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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 "Error.h"
#include "InputSection.h"
#include "LinkerScript.h"
#include "Memory.h"
#include "SymbolTable.h"
#include "Symbols.h"
#include "SyntheticSections.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/CodeGen/Analysis.h"
#include "llvm/DebugInfo/DWARF/DWARFContext.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/LTO/LTO.h"
#include "llvm/MC/StringTableBuilder.h"
#include "llvm/Object/ELFObjectFile.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/TarWriter.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;
TarWriter *elf::Tar;
InputFile::InputFile(Kind K, MemoryBufferRef M) : MB(M), FileKind(K) {}
namespace {
// In ELF object file all section addresses are zero. If we have multiple
// .text sections (when using -ffunction-section or comdat group) then
// LLVM DWARF parser will not be able to parse .debug_line correctly, unless
// we assign each section some unique address. This callback method assigns
// each section an address equal to its offset in ELF object file.
class ObjectInfo : public LoadedObjectInfo {
public:
uint64_t getSectionLoadAddress(const object::SectionRef &Sec) const override {
return static_cast<const ELFSectionRef &>(Sec).getOffset();
}
std::unique_ptr<LoadedObjectInfo> clone() const override {
return std::unique_ptr<LoadedObjectInfo>();
}
};
}
Optional<MemoryBufferRef> elf::readFile(StringRef Path) {
log(Path);
auto MBOrErr = MemoryBuffer::getFile(Path);
if (auto EC = MBOrErr.getError()) {
error("cannot open " + Path + ": " + EC.message());
return None;
}
std::unique_ptr<MemoryBuffer> &MB = *MBOrErr;
MemoryBufferRef MBRef = MB->getMemBufferRef();
make<std::unique_ptr<MemoryBuffer>>(std::move(MB)); // take MB ownership
if (Tar)
Tar->append(relativeToRoot(Path), MBRef.getBuffer());
return MBRef;
}
template <class ELFT> void elf::ObjectFile<ELFT>::initializeDwarfLine() {
std::unique_ptr<object::ObjectFile> Obj =
check(object::ObjectFile::createObjectFile(this->MB), toString(this));
ObjectInfo ObjInfo;
DWARFContextInMemory Dwarf(*Obj, &ObjInfo);
DwarfLine.reset(new DWARFDebugLine(&Dwarf.getLineSection().Relocs));
DataExtractor LineData(Dwarf.getLineSection().Data, Config->IsLE,
Config->Wordsize);
// The second parameter is offset in .debug_line section
// for compilation unit (CU) of interest. We have only one
// CU (object file), so offset is always 0.
DwarfLine->getOrParseLineTable(LineData, 0);
}
// Returns source line information for a given offset
// using DWARF debug info.
template <class ELFT>
Optional<DILineInfo> elf::ObjectFile<ELFT>::getDILineInfo(InputSectionBase *S,
uint64_t Offset) {
if (!DwarfLine)
initializeDwarfLine();
// The offset to CU is 0.
const DWARFDebugLine::LineTable *Tbl = DwarfLine->getLineTable(0);
if (!Tbl)
return None;
// Use fake address calcuated by adding section file offset and offset in
// section. See comments for ObjectInfo class.
DILineInfo Info;
Tbl->getFileLineInfoForAddress(
S->getOffsetInFile() + Offset, nullptr,
DILineInfoSpecifier::FileLineInfoKind::AbsoluteFilePath, Info);
if (Info.Line == 0)
return None;
return Info;
}
// Returns source line information for a given offset
// using DWARF debug info.
template <class ELFT>
std::string elf::ObjectFile<ELFT>::getLineInfo(InputSectionBase *S,
uint64_t Offset) {
if (Optional<DILineInfo> Info = getDILineInfo(S, Offset))
return Info->FileName + ":" + std::to_string(Info->Line);
return "";
}
// Returns "<internal>", "foo.a(bar.o)" or "baz.o".
std::string lld::toString(const InputFile *F) {
if (!F)
return "<internal>";
if (F->ToStringCache.empty()) {
if (F->ArchiveName.empty())
F->ToStringCache = F->getName();
else
F->ToStringCache = (F->ArchiveName + "(" + F->getName() + ")").str();
}
return F->ToStringCache;
}
template <class ELFT>
ELFFileBase<ELFT>::ELFFileBase(Kind K, MemoryBufferRef MB) : InputFile(K, MB) {
if (ELFT::TargetEndianness == support::little)
EKind = ELFT::Is64Bits ? ELF64LEKind : ELF32LEKind;
else
EKind = ELFT::Is64Bits ? ELF64BEKind : ELF32BEKind;
EMachine = getObj().getHeader()->e_machine;
OSABI = getObj().getHeader()->e_ident[llvm::ELF::EI_OSABI];
}
template <class ELFT>
typename ELFT::SymRange ELFFileBase<ELFT>::getGlobalSymbols() {
return makeArrayRef(Symbols.begin() + FirstNonLocal, Symbols.end());
}
template <class ELFT>
uint32_t ELFFileBase<ELFT>::getSectionIndex(const Elf_Sym &Sym) const {
return check(getObj().getSectionIndex(&Sym, Symbols, SymtabSHNDX),
toString(this));
}
template <class ELFT>
void ELFFileBase<ELFT>::initSymtab(ArrayRef<Elf_Shdr> Sections,
const Elf_Shdr *Symtab) {
FirstNonLocal = Symtab->sh_info;
Symbols = check(getObj().symbols(Symtab), toString(this));
if (FirstNonLocal == 0 || FirstNonLocal > Symbols.size())
fatal(toString(this) + ": invalid sh_info in symbol table");
StringTable = check(getObj().getStringTableForSymtab(*Symtab, Sections),
toString(this));
}
template <class ELFT>
elf::ObjectFile<ELFT>::ObjectFile(MemoryBufferRef M, StringRef ArchiveName)
: ELFFileBase<ELFT>(Base::ObjectKind, M) {
this->ArchiveName = ArchiveName;
}
template <class ELFT>
ArrayRef<SymbolBody *> elf::ObjectFile<ELFT>::getLocalSymbols() {
if (this->SymbolBodies.empty())
return this->SymbolBodies;
return makeArrayRef(this->SymbolBodies).slice(1, this->FirstNonLocal - 1);
}
template <class ELFT>
ArrayRef<SymbolBody *> elf::ObjectFile<ELFT>::getSymbols() {
if (this->SymbolBodies.empty())
return this->SymbolBodies;
return makeArrayRef(this->SymbolBodies).slice(1);
}
template <class ELFT>
void elf::ObjectFile<ELFT>::parse(DenseSet<CachedHashStringRef> &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(ArrayRef<Elf_Shdr> Sections,
const Elf_Shdr &Sec) {
if (this->Symbols.empty())
this->initSymtab(
Sections,
check(object::getSection<ELFT>(Sections, Sec.sh_link), toString(this)));
const Elf_Sym *Sym = check(
object::getSymbol<ELFT>(this->Symbols, Sec.sh_info), toString(this));
return check(Sym->getName(this->StringTable), toString(this));
}
template <class ELFT>
ArrayRef<typename elf::ObjectFile<ELFT>::Elf_Word>
elf::ObjectFile<ELFT>::getShtGroupEntries(const Elf_Shdr &Sec) {
const ELFFile<ELFT> &Obj = this->getObj();
ArrayRef<Elf_Word> Entries = check(
Obj.template getSectionContentsAsArray<Elf_Word>(&Sec), toString(this));
if (Entries.empty() || Entries[0] != GRP_COMDAT)
fatal(toString(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;
// Do not merge sections if generating a relocatable object. It makes
// the code simpler because we do not need to update relocation addends
// to reflect changes introduced by merging. Instead of that we write
// such "merge" sections into separate OutputSections and keep SHF_MERGE
// / SHF_STRINGS flags and sh_entsize value to be able to perform merging
// later during a final linking.
if (Config->Relocatable)
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.
uint64_t EntSize = Sec.sh_entsize;
if (EntSize == 0)
return false;
if (Sec.sh_size % EntSize)
fatal(toString(this) +
": SHF_MERGE section size must be a multiple of sh_entsize");
uint64_t Flags = Sec.sh_flags;
if (!(Flags & SHF_MERGE))
return false;
if (Flags & SHF_WRITE)
fatal(toString(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<CachedHashStringRef> &ComdatGroups) {
ArrayRef<Elf_Shdr> ObjSections =
check(this->getObj().sections(), toString(this));
const ELFFile<ELFT> &Obj = this->getObj();
uint64_t Size = ObjSections.size();
this->Sections.resize(Size);
unsigned I = -1;
StringRef SectionStringTable =
check(Obj.getSectionStringTable(ObjSections), toString(this));
for (const Elf_Shdr &Sec : ObjSections) {
++I;
if (this->Sections[I] == &InputSection::Discarded)
continue;
// SHF_EXCLUDE'ed sections are discarded by the linker. However,
// if -r is given, we'll let the final link discard such sections.
// This is compatible with GNU.
if ((Sec.sh_flags & SHF_EXCLUDE) && !Config->Relocatable) {
this->Sections[I] = &InputSection::Discarded;
continue;
}
switch (Sec.sh_type) {
case SHT_GROUP:
this->Sections[I] = &InputSection::Discarded;
if (ComdatGroups
.insert(
CachedHashStringRef(getShtGroupSignature(ObjSections, Sec)))
.second)
continue;
for (uint32_t SecIndex : getShtGroupEntries(Sec)) {
if (SecIndex >= Size)
fatal(toString(this) +
": invalid section index in group: " + Twine(SecIndex));
this->Sections[SecIndex] = &InputSection::Discarded;
}
break;
case SHT_SYMTAB:
this->initSymtab(ObjSections, &Sec);
break;
case SHT_SYMTAB_SHNDX:
this->SymtabSHNDX =
check(Obj.getSHNDXTable(Sec, ObjSections), toString(this));
break;
case SHT_STRTAB:
case SHT_NULL:
break;
default:
this->Sections[I] = createInputSection(Sec, SectionStringTable);
}
// .ARM.exidx sections have a reverse dependency on the InputSection they
// have a SHF_LINK_ORDER dependency, this is identified by the sh_link.
if (Sec.sh_flags & SHF_LINK_ORDER) {
if (Sec.sh_link >= this->Sections.size())
fatal(toString(this) + ": invalid sh_link index: " +
Twine(Sec.sh_link));
this->Sections[Sec.sh_link]->DependentSections.push_back(
this->Sections[I]);
}
}
}
template <class ELFT>
InputSectionBase *elf::ObjectFile<ELFT>::getRelocTarget(const Elf_Shdr &Sec) {
uint32_t Idx = Sec.sh_info;
if (Idx >= this->Sections.size())
fatal(toString(this) + ": invalid relocated section index: " + Twine(Idx));
InputSectionBase *Target = this->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::Discarded)
return nullptr;
if (!Target)
fatal(toString(this) + ": unsupported relocation reference");
return Target;
}
// Create a regular InputSection class that has the same contents
// as a given section.
InputSectionBase *toRegularSection(MergeInputSection *Sec) {
auto *Ret = make<InputSection>(Sec->Flags, Sec->Type, Sec->Alignment,
Sec->Data, Sec->Name);
Ret->File = Sec->File;
return Ret;
}
template <class ELFT>
InputSectionBase *
elf::ObjectFile<ELFT>::createInputSection(const Elf_Shdr &Sec,
StringRef SectionStringTable) {
StringRef Name = check(
this->getObj().getSectionName(&Sec, SectionStringTable), toString(this));
switch (Sec.sh_type) {
case SHT_ARM_ATTRIBUTES:
// FIXME: ARM meta-data section. Retain the first attribute section
// we see. The eglibc ARM dynamic loaders require the presence of an
// attribute section for dlopen to work.
// In a full implementation we would merge all attribute sections.
if (In<ELFT>::ARMAttributes == nullptr) {
In<ELFT>::ARMAttributes = make<InputSection>(this, &Sec, Name);
return In<ELFT>::ARMAttributes;
}
return &InputSection::Discarded;
case SHT_RELA:
case SHT_REL: {
// Find the relocation target section and associate this
// section with it. Target can be discarded, for example
// if it is a duplicated member of SHT_GROUP section, we
// do not create or proccess relocatable sections then.
InputSectionBase *Target = getRelocTarget(Sec);
if (!Target)
return nullptr;
// 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 make<InputSection>(this, &Sec, Name);
if (Target->FirstRelocation)
fatal(toString(this) +
": multiple relocation sections to one section are not supported");
// Mergeable sections with relocations are tricky because relocations
// need to be taken into account when comparing section contents for
// merging. It's not worth supporting such mergeable sections because
// they are rare and it'd complicates the internal design (we usually
// have to determine if two sections are mergeable early in the link
// process much before applying relocations). We simply handle mergeable
// sections with relocations as non-mergeable.
if (auto *MS = dyn_cast<MergeInputSection>(Target)) {
Target = toRegularSection(MS);
this->Sections[Sec.sh_info] = Target;
}
size_t NumRelocations;
if (Sec.sh_type == SHT_RELA) {
ArrayRef<Elf_Rela> Rels =
check(this->getObj().relas(&Sec), toString(this));
Target->FirstRelocation = Rels.begin();
NumRelocations = Rels.size();
Target->AreRelocsRela = true;
} else {
ArrayRef<Elf_Rel> Rels = check(this->getObj().rels(&Sec), toString(this));
Target->FirstRelocation = Rels.begin();
NumRelocations = Rels.size();
Target->AreRelocsRela = false;
}
assert(isUInt<31>(NumRelocations));
Target->NumRelocations = NumRelocations;
// Relocation sections processed by the linker are usually removed
// from the output, so returning `nullptr` for the normal case.
// However, if -emit-relocs is given, we need to leave them in the output.
// (Some post link analysis tools need this information.)
if (Config->EmitRelocs) {
InputSection *RelocSec = make<InputSection>(this, &Sec, Name);
// We will not emit relocation section if target was discarded.
Target->DependentSections.push_back(RelocSec);
return RelocSec;
}
return nullptr;
}
}
// The GNU linker uses .note.GNU-stack section as a marker indicating
// that the code in the object file does not expect that the stack is
// executable (in terms of NX bit). If all input files have the marker,
// the GNU linker adds a PT_GNU_STACK segment to tells the loader to
// make the stack non-executable. Most object files have this section as
// of 2017.
//
// But making the stack non-executable is a norm today for security
// reasons. Failure to do so may result in a serious security issue.
// Therefore, we make LLD always add PT_GNU_STACK unless it is
// explicitly told to do otherwise (by -z execstack). Because the stack
// executable-ness is controlled solely by command line options,
// .note.GNU-stack sections are simply ignored.
if (Name == ".note.GNU-stack")
return &InputSection::Discarded;
// Split stacks is a feature to support a discontiguous stack. At least
// as of 2017, it seems that the feature is not being used widely.
// Only GNU gold supports that. We don't. For the details about that,
// see https://gcc.gnu.org/wiki/SplitStacks
if (Name == ".note.GNU-split-stack") {
error(toString(this) +
": object file compiled with -fsplit-stack is not supported");
return &InputSection::Discarded;
}
if (Config->Strip != StripPolicy::None && Name.startswith(".debug"))
return &InputSection::Discarded;
// If -gdb-index is given, LLD creates .gdb_index section, and that
// section serves the same purpose as .debug_gnu_pub{names,types} sections.
// If that's the case, we want to eliminate .debug_gnu_pub{names,types}
// because they are redundant and can waste large amount of disk space
// (for example, they are about 400 MiB in total for a clang debug build.)
if (Config->GdbIndex &&
(Name == ".debug_gnu_pubnames" || Name == ".debug_gnu_pubtypes"))
return &InputSection::Discarded;
// The linkonce feature is a sort of proto-comdat. Some glibc i386 object
// files contain definitions of symbol "__x86.get_pc_thunk.bx" in linkonce
// sections. Drop those sections to avoid duplicate symbol errors.
// FIXME: This is glibc PR20543, we should remove this hack once that has been
// fixed for a while.
if (Name.startswith(".gnu.linkonce."))
return &InputSection::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 make<EhInputSection>(this, &Sec, Name);
if (shouldMerge(Sec))
return make<MergeInputSection>(this, &Sec, Name);
return make<InputSection>(this, &Sec, Name);
}
template <class ELFT> void elf::ObjectFile<ELFT>::initializeSymbols() {
SymbolBodies.reserve(this->Symbols.size());
for (const Elf_Sym &Sym : this->Symbols)
SymbolBodies.push_back(createSymbolBody(&Sym));
}
template <class ELFT>
InputSectionBase *elf::ObjectFile<ELFT>::getSection(const Elf_Sym &Sym) const {
uint32_t Index = this->getSectionIndex(Sym);
if (Index >= this->Sections.size())
fatal(toString(this) + ": invalid section index: " + Twine(Index));
InputSectionBase *S = this->Sections[Index];
// We found that GNU assembler 2.17.50 [FreeBSD] 2007-07-03 could
// generate broken objects. STT_SECTION/STT_NOTYPE 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) {
if (Index == 0 || Sym.getType() == STT_SECTION ||
Sym.getType() == STT_NOTYPE)
return nullptr;
fatal(toString(this) + ": invalid section index: " + Twine(Index));
}
if (S == &InputSection::Discarded)
return S;
return S->Repl;
}
template <class ELFT>
SymbolBody *elf::ObjectFile<ELFT>::createSymbolBody(const Elf_Sym *Sym) {
int Binding = Sym->getBinding();
InputSectionBase *Sec = getSection(*Sym);
uint8_t StOther = Sym->st_other;
uint8_t Type = Sym->getType();
uint64_t Value = Sym->st_value;
uint64_t Size = Sym->st_size;
if (Binding == STB_LOCAL) {
if (Sym->getType() == STT_FILE)
SourceFile = check(Sym->getName(this->StringTable), toString(this));
if (this->StringTable.size() <= Sym->st_name)
fatal(toString(this) + ": invalid symbol name offset");
StringRefZ Name = this->StringTable.data() + Sym->st_name;
if (Sym->st_shndx == SHN_UNDEF)
return make<Undefined>(Name, /*IsLocal=*/true, StOther, Type, this);
return make<DefinedRegular>(Name, /*IsLocal=*/true, StOther, Type, Value,
Size, Sec, this);
}
StringRef Name = check(Sym->getName(this->StringTable), toString(this));
switch (Sym->st_shndx) {
case SHN_UNDEF:
return elf::Symtab<ELFT>::X
->addUndefined(Name, /*IsLocal=*/false, Binding, StOther, Type,
/*CanOmitFromDynSym=*/false, this)
->body();
case SHN_COMMON:
if (Value == 0 || Value >= UINT32_MAX)
fatal(toString(this) + ": common symbol '" + Name +
"' has invalid alignment: " + Twine(Value));
return elf::Symtab<ELFT>::X
->addCommon(Name, Size, Value, Binding, StOther, Type, this)
->body();
}
switch (Binding) {
default:
fatal(toString(this) + ": unexpected binding: " + Twine(Binding));
case STB_GLOBAL:
case STB_WEAK:
case STB_GNU_UNIQUE:
if (Sec == &InputSection::Discarded)
return elf::Symtab<ELFT>::X
->addUndefined(Name, /*IsLocal=*/false, Binding, StOther, Type,
/*CanOmitFromDynSym=*/false, this)
->body();
return elf::Symtab<ELFT>::X
->addRegular(Name, StOther, Type, Value, Size, Binding, Sec, this)
->body();
}
}
ArchiveFile::ArchiveFile(std::unique_ptr<Archive> &&File)
: InputFile(ArchiveKind, File->getMemoryBufferRef()),
File(std::move(File)) {}
template <class ELFT> void ArchiveFile::parse() {
for (const Archive::Symbol &Sym : File->symbols())
Symtab<ELFT>::X->addLazyArchive(this, Sym);
}
// Returns a buffer pointing to a member file containing a given symbol.
std::pair<MemoryBufferRef, uint64_t>
ArchiveFile::getMember(const Archive::Symbol *Sym) {
Archive::Child C =
check(Sym->getMember(), toString(this) +
": could not get the member for symbol " +
Sym->getName());
if (!Seen.insert(C.getChildOffset()).second)
return {MemoryBufferRef(), 0};
MemoryBufferRef Ret =
check(C.getMemoryBufferRef(),
toString(this) +
": could not get the buffer for the member defining symbol " +
Sym->getName());
if (C.getParent()->isThin() && Tar)
Tar->append(relativeToRoot(check(C.getFullName(), toString(this))),
Ret.getBuffer());
if (C.getParent()->isThin())
return {Ret, 0};
return {Ret, C.getChildOffset()};
}
template <class ELFT>
SharedFile<ELFT>::SharedFile(MemoryBufferRef M, StringRef DefaultSoName)
: ELFFileBase<ELFT>(Base::SharedKind, M), SoName(DefaultSoName),
AsNeeded(Config->AsNeeded) {}
template <class ELFT>
const typename ELFT::Shdr *
SharedFile<ELFT>::getSection(const Elf_Sym &Sym) const {
return check(
this->getObj().getSection(&Sym, this->Symbols, this->SymtabSHNDX),
toString(this));
}
// Partially parse the shared object file so that we can call
// getSoName on this object.
template <class ELFT> void SharedFile<ELFT>::parseSoName() {
const Elf_Shdr *DynamicSec = nullptr;
const ELFFile<ELFT> Obj = this->getObj();
ArrayRef<Elf_Shdr> Sections = check(Obj.sections(), toString(this));
// Search for .dynsym, .dynamic, .symtab, .gnu.version and .gnu.version_d.
for (const Elf_Shdr &Sec : Sections) {
switch (Sec.sh_type) {
default:
continue;
case SHT_DYNSYM:
this->initSymtab(Sections, &Sec);
break;
case SHT_DYNAMIC:
DynamicSec = &Sec;
break;
case SHT_SYMTAB_SHNDX:
this->SymtabSHNDX =
check(Obj.getSHNDXTable(Sec, Sections), toString(this));
break;
case SHT_GNU_versym:
this->VersymSec = &Sec;
break;
case SHT_GNU_verdef:
this->VerdefSec = &Sec;
break;
}
}
if (this->VersymSec && this->Symbols.empty())
error("SHT_GNU_versym should be associated with symbol table");
// Search for a DT_SONAME tag to initialize this->SoName.
if (!DynamicSec)
return;
ArrayRef<Elf_Dyn> Arr =
check(Obj.template getSectionContentsAsArray<Elf_Dyn>(DynamicSec),
toString(this));
for (const Elf_Dyn &Dyn : Arr) {
if (Dyn.d_tag == DT_SONAME) {
uint64_t Val = Dyn.getVal();
if (Val >= this->StringTable.size())
fatal(toString(this) + ": invalid DT_SONAME entry");
SoName = 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.
const char *Base = this->MB.getBuffer().data();
Versym = reinterpret_cast<const Elf_Versym *>(Base + VersymSec->sh_offset) +
this->FirstNonLocal;
// 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 char *Verdef = 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->getGlobalSymbols();
for (const Elf_Sym &Sym : Syms) {
unsigned VersymIndex = 0;
if (Versym) {
VersymIndex = Versym->vs_index;
++Versym;
}
bool Hidden = VersymIndex & VERSYM_HIDDEN;
VersymIndex = VersymIndex & ~VERSYM_HIDDEN;
StringRef Name = check(Sym.getName(this->StringTable), toString(this));
if (Sym.isUndefined()) {
Undefs.push_back(Name);
continue;
}
// Ignore local symbols.
if (Versym && VersymIndex == VER_NDX_LOCAL)
continue;
const Elf_Verdef *V =
VersymIndex == VER_NDX_GLOBAL ? nullptr : Verdefs[VersymIndex];
if (!Hidden)
elf::Symtab<ELFT>::X->addShared(this, Name, Sym, V);
// Also add the symbol with the versioned name to handle undefined symbols
// with explicit versions.
if (V) {
StringRef VerName = this->StringTable.data() + V->getAux()->vda_name;
Name = Saver.save(Name + "@" + VerName);
elf::Symtab<ELFT>::X->addShared(this, Name, Sym, V);
}
}
}
static ELFKind getBitcodeELFKind(const Triple &T) {
if (T.isLittleEndian())
return T.isArch64Bit() ? ELF64LEKind : ELF32LEKind;
return T.isArch64Bit() ? ELF64BEKind : ELF32BEKind;
}
static uint8_t getBitcodeMachineKind(StringRef Path, const Triple &T) {
switch (T.getArch()) {
case Triple::aarch64:
return EM_AARCH64;
case Triple::arm:
case Triple::thumb:
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(Path + ": could not infer e_machine from bitcode target triple " +
T.str());
}
}
BitcodeFile::BitcodeFile(MemoryBufferRef MB, StringRef ArchiveName,
uint64_t OffsetInArchive)
: InputFile(BitcodeKind, MB) {
this->ArchiveName = ArchiveName;
// Here we pass a new MemoryBufferRef which is identified by ArchiveName
// (the fully resolved path of the archive) + member name + offset of the
// member in the archive.
// ThinLTO uses the MemoryBufferRef identifier to access its internal
// data structures and if two archives define two members with the same name,
// this causes a collision which result in only one of the objects being
// taken into consideration at LTO time (which very likely causes undefined
// symbols later in the link stage).
MemoryBufferRef MBRef(MB.getBuffer(),
Saver.save(ArchiveName + MB.getBufferIdentifier() +
utostr(OffsetInArchive)));
Obj = check(lto::InputFile::create(MBRef), toString(this));
Triple T(Obj->getTargetTriple());
EKind = getBitcodeELFKind(T);
EMachine = getBitcodeMachineKind(MB.getBufferIdentifier(), T);
}
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 std::vector<bool> &KeptComdats,
const lto::InputFile::Symbol &ObjSym,
BitcodeFile *F) {
StringRef NameRef = Saver.save(ObjSym.getName());
uint32_t Binding = ObjSym.isWeak() ? STB_WEAK : STB_GLOBAL;
uint8_t Type = ObjSym.isTLS() ? STT_TLS : STT_NOTYPE;
uint8_t Visibility = mapVisibility(ObjSym.getVisibility());
bool CanOmitFromDynSym = ObjSym.canBeOmittedFromSymbolTable();
int C = ObjSym.getComdatIndex();
if (C != -1 && !KeptComdats[C])
return Symtab<ELFT>::X->addUndefined(NameRef, /*IsLocal=*/false, Binding,
Visibility, Type, CanOmitFromDynSym,
F);
if (ObjSym.isUndefined())
return Symtab<ELFT>::X->addUndefined(NameRef, /*IsLocal=*/false, Binding,
Visibility, Type, CanOmitFromDynSym,
F);
if (ObjSym.isCommon())
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<CachedHashStringRef> &ComdatGroups) {
std::vector<bool> KeptComdats;
for (StringRef S : Obj->getComdatTable())
KeptComdats.push_back(ComdatGroups.insert(CachedHashStringRef(S)).second);
for (const lto::InputFile::Symbol &ObjSym : Obj->symbols())
Symbols.push_back(createBitcodeSymbol<ELFT>(KeptComdats, ObjSym, this));
}
static ELFKind getELFKind(MemoryBufferRef MB) {
unsigned char Size;
unsigned char Endian;
std::tie(Size, Endian) = getElfArchType(MB.getBuffer());
if (Endian != ELFDATA2LSB && Endian != ELFDATA2MSB)
fatal(MB.getBufferIdentifier() + ": invalid data encoding");
if (Size != ELFCLASS32 && Size != ELFCLASS64)
fatal(MB.getBufferIdentifier() + ": invalid file class");
size_t BufSize = MB.getBuffer().size();
if ((Size == ELFCLASS32 && BufSize < sizeof(Elf32_Ehdr)) ||
(Size == ELFCLASS64 && BufSize < sizeof(Elf64_Ehdr)))
fatal(MB.getBufferIdentifier() + ": file is too short");
if (Size == ELFCLASS32)
return (Endian == ELFDATA2LSB) ? ELF32LEKind : ELF32BEKind;
return (Endian == ELFDATA2LSB) ? ELF64LEKind : ELF64BEKind;
}
template <class ELFT> void BinaryFile::parse() {
ArrayRef<uint8_t> Data = toArrayRef(MB.getBuffer());
auto *Section =
make<InputSection>(SHF_ALLOC | SHF_WRITE, SHT_PROGBITS, 8, Data, ".data");
Sections.push_back(Section);
// For each input file foo that is embedded to a result as a binary
// blob, we define _binary_foo_{start,end,size} symbols, so that
// user programs can access blobs by name. Non-alphanumeric
// characters in a filename are replaced with underscore.
std::string S = "_binary_" + MB.getBufferIdentifier().str();
for (size_t I = 0; I < S.size(); ++I)
if (!isalnum(S[I]))
S[I] = '_';
elf::Symtab<ELFT>::X->addRegular(Saver.save(S + "_start"), STV_DEFAULT,
STT_OBJECT, 0, 0, STB_GLOBAL, Section,
nullptr);
elf::Symtab<ELFT>::X->addRegular(Saver.save(S + "_end"), STV_DEFAULT,
STT_OBJECT, Data.size(), 0, STB_GLOBAL,
Section, nullptr);
elf::Symtab<ELFT>::X->addRegular(Saver.save(S + "_size"), STV_DEFAULT,
STT_OBJECT, Data.size(), 0, STB_GLOBAL,
nullptr, nullptr);
}
static bool isBitcode(MemoryBufferRef MB) {
using namespace sys::fs;
return identify_magic(MB.getBuffer()) == file_magic::bitcode;
}
InputFile *elf::createObjectFile(MemoryBufferRef MB, StringRef ArchiveName,
uint64_t OffsetInArchive) {
if (isBitcode(MB))
return make<BitcodeFile>(MB, ArchiveName, OffsetInArchive);
switch (getELFKind(MB)) {
case ELF32LEKind:
return make<ObjectFile<ELF32LE>>(MB, ArchiveName);
case ELF32BEKind:
return make<ObjectFile<ELF32BE>>(MB, ArchiveName);
case ELF64LEKind:
return make<ObjectFile<ELF64LE>>(MB, ArchiveName);
case ELF64BEKind:
return make<ObjectFile<ELF64BE>>(MB, ArchiveName);
default:
llvm_unreachable("getELFKind");
}
}
InputFile *elf::createSharedFile(MemoryBufferRef MB, StringRef DefaultSoName) {
switch (getELFKind(MB)) {
case ELF32LEKind:
return make<SharedFile<ELF32LE>>(MB, DefaultSoName);
case ELF32BEKind:
return make<SharedFile<ELF32BE>>(MB, DefaultSoName);
case ELF64LEKind:
return make<SharedFile<ELF64LE>>(MB, DefaultSoName);
case ELF64BEKind:
return make<SharedFile<ELF64BE>>(MB, DefaultSoName);
default:
llvm_unreachable("getELFKind");
}
}
MemoryBufferRef LazyObjectFile::getBuffer() {
if (Seen)
return MemoryBufferRef();
Seen = true;
return MB;
}
InputFile *LazyObjectFile::fetch() {
MemoryBufferRef MBRef = getBuffer();
if (MBRef.getBuffer().empty())
return nullptr;
return createObjectFile(MBRef, ArchiveName, OffsetInArchive);
}
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(this->MB.getBuffer());
ArrayRef<Elf_Shdr> Sections = check(Obj.sections(), toString(this));
for (const Elf_Shdr &Sec : Sections) {
if (Sec.sh_type != SHT_SYMTAB)
continue;
Elf_Sym_Range Syms = check(Obj.symbols(&Sec), toString(this));
uint32_t FirstNonLocal = Sec.sh_info;
StringRef StringTable =
check(Obj.getStringTableForSymtab(Sec, Sections), toString(this));
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), toString(this)));
return V;
}
return {};
}
std::vector<StringRef> LazyObjectFile::getBitcodeSymbols() {
std::unique_ptr<lto::InputFile> Obj =
check(lto::InputFile::create(this->MB), toString(this));
std::vector<StringRef> V;
for (const lto::InputFile::Symbol &Sym : Obj->symbols())
if (!Sym.isUndefined())
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();
switch (getELFKind(this->MB)) {
case ELF32LEKind:
return getElfSymbols<ELF32LE>();
case ELF32BEKind:
return getElfSymbols<ELF32BE>();
case ELF64LEKind:
return getElfSymbols<ELF64LE>();
case ELF64BEKind:
return getElfSymbols<ELF64BE>();
default:
llvm_unreachable("getELFKind");
}
}
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<CachedHashStringRef> &);
template void BitcodeFile::parse<ELF32BE>(DenseSet<CachedHashStringRef> &);
template void BitcodeFile::parse<ELF64LE>(DenseSet<CachedHashStringRef> &);
template void BitcodeFile::parse<ELF64BE>(DenseSet<CachedHashStringRef> &);
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 void BinaryFile::parse<ELF32LE>();
template void BinaryFile::parse<ELF32BE>();
template void BinaryFile::parse<ELF64LE>();
template void BinaryFile::parse<ELF64BE>();
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