OutputSections.h

//===- OutputSections.h -----------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef LLD_ELF_OUTPUT_SECTIONS_H
#defineLLD_ELF_OUTPUT_SECTIONS_H

#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>

namespacelld {
namespaceelf {

structPhdrEntry;
classInputSection;
classInputSectionBase;

// 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.
classOutputSectionfinal : public BaseCommand, public SectionBase {
public:
OutputSection(StringRef Name, uint32_t Type, uint64_t Flags);

staticboolclassof(const SectionBase *S) {
return S->kind() == SectionBase::Output;
 }

staticboolclassof(const BaseCommand *C);

uint64_tgetLMA() const { return PtLoad ? Addr + PtLoad->LMAOffset : Addr; }
template <typename ELFT> voidwriteHeaderTo(typename ELFT::Shdr *SHdr);

uint32_t SectionIndex = UINT32_MAX;
unsigned SortRank;

uint32_tgetPhdrFlags() 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_tSize = 0;

// The following fields correspond to Elf_Shdr members.
uint64_t Offset = 0;
uint64_t Addr = 0;
uint32_t ShName = 0;

voidaddSection(InputSection *IS);

// 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<BaseCommand *> SectionCommands;
 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;

voidfinalize();
template <classELFT> voidwriteTo(uint8_t *Buf);
template <classELFT> voidmaybeCompress();

voidsort(llvm::function_ref<int(InputSectionBase *S)> Order);
voidsortInitFini();
voidsortCtorsDtors();

private:
// Used for implementation of --compress-debug-sections option.
 std::vector<uint8_t> ZDebugHeader;
 llvm::SmallVector<char, 1> CompressedData;

 std::array<uint8_t, 4> getFiller();
};

intgetPriority(StringRef S);

std::vector<InputSection *> getInputSections(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.
structOut {
staticuint8_t *BufferStart;
staticuint8_t First;
static PhdrEntry *TlsPhdr;
static OutputSection *ElfHeader;
static OutputSection *ProgramHeaders;
static OutputSection *PreinitArray;
static OutputSection *InitArray;
static OutputSection *FiniArray;
};

} // namespace elf
} // namespace lld

namespacelld {
namespaceelf {

uint64_tgetHeaderSize();

extern std::vector<OutputSection *> OutputSections;
} // namespace elf
} // namespace lld

#endif