blob: 413871b60cf701cada5ac6402cbdd11eee72157f [file] [log] [blame]
//===- OutputSections.h -----------------------------------------*- C++ -*-===//
// The LLVM Linker
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
#include "Config.h"
#include "InputSection.h"
#include "Relocations.h"
#include "lld/Core/LLVM.h"
#include "llvm/MC/StringTableBuilder.h"
#include "llvm/Object/ELF.h"
namespace lld {
namespace elf {
struct PhdrEntry;
class SymbolBody;
struct EhSectionPiece;
class EhInputSection;
class InputSection;
class InputSectionBase;
class MergeInputSection;
class OutputSection;
template <class ELFT> class ObjectFile;
template <class ELFT> class SharedFile;
class SharedSymbol;
class DefinedRegular;
// This represents a section in an output file.
// It is composed of multiple InputSections.
// The writer creates multiple OutputSections and assign them unique,
// non-overlapping file offsets and VAs.
class OutputSection final : public SectionBase {
OutputSection(StringRef Name, uint32_t Type, uint64_t Flags);
static bool classof(const SectionBase *S) {
return S->kind() == SectionBase::Output;
uint64_t getLMA() const { return Addr + LMAOffset; }
template <typename ELFT> void writeHeaderTo(typename ELFT::Shdr *SHdr);
unsigned SectionIndex;
unsigned SortRank;
uint32_t getPhdrFlags() const;
void updateAlignment(uint32_t Val) {
if (Val > Alignment)
Alignment = Val;
// If true, this section will be page aligned on disk.
// Typically the first section of each PT_LOAD segment has this flag.
bool PageAlign = false;
// Pointer to the first section in PT_LOAD segment, which this section
// also resides in. This field is used to correctly compute file offset
// of a section. When two sections share the same load segment, difference
// between their file offsets should be equal to difference between their
// virtual addresses. To compute some section offset we use the following
// formula: Off = Off_first + VA - VA_first.
OutputSection *FirstInPtLoad = nullptr;
// The following fields correspond to Elf_Shdr members.
uint64_t Size = 0;
uint64_t Offset = 0;
uint64_t LMAOffset = 0;
uint64_t Addr = 0;
uint32_t ShName = 0;
void addSection(InputSection *S);
void sort(std::function<int(InputSectionBase *S)> Order);
void sortInitFini();
void sortCtorsDtors();
uint32_t getFiller();
template <class ELFT> void writeTo(uint8_t *Buf);
template <class ELFT> void finalize();
template <class ELFT> void maybeCompress();
void assignOffsets();
std::vector<InputSection *> Sections;
// Used for implementation of --compress-debug-sections option.
std::vector<uint8_t> ZDebugHeader;
llvm::SmallVector<char, 1> CompressedData;
// Location in the output buffer.
uint8_t *Loc = nullptr;
// All output sections that are handled by the linker specially are
// globally accessible. Writer initializes them, so don't use them
// until Writer is initialized.
struct Out {
static uint8_t First;
static OutputSection *Opd;
static uint8_t *OpdBuf;
static PhdrEntry *TlsPhdr;
static OutputSection *DebugInfo;
static OutputSection *ElfHeader;
static OutputSection *ProgramHeaders;
static OutputSection *PreinitArray;
static OutputSection *InitArray;
static OutputSection *FiniArray;
struct SectionKey {
StringRef Name;
uint64_t Flags;
uint32_t Alignment;
namespace llvm {
template <> struct DenseMapInfo<lld::elf::SectionKey> {
static lld::elf::SectionKey getEmptyKey();
static lld::elf::SectionKey getTombstoneKey();
static unsigned getHashValue(const lld::elf::SectionKey &Val);
static bool isEqual(const lld::elf::SectionKey &LHS,
const lld::elf::SectionKey &RHS);
namespace lld {
namespace elf {
// This class knows how to create an output section for a given
// input section. Output section type is determined by various
// factors, including input section's sh_flags, sh_type and
// linker scripts.
class OutputSectionFactory {
OutputSectionFactory(std::vector<OutputSection *> &OutputSections);
void addInputSec(InputSectionBase *IS, StringRef OutsecName);
void addInputSec(InputSectionBase *IS, StringRef OutsecName,
OutputSection *&Sec);
llvm::SmallDenseMap<SectionKey, OutputSection *> Map;
std::vector<OutputSection *> &OutputSections;
uint64_t getHeaderSize();
} // namespace elf
} // namespace lld