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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 "Driver.h"
#include "ELFCreator.h"
#include "Error.h"
#include "InputSection.h"
#include "LinkerScript.h"
#include "SymbolTable.h"
#include "Symbols.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Bitcode/ReaderWriter.h"
#include "llvm/CodeGen/Analysis.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/LTO/LTO.h"
#include "llvm/MC/StringTableBuilder.h"
#include "llvm/Support/Path.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;
std::vector<InputFile *> InputFile::Pool;
// Deletes all InputFile instances created so far.
void InputFile::freePool() {
// Files are freed in reverse order so that files created
// from other files (e.g. object files extracted from archives)
// are freed in the proper order.
for (int I = Pool.size() - 1; I >= 0; --I)
delete Pool[I];
}
// Returns "(internal)", "foo.a(bar.o)" or "baz.o".
std::string elf::getFilename(const InputFile *F) {
if (!F)
return "(internal)";
if (!F->ArchiveName.empty())
return (F->ArchiveName + "(" + F->getName() + ")").str();
return F->getName();
}
template <class ELFT>
static ELFFile<ELFT> createELFObj(MemoryBufferRef MB) {
std::error_code EC;
ELFFile<ELFT> F(MB.getBuffer(), EC);
if (EC)
error(EC, "failed to read " + MB.getBufferIdentifier());
return F;
}
template <class ELFT> static ELFKind getELFKind() {
if (ELFT::TargetEndianness == support::little)
return ELFT::Is64Bits ? ELF64LEKind : ELF32LEKind;
return ELFT::Is64Bits ? ELF64BEKind : ELF32BEKind;
}
template <class ELFT>
ELFFileBase<ELFT>::ELFFileBase(Kind K, MemoryBufferRef MB)
: InputFile(K, MB), ELFObj(createELFObj<ELFT>(MB)) {
EKind = getELFKind<ELFT>();
EMachine = ELFObj.getHeader()->e_machine;
}
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(getFilename(this) + ": invalid sh_info in symbol table");
if (OnlyGlobals)
return makeArrayRef(Syms.begin() + FirstNonLocal, Syms.end());
return makeArrayRef(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 (ELFT::Is64Bits && MipsOptions && MipsOptions->Reginfo)
return MipsOptions->Reginfo->ri_gp_value;
if (!ELFT::Is64Bits && MipsReginfo && MipsReginfo->Reginfo)
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;
const Elf_Shdr *Symtab = check(Obj.getSection(Sec.sh_link));
const Elf_Sym *Sym = Obj.getSymbol(Symtab, Sec.sh_info);
StringRef Strtab = check(Obj.getStringTableForSymtab(*Symtab));
return check(Sym->getName(Strtab));
}
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(getFilename(this) + ": unsupported SHT_GROUP format");
return Entries.slice(1);
}
template <class ELFT>
bool elf::ObjectFile<ELFT>::shouldMerge(const Elf_Shdr &Sec) {
// We don't merge sections if -O0 (default is -O1). This makes sometimes
// the linker significantly faster, although the output will be bigger.
if (Config->Optimize == 0)
return false;
// A mergeable section with size 0 is useless because they don't have
// any data to merge. A mergeable string section with size 0 can be
// argued as invalid because it doesn't end with a null character.
// We'll avoid a mess by handling them as if they were non-mergeable.
if (Sec.sh_size == 0)
return false;
// Check for sh_entsize. The ELF spec is not clear about the zero
// sh_entsize. It says that "the member [sh_entsize] contains 0 if
// the section does not hold a table of fixed-size entries". We know
// that Rust 1.13 produces a string mergeable section with a zero
// sh_entsize. Here we just accept it rather than being picky about it.
uintX_t EntSize = Sec.sh_entsize;
if (EntSize == 0)
return false;
if (Sec.sh_size % EntSize)
fatal(getFilename(this) +
": SHF_MERGE section size must be a multiple of sh_entsize");
uintX_t Flags = Sec.sh_flags;
if (!(Flags & SHF_MERGE))
return false;
if (Flags & SHF_WRITE)
fatal(getFilename(this) + ": writable SHF_MERGE section is not supported");
// Don't try to merge if the alignment 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;
return Sec.sh_addralign <= EntSize;
}
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;
if (Sec.sh_flags & SHF_EXCLUDE) {
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(getFilename(this) + ": invalid section index in group: " +
Twine(SecIndex));
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;
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(getFilename(this) + ": invalid relocated section index: " +
Twine(Idx));
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(getFilename(this) + ": 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));
switch (Sec.sh_type) {
case SHT_ARM_ATTRIBUTES:
// FIXME: ARM meta-data section. At present attributes are ignored,
// they can be used to reason about object compatibility.
return &InputSection<ELFT>::Discarded;
case SHT_MIPS_REGINFO:
MipsReginfo.reset(new MipsReginfoInputSection<ELFT>(this, &Sec, Name));
return MipsReginfo.get();
case SHT_MIPS_OPTIONS:
MipsOptions.reset(new MipsOptionsInputSection<ELFT>(this, &Sec, Name));
return MipsOptions.get();
case SHT_MIPS_ABIFLAGS:
MipsAbiFlags.reset(new MipsAbiFlagsInputSection<ELFT>(this, &Sec, Name));
return MipsAbiFlags.get();
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)
return new (IAlloc.Allocate()) InputSection<ELFT>(this, &Sec, Name);
// Find the relocation target section and associate this
// section with it.
InputSectionBase<ELFT> *Target = getRelocTarget(Sec);
if (!Target)
return nullptr;
if (auto *S = dyn_cast<InputSection<ELFT>>(Target)) {
S->RelocSections.push_back(&Sec);
return nullptr;
}
if (auto *S = dyn_cast<EhInputSection<ELFT>>(Target)) {
if (S->RelocSection)
fatal(getFilename(this) +
": multiple relocation sections to .eh_frame are not supported");
S->RelocSection = &Sec;
return nullptr;
}
fatal(getFilename(this) +
": relocations pointing to SHF_MERGE are not supported");
}
}
// .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");
return &InputSection<ELFT>::Discarded;
}
if (Config->Strip != StripPolicy::None && Name.startswith(".debug"))
return &InputSection<ELFT>::Discarded;
// The linker merges EH (exception handling) frames and creates a
// .eh_frame_hdr section for runtime. So we handle them with a special
// class. For relocatable outputs, they are just passed through.
if (Name == ".eh_frame" && !Config->Relocatable)
return new (EHAlloc.Allocate()) EhInputSection<ELFT>(this, &Sec, Name);
if (shouldMerge(Sec))
return new (MAlloc.Allocate()) MergeInputSection<ELFT>(this, &Sec, Name);
return new (IAlloc.Allocate()) InputSection<ELFT>(this, &Sec, Name);
}
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())
fatal(getFilename(this) + ": invalid section index: " + Twine(Index));
InputSectionBase<ELFT> *S = Sections[Index];
// We found that GNU assembler 2.17.50 [FreeBSD] 2007-07-03
// could generate broken objects. STT_SECTION symbols can be
// associated with SHT_REL[A]/SHT_SYMTAB/SHT_STRTAB sections.
// In this case it is fine for section to be null here as we
// do not allocate sections of these types.
if (!S || S == &InputSectionBase<ELFT>::Discarded)
return S;
return S->Repl;
}
template <class ELFT>
SymbolBody *elf::ObjectFile<ELFT>::createSymbolBody(const Elf_Sym *Sym) {
int Binding = Sym->getBinding();
InputSectionBase<ELFT> *Sec = getSection(*Sym);
if (Binding == STB_LOCAL) {
if (Sym->st_shndx == SHN_UNDEF)
return new (this->Alloc)
Undefined(Sym->st_name, Sym->st_other, Sym->getType(), this);
return new (this->Alloc) DefinedRegular<ELFT>(*Sym, Sec);
}
StringRef Name = check(Sym->getName(this->StringTable));
switch (Sym->st_shndx) {
case SHN_UNDEF:
return elf::Symtab<ELFT>::X
->addUndefined(Name, Binding, Sym->st_other, Sym->getType(),
/*CanOmitFromDynSym*/ false, this)
->body();
case SHN_COMMON:
return elf::Symtab<ELFT>::X
->addCommon(Name, Sym->st_size, Sym->st_value, Binding, Sym->st_other,
Sym->getType(), this)
->body();
}
switch (Binding) {
default:
fatal(getFilename(this) + ": unexpected binding: " + Twine(Binding));
case STB_GLOBAL:
case STB_WEAK:
case STB_GNU_UNIQUE:
if (Sec == &InputSection<ELFT>::Discarded)
return elf::Symtab<ELFT>::X
->addUndefined(Name, Binding, Sym->st_other, Sym->getType(),
/*CanOmitFromDynSym*/ false, this)
->body();
return elf::Symtab<ELFT>::X->addRegular(Name, *Sym, Sec)->body();
}
}
template <class ELFT> void ArchiveFile::parse() {
File = check(Archive::create(MB), "failed to parse archive");
// Read the symbol table to construct Lazy objects.
bool IsEmpty = true;
for (const Archive::Symbol &Sym : File->symbols()) {
Symtab<ELFT>::X->addLazyArchive(this, Sym);
IsEmpty = false;
}
if (IsEmpty)
warn(getName() + " has no symbol. Chances are you are doing "
"an LTO build and forgot to use an ar command that can create "
"a symbol table for LLVM bitcode files. If so, use llvm-ar or "
"GNU ar + plugin.");
}
// 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();
MemoryBufferRef Ret =
check(C.getMemoryBufferRef(),
"could not get the buffer for the member defining symbol " +
Sym->getName());
if (C.getParent()->isThin() && Driver->Cpio)
Driver->Cpio->append(relativeToRoot(check(C.getFullName())),
Ret.getBuffer());
return Ret;
}
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;
case SHT_GNU_versym:
this->VersymSec = &Sec;
break;
case SHT_GNU_verdef:
this->VerdefSec = &Sec;
break;
}
}
this->initStringTable();
// DSOs are identified by soname, and they usually contain
// DT_SONAME tag in their header. But if they are missing,
// filenames are used as default sonames.
SoName = sys::path::filename(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(getFilename(this) + ": invalid DT_SONAME entry");
SoName = StringRef(this->StringTable.data() + Val);
return;
}
}
}
// Parse the version definitions in the object file if present. Returns a vector
// whose nth element contains a pointer to the Elf_Verdef for version identifier
// n. Version identifiers that are not definitions map to nullptr. The array
// always has at least length 1.
template <class ELFT>
std::vector<const typename ELFT::Verdef *>
SharedFile<ELFT>::parseVerdefs(const Elf_Versym *&Versym) {
std::vector<const Elf_Verdef *> Verdefs(1);
// We only need to process symbol versions for this DSO if it has both a
// versym and a verdef section, which indicates that the DSO contains symbol
// version definitions.
if (!VersymSec || !VerdefSec)
return Verdefs;
// The location of the first global versym entry.
Versym = reinterpret_cast<const Elf_Versym *>(this->ELFObj.base() +
VersymSec->sh_offset) +
this->Symtab->sh_info;
// We cannot determine the largest verdef identifier without inspecting
// every Elf_Verdef, but both bfd and gold assign verdef identifiers
// sequentially starting from 1, so we predict that the largest identifier
// will be VerdefCount.
unsigned VerdefCount = VerdefSec->sh_info;
Verdefs.resize(VerdefCount + 1);
// Build the Verdefs array by following the chain of Elf_Verdef objects
// from the start of the .gnu.version_d section.
const uint8_t *Verdef = this->ELFObj.base() + VerdefSec->sh_offset;
for (unsigned I = 0; I != VerdefCount; ++I) {
auto *CurVerdef = reinterpret_cast<const Elf_Verdef *>(Verdef);
Verdef += CurVerdef->vd_next;
unsigned VerdefIndex = CurVerdef->vd_ndx;
if (Verdefs.size() <= VerdefIndex)
Verdefs.resize(VerdefIndex + 1);
Verdefs[VerdefIndex] = CurVerdef;
}
return Verdefs;
}
// Fully parse the shared object file. This must be called after parseSoName().
template <class ELFT> void SharedFile<ELFT>::parseRest() {
// Create mapping from version identifiers to Elf_Verdef entries.
const Elf_Versym *Versym = nullptr;
std::vector<const Elf_Verdef *> Verdefs = parseVerdefs(Versym);
Elf_Sym_Range Syms = this->getElfSymbols(true);
for (const Elf_Sym &Sym : Syms) {
unsigned VersymIndex = 0;
if (Versym) {
VersymIndex = Versym->vs_index;
++Versym;
}
StringRef Name = check(Sym.getName(this->StringTable));
if (Sym.isUndefined()) {
Undefs.push_back(Name);
continue;
}
if (Versym) {
// Ignore local symbols and non-default versions.
if (VersymIndex == VER_NDX_LOCAL || (VersymIndex & VERSYM_HIDDEN))
continue;
}
const Elf_Verdef *V =
VersymIndex == VER_NDX_GLOBAL ? nullptr : Verdefs[VersymIndex];
elf::Symtab<ELFT>::X->addShared(this, Name, Sym, V);
}
}
static ELFKind getBitcodeELFKind(MemoryBufferRef MB) {
Triple T(getBitcodeTargetTriple(MB, Driver->Context));
if (T.isLittleEndian())
return T.isArch64Bit() ? ELF64LEKind : ELF32LEKind;
return T.isArch64Bit() ? ELF64BEKind : ELF32BEKind;
}
static uint8_t getBitcodeMachineKind(MemoryBufferRef MB) {
Triple T(getBitcodeTargetTriple(MB, Driver->Context));
switch (T.getArch()) {
case Triple::aarch64:
return EM_AARCH64;
case Triple::arm:
return EM_ARM;
case Triple::mips:
case Triple::mipsel:
case Triple::mips64:
case Triple::mips64el:
return EM_MIPS;
case Triple::ppc:
return EM_PPC;
case Triple::ppc64:
return EM_PPC64;
case Triple::x86:
return T.isOSIAMCU() ? EM_IAMCU : EM_386;
case Triple::x86_64:
return EM_X86_64;
default:
fatal(MB.getBufferIdentifier() +
": could not infer e_machine from bitcode target triple " + T.str());
}
}
BitcodeFile::BitcodeFile(MemoryBufferRef MB) : InputFile(BitcodeKind, MB) {
EKind = getBitcodeELFKind(MB);
EMachine = getBitcodeMachineKind(MB);
}
static uint8_t mapVisibility(GlobalValue::VisibilityTypes GvVisibility) {
switch (GvVisibility) {
case GlobalValue::DefaultVisibility:
return STV_DEFAULT;
case GlobalValue::HiddenVisibility:
return STV_HIDDEN;
case GlobalValue::ProtectedVisibility:
return STV_PROTECTED;
}
llvm_unreachable("unknown visibility");
}
template <class ELFT>
static Symbol *createBitcodeSymbol(const DenseSet<const Comdat *> &KeptComdats,
const lto::InputFile::Symbol &ObjSym,
StringSaver &Saver, BitcodeFile *F) {
StringRef NameRef = Saver.save(ObjSym.getName());
uint32_t Flags = ObjSym.getFlags();
uint32_t Binding = (Flags & BasicSymbolRef::SF_Weak) ? STB_WEAK : STB_GLOBAL;
uint8_t Type = ObjSym.isTLS() ? STT_TLS : STT_NOTYPE;
uint8_t Visibility = mapVisibility(ObjSym.getVisibility());
bool CanOmitFromDynSym = ObjSym.canBeOmittedFromSymbolTable();
if (const Comdat *C = check(ObjSym.getComdat()))
if (!KeptComdats.count(C))
return Symtab<ELFT>::X->addUndefined(NameRef, Binding, Visibility, Type,
CanOmitFromDynSym, F);
if (Flags & BasicSymbolRef::SF_Undefined)
return Symtab<ELFT>::X->addUndefined(NameRef, Binding, Visibility, Type,
CanOmitFromDynSym, F);
if (Flags & BasicSymbolRef::SF_Common)
return Symtab<ELFT>::X->addCommon(NameRef, ObjSym.getCommonSize(),
ObjSym.getCommonAlignment(), Binding,
Visibility, STT_OBJECT, F);
return Symtab<ELFT>::X->addBitcode(NameRef, Binding, Visibility, Type,
CanOmitFromDynSym, F);
}
template <class ELFT>
void BitcodeFile::parse(DenseSet<StringRef> &ComdatGroups) {
Obj = check(lto::InputFile::create(MB));
DenseSet<const Comdat *> KeptComdats;
for (const auto &P : Obj->getComdatSymbolTable()) {
StringRef N = Saver.save(P.first());
if (ComdatGroups.insert(N).second)
KeptComdats.insert(&P.second);
}
for (const lto::InputFile::Symbol &ObjSym : Obj->symbols())
Symbols.push_back(
createBitcodeSymbol<ELFT>(KeptComdats, ObjSym, Saver, this));
}
template <template <class> class T>
static InputFile *createELFFile(MemoryBufferRef MB) {
unsigned char Size;
unsigned char Endian;
std::tie(Size, Endian) = getElfArchType(MB.getBuffer());
if (Endian != ELFDATA2LSB && Endian != ELFDATA2MSB)
fatal("invalid data encoding: " + MB.getBufferIdentifier());
InputFile *Obj;
if (Size == ELFCLASS32 && Endian == ELFDATA2LSB)
Obj = new T<ELF32LE>(MB);
else if (Size == ELFCLASS32 && Endian == ELFDATA2MSB)
Obj = new T<ELF32BE>(MB);
else if (Size == ELFCLASS64 && Endian == ELFDATA2LSB)
Obj = new T<ELF64LE>(MB);
else if (Size == ELFCLASS64 && Endian == ELFDATA2MSB)
Obj = new T<ELF64BE>(MB);
else
fatal("invalid file class: " + MB.getBufferIdentifier());
if (!Config->FirstElf)
Config->FirstElf = Obj;
return Obj;
}
// Wraps a binary blob with an ELF header and footer
// so that we can link it as a regular ELF file.
template <class ELFT> InputFile *BinaryFile::createELF() {
// Fill the ELF file header.
ELFCreator<ELFT> ELF(ET_REL, Config->EMachine);
auto DataSec = ELF.addSection(".data");
DataSec.Header->sh_flags = SHF_ALLOC;
DataSec.Header->sh_size = MB.getBufferSize();
DataSec.Header->sh_type = SHT_PROGBITS;
DataSec.Header->sh_addralign = 8;
// Replace non-alphanumeric characters with '_'.
std::string Filepath = MB.getBufferIdentifier();
std::transform(Filepath.begin(), Filepath.end(), Filepath.begin(),
[](char C) { return isalnum(C) ? C : '_'; });
// Add _start, _end and _size symbols.
std::string StartSym = "_binary_" + Filepath + "_start";
auto SSym = ELF.addSymbol(StartSym);
SSym.Sym->setBindingAndType(STB_GLOBAL, STT_OBJECT);
SSym.Sym->st_shndx = DataSec.Index;
std::string EndSym = "_binary_" + Filepath + "_end";
auto ESym = ELF.addSymbol(EndSym);
ESym.Sym->setBindingAndType(STB_GLOBAL, STT_OBJECT);
ESym.Sym->st_shndx = DataSec.Index;
ESym.Sym->st_value = MB.getBufferSize();
std::string SizeSym = "_binary_" + Filepath + "_size";
auto SZSym = ELF.addSymbol(SizeSym);
SZSym.Sym->setBindingAndType(STB_GLOBAL, STT_OBJECT);
SZSym.Sym->st_shndx = SHN_ABS;
SZSym.Sym->st_value = MB.getBufferSize();
// Fix the ELF file layout and write it down to ELFData uint8_t vector.
std::size_t Size = ELF.layout();
ELFData.resize(Size);
ELF.write(ELFData.data());
// Fill .data section with actual data.
std::copy(MB.getBufferStart(), MB.getBufferEnd(),
ELFData.data() + DataSec.Header->sh_offset);
return createELFFile<ObjectFile>(MemoryBufferRef(
StringRef((char *)ELFData.data(), Size), MB.getBufferIdentifier()));
}
static bool isBitcode(MemoryBufferRef MB) {
using namespace sys::fs;
return identify_magic(MB.getBuffer()) == file_magic::bitcode;
}
InputFile *elf::createObjectFile(MemoryBufferRef MB, StringRef ArchiveName) {
InputFile *F =
isBitcode(MB) ? new BitcodeFile(MB) : createELFFile<ObjectFile>(MB);
F->ArchiveName = ArchiveName;
return F;
}
InputFile *elf::createSharedFile(MemoryBufferRef MB) {
return createELFFile<SharedFile>(MB);
}
MemoryBufferRef LazyObjectFile::getBuffer() {
if (Seen)
return MemoryBufferRef();
Seen = true;
return MB;
}
template <class ELFT>
void LazyObjectFile::parse() {
for (StringRef Sym : getSymbols())
Symtab<ELFT>::X->addLazyObject(Sym, *this);
}
template <class ELFT> std::vector<StringRef> LazyObjectFile::getElfSymbols() {
typedef typename ELFT::Shdr Elf_Shdr;
typedef typename ELFT::Sym Elf_Sym;
typedef typename ELFT::SymRange Elf_Sym_Range;
const ELFFile<ELFT> Obj = createELFObj<ELFT>(this->MB);
for (const Elf_Shdr &Sec : Obj.sections()) {
if (Sec.sh_type != SHT_SYMTAB)
continue;
Elf_Sym_Range Syms = Obj.symbols(&Sec);
uint32_t FirstNonLocal = Sec.sh_info;
StringRef StringTable = check(Obj.getStringTableForSymtab(Sec));
std::vector<StringRef> V;
for (const Elf_Sym &Sym : Syms.slice(FirstNonLocal))
if (Sym.st_shndx != SHN_UNDEF)
V.push_back(check(Sym.getName(StringTable)));
return V;
}
return {};
}
std::vector<StringRef> LazyObjectFile::getBitcodeSymbols() {
std::unique_ptr<lto::InputFile> Obj = check(lto::InputFile::create(this->MB));
std::vector<StringRef> V;
for (const lto::InputFile::Symbol &Sym : Obj->symbols())
if (!(Sym.getFlags() & BasicSymbolRef::SF_Undefined))
V.push_back(Saver.save(Sym.getName()));
return V;
}
// Returns a vector of globally-visible defined symbol names.
std::vector<StringRef> LazyObjectFile::getSymbols() {
if (isBitcode(this->MB))
return getBitcodeSymbols();
unsigned char Size;
unsigned char Endian;
std::tie(Size, Endian) = getElfArchType(this->MB.getBuffer());
if (Size == ELFCLASS32) {
if (Endian == ELFDATA2LSB)
return getElfSymbols<ELF32LE>();
return getElfSymbols<ELF32BE>();
}
if (Endian == ELFDATA2LSB)
return getElfSymbols<ELF64LE>();
return getElfSymbols<ELF64BE>();
}
template void ArchiveFile::parse<ELF32LE>();
template void ArchiveFile::parse<ELF32BE>();
template void ArchiveFile::parse<ELF64LE>();
template void ArchiveFile::parse<ELF64BE>();
template void BitcodeFile::parse<ELF32LE>(DenseSet<StringRef> &);
template void BitcodeFile::parse<ELF32BE>(DenseSet<StringRef> &);
template void BitcodeFile::parse<ELF64LE>(DenseSet<StringRef> &);
template void BitcodeFile::parse<ELF64BE>(DenseSet<StringRef> &);
template void LazyObjectFile::parse<ELF32LE>();
template void LazyObjectFile::parse<ELF32BE>();
template void LazyObjectFile::parse<ELF64LE>();
template void LazyObjectFile::parse<ELF64BE>();
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>;
template InputFile *BinaryFile::createELF<ELF32LE>();
template InputFile *BinaryFile::createELF<ELF32BE>();
template InputFile *BinaryFile::createELF<ELF64LE>();
template InputFile *BinaryFile::createELF<ELF64BE>();
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