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;
54 uint32_t getPhdrFlags() const;
56 void updateAlignment(uint32_t Val) {
61 // If true, this section will be page aligned on disk.
62 // Typically the first section of each PT_LOAD segment has this flag.
63 bool PageAlign = false;
65 // Pointer to the first section in PT_LOAD segment, which this section
66 // also resides in. This field is used to correctly compute file offset
67 // of a section. When two sections share the same load segment, difference
68 // between their file offsets should be equal to difference between their
69 // virtual addresses. To compute some section offset we use the following
70 // formula: Off = Off_first + VA - VA_first.
71 OutputSection *FirstInPtLoad = nullptr;
73 // The following fields correspond to Elf_Shdr members.
76 uint64_t LMAOffset = 0;
80 void addSection(InputSection *S);
81 void sort(std::function<int(InputSectionBase *S)> Order);
83 void sortCtorsDtors();
85 template <class ELFT> void writeTo(uint8_t *Buf);
86 template <class ELFT> void finalize();
87 template <class ELFT> void maybeCompress();
89 std::vector<InputSection *> Sections;
91 // Used for implementation of --compress-debug-sections option.
92 std::vector<uint8_t> ZDebugHeader;
93 llvm::SmallVector<char, 1> CompressedData;
95 // Location in the output buffer.
96 uint8_t *Loc = nullptr;
99 // All output sections that are handled by the linker specially are
100 // globally accessible. Writer initializes them, so don't use them
101 // until Writer is initialized.
103 static uint8_t First;
104 static OutputSection *Opd;
105 static uint8_t *OpdBuf;
106 static PhdrEntry *TlsPhdr;
107 static OutputSection *DebugInfo;
108 static OutputSection *ElfHeader;
109 static OutputSection *ProgramHeaders;
110 static OutputSection *PreinitArray;
111 static OutputSection *InitArray;
112 static OutputSection *FiniArray;
123 template <> struct DenseMapInfo<lld::elf::SectionKey> {
124 static lld::elf::SectionKey getEmptyKey();
125 static lld::elf::SectionKey getTombstoneKey();
126 static unsigned getHashValue(const lld::elf::SectionKey &Val);
127 static bool isEqual(const lld::elf::SectionKey &LHS,
128 const lld::elf::SectionKey &RHS);
134 // This class knows how to create an output section for a given
135 // input section. Output section type is determined by various
136 // factors, including input section's sh_flags, sh_type and
138 class OutputSectionFactory {
140 OutputSectionFactory(std::vector<OutputSection *> &OutputSections);
141 ~OutputSectionFactory();
143 void addInputSec(InputSectionBase *IS, StringRef OutsecName);
144 void addInputSec(InputSectionBase *IS, StringRef OutsecName,
145 OutputSection *&Sec);
148 llvm::SmallDenseMap<SectionKey, OutputSection *> Map;
149 std::vector<OutputSection *> &OutputSections;
152 uint64_t getHeaderSize();