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1//===- OutputSection.h ------------------------------------------*- C++ -*-===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9#ifndef LLD_MACHO_OUTPUT_SECTION_H10#define LLD_MACHO_OUTPUT_SECTION_H11 12#include "Symbols.h"13#include "lld/Common/LLVM.h"14#include "llvm/ADT/DenseMap.h"15#include "llvm/ADT/TinyPtrVector.h"16 17#include <limits>18 19namespace lld::macho {20 21class Defined;22class InputSection;23class OutputSegment;24 25// The default order value for OutputSections that are not constructed from26// InputSections (i.e. SyntheticSections). We make it less than INT_MAX in order27// not to conflict with the ordering of zerofill sections, which must always be28// placed at the end of their segment.29constexpr int UnspecifiedInputOrder = std::numeric_limits<int>::max() - 1024;30 31// Output sections represent the finalized sections present within the final32// linked executable. They can represent special sections (like the symbol33// table), or represent coalesced sections from the various inputs given to the34// linker with the same segment / section name.35class OutputSection {36public:37 enum Kind {38 ConcatKind,39 SyntheticKind,40 TextKind,41 };42 43 OutputSection(Kind kind, StringRef name) : name(name), sectionKind(kind) {}44 virtual ~OutputSection() = default;45 Kind kind() const { return sectionKind; }46 47 // These accessors will only be valid after finalizing the section.48 uint64_t getSegmentOffset() const;49 50 // How much space the section occupies in the address space.51 virtual uint64_t getSize() const = 0;52 // How much space the section occupies in the file. Most sections are copied53 // as-is so their file size is the same as their address space size.54 virtual uint64_t getFileSize() const { return getSize(); }55 56 // Hidden sections omit header content, but body content may still be present.57 virtual bool isHidden() const { return false; }58 // Unneeded sections are omitted entirely (header and body).59 virtual bool isNeeded() const { return true; }60 61 // The implementations of this method can assume that it is only called right62 // before addresses get assigned to this particular OutputSection. In63 // particular, this means that it gets called only after addresses have been64 // assigned to output sections that occur earlier in the output binary.65 // Naturally, this means different sections' finalize() methods cannot execute66 // concurrently with each other. As such, avoid using this method for67 // operations that do not require this strict sequential guarantee.68 //69 // Operations that need to occur late in the linking process, but which do not70 // need the sequential guarantee, should be named `finalizeContents()`. See71 // e.g. LinkEditSection::finalizeContents() and72 // CStringSection::finalizeContents().73 virtual void finalize() {}74 75 virtual void writeTo(uint8_t *buf) const = 0;76 77 // Handle section$start$ and section$end$ symbols.78 void assignAddressesToStartEndSymbols();79 80 StringRef name;81 llvm::TinyPtrVector<Defined *> sectionStartSymbols;82 llvm::TinyPtrVector<Defined *> sectionEndSymbols;83 OutputSegment *parent = nullptr;84 // For output sections that don't have explicit ordering requirements, their85 // output order should be based on the order of the input sections they86 // contain.87 int inputOrder = UnspecifiedInputOrder;88 89 uint32_t index = 0;90 uint64_t addr = 0;91 uint64_t fileOff = 0;92 uint32_t align = 1;93 uint32_t flags = 0;94 uint32_t reserved1 = 0;95 uint32_t reserved2 = 0;96 97private:98 Kind sectionKind;99};100 101} // namespace lld::macho102 103#endif104