1 //===- OutputSections.h -----------------------------------------*- C++ -*-===//
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #ifndef LLD_ELF_OUTPUT_SECTIONS_H
11 #define LLD_ELF_OUTPUT_SECTIONS_H
14 #include "InputSection.h"
15 #include "Relocations.h"
17 #include "lld/Core/LLVM.h"
18 #include "llvm/MC/StringTableBuilder.h"
19 #include "llvm/Object/ELF.h"
26 struct EhSectionPiece;
29 class InputSectionBase;
30 class MergeInputSection;
32 template <class ELFT> class ObjectFile;
33 template <class ELFT> class SharedFile;
37 // This represents a section in an output file.
38 // It is composed of multiple InputSections.
39 // The writer creates multiple OutputSections and assign them unique,
40 // non-overlapping file offsets and VAs.
41 class OutputSection final : public SectionBase {
43 OutputSection(StringRef Name, uint32_t Type, uint64_t Flags);
45 static bool classof(const SectionBase *S) {
46 return S->kind() == SectionBase::Output;
49 uint64_t getLMA() const { return Addr + LMAOffset; }
50 template <typename ELFT> void writeHeaderTo(typename ELFT::Shdr *SHdr);
52 unsigned SectionIndex;
55 uint32_t getPhdrFlags() const;
57 void updateAlignment(uint32_t Val) {
62 // Pointer to the first section in PT_LOAD segment, which this section
63 // also resides in. This field is used to correctly compute file offset
64 // of a section. When two sections share the same load segment, difference
65 // between their file offsets should be equal to difference between their
66 // virtual addresses. To compute some section offset we use the following
67 // formula: Off = Off_first + VA - VA_first.
68 OutputSection *FirstInPtLoad = nullptr;
70 // Pointer to a relocation section for this section. Usually nullptr because
71 // we consume relocations, but if --emit-relocs is specified (which is rare),
72 // it may have a non-null value.
73 OutputSection *RelocationSection = nullptr;
75 // The following fields correspond to Elf_Shdr members.
78 uint64_t LMAOffset = 0;
82 void addSection(InputSection *S);
83 void sort(std::function<int(InputSectionBase *S)> Order);
85 void sortCtorsDtors();
87 std::vector<InputSection *> Sections;
89 // Used for implementation of --compress-debug-sections option.
90 std::vector<uint8_t> ZDebugHeader;
91 llvm::SmallVector<char, 1> CompressedData;
93 // Location in the output buffer.
94 uint8_t *Loc = nullptr;
97 // All output sections that are handled by the linker specially are
98 // globally accessible. Writer initializes them, so don't use them
99 // until Writer is initialized.
101 static uint8_t First;
102 static OutputSection *Opd;
103 static uint8_t *OpdBuf;
104 static PhdrEntry *TlsPhdr;
105 static OutputSection *DebugInfo;
106 static OutputSection *ElfHeader;
107 static OutputSection *ProgramHeaders;
108 static OutputSection *PreinitArray;
109 static OutputSection *InitArray;
110 static OutputSection *FiniArray;
121 template <> struct DenseMapInfo<lld::elf::SectionKey> {
122 static lld::elf::SectionKey getEmptyKey();
123 static lld::elf::SectionKey getTombstoneKey();
124 static unsigned getHashValue(const lld::elf::SectionKey &Val);
125 static bool isEqual(const lld::elf::SectionKey &LHS,
126 const lld::elf::SectionKey &RHS);
132 // This class knows how to create an output section for a given
133 // input section. Output section type is determined by various
134 // factors, including input section's sh_flags, sh_type and
136 class OutputSectionFactory {
138 OutputSectionFactory(std::vector<OutputSection *> &OutputSections);
139 ~OutputSectionFactory();
141 void addInputSec(InputSectionBase *IS, StringRef OutsecName);
142 void addInputSec(InputSectionBase *IS, StringRef OutsecName,
143 OutputSection *&Sec);
146 llvm::SmallDenseMap<SectionKey, OutputSection *> Map;
147 std::vector<OutputSection *> &OutputSections;
150 uint64_t getHeaderSize();
151 void reportDiscarded(InputSectionBase *IS);
153 extern std::vector<OutputSection *> OutputSections;
154 extern std::vector<OutputSectionCommand *> OutputSectionCommands;