFT>::initializeSections(DenseSet<StringRef> &Comdats) {
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 (Comdats.insert(getShtGroupSignature(Sec)).second)
continue;
for (GroupEntryType E : getShtGroupEntries(Sec)) {
uint32_t SecIndex = E;
if (SecIndex >= Size)
error("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);
error(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)
error("Invalid relocated section index");
InputSectionBase<ELFT> *RelocatedSection =
Sections[RelocatedSectionIndex];
if (!RelocatedSection)
error("Unsupported relocation reference");
if (auto *S = dyn_cast<InputSection<ELFT>>(RelocatedSection))
S->RelocSections.push_back(&Sec);
else
error("Relocations pointing to SHF_MERGE are not supported");
break;
}
default:
if (shouldMerge<ELFT>(Sec))
Sections[I] = new (this->Alloc) MergeInputSection<ELFT>(this, &Sec);
else
Sections[I] = new (this->Alloc) InputSection<ELFT>(this, &Sec);
break;
}
}
}
template <class ELFT> void elf2::ObjectFile<ELFT>::initializeSymbols() {
this->initStringTable();
Elf_Sym_Range Syms = this->getNonLocalSymbols();
uint32_t NumSymbols = std::distance(Syms.begin(), Syms.end());
this->SymbolBodies.reserve(NumSymbols);
for (const Elf_Sym &Sym : Syms)
this->SymbolBodies.push_back(createSymbolBody(this->StringTable, &Sym));
}
template <class ELFT>
InputSectionBase<ELFT> *
elf2::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])
error("Invalid section index");
return Sections[Index];
}
template <class ELFT>
SymbolBody *elf2::ObjectFile<ELFT>::createSymbolBody(StringRef StringTable,
const Elf_Sym *Sym) {
ErrorOr<StringRef> NameOrErr = Sym->getName(StringTable);
error(NameOrErr.getError());
StringRef Name = *NameOrErr;
switch (Sym->st_shndx) {
case SHN_ABS:
return new (this->Alloc) DefinedAbsolute<ELFT>(Name, *Sym);
case SHN_UNDEF:
return new (this->Alloc) Undefined<ELFT>(Name, *Sym);
case SHN_COMMON:
return new (this->Alloc) DefinedCommon<ELFT>(Name, *Sym);
}
switch (Sym->getBinding()) {
default:
error("unexpected binding");
case STB_GLOBAL:
case STB_WEAK:
case STB_GNU_UNIQUE: {
InputSectionBase<ELFT> *Sec = getSection(*Sym);
if (Sec == &InputSection<ELFT>::Discarded)
return new (this->Alloc) Undefined<ELFT>(Name, *Sym);
return new (this->Alloc) DefinedRegular<ELFT>(Name, *Sym, *Sec);
}
}
}
static std::unique_ptr<Archive> openArchive(MemoryBufferRef MB) {
ErrorOr<std::unique_ptr<Archive>> ArchiveOrErr = Archive::create(MB);
error(ArchiveOrErr, "Failed to parse archive");
return std::move(*ArchiveOrErr);
}
void ArchiveFile::parse() {
File = openArchive(MB);
// 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();
error(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> Ret = C.getMemoryBufferRef();
error(Ret, "Could not get the buffer for the member defining symbol " +
Sym->getName());
return *Ret;
}
std::vector<MemoryBufferRef> ArchiveFile::getMembers() {
File = openArchive(MB);
std::vector<MemoryBufferRef> Result;
for (const Archive::Child &Child : File->children()) {
ErrorOr<MemoryBufferRef> MbOrErr = Child.getMemoryBufferRef();
error(MbOrErr, "Could not get the buffer for a child of the archive " +
File->getFileName());
Result.push_back(MbOrErr.get());
}
return Result;
}
template <class ELFT>
SharedFile<ELFT>::SharedFile(MemoryBufferRef M)
: 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);
error(Ret);
return *Ret;
}
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);
error(ErrorOrTable);
this->SymtabSHNDX = *ErrorOrTable;
break;
}
}
}
this->initStringTable();
this->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())
error("Invalid DT_SONAME entry");
this->SoName = StringRef(this->StringTable.data() + Val);
return;
}
}
}
template <class ELFT> void SharedFile<ELFT>::parse() {
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);
error(NameOrErr.getError());
StringRef Name = *NameOrErr;
if (Sym.isUndefined())
Undefs.push_back(Name);
else
SymbolBodies.emplace_back(this, Name, 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>
std::unique_ptr<InputFile> lld::elf2::createELFFile(MemoryBufferRef MB) {
using namespace llvm;
std::pair<unsigned char, unsigned char> Type =
object::getElfArchType(MB.getBuffer());
if (Type.second != ELF::ELFDATA2LSB && Type.second != ELF::ELFDATA2MSB)
error("Invalid data encoding: " + MB.getBufferIdentifier());
if (Type.first == ELF::ELFCLASS32) {
if (Type.second == ELF::ELFDATA2LSB)
return createELFFileAux<T<object::ELF32LE>>(MB);
return createELFFileAux<T<object::ELF32BE>>(MB);
}
if (Type.first == ELF::ELFCLASS64) {
if (Type.second == ELF::ELFDATA2LSB)
return createELFFileAux<T<object::ELF64LE>>(MB);
return createELFFileAux<T<object::ELF64BE>>(MB);
}
error("Invalid file class: " + MB.getBufferIdentifier());
}
namespace lld {
namespace elf2 {
template class ELFFileBase<llvm::object::ELF32LE>;
template class ELFFileBase<llvm::object::ELF32BE>;
template class ELFFileBase<llvm::object::ELF64LE>;
template class ELFFileBase<llvm::object::ELF64BE>;
template class ObjectFile<llvm::object::ELF32LE>;
template class ObjectFile<llvm::object::ELF32BE>;
template class ObjectFile<llvm::object::ELF64LE>;
template class ObjectFile<llvm::object::ELF64BE>;
template class SharedFile<llvm::object::ELF32LE>;
template class SharedFile<llvm::object::ELF32BE>;
template class SharedFile<llvm::object::ELF64LE>;
template class SharedFile<llvm::object::ELF64BE>;
template std::unique_ptr<InputFile> createELFFile<ObjectFile>(MemoryBufferRef);
template std::unique_ptr<InputFile> createELFFile<SharedFile>(MemoryBufferRef);
}
}