blob: a5b05cf28aa8da57f07d395d069b83f18cabb11b [file] [log] [blame]
//===- OutputSections.h -----------------------------------------*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include "Config.h"
#include "InputSection.h"
#include "LinkerScript.h"
#include "Relocations.h"
#include "lld/Common/LLVM.h"
#include "llvm/MC/StringTableBuilder.h"
#include "llvm/Object/ELF.h"
#include <array>
namespace lld {
namespace elf {
struct PhdrEntry;
class InputSection;
class InputSectionBase;
// 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 SectionCommand, public SectionBase {
OutputSection(StringRef name, uint32_t type, uint64_t flags);
static bool classof(const SectionBase *s) {
return s->kind() == SectionBase::Output;
static bool classof(const SectionCommand *c);
uint64_t getLMA() const { return ptLoad ? addr + ptLoad->lmaOffset : addr; }
template <typename ELFT> void writeHeaderTo(typename ELFT::Shdr *sHdr);
uint32_t sectionIndex = UINT32_MAX;
unsigned sortRank;
uint32_t getPhdrFlags() const;
// Pointer to the PT_LOAD segment, which this section 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, where Off_first and VA_first is file offset and VA of first
// section in PT_LOAD.
PhdrEntry *ptLoad = nullptr;
// Pointer to a relocation section for this section. Usually nullptr because
// we consume relocations, but if --emit-relocs is specified (which is rare),
// it may have a non-null value.
OutputSection *relocationSection = nullptr;
// Initially this field is the number of InputSections that have been added to
// the OutputSection so far. Later on, after a call to assignAddresses, it
// corresponds to the Elf_Shdr member.
uint64_t size = 0;
// The following fields correspond to Elf_Shdr members.
uint64_t offset = 0;
uint64_t addr = 0;
uint32_t shName = 0;
void recordSection(InputSectionBase *isec);
void commitSection(InputSection *isec);
void finalizeInputSections();
// The following members are normally only used in linker scripts.
MemoryRegion *memRegion = nullptr;
MemoryRegion *lmaRegion = nullptr;
Expr addrExpr;
Expr alignExpr;
Expr lmaExpr;
Expr subalignExpr;
std::vector<SectionCommand *> commands;
std::vector<StringRef> phdrs;
llvm::Optional<std::array<uint8_t, 4>> filler;
ConstraintKind constraint = ConstraintKind::NoConstraint;
std::string location;
std::string memoryRegionName;
std::string lmaRegionName;
bool nonAlloc = false;
bool noload = false;
bool expressionsUseSymbols = false;
bool usedInExpression = false;
bool inOverlay = false;
// Tracks whether the section has ever had an input section added to it, even
// if the section was later removed (e.g. because it is a synthetic section
// that wasn't needed). This is needed for orphan placement.
bool hasInputSections = false;
void finalize();
template <class ELFT> void writeTo(uint8_t *buf);
// Check that the addends for dynamic relocations were written correctly.
void checkDynRelAddends(const uint8_t *bufStart);
template <class ELFT> void maybeCompress();
void sort(llvm::function_ref<int(InputSectionBase *s)> order);
void sortInitFini();
void sortCtorsDtors();
// Used for implementation of --compress-debug-sections option.
std::vector<uint8_t> zDebugHeader;
llvm::SmallVector<char, 0> compressedData;
std::array<uint8_t, 4> getFiller();
int getPriority(StringRef s);
InputSection *getFirstInputSection(const OutputSection *os);
std::vector<InputSection *> getInputSections(const OutputSection *os);
// 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 *bufferStart;
static PhdrEntry *tlsPhdr;
static OutputSection *elfHeader;
static OutputSection *programHeaders;
static OutputSection *preinitArray;
static OutputSection *initArray;
static OutputSection *finiArray;
uint64_t getHeaderSize();
extern std::vector<OutputSection *> outputSections;
} // namespace elf
} // namespace lld