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llvm-project/lld/lib/ReaderWriter/ELF/SectionChunks.cpp

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//===- lib/ReaderWriter/ELF/SectionChunks.h -------------------------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "SectionChunks.h"
#include "TargetLayout.h"
#include "lld/Core/Parallel.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/Support/Dwarf.h"
namespace lld {
namespace elf {
template <class ELFT>
Section<ELFT>::Section(const ELFLinkingContext &ctx, StringRef sectionName,
StringRef chunkName, typename Chunk<ELFT>::Kind k)
: Chunk<ELFT>(chunkName, k, ctx), _inputSectionName(sectionName),
_outputSectionName(sectionName) {}
template <class ELFT> int Section<ELFT>::getContentType() const {
if (_flags & llvm::ELF::SHF_EXECINSTR)
return Chunk<ELFT>::ContentType::Code;
else if (_flags & llvm::ELF::SHF_WRITE)
return Chunk<ELFT>::ContentType::Data;
else if (_flags & llvm::ELF::SHF_ALLOC)
return Chunk<ELFT>::ContentType::Code;
else
return Chunk<ELFT>::ContentType::Unknown;
}
template <class ELFT>
AtomSection<ELFT>::AtomSection(const ELFLinkingContext &ctx,
StringRef sectionName, int32_t contentType,
int32_t permissions, int32_t order)
: Section<ELFT>(ctx, sectionName, "AtomSection",
Chunk<ELFT>::Kind::AtomSection),
_contentType(contentType), _contentPermissions(permissions) {
this->setOrder(order);
switch (contentType) {
case DefinedAtom::typeCode:
case DefinedAtom::typeDataFast:
case DefinedAtom::typeData:
case DefinedAtom::typeConstant:
case DefinedAtom::typeGOT:
case DefinedAtom::typeStub:
case DefinedAtom::typeResolver:
case DefinedAtom::typeThreadData:
this->_type = SHT_PROGBITS;
break;
case DefinedAtom::typeThreadZeroFill:
case DefinedAtom::typeZeroFillFast:
case DefinedAtom::typeZeroFill:
this->_type = SHT_NOBITS;
break;
case DefinedAtom::typeRONote:
case DefinedAtom::typeRWNote:
this->_type = SHT_NOTE;
break;
case DefinedAtom::typeNoAlloc:
this->_type = SHT_PROGBITS;
this->_isLoadedInMemory = false;
break;
}
switch (permissions) {
case DefinedAtom::permR__:
this->_flags = SHF_ALLOC;
break;
case DefinedAtom::permR_X:
this->_flags = SHF_ALLOC | SHF_EXECINSTR;
break;
case DefinedAtom::permRW_:
case DefinedAtom::permRW_L:
this->_flags = SHF_ALLOC | SHF_WRITE;
if (_contentType == DefinedAtom::typeThreadData ||
_contentType == DefinedAtom::typeThreadZeroFill)
this->_flags |= SHF_TLS;
break;
case DefinedAtom::permRWX:
this->_flags = SHF_ALLOC | SHF_WRITE | SHF_EXECINSTR;
break;
case DefinedAtom::perm___:
this->_flags = 0;
break;
}
}
template <class ELFT>
void AtomSection<ELFT>::assignVirtualAddress(uint64_t addr) {
parallel_for_each(_atoms.begin(), _atoms.end(), [&](AtomLayout *ai) {
ai->_virtualAddr = addr + ai->_fileOffset;
});
}
template <class ELFT>
void AtomSection<ELFT>::assignFileOffsets(uint64_t offset) {
parallel_for_each(_atoms.begin(), _atoms.end(), [&](AtomLayout *ai) {
ai->_fileOffset = offset + ai->_fileOffset;
});
}
template <class ELFT>
const AtomLayout *
AtomSection<ELFT>::findAtomLayoutByName(StringRef name) const {
for (auto ai : _atoms)
if (ai->_atom->name() == name)
return ai;
return nullptr;
}
template <class ELFT>
void AtomSection<ELFT>::printError(const std::string &errorStr,
const AtomLayout &atom,
const Reference &ref) const {
StringRef kindValStr;
if (!this->_ctx.registry().referenceKindToString(
ref.kindNamespace(), ref.kindArch(), ref.kindValue(), kindValStr)) {
kindValStr = "unknown";
}
std::string errStr =
(Twine(errorStr) + " in file " + atom._atom->file().path() +
": reference from " + atom._atom->name() + "+" +
Twine(ref.offsetInAtom()) + " to " + ref.target()->name() + "+" +
Twine(ref.addend()) + " of type " + Twine(ref.kindValue()) + " (" +
kindValStr + ")\n")
.str();
// Take the lock to prevent output getting interleaved between threads
std::lock_guard<std::mutex> lock(_outputMutex);
llvm::errs() << errStr;
}
/// Align the offset to the required modulus defined by the atom alignment
template <class ELFT>
uint64_t AtomSection<ELFT>::alignOffset(uint64_t offset,
DefinedAtom::Alignment &atomAlign) {
uint64_t requiredModulus = atomAlign.modulus;
uint64_t alignment = atomAlign.value;
uint64_t currentModulus = (offset % alignment);
uint64_t retOffset = offset;
if (currentModulus != requiredModulus) {
if (requiredModulus > currentModulus)
retOffset += requiredModulus - currentModulus;
else
retOffset += alignment + requiredModulus - currentModulus;
}
return retOffset;
}
// \brief Append an atom to a Section. The atom gets pushed into a vector
// contains the atom, the atom file offset, the atom virtual address
// the atom file offset is aligned appropriately as set by the Reader
template <class ELFT>
const AtomLayout *AtomSection<ELFT>::appendAtom(const Atom *atom) {
const DefinedAtom *definedAtom = cast<DefinedAtom>(atom);
DefinedAtom::Alignment atomAlign = definedAtom->alignment();
uint64_t alignment = atomAlign.value;
// Align the atom to the required modulus/ align the file offset and the
// memory offset separately this is required so that BSS symbols are handled
// properly as the BSS symbols only occupy memory size and not file size
uint64_t fOffset = alignOffset(this->fileSize(), atomAlign);
uint64_t mOffset = alignOffset(this->memSize(), atomAlign);
switch (definedAtom->contentType()) {
case DefinedAtom::typeCode:
case DefinedAtom::typeConstant:
case DefinedAtom::typeData:
case DefinedAtom::typeDataFast:
case DefinedAtom::typeZeroFillFast:
case DefinedAtom::typeGOT:
case DefinedAtom::typeStub:
case DefinedAtom::typeResolver:
case DefinedAtom::typeThreadData:
case DefinedAtom::typeRONote:
case DefinedAtom::typeRWNote:
_atoms.push_back(new (_alloc) AtomLayout(atom, fOffset, 0));
this->_fsize = fOffset + definedAtom->size();
this->_msize = mOffset + definedAtom->size();
DEBUG_WITH_TYPE("Section", llvm::dbgs()
<< "[" << this->name() << " " << this << "] "
<< "Adding atom: " << atom->name() << "@"
<< fOffset << "\n");
break;
case DefinedAtom::typeNoAlloc:
_atoms.push_back(new (_alloc) AtomLayout(atom, fOffset, 0));
this->_fsize = fOffset + definedAtom->size();
DEBUG_WITH_TYPE("Section", llvm::dbgs()
<< "[" << this->name() << " " << this << "] "
<< "Adding atom: " << atom->name() << "@"
<< fOffset << "\n");
break;
case DefinedAtom::typeThreadZeroFill:
case DefinedAtom::typeZeroFill:
_atoms.push_back(new (_alloc) AtomLayout(atom, mOffset, 0));
this->_msize = mOffset + definedAtom->size();
break;
default:
llvm::dbgs() << definedAtom->contentType() << "\n";
llvm_unreachable("Uexpected content type.");
}
// Set the section alignment to the largest alignment
// std::max doesn't support uint64_t
if (this->_alignment < alignment)
this->_alignment = alignment;
if (_atoms.size())
return _atoms.back();
return nullptr;
}
/// \brief convert the segment type to a String for diagnostics
/// and printing purposes
template <class ELFT> StringRef Section<ELFT>::segmentKindToStr() const {
switch (_segmentType) {
case llvm::ELF::PT_DYNAMIC:
return "DYNAMIC";
case llvm::ELF::PT_INTERP:
return "INTERP";
case llvm::ELF::PT_LOAD:
return "LOAD";
case llvm::ELF::PT_GNU_EH_FRAME:
return "EH_FRAME";
case llvm::ELF::PT_GNU_RELRO:
return "GNU_RELRO";
case llvm::ELF::PT_NOTE:
return "NOTE";
case llvm::ELF::PT_NULL:
return "NULL";
case llvm::ELF::PT_TLS:
return "TLS";
default:
return "UNKNOWN";
}
}
/// \brief Write the section and the atom contents to the buffer
template <class ELFT>
void AtomSection<ELFT>::write(ELFWriter *writer, TargetLayout<ELFT> &layout,
llvm::FileOutputBuffer &buffer) {
uint8_t *chunkBuffer = buffer.getBufferStart();
bool success = true;
parallel_for_each(_atoms.begin(), _atoms.end(), [&](AtomLayout *ai) {
DEBUG_WITH_TYPE("Section", llvm::dbgs()
<< "Writing atom: " << ai->_atom->name()
<< " | " << ai->_fileOffset << "\n");
const DefinedAtom *definedAtom = cast<DefinedAtom>(ai->_atom);
if (!definedAtom->occupiesDiskSpace())
return;
// Copy raw content of atom to file buffer.
ArrayRef<uint8_t> content = definedAtom->rawContent();
uint64_t contentSize = content.size();
if (contentSize == 0)
return;
uint8_t *atomContent = chunkBuffer + ai->_fileOffset;
std::memcpy(atomContent, content.data(), contentSize);
const TargetRelocationHandler &relHandler =
this->_ctx.getTargetHandler().getRelocationHandler();
for (const auto ref : *definedAtom) {
if (std::error_code ec =
relHandler.applyRelocation(*writer, buffer, *ai, *ref)) {
printError(ec.message(), *ai, *ref);
success = false;
}
}
});
if (!success)
llvm::report_fatal_error("relocating output");
}
template <class ELFT>
void OutputSection<ELFT>::appendSection(Section<ELFT> *section) {
if (section->alignment() > _alignment)
_alignment = section->alignment();
assert(!_link && "Section already has a link!");
_link = section->getLink();
_shInfo = section->getInfo();
_entSize = section->getEntSize();
_type = section->getType();
if (_flags < section->getFlags())
_flags = section->getFlags();
section->setOutputSection(this, (_sections.size() == 0));
_kind = section->kind();
_sections.push_back(section);
}
template <class ELFT>
StringTable<ELFT>::StringTable(const ELFLinkingContext &ctx, const char *str,
int32_t order, bool dynamic)
: Section<ELFT>(ctx, str, "StringTable") {
// the string table has a NULL entry for which
// add an empty string
_strings.push_back("");
this->_fsize = 1;
this->_alignment = 1;
this->setOrder(order);
this->_type = SHT_STRTAB;
if (dynamic) {
this->_flags = SHF_ALLOC;
this->_msize = this->_fsize;
}
}
template <class ELFT> uint64_t StringTable<ELFT>::addString(StringRef symname) {
if (symname.empty())
return 0;
StringMapTIter stringIter = _stringMap.find(symname);
if (stringIter == _stringMap.end()) {
_strings.push_back(symname);
uint64_t offset = this->_fsize;
this->_fsize += symname.size() + 1;
if (this->_flags & SHF_ALLOC)
this->_msize = this->_fsize;
_stringMap[symname] = offset;
return offset;
}
return stringIter->second;
}
template <class ELFT>
void StringTable<ELFT>::write(ELFWriter *writer, TargetLayout<ELFT> &,
llvm::FileOutputBuffer &buffer) {
uint8_t *chunkBuffer = buffer.getBufferStart();
uint8_t *dest = chunkBuffer + this->fileOffset();
for (auto si : _strings) {
memcpy(dest, si.data(), si.size());
dest += si.size();
memcpy(dest, "", 1);
dest += 1;
}
}
/// ELF Symbol Table
template <class ELFT>
SymbolTable<ELFT>::SymbolTable(const ELFLinkingContext &ctx, const char *str,
int32_t order)
: Section<ELFT>(ctx, str, "SymbolTable") {
this->setOrder(order);
Elf_Sym symbol;
std::memset(&symbol, 0, sizeof(Elf_Sym));
_symbolTable.push_back(SymbolEntry(nullptr, symbol, nullptr));
this->_entSize = sizeof(Elf_Sym);
this->_fsize = sizeof(Elf_Sym);
this->_alignment = sizeof(Elf_Addr);
this->_type = SHT_SYMTAB;
}
template <class ELFT>
void SymbolTable<ELFT>::addDefinedAtom(Elf_Sym &sym, const DefinedAtom *da,
int64_t addr) {
unsigned char binding = 0, type = 0;
sym.st_size = da->size();
DefinedAtom::ContentType ct;
switch (ct = da->contentType()) {
case DefinedAtom::typeCode:
case DefinedAtom::typeStub:
sym.st_value = addr;
type = llvm::ELF::STT_FUNC;
break;
case DefinedAtom::typeResolver:
sym.st_value = addr;
type = llvm::ELF::STT_GNU_IFUNC;
break;
case DefinedAtom::typeDataFast:
case DefinedAtom::typeData:
case DefinedAtom::typeConstant:
sym.st_value = addr;
type = llvm::ELF::STT_OBJECT;
break;
case DefinedAtom::typeGOT:
sym.st_value = addr;
type = llvm::ELF::STT_NOTYPE;
break;
case DefinedAtom::typeZeroFill:
case DefinedAtom::typeZeroFillFast:
type = llvm::ELF::STT_OBJECT;
sym.st_value = addr;
break;
case DefinedAtom::typeThreadData:
case DefinedAtom::typeThreadZeroFill:
type = llvm::ELF::STT_TLS;
sym.st_value = addr;
break;
default:
type = llvm::ELF::STT_NOTYPE;
}
if (da->customSectionName() == da->name())
type = llvm::ELF::STT_SECTION;
if (da->scope() == DefinedAtom::scopeTranslationUnit)
binding = llvm::ELF::STB_LOCAL;
else
binding = llvm::ELF::STB_GLOBAL;
sym.setBindingAndType(binding, type);
}
template <class ELFT>
void SymbolTable<ELFT>::addAbsoluteAtom(Elf_Sym &sym, const AbsoluteAtom *aa,
int64_t addr) {
unsigned char binding = 0, type = 0;
type = llvm::ELF::STT_OBJECT;
sym.st_shndx = llvm::ELF::SHN_ABS;
switch (aa->scope()) {
case AbsoluteAtom::scopeLinkageUnit:
sym.setVisibility(llvm::ELF::STV_HIDDEN);
binding = llvm::ELF::STB_LOCAL;
break;
case AbsoluteAtom::scopeTranslationUnit:
binding = llvm::ELF::STB_LOCAL;
break;
case AbsoluteAtom::scopeGlobal:
binding = llvm::ELF::STB_GLOBAL;
break;
}
sym.st_value = addr;
sym.setBindingAndType(binding, type);
}
template <class ELFT>
void SymbolTable<ELFT>::addSharedLibAtom(Elf_Sym &sym,
const SharedLibraryAtom *aa) {
unsigned char binding = 0, type = 0;
if (aa->type() == SharedLibraryAtom::Type::Data) {
type = llvm::ELF::STT_OBJECT;
sym.st_size = aa->size();
} else
type = llvm::ELF::STT_FUNC;
sym.st_shndx = llvm::ELF::SHN_UNDEF;
binding = llvm::ELF::STB_GLOBAL;
sym.setBindingAndType(binding, type);
}
template <class ELFT>
void SymbolTable<ELFT>::addUndefinedAtom(Elf_Sym &sym,
const UndefinedAtom *ua) {
unsigned char binding = 0, type = 0;
sym.st_value = 0;
type = llvm::ELF::STT_NOTYPE;
if (ua->canBeNull())
binding = llvm::ELF::STB_WEAK;
else
binding = llvm::ELF::STB_GLOBAL;
sym.setBindingAndType(binding, type);
}
/// Add a symbol to the symbol Table, definedAtoms which get added to the symbol
/// section don't have their virtual addresses set at the time of adding the
/// symbol to the symbol table(Example: dynamic symbols), the addresses needs
/// to be updated in the table before writing the dynamic symbol table
/// information
template <class ELFT>
void SymbolTable<ELFT>::addSymbol(const Atom *atom, int32_t sectionIndex,
uint64_t addr, const AtomLayout *atomLayout) {
Elf_Sym symbol;
if (atom->name().empty())
return;
symbol.st_name = _stringSection->addString(atom->name());
symbol.st_size = 0;
symbol.st_shndx = sectionIndex;
symbol.st_value = 0;
symbol.st_other = 0;
symbol.setVisibility(llvm::ELF::STV_DEFAULT);
// Add all the atoms
if (const DefinedAtom *da = dyn_cast<const DefinedAtom>(atom))
addDefinedAtom(symbol, da, addr);
else if (const AbsoluteAtom *aa = dyn_cast<const AbsoluteAtom>(atom))
addAbsoluteAtom(symbol, aa, addr);
else if (isa<const SharedLibraryAtom>(atom))
addSharedLibAtom(symbol, dyn_cast<SharedLibraryAtom>(atom));
else
addUndefinedAtom(symbol, dyn_cast<UndefinedAtom>(atom));
// If --discard-all is on, don't add to the symbol table
// symbols with local binding.
if (this->_ctx.discardLocals() && symbol.getBinding() == llvm::ELF::STB_LOCAL)
return;
// Temporary locals are all the symbols which name starts with .L.
// This is defined by the ELF standard.
if (this->_ctx.discardTempLocals() && atom->name().startswith(".L"))
return;
_symbolTable.push_back(SymbolEntry(atom, symbol, atomLayout));
this->_fsize += sizeof(Elf_Sym);
if (this->_flags & SHF_ALLOC)
this->_msize = this->_fsize;
}
template <class ELFT> void SymbolTable<ELFT>::finalize(bool sort) {
// sh_info should be one greater than last symbol with STB_LOCAL binding
// we sort the symbol table to keep all local symbols at the beginning
if (sort)
sortSymbols();
uint16_t shInfo = 0;
for (const auto &i : _symbolTable) {
if (i._symbol.getBinding() != llvm::ELF::STB_LOCAL)
break;
shInfo++;
}
this->_info = shInfo;
this->_link = _stringSection->ordinal();
if (this->_outputSection) {
this->_outputSection->setInfo(this->_info);
this->_outputSection->setLink(this->_link);
}
}
template <class ELFT>
void SymbolTable<ELFT>::write(ELFWriter *writer, TargetLayout<ELFT> &,
llvm::FileOutputBuffer &buffer) {
uint8_t *chunkBuffer = buffer.getBufferStart();
uint8_t *dest = chunkBuffer + this->fileOffset();
for (const auto &sti : _symbolTable) {
memcpy(dest, &sti._symbol, sizeof(Elf_Sym));
dest += sizeof(Elf_Sym);
}
}
template <class ELFT>
DynamicSymbolTable<ELFT>::DynamicSymbolTable(const ELFLinkingContext &ctx,
TargetLayout<ELFT> &layout,
const char *str, int32_t order)
: SymbolTable<ELFT>(ctx, str, order), _layout(layout) {
this->_type = SHT_DYNSYM;
this->_flags = SHF_ALLOC;
this->_msize = this->_fsize;
}
template <class ELFT> void DynamicSymbolTable<ELFT>::addSymbolsToHashTable() {
int index = 0;
for (auto &ste : this->_symbolTable) {
if (!ste._atom)
_hashTable->addSymbol("", index);
else
_hashTable->addSymbol(ste._atom->name(), index);
++index;
}
}
template <class ELFT> void DynamicSymbolTable<ELFT>::finalize() {
// Defined symbols which have been added into the dynamic symbol table
// don't have their addresses known until addresses have been assigned
// so let's update the symbol values after they have got assigned
for (auto &ste : this->_symbolTable) {
const AtomLayout *atomLayout = ste._atomLayout;
if (!atomLayout)
continue;
ste._symbol.st_value = atomLayout->_virtualAddr;
}
// Don't sort the symbols
SymbolTable<ELFT>::finalize(false);
}
template <class ELFT>
RelocationTable<ELFT>::RelocationTable(const ELFLinkingContext &ctx,
StringRef str, int32_t order)
: Section<ELFT>(ctx, str, "RelocationTable") {
this->setOrder(order);
this->_flags = SHF_ALLOC;
// Set the alignment properly depending on the target architecture
this->_alignment = ELFT::Is64Bits ? 8 : 4;
if (ctx.isRelaOutputFormat()) {
this->_entSize = sizeof(Elf_Rela);
this->_type = SHT_RELA;
} else {
this->_entSize = sizeof(Elf_Rel);
this->_type = SHT_REL;
}
}
template <class ELFT>
uint32_t RelocationTable<ELFT>::addRelocation(const DefinedAtom &da,
const Reference &r) {
_relocs.emplace_back(&da, &r);
this->_fsize = _relocs.size() * this->_entSize;
this->_msize = this->_fsize;
return _relocs.size() - 1;
}
template <class ELFT>
bool RelocationTable<ELFT>::getRelocationIndex(const Reference &r,
uint32_t &res) {
auto rel = std::find_if(
_relocs.begin(), _relocs.end(),
[&](const std::pair<const DefinedAtom *, const Reference *> &p) {
if (p.second == &r)
return true;
return false;
});
if (rel == _relocs.end())
return false;
res = std::distance(_relocs.begin(), rel);
return true;
}
template <class ELFT>
bool RelocationTable<ELFT>::canModifyReadonlySection() const {
for (const auto &rel : _relocs) {
const DefinedAtom *atom = rel.first;
if ((atom->permissions() & DefinedAtom::permRW_) != DefinedAtom::permRW_)
return true;
}
return false;
}
template <class ELFT> void RelocationTable<ELFT>::finalize() {
this->_link = _symbolTable ? _symbolTable->ordinal() : 0;
if (this->_outputSection)
this->_outputSection->setLink(this->_link);
}
template <class ELFT>
void RelocationTable<ELFT>::write(ELFWriter *writer, TargetLayout<ELFT> &layout,
llvm::FileOutputBuffer &buffer) {
uint8_t *chunkBuffer = buffer.getBufferStart();
uint8_t *dest = chunkBuffer + this->fileOffset();
for (const auto &rel : _relocs) {
if (this->_ctx.isRelaOutputFormat()) {
auto &r = *reinterpret_cast<Elf_Rela *>(dest);
writeRela(writer, r, *rel.first, *rel.second);
DEBUG_WITH_TYPE("ELFRelocationTable",
llvm::dbgs()
<< rel.second->kindValue() << " relocation at "
<< rel.first->name() << "@" << r.r_offset << " to "
<< rel.second->target()->name() << "@" << r.r_addend
<< "\n";);
} else {
auto &r = *reinterpret_cast<Elf_Rel *>(dest);
writeRel(writer, r, *rel.first, *rel.second);
DEBUG_WITH_TYPE("ELFRelocationTable",
llvm::dbgs() << rel.second->kindValue()
<< " relocation at " << rel.first->name()
<< "@" << r.r_offset << " to "
<< rel.second->target()->name() << "\n";);
}
dest += this->_entSize;
}
}
template <class ELFT>
void RelocationTable<ELFT>::writeRela(ELFWriter *writer, Elf_Rela &r,
const DefinedAtom &atom,
const Reference &ref) {
r.setSymbolAndType(getSymbolIndex(ref.target()), ref.kindValue(), false);
r.r_offset = writer->addressOfAtom(&atom) + ref.offsetInAtom();
// The addend is used only by relative relocations
if (this->_ctx.isRelativeReloc(ref))
r.r_addend = writer->addressOfAtom(ref.target()) + ref.addend();
else
r.r_addend = 0;
}
template <class ELFT>
void RelocationTable<ELFT>::writeRel(ELFWriter *writer, Elf_Rel &r,
const DefinedAtom &atom,
const Reference &ref) {
r.setSymbolAndType(getSymbolIndex(ref.target()), ref.kindValue(), false);
r.r_offset = writer->addressOfAtom(&atom) + ref.offsetInAtom();
}
template <class ELFT>
uint32_t RelocationTable<ELFT>::getSymbolIndex(const Atom *a) {
return _symbolTable ? _symbolTable->getSymbolTableIndex(a)
: (uint32_t)STN_UNDEF;
}
template <class ELFT>
DynamicTable<ELFT>::DynamicTable(const ELFLinkingContext &ctx,
TargetLayout<ELFT> &layout, StringRef str,
int32_t order)
: Section<ELFT>(ctx, str, "DynamicSection"), _layout(layout) {
this->setOrder(order);
this->_entSize = sizeof(Elf_Dyn);
this->_alignment = ELFT::Is64Bits ? 8 : 4;
// Reserve space for the DT_NULL entry.
this->_fsize = sizeof(Elf_Dyn);
this->_msize = sizeof(Elf_Dyn);
this->_type = SHT_DYNAMIC;
this->_flags = SHF_ALLOC;
}
template <class ELFT>
std::size_t DynamicTable<ELFT>::addEntry(int64_t tag, uint64_t val) {
Elf_Dyn dyn;
dyn.d_tag = tag;
dyn.d_un.d_val = val;
_entries.push_back(dyn);
this->_fsize = (_entries.size() * sizeof(Elf_Dyn)) + sizeof(Elf_Dyn);
this->_msize = this->_fsize;
return _entries.size() - 1;
}
template <class ELFT>
void DynamicTable<ELFT>::write(ELFWriter *writer, TargetLayout<ELFT> &layout,
llvm::FileOutputBuffer &buffer) {
uint8_t *chunkBuffer = buffer.getBufferStart();
uint8_t *dest = chunkBuffer + this->fileOffset();
// Add the null entry.
Elf_Dyn d;
d.d_tag = 0;
d.d_un.d_val = 0;
_entries.push_back(d);
std::memcpy(dest, _entries.data(), this->_fsize);
}
template <class ELFT> void DynamicTable<ELFT>::createDefaultEntries() {
bool isRela = this->_ctx.isRelaOutputFormat();
_dt_hash = addEntry(DT_HASH, 0);
_dt_strtab = addEntry(DT_STRTAB, 0);
_dt_symtab = addEntry(DT_SYMTAB, 0);
_dt_strsz = addEntry(DT_STRSZ, 0);
_dt_syment = addEntry(DT_SYMENT, 0);
if (_layout.hasDynamicRelocationTable()) {
_dt_rela = addEntry(isRela ? DT_RELA : DT_REL, 0);
_dt_relasz = addEntry(isRela ? DT_RELASZ : DT_RELSZ, 0);
_dt_relaent = addEntry(isRela ? DT_RELAENT : DT_RELENT, 0);
if (_layout.getDynamicRelocationTable()->canModifyReadonlySection())
_dt_textrel = addEntry(DT_TEXTREL, 0);
}
if (_layout.hasPLTRelocationTable()) {
_dt_pltrelsz = addEntry(DT_PLTRELSZ, 0);
_dt_pltgot = addEntry(getGotPltTag(), 0);
_dt_pltrel = addEntry(DT_PLTREL, isRela ? DT_RELA : DT_REL);
_dt_jmprel = addEntry(DT_JMPREL, 0);
}
}
template <class ELFT> void DynamicTable<ELFT>::doPreFlight() {
auto initArray = _layout.findOutputSection(".init_array");
auto finiArray = _layout.findOutputSection(".fini_array");
if (initArray) {
_dt_init_array = addEntry(DT_INIT_ARRAY, 0);
_dt_init_arraysz = addEntry(DT_INIT_ARRAYSZ, 0);
}
if (finiArray) {
_dt_fini_array = addEntry(DT_FINI_ARRAY, 0);
_dt_fini_arraysz = addEntry(DT_FINI_ARRAYSZ, 0);
}
if (getInitAtomLayout())
_dt_init = addEntry(DT_INIT, 0);
if (getFiniAtomLayout())
_dt_fini = addEntry(DT_FINI, 0);
}
template <class ELFT> void DynamicTable<ELFT>::finalize() {
StringTable<ELFT> *dynamicStringTable = _dynamicSymbolTable->getStringTable();
this->_link = dynamicStringTable->ordinal();
if (this->_outputSection) {
this->_outputSection->setType(this->_type);
this->_outputSection->setInfo(this->_info);
this->_outputSection->setLink(this->_link);
}
}
template <class ELFT> void DynamicTable<ELFT>::updateDynamicTable() {
StringTable<ELFT> *dynamicStringTable = _dynamicSymbolTable->getStringTable();
_entries[_dt_hash].d_un.d_val = _hashTable->virtualAddr();
_entries[_dt_strtab].d_un.d_val = dynamicStringTable->virtualAddr();
_entries[_dt_symtab].d_un.d_val = _dynamicSymbolTable->virtualAddr();
_entries[_dt_strsz].d_un.d_val = dynamicStringTable->memSize();
_entries[_dt_syment].d_un.d_val = _dynamicSymbolTable->getEntSize();
auto initArray = _layout.findOutputSection(".init_array");
if (initArray) {
_entries[_dt_init_array].d_un.d_val = initArray->virtualAddr();
_entries[_dt_init_arraysz].d_un.d_val = initArray->memSize();
}
auto finiArray = _layout.findOutputSection(".fini_array");
if (finiArray) {
_entries[_dt_fini_array].d_un.d_val = finiArray->virtualAddr();
_entries[_dt_fini_arraysz].d_un.d_val = finiArray->memSize();
}
if (const auto *al = getInitAtomLayout())
_entries[_dt_init].d_un.d_val = getAtomVirtualAddress(al);
if (const auto *al = getFiniAtomLayout())
_entries[_dt_fini].d_un.d_val = getAtomVirtualAddress(al);
if (_layout.hasDynamicRelocationTable()) {
auto relaTbl = _layout.getDynamicRelocationTable();
_entries[_dt_rela].d_un.d_val = relaTbl->virtualAddr();
_entries[_dt_relasz].d_un.d_val = relaTbl->memSize();
_entries[_dt_relaent].d_un.d_val = relaTbl->getEntSize();
}
if (_layout.hasPLTRelocationTable()) {
auto relaTbl = _layout.getPLTRelocationTable();
_entries[_dt_jmprel].d_un.d_val = relaTbl->virtualAddr();
_entries[_dt_pltrelsz].d_un.d_val = relaTbl->memSize();
auto gotplt = _layout.findOutputSection(".got.plt");
_entries[_dt_pltgot].d_un.d_val = gotplt->virtualAddr();
}
}
template <class ELFT>
const AtomLayout *DynamicTable<ELFT>::getInitAtomLayout() {
auto al = _layout.findAtomLayoutByName(this->_ctx.initFunction());
if (al && isa<DefinedAtom>(al->_atom))
return al;
return nullptr;
}
template <class ELFT>
const AtomLayout *DynamicTable<ELFT>::getFiniAtomLayout() {
auto al = _layout.findAtomLayoutByName(this->_ctx.finiFunction());
if (al && isa<DefinedAtom>(al->_atom))
return al;
return nullptr;
}
template <class ELFT>
InterpSection<ELFT>::InterpSection(const ELFLinkingContext &ctx, StringRef str,
int32_t order, StringRef interp)
: Section<ELFT>(ctx, str, "Dynamic:Interp"), _interp(interp) {
this->setOrder(order);
this->_alignment = 1;
// + 1 for null term.
this->_fsize = interp.size() + 1;
this->_msize = this->_fsize;
this->_type = SHT_PROGBITS;
this->_flags = SHF_ALLOC;
}
template <class ELFT>
void InterpSection<ELFT>::write(ELFWriter *writer, TargetLayout<ELFT> &layout,
llvm::FileOutputBuffer &buffer) {
uint8_t *chunkBuffer = buffer.getBufferStart();
uint8_t *dest = chunkBuffer + this->fileOffset();
std::memcpy(dest, _interp.data(), _interp.size());
}
template <class ELFT>
HashSection<ELFT>::HashSection(const ELFLinkingContext &ctx, StringRef name,
int32_t order)
: Section<ELFT>(ctx, name, "Dynamic:Hash") {
this->setOrder(order);
this->_entSize = 4;
this->_type = SHT_HASH;
this->_flags = SHF_ALLOC;
this->_alignment = ELFT::Is64Bits ? 8 : 4;
this->_fsize = 0;
this->_msize = 0;
}
template <class ELFT>
void HashSection<ELFT>::addSymbol(StringRef name, uint32_t index) {
SymbolTableEntry ste;
ste._name = name;
ste._index = index;
_entries.push_back(ste);
}
/// \brief Set the dynamic symbol table
template <class ELFT>
void HashSection<ELFT>::setSymbolTable(
const DynamicSymbolTable<ELFT> *symbolTable) {
_symbolTable = symbolTable;
}
template <class ELFT> void HashSection<ELFT>::doPreFlight() {
// The number of buckets to use for a certain number of symbols.
// If there are less than 3 symbols, 1 bucket will be used. If
// there are less than 17 symbols, 3 buckets will be used, and so
// forth. The bucket numbers are defined by GNU ld. We use the
// same rules here so we generate hash sections with the same
// size as those generated by GNU ld.
uint32_t hashBuckets[] = {1, 3, 17, 37, 67, 97, 131,
197, 263, 521, 1031, 2053, 4099, 8209,
16411, 32771, 65537, 131101, 262147};
int hashBucketsCount = sizeof(hashBuckets) / sizeof(uint32_t);
unsigned int bucketsCount = 0;
unsigned int dynSymCount = _entries.size();
// Get the number of buckes that we want to use
for (int i = 0; i < hashBucketsCount; ++i) {
if (dynSymCount < hashBuckets[i])
break;
bucketsCount = hashBuckets[i];
}
_buckets.resize(bucketsCount);
_chains.resize(_entries.size());
// Create the hash table for the dynamic linker
for (auto ai : _entries) {
unsigned int dynsymIndex = ai._index;
unsigned int bucketpos = llvm::object::elf_hash(ai._name) % bucketsCount;
_chains[dynsymIndex] = _buckets[bucketpos];
_buckets[bucketpos] = dynsymIndex;
}
this->_fsize = (2 + _chains.size() + _buckets.size()) * sizeof(uint32_t);
this->_msize = this->_fsize;
}
template <class ELFT> void HashSection<ELFT>::finalize() {
this->_link = _symbolTable ? _symbolTable->ordinal() : 0;
if (this->_outputSection)
this->_outputSection->setLink(this->_link);
}
template <class ELFT>
void HashSection<ELFT>::write(ELFWriter *writer, TargetLayout<ELFT> &layout,
llvm::FileOutputBuffer &buffer) {
uint8_t *chunkBuffer = buffer.getBufferStart();
uint8_t *dest = chunkBuffer + this->fileOffset();
Elf_Word bucketChainCounts[2];
bucketChainCounts[0] = _buckets.size();
bucketChainCounts[1] = _chains.size();
std::memcpy(dest, bucketChainCounts, sizeof(bucketChainCounts));
dest += sizeof(bucketChainCounts);
// write bucket values
std::memcpy(dest, _buckets.data(), _buckets.size() * sizeof(Elf_Word));
dest += _buckets.size() * sizeof(Elf_Word);
// write chain values
std::memcpy(dest, _chains.data(), _chains.size() * sizeof(Elf_Word));
}
template <class ELFT>
EHFrameHeader<ELFT>::EHFrameHeader(const ELFLinkingContext &ctx, StringRef name,
TargetLayout<ELFT> &layout, int32_t order)
: Section<ELFT>(ctx, name, "EHFrameHeader"), _layout(layout) {
this->setOrder(order);
this->_entSize = 0;
this->_type = SHT_PROGBITS;
this->_flags = SHF_ALLOC;
this->_alignment = ELFT::Is64Bits ? 8 : 4;
// Minimum size for empty .eh_frame_hdr.
this->_fsize = 1 + 1 + 1 + 1 + 4;
this->_msize = this->_fsize;
}
template <class ELFT> void EHFrameHeader<ELFT>::doPreFlight() {
// TODO: Generate a proper binary search table.
}
template <class ELFT> void EHFrameHeader<ELFT>::finalize() {
OutputSection<ELFT> *s = _layout.findOutputSection(".eh_frame");
OutputSection<ELFT> *h = _layout.findOutputSection(".eh_frame_hdr");
if (s && h)
_ehFrameOffset = s->virtualAddr() - (h->virtualAddr() + 4);
}
template <class ELFT>
void EHFrameHeader<ELFT>::write(ELFWriter *writer, TargetLayout<ELFT> &layout,
llvm::FileOutputBuffer &buffer) {
uint8_t *chunkBuffer = buffer.getBufferStart();
uint8_t *dest = chunkBuffer + this->fileOffset();
int pos = 0;
dest[pos++] = 1; // version
dest[pos++] = llvm::dwarf::DW_EH_PE_pcrel |
llvm::dwarf::DW_EH_PE_sdata4; // eh_frame_ptr_enc
dest[pos++] = llvm::dwarf::DW_EH_PE_omit; // fde_count_enc
dest[pos++] = llvm::dwarf::DW_EH_PE_omit; // table_enc
*reinterpret_cast<typename llvm::object::ELFFile<ELFT>::Elf_Sword *>(
dest + pos) = _ehFrameOffset;
}
#define INSTANTIATE(klass) \
template class klass<ELF32LE>; \
template class klass<ELF32BE>; \
template class klass<ELF64LE>; \
template class klass<ELF64BE>
INSTANTIATE(AtomSection);
INSTANTIATE(DynamicSymbolTable);
INSTANTIATE(DynamicTable);
INSTANTIATE(EHFrameHeader);
INSTANTIATE(HashSection);
INSTANTIATE(InterpSection);
INSTANTIATE(OutputSection);
INSTANTIATE(RelocationTable);
INSTANTIATE(Section);
INSTANTIATE(StringTable);
INSTANTIATE(SymbolTable);
} // end namespace elf
} // end namespace lld
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