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1 //===- OutputSection.h ------------------------------------------*- C++ -*-===//
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2 //
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3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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4 // See https://llvm.org/LICENSE.txt for license information.
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5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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6 //
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7 //===----------------------------------------------------------------------===//
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8
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9 #ifndef LLD_MACHO_OUTPUT_SECTION_H
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10 #define LLD_MACHO_OUTPUT_SECTION_H
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11
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12 #include "lld/Common/LLVM.h"
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13 #include "llvm/ADT/DenseMap.h"
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14
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221
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15 #include <limits>
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16
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17 namespace lld {
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18 namespace macho {
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19
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20 class InputSection;
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21 class OutputSegment;
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22
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23 // The default order value for OutputSections that are not constructed from
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24 // InputSections (i.e. SyntheticSections). We make it less than INT_MAX in order
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25 // not to conflict with the ordering of zerofill sections, which must always be
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26 // placed at the end of their segment.
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27 constexpr int UnspecifiedInputOrder = std::numeric_limits<int>::max() - 1024;
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28
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29 // Output sections represent the finalized sections present within the final
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30 // linked executable. They can represent special sections (like the symbol
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31 // table), or represent coalesced sections from the various inputs given to the
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32 // linker with the same segment / section name.
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33 class OutputSection {
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34 public:
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35 enum Kind {
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36 ConcatKind,
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37 SyntheticKind,
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38 };
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39
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40 OutputSection(Kind kind, StringRef name) : name(name), sectionKind(kind) {}
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41 virtual ~OutputSection() = default;
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42 Kind kind() const { return sectionKind; }
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43
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44 // These accessors will only be valid after finalizing the section.
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45 uint64_t getSegmentOffset() const;
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46
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47 // How much space the section occupies in the address space.
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48 virtual uint64_t getSize() const = 0;
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49 // How much space the section occupies in the file. Most sections are copied
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50 // as-is so their file size is the same as their address space size.
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51 virtual uint64_t getFileSize() const { return getSize(); }
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52
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53 // Hidden sections omit header content, but body content may still be present.
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54 virtual bool isHidden() const { return false; }
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55 // Unneeded sections are omitted entirely (header and body).
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56 virtual bool isNeeded() const { return true; }
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57
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58 virtual void finalize() {
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59 // TODO investigate refactoring synthetic section finalization logic into
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60 // overrides of this function.
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61 }
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62
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63 virtual void writeTo(uint8_t *buf) const = 0;
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64
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65 StringRef name;
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66 OutputSegment *parent = nullptr;
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67 // For output sections that don't have explicit ordering requirements, their
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68 // output order should be based on the order of the input sections they
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69 // contain.
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70 int inputOrder = UnspecifiedInputOrder;
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71
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72 uint32_t index = 0;
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73 uint64_t addr = 0;
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74 uint64_t fileOff = 0;
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75 uint32_t align = 1;
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76 uint32_t flags = 0;
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77 uint32_t reserved1 = 0;
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78 uint32_t reserved2 = 0;
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79
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80 private:
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81 Kind sectionKind;
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82 };
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83
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84 } // namespace macho
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85 } // namespace lld
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86
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87 #endif
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